两个30年气候平均值的差异及其对气候业务的影响

对陕西短期气候预测业务使用的39个气象站气候要素1971～2000年平均值与1961～1990年平均值进行比较，发现大部分地区年平均气温升高，晴天日数增加；年降水量、阴天日数、降水日数、年日照时数减少；年大风日数、沙尘暴日数、冰雹日数、雷暴日数减少等。把两个平均值放在长序列中分析，发现某些气象要素最近的气候平均值的差值在20世纪80～90年代期间的5～6个气候平均值每两个相邻平均值的差值中是最大的，说明陕西20世纪90年代气候较60年代干燥、温暖，且90年代气温高、降水少的特点十分突出。还对某些要素平均值改变对气候影响评价、气候预测业务产生的影响进行简要分析。

Difference of Two 30-Year Averages and Its Influence on Operational Climatic Analysis

A comparison was made between the two 30-year climatic averages of meteorological elements from 1971 to 2000 and 1961 to 1990 from 39 meteorological stations used in Shaanxi climate prediction. The results show that the climate in the 1990s is drier and wormer than that in the 1960s in most areas, and some elements are especially obvious. Compared it with the 1961-1990 average, the 1971-2000 annual mean temperature and the days of sunny day increase, while the annual mean precipitation and the rainy days, overcast days, etc, decrease. The annual sunshine duration and the days of strong wind, sandstorm, and thunderstorm, etc, also decrease. For various long-range data series, the difference between the two averages is most obvious for the latest several (five to six) 30-year averages during the period from the 1920s to the 1990s. The difference of the two averages has certain impacts on the operation of climatic analysis and climatic prediction.