@article{reeves_lin_rotunno_2008, title={Dynamic forcing and mesoscale variability of heavy precipitation events over the Sierra Nevada mountains}, volume={136}, ISSN={["0027-0644"]}, DOI={10.1175/2007MWR2164.1}, abstractNote={Abstract
               The aim of this research is to investigate the causes for an isolated maximum in precipitation that is typically found along the northern half of the Sierra Nevada mountains of California, in the vicinity of Plumas National Forest (PNF), during moderate to heavy precipitation events. Particular attention was paid to the role various mesoscale (i.e., <200 km) terrain features may have played in localizing the precipitation at PNF. Numerical simulations and sensitivity experiments for two cases of heavy precipitation at PNF reveal that the extent to which terrain acts to focus precipitation is case sensitive. In the first case, the upstream flow was characterized by a strong horizontal gradient in wind speed and moisture. This gradient led to differential deflection of airstreams incident to the range and, consequently, localized convergence and enhanced rain rates at PNF. This localized enhancement occurred regardless of whether any terrain variations were present in the simulations or not. The second case was characterized by more a horizontally uniform upstream flow and showed a much stronger sensitivity to terrain variations, in particular, short- and long-wavelength undulations along the leading (west) edge of the Sierra Nevada range. When these undulations were removed, no localized maxima in precipitation occurred.}, number={1}, journal={MONTHLY WEATHER REVIEW}, author={Reeves, Heather Dawn and Lin, Yuh-Lang and Rotunno, Richard}, year={2008}, month={Jan}, pages={62–77} }
 @article{reeves_lin_2007, title={The effects of a mountain on the propagation of a preexisting convective system for blocked and unblocked flow regimes}, volume={64}, ISSN={["1520-0469"]}, DOI={10.1175/JAS3959.1}, abstractNote={Abstract
               Observations and previous research of squall lines impinging on mountain ranges have revealed that the squall lines sometimes stall upstream of the mountains for several hours leading to copious accumulations of precipitation. It has been hypothesized that squall-line stagnation may be more prone to occur in flows where the Froude number (F = U/Nh, where U is the basic-state wind, N is the Brunt–Väisälä frequency, and h is the mountain height) is low. This hypothesis is tested herein through a series of idealized, two-dimensional experiments where a convective system was triggered upstream of a mesoscale mountain in conditionally unstable flow. For simulations with relatively low Froude numbers, stagnation of the preexisting convective system was not observed. In the simulations with high values of F, squall lines were noted to stagnate between 100 and 200 km upstream of the mountain. This result indicates that squall-line stagnation may be more favored for moderate to large values of F for conditionally unstable flow. The mechanisms leading to the formation of the stationary convective system upstream of the mountain in the unblocked flows were explored and it was found that evaporative cooling played a pivotal role in the stagnation of the squall line.}, number={7}, journal={JOURNAL OF THE ATMOSPHERIC SCIENCES}, author={Reeves, Heather Dawn and Lin, Yuh-Lang}, year={2007}, month={Jul}, pages={2401–2421} }
 @article{reeves_lin_2006, title={Effect of stable layer formation over the Po valley on the development of convection during MAP IOP-8}, volume={63}, ISSN={["1520-0469"]}, DOI={10.1175/JAS3759.1}, abstractNote={AbstractDuring intensive observation period (IOP)-8 of the Mesoscale Alpine Program, there was a stable layer of air in the lowest levels of the Po Valley and just upstream of the Apennines. In this study, the effects of the stable layer on the formation of convection in the southern Alpine region were investigated through a series of two-dimensional, idealized experiments. The goals of this study were twofold: 1) to determine if stable layer strength affected the placement of convection and 2) to test the notion that the stable layer during IOP-8 behaved as an effective mountain. To accomplish the first objective, three simulations were compared in which the strength of the inversion and low-level cooling in the Po Valley and upstream of the Apennines was varied. The results of these simulations show that the stronger the inversion and low-level cooling, the farther south the convection was positioned. Additionally, it was found that convection developed as a result of the formation of a broad region of moist instability over the stable layer. Cellular convection developed in this region of moist instability. The second objective was tested through a simulation where the cold pool was replaced by terrain (MMTN). As in the reference (or STB10) simulation, the upslope of the terrain in the MMTN simulation was characterized by a wide zone of moist instability. However, wave structures to the lee of the Apennines were markedly different in the STB10 and MMTN simulations. This led to different convective and precipitation patterns, with the MMTN simulation exhibiting heavier convection over the Po Valley while the heaviest convection in STB10 was upstream of the Apennines. These results suggest that, at best, the stable layer in the STB10 simulation can only be roughly approximated by terrain.}, number={10}, journal={JOURNAL OF THE ATMOSPHERIC SCIENCES}, author={Reeves, Heather Dawn and Lin, Yuh-Lang}, year={2006}, month={Oct}, pages={2567–2584} }
