@article{anyah_xia_semazzi_2022, title={Influence of water table dynamics on spatial and temporal patterns of hydroclimate extremes over Lake Victoria Basin, East Africa: Comparison of wet and dry years}, ISSN={["1097-0088"]}, DOI={10.1002/joc.7682}, abstractNote={Abstract}, journal={INTERNATIONAL JOURNAL OF CLIMATOLOGY}, author={Anyah, Richard and Xia, Sun and Semazzi, Fredrick}, year={2022}, month={May} }
 @article{evans_rowell_semazzi_2020, title={The future-climate, current-policy framework: towards an approach linking climate science to sector policy development}, volume={15}, ISSN={["1748-9326"]}, DOI={10.1088/1748-9326/abbeb9}, abstractNote={Abstract}, number={11}, journal={ENVIRONMENTAL RESEARCH LETTERS}, author={Evans, Barbara E. and Rowell, David P. and Semazzi, Frederick H. M.}, year={2020}, month={Nov} }
 @article{kiwanuka-tondo_semazzi_pettiway_2019, title={Climate risk communication of navigation safety and climate conditions over Lake Victoria basin: Exploring perceptions and knowledge of indigenous communities}, volume={5}, ISSN={2331-1886}, url={http://dx.doi.org/10.1080/23311886.2019.1588485}, DOI={10.1080/23311886.2019.1588485}, abstractNote={Abstract Governmental and non-governmental organizations have increasingly developed climate services and products to improve safety on Lake Victoria, Africa’s largest and the world’s second largest freshwater lake. Despite these efforts and other interests in efficient exploitation of natural resources, Lake Victoria is one of the most dangerous waterways in the world. Each year, around 5,000 people lose their lives on the lake due to navigation accidents. The purpose of this study is to analyze the perceptions of the stakeholders about climate change, meteorological services, causes of accidents, and cultural, social, and economic barriers that lead to lack of safety of navigation on Lake Victoria. The study uses anecdotal interviews with a convenience sample of five participants and surveys research with a convenience sample of 316 respondents from Burundi, Kenya, Rwanda, Tanzania, and Uganda. The study makes a significant contribution to the understanding of the multilayered ecological, socioeconomic, environmental, technological, and health-related factors that influence the safety of navigation on the lake by harnessing the indigenous knowledge of the stakeholders about their concerns and experiences. The authors assert and reaffirm the importance of integrating indigenous and scientific climate knowledge, offering strategies to enhance climate services and make technological products culturally relevant.}, number={1}, journal={Cogent Social Sciences}, publisher={Informa UK Limited}, author={Kiwanuka-Tondo, James and Semazzi, Fredrick and Pettiway, Keon}, editor={Ricart Casadevall, SandraEditor}, year={2019}, month={Mar} }
 @article{gudoshava_semazzi_2019, title={Customization and Validation of a Regional Climate Model Using Satellite Data Over East Africa}, volume={10}, ISSN={["2073-4433"]}, DOI={10.3390/atmos10060317}, abstractNote={This study focused on the customization of the fourth generation International Center for Theoretical Physics Regional Climate Model version 4.4 and its ability to reproduce the mean climate and most dominant modes of variability over East Africa. The simulations were performed at a spatial resolution of 25 km for the period 1998–2013. The model was driven by ERA-Interim reanalysis. The customization focus was on cumulus and microphysics schemes during the Short Rains for the year 2000. The best physics combinations were then utilized for the validation studies. The East Africa region and Lake Victoria Basin region are adapted to carry out empirical orthogonal function analysis, during the Short and Long Rains. Tropical Rainfall Measuring Mission data was utilized in the validation of the model. The first mode of variability from the model and observational data during the Short Rains was associated with the warming of the Pacific Ocean and the sea surface temperature gradients over the Indian Ocean. During the Long rains, the inter-annual rainfall variability over the Lake Victoria region was associated with the sea surface temperature anomaly over the Indian Ocean and for the East Africa region the associations were weak. The drivers during the Long Rains over East Africa region were then further investigated by splitting the season to the March–April and May periods. The March–April period was positively correlated to the West Pacific and Indian Ocean dipole index, while May was associated with the Quasi-Biennial Oscillation. In conclusion, although the model can reproduce the dominant modes of variability as in the observational data sets during the Short Rains, skill was lower during the Long Rains.}, number={6}, journal={ATMOSPHERE}, author={Gudoshava, Masilin and Semazzi, Fredrick H. M.}, year={2019}, month={Jun} }
 @article{wootten_terando_reich_boyles_semazzi_2017, title={Characterizing Sources of Uncertainty from Global Climate Models and Downscaling Techniques}, volume={56}, ISSN={["1558-8432"]}, DOI={10.1175/jamc-d-17-0087.1}, abstractNote={Abstract}, number={12}, journal={JOURNAL OF APPLIED METEOROLOGY AND CLIMATOLOGY}, author={Wootten, A. and Terando, A. and Reich, B. J. and Boyles, R. P. and Semazzi, F.}, year={2017}, month={Dec}, pages={3245–3262} }
 @article{tetteh_appiah-badu_semazzi_olayide_2017, title={Deriving Useful Information from Bimonthly Global-Scale Climate Analysis for Climate Change Adaptation Over East Africa}, ISBN={["978-3-319-49519-4"]}, ISSN={["1610-2010"]}, DOI={10.1007/978-3-319-49520-0_8}, abstractNote={Implementation of appropriate climate change adaptation strategies is contingent on a good understanding of climate variability. Efforts to adapt to climate change impacts in East African societies have flourished. However, an area of research which has been neglected and could enhance adaptive capacity is bimonthly global-scale climate analysis in relationship to the long rains, during the climatologically prominent phase of El Niño Southern Oscillation (ENSO). Empirical analyses were carried out using nearly 60 years of standardized gridded rainfall, horizontal wind and sea surface temperature (SST) data, to gain predictive understanding of the region’s climate. This study has delineated SST and divergent circulation features related to three of the four rainfall modes. The modes responded differently to the Pacific ENSO, Atlantic and Indian Oceans. However, there was no clear relationship between the second mode and the global SST distributions. Having substantiated this with monthly and seasonal-scale SST analyses, it suggested that this atypical pattern warranted numerical modeling studies or should be verified using other high resolution datasets. The SST predictor features identified may be used to enhance operational seasonal climate prediction scheme. In this way, end users would be better prepared to select appropriate climate change adaption options.}, journal={CLIMATE CHANGE ADAPTATION IN AFRICA: FOSTERING RESILIENCE AND CAPACITY TO ADAPT}, author={Tetteh, Isaac K. and Appiah-Badu, Nana K. A. and Semazzi, Fredrick H. M. and Olayide, Olawale E.}, year={2017}, pages={125–140} }
 @article{thiery_gudmundsson_bedka_semazzi_lhermitte_willems_lipzig_seneviratne_2017, title={Early warnings of hazardous thunderstorms over Lake Victoria}, volume={12}, ISSN={["1748-9326"]}, DOI={10.1088/1748-9326/aa7521}, abstractNote={Weather extremes have harmful impacts on communities around Lake Victoria in East Africa. Every year, intense nighttime thunderstorms cause numerous boating accidents on the lake, resulting in thousands of deaths among fishermen. Operational storm warning systems are therefore crucial. Here we complement ongoing early warning efforts based on numerical weather prediction, by presenting a new satellite data-driven storm prediction system, the prototype Lake Victoria Intense storm Early Warning System (VIEWS). VIEWS derives predictability from the correlation between afternoon land storm activity and nighttime storm intensity on Lake Victoria, and relies on logistic regression techniques to forecast extreme thunderstorms from satellite observations. Evaluation of the statistical model reveals that predictive power is high and independent of the type of input dataset. We then optimise the configuration and show that false alarms also contain valuable information. Our results suggest that regression-based models that are motivated through process understanding have the potential to reduce the vulnerability of local fishing communities around Lake Victoria. The experimental prediction system is publicly available under the MIT licence at http://github.com/wthiery/VIEWS.}, number={7}, journal={ENVIRONMENTAL RESEARCH LETTERS}, author={Thiery, Wim and Gudmundsson, Lukas and Bedka, Kristopher and Semazzi, Fredrick H. M. and Lhermitte, Stef and Willems, Patrick and Lipzig, Nicole P. M. and Seneviratne, Sonia I.}, year={2017}, month={Jul} }
