SR/SSD 97-36

08-01-97

Technical Attachment

Changes to Operational (Early) and Meso Eta Models

Geoff DiMego

Environmental Modeling Center, NCEP

At 1200 UTC on July 29, 1997, a series of changes were implemented to the post-processed output from the NCEP operational Early Eta (48km/38levs) and Meso Eta (29km/50lev) models. Here is a brief description of the changes:

1. FOUS60-FOUS78 Output

The T3 and T5 values in the Eta FOUS messages were corrected to reflect temperatures at approximately the same pressure levels above the model terrain as those from the NGM FOUS. For example, T5 for the NGM FOUS is the temperature at sigma=.7848, about 215 mb above the model surface. The Eta T5 had been the temperature at 120-150 mb above the model terrain. The T3 temperature in the NGM FOUS is at sigma=.8967, about 100 mb above the model surface. In the Eta FOUS T3 was the temperature at 60-90 mb above the model surface.

2. Gridded Output

The codes which compute tropopause height have been modified to conform to the WMO definition of the tropopause height, and an error in the computation of cloud water on pressure surfaces in the Early Eta was corrected.

3. Hourly Station Profile Output

The station list used for hourly station output from the Eta model has been modified to reflect recent changes in rawinsonde station locations and to correct some errors:

ADDED DROPPED

72364 - Santa Teresa, NM 72270 - El Paso, TX

72376 - Flagstaff, AZ 72374 - Winslow, AZ

72426 - Wilmington, OH 72421 - Cincinnati, OH

72582 - Elko, NV 72576 - Lander, WY

72634 - Gaylord, ME 72583 - Winnemucca, NV

72672 - Riverton, WY

74389 - Gray, ME

74455 - Davenport, IA

The following stations were not being placed at the correct locations:

70308 - St. Paul Island, AK 71600 - Sable Island, NS

71201 - Key West, FL 91165 - Lihue, Kauai, HI (48 km Eta only)