The impact of NAWDEX dropsonde and extra radiosonde observations on forecast quality and tropopause structure

Utilizing a multitude of in situ and remote sensing instruments, a comprehensive dataset was collected during the transatlantic field campaign NAWDEX in autumn 2016. Cycled data denial experiments with the global model of the ECMWF showed that additionally collected dropsonde and radiosonde observations contributed to a reduction in the short-range forecast error, with the most prominent error reductions being linked to Tropical Storm Karl, cyclones Matthew and Nicole and their subsequent interaction with the midlatitude waveguide. While the short-range forecast quality was improved, Schäfler et al. (2019, in review) demonstrated that ECMWF IFS analyses exhibit deficiencies in capturing observed wind speeds at and above the dynamical tropopause during NAWDEX. Therefore, data assimilation output from the ECMWF IFS is used to evaluate the observational influence on the tropopause. Statistics of data assimilation diagnostics such as the analysis increment and first guess departure will be assessed in observation space in a tropopause relative framework to quantify the impact of assimilated radiosonde observations on tropopause location and sharpness.