Accurate Numerical Weather Prediction (NWP) is one of the essential information for natural disaster prevention. Japan
Meteorological Agency (JMA) has been operating a Meso-scale model (MSM). The target of the MSM is to provide
guidance for issuing warnings or making very short-range forecasts of precipitation to cover Japan and its surrounding
areas. In order to produce accurate precipitation forecasts by MSM, realistic moisture fields as initial conditions are
necessary. The initial fields are produced in analyses with a four dimensional variational data assimilation method. The
initial fields are updated eight times per day to capture rapid change of mesoscale weather conditions.
Because Japan is a country surrounded by ocean, moisture information over the ocean is a key for the accurate humidity
analysis and the precipitation forecasting. Observations of microwave imagers in space contain the moisture information
over the ocean. The microwave imager data are available in wide coverage under all weather conditions and play an
important role in the analysis.
Microwave brightness temperature in clear sky condition and retrieved precipitation in rainy condition from various
microwave imagers are assimilated in the analysis. In this study, Global Change Observation Mission 1st Water (GCOM-W1)
/ Advanced Microwave Scanning Radiometer-2 (AMSR2) data were newly incorporated in the analysis. From the
preliminary AMSR2 data assimilation experiment, improvements of the humidity analysis and the precipitation
forecasting were found. The results suggest the use of multiple satellite data is necessary to produce realistic moisture
fields as the initial condition for the operational NWP.
The Global Change Observation Mission (GCOM) consists of two polar orbiting satellite observing systems, GCOM-W
(Water) and GCOM-C (Climate), and three generations to achieve global and long-term monitoring of the Earth.
GCOM-W1 is the first satellite of the GCOM-W series and scheduled to be launched in Japanese fiscal year 2011. The
mission instrument will be the Advanced Microwave Scanning Radiometer-2 (AMSR2), which is the successor
instrument of AMSR on ADEOS-II and AMSR-E on EOS Aqua platform. Development of the GCOM-W1 system
progresses favorably. The mechanical and thermal tests using the GCOM-W1 structural and thermal model were
successfully completed. The GCOM-W1 and AMSR2 proto-flight models are under their proto-flight testing. In the
middle of 2010, AMSR2 will be delivered to satellite system prior to the system proto-flight test of GCOM-W1.
Retrieval algorithms are being developed by collaborating with principal investigators. Algorithm comparisons or
integrations are now underway for several algorithms to find best available algorithms for post-launch processing. Also,
maintaining and extending the validation sites such as the Mongolian Plateau site for soil moisture is being implemented.
In addition to the long-term climate variability monitoring, meteorological applications will be the most important
operational utilization of AMSR2 data. Currently, AMSR-E data are being used for numerical prediction through data
assimilation at several meteorological agencies. Also, retrieved geophysical parameters such as sea surface temperature
are being used for diagnostics of the weather and ocean variations.