Speaker
Description
The ECMWF stratospheric humidity analysis is currently unaffected by assimilation, in both the Numerical Weather Prediction (NWP) configuration and the Atmospheric Composition configuration that is used by the Copernicus Atmosphere Monitoring Service (CAMS), because the analysis increments are forced to be zero above a diagnosed model tropopause. The humidity near the tropopause is incremented only if is necessary to remove supersaturation caused by a temperature increment. The ECMWF forecasts exhibit an extratropical lower stratospheric moist bias that is co-located with a cold bias. The temperature is constrained by observations in the analysis, but the cold bias then grows with forecast time above the tropopause due to an excessive long-wave radiative cooling from the additional moisture.
As developed in the Horizon Europe CAMEO project, we allow stratospheric humidity increments and conjointly assimilate EOS-Aura Microwave Limb Sounder water vapour retrievals. This new development successfully reduces the moist bias in the analysis and improves humidity and temperature forecasts. This work is needed as preparation for the development of a weak constraint 4D-Var framework for stratospheric humidity in the IFS.
| You plan to attend | On site (at FZ Jülich) |
|---|
