Short-term forecasts of current high-resolution numerical weather prediction models still have large deficits in forecasting the exact temporal and spatial location of severe, locally influenced weather such as summer-time convective storms or cool season lifted stratus or ground fog. Often the thermodynamic instability - especially in the boundary layer - plays an essential role in the evolution of weather events. While the thermodynamic state of the atmosphere is well measured close to the surface (i.e. 2 m) by in-situ sensors and in the upper troposphere by satellite sounders, the planetary boundary layer remains a largely under-sampled region of the atmosphere where only sporadic information from radiosondes or aircraft observations is available. The major objective of the ARON project is to design an optimized network of ground based microwave radiometers (MWR) and compact Differential Absorption Lidars (DIAL) for a continuous, near-real-time monitoring of temperature and humidity in the atmospheric boundary layer in order to monitor thermodynamic (in)stability. For this a synergistic retrieval method combining satellite measurements with ground based microwave radiometers and DIAL will be developed. Since such a network does not yet exist, a virtual network will be simulated by using the reanalysis of the COSMO-DE model for Europe (CORDEX-area, 6 km horizontal resolution) and for Germany (2 km resolution). The fast radiative transfer operator RTTOV and its ground-based version (RTTOV-gb) will be used to provide simulated ground- and satellite-based measurements. Inversion techniques will be applied to retrieve thermodynamic profiles of humidity and temperature as well as cloud liquid water path or directly atmospheric stability indices at distinct locations in the model domain. By considering correlation/covariance between the model grid-boxes, the 2D model fields of stability indices or finally the 3D fields of temperature and humidity can be reproduced. An accuracy assessment will be carried out by considering the network configuration (i.e. instrument number/density) versus the estimated operation costs of the network. The ARON-project shall contribute to advancing the integrated forecasting system for seamless prediction of DWD by providing a near-real-time, continuous and more complete and accurate picture of the thermodynamic structure of the lower troposphere. We aim to quantify the impact of the new measurements systems on now-casting and short-term forecasting.

Löhnert, U., K. Ebell, E. Orlandi, M. Toporov: Combining ground-based and satellite remote sensing for improving the derivation of atmospheric stability, ISARS, 6-9 Juni 2016, Varna, Bulgaria