A radiative transfer model for surface radiation budget studies

Abstract. In situ surface observations show that downward surface solar radiation (SWdn) over the central and southeastern United States (US) has increased by 0.58–1.0 Wm−2 a−1 over the 2000–2014 time frame, simultaneously with reductions in US aerosol optical depth (AOD) of 3.3–5.0  ×  10−3 a−1. Establishing a link between these two trends, however, is challenging due to complex interactions between aerosols, clouds, and radiation. Here we investigate the clear-sky aerosol–radiation effects of decreasing US aerosols on SWdn and other surface variables by applying a one-dimensional radiative transfer to 2000–2014 measurements of AOD at two Surface Radiation Budget Network (SURFRAD) sites in the central and southeastern United States. Observations characterized as clear-sky may in fact include the effects of thin cirrus clouds, and we consider these effects by imposing satellite data from the Clouds and Earth's Radiant Energy System (CERES) into the radiative transfer model. The model predicts that 2000–2014 trends in aerosols may have driven clear-sky SWdn trends of +1.35 Wm−2 a−1 at Goodwin Creek, MS, and +0.93 Wm−2 a−1 at Bondville, IL. While these results are consistent in sign with observed trends, a cross-validated multivariate regression analysis shows that AOD reproduces 20–26 % of the seasonal (June–September, JJAS) variability in clear-sky direct and diffuse SWdn at Bondville, IL, but none of the JJAS variability at Goodwin Creek, MS. Using in situ soil and surface flux measurements from the Ameriflux network and Illinois Climate Network (ICN) together with assimilated meteorology from the North American Land Data Assimilation System (NLDAS), we find that sunnier summers tend to coincide with increased surface air temperature and soil moisture deficits in the central US. The 1990–2015 trends in the NLDAS SWdn over the central US are also of a similar magnitude to our modeled 2000–2014 clear-sky trends. Taken together, these results suggest that climate and regional hydrology in the central US are sensitive to the recent reductions in aerosol concentrations. Our work has implications for severely polluted regions outside the US, where improvements in air quality due to reductions in the aerosol burden could inadvertently pose an enhanced climate risk.

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Retrieval of surface radiative fluxes on the marginal zone of sea ice from operational satellite data

Annals of Glaciology ◽

10.3189/s0260305500012842 ◽

1993 ◽

Vol 17 ◽

pp. 201-206 ◽

Cited By ~ 1

Author(s):

Claude Kergomard ◽

Bernard Bonnel ◽

Yves Fouquart

Keyword(s):

Satellite Data ◽

Optical Thickness ◽

Field Measurements ◽

Surface Radiation ◽

Radiation Budget ◽

Radiative Transfer Model ◽

Cloud Base ◽

Transfer Model ◽

Liquid Water Path ◽

Surface Radiation Budget

With the development of coupled atmosphere–ocean models for the polar seas, there will be a great need of surface radiation budget data over partially ice-covered sea surfaces of the marginal ice zones. This paper presents an attempt to retrieve the surface radiation budget components over the Fram Strait area from operational satellite data, i.e. AVHRR visible and infrared radiances and SSM/I passive microwave brightness temperatures. The cloud optical thickness, which is the main modulator for the incoming solar flux, is retrieved from AVHRR visible radiances through a radiative transfer model, assuming surface conditions deduced from the SSM/I ice concentrations. The cloud base emissivity, required for the downwelling infrared flux computation, is linked to the optical thickness through the liquid water path. The results presented show a good agreement with field measurements and little sensitivity to the cloud and aerosol properties extracted from the literature rather than from the satellite data. Infrared fluxes retrievals would however require a better knowledge of the atmosphere temperature profile and cloud base altitude.

