[Wrfems] Use of LSMDSET/LSM in EMSv2/3

Case, Jonathan (MSFC-VP61)[Other] jonathan.case-1 at nasa.gov
Wed Sep 16 11:38:59 MDT 2009

Dear WRF EMS users,

I have a general question on the use of the LSMDSET/LSM settings in the wrf_autorun.conf/ems_autorun.conf files for EMS v2/3, respectively.  I have been under the impression that this option is only necessary when using an initialization dataset that does not have land surface fields present (i.e. LAPS analyses). If LAPS is not used and the LSM option is left blank, then I thought the WRFSI/WPS pre-processor would use LSM fields from the model being used for ICs/BCs.  For example, if we initialized the model at 03z with the 00z NAM and left LSM blank, then the EMS should simply use the 3-h NAM forecasts of the LSM fields to interpolate the data to the WRF grid.  

However, I stumbled upon some different behavior in WRF forecasts.  In EMS v2, I re-ran some cases with and without the LSMDSET option set in wrf_autorun.conf.  It showed up with different results at some verification sites -- most notably in the first few forecast hours at night for a 03z initialization time. The differences were substantial at some locations -- on the order of a couple degrees C.  So, it seems to me that there may be different LSM fields being used based on whether LSMDSET is set or not (at least in v2).  


Jonathan Case, ENSCO Inc.
NASA Short-term Prediction Research and Transition Center (aka SPoRT Center)
320 Sparkman Drive, Room 3062
Huntsville, AL 35805
Voice: 256.961.7504
Fax: 256.961.7788
Emails: Jonathan.Case-1 at nasa.gov / case.jonathan at ensco.com

"Whether the weather is cold, or whether the weather is hot, we'll weather 
  the weather whether we like it or not!"

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