Moisture structure of the quasi-biweekly mode revealed by AIRS in western Pacific |
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Authors: | Li Tao Xiouhua Fu Weisong Lu |
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Institution: | Key Laboratory of Meteorological Disaster of Ministry of Education,
Nanjing University of Information Science & Technology, Nanjing 210044;International Pacific Research Center, School of Ocean Science and Technology,
University of Hawaii, Honolulu, HI 96822;Key Laboratory of Meteorological Disaster of Ministry of Education,
Nanjing University of Information Science & Technology, Nanjing 210044 |
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Abstract: | Using Atmospheric Infrared Sounder (AIRS) humidity profiles, rainfall from the Tropical
Rainfall Measuring Mission (TRMM) Global Precipitation Index (GPI), Quick Scatterometer (QSCAT)
satellite-observed surface winds, and SST from the Advanced Microwave Scanning Radiometer for
NASA's Earth Observing System (AMSR_E), we analyzed the structure of the summer quasi-biweekly
mode (QBM) over the western Pacific in 2003--2004. We find that the signal of 10--20-day oscillations
in the western Pacific originates from the Philippine Sea, and propagates northwestward toward South
China. The AIRS data reveal that the boundary-layer moisture provides preconditioning for QBM propagation,
and leads the mid-troposphere moisture during the entire QBM cycle. The positive SST anomaly leads or
is in-phase with the boundary-layer moistening, and may be a major contributor. Most likely, the
10--20-day SST anomaly positively feeds back to the atmosphere by moistening the boundary layer,
destabilizing the troposphere, and leading the QBM to propagate northwestward in the western North
Pacific. However, the ECMWF/TOGA (Tropical Ocean and Global Atmosphere) analysis does not display
boundary-layer (BL) moisture anomalies leading the mid-troposphere moisture. |
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Keywords: | quasi-biweekly mode moisture structure Atmospheric Infrared Sounder |
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