摘要
根据Holzworth干绝热曲线法求最大混合层厚度的基本原理 ,提出了两种计算最大混合层厚度的方法———求解二元一次方程组法和逐步逼近法。利用此方法和兰州市气象站1 988～ 1 992年逐日的气象观测资料 ,计算并分析了兰州市城区最大混合层厚度的时间变化特征 ,其月平均值的年变化呈单周期型 ,即 1 2月最低 ( 71 6m) ,5月份最高 ( 2 0 74m) ;旬平均值的年变化趋势基本上与月平均值的年变化一致 ,只是在 4月下旬和 6月下旬分别出现两个峰值。冬季兰州地区处于不同天气系统控制时 ,其最大混合层厚度也有一定变化 ,其中冷锋过境前平均最大混合层厚度最低 ( 735m) ;冷锋过境后受蒙古高压前部控制时 ,平均最大混合层厚度最高为 ( 946m)。兰州城区SO2 、CO和NOX 三种污染物月平均浓度值的年变化也呈单周期型 ,但与月平均最大混合层厚度年变化曲线的位相几乎相反 ,即 1 2月份的浓度峰值对应平均最大混合层厚度的谷值 ,呈显著的反相关关系 ;其旬平均值的相关系数分别为 - 0 .774、- 0 .82 7和 - 0 .743,这表明最大混合层厚度是影响城市空气污染的重要因素。
According to the fundamentals of estimating maximum mixing depths(MMD's) by the assumption of a dry adiabatic lapse rate, two methods of calculating MMD's, that is, a method of solving dual linear equation groups and a method of stepwise approach, have been presented. By using the latter and the everyday meteorological data from Meteorological Observing Station of Lanzhou during 1988～1992, the MMD's in Lanzhou Proper were calculated and their variable characteristics with time were analysed. The results were as follows: Annual variation of monthly mean MMD's accorded with a single cycle pattern, that is, the minimum value(716 m) of monthly mean MMD's occurred in December but the maximum value(2 074 m) of them occurred in May. An annual variable tendency of ten day mean MMD's almost corresponded with that of monthly mean MMD's except two peak values occurring in the last ten days of April and June respectively. In addition, the MMD's in Lanzhou Proper varied with different synoptic systems. The mean MMD was minimum (735 m)before cold front passage. But it was maximum (946 m) when Lanzhou Proper was controlled by the front of a high pressure system after cold front passage. Annual variations of monthly mean concentrations of SO 2, CO and NO X were also single cycle pattern separately. But their phases were almost contrary to that of annual variation curve of monthly mean MMD's, that is, the three air pollutants were all corresponding to the minimum value of monthly mean MMD's in December. The correlation coefficents between the ten day mean concentrations of SO 2, CO, NO X and the monthly mean MMD's were -0.774, -0.827 and -0.743, respectively. These showed that their negative correlations were remarkable. In other words, the MMD's were a primary factor affecting air pollution in Lanzhou Proper.
出处
《高原气象》
CSCD
北大核心
2000年第3期363-370,共8页
Plateau Meteorology
基金
国家自然科学基金!( 498750 0 4 )
中国科学院重大项目!(KZ951 A1 4 0 3 2 )
高等学校骨干教师资助计划项目资助
