Multiscale Analysis of Interannual Variability of Summer Precipitation over Middle and Lower Reaches of Yangtze River
Based on observational data from meteorological stations of the China Meteorological Administration and the ERA5 reanalysis dataset provided by the European Centre for Medium-Range Weather Forecasts,this study conducted a quantitative diagnosis of precipitation rates using the scale separation method to explore the multi-scale characteristics of interannual variability of summer precipitation in the middle and lower reaches of the Yangtze River from 1980 to 2020.The results indicate that the precipitation variability in the region exhibited two dominant timescales,one with a synoptic period(less than 10 days)and the other with a subseasonal period(10-30 days and 30-60 days).By quantitatively diagnosing the interactions between background-scale(greater than 60 days),intraseasonal scale(30-60 days),quasi-biweekly-scale(10-30 days),and synoptic-scale(less than 10 days)variables,we found that summer precipitation in the middle and lower reaches of the Yangtze River was mainly determined by ambient water vapor,ambient wind,and synoptic-scale wind.Moreover,background circulation contributed the most in years with strong precipitation,while synoptic-scale disturbances contributed more in years with weak precipitation.Further analysis of the two precipitation centers in the middle and lower reaches of the Yangtze River reveals that the average precipitation in the middle reaches was more dependent on synoptic-scale disturbances.In comparison,precipitation in the lower reaches was more dependent on background circulation.In years with strong precipitation in the middle reaches,the subtropical high in the Northwestern Pacific extended further westward and exhibited stronger intensity.There was also a significant difference between the two precipitation centers at the subseasonal scale,with the 30-60-day oscillation being more significant in the downstream areas,especially in years with stronger precipitation.
middle and lower reaches of the Yangtze Rivermultiscale diagnosisinterannual differencesregional differences
国家科技期刊平台
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