On the Relationship between Clear-Sky Planetary and Surfae Albedos

Chen, T. S.; Ohring, George

doi:10.1175/1520-0469(1984)041<0156:otrbcs>2.0.co;2

Cited by 64 publications

(23 citation statements)

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“…where S in is the incoming short wave radiation (W m 2 ), L in is the incoming long wave radiation (W m 2 ), L out is the outgoing long wave radiation (W m 2 ), r is the surface albedo, which can be retrieved from Band 1, 2, 3, 4, 5, and 7 of Landsat5 TM (Chen and Ohring, 1984;Koepke et al, 1985;Bastiaanssen et al, 1998a;Bastiaanssen, 2000;Wang et al, 2000), ε is the surface emissivity, which can be estimated by the Normal Difference Vegetation Index (NDVI) retrieved from the red and near infrared bands using semi-empirical relationships ( Van de Griend and Owe, 1993;Bastiaanssen et al, 1998a), T sur is the surface temperature (K), which can be retrieved by the thermal infrared band, Band 4853 6 of Landsat5 TM (Bastiaanssen, 2000;Chander and Markham, 2003). The atmospheric emissivity ε a can be estimated from atmospheric temperature and humidity (Brutsaert, 1975), is the Stefan-Boltzman constant (5Ð67 ð 10 8 W m 2 K 4 ).…”

Section: Model Similaritiesmentioning

confidence: 85%

Intercomparison of remote sensing‐based models for estimation of evapotranspiration and accuracy assessment based on SWAT

Gao

Long

2008

Hydrological Processes

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Abstract:An intercomparison of daily actual evapotranspiration (ET) estimates from the single-source models (SEBAL and SEBS) and the two-source models (P-TSEB and S-TSEB) using remotely sensed data was performed to examine their utilities and limitations under a wide range of land covers and different meteorological conditions. The accuracy of ET estimates from remote sensing-based models of a selected watershed on 23 June 2005 (DOY 174) presenting large air drying power and marked contrast in underlying surface characteristics, and 25 July 2005, (DOY 206) in contrast to the meteorological and underlying surface conditions of DOY 174, were evaluated in terms of SWAT-based ET. The ET estimates from the two methodologies are shown to be comparable, indicating that S-TSEB has the highest accuracy with relative errors of 2Ð2% and 5Ð6% with reference to SWAT-based ET for DOY 174 and 206, respectively. Hence it was selected to be the basis for performing an intercomparison with other remote sensing-based models. Single-source models are very sensitive to KB 1 parameter, rendering marked differences in ET estimates because of different treatments of roughness length for heat transfer. SEBAL and SEBS yielded mean absolute percentage difference (MAPD) versus S-TSEB within 26Ð22% and 26Ð56% for DOY 174 and within 9Ð11% and 11Ð69% for DOY 206, respectively, indicating their applicability to higher vegetation cover and soil moisture availability areas under small air drying power condition. P-TSEB generated MAPD versus S-TSEB within 41Ð15% for DOY 174 and 8Ð79% for DOY 206, implying that P-TSEB is highly consistent with S-TSEB under small air drying power and less contrast in soil moisture conditions, whereas noticeable discrepancies occur under large air drying power and marked contrast in soil moisture circumstances, in particular for sparse cover. The performance of P-TSEB largely depends on the meteorological and underlying surface conditions, both exerting significant influences on the extent of coupling between vegetation and soil.

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Section: Model Similaritiesmentioning

confidence: 85%

Intercomparison of remote sensing‐based models for estimation of evapotranspiration and accuracy assessment based on SWAT

Gao

Long

2008

Hydrological Processes

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“…For surface albedo changes, the linear relationship with planetary albedo changes, Eq. (4), is supported by the results of radiative transfer models (Chen and Ohring, 1984;Li and Garand, 1994). Under a clear-sky, f a represents the mean effective "two-way" transmittance of the atmosphere:…”

Section: Shortwave Optionsmentioning

confidence: 99%

“…From the clear-sky results of a radiative transfer model (Lacis and Hansen, 1974), f a =0.730 (T a =0.854) in the annual global mean, similarly for a fixed solar zenith angle of 60 • f a =0.729, and two different sets of observational data give f a =0.756 and f a =0.676 (Chen and Ohring, 1984). A different radiative transfer model that additionally includes aerosols and variation in the albedo of some surfaces with solar zenith angle gives comparable clear-sky results (Li and Garand, 1994) (e.g.…”