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Aerosol trends as a potential driver of regional climate in the central United States: Evidence from observations

10.5194/acp-2017-208 ◽

2017 ◽

Author(s):

Daniel H. Cusworth ◽

Loretta J. Mickley ◽

Eric M. Leibensperger ◽

Michael J. Iacono

Keyword(s):

United States ◽

Radiative Transfer ◽

Southeastern United States ◽

Radiant Energy ◽

Surface Radiation ◽

Radiation Budget ◽

Radiative Transfer Model ◽

Transfer Model ◽

Clear Sky

Abstract. In situ surface observations show that downward surface solar radiation (SWdn) over the central and southeastern United States (U.S.) has increased by 0.58–1.0 W m−2 a−1 over the 2000–2014 timeframe, simultaneously with reductions in U.S. aerosol optical depth (AOD) of 3.3–5.0 × 10−3 a−1. Establishing a link between these two trends, however, is challenging due to complex interactions between aerosols, clouds, and radiation. Here we investigate the clear-sky aerosol–radiation effects of decreasing U.S. aerosols on SWdn and other surface variables by applying a one-dimensional radiative transfer to 2000 2014 measurements of AOD at two Surface Radiation Budget Network (SURFRAD) sites in the central and southeastern United States. Observations characterized as clear–sky may in fact include the effects of thin cirrus clouds, and we consider these effects by imposing satellite data from the Clouds and Earth's Radiant Energy System (CERES) into the radiative transfer model. The model predicts that 2000–2014 trends in aerosols may have driven clear-sky SWdn trends of +1.35 W m−2 a−1 at Goodwin Creek, MS, and +0.93 W m−2 a−1 at Bondville, IL. While these results are consistent in sign with observed trends, a cross-validated multivariate regression analysis shows that AOD reproduces 20–26 % of the seasonal (June–September, JJAS) variability in clear-sky direct and diffuse SWdn at Bondville, IL, but none of the JJAS variability at Goodwin Creek, MS. Using in situ soil and surface flux measurements from the Ameriflux network and Illinois Climate Network (ICN) together with assimilated meteorology from the North American Land Data Assimilation System (NLDAS), we find that sunnier summers tend to coincide with increased surface air temperature and soil moisture deficits in the central U.S. The 1990–2015 trends in the NLDAS SWdn over the central U.S. are also of a similar magnitude as our modeled 2000–2014 clear-sky trends. Taken together, these results suggest that climate and regional hydrology in the central U.S. are sensitive to the recent reductions in aerosol concentrations. Our work has implications for severely polluted regions outside the U.S., where improvements in air quality due to reductions in the aerosol burden could inadvertently increase vulnerability to drought.

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Retrieval of surface radiative fluxes on the marginal zone of sea ice from operational satellite data

Annals of Glaciology ◽

10.1017/s0260305500012842 ◽

1993 ◽

Vol 17 ◽

pp. 201-206 ◽

Cited By ~ 5

Author(s):

Claude Kergomard ◽

Bernard Bonnel ◽

Yves Fouquart

Keyword(s):

Satellite Data ◽

Optical Thickness ◽

Field Measurements ◽

Surface Radiation ◽

Radiation Budget ◽

Radiative Transfer Model ◽

Cloud Base ◽

Transfer Model ◽

Liquid Water Path ◽

Surface Radiation Budget

With the development of coupled atmosphere–ocean models for the polar seas, there will be a great need of surface radiation budget data over partially ice-covered sea surfaces of the marginal ice zones. This paper presents an attempt to retrieve the surface radiation budget components over the Fram Strait area from operational satellite data, i.e. AVHRR visible and infrared radiances and SSM/I passive microwave brightness temperatures. The cloud optical thickness, which is the main modulator for the incoming solar flux, is retrieved from AVHRR visible radiances through a radiative transfer model, assuming surface conditions deduced from the SSM/I ice concentrations. The cloud base emissivity, required for the downwelling infrared flux computation, is linked to the optical thickness through the liquid water path. The results presented show a good agreement with field measurements and little sensitivity to the cloud and aerosol properties extracted from the literature rather than from the satellite data. Infrared fluxes retrievals would however require a better knowledge of the atmosphere temperature profile and cloud base altitude.

