Variations of Frost-free Period and Its Impact on Grain Yields in Henan Province during 1961-2013

The aim of this study was to investigate the responses of frost dates to global warming and its influences on grain yields. In this study, based on the frost date series defined by daily minimum ground temperature, the spatial and temporal characteristics of first frost date （FFD）, last frost date （LFD） and frost-free period （FFP） were analyzed. The impact of extending FFP on major crop yields was also studied. The results were as follows： FFD showed a significantly delaying trend of 2.2 d/10 y, and LFD presented an advancing trend of 2.4 d/10 y. FFP extended at a rate of 4.5 d/10 y due to the later FFD and earlier LFD. The most obvious trend of FFD was in westem Henan, while the most significant trend of LFD and FFP oc- curred in south central parts of the study area. However, in eestem region, the trends of FFD, LFD and FFP were not so obvious. Major crop yield showed a sig- nificant correlation with frost-free period for Henan during 1961-2013. The yields of grain, rice, wheat, and maize increased by 79.5, 90.0, 79.5 and 70.5 kg/hm2 with FFP extending by one day.

1961—2013年黄河三角洲气候变化趋势研究

利用黄河三角洲地区11个气象站点1961—2013年间的气候数据,对该地区近53 a来的气候变化趋势及其特征进行了分析。结果表明:黄河三角洲地区气温整体呈上升趋势,气温倾向率为0.3℃/10 a;降水量、蒸发量、风速、相对湿度均呈波动减少趋势,气候倾向率分别为-12.6 mm/10 a、-69.4 mm/10 a、(-0.26 m/s)/10 a、-0.58%/10 a;黄河三角洲地区在20世纪60—70年代表现出明显的冷湿特征,80年代表现出过渡性的气候特征,90年代以来气候表现出明显的暖干特征;四季气温均呈波动上升趋势,其中冬季气温升幅最大,为0.34℃/10 a,夏季气温升温幅度最小;降水量在春季呈增加趋势,增加速率为0.54 mm/10 a,其他季节呈下降趋势,夏季下降最多;各季节蒸发量、风速和相对湿度均呈波动下降趋势;黄河三角洲地区6—8月气温高、降水丰富、蒸发旺盛、相对湿度大,风速较小。

1961—2013年辽宁省夏季降水时空变化分布特征分析

利用1961—2013年辽宁省25个台站逐时降水资料,分析了辽宁省夏季降水时数、强度以及极端强降水时数、强度的空间分布特点及变化趋势。结果表明:辽宁省夏季平均降水时数呈减少趋势,但降水强度呈增加趋势;夏季平均极端强降水时数和降水强度均呈增加趋势,尤其在汛期7月极端强降水强度增加趋势明显。极端降水事件的增多,会导致由其引起的灾害性事件的增多,因此研究辽宁省夏季降水时空变化分布特征,对汛期强降水集中地区的防灾减灾工作具有十分重要的意义。