Evaluation of a forward operator to assimilate cloud water path into WRF-DART

Thomas A. Jones, David J. Stensrud, Patrick Minnis, Rabindra Palikonda

Research output: Contribution to journalArticlepeer-review

26 Scopus citations

Abstract

Assimilating satellite-retrieved cloud properties into storm-scale models has received limited attention despite its potential to provide a wide array of information to a model analysis. Available retrievals include cloud water path (CWP), which represents the amount of cloud water and cloud ice present in an integrated column, and cloud-top and cloud-base pressures, which represent the top and bottom pressure levels of the cloud layers, respectively. These interrelated data are assimilated into an Advanced Research Weather Research and Forecasting Model (ARW-WRF) 40-member ensemble with 3-km grid spacing using the Data Assimilation Research Testbed (DART) ensemble Kalman filter. A new CWP forward operator combines the satellite-derived cloud information with similar variables generated by WRF. This approach is tested using a severe weather event on 10 May 2010. One experiment only assimilates conventional (CONV) observations, while the second assimilates the identical conventional observations and the satellite-derived CWP (PATH). Comparison of theCWPobservations at 2045 UTC to CONVand PATHanalyses shows that PATHhas an improved representation of both the magnitude and spatial orientation of CWP compared to CONV. Assimilating CWP acts both to suppress convection in the model where none is present in satellite data and to encourage convection where it is observed. Oklahoma Mesonet observations of downward shortwave flux at 2100 UTC indicate that PATH reduces the root-mean-square difference errors in downward shortwave flux by 75Wm22 compared to CONV. Reduction in model error is generally maximized during the initial 30-min forecast period with the impact of CWP observations decreasing for longer forecast times.

Original languageEnglish (US)
Pages (from-to)2272-2289
Number of pages18
JournalMonthly Weather Review
Volume141
Issue number7
DOIs
StatePublished - 2013

All Science Journal Classification (ASJC) codes

  • Atmospheric Science

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