Response of climate change in Hedong sandy area of Ningxia to global warming

By use of correlation between the drought-waterlogging grade index of Ningxia in recent 500 years/the tree ring index of Helan Mountain area and the yearly precipitation in representotive stations of Hedong sand area/air temperature anomaly,the yearly precipitalion series of representative stations in sand area since 1981 and the air temperature anomaly series since 1916 were inversed,and the response of climate change in Hedong sand area to globle warming was analysed.Results show that,the low frequency features of the drought-flood cycle in last 500a is relatively clear,among them,that of the 250a is the most significant following with 60a and 30a.From the middle of 1930s to the middle of 1950s there is a typical warm-wet time that is consistent with the average state of the whole country,but the duration is longer than the average for about 10a.Since then,the temperature dropped and the rainfall kept above normal,that means a typical cold-wet period,and it lasted until the end of 1960s following a relative cold-dry time,at that time it is similar to the average of the whole country.Up to now since the middle of 1980s,the temperature has been keeping high with less precipitation that is different from the situation of the whole country featured with more precipitation after 1990.The temperatures in the four seasons rise in fluctuation with different ranges,and all of them are higher than that of the average of whole China.The precipitations in the four seasons changed differently in fluctuation;there is a remarkable rise in summer and the most significant decline in autumn that is consistent with the trend of the whole country.