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干旱是延安地区主要灾害,尤以春旱严重,对大秋作物的播种、全苗威胁很大。据1951-70年气象资料,20年中,除1958、64年外,其余18年都发生了程度不同的干旱,其中春旱占56％。1962年3月上旬开始的春旱,长达110-140天。全地区310万亩早秋,其中70万亩缺苗率达50％以上,延安县春谷因干旱缺苗翻种的占40-60％,当年谷子亩产仅61.4斤,玉米113斤。造成春早的主要原因:春季降水量少,一般占全年降水量的13-19％,且不稳定;春季风大,四季中平均风速最高,加快了土壤水分的散失;春季增温快,增加了土壤水分的蒸发。抗旱的有利条件是:秋季降水量较多,年平均130-180毫米,占全年降水量
Drought is a major disaster in Yan’an, especially in the spring drought, the planting of big autumn crops, the whole plant a great threat. According to the meteorological data of 1951-70, in 20 years, with the exception of 1958 and 64, different degrees of drought have occurred in the remaining 18 years, of which spring drought accounts for 56%. Spring drought started in early March 1962, up to 110-140 days. 310 million mu of early autumn in the whole region, of which 70 million mu lack of seedlings rate of 50% or more, Yan’an Spring Valley due to arid seedlings planted 40-60%, then millet mu only 61.4 kg, 113 kg of corn. The main causes of spring early spring: less precipitation in spring, generally accounting for 13-19% of the annual precipitation, and instability; spring monsoon, the highest average wind speed in four seasons, speeding up the loss of soil moisture; warming in spring, Increased soil moisture evaporation. The favorable conditions for drought relief are: more precipitation in autumn with an average annual 130-180 mm, accounting for the annual precipitation