A size‐segregated soil dust emission and transport model, Northern Aerosol Regional Climate Model (NARCM), was used to simulate the production and transport of Asian soil dust during the Aerosol Characterization Experiment‐Asia (ACE‐Asia) period from March to May 2001. The model is driven by the NCEP reanalyzed meteorology and has all the atmospheric aerosol physical processes of soil dust: production, transport, growth, coagulation, and dry and wet deposition. A Chinese soil texture map that infers the soil grain‐size distribution with 12 categories was generated to drive the size‐distributed soil dust emission scheme [Alfaro et al., 1997; Marticorena and Bergametti, 1995]. The size distribution of vertical dust flux was derived from the observed surface dust‐size distribution in the desert regions. Parameters applicable to the Asian deserts for the dust emission scheme are assessed. Model simulations were compared with ground‐based measurements in East Asia and North America and with satellite measurements for the same period of time. The model captured most of the dust mobilization episodes during this period in China and reasonably simulated the concentrations in source regions and downwind areas from East China to western North America. About 252.8 Mt of soil dust below d < 40 μm was estimated to be emitted in the East Asian deserts between 1 March and 31 May 2001 with ∼60% attributed to four major dust storms. The vertical dust loadings above 700 hPa correlate reasonably well with Total Ozone Mapping Spectrometer aerosol index (TOMS AI) observations. The sensitivity analysis of model performance to soil size distribution, water moisture, and meteorology was carried out with the observational data to establish the most appropriate parameters and conditions for the Chinese soil dust production and transport.

The purpose of the International Global Precipitation Measurement (GPM) Program is to develop a next-generation space-based measuring system which can fulfill the requirements for frequent, global, and accurate precipitation measurements. The associated GPM Mission is being developed as an international collaboration of space agencies, weather and hydrometeorological forecast services, research institutions, and individual scientists. The design and development of the GPM Mission is an outgrowth of valuable knowledge and published findings enabled by the Tropical Rainfall Measurement Mission (TRMM). From the TRMM experience, it was recognized that the GPM Mission must consist of a mixed nonsunsynchronous and sunsynchronous orbiting satellite constellation in order to have the capability to provide physically based retrievals on a global basis, with ~3-h sampling assured at any given Earth coordinate ~90% of the time. The heart of the GPM constellation is the Core satellite, under joint development by NASA and the Japan Aerospace Exploration Agency (JAXA), which will carry a dual frequency Ku/Kaband precipitation radar (PR) and a high-resolution, multichannel passive microwave (PMW) rain radiometer. The core is required to serve as the calibration reference system and the fundamental microphysics probe to enable an integrated measuring system made up of additional constellationsupport satellites, each carrying at a minimum some type of PMW radiometer. In this article the background, planning, design, and implementation of the GPM is described.

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