Influência da variabilidade climática no avanço e recuo dos processos de desertificação no Estado do Rio Grande do Norte.

Abstract

The objective of this study is to verify the importance of climatic variability produced by the tropical Pacific and Atlantic Ocean temperature anomalies, over the fluctuations in the aridity indices and consequently in the desertification processes in the State of Rio Grande do Norte. Monthly precipitation totals of 57 stations, which are spacially distributed over the State of Rio Grande do Norte, and the mean monthly values of air temperature and insolation of six stations were used in this study. The air temperatures were estimated, for those stations which did not possess the observed temperature data, for those years of occurrence of the events of El Nino, La Nina, Positive South Atlantic Dipole and Negative South Atlantic Dipole. The aridity indices were calculated for each of the above events and the results of these indices were compared. It is observed that in the years of El Nino and Negative South Atlantic Dipole, there was a decrease in the annual precipitation totals throughout the State and an increase in values of insolation, air temperature and evapotranspiration. Consequently, there is a rise in the aridity indices, which resulted in the predominance of arid and semi-arid climatic regions practically throughout the State. In the years of occurrence of La Nina and Positive South Atlantic Dipole there was an increase in the annual precipitation totals throughout the State and a decrease in the values of insolation, air temperature and evapotranspiration. As a consequence of this, there is a decrease in the aridity index, which resulted in the predominance of sub-humid and humid regions throughout the State. Thus reducing the areas affected by the processes of semidesertification. This interannual fluctuation is reflected in the degree of aridity contributing to the advancement or recession of the desertification processes in the State. Besides these climatic fluctuations, practically all the predominant soils in that State are not fertile, principally, deficient in mineral, plant and organic nutrientes, and as a result they are vulnerable to desertification. Practically, the whole State of Rio Grande do Norte is susceptible to the conditions of desertification.