Thermodynamic indexes during the GOAmazon2014/5 campaign and comparison with ERA-Interim reanalysis data

Abstract

The thermodynamic indexes LCL, LFC, CINE and CAPE characterize atmospheric instability, and allow the study of cloud formation and convection, important phenomena for the hydrologic cycle and the radiative balance. For this reason, this work makes a seasonal analysis of these thermodynamic indexes computed from radiosondes released during the GOAmazon2014/5 experiment. A comparison was made with ERA-Interim reanalysis for both these indexes and the temperature and relative humidity profiles. Analysis of radiosonde data shows that the median vertical profile of relative humidity in the dry season was lower in 2015 when compared to 2014, resulting in higher LCL (~50 hPa at 18 Z) and lower CAPE (~50% lower). The difference stems from a more severe dry season in 2015 when compared with 2014. The comparison with the reanalysis reveals that modeled LCL values are only compatible with observed ones at 18 Z (mean bias -10 hPa). On the other hand, CAPE values are always incompatible (mean bias -750 j/kg). Results indicate that ERA Interim poorly represents the thermodynamic conditions over the Amazon rainforest.