Observational Analysis of Fog Events in the Area of the Rio de Janeiro Harbor, Brazil

Abstract

Fogs are meteorological events in which water vapor condensation in the atmosphere results in a horizontal visibility inferior to 1000 m, making air, sea and land traffic difficult. Fogs are classified according to their formation processes and require the presence of specific initial conditions, such as elevated humidity, thermal inversion and atmospheric stability. In general, when atmospheric temperature and dew point temperature are equal, there is fog formation. This can occur due to either atmospheric cooling or increase in atmospheric humidity. The objective of this study is to examine the meteorological conditions in Rio de Janeiro Harbor by analyzing the occurrence of fog, as well as observations of meta-oceanographic conditions associated with fog formation processes. Thirteen years of METAR data from surface meteorological stations located in Santos Dumont and Galeão airports were studied. The results revealed a strong seasonality of fog occurrence, showing a higher occurrence during autumn and winter. It was also observed that there is a relationship between the interannual variability and ENSO cycles and a strong fog event dependence on meteorological conditions such as atmospheric pressure and relative humidity.