TY - JOUR
T1 - Evaluation and Error Source Analysis of Convection-Permitting Forecasts for Localized Nocturnal Rainfall Over a Complex Mountainous Region in Pearl River Delta, South China
AU - Rao, Xiaona
AU - Zhu, Kefeng
AU - Zhao, Kun
AU - Chen, Xingchao
AU - Hu, Sheng
AU - Liu, Xiantong
AU - Zhou, Ang
N1 - Publisher Copyright:
© 2023. American Geophysical Union. All Rights Reserved.
PY - 2023/11/16
Y1 - 2023/11/16
N2 - The concave mountainous area of Pearl River Delta (PRD) is a summer rainfall hotspot of South China due to the presence of warm-moist monsoon flow and complex orography. This study evaluated the performance of a convection-permitting Weather Research and Forecasting (WRF) model in forecasting nocturnal rainfall in this area, focusing on days with low level southwesterly winds during the summers of 2013–2015. Results showed that the nocturnal rainfall exhibited two centers, one located along the large-scale northern mountains and the other along the small-scale Huadu Hill. WRF demonstrated superior performance in predicting rainfall over the northern mountainous region. In contrast, WRF significantly underestimated nocturnal rainfall both near local Huadu Hill and in the foothill area of northern mountains, which were strongly influenced by local forcings. Using high-resolution analyses from Variational Doppler Radar Analysis System (VDRAS) and Automatic Weather Stations observations, we firstly identified the sources of forecast errors in triggering a typical localized nocturnal convection. Results revealed that WRF severely underestimated thermal contrast between the Guangdong-Hong Kong-Macao Greater Bay Area urban agglomeration and the concave mountains, leading to the absence of the northeastern/northern inflows toward the cities. Consequently, low level convergence and updrafts near the convection initiation position were too weak to lift air parcels above the severely overestimated level of free convection, thereby failing to trigger the convection. VDRAS-based sensitivity experiments, with a specific focus on assimilating surface temperature, validated the crucial role of urban-mountain thermal contrast on local winds that triggered the nocturnal convection.
AB - The concave mountainous area of Pearl River Delta (PRD) is a summer rainfall hotspot of South China due to the presence of warm-moist monsoon flow and complex orography. This study evaluated the performance of a convection-permitting Weather Research and Forecasting (WRF) model in forecasting nocturnal rainfall in this area, focusing on days with low level southwesterly winds during the summers of 2013–2015. Results showed that the nocturnal rainfall exhibited two centers, one located along the large-scale northern mountains and the other along the small-scale Huadu Hill. WRF demonstrated superior performance in predicting rainfall over the northern mountainous region. In contrast, WRF significantly underestimated nocturnal rainfall both near local Huadu Hill and in the foothill area of northern mountains, which were strongly influenced by local forcings. Using high-resolution analyses from Variational Doppler Radar Analysis System (VDRAS) and Automatic Weather Stations observations, we firstly identified the sources of forecast errors in triggering a typical localized nocturnal convection. Results revealed that WRF severely underestimated thermal contrast between the Guangdong-Hong Kong-Macao Greater Bay Area urban agglomeration and the concave mountains, leading to the absence of the northeastern/northern inflows toward the cities. Consequently, low level convergence and updrafts near the convection initiation position were too weak to lift air parcels above the severely overestimated level of free convection, thereby failing to trigger the convection. VDRAS-based sensitivity experiments, with a specific focus on assimilating surface temperature, validated the crucial role of urban-mountain thermal contrast on local winds that triggered the nocturnal convection.
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U2 - 10.1029/2023JD039065
DO - 10.1029/2023JD039065
M3 - Article
AN - SCOPUS:85175372210
SN - 2169-897X
VL - 128
JO - Journal of Geophysical Research: Atmospheres
JF - Journal of Geophysical Research: Atmospheres
IS - 21
M1 - e2023JD039065
ER -