Surface energy balance of the NCEP MRF and NCEP-NCAR reanalysis in Antarctic latitudes during FROST

The surface energy budget in Antarctic latitudes is evaluated for the mediu m-range numerical weather forecasts produced by the National Centers for En vironmental Prediction (NCEP) and for the NCEP-National Center for Atmosphe ric Research reanalysis project during the winter, spring. and summer speci al observing periods (SOPs) of the Antarctic First Regional Observing Study of Troposphere project. A significant change in the energy balance resulte d from an extensive model update beginning with the forecasts initialized o n 11 January 1995 during the summer SOP. Both the forecasts and the reanaly sis include significant errors in the surface energy balance over Antarctic a. The errors often tend to cancel and thus produce reasonable surface temp erature fields. General errors include downward longwave radiation about 30 -50 W m(-2) too small. Lower than observed cloudiness contributes to this e rror and to excessive downward shortwave radiation at the surface. The mode l albedo over Antarctica, about 75%, is lower than that derived from observ ations, about 81%. During the polar day, errors in net longwave and net sho rtwave radiation tend to cancel. The energy balance over Antarctica in the reanalysis is, in general, degraded from that of the forecasts. Seasonal characteristics of the surface energy balance include cooling over East Antarctica and slight warming over West Antarctica during NCEP foreca sts for the winter SOP. Wintertime surface warming by downward sensible hea r Aux is larger than observations by 21-36 W m(-2) and tends to balance the excessive longwave cooling at the surface. During the spring SOP, forecast sensible heat flux Produces an excessive hearing contribution by about 20 W m(-2). Latent heat flux during the Antarctic winter for the reanalysis is at least an order of magnitude larger than the very small observed values.