Forecasting of Warm Season Heavy Precipitation over Continental China at Convection-Permitting Resolutions: Forecast Skills, Spatial Distribution, Propagation, and Diurnal Cycles of Precipitation (Invited Presentation)

Being located within the East Asian Summer Monsoon region, major river, lake, urban flooding disasters and land/mud slides caused by wide spread heavy precipitation and/or extreme local rainfall occur every year in different parts of China. Due to the very large difference in terrain elevations between the western and eastern parts of the country, China is especially prone to major river flooding; annual financial losses caused by flooding are estimated at 120 billion RMB Yuan (about $18 billion).

Warm-season quantitative precipitation forecasting (QPF) has always been a challenge, and it is especially so over china given the relatively weak synoptic forcing situations and highly complex terrain. As part of a five-year national project called “Observation, Prediction and Aanlysis of severe Convection of China (OPACC)” led by the first author, and as an effort to increase the collaborations between the operational and research communities within China, Nanjing University (NJU) has been producing experimental real-time 48-h forecasts at a 4 km convection-permitting resolution over continental China twice a day from June to August over the past five years, using a version of the WRF model. In this study, these forecasts are systematically evaluated, in terms of precipitation skill scores for different rainfall intensity thresholds, and of the model’s ability in accurately simulating the spatial distributions, propagation and diurnal cycles of precipitation, as well as inner-season movement of precipitation bands. Data from the national rain gauge network of over 20,000 stations are used for the evaluation. Certain precipitation mechanisms including diurnal peaks and heavy precipitation along coast lines are examined and explanations offered. Examples of extreme local precipitation events will also be presented together with the meteorological conditions in which they occur.