Relação entre expansão agrícola em áreas de caatinga e condições anômalas de radiopropagação.

Abstract

The innovations in technology in the telecommunications sector allowed the use of more efficient data transmission networks, making possible to attend with more efficiency the increasing need for wireless conexion of dispositives and equipments, in different areas of application. However, in the planning of a wireless network system it is important to consider the influence of the atmosphere in the trajectory of the radioelectric waves. The increase in knowledge about the phenomena of difraction, refraction (deviations in the trajectory of the waves), and attenuation by clouds and rain becomes relevant due to the association with atmospheric disturbances and occurrences of fading or signal loss. The delay or loss of radioelectric signals may interfere in human activities, causing significant social or economical impact. In this context, the objective in this research is to investigate in which manner the expansion in irrigated agriculture in areas of the Caatinga biome changes the local refractivity pattern. Landsat-5 (TM) satellite images, historical series of data collected in the surface meteorological stations of Petrolina (PE), Bebedouro (PE) and Mandacaru (BA), and data of upper air soundings made at Petrolina (PE). The results show that the increase in the moisture content in the area of the irrigated perimeters of Bebedouro-PE and Mandacaru-BA has a direct influence on the wet term of refractivity (Nu). Surface descontinuities resulting from changes in soil coverage and use are important factors in the variability of the vapour content in the low troposphere. On the regional scale, they may cause distortions in the propagation and intensity of the radioelectric signals. The expansion in irrigated agriculture in the region of Juazeiro-Petrolina represents an important source of moisture in the low troposphere and, as a consequence, of intensification of the horizontal gradient of the wet term of refractivity (Nu). Nuclei of higher moisture and Nu characterize the generation of microclimates in the area of Petrolina and Juazeiro.