Cartarea teritoriului României în raport cu lungimea medie a perioadelor de secetă şi uscăciune [Mapping of the Romanian teritory in relation with the average lenght of periods with drought and aridity]

The knowledge of natural risk of occurrence of drought period represents a necessity for the foun­dation of afforests technologies and silvicultural operations. The idea of synthesis is in the book of H. Walter (1974) and is based on the using of cli­matic diagrams type Walter - Leith for the delimitation of drought climate of Romania (Donița, 1967; Barbu și Cenușă 1975). Walter (1974) consider that the period·in which the precipitation curve at P = 2T scale is under the temperature curve is a drought period and the peri­od in which the precipitation curve at P = 3T scale is under the temperature curve is a aridity period. The delimitation of drought zone on the base of cli­matic diagrams type Walter-Leith (P < 2T) and aridity zone (P < 3T) in function of length of drought period or aridity period was made on basis of the analysis of the means from 27 weather station. The greatest correlation was found between the numbers of drought (aridity) days and the annual mean precipitation or station (r = -0.82). The maxi­mum number or days with drought is registered in the regions with precipitations smaller that 400 mm /year and is great that 50 day or drought and 150 day of aridity. and the minimum in the regions with Pma greater that 600 mm /years. Practically in these regions the drought is missing and the num­ber of aridity days is lower than 50 days/year. The multiple regression between number of drought days (aridity) and the geographic (altitude, latitude, longitude) and climate parameters (Tma, Pma) were established. Nu = 245 - 0.015AIt - 3,52Lat + 0,67Long - 0,37Pma + 1 0,6 Tma (R multiple = 0,88; R2 = 0,78); Ns = 102,4 - 0,15Alt - 0,034Lat + 1,92Long - 0,36Pm + 13,89 Tma (R multiple = 0,915; R2 = 0,838). The multiple correlation coefficients calculated have very significant values. This permit the graph­ical representation or number of drought days (arid­ity) in relation with 2-5 geographical parameters using geostatistical analysis.