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1.
The sensitivity of the development of the convective planetary boundary layer (PBL) and the surface layer are examined using a coupled surface parameterization and detailed PBL model. First, the coupling is verified against observations from the First ISLSCP (International Satellite Land Surface Climatology Project) Field Experiment (FIFE). Results of the sensitivity experiments indicate that the PBL is most sensitive to the amount of soil water content, and the proximity of the soil water content to critical soil texture values (field capacity and wilting point). While vegetation cover is not the most sensitive parameter at the surface, its influence on the surface energy and hydrologic balance is crucial. Model sensitivity to minimum stomatal resistance, type of soil parameterization and canopy height (surface roughness and displacement depth) is also discussed. 相似文献
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This paper describes a one-level variational adjustment process for producing mass-consistent surface winds in the Barrow Strait area, N.W.T. To achieve this result, the continuity equation is employed as a physical constraint. The variational technique adjusts mean winds (vertically averaged through the planetary boundary layer); therefore, a relationship is required between surface and mean winds. Use is made of existing velocity profiles, but interpolation may be used between surface and geostrophic winds. The model was found to be strongly dependent upon specification of boundary-layer height. Channeling effects are not readily seen until topography begins to protrude through the boundary layer. The model might thus be better suited to areas where shallow inversion layers are well defined. By application of the variational adjustment, errors in continuity are reduced by six orders of magnitude. Upon comparison of the variational technique with a diagnostic, one-level, primitive equation model, median errors between computed and observed surface winds were found to be comparable. 相似文献
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Sea-surface stress measurements were made from a rigid tower in shallow water near San Diego, California, by both the direct covariance and inertial dissipation techniques. Stress estimates from the dissipation technique were generally higher than the directly measured values, with average drag coefficients of 0.99 x 10-3 and 0.77 x 10-3, respectively, for 8-m wind speeds of 5 to 7 m s-1. In the inertial subrange, ratios of vertical to streamwise velocity spectra averaged 1.06 ± 0.16, significantly less than the isotropic value of 4/3 observed over land, suggesting that turbulence over water may be altered by the presence of waves. 相似文献
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A. Kh. Degterev 《Russian Meteorology and Hydrology》2007,32(7):461-464
The sea roughness effect on insolation and sun rays reflection for different sun heights above the horizon and unclouded sky is considered. Numerical assessments for albedo, insolation, and absorbed radiation are received for Stokes waves. Normal ray falling at the wave crest is suggested. The ray trace approach is used that allowed to take into account such effects as the dependence of albedo on the wave tilt, double light reflection from neighboring wave crests and the trough shading by the crest. It is concluded that the main roughness effect on the radiative balance is the insolation increasing and albedo diminishing at large wave steepness when the sun height above the horizon is less than 40°. 相似文献
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Routine surface wind speed data, vital for the study of drifting pack ice, are not available for the polar oceans. Over sea, it has been demonstrated by Hasse that estimates of surface wind speed may be obtained from the geostrophic wind speed using linear formulae. Comparing estimated with observed data for six sites in Canada, it is found that the formulae may also be applied to obtain estimates of surface wind speed over pack ice. 相似文献
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Radiometric surface temperatures, derived from measurements by the AVHRR instrument aboard the NOAA-9 and the NOAA-11 polar orbiting satellites, were used in combination with wind velocity and temperature profiles measured by radiosondes, to calculate surface fluxes of sensible heat. The measurements were made during FIFE, the First ISLSCP (International Satellite Land Surface Climatology Project) Field Experiment, in a hilly tall grass prairie area of northeastern Kansas. The method of calculation was based on turbulent similarity formulations for the atmospheric boundary layer. Good agreement (r = 0.7) was obtained with reference values of sensible heat flux, taken as arithmetic means of measurements with the Bowen ratio method at six ground stations. The values of evaporation (latent heat fluxes), derived from these sensible heat fluxes by means of the energy budget, were also in good agreement (r = 0.94) with the corresponding reference values from the ground stations. 相似文献
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A three-dimensional model of the mesoscale surface boundary layer of the open ocean is developed through scale analysis of the primitive equations with mixing included. A set of surface boundary-layer equations appropriate for a broad range of oceanic and atmospheric scales is thereby derived. The essential basis of the model is a coupling between quasigeostrophic dynamics away from the boundary layer and arbitrary mixing models within the mixed layer. The coupling consists of advection of the boundary layer by the horizontal and vertical components of the interior quasigeostrophic flow and forcing of the interior by the boundary layer in the form of divergence within the boundary layer which leads to vortex stretching/compression in the interior. The divergence is generalized for mesoscale wind-driven flows and includes nonlinear interaction between the directly wind-driven boundary-layer flow and the interior flow in the form of interior relative vorticity advection by the wind-driven flow. The nature of the equations leads us to apply a numerical algorithm to their solution. This algorithm is calibrated through application to idealized problems to determine the temporal and spatial grid requirements. The model is initialized with a realistic ocean flow having the properties of the Gulf Stream. 相似文献
11.
