微波辐射计测量东莞地区的水汽特征初步分析

Preliminary Analysis of the Characteristics of Water Vapor in Dongguan Area Measured by Microwave Radiometers

利用微波辐射计测量得到的综合水汽含量(IWV),分析了东莞地区IWV的变化特征,初步探讨了IWV与地面风向、气温、降水量的关系,并根据地面湿度参量拟合出东莞地区IWV与地面水汽压的经验公式。研究表明:IWV月变化属于典型的单峰分布,4—10月为高值期其中8月最高,其余月份相对较低。IWV日变化不显著,变幅很小,其中夜间略呈下降趋势、白天则相反。东南、偏南和西南风时IWV平均值偏高;而偏北风和东北风影响下IWV则相对较低。降雨发生前IWV有一定的持续增长,对降雨的预报有一定的指示意义,但逐小时的IWV持续增长则不一定产生降雨。一般情况下,大的、强的降雨过程需要大的IWV,但大的IWV不一定能产生强的降雨。建立了用地面水汽压估算IWV线性经验公式。

Using the data of integrated water vapor ( IWV) content measured by microwave radiome-ters ,this work studies the variation of IWV in the Dongguan area and makes a preliminary discussion of the relationship between the IWV and surface wind direction, air temperature and rainfall amount, and fits an empirical formula between the local IWV and surface water vapor pressure based on the parameter of surface humidity. The result is shown as follows. The monthly variation of IWV showed a trend of first ascending and then descending and the IWV increased from March, and decreased from October, both rapidly. Its values were high from April to October but low in the rest of the year, which was a typical unimodal distribution. For the diurnal variation, it is both small and insignificant, with the night showing a decreasing trend and the day an increasing trend. The average IWV is high with the southeasterly, southerly and southwesterly winds but low with the northerly and northeasterly. On long-time scales, the IWV varies with the temperature con-sistently but it correlates less or even negatively with it on short-time scales. Before the rain, the IWV kept increasing, indicative in the forecasting of rain. Constant increases of hourly IWV did not foretell the rain necessarily. Under general circumstances, extensive and intense rains require a large IWV but a large IWV does not necessarily produce intense rains, and a low IWV may also result in large rains. The surface water vapor pressure was used to set up a linear empirical formula for estimating IWV.