Original Paper

Meteorology and Atmospheric Physics

, Volume 116, Issue 3, pp 63-79

First online:

Open Access This content is freely available online to anyone, anywhere at any time.

An upgraded version of the Eta model

  • Fedor MesingerAffiliated withEarth System Science Interdisciplinary Center (ESSIC), University of MarylandSerbian Academy of Sciences and Arts Email author 
  • , Sin Chan ChouAffiliated withINPE Center for the Weather Prediction and Climate Studies (CPTEC)
  • , Jorge L. GomesAffiliated withINPE Center for the Weather Prediction and Climate Studies (CPTEC)
  • , Dusan JovicAffiliated withNCEP Environmental Modeling Center
  • , Paulo BastosAffiliated withBrazilian Air Force
  • , Josiane F. BustamanteAffiliated withINPE Center for the Weather Prediction and Climate Studies (CPTEC)
  • , Lazar LazicAffiliated withInstitute of Meteorology, University of Belgrade
  • , André A. LyraAffiliated withINPE Center for the Weather Prediction and Climate Studies (CPTEC)
  • , Sandra MorelliAffiliated withDepartment of Physics, University of Modena and Reggio Emilia
    • , Ivan RisticAffiliated withWeather2Umbrella Co.
    • , Katarina VeljovicAffiliated withInstitute of Meteorology, University of Belgrade


Upgrades implemented over a number of years in an open source version of the Eta model, posted at the CPTEC web site http://​etamodel.​cptec.​inpe.​br/​, are summarized and examples of benefits are shown. The version originates from the NCEP’s Workstation Eta code posted on the NCEP web site http://​www.​emc.​ncep.​noaa.​gov/​mmb/​wrkstn_​eta, which differs from the NCEP’s latest operational Eta by having the WRF-NMM nonhydrostatic option included. Most of the upgrades made resulted from attention paid to less than satisfactory performance noted in several Eta results, and identification of the reasons for the problem. Others came from simple expectation that including a feature that is physically justified but is missing in the code should help. The most notable of the upgrades are the introduction of the so-called sloping steps, or discretized shaved cells topography; piecewise-linear finite-volume vertical advection of dynamic variables; vapor and hydrometeor loading in the hydrostatic equation, and changes aimed at refining the convection schemes available in the Eta. Several other modifications have to do with the calculation of exchange coefficients, conservation in the vertical diffusion, and diagnostic calculation of 10-m winds. Several examples showing improved performance resulting from the dynamics changes are given. One includes a case of unrealistically low temperatures in several mountain basins generated by a centered vertical advection difference scheme’s unphysical advection from below ground, removed by its replacement with a finite-volume scheme. Another is that of increased katabatic winds in the Terra Nova Bay Antarctica region. Successful forecast of the severe downslope zonda wind case in the lee of the highest peaks of the Andes is also shown, and some of the recent successful verification results of the use of the upgraded model are pointed out. The code is used at numerous places, and along with setup information it is available for outside users at the CPTEC Eta web site given above.