Sistemas meteorológicos e sua relação com altos valores de espessura ótica dos aerossóis no Rio Grande do Sul

Abstract

Consisting of solid and liquid particles suspended in the atmosphere, aerosols affect the radiative balance of the Earth through the scattering and absorption of solar radiation. By floating in the atmosphere they can be advected through long distances. Southern Brazil may suffer influences of various types of aerosol particles, both transported from other regions or locally emmited, resulting in high optical thickness values of aerosols over this region that needs to be studied. Understanding how active weather systems in South America influence aerosol optical thickness (through transport and deposition of aerosols), it is essential to analyze its effects on the study area. Thus, the main objective of this work was to identify the active synoptic systems for cases with high occurrence of Aerosol Optical Thickness (AOT) values in Rio Grande do Sul state. The cases selected for analysis were separated by the 99 percentile (P99), indicating days with higher AOT values, indicating regions where this occurred within the southern region of Brazil for the period from 2002 to 2011. For the synoptic analysis, data with spatial resolution of 2.5 ° and time of daily averages were used, obtained from reanalysis 2 data from NCEP / NCAR (National Centers for Environmental Prediction / National Center for Atmospheric Research). Composite fields were generated for the days with occurrence of high AOT values (t=0) in addition to the previous (t-1, t-2 and t-3) and subsequent days of this occurrence (t+1 and t+2) for August, September and October (where there werethe most frequent days of these high AOT values) to analyze the possible occurrence of a pattern. The selected cases were also related to climatic events ENSO and ENSO Modoki. It was found that, for the selected sample, 84% of the cases occurred in ENSO period and 28% in ENSO Modoki. Furthermore, according to the composite fields examined, some systems showed persistence and the potential to alter AOT. The developed conceptual models highlighted the systems of the South Atlantic Subtropical High, the flow in the levels of 850hPa and 700hPa and the low and high surface pressure system.