All‐sky microwave humidity sounder assimilation in the Korean Integrated Model forecast system

The Korean Integrated Model (KIM) and hybrid data assimilation system were extended to assimilate all‐sky radiance from microwave satellite sensors. Initially, a radiative transfer model for the TIROS Operational Vertical Sounder (TOVS), called RTTOV‐SCATT (version 11.3), was implemented to assimila...

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Bibliographic Details
Published in:Quarterly journal of the Royal Meteorological Society 2020-10, Vol.146 (732), p.3570-3586
Main Authors: Lee, Sihye, Song, Hyo‐Jong, Chun, Hyoung‐Wook, Kwon, In‐Hyuk, Kang, Jeon‐Ho, Lim, Sujeong
Format: Article
Language:English
Subjects:
all‐sky assimilation
Analysis
Brightness temperature
Data assimilation
Data collection
East Asia
Heavy rainfall
Humidity
Humidity profiles
Hydrometeors
Meteorological satellites
microwave satellite
Profiles
Radiance
Radiative transfer
Rain
Rainfall
RTTOV‐SCATT
Sky radiance
Specific humidity
Surface radiation temperature
Temperature and humidity profiles
Tropical environments
Weather forecasting
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Summary:The Korean Integrated Model (KIM) and hybrid data assimilation system were extended to assimilate all‐sky radiance from microwave satellite sensors. Initially, a radiative transfer model for the TIROS Operational Vertical Sounder (TOVS), called RTTOV‐SCATT (version 11.3), was implemented to assimilate the Microwave Humidity Sounder (MHS) 183 GHz channels over the ocean. Cloud and precipitation parameters are not directly assimilated into our system, but temperature and humidity profiles are improved in the all‐sky assimilation. In the cycled analysis and forecast experiments, an assimilation of the MHS in a cloudy region shows globally substantial benefits: the coverage of the MHS radiance data is increased by 23–28% in the all‐sky assimilation. It is demonstrated that RTTOV‐SCATT well describes the brightness temperature (TB) on selected cloudy pixels over the Tropics and the Southern Hemisphere, with potential for linking the TB innovation to the increment for the hydrometeor variable. As a result, a reduction of 1.11% in the specific humidity root‐mean‐square error occurs in the 6‐hr forecast field as compared to the European Centre for Medium‐Range Weather Forecasts (ECMWF)'s Integrated Forecasting System (IFS) analysis. Even though the all‐sky MHS assimilation's impact on the Northern Hemisphere midlatitudes is not remarkable, it nonetheless produces an improved humidity analysis increment for a heavy rainfall case over East Asia. The radiative transfer model for the TIROS Operational Vertical Sounder (RTTOV) works most effectively, in terms of accurate simulation of brightness temperature and reliable Jacobian sensitivity, when hydrometeor components in the convective area are taken into consideration. The availability of the radiance data over the convective region increases the persistence of weather forecasting with the aid of extended satellite observation coverage. Forecast error decreases globally with a statistical significance, and a case study related to heavy rainfall over Japan shows that the all‐sky radiance data assimilation improves a longer‐range weather forecast case study.
ISSN:0035-9009
1477-870X
DOI:10.1002/qj.3862