北京地区风沙活动的现状

根据1949-1984年的降水和蒸发资料,本文分析北京地区风沙活动的气候原因,阐明风沙活动的现状和特点,并提出用扬沙能力表示风沙活动的强度。

PRESENT STATUS OF MIND-SAND ACTIVITY IN BEIJING REGION

From analytical data of precipitation and evaporation in thirty-five years (1949 to 1984) one might conclude that spring drought often occurred in Beijing region. Frequent, dry wind in spring and abundant sand source derived from frequent outbursts of the Yongding River during the historical period served as a foundation for the wind-sand activity in Beijing region, wind-sand activity in Beijing region, with blowing sand being the predominant form, most often occurred in spring, followed by winter. During the half-year period from winter to spring, days of blowing sand constitute 80% or more. The frequency of wind-sand activity is closely related to the greenland construction.Afforestation in the initial period after the founding of new China and planting trees and grass in 1980S played an important role in controlling wind-sand activitie s.In order to express the intensity of wind-sand activity the author introduced a new physical measure-blowing sand capacity.It may be defineb as the blowing sand ability equaling to the sum of vectors cubed of difference between threshold velocity and maximum of mean wind speed in ten minutes from hour to hour in given time interval, i. e.