Measurements of the snow surface emissivity for infrared radiation have been made with an infrared radiation thermometer. The mean value of the emissivity is estimated at = 0.970 ± 0.008. 相似文献
12.
The complexity of inhomogeneous surface–atmosphere radiation transfer is one of the foremost problems in the field of atmospheric physics and atmospheric radiation. To date, the influence of surface properties on shortwave radiation has not been well studied. The daily downward surface shortwave radiation of the latest FLASHFlux/CERES(Fast Longwave And Shortwave Fluxes Time Interpolated and Spatially Averaged/Clouds and the Earth's Radiant Energy System) satellite data was evaluated against in situ data. The comparison indicated that the differences between the two data sets are unstable and large over rugged terrain compared with relatively flat terrain, and the mean absolute error of the satellite products reaches 31.4 W m-2(12.3%) over rugged terrain. Based on the SSF(single satellite footprint)/CERES product, the influence of surface properties on the distribution of downward surface shortwave radiation(DSSR) was analyzed. The influence of surface properties on DSSR over the Tibetan Plateau is about twice as large as that in two other regions located at the same latitude(eastern China–western Pacific and subtropical North Pacific). A simulation was carried out with the help of the I3RC(International Intercomparision of Three-Dimensional Radiation Code) Monte Carlo 3D radiative transfer community model. The results showed that DSSR increases as surface albedo increases. Moreover, the impact of surface albedo on DSSR is larger if the spatial distribution of clouds is more non-uniform. It is hoped that these results will contribute to the development of 3D radiative transfer models and the improvement of satellite inversion algorithms. 相似文献
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Drag of the sea surface 总被引：6，自引：1，他引：6
It is shown how the drag of the sea surface can be computed from the wind speed and the sea state. The approach, applicable both for fully developed and for developing seas, is based on conservation of momentum in the boundary layer above the sea, which allows one to relate the drag to the properties of the momentum exchange between the sea waves and the atmosphere.The total stress is split into two parts: a turbulent part and a wave-induced part. The former is parameterized in terms of mixing-length theory. The latter is calculated by integration of the wave-induced stress over all wave numbers. Usually, the effective roughness is given in terms of the empirical Charnock relation. Here, it is shown how this relation can be derived from the dynamical balance between turbulent and wave-induced stress. To this end, the non-slip boundary conditions is assigned to the wave surface, and the local roughness parameter is determined by the scale of the molecular sublayer.The formation of the sea drag is then described for fully developed and developing seas and for light to high winds.For the Charnock constant, a value of about 0.018–0.030 is obtained, depending on the wind input, which is well within the range of experimental data.It is shown that gravity-capillary waves with a wavelength less than 5 cm play a minor role in the momentum transfer from wind to waves. Most of the momentum is transferred to decimeter and meter waves, so that the drag of developing seas depends crucially on the form of the wave spectrum in the corresponding high wavenumber range.The dependence of the drag on wave age depends sensitively on the dependence of this high wavenumbertail on wave age. If the tail is wave-age independent, the sea drag appears to be virtually independent of wave age. If the tail depends on wave age, the drag also does. There is contradictory evidence as to the actual dependence. Therefore, additional experiments are needed.The investigation was in part supported by the Netherlands Geosciences Foundation (GOA) with financial aid from the Netherlands Organization for Scientific Research (NWO). 相似文献
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B. G. Sherstyukov 《Russian Meteorology and Hydrology》2017,42(4):213-221
The index of inertance of surface temperature variations is proposed which supposedly reflects the damping effect of the ocean on the variations in atmospheric thermal conditions over the land. It is demonstrated that the climate variability and climate change are related to the index of inertance. Air temperature rose most intensively in the years of weak stabilizing effect of the ocean which restrains the climate warming. The general trend of the inertance weakening on the land in the second half of the 20th century led to the additional and more rapid warming and to the increase in climate extremity on the continents. 相似文献
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Estimation of areally-averaged surface fluxes 总被引：6，自引：1，他引：6
Martin Claussen 《Boundary-Layer Meteorology》1991,54(4):387-410
The concept of blending height is used to estimate areally averaged surface fluxes of momentum and heat in a stratified, horizontally inhomogeneous surface-layer flow. This concept is based on the assumption that at sufficiently large heights above a heterogeneous surface, subsequent surface modifications will not be recognizable in the flow individually, but overall flux and mean profiles will represent the surface condition of a large area. The height at which the flow becomes approximately independent of horizontal position is called blending height according to Wieringa (1986).Here, it is proposed to classify the ground surface in a surface-layer grid box of a larger-scale model into several land-use categories. Surface momentum and heat fluxes should be estimated for each category at the blending height. The grid-averaged surface fluxes are to be obtained by the average of surface fluxes on each land-use surface weighted by its fractional area. The postulate of computing the surface fluxes at the blending height leads to a new formulation of turbulent transfer coefficients.The proposed parameterization has been tested by employing a small-scale numerical model as a surface-layer grid box of a hypothesized larger-scale model. Several quite different flow configurations have been studied in order to investigate the performance of the new parameterization. Generally, the relative errors of estimated averaged surface fluxes are found to be well within ±10%. 相似文献
17.
