THE DROUGHT AND EXCESSIVE MOISTURE INDEXES IN A HISTORICAL-PERSPECTIVE IN THE PRINCIPAL GRAIN-PRODUCING REGIONS OF THE FORMER SOVIET-UNION

The paper deals with catalogs (two listing by years) of droughts and c onditions of excessive moisture in May-July in the basic cereals-produ cing area of the former Soviet Union (FSU) for 1891-1995. To calculate catalogs, data on precipitation averaged over the area of administrat ive regions and temperature at meteorological stations were used. The problem of the inhomogeneity of precipitation series at stations in th e warm period of year is discussed, related to the introduction of cor rections for moistening rain gauge bucket. The suggested catalogs of d roughts and excessive moisture (index DM) explicitly include the area of distribution of certain precipitation and temperature combinations. This is their principle difference from other authors' catalogs. The paper studies the relationship between the index DM in the European (E P) sind Asian (AP) parts of the territory under consideration with oth er drought indices and with the anomalies of cereals yield. Linear tre nds of the DM index series are presented, as are series of precipitati on and temperature in May-July for 105 yr. It is shown that the DM tim e series for the European part is practically stationary. In the AP te rritory in May-July, the aridity grows (the positive trends of the DM index are statistically significant). The aridity growth in the AP of the basic cereals-producing area of the FSU is mainly determined by te mperature rise; the negative, but statistically insignificant, trend o f precipitation intensifies this process.