Targeted Doppler lidar observations during NA-TReC (14-28 November 2003)

Last update: 22 November 2005

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Overview

The North Atlantic THORPEX Regional Campaign (NA-TReC) in 2003 was part of the THORPEX Programme of the World Meteorological Organization. The objective of the campaign was to investigate the influence of additional observations on numerical weather prediction. ECMWF, UK Met. Office, Meteo France, NCEP and NRL calculated sensitive regions (regions where the largest impact on the forecast is expected), and additional observations in these areas were performed.

For the first time a scanning airborne Doppler lidar was used for these "targeted" observations during the campaign. A 2 µm Doppler lidar was operated on a Falcon 20 aircraft for 28.5 flight hours and measured ~1594 wind profiles (see measurements). Due to low observational and representativeness errors, the total error of these lidar winds for the assimilation in NWP models is 1-1.5 m/s, which is lower than the error of all other wind measurements in the current operational observing system and dropsondes (Weissmann et al. 2005 ).

The measurements were assimilated in several experiments using the ECMWF T511 global model and compared to a control run without additional observations. All experiments with lidar data showed a mean reduction of the 1-4 day forecast error of geopotential height in the period of the lidar deployment. The impact of the lidar measurements was higher than the impact of 100 dropsondes in the same period.





Contact: Andreas Dörnbrack, Martin Weissmann
Institut für Physik der Atmosphäre


Design: Martin Großhauser
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