 @inbook{chaudhary_gonzalez_bello_angus_desai_harenberg_doraiswamy_semazzi_kumar_samatova_2016, title={Causality-Guided Feature Selection}, ISBN={9783319495859 9783319495866}, ISSN={0302-9743 1611-3349}, url={http://dx.doi.org/10.1007/978-3-319-49586-6_26}, DOI={10.1007/978-3-319-49586-6_26}, abstractNote={Identifying meaningful features that drive a phenomenon (response) of interest in complex systems of interconnected factors is a challenging problem. Causal discovery methods have been previously applied to estimate bounds on causal strengths of factors on a response or to identify meaningful interactions between factors in complex systems, but these approaches have been used only for inferential purposes. In contrast, we posit that interactions between factors with a potential causal association on a given response could be viable candidates not only for hypothesis generation but also for predictive modeling. In this work, we propose a causality-guided feature selection methodology that identifies factors having a potential cause-effect relationship in complex systems, and selects features by clustering them based on their causal strength with respect to the response. To this end, we estimate statistically significant causal effects on the response of factors taking part in potential causal relationships, while addressing associated technical challenges, such as multicollinearity in the data. We validate the proposed methodology for predicting response in five real-world datasets from the domain of climate science and biology. The selected features show predictive skill and consistent performance across different domains.}, booktitle={Advanced Data Mining and Applications}, publisher={Springer International Publishing}, author={Chaudhary, Mandar S. and Gonzalez, Doel L. and Bello, Gonzalo A. and Angus, Michael P. and Desai, Dhara and Harenberg, Steve and Doraiswamy, P. Murali and Semazzi, Fredrick H. M. and Kumar, Vipin and Samatova, Nagiza F.}, year={2016}, pages={391–405} }
 @article{sun_xie_semazzi_liu_2015, title={Effect of Lake Surface Temperature on the Spatial Distribution and Intensity of the Precipitation over the Lake Victoria Basin}, volume={143}, ISSN={["1520-0493"]}, DOI={10.1175/mwr-d-14-00049.1}, abstractNote={Abstract}, number={4}, journal={MONTHLY WEATHER REVIEW}, author={Sun, Xia and Xie, Lian and Semazzi, Fredrick and Liu, Bin}, year={2015}, month={Apr}, pages={1179–1192} }
 @article{gonzalez_angus_tetteh_bello_padmanabhan_pendse_srinivas_yu_semazzi_kumar_et al._2015, title={On the data-driven inference of modulatory networks in climate science: an application to West African rainfall}, volume={22}, ISSN={["1607-7946"]}, DOI={10.5194/npg-22-33-2015}, abstractNote={Abstract. Decades of hypothesis-driven and/or first-principles research have been applied towards the discovery and explanation of the mechanisms that drive climate phenomena, such as western African Sahel summer rainfall~variability. Although connections between various climate factors have been theorized, not all of the key relationships are fully understood. We propose a data-driven approach to identify candidate players in this climate system, which can help explain underlying mechanisms and/or even suggest new relationships, to facilitate building a more comprehensive and predictive model of the modulatory relationships influencing a climate phenomenon of interest. We applied coupled heterogeneous association rule mining (CHARM), Lasso multivariate regression, and dynamic Bayesian networks to find relationships within a complex system, and explored means with which to obtain a consensus result from the application of such varied methodologies. Using this fusion of approaches, we identified relationships among climate factors that modulate Sahel rainfall. These relationships fall into two categories: well-known associations from prior climate knowledge, such as the relationship with the El Niño–Southern Oscillation (ENSO) and putative links, such as North Atlantic Oscillation, that invite further research.
                    }, number={1}, journal={NONLINEAR PROCESSES IN GEOPHYSICS}, author={Gonzalez, D. L., II and Angus, M. P. and Tetteh, I. K. and Bello, G. A. and Padmanabhan, K. and Pendse, S. V. and Srinivas, S. and Yu, J. and Semazzi, F. and Kumar, V. and et al.}, year={2015}, pages={33–46} }
 @article{xie_semazzi_hanna_anyah_gao_he_2015, title={Regional Climate Change: Downscaling, Prediction, and Impact Assessment}, volume={2015}, ISSN={["1687-9317"]}, DOI={10.1155/2015/290281}, abstractNote={Although the issue of climate change is often dealt with in global perspective, the impact of climate change must be assessed at regional scales. While global climate models can provide projections of the average state of large-scale circulation of future climate, the downscaling of such projections to regional scale with improved spatial and temporal resolution for both the forcing fields and the climatic responses is the basis for assessing the societal impacts of climate change. Therefore, it is important to not only study climate change at the global scale but also study the regional manifestations of the climate system at spatial scales ranging from less than a hundred kilometers to thousands of kilometers with time scales from months to years to decades. This special issue publishes a collection of articles covering a wide range of topics of our understanding of “regional climate” from downscaling the variability of extreme rainfall over the Yangtze River basin (T. Gao and L. Xie) and assessing the water resources in the Yellow River region (Z. Wu et al.) in China to forecasting the precipitation and water resources in the Lake Victoria region in East Africa (X. Sun et al., R. Argent et al., and K. A. Smith and F. H. M. Semazzi), from downscaling wind energy resources in the contiguous United States (B. Liu et al.) to characterizing the precipitation extremes in the Carpathian region in central and southern Europe (L. Gaal et al.), and from analyzing the energy balance in semiarid grasslands in China (Q. Jiang et al.) to detecting future climate change signals in central and eastern Europe from numerical model simulations (M. Belda et al.). This special issue also includes articles addressing the impacts of regional climate change on tropical cyclones over the Atlantic Ocean (K. Xie and B. Liu), on crop yields in North China (H. Liu et al.), and on litter production and nutrient dynamics in a plantation in China (X. Ge et al.), as well as rainfall and drought in Eastern Kenya (M. O. Kisaka et al.). Additionally, several articles with focus on regional climate downscaling methodologies are also included. S. Kim et al. studied the effects of geographic features in a mountainous area on the downscaling of global climate model data; T. R. Lee et al. demonstrated the feasibility of using PRISM (parameterelevation regression on independent slope model) to downscale maximum temperature to subkilometer scale; L. Gao et al. applied the LASSO algorithm to statistically downscale the ERA-interim precipitation forecast over complex terrain; and K.-H. Min and W.-Y. Sun explored the application of an atmosphere-cryosphere coupledmodel in regional climate applications. These articles reflect the recent advances and applications in “regional climate downscaling, prediction, and impact assessment” from a set of unique angles. We hope they are of interest to peers.}, journal={ADVANCES IN METEOROLOGY}, author={Xie, Lian and Semazzi, Fredrick and Hanna, Adel and Anyah, Richard and Gao, Huiwang and He, Yijun}, year={2015} }
