Classificação de áreas semiáridas e subúmidas secas utilizando diferentes índices climáticos.

Abstract

The present research aims to show that even using quantifying methods, the delimitation of the semiarid areas can undergo changes, according to the method used. Climatological data from the meteorological stations of the National Institute of Meteorology (INMET) were used of the nine states of the Northeast, northern Minas Gerais and Espírito Santo and western Goiás. The climate classification was based on effective moisture indexes of Thornthwaite (Im) and aridity of the United Nations Environment Program (IaUNEP). For the estimation of potential evapotranspiration, we used the Thornthwaite and PMF methods. We also used fixed values of the available water capacity in the soil (AWC) of 100 and 50 mm to verify AWC influence on the climate classification according to the effective moisture index and the ET0 estimate by PMF and Thornthwaite. The results show that the use of potential evapotranspiration estimated by PMF has a much higher ET0 when compared to that estimated by Thornthwaite, leading to a more arid climatic classification for the arid, semi-arid, dry sub-humid and humid sub-humid lands. For the arid and semi-arid areas estimated with Im and ET0 by PMF, there is an increase of approximately 185,000 km2 (377%) for the arid climate and 78,500 Km2 (10%) for the semiarid, when compared to Im and ET0 by Thornthwaite, resulting in higher conditions of aridity and semi-aridity. The climate classification with IaUNEP and ET0 by PMF also showed an almost 100% increase in the semi-arid climate when compared to IaUNEP and ET0 by Thornthwaite, but with a reduction of up to 50% in the arid climate when compared to IaUNEP and ET0 by PMF with Im and ET0 by PMF. When analyzing the AWC fixed values, which were used to calculate the Im index with ET0 estimate by PMF and Thornthwaite, we note that reducing the value of AWC by 50% did not show significant variations that alter the type of climate of the study geographic area.