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Surface Radiation (surface + radiation)

Distribution by Scientific Domains

Earth and Environmental Science	50%

Selected Abstracts

Local hydrologic effects of introducing non-native vegetation in a tropical catchment

ECOHYDROLOGY, Issue 1 2008
Maite Guardiola-Claramonte
Abstract This study investigates the hydrologic implications of land use conversion from native vegetation to rubber (Hevea brasiliensis) in Southeast Asia. The experimental catchment, Nam Ken (69 km2), is located in Xishuangbanna Prefecture (22°N, 101°E), in the south of Yunnan province, in southwestern China. During 2005 and 2006, we collected hourly records of 2 m deep soil moisture profiles in rubber and three native land-covers (tea, secondary forest and grassland), and measured surface radiation above the tea and rubber canopies. Observations show that root water uptake of rubber during the dry season is controlled by day-length, whereas water demand of the native vegetation starts with the arrival of the first monsoon rainfall. The different dynamics of root water uptake in rubber result in distinct depletion of soil moisture in deeper layers. Traditional evapotranspiration and soil moisture models are unable to simulate this specific behaviour. Therefore, a different conceptual model, taking in account vegetation dynamics, is needed to predict hydrologic changes due to land use conversion in the area. Copyright © 2008 John Wiley & Sons, Ltd. [source]

A parallel Galerkin boundary element method for surface radiation and mixed heat transfer calculations in complex 3-D geometries

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 12 2004
X. Cui
Abstract This paper presents a parallel Galerkin boundary element method for the solution of surface radiation exchange problems and its coupling with the finite element method for mixed mode heat transfer computations in general 3-D geometries. The computational algorithm for surface radiation calculations is enhanced with the implementation of ideas used for 3-D computer graphics applications and with data structure management involving creating and updating various element lists optimized for numerical performance. The algorithm for detecting the internal third party blockages of thermal rays is presented, which involves a four-step procedure, i.e. the primary clip, secondary clip and adaptive integration with checking. Case studies of surface radiation and mixed heat transfer in both simple and complex 3-D geometric configurations are presented. It is found that a majority of computational time is spent on the detection of foreign element blockages and parallel computing is ideally suited for surface radiation calculations. Results show that the decrease of the CPU time approaches asymptotically to an inverse rule for parallel computing of surface radiation exchanges. For large-scale computations involving complex 3-D geometries, an iterative procedure is a preferred approach for the coupling of the Galerkin boundary and finite elements for mixed mode heat transfer calculations. Copyright © 2004 John Wiley & Sons, Ltd. [source]

The surface radiation budget over North America: gridded data assessment and evaluation of regional climate models

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 15 2009
Marko Markovic
Abstract While surface station observations of downwelling radiation offer accuracy at high temporal resolution, they do not easily allow an evaluation of model surface radiation budgets (SRB) over a wide geographical area. We evaluate three gridded SRB data sets against detailed observations from six surface radiation sites from the US surface radiation (SURFRAD) network. We subsequently use the most accurate surrogate observational data set for evaluation of model-simulated SRB. The data sets assessed are: ERA40,reanalysis of European Centre for Medium-Range Weather Forecasts (ECMWF), North American Regional Reanalysis (NARR),regional reanalysis of National Centres for Environmental Prediction (NCEP) and the surface radiative budget (SRB) from the International Satellite Cloud Climatology Project (ISCCP). Due to varying constraints with respect to temporal coverage of each data set, the evaluation period used in this study is 1996,2001, inclusive. The ERA40 downwelling longwave radiation (DLR) appears the most accurate surrogate observation, while both ERA40 and ISCCP show accurate results when the incoming shortwave radiation (ISR) is considered across the annual cycle. Winter DLR is less accurate in ISCCP with a positive bias and lack of very low (<200 Wm,2) flux values. The NARR SRB shows a large positive bias in the ISR throughout the annual cycle, linked to a significant underestimate of cloud cover. The ERA40 data are subsequently used to evaluate the simulated SRB in three regional climate models across North America. With respect to solar radiation, cloud cover biases are seen to be crucial, while for longwave fluxes both cloud fraction and in-cloud water content are important to simulate correctly. Inclusion of trace gases beyond H2O, CO2 and O3 appears necessary for an accurate calculation of clear-sky longwave radiation. Error compensation frequently occurs between the various components contributing to a model total-sky SRB. This is important to consider when trying to identify the underlying causes of errors in the simulated total SRB. Copyright © 2009 Royal Meteorological Society [source]

Rigorous modeling of UV absorption by TiO2 films in a photocatalytic reactor

AICHE JOURNAL, Issue 7 2000
Z. Zhang
The radiation absorption profiles on the surfaces of TiO2 films in a corrugated-plate photocatalytic reactor were modeled based on first principles. A new term, the local-area-specific rate of energy absorption (LASREA), was adopted to describe the catalyst surface radiation in heterogeneous photoreactors. The LASREA and the energy absorption efficiency were both quite sensitive to the dimensions of the corrugated plates. Due to the multiple photon reflections between the opposing surfaces, corrugated plates possess a superior capability for recapturing longer wavelength photons that would otherwise be reflected out of some reactor designs. This results in higher energy absorption efficiency and more uniform LASREA on the catalyst films. Compared to a flat plate, corrugations are predicted to enhance the energy absorption efficiency by up to 50% for UV-A fluorescent-lamp-powered systems and more than 100% for solar-powered systems. [source]

Soil state and surface hydrology diagnosis based on MOSES in the Met Office Nimrod nowcasting system

METEOROLOGICAL APPLICATIONS, Issue 2 2006
R. N. B. Smith
Abstract A system has been developed and made operational at the Met Office for the real-time diagnosis of soil state and surface hydrology. It is based on the Met Office Surface Exchanges Scheme (MOSES) modified to take account of unresolved soil and topographic heterogeneity when calculating surface runoff by incorporating a Probability Distributed Moisture (PDM) scheme developed by the Centre for Ecology and Hydrology. The implementation of MOSES-PDM in the Met Office's Nimrod nowcasting system is described. High resolution soil characteristics and land cover data, together with Nimrod's analyses of precipitation amount and type, cloud cover and near-surface atmospheric variables are used to drive MOSES-PDM. Hourly values of snowmelt, runoff, net surface radiation, evaporation, potential evaporation, soil temperature, soil moisture and soil moisture deficit are calculated on a 5 km grid. Copyright © 2006 Royal Meteorological Society. [source]