Statistical characteristics of heat wave precursors in China and model prediction

Among 87 events of regional dry heat wave (HW) in China during 1979-2008, precursors can be found from 83 regional dry HW events by the 250hPa regional-scale geopotential height anomalies. These height anomalies move westward in the low latitudes and eastward in the middle latitudes, with an average lead of 7 days before HW events occurred. 19% of the precursors for regional dry HW in southern China originate in the northwest Pacific, 4. 6 clays in advance of the HW on average, while most of the precursors (81%) start from Europe to Northwest China with a lead of 2-15 days, then propagate in the middle latitudes to 100-110 degrees E and 40 degrees N. Precursors for all of the northern China heat waves start from Europe. When the height anomaly reached 120gpm at 250hPa, the chance of regional dry HW events is 41%. With lower HW standards, the accurate rate of predicting HW events with height anomaly will rise accordingly. From the analysis of widespread-prolonged HW occurred in 2003 summer in southern China and based on physical decomposed ECMWF forecast data at 500hPa, the positive height anomaly to indicate the HW on 30 July 2003 can be predicted 1-7 days ahead.