Sensitivity of U.S. summer precipitation to model resolution and convective parameterizations across gray zone resolutions

Abstract

Simulating summer precipitation is a significant challenge for climate models that rely on cumulus parameterizations to represent moist convection processes. Motivated by recent advances in computing that support very high‐resolution modeling, this study aims to systematically evaluate the effects of model resolution and convective parameterizations across the gray zone resolutions. Simulations using the Weather Research and Forecasting model were conducted at grid spacings of 36 km, 12 km, and 4 km for two summers over the conterminous U.S. The convection‐permitting simulations at 4 km grid spacing are most skillful in reproducing the observed precipitation spatial distributions and diurnal variability. Notable differences are found between simulations with the traditional Kain‐Fritsch (KF) and the scale‐aware Grell‐Freitas (GF) convection schemes, with the latter more skillful in capturing the nocturnal timing in the Great Plains and North American monsoon regions. The GF scheme also simulates a smoother transition from convective to large‐scale precipitation as resolution increases, resulting in reduced sensitivity to model resolution compared to the KF scheme. Nonhydrostatic dynamics has a positive impact on precipitation over complex terrain even at 12 km and 36 km grid spacings. With nudging of the winds toward observations, we show that the conspicuous warm biases in the Southern Great Plains are related to precipitation biases induced by large‐scale circulation biases, which are insensitive to model resolution. Overall, notable improvements in simulating summer rainfall and its diurnal variability through convection‐permitting modeling and scale‐aware parameterizations suggest promising venues for improving climate simulations of water cycle processes.

The Importance of Soil‐Type Contrast in Modulating August Precipitation Distribution Near the Edwards Plateau and Balcones Escarpment in Texas

“…Accurate downscaling of summer precipitation remains a great challenge for most mesoscale models (Gao et al, ; Liang et al, ; Qiao & Liang, ), even at convection‐allowing resolutions (Sun et al, ). Our previous dynamic downscaling of precipitation over the Great Plains for the past climate with the WRF model significantly underestimated warm‐season precipitation over the Southern Great Plains and shifted the band of maximum precipitation to the Rockies and Nebraska (Sun et al, ); in most cases, the rainband was shifted northwestward, regardless of convection‐allowing or convection‐parameterizing configurations.…”

“…Accurate downscaling of summer precipitation remains a great challenge for most mesoscale models (Gao et al, 2017;Liang et al, 2006;Qiao & Liang, 2015), even at convection-allowing resolutions (Sun et al, 2016).…”

Exploring the convective grey zone with regional simulations of a cold air outbreak

“…These studies over land and another over the tropical Pacific (Holloway et al , 2012) concluded that the highest resolution simulations with convection explicitly resolved agreed best with observations. Similarly, Gao et al (2017) report improved representation of precipitation spatial distribution and timing in higher resolution (4 km when compared to 12 and 36 km). These results suggest that, at least for deep convection, we should expect better comparison to observations at higher resolution.…”

Impact of Atmospheric Rivers on Surface Hydrological Processes in Western U.S. Watersheds

“…Previous studies have mostly been conducted to either focus on fine spatial resolution over short durations or long duration at a coarse resolution (Chen & Hossain, ; Hu et al, ; Leung & Qian, ). With advances in computing resources, convection permitting climate simulations at grid spacing of a few kilometers are becoming feasible and recent studies have demonstrated their usefulness for simulating cold season orographic precipitation and snowpack dynamics (Rasmussen et al, ) and extreme precipitation (Liu et al, ; Prein et al, ) as well as warm season precipitation and its diurnal variability (Gao et al, ; Prein et al, ; Yang et al, ). Overcoming the limitations of both model resolution and simulation period opens the door to improving analysis of AR events on climate time scale.…”