中国热浪前期信号及其模式预报

Statistical characteristics of heat wave precursors in China and model prediction

在中国1979—2008年发生的87场区域干热浪事件中有83场区域干热浪事件可以在250hPa层高度扰动场上追踪到前期信号.高度扰动信号的移动方向可分为低纬向西和中纬向东传播的两类,前期信号平均出现的时间为7天.中国南方热浪的前期信号,一部分(19%)来自低纬西北太平洋,平均提前4.6天,而大部分(81%)的前期信号来自欧洲和中国西北地区,可提前2—15天,这些信号沿中纬度自西向东移动到达100°E—110°E和40°N附近地区.中心位置发生在北方的区域干热浪事件,前期扰动信号都来自欧亚中高纬度.统计得到,250hPa层的高度扰动达到120gpm与地面出现区域干热浪相对应的次数占41%.降低区域干热浪的定义标准,高度扰动作为前期信号的正确率会得到提高.在分析2003年中国夏季江南—华南大范围持续热浪事件的基础上,用欧洲中期天气预报中心的模式产品,对这次热浪500hPa高度场做物理分解,结果发现模式对高度扰动的预报具有提前1—7天的预示能力.

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 days 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°E and 40°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.