Climate Change Impacts and Adaptation Strategies in Northwest China

Climate change resulted in changes in crop growth duration and planting structure,northward movement of planting region,and more severe plant diseases and insect pests in Northwest China.It caused earlier seeding for spring crop,later seeding for autumn crop,accelerated crop growth,and reduced mortality for winter crop.To adapt to climate change,measures such as optimization of agricultural arrangement,adjustment of planting structure,expansion of thermophilic crops,and development of water-saving agriculture have been taken.Damaging consequences of imbalance between grassland and livestock were enhanced.The deterioration trend of grassland was intensified;both grass quantity and quality declined.With overgrazing,proportions of inferior grass,weeds and poisonous weeds increased in plateau pastoral areas.Returning farmland to grazing,returning grazing to grassland,fence enclosure and artificial grassland construction have been implemented to restore the grassland vegetation,to increase the grassland coverage,to reasonably control the livestock carrying capacity,to prevent overgrazing,to keep balance between grassland and livestock,and to develop the ecological animal husbandry.In Northwest China,because the amount of regional water resources had an overall decreasing trend,there was a continuous expansion in the regional land desertification,and soil erosion was very serious.A series of measures,such as development of artificial precipitation(snow),water resources control,regional water diversion,water storage project and so on,were used effectively to respond to water deficit.It had played a certain role in controlling soil erosion by natural forest protection and returning farmland to forest and grassland.In the early21st century,noticeable achievements had been made in prevention and control of desertification in Northwest China.The regional ecological environment has been improved obviously,and the desertification trend has shown sign of under control.

The Variation Rule and Anomaly Features of the Available Precipitation in the Growth Period of Crops in the Middle and Southern Part of Ningxia

[ Objective] The aim was to study the available precipitation and its abnormal characteristics during the growth period of crops in the mid- dle and southern part of Ningxia. [ Methed] Through Takahashi＇s evaporation equation, linear trend analysis, Mann -Kendall, Lepage, wavelet analysis, the characteristics of available precipitation and its abnormal characteristics during its growth period in Ningxia were analyzed based on monthly precipitation （March- September）, temperature, and NCAR/NCEP reanalysis data in 9 observation stations from 1961 to 2010. E Result l In recent 50 years, the available precipitation during the growth period of crops in central drought area and south hilly area varied a lot, more in the south and less in the north. The available precipitation in these two areas was reducing and varied a lot in different ages. The available precipitation was less in the middle drought region after 1970s and in the southern hilly region after 1990s and the available precipitation in middle drought area changed significantly. The available precipitation in the two areas appeared in July, August, and September, above 76% of general growth period, while that in March, April and May was 14% lower than that in growth period. No abrupt changes in central drought area and south hilly area. There were the periods of 5 -7 a and 2 -3 a oscillations in the middle drought region, 2 -3 a and 10 -12 a oscillations in the southern hilly region. There were negative anomaly field at 500hPa height in high-precipitation years between the Baikal and the China＇s northwestern, and there were positive anomaly field in low-precipitation years. [ Cenclusion] The study provided reference for the reasonable utilization of available water resources in cen- tral and south Ningxia.

Analysis on Spatial and Temporal Changes of Extreme Precipitation Events in Ningxia in Recent 50 Years

[ Objective] The aim was to study the spatial and temporal changes of extreme precipitation events in Ningxia in recent 50 years. [ Method] Using dally precipitation data at 20 stations in Ningxia from 1961 to 2010, and defining the threshold value of extreme precipitation in each sta- tion by percentage method, choosing indicators such as precipitation, frequency and intensity of extreme precipitation events, the characteristics of the spatial and temporal distribution and linear trend of extreme precipitation events in Ningxia were analyzed based on linear regression and M-K non-parameter statistical test method. [ Result] The percentage method suggested the threshold value of average extreme precipitation in Ningxia in recent 50 years decreased from south to north. The large threshold value was in southern Haiyuan, Tongxin and northern Yancheng, which was similar to the distribution of mean annual precipitation in Ningxia. In recent 50 years, extreme precipitation frequency and extreme precipitation de- creased in most part of Ningxia but the intensity tended to strengthen. Study of extreme precipitation in Mahuang Mountain and Liupan Mountain in- dicated that precipitation frequency, intensity and extreme precipitation reduced. Annual extreme precipitation frequency narrowed and then in- creased after 1994 and had mutation in 2003. Annual extreme precipitation intensity enhanced since 1984. Mutation took place in 1984. Intensity in Liupan Mountain had weakened since 1978. [ Conclusion] The study provided theoretical basis for the mutation of climate in Ningxia.

Seasonal Difference of the Spatio-Temporal Variation of Precipitable Water Vapor in China

This study analyzes the spatial and temporal distribution characteristics of seasonal precipitable water vapor (PWV) in China between 1979 and 2008. To achieve this, the observed temperature dew point difference and atmospheric pressure at various altitudes of 102 radiosonde stations were utilized. The analysis involved calculating and examining the PWV variations across the different seasons in the study period. The results are illustrated as follows: 1) The annual mean and seasonal mean PWV over China is characterized by decreasing from southeast to northwest. The PWV has obvious seasonal features. It is the least in winter, which is mainly affected by latitude and altitude, and the most in summer, which is mainly affected by the monsoon. It is the medium in spring and autumn, with more in autumn than in spring. 2) The spatial distribution pattern of four seasonal PWV is approximately opposite to its variation coefficient distribution pattern, that is, the monsoon (non-monsoon) areas with more (less) PWV have a smaller (larger) variation amplitude. 3) The distribution pattern of four seasonal PWV shows a consistent distribution pattern in the whole region and the winter characteristics are the most significant. The abnormal variation of PWV shows consistent interdecadal oscillation, and it exhibits an obvious phase transition around 2002 when the PWV has an increasing shift in winter, spring, and summer, while it is more complicated in autumn.

宁夏年降水和季节降水的创新趋势分析

采用创新趋势分析(ITA)方法对1961年至2018年宁夏不同强度降水的时空变化进行研究。结果表明,区域年降水量增加主要是弱降水增加,而区域年降水量减少主要是强降水减少;极端降水的变化趋势明显。不同类型极端降水的贡献随季节变化。春季区域降水增加主要是强降水增加,区域降水减少主要是弱降水减少。夏季和秋季区域降水增加主要是弱降水增加,而区域降水减少是由强降水减少引起。该研究结果为水资源规划和应对干旱和洪涝灾害提供了支持。