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Modeling the Downwelling Longwave Radiation over a Groomed Ski Run under Clear Skies

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-12-0245.1 ◽

2013 ◽

Vol 52 (7) ◽

pp. 1540-1553 ◽

Cited By ~ 1

Author(s):

Rosie Howard ◽

Roland Stull

Keyword(s):

Longwave Radiation ◽

Liquid Water Content ◽

Surface Radiation ◽

Radiation Budget ◽

Radiative Transfer Model ◽

Transfer Model ◽

Clear Sky ◽

Surface Radiation Budget ◽

Flux Model ◽

Downwelling Longwave Radiation

AbstractThe surface radiation budget of a groomed ski run is important to ski racing. Variables such as snow-surface temperature and liquid water content depend upon the surface radiation budget and are crucial to preparing fast skis. This case study focuses on downwelling longwave radiation, measurements of which were made at a point on a ski run on Whistler Mountain, British Columbia, Canada, throughout a 5-day clear-sky intensive observation period. Tall trees often dominate the horizon of a point on a ski run, and so contributions to total downwelling longwave radiation from trees and sky were treated separately. The “LWRAD” longwave radiative flux model estimated the total downwelling longwave radiation by first calculating thermal contributions from the trees, incorporating regressions for tree temperature that use routine meteorological measurements. Contributions from each azimuth direction were determined with horizon-elevation angles from a theodolite survey. Thermal emissions were weighted accordingly and summed. Sky contributions were estimated using the “libRadtran” radiative transfer model with input of local atmospheric profiles of temperature and humidity and were added to tree emissions. Two clear-sky emissivity parameterizations using screen-height measurements were tested for comparison. LWRAD total downwelling longwave radiation varies between 235 and 265 W m−2 and compares well to measurements, with correlation coefficient squared (r2) of 0.96. These results can be used to improve estimates of downwelling longwave radiation for a groomed ski run.

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Evaluation of Cirrus Parameterizations for Radiative Flux Computations in Climate Models Using TOVS–ScaRaB Satellite Observations

Journal of Climate ◽

10.1175/jcli4251.1 ◽

2007 ◽

Vol 20 (17) ◽

pp. 4459-4475 ◽

Cited By ~ 12

Author(s):

C. J. Stubenrauch ◽

F. Eddounia ◽

J. M. Edwards ◽

A. Macke

Keyword(s):

Optical Properties ◽

Radiative Transfer ◽

Climate Models ◽

Radiative Flux ◽

Satellite Observations ◽

Radiation Budget ◽

Radiative Transfer Model ◽

Transfer Model ◽

Ice Crystal ◽

Infrared Observation

Abstract Combined simultaneous satellite observations are used to evaluate the performance of parameterizations of the microphysical and optical properties of cirrus clouds used for radiative flux computations in climate models. Atmospheric and cirrus properties retrieved from Television and Infrared Observation Satellite (TIROS-N) Operational Vertical Sounder (TOVS) observations are given as input to the radiative transfer model developed for the Met Office climate model to simulate radiative fluxes at the top of the atmosphere (TOA). Simulated cirrus shortwave (SW) albedos are then compared to those retrieved from collocated Scanner for Radiation Budget (ScaRaB) observations. For the retrieval, special care has been given to angular direction models. Three parameterizations of cirrus ice crystal optical properties are represented in the Met Office radiative transfer model. These parameterizations are based on different physical approximations and different hypotheses on crystal habit. One parameterization assumes pristine ice crystals and two ice crystal aggregates. By relating the cirrus ice water path (IWP) retrieved from the effective infrared emissivity to the cirrus SW albedo, differences between the parameterizations are amplified. This study shows that pristine crystals seem to be plausible only for cirrus with IWP less than 30 g m−2. For larger IWP, ice crystal aggregates lead to cirrus SW albedos in better agreement with the observations. The data also indicate that climate models should allow the cirrus effective ice crystal diameter (De) to increase with IWP, especially in the range up to 30 g m−2. For cirrus with IWP less than 20 g m−2, this would lead to SW albedos that are about 0.02 higher than the ones of a constant De of 55 μm.

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Global distribution of Earth's surface shortwave radiation budget

Atmospheric Chemistry and Physics ◽

10.5194/acp-5-2847-2005 ◽

2005 ◽

Vol 5 (10) ◽

pp. 2847-2867 ◽

Cited By ~ 108

Author(s):

N. Hatzianastassiou ◽

C. Matsoukas ◽

A. Fotiadi ◽

K. G. Pavlakis ◽

E. Drakakis ◽

...