 @inbook{bello_angus_pedemane_harlalka_semazzi_kumar_samatova_2015, title={Response-Guided Community Detection: Application to Climate Index Discovery}, ISBN={9783319235240 9783319235257}, ISSN={0302-9743 1611-3349}, url={http://dx.doi.org/10.1007/978-3-319-23525-7_45}, DOI={10.1007/978-3-319-23525-7_45}, abstractNote={Discovering climate indices–time series that summarize spatiotemporal climate patterns–is a key task in the climate science domain. In this work, we approach this task as a problem of response-guided community detection; that is, identifying communities in a graph associated with a response variable of interest. To this end, we propose a general strategy for response-guided community detection that explicitly incorporates information of the response variable during the community detection process, and introduce a graph representation of spatiotemporal data that leverages information from multiple variables. We apply our proposed methodology to the discovery of climate indices associated with seasonal rainfall variability. Our results suggest that our methodology is able to capture the underlying patterns known to be associated with the response variable of interest and to improve its predictability compared to existing methodologies for data-driven climate index discovery and official forecasts.}, booktitle={Machine Learning and Knowledge Discovery in Databases}, publisher={Springer International Publishing}, author={Bello, Gonzalo A. and Angus, Michael and Pedemane, Navya and Harlalka, Jitendra K. and Semazzi, Fredrick H. M. and Kumar, Vipin and Samatova, Nagiza F.}, year={2015}, pages={736–751} }
 @article{argent_sun_semazzi_xie_liu_2015, title={The Development of a Customization Framework for the WRF Model over the Lake Victoria Basin, Eastern Africa on Seasonal Timescales}, volume={2015}, ISSN={["1687-9317"]}, DOI={10.1155/2015/653473}, abstractNote={Lake Victoria, Africa, supports millions of people. To produce reliable climate projections, it is desirable to successfully model the rainfall over the lake accurately. An initial step is taken here with customization of the Weather, Research, and Forecast (WRF) model. Of particular interest is an asymmetrical rainfall pattern across the lake basin, due to a diurnal land-lake breeze. The main aim is to present a customization framework for use over the lake. This framework is developed by conducting several series of model runs to investigate aspects of the customization. The runs are analyzed using Tropical Rainfall Measuring Mission rainfall data and Climatic Research Unit temperature data. The study shows that the choice of parameters and lake surface temperature initialization can significantly alter the results. Also, the optimal physics combinations for the climatology may not necessarily be suitable for all circumstances, such as extreme years. The study concludes that WRF is unable to reproduce the pattern across the lake. The temperature of the lake is too cold and this prevents the diurnal land-lake breeze reversal. Overall, this study highlights the importance of customizing a model to the region of research and presents a framework through which this may be achieved.}, journal={ADVANCES IN METEOROLOGY}, author={Argent, R. and Sun, X. and Semazzi, F. and Xie, L. and Liu, B.}, year={2015} }
 @article{pandya_hodgson_hayden_akweongo_hopson_forgor_yoksas_dalaba_dukic_mera_et al._2015, title={Using Weather Forecasts to Help Manage Meningitis in the West African Sahel}, volume={96}, ISSN={0003-0007 1520-0477}, url={http://dx.doi.org/10.1175/bams-d-13-00121.1}, DOI={10.1175/bams-d-13-00121.1}, abstractNote={Abstract}, number={1}, journal={Bulletin of the American Meteorological Society}, publisher={American Meteorological Society}, author={Pandya, Rajul and Hodgson, Abraham and Hayden, Mary H. and Akweongo, Patricia and Hopson, Thomas and Forgor, Abudulai Adams and Yoksas, Tom and Dalaba, Maxwell Ayindenaba and Dukic, Vanja and Mera, Roberto and et al.}, year={2015}, month={Jan}, pages={103–115} }
 @article{sun_xie_semazzi_liu_2014, title={A Numerical Investigation of the Precipitation over Lake Victoria Basin Using a Coupled Atmosphere-Lake Limited-Area Model}, volume={2014}, ISSN={["1687-9317"]}, DOI={10.1155/2014/960924}, abstractNote={By using a coupled atmosphere-lake model, which consists of the Weather Research and Forecasting (WRF) model and the Princeton Ocean Model (POM), the present study generated realistic lake surface temperature (LST) over Lake Victoria and revealed the prime importance of LST on the precipitation pattern over the Lake Victoria Basin (LVB). A suite of sensitivity experiments was conducted for the selection of an optimal combination of physics options including cumulus, microphysics, and planetary boundary layer schemes for simulating precipitation over the LVB. The WRF-POM coupled system made a great performance on simulating the expected LST, which is featured with eastward temperature gradient as in the real bathymetry of the lake. Under thorough examination of diagnostic analysis, a distinguished diurnal phenomenon has been unveiled. The precipitation mainly occurs during the nocturnal peak between midnight and early in the morning, which is associated with the strong land breeze circulation, when the lake temperature is warmer than the adjacent land. Further exploration of vertical velocity, surface divergence pattern, and maximum radar reflectivity confirms such conjecture. The time-longitude analysis of maximum radar reflectivity over the entire lake also shows a noticeable pattern of dominating westward propagation.}, journal={ADVANCES IN METEOROLOGY}, publisher={Hindawi Publishing Corporation}, author={Sun, Xia and Xie, Lian and Semazzi, Fredrick H. M. and Liu, Bin}, year={2014} }
 @article{liess_kumar_snyder_kawale_steinhaeuser_semazzi_ganguly_samatova_kumar_2014, title={Different Modes of Variability over the Tasman Sea: Implications for Regional Climate}, volume={27}, ISSN={["1520-0442"]}, DOI={10.1175/jcli-d-13-00713.1}, abstractNote={Abstract}, number={22}, journal={JOURNAL OF CLIMATE}, author={Liess, Stefan and Kumar, Arjun and Snyder, Peter K. and Kawale, Jaya and Steinhaeuser, Karsten and Semazzi, Frederick H. M. and Ganguly, Auroop R. and Samatova, Nagiza F. and Kumar, Vipin}, year={2014}, month={Nov}, pages={8466–8486} }
 @article{liu_costa_xie_semazzi_2014, title={Dynamical downscaling of climate change impacts on wind energy resources in the contiguous United States by using a limited-area model with scale-selective data assimilation}, DOI={10.1155/2014/897246}, abstractNote={By using a limited-area model (LAM) in combination with the scale-selective data assimilation (SSDA) approach, wind energy resources in the contiguous United States (CONUS) were downscaled from IPCC CCSM3 global model projections for both current and future climate conditions. An assessment of climate change impacts on wind energy resources in the CONUS region was then conducted. Based on the downscaling results, when projecting into future climate under IPCC’s A1B scenario, the average annual wind speed experiences an overall shift across the CONUS region. From the current climate to the 2040s, the average annual wind speed is expected to increase from 0.1 to 0.2 m s−1over the Great Plains, Northern Great Lakes Region, and Southwestern United States located southwest of the Rocky Mountains. When projecting into the 2090s from current climate, there is an overall increase in the Great Plains Region and Southwestern United States located southwest of the Rockies with a mean wind speed increase between 0 and 0.1 m s−1, while, the Northern Great Lakes Region experiences an even greater increase from current climate to 2090s than over the first few decades with an increase of mean wind speed from 0.1 to 0.4 m s−1.}, journal={Advances in Meteorology}, author={Liu, B. and Costa, K. B. and Xie, L. and Semazzi, F. H. M.}, year={2014} }
 @article{mera_laing_semazzi_2014, title={Moisture Variability and Multiscale Interactions during Spring in West Africa}, volume={142}, ISSN={0027-0644 1520-0493}, url={http://dx.doi.org/10.1175/mwr-d-13-00175.1}, DOI={10.1175/mwr-d-13-00175.1}, abstractNote={Abstract}, number={9}, journal={Monthly Weather Review}, publisher={American Meteorological Society}, author={Mera, Roberto and Laing, Arlene G. and Semazzi, Frederick}, year={2014}, month={Sep}, pages={3178–3198} }
