Impact of GOES-16 Clear-Sky Radiance Data Assimilation in JMA’s Global NWP System

Clear-Sky Radiance (CSR) data mainly have information on tropospheric humidity under clear-sky conditions. Japan Meteorological Agency (JMA) uses CSR data from geostationary meteorological satellites in the global data assimilation (DA) system. Reductions of dry biases in the middle-troposphere analysis and improvements of forecasting errors of specific humidity with JMA’s global spectral model (GSM) were reported from CSR data assimilation experiments (e.g. Kazumori 2018, Shimoji et al. 2018).
A new methodology for radiative transfer (RT) calculation using retrieved land surface temperature data (Okabe 2019) was developed for assimilating surface-sensitive CSR data from Himawari-8 (6.9 µm; band 9 and 7.3 µm; band 10), Meteosat-8 and -11 (7.35 µm; channel 6) in the JMA DA system. Since accurate land surface information is required for RT calculation of such CSR data, land surface temperatures retrieved from observed window channel’s (10.8 µm; Himawari-8’s band 13 and Meteosat’s channel 9) CSRs are used instead of first-guess (FG) surface temperatures from GSM. Furthermore, the emissivity atlas of Wisconsin University (Borbas and Ruston 2010) is adopted as land surface emissivity data in RT calculation instead of a fixed value to include the seasonal and regional variability.
GOES-16 CSR data have been assimilated in JMA’s DA system with the new methodology since June 2019. According to assimilation experiments, GOES-16 CSR data assimilation improved water vapor and temperature fields’ accuracy in FG, forecasting scores of specific humidity, temperature and geopotential height, and hurricane track prediction scores over north-east Pacific Ocean. The improvement of forecasting score of each element was especially observed in the tropical troposphere, and remained up to about two days in the forecasting of JMA’s GSM. The details of the experiments’ results will be presented in this conference.

References

Borbas, E. E. and B. C. Ruston, 2010: The RTTOV UWiremis IR land surface emissivity module, AS Mission Report NWPSAF-MO-VS-042, EUMETSAT Numerical Weather Prediction Satellite Applications Facility, 24pp.

Kazumori, M., 2018: Assimilation of Himawari-8 Clear Sky Radiance data in JMA's global and mesoscale NWP systems. J. Meteor. Soc. Japan, 96B, 173-192.

Okabe, I., 2019: Operational use of surface-sensitive Clear-Sky Radiance (CSR) data in JMA’s Global NWP System. CAS/JSC WGNE Research Activities in Atmospheric and Oceanic Modelling, Rep. 49, 1.15-1.16.

Shimoji, K., I. Okabe, and M. Kazumori 2018: Operational use of Meteosat-11 Atmospheric Motion Vectors (AMVs) and Clear-Sky Radiance (CSR) Data in JMA’s Global NWP System. CAS/JSC WGNE Research Activities in Atmospheric and Oceanic Modelling, Rep. 48, 1.23-1.24.