Section: Shortwave Optionsmentioning

confidence: 99%

The radiative forcing potential of different climate geoengineering options

2009

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Abstract. Climate geoengineering proposals seek to rectify the Earth's current and potential future radiative imbalance, either by reducing the absorption of incoming solar (shortwave) radiation, or by removing CO 2 from the atmosphere and transferring it to long-lived reservoirs, thus increasing outgoing longwave radiation. A fundamental criterion for evaluating geoengineering options is their climate cooling effectiveness, which we quantify here in terms of radiative forcing potential. We use a simple analytical approach, based on energy balance considerations and pulse response functions for the decay of CO 2 perturbations. This aids transparency compared to calculations with complex numerical models, but is not intended to be definitive. It allows us to compare the relative effectiveness of a range of proposals. We consider geoengineering options as additional to large reductions in CO 2 emissions. By 2050, some land carbon cycle geoengineering options could be of comparable magnitude to mitigation "wedges", but only stratospheric aerosol injections, albedo enhancement of marine stratocumulus clouds, or sunshades in space have the potential to cool the climate back toward its pre-industrial state. Strong mitigation, combined with global-scale air capture and storage, afforestation, and bio-char production, i.e. enhanced CO 2 sinks, might be able to bring CO 2 back to its pre-industrial level by 2100, thus removing the need for other geoengineering. Alternatively, strong mitigation stabilising CO 2 at 500 ppm, combined with geoengineered increases in the albedo of marine stratiform clouds, grasslands, croplands and human settlements might achieve a patchy cancellation of radiative forcing. Ocean fertilisation options are only worthwhile if susCorrespondence to: T. M. Lenton (t.lenton@uea.ac.uk) tained on a millennial timescale and phosphorus addition may have greater long-term potential than iron or nitrogen fertilisation. Enhancing ocean upwelling or downwelling have trivial effects on any meaningful timescale. Our approach provides a common framework for the evaluation of climate geoengineering proposals, and our results should help inform the prioritisation of further research into them.

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“…The planetary albedo can be estimated with the reflectance of visible and nearinfrared channel of AVHRR (Chen and Ohring 1984): r p ¼ 0:035 þ 0:545CH 1 þ 0:32CH 2 , where CH 1 and CH 2 represent the reflectance of AVHRR Channels 1 and 2, respectively. Surface emissivity is a function of the Normalized Di¤erence Vegetation Index NDVI , and the inversion model is (van de Griend et al 1993)…”

Section: Surface Net Radiation Flux R Nmentioning

confidence: 99%

Comparative Analysis of Satellite Remotely-Sensed Surface Energy Flux and Ground-Based Observation in the Sichuan Basin

Wang

et al. 2012

Journal of the Meteorological Society of Japan

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Integrating the clear-sky NOAA/AVHRR satellite data with station meteorological observations, we conduct a remote sensing estimation of surface energy fluxes of the Sichuan Basin based on surface energy balance. The correlation between the estimation of satellite pixel and the ground-based observed value of Wenjiang Atmospheric Boundary Layer Observation Station is analyzed to verify the satellite remotely-sensed surface energy flux. Result indicates that the distributions of satellite remotely-sensed surface energy fluxes are consistent with those of the underlying surface. There exist remarkable positive correlations among the satellite-estimated net radiation flux, soil heat flux, sensible heat flux, and the ground-based observed values of key components. All correlation coe‰cients significantly exceed 0.9. Hence, the remotely-sensed estimations of net radiation flux, soil heat flux, and sensible heat flux are reliable to a certain extent. Since the surface energy balance at Wenjiang test site is usually unclosed, the correlation coe‰cient between the satellite pixel latent heat flux estimated by surface energy balance method and the value measured by eddy covariance method of the key components is only 0.717. If the unclosed value of surface energy balance is taken into consideration, the correlation coe‰-cient increases to 0.945, meaning that the deviation between the two decreases obviously. It is thus unadvisable to use the residual of surface energy balance equation to estimate the latent heat flux in the Sichuan Basin, because the unclosed energy can cause large errors. Closure of surface energy is required when the residual method is applied.

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On the Relationship between Clear-Sky Planetary and Surfae Albedos

Cited by 64 publications

References 0 publications

Intercomparison of remote sensing‐based models for estimation of evapotranspiration and accuracy assessment based on SWAT

Intercomparison of remote sensing‐based models for estimation of evapotranspiration and accuracy assessment based on SWAT

The radiative forcing potential of different climate geoengineering options

Comparative Analysis of Satellite Remotely-Sensed Surface Energy Flux and Ground-Based Observation in the Sichuan Basin

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