Keyword(s):

Radiative Heating ◽

Surface Radiation ◽

Radiation Budget ◽

Shortwave Radiation ◽

Radiative Transfer Model ◽

Physical Parameters ◽

Transfer Model ◽

Data Set ◽

Global Mean

Abstract. The monthly mean shortwave (SW) radiation budget at the Earth's surface (SRB) was computed on 2.5-degree longitude-latitude resolution for the 17-year period from 1984 to 2000, using a radiative transfer model accounting for the key physical parameters that determine the surface SRB, and long-term climatological data from the International Satellite Cloud Climatology Project (ISCCP-D2). The model input data were supplemented by data from the National Centers for Environmental Prediction - National Center for Atmospheric Research (NCEP-NCAR) and European Center for Medium Range Weather Forecasts (ECMWF) Global Reanalysis projects, and other global data bases such as TIROS Operational Vertical Sounder (TOVS) and Global Aerosol Data Set (GADS). The model surface radiative fluxes were validated against surface measurements from 22 stations of the Baseline Surface Radiation Network (BSRN) covering the years 1992-2000, and from 700 stations of the Global Energy Balance Archive (GEBA), covering the period 1984-2000. The model is in good agreement with BSRN and GEBA, with a negative bias of 14 and 6.5 Wm-2, respectively. The model is able to reproduce interesting features of the seasonal and geographical variation of the surface SW fluxes at global scale. Based on the 17-year average model results, the global mean SW downward surface radiation (DSR) is equal to 171.6 Wm-2, whereas the net downward (or absorbed) surface SW radiation is equal to 149.4 Wm-2, values that correspond to 50.2 and 43.7% of the incoming SW radiation at the top of the Earth's atmosphere. These values involve a long-term surface albedo equal to 12.9%. Significant increasing trends in DSR and net DSR fluxes were found, equal to 4.1 and 3.7 Wm-2, respectively, over the 1984-2000 period (equivalent to 2.4 and 2.2 Wm-2 per decade), indicating an increasing surface solar radiative heating. This surface SW radiative heating is primarily attributed to clouds, especially low-level, and secondarily to other parameters such as total precipitable water. The surface solar heating occurs mainly in the period starting from the early 1990s, in contrast to decreasing trend in DSR through the late 1980s. The computed global mean DSR and net DSR flux anomalies were found to range within ±8 and ±6 Wm-2, respectively, with signals from El Niño and La Niña events, and the Pinatubo eruption, whereas significant positive anomalies have occurred in the period 1992-2000.

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Radiative signature of absorbing aerosol over the eastern Mediterranean basin

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-7213-2014 ◽

2014 ◽

Vol 14 (14) ◽

pp. 7213-7231 ◽

Cited By ~ 26

Author(s):

A. K. Mishra ◽

K. Klingmueller ◽

E. Fredj ◽

J. Lelieveld ◽

Y. Rudich ◽

...

Keyword(s):

Radiative Transfer ◽

Eastern Mediterranean ◽

Eastern Mediterranean Region ◽

Radiation Budget ◽

Radiative Transfer Model ◽

Transfer Model ◽

Aerosol Layer ◽

Marine Aerosol ◽

Model Calculations ◽

Aerosol Types

Abstract. The effects of absorbing aerosols on the atmospheric radiation budget and dynamics over the eastern Mediterranean region are studied using satellites and ground-based observations, and radiative transfer model calculations, under summer conditions. Climatology of aerosol optical depth (AOD), single scattering albedo (SSA) and size parameters were analyzed using multi-year (1999–2012) observations from Moderate Resolution Imaging Spectroradiometer (MODIS), Multi-angle Imaging SpectroRadiometer (MISR) and AErosol RObotic NETwork (AERONET). Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP)-derived aerosol vertical distributions and their classifications are used to calculate the AOD of four dominant aerosol types: dust, polluted dust, polluted continental, and marine aerosol over the region. The seasonal mean (June–August 2010) AODs are 0.22 ± 0.02, 0.11 ± 0.04, 0.10 ± 0.04 and 0.06 ± 0.01 for polluted dust, polluted continental, dust and marine aerosol, respectively. Changes in the atmospheric temperature profile as a function of absorbing aerosol loading were derived for the same period using observations from the AIRS satellite. We inferred heating rates in the aerosol layer of ~1.7 ± 0.8 K day−1 between 925 and 850 hPa, which is attributed to aerosol absorption of incoming solar radiation. Radiative transfer model (RTM) calculations show significant atmospheric warming for dominant absorbing aerosol over the region. A maximum atmospheric forcing of +16.7 ± 7.9 Wm−2 is calculated in the case of polluted dust, followed by dust (+9.4 ± 4.9 Wm−2) and polluted continental (+6.4 ± 4.5 Wm−2). RTM-derived heating rate profiles for dominant absorbing aerosol show warming of 0.1–0.9 K day−1 in the aerosol layer (< 3.0 km altitudes), which primarily depend on AODs of the different aerosol types. Diabatic heating due to absorbing aerosol stabilizes the lower atmosphere, which could significantly reduce the atmospheric ventilation. These conditions can enhance the "pollution pool" over the eastern Mediterranean.

