Francesco De Angelis: “Study of the ground-based microwave radiometer data impact on short and medium term weather forecasts”

Ground-based microwave radiometers (MWR) offer the capability to provide continuous observations of the atmospheric thermodynamic state in the planetary boundary layer (PBL). The focus on PBL and the high temporal resolution candidate MWR to supplement radiosonde and satellite observations for feeding modern numerical weather prediction (NWP) models through variational data assimilation. This assimilation technique requires a fast radiative transfer model and a variational assimilation algorithm. The radiative transfer model is necessary for going from the model state vector space to the observation space at every observation point. The model RTTOV is well accepted in the NWP community, though it was developed to simulate satellite observations only. In the first part of this work, the RTTOV code has been modified to allow for simulations of ground-based upward looking microwave sensors. The proposed ground-based version of RTTOV, called RTTOV-gb, has been validated against accurate and less time-efficient line-by-line radiative transfer models. In the second part of this work, RTTOV-gb has been interfaced with the one-dimensional variational (1D-Var) software tool developed at UK Met Office to retrieve temperature and humidity profiles and liquid water path (LWP) by combining ground-based MWR observations with a priori information from a NWP forecast. RTTOV-gb has been applied as the forward model operator within the Met Office 1D-Var software tool in two different assimilation experiments: the first with simulated observations and the second with real observations from operative MWRs. Successful retrievals have shown the feasibility of using the 1D-Var tool interfaced with RTTOV-gb for a direct, safe, and fast data assimilation of MWR radiance observations into NWP models. The work described above completes the steps needed for MWR data assimilation into NWP and thus paves the road towards the operational exploitation of these crucial, but so far under-exploited, instruments.

Biografia.

Francesco De Angelis is a PhD student in the Department of Physical and Chemical Sciences (DSFC) of the University of L’Aquila. His research interest is focused on the assimilation of ground-based microwave radiometer radiances to improve the NWP model forecasts in the Planetary Boundary Layer (PBL).

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