Temperature above the surface layer 总被引：1，自引：0，他引：1
John R. Christy 《Climatic change》1995,31(2-4):455-474
Three published data sets of upper-air global temperatures, two from radiosondes and one from satellites, are examined and compared for the lower stratosphere and troposphere.The global lower stratosphere exhibits a downward trend for the past 16+ years of -0.53 °C (-0.33 °C per decade). Since the 1960's (using radiosondes before 1979 which are subject to known and unknown inhomogeneities) it is likely that there has been a downward trend of about the same magnitude. Significant issues of the stratospheric radiosonde data are: (1) that the long-term time series is biased toward spurious cooling; and (2) the earliest years of Angell display unrealistic variability. Inhomogeneities in satellite data due to orbit drifting and instrument calibration are examined.The tropospheric temperature has shown a downward trend of -0.11 °C since 1979 (-0.07 °C per decade). Beginning in earlier years, (relying only on radiosonde data before 1979) the estimated warming trend since the late 1950's is +0.07 to +0.11 °C per decade.Tropospheric and surface temperature anomalies are compared. There is concern that the disproportionate representation of extratropical continents, with their high temperature variance, may bias any long term global surface trend toward a maximum-possible value than would be calculated had all regions (including those with much lower responsiveness) been monitored. 相似文献
18.
Using data collected during 1975–1976 from a meteorological network operating in the vicinity of the Columbia Generating Site approximately 8 km south of Portage, Wis., the influence of the Baraboo Hills on the surface wind field is determined. Half-hour means of wind speed and direction measured at 9 m at three sites were used to compute divergence and vorticity using Bellamy's method. The data were grouped into 18 sectors each 20 deg wide and averages computed for each quantity. Results indicate that for wind directions perpendicular to the eastern edge of the Baraboo Hills, the surface (9m) wind field is significantly perturbed up to 4 km from the bluffs. The largest convergence of 2.1 × 10–4 s–1 occurs with 160 deg wind direction and the largest divergence of 1.2 × 10–4 s–1 with 290 deg wind direction. The maximum anticyclonic vorticity was 1.6 × 10–4 s–1 at 210 deg and the maximum cyclonic vorticity was 1.6 × 10–4 s–1 at 330 deg. 相似文献
19.
Yu. P. Perevedentsev A. A. Vasil’ev K. M. Shantalinskii V. V. Gur’yanov 《Russian Meteorology and Hydrology》2017,42(7):461-470
The spatiotemporal variability of surface air pressure and surface air temperature in the Northern Hemisphere troposphere in 1990-2014 is described. In 2005 the low-frequency component (LFC) of average air temperature in January averaged over the latitude zone of 32.5°-67.5° N has stopped its increase that lasted for 35 years (from 1970). The LFC of air temperature in July has continued growing since 1975 (for 39 years). The anomalies of air pressure and air temperature for thirty-year periods and the dynamics of LFC of air temperature and air pressure in the atmospheric centers of action are analyzed. 相似文献
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《Atmospheric Science Letters》2001,2(1-4):81-85
The radiative impact of greenhouse gases in warming the Earth varies significantly, depending on whether one considers the forcing at the tropopause or at the surface. Compared to the former, the surface forcing for some greenhouse gases is reduced by the interference of water vapour. Hence, we calculate alternative surface global warming potentials (SGWPs) that are derived from the surface forcing radiation of greenhouse gases for potential use in surface radiative energy balance models (SREBMs). For gases with a large water vapour overlap, the SGWPs are typically 30% smaller than current GWPs; for gases with relatively little overlap, the SGWPs are larger by more than 33%. These results may be used in conjunction with SREBMs as an additional means of calculating climate change, and may lead to an altered emissions budget compared to that outlined by the current Kyoto agreement. 相似文献