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Land surface temperature (LST) is an important element of the climate system. Remote sensing methods for estimating LST have been developed in the past and several of them have been implemented at large-scales. Geostationary satellites are of particular interest because they depict the diurnal cycle. Soil moisture has a strong effect on the magnitude of surface temperature via its influence on emissivity; yet, information on soil moisture at large scales is meager. It is of interest to estimate what effect soil moisture has on the retrieval accuracy of surface temperature by methods of remote sensing. In this study, newly developed algorithms to estimate land surface temperature (LST) from geostationary satellites will be applied to GOES-8 observations during the Southern Great Plains 1997 Hydrology Experiment (SGP-97) when surface observations of both soil moisture and surface temperature were made. The ground observations were used to first demonstrate the influence of soil moisture on the diurnal cycle of the surface temperature, its amplitude and the lag in LST maxima. Subsequently, it was established that errors in LST as derived from GOES-8 measurements have a negative correlation with soil moisture, namely, increasing with the decrease of soil moisture. 相似文献
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R. T. Pinker 《Boundary-Layer Meteorology》1983,26(3):305-311
During the TREND (Tropical Environmental Data) experiment conducted in Thailand, wind observations were made at several levels below and above a tropical forest canopy. These data allowed us to compute the widely used canopy coupling index and to study its dependence on ambient conditions. Our results indicate that the coupling between the above and below canopy flows depends primarily on stability and wind direction and to a lesser extent on the magnitude of the ambient wind speed. The coupling index as a function of the normalized height below the canopy was best described by exponential functions. 相似文献
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Christian Ferrarin Georg Umgiesser Andrea Cucco Tai-Wen Hsu Aron Roland Carl L. Amos 《Coastal Engineering》2008
Recognising the importance of understanding sediment dynamics to evaluate the status of a coastal lagoon environment, this work has been focused on the investigation of the hydrodynamic and sediment transport processes occurring in such basins. In order to describe the lagoon system, a modelling approach combining hydrodynamics, waves and sediment dynamics has been developed. The framework of the numerical model consists of a finite element hydrodynamic model, a third generation finite element spectral wave model and a sediment transport and morphodynamic model for both cohesive and non-cohesive sediments. The model adopts the finite element technique for spatial integration, which has the advantage to describe more accurately complicated bathymetry and irregular boundaries for shallow water areas. The developed model has been applied to test cases and to a very shallow tidal lagoon, the Venice Lagoon, Italy. Numerical results show good agreement with water level, waves and turbidity measurements collected in several monitoring stations inside the Lagoon of Venice. Such a model represents an indispensable tool in analysing coastal problems and assessing morphological impacts of human interference. 相似文献
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A detailed analysis is presented of the horizontal wind fluctuations with periods 20 s to 1 hr, and their vertical structure
as measured with light three-cup anemometers in a tropical forest environment. Information collected during the TREND (Tropical Environmental Data) experiment in a monsoon dominated region, was utilized. A special attempt was made to extract information relevant for
dispersion modeling. Variability parameters within and above the forest canopy under different stability conditions were derived.
A similar analysis was performed for a nearby clearing, to facilitate comparison between relatively smooth and rough surfaces,
under identical ambient conditions. A limited sample of data (7 days) was utilized, initially, to develop a methodology to
be later applied on a comprehensive data base, spanning the whole monsoon cycle. 相似文献
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Paul M. Winkler Anca Hienola Gerhard Steiner Gerard Hill Aron Vrtala Georg P. Reischl Markku Kulmala Paul E. Wagner 《Atmospheric Research》2008,90(2-4):187-ICNAA07
Heterogeneous nucleation of supersaturated n-nonane vapour on seed particles of different size and composition has been investigated using a fast expansion chamber. Monodisperse seed particle sizes were ranging from about 4 nm up to about 24 nm in diameter. By using different types of particle generators WOx, Ag and (NH4)2SO4 particles were generated. For direct comparison between different particle compositions overlapping sizes have been generated for WOx and Ag at about 7 nm particle diameter as well as for Ag and (NH4)2SO4 at about 15 nm. Nucleation temperature was kept constant at about 278 K. Experimental data were compared to Kelvin equation and Fletcher theory including the effect of line tension. It was found that heterogeneous nucleation of n-nonane seems to be independent of seed particle composition and starts well below the Kelvin curve. Good agreement was achieved with Fletcher theory including the effect of line tension. 相似文献
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The usefulness of the canopy flow index concept is demonstrated for a two-story evergreen tropical forest. A sample of about 2500 wind profiles was utilized. It encompasses a large range of ambient wind conditions and spans the whole monsoon cycle in Southeast Asia.It was found that the use of two canopy flow indices (one for the upper and one for the lower canopy) would be necessary to simulate the average canopy flow. For the upper canopy, an average value of 4.04 was obtained; for the lower canopy an index of 1.77 was computed. The indices seem to be independent of the ambient wind speed (if 2 m s-1 is exceeded), yet strongly dependent on wind direction. 相似文献
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The karsted limestone valleys of central Pennsylvania contain two populations of sinkholes. Solution sinkholes occur in the
Champlainian limestone units along the margins of the valleys. Solution sinkholes are permanent parts of the landscape and,
although a nuisance to construction, do not present other problems. The second population is the suffosional or soil-piping
sinkholes These occur on all carbonate rock units including the Beekmantown and Gatesburg dolomites that comprise the two
principal carbonate aquifers in the valley. Suffosional sinkholes are the principal land-use hazard.
Suffosional sinkholes are transient phonomena. They occur naturally but are exacerbated by runoff modifications that accompany
urbanization Suffosional sinkholes are typically 1.5–2.5 m in diameter depending on soil thickness and soil type. The vertical
transport of soil to form the void space and soil arch that are the precursors to sinkhole collapse is through solutionally
widened fractures and cross-joints and less often through large vertical openings in the bedrock. The limited solution development
on the dolomite bedrock combined with soil thickness, seldom greater than 2 m, limits the size of the sinkholes. All aspects
of suffosional sinkhole development are shallow processes: transport, piping, void and arch formation, and subsequent collapse
take place usually less than 10 m below the land surface
Factors exacerbating sinkhole development include pavement, street, and roof runoff which accelerates soil transport Such
seemingly minor activities as replacing high grass and brush with mowed grass is observed to accelerate sinkhole development.
Dewatering of the aquifer is not a major factor in this region 相似文献