山西北部农业干旱的原因及防御对策

为了探究造成山西北部地区农业干旱的气象因子，以便有针对性地提出应对干旱措施，通过彭曼公式和玛格努斯经验公式确定影响蒸发量的主要气候因子，利用近50年的气象资料，采用线性趋势分析和多项式拟合对山西省北部地区春季及初夏阶段干旱的成因进行分析。结果表明：造成山西省北部地区干旱的根本原因是降水量与蒸发量之间的不平衡，降水的主要时段是发生在6-9月，而蒸发量的峰值却出现在4-7月，这种情况造成春季到初夏时段降水量与蒸发量失去平衡。另外，由于气温以0.33℃/10 a的速率升高，饱和差以0.17 hpa/10 a的频率递增，从而造成蒸发量的加大。日照时数对蒸发量的贡献一般，50年来蒸发量的上升率为5.06 mm/10 a，相同时段内的日照时数却呈现下降之势，速率-2.84 h/10 a。说明日照时数不是干旱出现的主要因子。山西北部地区干旱的影响因子与全国大部地区基本相同，但更接近北方地区。

Cause of Agricultural Drought and Defensive Countermeasures in the North Region of Shanxi Province

In order to explore the fundamental causes of leading to agricultural drought in the northern Shanxi Province and putting forward targeted measures for responding drought, the main climatic factors of affecting evaporation were proposed based on the Penman formulas and Magnus formulas. As well as, the cause of bringing about drought in spring and early summer in the northern Shanxi Province was analyzed based on the methods of the linear trend analysis and polynomial fitting with the meteorological data of the nearly 50 years. The results showed that the fundamental cause of leading to agricultural drought in the northern Shanxi Province was unbalanced between precipitation and evaporation. There were two reasons for the unbalance. On the one hand, the main period of precipitation was in between June and September, and the peak of evaporation appeared in between April and July. On the other hand, the air temperature rose at the rate of 0.33℃/10 a and the saturation deficit increased at the rate of 0.17 hpa/10 a, which directly led to the increase of evaporation. Sunshine duration made a little contribution to evaporation, for the increase rate of evaporation was 5.06 mm/10 a in 50 years and in the same period, the sunshine duration declined at the rate of-2.84 h/10 a, which showed that the sunshine duration was not the main fact of affecting drought. In short, the main climatic factors of affecting drought in the northern Shanxi Province were the same to the most areas of country, but nearly to the northern.