Sensitivity of diurnal variation in simulated precipitation during East Asian summer monsoon to cumulus parameterization schemes

Abstract

The capability to simulate the diurnal variation of precipitation over East Asia region during the summertime of 2011 is investigated using five different cumulus parameterization schemes with the Weather Research and Forecasting model. A semidiurnal cycle with a 12 h interval over land and a diurnal cycle with a 24 h interval over ocean are commonly found in all simulations, consistent with the observed diurnal cycle. Two observed dominant peaks in the early morning and afternoon are reproduced in all simulations. With overestimated precipitation rate, however, the simulated afternoon peaks occur earlier than the observed peaks by 2 h for the Kain‐Fritsch (KF) and Simplified Arakawa‐Schubert schemes, and by 3 h for the Betts‐Miller‐Janjić and Tiedtke schemes. The overestimation of simulated precipitation frequency leads to amplitude and phase errors in the precipitation rate, and the early peak time of simulated precipitation intensity intensifies the phase error in the simulation over land. The KF scheme with alternative trigger function (KFtr) based on moisture advection provides slightly better results in terms of alleviating the overestimated precipitation rate and frequency and delaying the afternoon peaks. Additional sensitivity simulations based on the change of temperature perturbation in the trigger function of the KF and KFtr schemes demonstrate the afternoon peak tends to be delayed as temperature perturbation decreases, implying the significant role of convective initiation frequency in determining diurnal peaks of precipitation. Modulation of temperature perturbation alleviates the precipitation frequency bias, while it could not resolve the precipitation intensity bias.

Projected effects of 1.5 °C and 2 °C global warming levels on the intra-seasonal rainfall characteristics over the Greater Horn of Africa

“…It must be noted that climate models are known to overestimate the number of rainy days of low intensity. This overestimation is attributed to phase errors of rainfall amount, and the peak time of the simulated rainfall intensity, as reported by Choi et al (2015), Prein et al (2015), Salih et al (2018) and Otieno et al (2019). Therefore, the results from this study on the intra-seasonal rainfall characteristics are interpreted with this information in mind.…”

Precipitation Dynamical Downscaling Over the Great Plains

“…The closure assumption and trigger function adopted in cumulus schemes were reported to play a key role in dictating diurnal variation of precipitation (Choi et al, ; Qiao & Liang, ; Xie & Zhang, ; Zhang, ). Those closure assumptions and trigger functions that couple moist convection too strongly with boundary layer thermodynamic forcing and too weakly with large‐scale forcing are likely to fail to accurately predict the observed nocturnal precipitation maxima over the Great Plains (Liang et al, ; Qiao & Liang, ; Xie & Zhang, ).…”

“…However, in general, there exist large uncertainties with dynamic downscaling. RCMs have been found to be sensitive to spatial resolution (Lee et al, ; Tripathi & Dominguez, ; Yamada et al, ), nudging strategies (Bowden et al, ; Bullock et al, ; Harkey & Holloway, ; Liu et al, ; Miguez‐Macho et al, ; Omrani et al, ; Otte et al, ; Spero et al, ; Wang & Kotamarthi, ), model reinitialization frequency (Lo et al, ; Pan et al, ; Qian et al, ), and physics parameterizations such as cumulus schemes (Choi et al, ; Gochis et al, ; Liang et al, ; Pohl et al, ; Qiao & Liang, ) and land surface models (Bukovsky & Karoly, ; Chen et al, ; Vidale et al, ). Given these uncertainties, confidence in RCM‐downscaled projections of future climate can only be achieved when the credibility of RCM downscaling of historical climate has been proven (Gutowski et al, ; Harding & Snyder, ; Kendon et al, ; Liang et al, ; Mearns et al, ; Wehner, ; Xue et al, ).…”

Effects of the Convective Triggering Process in a Cumulus Parameterization Scheme on the Diurnal Variation of Precipitation over East Asia

“…Non-convective precipitation exhibits a diurnal cycle with an early morning peak at 0500-0600 LST, but its contribution to total precipitation is too small to produce the morning peak in total precipitation. Note that the ratio of convective to total precipitation in the simulation with the SAS convection scheme is higher than those with other cumulus parameterization schemes [4].…”

“…Because the diurnal variation of precipitation involves many coupled physical processes such as surface exchange, turbulence, and convection and cloud-radiation interactions [2], the deficiencies of the model in reproducing the diurnal variation of precipitation are mainly attributed to uncertain and incomplete parameterization of physical processes and their interactions. Previous modeling studies have indicated a high sensitivity of the simulation of the diurnal variation of precipitation over land especially to cumulus parameterization schemes in terms of both phase and amplitude (e.g., [3][4][5]). By performing a series of physics sensitivity experiments, Koo and Hong (2010) [3] showed that the phase appears to be modulated by moist convective processes, while the amplitude is more strongly controlled by boundary layer processes.…”