 @article{smith_semazzi_2014, title={The Role of the Dominant Modes of Precipitation Variability over Eastern Africa in Modulating the Hydrology of Lake Victoria}, volume={2014}, ISSN={["1687-9317"]}, DOI={10.1155/2014/516762}, abstractNote={Previous water budget studies over Lake Victoria basin have shown that there is near balance between rainfall and evaporation and that the variability of Lake Victoria levels is determined virtually entirely by changes in rainfall since evaporation is nearly constant. The variability of rainfall over East Africa is dominated by El Niño-Southern Oscillation (ENSO); however, the second and third most dominant rainfall climate modes also account for significant variability across the region. The relationship between ENSO and other significant modes of precipitation variability with Lake Victoria levels is nonlinear. This relationship should be studied to determine which modes need to be accurately modeled in order to accurately model Lake Victoria levels, which are important to the hydroelectric industry in East Africa. The objective of this analysis is to estimate the relative contributions of the dominant modes of annual precipitation variability to the modulation of Lake Victoria levels for the present day (1950–2012). The first mode of annual rainfall variability accounts for most of the variability in Lake Victoria levels, while the effects of the second and third modes are negligible even though these modes are also significant over the region.}, journal={ADVANCES IN METEOROLOGY}, author={Smith, Kara A. and Semazzi, Fredrick H. M.}, year={2014} }
 @article{kawale_liess_kumar_steinbach_snyder_kumar_ganguly_samatova_semazzi_2013, title={A graph-based approach to find teleconnections in climate data}, volume={6}, ISSN={1932-1864}, url={http://dx.doi.org/10.1002/SAM.11181}, DOI={10.1002/SAM.11181}, abstractNote={Abstract}, number={3}, journal={Statistical Analysis and Data Mining}, publisher={Wiley}, author={Kawale, Jaya and Liess, Stefan and Kumar, Arjun and Steinbach, Michael and Snyder, Peter and Kumar, Vipin and Ganguly, Auroop R. and Samatova, Nagiza F. and Semazzi, Fredrick}, year={2013}, month={Apr}, pages={158–179} }
 @article{gonzalez_pendse_padmanabhan_angus_tetteh_srinivas_villanes_semazzi_kumar_samatova_2013, title={Coupled Heterogeneous Association Rule Mining (CHARM): Application toward Inference of Modulatory Climate Relationships}, ISSN={["1550-4786"]}, DOI={10.1109/icdm.2013.142}, abstractNote={The complex dynamic climate system often exhibits hierarchical modularity of its organization and function. Scientists have spent decades trying to discover and understand the driving mechanisms behind western African Sahel summer rainfall variability, mostly via hypothesis-driven and/or first-principles based research. Their work has furthered theory regarding the connections between various climate patterns, but the key relationships are still not fully understood. We present Coupled Heterogeneous Association Rule Mining (CHARM), a computationally efficient methodology that mines higher-order relationships between these subsystems' anomalous temporal phases with respect to their effect on the system's response. We apply this to climate science data, aiming to infer putative pathways/cascades of modulating events and the modulating signs that collectively define the network of pathways for the rainfall anomaly in the Sahel. Experimental results are consistent with fundamental theories of phenomena in climate science, especially physical processes that best describe sub-regional climate.}, journal={2013 IEEE 13TH INTERNATIONAL CONFERENCE ON DATA MINING (ICDM)}, author={Gonzalez, Doel L., II and Pendse, Saurabh V. and Padmanabhan, Kanchana and Angus, Michael P. and Tetteh, Isaac K. and Srinivas, Shashank and Villanes, Andrea and Semazzi, Fredrick and Kumar, Vipin and Samatova, Nagiza F.}, year={2013}, pages={1055–1060} }
 @article{chen_hendrix_guan_tetteh_choudhary_semazzi_samatova_2013, title={Discovery of extreme events-related communities in contrasting groups of physical system networks}, volume={27}, ISSN={["1573-756X"]}, DOI={10.1007/s10618-012-0289-3}, abstractNote={The latent behavior of a physical system that can exhibit extreme events such as hurricanes or rainfalls, is complex. Recently, a very promising means for studying complex systems has emerged through the concept of complex networks. Networks representing relationships between individual objects usually exhibit community dynamics. Conventional community detection methods mainly focus on either mining frequent subgraphs in a network or detecting stable communities in time-varying networks. In this paper, we formulate a novel problem—detection of predictive and phase-biased communities in contrasting groups of networks, and propose an efficient and effective machine learning solution for finding such anomalous communities. We build different groups of networks corresponding to different system's phases, such as higher or low hurricane activity, discover phase-related system components as seeds to help bound the search space of community generation in each network, and use the proposed contrast-based technique to identify the changing communities across different groups. The detected anomalous communities are hypothesized (1) to play an important role in defining the target system's state(s) and (2) to improve the predictive skill of the system's states when used collectively in the ensemble of predictive models. When tested on the two important extreme event problems—identification of tropical cyclone-related and of African Sahel rainfall-related climate indices—our algorithm demonstrated the superior performance in terms of various skill and robustness metrics, including 8–16 % accuracy increase, as well as physical interpretability of detected communities. The experimental results also show the efficiency of our algorithm on synthetic datasets.}, number={2}, journal={DATA MINING AND KNOWLEDGE DISCOVERY}, author={Chen, Zhengzhang and Hendrix, William and Guan, Hang and Tetteh, Isaac K. and Choudhary, Alok and Semazzi, Fredrick and Samatova, Nagiza F.}, year={2013}, month={Sep}, pages={225–258} }
 @article{gonzalez_chen_tetteh_pansombut_semazzi_kumar_melechko_samatova_2012, title={Hierarchical Classifier-Regression Ensemble for Multi-Phase Non-Linear Dynamic System Response Prediction: Application to Climate Analysis}, ISBN={["978-1-4673-5164-5"]}, ISSN={["2375-9232"]}, DOI={10.1109/icdmw.2012.133}, abstractNote={A dynamic physical system often undergoes phase transitions in response to fluctuations induced on system parameters. For example, hurricane activity is the climate system's response initiated by a liquid-vapor phase transition associated with non-linearly coupled fluctuations in the ocean and the atmosphere. Because our quantitative knowledge about highly non-linear dynamic systems is very meager, scientists often resort to linear regression techniques such as Least Absolute Deviation (LAD) to learn the non-linear system's response (e.g., hurricane activity) from observed or simulated system's parameters (e.g., temperature, precipitable water, pressure). While insightful, such models still offer limited predictability, and alternatives intended to capture non-linear behaviors such as Stepwise Regression are often controversial in nature. In this paper, we hypothesize that one of the primary reasons for lack of predictability is the treatment of an inherently multi-phase system as being phase less. To bridge this gap, we propose a hybrid approach that first predicts the phase the system is in, and then estimates the magnitude of the system's response using the regression model optimized for this phase. Our approach is designed for systems that could be characterized by multi-variate spatio-temporal data from observations, simulations, or both.}, journal={12TH IEEE INTERNATIONAL CONFERENCE ON DATA MINING WORKSHOPS (ICDMW 2012)}, author={Gonzalez, Doel L., II and Chen, Zhengzhang and Tetteh, Isaac K. and Pansombut, Tatdow and Semazzi, Fredrick and Kumar, Vipin and Melechko, Anatoli and Samatova, Nagiza F.}, year={2012}, pages={781–788} }
 @article{norman_nair_semazzi_2011, title={A low communication and large time step explicit finite-volume solver for non-hydrostatic atmospheric dynamics}, volume={230}, ISSN={["1090-2716"]}, DOI={10.1016/j.jcp.2010.11.022}, abstractNote={An explicit finite-volume solver is proposed for numerical simulation of non-hydrostatic atmospheric dynamics with promise for efficiency on massively parallel machines via low communication needs and large time steps. Solving the governing equations with a single stage lowers communication, and using the method of characteristics to follow information as it propagates enables large time steps. Using a non-oscillatory interpolant, the method is stable without post-hoc filtering. Characteristic variables (built from interface flux vectors) are integrated upstream from interfaces along their trajectories to compute time-averaged fluxes over a time step. Thus we call this method a Flux-Based Characteristic Semi-Lagrangian (FBCSL) method. Multidimensionality is achieved via a second-order accurate Strang operator splitting. Spatial accuracy is achieved via the third- to fifth-order accurate Weighted Essentially Non-Oscillatory (WENO) interpolant. We implement the theory to form a 2-D non-hydrostatic compressible (Euler system) atmospheric model in which standard test cases confirm accuracy and stability. We maintain stability with time steps larger than CFL = 1 (CFL number determined by the acoustic wave speed, not advection) but note that accuracy degrades unacceptably for most cases with CFL > 2. For the smoothest test case, we ran out to CFL = 7 to investigate the error associated with simulation at large CFL number time steps. Analysis suggests improvement of trajectory computations will improve error for large CFL numbers.}, number={4}, journal={JOURNAL OF COMPUTATIONAL PHYSICS}, author={Norman, Matthew R. and Nair, Ramachandran D. and Semazzi, Fredrick H. M.}, year={2011}, month={Feb}, pages={1567–1584} }
