Using dynamical downscaling to examine mechanisms contributing to the intensification of Central U.S. heavy rainfall events

Abstract

The frequency and intensity of heavy rainfall events have increased in the Central U.S. over the last several decades, and model projections from dynamical downscaling suggest a continuation with climate change. In this study, we examine how climate change might affect mechanisms related to the development of heavy rainfall events that occur on the scale of mesoscale convective systems over the Central U.S. To accomplish these goals, we incorporate dynamical downscaled simulations of two Coupled Model Intercomparison Project phase 5 models in the Weather Research and Forecasting model that accurately simulate heavy rainfall events. For each model, a set of heavy rainfall events that match the frequency, timing, and intensity of observed events are objectively identified in historical and future simulations. We then examine multimodel composites of select atmospheric fields during these events in simulations of historical and future scenarios, enabling an identification of possible physical mechanisms that could contribute to the intensification of heavy rainfall events with climate change. Simulations show that additional moisture is transported into convective updrafts during heavy rain events in future simulations, driving stronger evaporative cooling from the entrainment of drier midtropospheric air. This results in the formation of a stronger low-level cold pool, which enhances moisture convergence above the cold pool and increases rainfall rates during future heavy precipitation events. In addition, a warmer profile in future simulations might allow for heavier rainfall rates as a deeper atmospheric column can support additional collision-coalescence of liquid hydrometeors.

Is the intensification of precipitation extremes with global warming better detected at hourly than daily resolutions?

“…While future increases in daily precipitation extremes have been projected across parts of the U.S. in both the cold season [ Wang and Zhang , ] and the warm season [ Harding and Snyder , ], further projections from convection‐permitting scales capable of simulating extreme precipitation on subdaily timescales [ Kendon et al ., ; Fosser et al ., ] as well as the observed precipitation scaling [ Chan et al ., ] may elucidate future changes to subdaily precipitation extremes in a warming climate [ Prein et al ., ]. Such simulations across the U.S. may reveal increases in summer extremes on hourly timescales that we have failed to detect from direct observations.…”

Climatological representation of mesoscale convective systems in a dynamically downscaled climate simulation

“…To assure precision and comparability, a segmentation, classification, and tracking procedure is uniformly applied to observed (OBS), CTRL, and PGW composite reflectivity to detect QLCS and non‐QLCS events (Haberlie and Ashley, , ). Since QLCS produce multifaceted hazards and are an important part of the eastern CONUS hydroclimate (Houze, ; Harding and Snyder, ), these results may have far‐reaching implications for many aspects of society. In addition, the event‐identification machine learning technique described in this article could be modified for many different applications in climate science.…”

“…These changes may be caused, in part, by the modification of MCSs in a changing climate (Feng et al, 2016;Prein et al, 2017b). Changes in important meteorological factors that could influence future MCSs evolution include low-and mid-level specific humidity, instability (i.e., CAPE), the frequency of the Great Plains low-level jet, and cold pool development and strength (Harding and Snyder, 2015;Feng et al, 2016;Tang et al, 2017;Prein et al, 2017b). These factors may work in concert to generate MCSs that are larger, produce more rainfall, and exhibit faster forward propagation (Prein et al, 2017b), although the spatial pattern of these changes may vary (Rasmussen et al, 2017).…”

Improved Tolerance to Root Rot and Bacterial Blights in Kidney Bean: Registration of ‘Talon’ Dark Red Kidney and ‘Rosie’ Light Red Kidney

“…Under conditions of high disease pressure, pods and seeds are also affected, resulting in further losses due to seed quality. Climate change forecasts are predicting a significant increase in rainfall activity (especially thunderstorms) in the central United States during the summer months for the next 20 yr (Harding and Snyder, 2015). This may have a direct impact in the amount of disease pressure expected in bean production in these regions.…”