Naoto Ebuchi

W Timothy Liu

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AMSR AND DFS SYNERGY 
Naoto Ebuchi 1), and W. Timothy Liu 2)
1) Institute of Low Temperature Science, Hokkaido University 
2) Jet Propulsion Laboratory, California Institute of Technology 
1. INTRODUCTION 
A combination of spaceborne scatterometer and radiometer provides us with instantaneous observation of various 
physical parameters of air-sea interface, such as wind speed and direction, water vapor content, sea surface 
temperature (SST), and rain rate, which are essential to scientific studies of global climate changes. The combined 
observation also plays an important role in the operational applications, such as weather forecast and disaster 
prevention. The Japanese earth observation satellite, Advanced Earth Observing Satellite-II (ADEOS-II), which 
carried a microwave scatterometer, SeaWinds, and a microwave radiometer, Advanced Microwave Scanning 
Radiometer (AMSR), was launched by the National Space Development Agency of Japan (NASDA) in December 
2002, and the simultaneous observation was started. However, ADEOS-II failed in October 2003. A follow-up 
mission is required to continue the data flow for the operational applications and scientific studies. The Japan 
Aerospace Exploration Agency (JAXA), National Oceanic and Atmospheric Agency (NOAA), and Jet Propulsion 
Laboratory (JPL) are now proposing to launch the second satellite of the Global Change Observation Mission-W 
(GCOM-W2) carrying the Advanced Microwave Scanning Radiometer-3 (AMSR-3) together with Dual 
Frequency Scatterometer (DFS). This paper reviews sensor and science synergy of microwave scatterometers and 
radiometers. 
2. SENSOR SYNERGISM 
The simultaneous operation of the active and passive microwave sensors will contribute to improve sensor 
algorithms to estimate physical parameters. The radiometer measurements will be used by the scatterometer for 
rain flagging, corrections for the rain effects on the scatterometer signal, and improving wind retrieval under rain. 
Several studies have been conducted to investigate the impacts of rain on vector wind measurements by 
scatterometers [1], [2], [3], [4], [5] and corrections for the rain effect [5], [6], [7]. Scatterometer wind will be able 
to correct wind direction dependence of the radiometer measurements. Intercomparison of simultaneous 
measurements of wind speed by SeaWinds and AMSR on ADEOS-II clearly exhibited the systematic errors in the 
previous AMSR wind retrieval algorithm [8], [9], [10]. Refinements of the algorithm based on the results have 
successfully reduced the systematic errors in the retrieved wind [11], [12], [13]. 
3. SCIENCE SYNERGISM 
The simultaneous observation of the water vapor, precipitation and marine surface vector winds will have a 
significant impact on studies of the water-energy cycle, which is one of the most important scientific topics and 
social issues. The mission will provide a unique data set to investigate the balance among horizontal 
convergence/divergence of the water vapor, evaporation from the sea surface, and precipitation [14]. Monitoring 
these terms is critical to the characterization of the hydrological cycle and climate changes [15], [16], [17]. The 
combined measurements of the vector wind, water vapor, SST, and rain will also help to monitor tropical climate 
including tropical convection systems and cloud clusters, the intertropical convergence zone (ITCZ) [18], [19], 
[20], and the interannual climate anomalies of El Nino/Southern Oscillation (ENSO) [21], [22], [23], which also 
influences the mid- and high-latitude climate variations. Scientific impacts of the combined mission will further 
extend to studies concerning various phenomena of the atmosphere and ocean, such as monsoon [24], tropical 
cyclones [25], [26], ocean-atmosphere coupling mechanism [27] - [35], ocean’s response to wind and hydrologic 
forcing, and operational numerical weather prediction, and also to cryospheric studies and land applications.  
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AMSR AND DFS SYNERGY

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AMSR AND DFS SYNERGY

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