 @article{semazzi_2011, title={Framework for climate services in developing countries}, volume={47}, ISSN={["0936-577X"]}, DOI={10.3354/cr00955}, abstractNote={An embryonic framework now exists for the provision of climate services in developing countries via the Regional Climate Outlook Forum supported by the World Meteorological Organization (WMO) Climate Information and Prediction Services (CLIPS) project. However, in general, the major advances in climate science research made during recent decades have hardly improved climate services or socio-economic conditions. It is therefore important, while the Global Framework for Climate Services (GFCS) is being developed, to examine the reasons for these shortcomings and formulate the appropriate mechanisms to address this problem. Although the lack of financial and technological resources, and the necessary infrastructure are critical drawbacks to addressing the climate change problem, we believe the major obstacle is the existence of a self-sustaining cycle, which is continuously eroding and undermining progress. This cycle begins with poor support and funding for research and climate services, leading to the inability of climate service providers to meet stakeholder needs and, thus, further eroding support and perpetuating the cycle. We propose an alternative approach that would break this cycle and create a new class of stakeholders for climate services in developing countries, who will use and advocate for funding and other forms of support for relevant research in the field and its outcomes. We propose a framework for the development of climate risk management strategies (CRMS) and climate services in developing countries. This framework comprises 3 components, namely, implementation sites for the CRMS incubation projects, a joint task force of Climate Variability and Predictability (CLIVAR) and CLIPS for guiding the relevant cross-cut research, and a WMO-World Climate Research Program mechanism for coordinating the CRMS agenda.}, number={1-2}, journal={CLIMATE RESEARCH}, author={Semazzi, F. H. M.}, year={2011}, pages={145–150} }
 @article{peng_xie_liu_semazzi_2010, title={Application of Scale-Selective Data Assimilation to Regional Climate Modeling and Prediction}, volume={138}, ISSN={["1520-0493"]}, DOI={10.1175/2009mwr2974.1}, abstractNote={Abstract}, number={4}, journal={MONTHLY WEATHER REVIEW}, author={Peng, Shiqiu and Xie, Lan and Liu, Bin and Semazzi, Fredrick}, year={2010}, month={Apr}, pages={1307–1318} }
 @article{norman_semazzi_nair_2009, title={Conservative cascade interpolation on the sphere: An intercomparison of various non-oscillatory reconstructions}, volume={135}, ISSN={["1477-870X"]}, DOI={10.1002/qj.402}, abstractNote={Abstract}, number={640}, journal={QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY}, author={Norman, Matthew R. and Semazzi, Fredrick H. M. and Nair, Ramachandran D.}, year={2009}, month={Apr}, pages={795–805} }
 @article{davis_bowden_semazzi_xie_onol_2009, title={Customization of RegCM3 Regional Climate Model for Eastern Africa and a Tropical Indian Ocean Domain}, volume={22}, ISSN={["1520-0442"]}, url={http://dx.doi.org/10.1175/2009jcli2388.1}, DOI={10.1175/2009JCLI2388.1}, abstractNote={Abstract}, number={13}, journal={JOURNAL OF CLIMATE}, author={Davis, Neil and Bowden, Jared and Semazzi, Fredrick and Xie, Lian and Onol, Baris}, year={2009}, month={Jul}, pages={3595–3616} }
 @article{anyah_semazzi_2009, title={Idealized simulation of hydrodynamic characteristics of Lake Victoria that potentially modulate regional climate}, volume={29}, ISSN={["0899-8418"]}, DOI={10.1002/joc.1795}, abstractNote={Abstract}, number={7}, journal={INTERNATIONAL JOURNAL OF CLIMATOLOGY}, author={Anyah, Richard O. and Semazzi, Fredrick}, year={2009}, month={Jun}, pages={971–981} }
 @article{oenol_semazzi_2009, title={Regionalization of Climate Change Simulations over the Eastern Mediterranean}, volume={22}, ISSN={["1520-0442"]}, DOI={10.1175/2008JCLI1807.1}, abstractNote={Abstract}, number={8}, journal={JOURNAL OF CLIMATE}, author={Oenol, Baris and Semazzi, Fredrick H. M.}, year={2009}, month={Apr}, pages={1944–1961} }
 @article{bowden_semazzi_2007, title={Empirical analysis of intraseasonal climate variability over the greater horn of Africa}, volume={20}, ISSN={["1520-0442"]}, url={http://dx.doi.org/10.1175/2007jcli1587.1}, DOI={10.1175/2007JCLI1587.1}, abstractNote={Abstract}, number={23}, journal={JOURNAL OF CLIMATE}, author={Bowden, Jared H. and Semazzi, Fredrick H. M.}, year={2007}, month={Dec}, pages={5715–5731} }
 @article{anyah_semazzi_2007, title={Variability of East African rainfall based on multiyear RegCM3 simulations}, volume={27}, ISSN={["1097-0088"]}, DOI={10.1002/joc.1401}, abstractNote={Abstract}, number={3}, journal={INTERNATIONAL JOURNAL OF CLIMATOLOGY}, author={Anyah, Richard O. and Semazzi, Fredrick H. M.}, year={2007}, month={Mar}, pages={357–371} }
 @article{semazzi_mera_2006, title={An extended procedure for implementing the relative operating characteristic graphical method}, volume={45}, ISSN={["1558-8432"]}, DOI={10.1175/JAM2397.1}, abstractNote={Abstract}, number={9}, journal={JOURNAL OF APPLIED METEOROLOGY AND CLIMATOLOGY}, author={Semazzi, Fredrick H. M. and Mera, Roberto J.}, year={2006}, month={Sep}, pages={1215–1223} }
 @article{fall_niyogi_semazzi_2006, title={Analysis of mean climate conditions in Senegal (1971-98)}, volume={10}, DOI={10.1175/ei158.1}, abstractNote={Abstract}, journal={Earth Interactions}, author={Fall, S. and Niyogi, D. and Semazzi, F. H. M.}, year={2006} }
 @article{anyah_semazzi_2006, title={Climate variability over the Greater Horn of Africa based on NCAR AGCM ensemble}, volume={86}, ISSN={["0177-798X"]}, DOI={10.1007/s00704-005-0203-7}, number={1-4}, journal={THEORETICAL AND APPLIED CLIMATOLOGY}, author={Anyah, R. O. and Semazzi, F. H. M.}, year={2006}, month={Sep}, pages={39–62} }
 @article{mera_niyogi_buol_wilkerson_semazzi_2006, title={Potential individual versus simultaneous climate change effects on soybean (C-3) and maize (C-4) crops: An agrotechnology model based study}, volume={54}, ISSN={["1872-6364"]}, DOI={10.1016/j.gloplacha.2005.11.003}, abstractNote={Landuse/landcover change induced effects on regional weather and climate patterns and the associated plant response or agricultural productivity are coupled processes. Some of the basic responses to climate change can be detected via changes in radiation (R), precipitation (P), and temperature (T). Past studies indicate that each of these three variables can affect LCLUC response and the agricultural productivity. This study seeks to address the following question: What is the effect of individual versus simultaneous changes in R, P, and T on plant response such as crop yields in a C3 and a C4 plant? This question is addressed by conducting model experiments for soybean (C3) and maize (C4) crops using the DSSAT: Decision Support System for Agrotechnology Transfer, CROPGRO (soybean), and CERES-Maize (maize) models. These models were configured over an agricultural experiment station in Clayton, NC [35.65°N, 78.5°W]. Observed weather and field conditions corresponding to 1998 were used as the control. In the first set of experiments, the CROPGRO (soybean) and CERES-Maize (maize) responses to individual changes in R and P (25%, 50%, 75%, 150%) and T (± 1, ± 2 °C) with respect to control were studied. In the second set, R, P, and T were simultaneously changed by 50%, 150%, and ± 2 °C, and the interactions and direct effects of individual versus simultaneous variable changes were analyzed. For the model setting and the prescribed environmental changes, results from the first set of experiments