Vegetative Stress Analysis, Associated with Climate Variables in Northeast Brazil and in the Municipalities of Ceará >/>(Fortaleza, Jaguaruana and Campos Sales)

Abstract

The Northeast region of Brazil - NEB has 1,561,177.8 km², of which approximately 61.7% constitutes the Brazilian semiarid, forming a special territory with annual temperature averages between 23 °C and 27 °C, with rainfall below 800 mm and relative humidity around 50% and high evaporation rates in the order of 2,000 mm year^-1, which makes NEB very affected by the variability of most climatic variables. The loss and temperature of the air on the surface extinguished vital meteorological conditions in the hydrological cycle, in addition to its influences on human activities, has a strong influence on the maintenance of vegetation cover and consequently on the natural ecosystem of a region. This study investigated the existing correlation between climatic variables and variables related to the exclusion and temperature of the surface air, with the vegetation cover of the region using the Normalized Difference Vegetation index - NDVI, vegetation condition index - VCI and the Temperature Condition Index - TCI. It was investigated how these VCI, TCI and NDVI indices measured the air temperature in some municipalities in the state of Ceará: Fortaleza - region of high urban development; Jaguaruana - rural characteristic and Campos Sales - Sertão Central. Remote sensing data (NOAA-NESDIS) was used in a historical series (1982 to 2015) and classified into: seasonal periods, ten-year periods and years of climatic contrasts (La Niña, El Niño and Normal Conditions). The data were processed in FORTRAN and GrADS (Grid Analysisand Display System) routines. The results of the positive trend between the positive indices (NDVI, VCI and TCI) in the semi-arid region of NEB. When analyzing other areas of the NEB region with higher precipitation rates, the results were not as noticeable. The monitoring of seasonal and interannual thermal stress in the semi-arid sub-regions of the NEB, east of the NEB and south of the NEB was quite significant and favored the regions with low levels of precipitation indicating that the VCI, TCI and NDVI can be used for monitoring droughts , however, these indices can obtain different results and noise when supplied or in regions with high graduation rates. Pearson's correlation coefficient was used to correlate the “Air” temperature of the surface measured at stations in the cities of Fortaleza, Jaguaruana and Campos Vendas with the mean TCI and VCI indexes and that Strong Correlation (0.80). From the t-Student test the critical correlation coefficient (rc) was extracted, which has a 95% significance with the observed data, proving that the TCI and VCI can be indicative of stress conditions in the cities vegetation, as it has a strong correlation with the meteorological variables analyzed.

Keywords:
vegetative stress; climaticvariability; remote sensing