Forecasts of the Warm-Sector Heavy Rainfall With a Warm Shear Pattern Over Coastal Areas of the Yangtze–Huaihe River in a Regional Business Forecast Model

Abstract

Based on the observational hourly precipitation data and the ERA5 reanalysis datasets, the short-term forecasts of the warm-sector heavy rainfall with warm-type shear line (WRWS) events over the coastal areas of the Yangtze–Huaihe River (YHR) are investigated in the regional business model Precision Weather Analysis and Forecasting System (PWAFS). Evaluations and diagnoses are carried out via objective estimations and composition analyses for the rainy season of 2017. Results show that the short-term forecasts of PWAFS are characterized by considerable skills for WRWS events in the coastal areas of YHR in view of the object-based diagnostic evaluation, which, however, tend to generate the rain belts with northeast shift phases and weaker intensities. Meantime, the threat score results for WRWS-associated processes show that the model forecasting skill declines sharply as the precipitation intensity increases. Moreover, composition differences of the synoptic-scale thermodynamic characteristics between observations and forecast results are diagnosed to reveal the possible mechanisms of the short-term forecast biases toward WRWS. The zonal westerlies are overestimated in the model, while the southerlies are underestimated in the lower troposphere over coastal areas of YHR, leading to the northeastward shifted shear line and the absent moisture channel associated with the East China Sea at the boundary layer. Attributed to these atmospheric circulation biases, the accumulated warm and moist energy is weaker at the boundary layer, and hence, the short-term forecasts of the rain-belt location for WRWS over the YHR coastal areas have northeast shifting phases with weaker intensities of precipitation in forecasts of the regional business model PWAFS.

Diagnosis of Warm-Sector Heavy Rainfall with Warm Shear in the Yangtze–Huaihe Coastal Areas from the Perspective of Moist Static Energy

“…The selection criteria for WSWR below were employed in this study based on the concept of WR [1] and the shear line [36][37][38]:…”

Trend Analysis and Projection of Climate Variables Using the LARS-WG Model in Coastal Areas of China

“…This uncertainty arises from variations in study approaches, such as the use of different climate models and climatic scenarios (Qin et al, 2023). Despite ongoing research, there are still uncertainties surrounding the anticipated long-term alterations in air temperature and precipitation within specific regions of China, including the Shandong Plain and Huaibei Plain, under future climate scenarios (Wang et al, 2023a;Wang et al, 2016;Wu et al, 2023;Yan et al, 2021;Zhang et al, 2022). The vulnerability of these regions to climate change is magnified by the intricate interaction of land-ocean-atmosphere dynamics, which is particularly pronounced due to their geographical location in the coastal regions of China (Wang et al, 2021;Yan et al, 2023).…”