indicate: (i) precipitation changes were most sensitive and directly affected yield and water loss due to evapotranspiration; (ii) radiation changes had a non-linear effect and were not as prominent as precipitation changes; (iii) temperature had a limited impact and the response was non-linear; (iv) soybeans and maize responded differently for R, P, and T, with maize being more sensitive. The results from the second set of experiments indicate that simultaneous change analyses do not necessarily agree with those from individual changes, particularly for temperature changes. Our analysis indicates that for the changing climate, precipitation (hydrological), temperature, and radiative feedbacks show a non-linear effect on yield. Study results also indicate that for studying the feedback between the land surface and the atmospheric changes, (i) there is a need for performing simultaneous parameter changes in the response assessment of cropping patterns and crop yield based on ensembles of projected climate change, and (ii) C3 crops are generally considered more sensitive than C4; however, the temperature–radiation related changes shown in this study also effected significant changes in C4 crops. Future studies assessing LCLUC impacts, including those from agricultural cropping patterns and other LCULC–climate couplings, should advance beyond the sensitivity mode and consider multivariable, ensemble approaches to identify the vulnerability and feedbacks in estimating climate-related impacts.}, number={1-2}, journal={GLOBAL AND PLANETARY CHANGE}, author={Mera, Roberto J. and Niyogi, Dev and Buol, Gregory S. and Wilkerson, Gail G. and Semazzi, Fredrick H. M.}, year={2006}, month={Nov}, pages={163–182} }
 @article{anyah_semazzi_xie_2006, title={Simulated physical mechanisms associated with climate variability over Lake Victoria basin in East Africa}, volume={134}, ISSN={["1520-0493"]}, DOI={10.1175/MWR3266.1}, abstractNote={Abstract}, number={12}, journal={MONTHLY WEATHER REVIEW}, author={Anyah, Richard O. and Semazzi, Fredrick H. M. and Xie, Lian}, year={2006}, month={Dec}, pages={3588–3609} }
 @article{fall_semazzi_dutta_niyogi_anyah_bowden_2006, title={The spatiotemporal climate variability over Senegal and its relationship to global climate}, volume={26}, ISSN={["1097-0088"]}, url={http://dx.doi.org/10.1002/joc.1355}, DOI={10.1002/joc.1355}, abstractNote={Abstract}, number={14}, journal={INTERNATIONAL JOURNAL OF CLIMATOLOGY}, author={Fall, Souleymane and Semazzi, Fredrick H. M. and Dutta, Dev and Niyogi, S. and Anyah, Richard O. and Bowden, Jared}, year={2006}, month={Nov}, pages={2057–2076} }
 @article{semazzi_scroggs_pouliot_mckee-burrows_norman_poojary_tsai_2005, title={On the accuracy of semi-Lagrangian numerical simulation of internal gravity wave motion in the atmosphere}, volume={83}, ISSN={["2186-9057"]}, DOI={10.2151/jmsj.83.851}, abstractNote={We have investigated the accuracy ofthe semi-implicit semi-Lagrangian (SISL) method in simulating internal gravity wave (IGW) motion. We have focused on the relative accuracy of the hydrostatic, and nonhydrostatic IGW solutions. The analysis is based on a linearized model and a Global Circulation Model-Dynamic Core (GCM-DC) with a stretched grid.The nonhydrostatic version of the GCM-DC model produces the familiar IGW train disturbance anchored to an isolated hypothetical mountain. The wave has a distinct tilt away from the vertical direction, which is consistent with classical theory. For the hydrostatic version of the model, the axis of the resulting IGW train rests nearly perpendicular to the mountain top, thus again consistent with classical theory. Increasing the time step from 10 s; Courant number (Cn) = 0.5; to 60 s (Cn = 3.0), results in stable solutions for both the hydrostatic and nonhydrostatic versions of the model. The nonhydrostatic solution is in close agreement with the control run however, the hydrostatic solution exhibits large phase truncation errors.The solutions for the one-dimensional linearized SISL model confirm the GCM-DC results that the nonhydrostatic IGW train is less damped and shifted by the SISL scheme than the corresponding hydrostatic IGW motion. The linear solutions indicate very high accuracy of the physical mode of the solution, but it rapidly deteriorates when Cn exceeds unity. As Δt → 0 the amplitude of the computational mode tends to zero and its frequency to infinity. However, as Δt → ∞, the frequency of the computational SISL mode asymptotically approaches the value of the frequency of the corresponding SISL physical mode. Furthermore, the amplitude of the SISL computational mode is directly proportional to the size of the time step. Therefore, at large time steps, the amplification of the computational mode could offset some of the numerical damping of the physical mode by the SISL scheme.}, number={5}, journal={JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN}, author={Semazzi, FHM and Scroggs, JS and Pouliot, GA and McKee-Burrows, AL and Norman, M and Poojary, V and Tsai, YM}, year={2005}, month={Oct}, pages={851–869} }
 @article{song_semazzi_xie_ogallo_2004, title={A coupled regional climate model for the Lake Victoria basin of East Africa}, volume={24}, ISSN={["1097-0088"]}, DOI={10.1002/joc.983}, abstractNote={Abstract}, number={1}, journal={INTERNATIONAL JOURNAL OF CLIMATOLOGY}, author={Song, Y and Semazzi, FHM and Xie, L and Ogallo, LJ}, year={2004}, month={Jan}, pages={57–75} }
 @article{anyah_semazzi_2004, title={Simulation of the sensitivity of Lake Victoria basin climate to lake surface temperatures}, volume={79}, ISSN={["1434-4483"]}, DOI={10.1007/s00704-004-0057-4}, number={1-2}, journal={THEORETICAL AND APPLIED CLIMATOLOGY}, author={Anyah, RO and Semazzi, FHM}, year={2004}, month={Oct}, pages={55–69} }
 @article{schreck_semazzi_2004, title={Variability of the recent climate of eastern Africa}, volume={24}, ISSN={["1097-0088"]}, DOI={10.1002/joc.1019}, abstractNote={Abstract}, number={6}, journal={INTERNATIONAL JOURNAL OF CLIMATOLOGY}, author={Schreck, CJ and Semazzi, FHM}, year={2004}, month={May}, pages={681–701} }
 @article{nair_scroggs_semazzi_2003, title={A forward-trajectory global semi-Lagrangian transport scheme}, volume={190}, ISSN={["1090-2716"]}, DOI={10.1016/S0021-9991(03)00274-2}, abstractNote={A forward-trajectory semi-Lagrangian scheme for advection on the surface of the sphere is proposed. The advection scheme utilizes the forward (downstream) trajectory originating at Eulerian grid points and cascade interpolation, a sequence of 1D interpolations, to transfer data from the downstream Lagrangian points to the Eulerian points. A new and more accurate algorithm determines pole values. The resulting forward-trajectory semi-Lagrangian scheme can easily incorporate high-order trajectory integration methods. This avoids the standard iterative process in a typical backward-trajectory scheme. Two third-order accurate schemes and a second-order accurate scheme are presented. A mass-conservative version of the forward-trajectory semi-Lagrangian scheme is also derived within the cascade interpolation framework. Mass from a Lagrangian cell is transferred to the corresponding Eulerian cell with two 1D remappings through an intermediate cell system. Mass in the polar region is redistributed by way of an efficient local approximation. The resulting scheme is globally conservative, but restricted to meridional Courant number, Cθ⩽1.}, number={1}, journal={JOURNAL OF COMPUTATIONAL PHYSICS}, author={Nair, RD and Scroggs, JS and Semazzi, FHM}, year={2003}, month={Sep}, pages={275–294} }
 @article{semazzi_2003, title={Air quality research: perspective from climate change modelling research}, volume={29}, ISSN={["0160-4120"]}, DOI={10.1016/S0160-4120(02)00184-8}, abstractNote={A major component of climate change is a manifestation of changes in air quality. This paper explores the question of air quality from the climate change modelling perspective. It reviews recent research advances on the cause-effect relationships between atmospheric air composition and climate change, primarily based on the Intergovernmental Panel on Climate Change (IPCC) assessment of climate change over the past decade. There is a growing degree of confidence that the warming world over the past century was caused by human-related changes in the composition of air. Reliability of projections of future climate change is highly dependent on future emission scenarios that have been identified that in turn depend on a multitude of complicated interacting social-economic factors. Anticipated improvements in the performance of climate models is a major source of optimism for better climate projections in the future, but the real benefits of its contribution will be closely coupled with other sources of uncertainty, and in particular emission projections.}, number={2-3}, journal={ENVIRONMENT INTERNATIONAL}, author={Semazzi, F}, year={2003}, month={Jun}, pages={253–261} }
