Abstract:

Based on the hourly precipitation data and the fifth-generation European Center for Medium-Range Weather Forecasts(ECMWF) atmospheric reanalysis(ERA5) data in Beijing-Tianjin-Hebei region in the warm season (June-September) from 2013 to 2021, the temporal and spatial characteristics were statistically analyzed. The evolution characteristics of environmental factors such as dynamic, water vapor, and thermal instability conditions of different synoptic patterns were compared and analyzed. The results show that the Subtropical High (SH) pattern and the Cold Vortex (CV) pattern are the main types of short-duration heavy rainfall, accounting for 55%. The short-duration heavy rainfall mainly occurs from the middle and late July to the early and middle August and concentrates from the afternoon to the midnight.Comparably, the rain distribution differences are obvious.Pattern parting is reasonable.Mostly for low-level convergence and high-level divergence, the Southwest Vortex (SV) pattern are the most prominent, and increase with approaching precipitation, while the Weak Weather (WW) pattern is the smallest in all stages. The water vapor of the SH pattern, the Typhoon Wind (TW) pattern and the SV pattern are the most abundant, median specific humidity on 925 hPa is 19.14 g·kg^-1 for SH pattern. The SV pattern has the highest saturation in high and low layers, and the average of median relative humidity reaches 87% in low layers. The WW pattern is relatively low of 74%. The precipitable water vapor of almost all patterns increases with the approaching precipitation. The thermal instability of the WW patter is the strongest, and the median temperature difference on 825 hPa and 500 hPa reaches 25.74℃, while the SV pattern is the weakest. The thermal condition of each type weakens over time except for the WW pattern.

Key words: Short-duration heavy rainfall, Typing, Environmental conditions