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Assessment and Validation of i-Skyradiometer Retrievals Using Broadband Flux and MODIS Data

Advances in Meteorology ◽

10.1155/2014/849279 ◽

2014 ◽

Vol 2014 ◽

pp. 1-8

Author(s):

S. Dipu ◽

G. Pandithurai ◽

A. S. Panicker ◽

T. Takamura ◽

Dong-In Lee ◽

...

Keyword(s):

Radiative Transfer ◽

Climate Models ◽

Surface Radiation ◽

Combination Method ◽

New Combination ◽

Radiative Transfer Model ◽

Retrieval Algorithm ◽

Transfer Model ◽

Cloud Parameters ◽

Radiation Measurements

Ground-based network of cloud measurements is presently limited and there exists uncertainty in the cloud microphysical parameters derived from ground-based measurements. Bias in the i-skyradiometer derived cloud optical depth (τc) and droplet effective radius (Reff) and the importance of these parameters in the parameterization of clouds in climate models have made us intend to develop a possible method for improving these parameters. A new combination method, which uses zenith sky transmittance and surface radiation measurements, has been proposed in the present study to improve the retrievals. The i-skyradiometer derived parametersτcandReffhave been provided as a first guess to a radiative transfer model (SBDART) and a new retrieval algorithm has been implemented to obtain the best combination ofτcandReffhaving minimum bias (−0.09 and −2.5) between the simulated global and diffuse fluxes at the surface with the collocated surface radiation measurements. The new retrieval method has improvedτcandReffvalues compared to those derived using the transmittance only method and are in good agreement with the MODIS satellite retrievals. The study therefore suggests a possible improvement of the i-skyradiometer derived cloud parameters using observed radiation fluxes and a radiative transfer model.

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On the influence of erect shrubs on the irradiance profile in snow

10.5194/bg-2020-461 ◽

2021 ◽

Author(s):

Maria Belke-Brea ◽

Florent Domine ◽

Ghislain Picard ◽

Mathieu Barrere ◽

Laurent Arnaud

Keyword(s):

Radiative Transfer ◽

Thermal Regime ◽

Local Effect ◽

Radiation Budget ◽

The Arctic ◽

Radiative Transfer Model ◽

Transfer Model ◽

Effect Hypothesis ◽

Snowpack Properties ◽

The Impact

Abstract. The warming-induced expansion of shrubs in the Arctic is transforming snowpacks into a mixture of snow, impurities and buried branches. Because snow is a translucent medium into which light penetrates up to tens of centimeters, buried branches may alter the snowpack radiation budget with important consequences for the snow thermal regime and microstructure. To characterize the influence of buried branches on radiative transfer in snow, irradiance profiles were measured in snowpacks with and without shrubs near Umiujaq in the Canadian Low Arctic (56.5° N, 76.5° W) in November and December 2015. Using the irradiance profiles measured in shrub-free snowpacks in combination with a Monte Carlo radiative transfer model revealed that the dominant impurity type was black carbon (BC) in variable concentrations up to 185 ng g−1. This allowed the separation of the radiative effects of impurities and buried branches. Irradiance profiles measured in snowpacks with shrubs showed that the impact of buried branches was generally weak, except for layers where branches were also visible in snowpit photographs, suggesting that branches influence snow locally (i.e. a few centimeters around branches). The local-effect hypothesis was further supported by observations of localized melting and depth hoar pockets that formed in the vicinity of branches. Buried branches therefore affect snowpack properties, with possible impacts on Arctic flora and fauna and on the thermal regime of permafrost. Lastly, the unexpectedly high BC concentrations in snow are likely caused by nearby open-air waste burning, suggesting that cleaner waste management plans are required for northern community and ecosystem protection.

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