 @article{nair_scroggs_semazzi_2002, title={Efficient conservative global transport schemes for climate and atmospheric chemistry models}, volume={130}, ISSN={["0027-0644"]}, DOI={10.1175/1520-0493(2002)130<2059:ECGTSF>2.0.CO;2}, abstractNote={A computationally efficient mass-conservative transport scheme over the sphere is proposed and tested. The scheme combines a conservative finite-volume method with an efficient semi-Lagrangian scheme based on the dimension splitting ‘‘cascade’’ method. In the regions near the poles where the conservative cascade procedure breaks down, a globally conservative, but locally approximate scheme is used. This procedure is currently restricted to polar meridional Courant numbers less than one. The resulting conservative cascade scheme is evaluated using a solid-body rotation test and deformational flow test, and found to be both accurate and efficient. Compared to the traditional semi-Lagrangian scheme employing a bicubic-Lagrange interpolator, the proposed scheme is considerably more accurate and almost twice as fast while conserving mass exactly.}, number={8}, journal={MONTHLY WEATHER REVIEW}, author={Nair, RD and Scroggs, JS and Semazzi, FHM}, year={2002}, month={Aug}, pages={2059–2073} }
 @article{semazzi_song_2001, title={A GCM study of climate change induced by deforestation in Africa}, volume={17}, ISSN={["0936-577X"]}, DOI={10.3354/cr017169}, abstractNote={In this modeling study we investigated the potential climate change which would result from totally clearing the tropical rain forests in Africa. The primary research vehicle in our investigation was the standard version of the National Center for Atmospheric Research (NCAR) CCM3 global climate model (GCM), with a horizontal resolution of triangular spectral truncation T42 (approximately 2.8° × 2.8°). Two separate 10 yr simulations were performed; for each of these the global climatological sea surface temperature field was prescribed. The purpose of the 10 yr simulations was to provide a sufficiently large ensemble whose average minimizes model noise errors. In the control simulation normal vegetation was prescribed. The design of the anomaly experiment was similar to the control run except that the tropical rainforest regions in Africa were replaced by savanna grassland vegetation. The CCM3 GCM successfully simulated the primary features of the seasonal mean climate conditions over Africa. The model results show that replacement of tropical rain forest vegetation with savanna grassland vegetation produces the following climate changes over Africa: (1) Over the deforested region, the model results indicate a significant reduction in areaaveraged rainfall throughout the year. The decrease ranges between 2 to 3 mm d–1 during the northern hemispheric summer months, when the region experiences the driest conditions (July to September), and less than 1 mm d–1 during the wettest months (autumn and spring). (2) Over southern Africa deforestation results in substantial rainfall reduction over Mozambique and rainfall increase over Botswana, Zambia, the southern region of the Democratic Republic of the Congo, and parts of South Africa. Changes in the trapped Rossby wave train activity generated by the mid-tropospheric latent heating over the tropical forest region are responsible for the continental-scale teleconnection climate response. (3) Over Eastern and Western Africa the impact of deforestation is primarily characterized by a reduction in rainfall, however the adopted GCM T42 resolution may not have been adequate to resolve the large contrasts in terrain and vegetation types. (4) Over the rest of Africa the response is relatively weak.}, number={2}, journal={CLIMATE RESEARCH}, author={Semazzi, FHM and Song, Y}, year={2001}, month={Aug}, pages={169–182} }
 @article{indeje_semazzi_xie_ogallo_2001, title={Mechanistic model simulations of the East African climate using NCAR regional climate model: Influence of large-scale orography on the Turkana low-level jet}, volume={14}, ISSN={["1520-0442"]}, DOI={10.1175/1520-0442(2001)014<2710:MMSOTE>2.0.CO;2}, abstractNote={Abstract The National Center for Atmospheric Research regional climate model (RegCM) is employed to study the dynamics of the Turkana low-level jet that lies between the Ethiopian and the East African highlands, and also investigate the mechanisms responsible for the observed dry conditions over the Lake Turkana basin that lies in the wider section of the Turkana channel. The role of the large-scale orography and two other forcing factors namely the large-scale monsoonal flow and the Turkana channel depth are investigated in order to understand the kinematics of the jet. The simulated patterns of the Turkana easterly low-level jet compares well with its observed characteristics. Strong winds are indicated in the channel throughout the study period of October to December, with the wind speed decreasing in the middle and wider region of the channel. A split in the jet core is also shown in the middle of the channel. The level of maximum winds (∼11 m s−1) occurs in the layers 930-hPa and 650-hPa levels. The ...}, number={12}, journal={JOURNAL OF CLIMATE}, author={Indeje, M and Semazzi, FHM and Xie, L and Ogallo, LJ}, year={2001}, pages={2710–2724} }
 @article{indeje_semazzi_ogallo_2000, title={ENSO signals in East African rainfall seasons}, volume={20}, ISSN={["0899-8418"]}, DOI={10.1002/(SICI)1097-0088(200001)20:1<19::AID-JOC449>3.3.CO;2-S}, abstractNote={The evolutions of ENSO modes in the seasonal rainfall patterns over East Africa are examined in this study. The study covers the period 1961–1990. Both rotated empirical orthogonal function (EOF) and simple correlation analyses were used to delineate a network of 136 stations over East Africa into homogeneous rainfall regions in order to derive rainfall indices. Time series generated from the delineated regions were later used in the rainfall/ENSO analyses. Such analyses involved the development of composite rainfall map patterns for El Niño and post-ENSO (+1) years in order to investigate the associations between seasonal evolution of El Niño–Southern Oscillation (ENSO) signals and the space-time evolution of rainfall anomalies over the region. Analyses based on both EOF and simple correlation techniques yielded eight homogeneous rainfall regions over East Africa. The results showed unique seasonal evolution patterns in rainfall during the different phases of the ENSO cycles. East African rainfall performance characteristics were stratified to identify distinct rainfall anomaly patterns associated with ENSO and post-ENSO (+1) years. These can be applied in conjunction with skilful long lead (up to 12 months) ENSO prediction to provide guidance on likely patterns of seasonal rainfall anomalies over the region. Such information can be crucial for early warning of socio-economic disasters associated with extreme rainfall anomalies over East Africa. Copyright © 2000 Royal Meteorological Society}, number={1}, journal={INTERNATIONAL JOURNAL OF CLIMATOLOGY}, author={Indeje, M and Semazzi, FHM and Ogallo, LJ}, year={2000}, month={Jan}, pages={19–46} }
 @article{indeje_semazzi_2000, title={Relationships between QBO in the lower equatorial stratospheric zonal winds and east African seasonal rainfall}, volume={73}, ISSN={["0177-7971"]}, DOI={10.1007/s007030050075}, number={3-4}, journal={METEOROLOGY AND ATMOSPHERIC PHYSICS}, author={Indeje, M and Semazzi, FHM}, year={2000}, pages={227–244} }
