Análise dos processos de formação de nevoeiro nos aeroportos de Manaus-AM

Abstract

Analyzing the fog formation processes in Manaus-AM and creating an operational forecasting method were the main objectives of this work. The scarcity of works on fog in the northern region of Brazil motivated the understanding in order to its formation process. Of the 10 years of data, 741 cases were identified at Eduardo Gomes airport and 8 at Ponta Pelada airport. Analyzes were performed for a sample of the most intense events for each airport, during the dry season and rainy season. The analyzes were composed by: (1) Analysis of surface variables (air temperature at 2m (T), dew point temperature (Td), relative humidity (RH), wind direction and speed and precipitation); (2) Thermodynamic analysis (vertical temperature and humidity profiles constructed by reanalysis data) and (3) Synoptic Analysis (Streamline, divergence and omega fields constructed by reanalysis data). The PAFOG model was also used in order to analyze the predictability and performance of the model for the northern region of Brazil. At Eduardo Gomes airport, the data observed in the surface analysis did not show significant differences between the dry and rainy seasons. In both seasons the average temperature was 23°C; T-TD between 0 and 2°C; wind direction between 220 and 50° and wind speed between 00 and 03KT. There was precipitation preceding the events in most cases. In Ponta Pelada, the surface variables, individually, compose a scenario less favorable to fog formations. However, the average conditions showed high relative humidity (between 94% and 100%) and T-TD between 1 and 2°C. Wind direction was the variable that most diverged between airports. The predominant wind direction in Eduardo Gomes was north-northwest, while in Ponta Pelada, it was not possible to determine the predominance due to the observed variations. The thermodynamic profiles showed that fogs in Manaus were formed under conditions of: conditionally unstable atmosphere; weak or no inversion and wet layer up to 900 hPa. The active synoptic systems that influenced fog formations during the rainy season were VCAN, Alta da Bolivia and trough in the northeast region. During the dry season, there was influence of anticyclones and ridges in the North, Northeast, Midwest and Northern Hemisphere. The predictability of the PAFOG model was considered satisfactory for all cases analyzed and the forecast was classified as good/excellent. The results allowed the construction of an operational forecasting method based on favorable conditions for fog formation in Manaus in observational, synoptic and thermodynamic aspects.