18D.2
Improving Forecasts of Asian Monsoon Rainfall Using COSMIC Radio Occultation Refractivity Observations
Hui Liu, NCAR, Boulder, CO; and J. Anderson, B. Kuo, G. X. Wu, C. Snyder, and Y. Chen
Monsoon rainfall is very important for the economy of Asia but its
prediction is still not satisfactory. One reason is a lack of
good observations of the subtropical high over the
Western Pacific ocean.
The newly available COSMIC GPS radio occultation (RO) refractivity
soundings provide good coverage globally including the Western
Pacific ocean. The measurements contain valuable water vapor and
temperature information with high vertical resolution in the lower
troposphere and are not contaminated by clouds or precipitation.
The DART/WRF ensemble filter/prediction system is used to examine
the impact of COSMIC GPS refractivity
observations on forecasts of heavy monsoon rainfall during June
1-14, 2007. Radiosondes,
AIRS retrieved temperature, and satellite cloud/water vapor drift
winds are assimilated using WRF with a 36 km resolution for
the period of June 1-14, 2007 in a control case. A comparison is
made to an assimilation using all of these observations plus GPS
RO data. Assimilating the GPS
RO data leads to a better defined analysis of the subtropical high
and its circulation and significantly reduces the bias of the water vapor
analysis over eastern Asia. Forecasts of the heavy monsoon
rainfall events are significantly improved by adding the GPS RO
refractivity observations.
Recorded presentationSession 18D, Monsoons II
Friday, 2 May 2008, 10:15 AM-12:00 PM, Palms I
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