Abstract
In this study, we evaluated the impact of directly assimilating radiance on Hurricane Katrina forecasts over the Gulf of Mexico in the southeastern United States in August 2005. The ATOVS (i.e., The Advanced Television and Infrared Observation Satellite (TIROS)-N Operational Vertical Sounder) radiance data, the Gridpoint Statistical Interpolation (GSI) three-dimensional variational analysis (3DVAR) system, and the Advanced Research WRF (ARW WRF) model were employed. The results in a series of experiments show that after radiance data assimilation, the intensity and structure of initial fields including atmospheric flow, temperature and moisture have been modified somehow, especially with instruments using microwave bands such as AMSU-A/B. An anomalous southward pressure gradient has been added behind the hurricane center, which made the easterly flow go through the initial vortex center, accelerating westward movement of the hurricane. All data assimilation experiments obtain a similar forecast for the hurricane track before 36 h of model integration. After 36 h, the hurricane tracks in AMSU-A/B experiments are closer to the best track, but the tracks in HIRS3 and control experiments have a bigger error. However, we note that the improvement is limited, all assimilation experiments did not properly depict the deepening of the hurricane center around 1800 UTC 28 August.
Highlights
The assimilation of satellite radiance observations into a numerical weather prediction (NWP) system is an important path to improve weather forecasts by providing initial conditions that are more representative of the true state of the atmosphere
There are a total of 7 available sensors, including Advanced Microwave Sounding Unit (AMSU)-A/B in National Oceanic and Atmospheric Administration (NOAA)-15, AMSU-A/B and HIRS/3 in NOAA-16, and the AMSU-B and HIRS/3 in NOAA-17 used in this study
We evaluated the impact of ATOVS including AMSU-A, AMSU-B and HIRS/3 radiance direct assimilation through the JCSDA prototype Community Radiative Transfer Model (pCRTM) on the forecasts of Hurricane Katrina over the Gulf of Mexico in the southeastern United States in August 2005
Summary
The assimilation of satellite radiance observations into a numerical weather prediction (NWP) system is an important path to improve weather forecasts by providing initial conditions that are more representative of the true state of the atmosphere. Preliminary impact studies of satellite data using satellite retrieved winds, and humidity were focused on the global system. The results shows a positive impact of satellite data on numerical weather prediction, especially in the Southern Hemisphere [1,2,3,4,5,6] The satellite data are a useful data source in global models and in regional models. The satellite data assimilation shows a strong regional feature. The impact of satellite data in regional models in North American regions, including the North American Continent surrounded by the ocean, is not very clearly. The purpose of this paper is to evaluate the impact of satellite observation data assimilation on the simulation used in a regional model
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