Análise dos processos físicos de formação da visibilidade baixa no Nordeste brasileiro e previsão pelos modelos PAFOG e FOGVIS

Abstract

Adverse meteorological phenomena can create serious economic and social losses, including human lives. Its formation is strongly connected to specific atmospheric conditions and synoptic scale systems in the region. Therefore, all over the world, models for adverse events forecast are being created for each region. The study goal was to analyze the physical processes of fog formation and meteorological phenomena that cause low visibility and forecast evaluation by the models. All fog events at the airports of Maceió (32 cases), Recife (1 case) and Campina Grande (185 cases) in the 13 years (2008 – 2020) were tabulated, and some were chosen for more detailed analysis. Data from different sources were used: a) airport surface data obtained by the Meteorology Network of the Aeronautics Command (REDEMET); b) GOES and METEOSAT satellite images provided by CPTEC, in the infrared and water vapor channels; c) reanalysis products of the ECMWF numerical models, ERA5 (0.25°x0.25°). The GrADS graphic software was used to create meteorological fields and vertical profiles for synoptic and thermodynamic analysis. The PAFOG model was developed in Germany and in this work it was adjusted to the local atmospheric conditions. FogVIS software was developed in the lab previously. These two models were used to fog forecast and to compare their results with data recorded by the METAR code. This was done to work out the most effective methodology in each scenario. In the cases of Maceió, they fog events were associated with low level trough at low levels and ridges from medium to high levels. In Campina Grande it was the opposite with ridge at low levels and confluence from easterly currents. The fog forecast by the PAFOG model with 18, 12 and 06 hours antecedence were very satisfactory for Maceió and Recife. For Campina Grande, fog forecasts with 18 hours antecedence are more satisfactory. To improve the execution of FogVIS in conjunction with the PAFOG model, the results of the 24-hour and 18-hour forecast were compared. The Fog Stability Index (FSI) indicated a high possibility of fog occurring 18 hours in advance. Both the FogVIS software and the PAFOG model showed, in general, better efficiency by forecasting 18 hours in advance. FogVIS made excellent forecasts for Maceió and Campina Grande, proving to be favorable to its use in these cities.