Changing Trends of Winter Temperature in Recent 53 Years in Ningxia and Impact for Agriculture

Based on winter (December to February) daily temperature data of 20 meteorological stations in Ningxia Hui Autonomous Region since 1961, the interannual and interdecadal change trend and the mutation characteristics of the winter average, the maximum, and the minimum temperature of the whole Ningxia region, the Yellow River irrigation area, the central arid zone and the southern mountainous area were analyzed using linear trend, Mann-Kendall test and other methods; Meanwhile,the new characteristics of average temperature of the coldest month, <0 ℃ negative accumulated temperature in winter of the 21^st century and impact on agriculture were comparatively analyzed. The results showed that: Firstly, in the whole region and different areas of Ningxia, winter average temperature rose significantly before 2000, the Yellow River irrigation area was the most obvious in winter warming than that in the central arid zone and the southern mountainous area. 1985 was the abrupt change point of winter average temperatures in most areas of Ningxia. In the early 21^st century the winter average temperature rose slowly in most areas of Ningxia, even falling in the central arid zone. Secondly, the rise of average minimum temperature was significantly higher than average temperature and average maximum temperature in the winter, indicating that the rise of winter temperature in Ningxia was mainly due to winter minimum temperature. Since the 21^st century, the average maximum temperature had changed more dramatically than the average temperature in the winter, dropping in most areas. Winter average minimum temperature in addition to the central arid zone declined slightly after 2002, and continued to rise in most areas of Ningxia.Thirdly, both rise of the average temperature of the coldest month and dramatic reduction of the absolute value of negative accumulated temperature is not only beneficial to the northern planting boundary of winter crops spreading further to north and planting areas expanding with a lower risk of freezing injury, but also beneficial to crop pests increase.