 @article{hoggarth_reeves_lin_2006, title={Formation and maintenance mechanisms of the stable layer over the Po valley during MAP IOP-8}, volume={134}, ISSN={["0027-0644"]}, DOI={10.1175/MWR3251.1}, abstractNote={Abstract
               During intensive observation period 8 (IOP-8) of the Mesoscale Alpine Program, a strong stable layer formed over Italy’s Po Valley and the northern Ligurian Sea. This stable layer has been shown in previous research to be important for the formation of convection over the Ligurian Sea and the lack thereof over the Po Valley and southern slopes of the Alps. The purpose of this study is to investigate the mechanisms that acted to form and maintain the stable layer during IOP-8. This aim is accomplished through inspection of observed data as well as numerical simulations and sensitivity experiments. Observations and reanalysis data show that starting on 17 October 1999, a relatively cool, stable air mass was advected around the eastern side of the Alps into the lower atmosphere of the Po Valley. Both observational data and model output show this air mass as being blocked as it encountered the western Alps, thus resulting in an accumulation of cool, stable air at low levels in the Po Valley during the ensuing 60 h. When southerly flow approached northern Italy beginning on 20 October 1999, both the western Alps and the northern Alps appeared to help retain the low-level, cool, stable air over the Po Valley. A trajectory and sounding analysis shows that warmer, less stable air originating from over the southern Mediterranean Sea was advected atop the low-lying stable layer within the Po Valley. It is hypothesized that this differential advection, as well as blocking by the western and northern flanks of the Alps, were responsible for the longevity of the stable layer. A series of numerical simulations and sensitivity experiments were performed to test the above hypotheses. These tests support the hypotheses. Other mechanisms were also considered, including blocking of solar radiation by clouds, friction, and evaporative cooling. These simulations revealed that all three processes were critical for the longevity of the stable layer and point to the importance of accurate model representation of subgrid-scale processes.}, number={11}, journal={MONTHLY WEATHER REVIEW}, author={Hoggarth, Allison M. and Reeves, Heather Dawn and Lin, Yuh-Lang}, year={2006}, month={Nov}, pages={3336–3354} }
 @article{lin_reeves_chen_chiao_2005, title={Formation mechanisms for convection over the Ligurian Sea during MAP IOP-8}, volume={133}, ISSN={["0027-0644"]}, DOI={10.1175/MWR2970.1}, abstractNote={Abstract
               The dynamical impacts of an unusually strong stable layer that developed over the Po Valley and northern Ligurian Sea during Mesoscale Alpine Program (MAP) intensive observation period 8 (IOP-8) on the formation of convection over the Ligurian Sea are explored. Based on numerically simulated equivalent potential temperature, wind vectors, and by a trajectory analysis of parcels both beneath and above the stable layer, it is shown that the stable layer behaved as a material surface or “effective mountain” to the airstreams impinging on it from the south. Additional analyses show that the leading edge of the stable layer was collocated with maxima in upward motion and a strong positive moisture flux. Hence, it was further argued and demonstrated through inspection of soundings upstream of the cold dome and trajectory analyses that lifting by the stable layer enhanced convective activities over the Ligurian Sea. Finally, processes contributing to the maintenance of the stable layer during IOP-8 were explored. It was found that the differential advection of a warm, less stable air mass on top of a cooler, more stable air mass helped maintain the stable layer. The Ligurian Apennines made a secondary contribution to the stagnation of the cool air in the Po Valley by partially blocking this air mass from exiting the valley to the south.}, number={8}, journal={MONTHLY WEATHER REVIEW}, author={Lin, YL and Reeves, HD and Chen, SY and Chiao, S}, year={2005}, month={Aug}, pages={2227–2245} }
 @article{reeves_lackmann_2004, title={An investigation of the influence of latent heat release on cold-frontal motion}, volume={132}, ISSN={["1520-0493"]}, DOI={10.1175/MWR2827.1}, abstractNote={Abstract The effects of condensational heating on cold-frontal translation speed are explored through the use of potential vorticity (PV) diagnostics and model sensitivity experiments. It is hypothesized that condensational heating can lead to faster frontal translation speeds in the presence of vertical shear because of the horizontal propagation of the positive PV anomaly associated with the front. A case study of a cold front with an evolving precipitation structure is presented. A positive correlation existed between the position of condensational heating relative to the frontal zone and frontal translation speed, with faster frontal movement occurring when condensational heating was present in the prefrontal zone. This front was numerically simulated to see if the hypothesized mechanism for frontal movement was active. Through the use of a PV budget, it was confirmed that condensational heating did contribute to the forward propagation of the cold-frontal PV band. Numerical experiments were performed...}, number={12}, journal={MONTHLY WEATHER REVIEW}, author={Reeves, HD and Lackmann, GM}, year={2004}, month={Dec}, pages={2864–2881} }