甘肃河东早春旱和春旱的监测与预测

The monitoring and forecasting for early spring drought and spring drought in Hedong region in Gansu province

利用1958年以来甘肃河东地区具有代表性的12个站点的降水和蒸发资料,给出了甘肃省早春旱和春旱指数计算公式和判别标准。结果表明:此法能够较准确地提炼出早春旱和春旱与多雨的年份,而且资料获取相对容易,在实时业务的干旱监测中有一定的应用价值。对46a来干旱的时空分布特征进行了初步分析,给出典型年份前期和当时场的风场和高度场的环流特征,指出从隆冬开始,北风异常就贯穿我国中西部上空的整个对流层;随着高度的升高,东亚高度场减弱并向西倾斜,东亚槽偏强,欧洲脊偏强,高低空环流的这种配制以及东西方向的波列分布状况不利于河东地区的降水,易造成干旱,并就此给出一个预测模型。

Using the precipitation and evaporation data for 12 representative stations in Hedong region in Gansu province during 1958 to 2003, this paper gives the numeration expressions and estimation criterion for early spring drought index and spring drought index. It is indicated that these methods can be used for determining early spring drought years, spring drought years and rainy years easily, and are valuable for drought monitoring. By analyzing the spatio-temporal drought characters in 46 years, the paper presents the circumfluence characters of meridional wind and geopotential height. It is discovered that the anomaly of north wind runs through all convection layer over west China from mid-winter; with the increase of height, the geopotential height over east Asia tends to weaken and incline to the west, and the east Asia groove and the Europe ridge is relatively strong. The circumfluence condition and wavelet distribution is not beneficial to rainfall and cause drought easily in Hedong region in Gansu province. A forecast model for early spring drought and spring drought is proposed.