Improving diurnal rainfall phase over the Southern Great Plains in warm seasons by using a convective triggering design

Abstract

This study reports the improvements in the diurnal rainfall phase over the Southern Great Plains (SGP) with the Community Atmosphere Model by incorporating two convective initiation designs into the Zhang–Mcfarlane scheme. To capture the convection initiation of the nocturnal rainfall regime, the triggers emphasized the importance of suppression of convective inhibition and identification of elevated buoyancy for initiating convection. Consistent with the single‐column study of Wang et al. (2015), the model rainfall bias reduced with an increase in the heavy nocturnal rainfall and with the suppression of the spurious daytime convection in global domain experiments. We found that, with the climate model resolution of 1°, the nocturnal convection over the SGP can be well represented when the destabilization mechanisms of potentially buoyant layer at the low‐level troposphere is appropriately captured. Such destabilization is caused by the moisture convergence between the Rocky Mountains–SGP circulations and the uplifted low‐level jets from the Gulf of Mexico. Similar improvements are also found in other regions on the lee side of high terrains, such as the Tibetan Plateau.

Performance of the Taiwan Earth System Model in Simulating Climate Variability Compared With Observations and CMIP6 Model Simulations

“…While detailed sensitivity experiments are needed to understand the cause, we think the improvements in rainfall are very likely to be from better rainfall characteristics due to convective trigger scheme and the better surface radiative heating due to the inclusion of radiative effects of 3D topography over the East Asia region. Previous studies show these two schemes can improve intensity and distribution of land convection (Lee et al, 2013;Wang & Hsu, 2019), which is consistent with improvements of land rainfall in TaiESM1 (e.g., Figure S4). In terms of the climate variability of ENSO, decadal variability, and teleconnection, we think the improvements are likely due to changes of moisture-cloud relationship and cloud radiative properties from GTS macrophysics scheme and convection behaviors of convective trigger scheme, through atmosphere-ocean interactions.…”

“…For AMO, they are 1.12 and 0.74 for CESM1/CMIP5, and 1.36 and 0.72 for TaiESM1. Figure S6a C. Wang &Hsu, 2019), which is consistent with improvements of land rainfall in TaiESM1 (e.g. Fig.…”

“…This improvement result is also reported by Lee, Wang, et al. (2020) and can be attributed to the improvements in the convective trigger function designs in TaiESM1 (Wang & Hsu, 2019). Figure 11c presents the performance of the CMIP6 model compared with TMPA observations based on the pattern correlation for the diurnal rainfall phase and amplitude.…”

“…However, unlike other models, TaiESM1 exhibits improved representations of the propagation behavior in the diurnal peak phase over many topographical regions and coastal regions, including the Southern Great Plains and the coastal regions of the maritime continent. This improvement result is also reported by Lee, Wang, et al (2020) and can be attributed to the improvements in the convective trigger function designs in TaiESM1 (Wang & Hsu, 2019). Figure 11c presents the performance of the CMIP6 model compared with TMPA observations based on the pattern correlation for the diurnal rainfall phase and amplitude.…”

Taiwan Earth System Model Version 1: Description and Evaluation of Mean State

“…This result is consistent with the single-column model tests of , indicating that their proposed convective trigger may be the cause of these improvements. Furthermore, Wang and Hsu (2019) demonstrate that the improvement of nocturnal rainfall over SGP is mainly from the https://doi.org/10.5194/gmd-2019-377 Preprint. Discussion started: 31 January 2020 c Author(s) 2020.…”