@article{niyogi_pyle_lei_arya_kishtawal_shepherd_chen_wolfe_2011, title={Urban Modification of Thunderstorms: An Observational Storm Climatology and Model Case Study for the Indianapolis Urban Region}, volume={50}, ISSN={["1558-8432"]}, DOI={10.1175/2010jamc1836.1}, abstractNote={AbstractA radar-based climatology of 91 unique summertime (May 2000–August 2009) thunderstorm cases was examined over the Indianapolis, Indiana, urban area. The study hypothesis is that urban regions alter the intensity and composition/structure of approaching thunderstorms because of land surface heterogeneity. Storm characteristics were studied over the Indianapolis region and four peripheral rural counties approximately 120 km away from the urban center. Using radar imagery, the time of event, changes in storm structure (splitting, initiation, intensification, and dissipation), synoptic setting, orientation, and motion were studied. It was found that more than 60% of storms changed structure over the Indianapolis area as compared with only 25% over the rural regions. Furthermore, daytime convection was most likely to be affected, with 71% of storms changing structure as compared with only 42% at night. Analysis of radar imagery indicated that storms split closer to the upwind urban region and merge again downwind. Thus, a larger portion of small storms (50–200 km2) and large storms (>1500 km2) were found downwind of the urban region, whereas midsized storms (200–1500 km) dominated the upwind region. A case study of a typical storm on 13 June 2005 was examined using available observations and the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5), version 3.7.2. Two simulations were performed with and without the urban land use/Indianapolis region in the fourth domain (1.33-km resolution). The storm of interest could not be simulated without the urban area. Results indicate that removing the Indianapolis urban region caused distinct differences in the regional convergence and convection as well as in simulated base reflectivity, surface energy balance (through sensible heat flux, latent heat flux, and virtual potential temperature changes), and boundary layer structure. Study results indicate that the urban area has a strong climatological influence on regional thunderstorms.}, number={5}, journal={JOURNAL OF APPLIED METEOROLOGY AND CLIMATOLOGY}, author={Niyogi, Dev and Pyle, Patrick and Lei, Ming and Arya, S. Pal and Kishtawal, Chandra M. and Shepherd, Marshall and Chen, Fei and Wolfe, Brian}, year={2011}, month={May}, pages={1129–1144} }
 @article{alapaty_niyogi_chen_pyle_chandrasekar_seaman_2008, title={Development of the flux-adjusting surface data assimilation system for mesoscale models}, volume={47}, ISSN={["1558-8432"]}, DOI={10.1175/2008JAMC1831.1}, abstractNote={Abstract
               The flux-adjusting surface data assimilation system (FASDAS) is developed to provide continuous adjustments for initial soil moisture and temperature and for surface air temperature and water vapor mixing ratio for mesoscale models. In the FASDAS approach, surface air temperature and water vapor mixing ratio are directly assimilated by using the analyzed surface observations. Then, the difference between the analyzed surface observations and model predictions of surface layer temperature and water vapor mixing ratio are converted into respective heat fluxes, referred to as adjustment heat fluxes of sensible and latent heat. These adjustment heat fluxes are then used in the prognostic equations for soil temperature and moisture via indirect assimilation in the form of several new adjustment evaporative fluxes. Thus, simulated surface fluxes for the subsequent model time step are affected such that the predicted surface air temperature and water vapor mixing ratio conform more closely to observations. The simultaneous application of indirect and direct data assimilation maintains greater consistency between the soil temperature–moisture and the surface layer mass-field variables. The FASDAS is coupled to a land surface submodel in a three-dimensional mesoscale model and tests are performed for a 10-day period with three one-way nested domains. The FASDAS is applied in the analysis nudging mode for two coarse-resolution nested domains and in the observational nudging mode for a fine-resolution nested domain. Further, the effects of FASDAS on two different initial specifications of a three-dimensional soil moisture field are also studied. Results indicate that the FASDAS consistently improved the accuracy of the model simulations.}, number={9}, journal={JOURNAL OF APPLIED METEOROLOGY AND CLIMATOLOGY}, author={Alapaty, Kiran and Niyogi, Dev and Chen, Fei and Pyle, Patrick and Chandrasekar, Anantharman and Seaman, Nelson}, year={2008}, month={Sep}, pages={2331–2350} }
 @article{niyogi_holt_zhong_pyle_basara_2006, title={Urban and land surface effects on the 30 July 2003 mesoscale convective system event observed in the southern Great Plains}, volume={111}, number={D19}, journal={Journal of Geophysical Research. Atmospheres}, author={Niyogi, D. and Holt, T. and Zhong, S. and Pyle, P. C. and Basara, J.}, year={2006} }