MONITORING OF WIND SPEED IN THE VOLGA AND URAL RIVER BASINS IN THE TWENTIETH CENTURY

摘要

Possible causes of the discontinuty of the initial series of wind speed (replacement of a wind vane by anemometer, change in the height at which a wind-measuring instrument is mounted, relocation of meteorological sites, and development and afforestation of the areas around meteorological sites) are analyzed on the basis of standard observations of wind speed at 22 weather stations located in the basin of the Volga and Ural rivers. The data are taken from the archives of the All-Russia Institute of Hydrometeorological Information—World Data Center. Linear trends of annual mean wind speed are calculated for individual stations and averaged over natural zones for three periods: 1936-2000, 1961-1991, and 1961-2000. It is shown that at most stations (when the series inhomogeneity is removed) the annual mean speed decreases in all three periods. The 1936-2000 mean speed decreases by a factor of 2.1 in a zone of sufficient and excessive moisture; by a factor of 1.5 in a slightly arid and arid zone; and by a factor of 1.4 in an extremely arid and dry zone. Based on a physiographic description of 17 weather stations, the types of enclosure of meteorological sites in the early 1960s and in 2001 are compared. By rough estimates, about 60% of a decrease in the 1936-2000 annual mean wind speed is explained by an increased enclosure of meteorological sites and only about 40% is attributed to natural processes.