Estudo da variabilidade da coluna de água precipitável (pwc) no semiárido brasileiro para calibração de fotômetro solar

Abstract

Water is present in the atmosphere as vapor, from ground level to stratosphere. As a major component of the hydrological cycle, water quantity variation over a region causes climate change, affecting the economic and living conditions of the local population. The sun photometer allows you to monitor the variation of this precipitable water column (PWC) i.e. water vapor in atmosphere using solar radiation in the 940 nm band, where strong absorption occurs. For calibration of the sun photometer developed in this work, we investigated a site in the semiarid region of the Rio Grande do Norte state, near the city of Caicó, applying Modified Langley Method (MLM) which is a variation of the Langley Method. This methodology allows us to calibrate sun photometer for PWC in the open field, which under atmosphere optical stability condition makes possible to obtain best calibration constants than in laboratory. The results, during the study period, showed that the expected atmosphere optical stability for the calibration of the equipment did not occu