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Summary
Discharge from a small grassland catchment in Ireland is simulated with the atmospheric land-surface scheme SEWAB. Hydrological
processes are parameterized to represent surface runoff and baseflow generation and soil moisture storage changes. Surface
ponding and infiltration are explicitly described in order to account for the rapid response of streamflow to precipitation
events. The annual discharge, the evapotranspiration and individual flood flows are accurately modelled. The simulation of
soil moisture at various depths is close to the observations from time domain reflectometer measurements. An analysis of the
significance of individual hydrological processes for discharge simulation from the small catchment found the ponding process
to be essential for time periods of less than 12 hours. A depth dependent saturation hydraulic conductivity improves the simulations
on all time scales.
Received October 25, 2000/Revised February 16, 2001 相似文献
2.
Evaporation over a Heterogeneous Land Surface: EVA_GRIPS and the LITFASS-2003 Experiment—An Overview
The Evaporation at Grid/Pixel Scale (EVA_GRIPS) project was realised in order to determine the area-averaged evaporation over a heterogeneous land surface at the scale of a grid box of a regional numerical weather prediction or climate model, and at the scale of a pixel of a satellite image. EVA_GRIPS combined surface-based and airborne measurements, satellite data analysis, and numerical modelling activities. A mesoscale field experiment, LITFASS-2003, was carried out in the heterogeneous landscape around the Meteorological Observatory Lindenberg (MOL) of the German Meteorological Service in May and June, 2003. The experiment was embedded in the comprehensive, operational measurement program of the MOL. Experimental determination of surface fluxes on a variety of spatial scales was achieved by employing micrometeorological flux stations, scintillometers, a combination of ground-based remote sensing instruments, and the Helipod, a turbulence probe carried by a helicopter. Surface energy fluxes were also derived from satellite data. Modelling work included the use of different Soil–Vegetation–Atmosphere Transfer schemes, a large-eddy simulation model and three mesoscale atmospheric models. The paper gives an overview on the background of EVA_GRIPS, and on the measurements and meteorological conditions during LITFASS-2003. A few general results are discussed. 相似文献
3.
H.-T. Mengelkamp 《Theoretical and Applied Climatology》1999,63(3-4):129-139
Summary A statistical-dynamical downscaling procedure is applied to investigate the climatological wind field over a complex terrain
area in central Germany. The model domain, 80×87 km, is dominated by flat terrain in the westerly and northerly part and encompasses
the Teuteburger Wald and the Wiehengebirge areas with hills up to 330 m a.m.s.l. in the southeasterly region. The downscaling
procedure combines a large-scale regionally representative wind statistic and a high-resolution numerical atmospheric mesoscale
model. A cluster analysis of a 12-years time series of radiosonde data provides 143 clusters each being a combination of the
geostrophic wind components and the vertical temperature gradient. These parameter sets constitute the reference state for
highly-resolved steady-state wind field simulations with a non-hydrostatic model. Weighting the resulting wind fields with
the corresponding cluster frequency gives climatologically representative frequency distributions of the wind speed and -direction.
By combining the wind speed frequency distribution with the power curve of wind turbines the yearly energy output of 46 wind
turbines inside the simulation domain was calculated and compared to the actual production. No bias or systematic trend in
the deviation was found. The relative differences for the smallest turbines reach 100 percent with a decreasing tendency to
larger units.
Received November 13, 1998 相似文献
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Heinz -Theo Mengelkamp 《Boundary-Layer Meteorology》1991,57(4):323-341
A three-dimensional, non-hydrostatic mesoscale model is used to study boundary-layer structure over an area characterized by the city of Copenhagen, the Øresund strait, and adjacent coastal farmland. Simulations are compared with data obtained on June 5, 1984 during the Øresund experiment.Under moderately strong wind conditions, a stable internal boundary layer (IBL) developed over the Øresund strait during the day. Near-surface winds decelerate over water due to diminished vertical momentum transfer.The turbulent kinetic energy field closely reflects the surface roughness distribution due to the imposed relatively strong wind forcing. TKE budgets over water, farmland and a city area are discussed by inspection of vertical profiles of the individual terms. The buoyancy term is used to indicate IBL heights because it changes sign at the boundary between different stability regimes. Measured and simulated dissipation rates show a decrease in the transition zone as the air travels over water and an abrupt increase when the IBL over a downwind city area is intersected. The top of the stable IBL is characterized by a minimum in the vertical TKE profile. 相似文献
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Summary The land surface model SEWAB (Surface Energy and Water Balance) is designed to be coupled to both, atmospheric and hydrological
models. Its application in mid and high latitudes requires the inclusion of freezing and thawing processes within the soil
and the accumulation and ablation of a snow cover. These winter processes are parameterised with a minimum number of empirical
formulations in order to assure reasonable computation times for an application in climate and sensitivity studies yet accounting
for all important processes. Meteorological forcing data and measurements of snow depth, soil temperature and liquid soil
water content at two locations in the mid-west of North America are used to test the model. Generally the simulated snow depth
matches the measurements, remaining differences in snow depth can be explained by uncertainties in snow density, blowing snow
and errors in precipitation measurements. The simulated soil temperature and liquid soil water content compare well with the
measurements, showing the isolating effect of the snow cover.
Received August 25, 2000 Revised January 19, 2001 相似文献
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