Observed and estimated atmospheric thermodynamic instability using radiosonde observations over the city of Rio de Janeiro, Brazil
Estimating critical weather conditions for the generation of storms with heavy rainfall represents one of the main challenges in the scientific community, especially in the warm season. While the use of radiosonde data is a possible option, an important limitation for achieving reliable forecasting of extreme rainfall events is undoubtedly low spatio-temporal resolution. As such, this research work endeavored to provide a special contribution by analyzing radiosonde data specifically collected for such evaluation applied to a tropical area, namely the city of Rio de Janeiro, Brazil. In that context, we applied a method recommended by previously reviewed literature consisting of replacing air temperature of a sounding probe launched in the morning (12 UTC) with forecasted values using data observed in the afternoon in order to gauge the method. Data points measured by radiosondes launched in the afternoon (between 12 and 7 pm local time) were used to evaluate the proposed method. The results showed that the atmosphere presented the highest heating rates in the atmospheric layer closest to the surface during the afternoon for diurnal clouds (DC) days. Similar behaviour was observed for the days of the South Atlantic Convergence Zone (SACZ). For days with frontal system (FS) presence, however, lower temperature values were observed in the afternoon in relation to the measured by morning soundings. Winds presented northeast and southwest components leading to the occurrence of warm and cold advection, respectively, in the analyzed region. Thermodynamic variables tended to be overestimated in relation to observed field results in most of the analyzed days.