Latent heat

About: Latent heat is a research topic. Over the lifetime, 13503 publications have been published within this topic receiving 302811 citations.

Temporal and spatial variability of the surface energy balance in Dronning Maud Land, East Antarctica

Abstract: [1] We present data of nine Automatic Weather Stations (AWS), which are located in Dronning Maud Land (DML), East Antarctica, since the austral summer of 1997. Potential temperature and wind speed are maximum at the sites with the steepest surface slope, i.e., at the edge of the Antarctic plateau. Specific humidity and accumulation decrease with elevation and distance from the coast. The annual average energy gain at the surface from the downward sensible heat flux varies between ∼3 W m−2 and ∼25 W m−2, with the highest values at the sites with the largest surface inclination and wind speeds. The net radiative flux is negative and largely balances this sensible heat flux and ranges from ∼−2 W m−2 to ∼−28 W m−2; maximum values can be linked to maxima in surface slope and wind speed, and suggest a strong connection between the heat budget and the katabatic flow in DML. The average latent heat flux is generally small and negative (∼−1 W m−2) indicating a slight net mass loss through sublimation.

Interannual, seasonal and regional variations of precipitation and evaporation over the Baltic Sea

Abstract: Precipitation and evaporation rates over the Baltic Sea during the period 1981-1994 have been analyzed. The precipitation rate was based upon available meteorological weather, which were interpolated to grid paints using a two-dimensional objective analysis scheme, The evaporation rate was calculated using an ocean model, in which the Baltic Sea was treated as 13 sub-basins with high vertical resolution. Sea-surface temperatures as well as sea ice were calculated and verified extensively against temperature and ice-chart information, In the model, the latent heat flux was calculated according to a bulk formula parameterization. The evaporation rate was then calculated from the latent heat calculations and reduced by sea ice concentration, assuming that evaporation from sea ice is negligible. The long-term difference between precipitation and evaporation rates (the atmospheric fresh water inflow) is positive, which implies that the atmosphere adds fresh water to the Baltic Sea. For the period 1981 - 1994, the total mean atmospheric freshwater inflow was calculated to be 1986 m(3) s(-1). This is less than the total river runoff, but almost as large as the contribution from the River Neva, and thus an important source in the freshwater balance of the Baltic Sea. For the long time mean, the inclusion of sea ice increased (by reducing evaporation with 8%) the atmospheric freshwater inflow by 26% for the studied period, compared to an artificial case without ice in the Baltic Sea. The precipitation and evaporation over the Baltic Sea show, however, large interannual, seasonal and regional differences.

Modeling soil moisture: A Project for Intercomparison of Land Surface Parameterization Schemes Phase 2(b)

Abstract: In an intensive investigation of soil moisture simulation in land surface schemes, a number of numerical experiments was conducted with 14 representative schemes and the results compared with Hydrological and Atmospheric Pilot Experiment - Modelization du Bilan Hydrique (HAPEX-MOBILHY) data. The results show that soil moisture simulation in current land surface schemes varies considerably. After adjustment of land surface parameters, the disagreement in soil moisture for a 1.6-m soil layer remains around 100 mm. Correspondingly, the range of variation in predicted annual cumulative evaporation as well as total runoff plus drainage is around 250 mm (annual precipitation being 856 mm for HAPEX-MOBILHY). The partitioning of surface available energy into sensible and latent heat fluxes is closely coupled to the partition of precipitation into evaporation and runoff plus drainage. Although, on average, the range of variation in net radiation is about 8 W m−2, that of both the latent and sensible heat fluxes is twice as large. These disagreements are related to different causes but attempts to establish the link between the outcome and the responsible mechanism has had only limited success to date because of the complex interactions embedded in the schemes. This study implies that different schemes achieve different equilibrium states when forced with prescribed atmospheric conditions and that the time period to reach these states differs among schemes; and even when soil moisture is fairly well simulated, the processes (particularly evaporation and runoff plus drainage) controlling the simulation differ among schemes and at different times of the year. These results suggest that prescription of land surface scheme physics may have to be a function of the type of predictions (short-term weather forecasting, mesoscale modeling or climate ensembles) required as well as the underlying scheme formulation and that scheme simulations must be validated for all components of the prediction.