Estimativa de saldo de radiação comparando os modelos de elevação digital, med cotado e o SRTM, na bacia do rio Jacarecica

Abstract

For the study of the processes occurring in the biosphere it is vitally important to be aware of the amount of energy used for the movement of all mechanical giving supports life on Earth. Therefore, knowing the net radiation at the earth's surface is fundamental in understanding this mechanics. Despite the importance of this variable, its measure in-situ or estimative with meteorological data is not always available. Thus, the use of satellite images is an alternative method to estimate the net radiation. Added to this methodology, the use of Digital Elevation Models allows aggregate the effects of topography to the components of the radiation balance. On the other hand, the river basin Jacarecica is practically devoid of hydrometeorological information. In this context, this study aimed to compare the estimates of net radiation obtained from MED's different in the river basin Jacarecica. For this, we used the SEBAL, images of the TM-Landsat 5 of 03/09/2003 and 17/03/2011, and two digital elevation models, namely: MED-SRTM (90 m) and MED-Cotado (15 m), the first obtained free of charge and the second drawn from elevation points of the cartographic base of Maceio. It was observed that the MED-Cotado presented a spatial pattern very similar to MED-SRTM, but with more detailed representation of relief nuances. The net radiation estimated MED-Cotado had a better representation of spatial continuity, being the areas with the highest values with east orientation, while areas with lower values have west orientation. The use of MED-SRTM tended to underestimate the net radiation values on the faces with orientation N, NE, E, SE, and to overestimate the phases S, SW and W. The net radiation showed an increase in 17/03 / 2011 which can be linked to natural causes such as: reduction of soil moisture, increased short-wave radiation, surface temperature elevation and orientation of relief. Already the net radiation reduction may be related to anthropogenic causes, such as replacement of vegetated areas by built.