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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Volume 8, issue 10 | Copyright
Atmos. Meas. Tech., 8, 4231-4242, 2015
https://doi.org/10.5194/amt-8-4231-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 14 Oct 2015

Research article | 14 Oct 2015

Impacts of AMSU-A, MHS and IASI data assimilation on temperature and humidity forecasts with GSI–WRF over the western United States

Y. Bao1,2, J. Xu2, A. M. Powell Jr.4, M. Shao2, J. Min1, and Y. Pan3 Y. Bao et al.
  • 1Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration, Nanjing University of Information Science and Technology, Nanjing, China
  • 2Global Environment and Natural Resources Institute, College of Science, George Mason University, Fairfax, Virginia, USA
  • 3School of Atmospheric Science, Nanjing University, Nanjing, China
  • 4NOAA Center for Satellite Applications and Research (STAR), College Park, Maryland, USA

Abstract. Using NOAA's Gridpoint Statistical Interpolation (GSI) data assimilation system and NCAR's Advanced Research WRF (Weather Research and Forecasting) (ARW-WRF) regional model, six experiments are designed by (1) a control experiment (CTRL) and five data assimilation (DA) experiments with different data sets, including (2) conventional data only (CON); (3) microwave data (AMSU-A + MHS) only (MW); (4) infrared data (IASI) only (IR); (5) a combination of microwave and infrared data (MWIR); and (6) a combination of conventional, microwave and infrared observation data (ALL). One-month experiments in July 2012 and the impacts of the DA on temperature and moisture forecasts at the surface and four vertical layers over the western United States have been investigated. The four layers include lower troposphere (LT) from 800 to 1000 hPa, middle troposphere (MT) from 400 to 800 hPa, upper troposphere (UT) from 200 to 400 hPa, and lower stratosphere (LS) from 50 to 200 hPa. The results show that the regional GSI–WRF system is underestimating the observed temperature in the LT and overestimating in the UT and LS. The MW DA reduced the forecast bias from the MT to the LS within 30 h forecasts, and the CON DA kept a smaller forecast bias in the LT for 2-day forecasts. The largest root mean square error (RMSE) is observed in the LT and at the surface (SFC). Compared to the CTRL, the MW DA produced the most positive contribution in the UT and LS, and the CON DA mainly improved the temperature forecasts at the SFC. However, the IR DA gave a negative contribution in the LT. Most of the observed humidity in the different vertical layers is overestimated in the humidity forecasts except in the UT. The smallest bias in the humidity forecast occurred at the SFC and in the UT. The DA experiments apparently reduced the bias from the LT to UT, especially for the IR DA experiment, but the RMSEs are not reduced in the humidity forecasts. Compared to the CTRL, the IR DA experiment has a larger RMSE in the moisture forecast, although the smallest bias is found in the LT and MT.

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The regional GSI-WRF system is underestimating the observed temperature in the LT and overestimating in the UT and LS. The microwave (MW) data assimilation (DA) reduced the forecast bias from the MT to the LS within 30-hour forecasts, and the conventional (CON) DA kept a smaller forecast bias in the LT for 2-day forecasts. The smallest bias in the humidity forecast occurred at the surface and in the UT. The DA experiments apparently reduced the bias from the LT to UT, especially for the IR DA.
The regional GSI-WRF system is underestimating the observed temperature in the LT and...
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