Assimilation of NCEP multi-sensor hourly rainfall data using 4D-Var approach: A case study of the squall line on April 5, 1999 |
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| Authors: | S Q Peng X Zou |
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| Institution: | (1) Florida State University, Tallahassee, Florida, USA, US |
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| Abstract: | Summary ?NCEP multi-sensor hourly rainfall data were used for data assimilation and evaluation of quantitative precipitation forecasts
(QPFs) through a case study of a squall line on April 5, 1999. Improvements in QPFs were obtained through direct assimilation
of these rainfall observations using 4-dimensional variational assimilation (4D-Var). Inclusion of the observed no-rain information
was shown to be beneficial to QPFs. While the penalty constraint applying a digital filter was effective in removing high
frequency oscillations introduced by rainfall assimilation and produced a smoother “optimal” initial condition, its impact
on QPFs is mixed. Sensitivity studies indicated that the adjustments in the moisture and temperature fields resulted from
precipitation assimilation played a more important role than those of other state variables for improving QPFs.
Received October 27, 2001; accepted January 30, 2002 |
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