 @article{sun_semazzi_giorgi_ogallo_1999, title={Application of the NCAR Regional Climate Model to eastern Africa - 2. Simulation of interannual variability of short rains}, volume={104}, ISSN={["2169-897X"]}, DOI={10.1029/1998JD200050}, abstractNote={We have applied the NCAR RegCM2 to the simulation of the interannual variability of precipitation over eastern Africa for the short‐rains season by performing a set of experiments for the years 1982 to 1993. The model reproduced the observed interannual variability of precipitation in most of the years. The results show that remote factors play a dominant role in determining the precipitation anomalies. Interannual variability of precipitation over Tanzania is closely related to El Niño events in their mature phase and sea surface temperature (SST) anomalies over the Indian and Atlantic Oceans. The southward shift of the Arabian High results in a southward shift of the zonal component of the Intertropical Convergence Zone (ITCZ), which is responsible for early onset of the rainy season (e.g., 1982 and 1986). The enhanced St. Helena High and weaker Mascarene High lead to the eastward shift of the meridional branch of the ITCZ for the wet years. Model simulations confirmed a strong positive correlation between precipitation anomalies over Lake Victoria and the warm El Niño‐Southern Oscillation events, by which enhanced moist westerly flow from the Atlantic Ocean and the mainly easterly flow from the Indian Ocean converge over Lake Victoria during wet years. The interannual variability of precipitation over Lake Victoria and the western Kenya Highlands (WKH) are strongly coupled. Positive precipitation anomalies over the WKH region are usually associated with weaker Arabian High and Mascarene High, which weaken the large‐scale divergence over the WKH region and favor the development of convection. The interannual variability of precipitation over eastern Kenya Highlands (EKH) is not directly related to the El Niño events, but the association with a warm SST anomaly pattern over the western Indian Ocean is evident during wet years. An El Niño signal is, however, evident for wet years over the Turkana Channel, warm SST anomalies over the northern Indian Ocean contribute enhanced water vapor transport over the region.}, number={D6}, journal={JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES}, author={Sun, LQ and Semazzi, FHM and Giorgi, F and Ogallo, L}, year={1999}, month={Mar}, pages={6549–6562} }
 @article{sun_semazzi_giorgi_ogallo_1999, title={Application of the NCAR regional climate model to eastern Africa - 1. Simulation of the short rains of 1988}, volume={104}, ISSN={["2169-8996"]}, DOI={10.1029/1998JD200051}, abstractNote={The National Center for Atmospheric Research (NCAR) Regional Climate Model (RegCM2) is employed to investigate the physical mechanisms that govern the October‐December rains over eastern Africa. The model employs the Mercator conformai projection, with a domain of 5580 km × 5040 km centered at 31°E, 4°S, and a horizontal grid point spacing of 60 km. The simulation period is October‐December 1988, and the model initial and lateral boundary conditions are taken from ECMWF reanalysis. A number of month‐long simulations have been conducted to optimize various parameterizations of the model which include the following factors: cumulus convection, moisture parameterization, radiative transfer formulation, surface processes, boundary layer physics, and the lateral boundary conditions. The model was successfully customized over eastern Africa. The model simulates the large‐scale circulation characteristics over the region as well as local features such as the dominant precipitation maxima, the Turkana low‐level jet, and the diurnal reversal in the lake/land breeze circulation over Lake Victoria. Several model deficiencies are also identified. They include a negative rainfall bias over the western portions of the domain and the Kenya Highlands and a temperature bias over the tropical forest regions. Systematic analysis of surface water budget reveals that evapotranspiration is a major sink in the water budget over the regions where precipitation is moderate or small, while the role of runoff and drainage becomes important over the regions where precipitation is abundant. The model simulations also suggest that during the short‐rains season, the large‐scale circulation anomalies play the most important role in shaping the precipitation anomalies.}, number={D6}, journal={JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES}, author={Sun, LQ and Semazzi, FHM and Giorgi, F and Ogallo, L}, year={1999}, month={Mar}, pages={6529–6548} }
 @article{qian_semazzi_scroggs_1998, title={A global nonhydrostatic semi-Lagrangian atmospheric model with orography}, volume={126}, ISSN={["0027-0644"]}, DOI={10.1175/1520-0493(1998)126<0747:AGNSLA>2.0.CO;2}, abstractNote={A global nonhydrostatic semi-implicit semi-Lagrangian (SISL) atmospheric model with orography has been developed. The height-based terrain-following σz coordinate of Gal-Chen and Somerville is used to incorporate the orography. A 3D vector form of the SISL formulation is proposed. It is based on the complete Navier–Stokes equations. The model is stable for large time steps of up to 1 h at horizontal/vertical resolution of 2.8125°/1200 m. Isolated bell-shaped mountain profiles and real orography are employed to evaluate the model performance. The sensitivity of the model with orography to the order of accuracy of the uncentering scheme, the reference temperature (T), and size of the time step are similar to that of the model without orography described in Semazzi et al. The authors find that for successful execution of the model, it is important that the orographic height Zs, the reference state mass variable (qs), and T satisfy the hydrostatic balance relationship in the terrain-following σz coordinate system. This formulation effectively controls the generation of unphysical orographic induced computational noise usually encountered in connection with semi-Lagrangian models. The global model used here is based on the complete dynamical Navier–Stokes equations, however, it is run at coarse resolutions, for which nonhydrostatic effects are negligible. In the future, when the computing resources permit, the model will be a valuable vehicle for investigating the role of multiple-scale interaction, including the effects of nonhydrostatic dynamics.}, number={3}, journal={MONTHLY WEATHER REVIEW}, author={Qian, JH and Semazzi, FHM and Scroggs, JS}, year={1998}, month={Mar}, pages={747–771} }
 @article{semazzi_sun_1997, title={The role of orography in determining the Sahelian climate}, volume={17}, ISSN={["0899-8418"]}, DOI={10.1002/(SICI)1097-0088(199705)17:6<581::AID-JOC134>3.0.CO;2-E}, abstractNote={We have examined numerical modelling evidence based on the NASA GEOS-1 general circulation model in order to investigate the role of orography in determining the West African summer climate anomalies. Orographic climatic control and the influence of sea-surface temperature (SST) anomaly forcing were investigated by systematic suppression or inclusion of these effects in the numerical experiments. Our main finding is that the orography of Africa plays a major role in determining the climate of the Sahel and the coastal region of West Africa during the northern hemispheric summer season. These orographic effects are comprised of: (i) a quasi-stationary orographic ridge–trough dipole generated by the passage of the low-level prevailing easterlies over the Atlas–Ahaggar mountain complex over northern Africa, and (ii) an elongated zonal windward orographic ridge generated as the cross-equatorial summer monsoons from the South Atlantic Ocean basin ascends over the elevated landmass of West Africa. 
 
 
 
Over the Sahel, the moist south-westerly flow emanating from the Atlas–Ahaggar orographic trough over the Atlantic Ocean and the dry hot north-easterlies originating from the corresponding orographic windward ridge tend to converge along a zonal axis thus reinforcing the Inter-Tropical Convergence Zone. This results in wetter conditions over the Sahel than would have been the case in the absence of orography. The model simulations show that further to the south along the coastal region of West Africa, the zonal orographic ridge results in drier conditions than in the model runs when orography is suppressed. The net result is a permanent orographic-induced rainfall dipole pattern over West Africa. 
 
 
 
Further model simulations were conducted in which the 1973 SST anomaly conditions were described with or without the orography of Africa. The 1973 SST anomaly pattern is characterized by positive anomalies in the Southern Hemisphere and negative anomalies in the Northern Hemisphere. The model results show a weaker orographic-induced rainfall dipole pattern across West Africa in response to the 1973 SST anomaly pattern. The net result is wetter conditions along the coastal region and rainfall deficits over the Sahelian zonal strip. © 1997 by the Royal Meteorological Society.}, number={6}, journal={INTERNATIONAL JOURNAL OF CLIMATOLOGY}, author={Semazzi, FHM and Sun, LQ}, year={1997}, month={May}, pages={581–596} }