Climatic fluctuations and homogenization of Northeast Brazil using precipitation data

Abstract

In order to assess the cyclic variations in the precipitation series and to homogenize the precipitation regimes of the Northeast Brazil 70-years annual precipitation data of 105-locations were subjected to power spectrum analysis. In terms of some cycles the regions above and below 8^°S lat differ significantly. Also regions between 4-8^°S lat. are different in some respects from regions above 4^°S lat. This is true with respect to coefficient of variation of annual precipitation. The auto-regression of Fortaleza data of 1849 to 1981 revealed the presence of four cycles, namely 52, 26,13 and 6.5 years, The integrated curve of these four cycles is compared with the observed precipitation. The agreement in general is good with few exceptions. The same predicted curve is also used to compare with the observed precipitation at few other locations. The agreement is good only for few regions. The coefficient of variation of annual precipitation presented a non-homogeneity over regions above 8^°S lat. compared to regions below 8°S lat. This is also true even with the observed cycles. This type of discrepancy is attributed to the non-homogeneity in the data series, which is also substantiated with few examples. This study demonstrates that the basic precipitation data must be corrected for homogeneity before they are actually used in the agricultural productivity estimates or planning strategies using regression approach.