Experimental and modeled UV erthemal irradiance under overcast conditions: the role of cloud optical depth
This paper evaluates the relationship between the cloud modification factor (CMF) in the ultraviolet erythe- mal range and the cloud optical depth (COD) retrieved from the Aerosol Robotic Network (AERONET) "cloud mode" algorithm under overcast cloudy conditions (confirmed with sky images)...
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ftunivreading:oai:centaur.reading.ac.uk:30210 2024-06-23T07:45:00+00:00 Experimental and modeled UV erthemal irradiance under overcast conditions: the role of cloud optical depth Anton, M. Alados-Arboledas, L. Guerrero-Rascado, J. L. Costa, M. J. Chiu, J. Christine Olmo, F. J. 2012-12-10 text https://centaur.reading.ac.uk/30210/ https://centaur.reading.ac.uk/30210/1/acp-12-11723-2012.pdf en eng Copernicus Publications https://centaur.reading.ac.uk/30210/1/acp-12-11723-2012.pdf Anton, M., Alados-Arboledas, L., Guerrero-Rascado, J. L., Costa, M. J., Chiu, J. C. <https://centaur.reading.ac.uk/view/creators/90003721.html> and Olmo, F. J. (2012) Experimental and modeled UV erthemal irradiance under overcast conditions: the role of cloud optical depth. Atmospheric Chemistry and Physics, 12 (23). pp. 11723-11732. ISSN 1680-7316 doi: https://doi.org/10.5194/acp-12-11723-2012 <https://doi.org/10.5194/acp-12-11723-2012> Article PeerReviewed 2012 ftunivreading https://doi.org/10.5194/acp-12-11723-2012 2024-06-11T14:59:15Z This paper evaluates the relationship between the cloud modification factor (CMF) in the ultraviolet erythe- mal range and the cloud optical depth (COD) retrieved from the Aerosol Robotic Network (AERONET) "cloud mode" algorithm under overcast cloudy conditions (confirmed with sky images) at Granada, Spain, mainly for non-precipitating, overcast and relatively homogenous water clouds. Empirical CMF showed a clear exponential dependence on experimental COD values, decreasing approximately from 0.7 for COD=10 to 0.25 for COD=50. In addition, these COD measurements were used as input in the LibRadtran radia tive transfer code allowing the simulation of CMF values for the selected overcast cases. The modeled CMF exhibited a dependence on COD similar to the empirical CMF, but modeled values present a strong underestimation with respect to the empirical factors (mean bias of 22 %). To explain this high bias, an exhaustive comparison between modeled and experimental UV erythemal irradiance (UVER) data was performed. The comparison revealed that the radiative transfer simulations were 8 % higher than the observations for clear-sky conditions. The rest of the bias (~14 %) may be attributed to the substantial underestimation of modeled UVER with respect to experimental UVER under overcast conditions, although the correlation between both dataset was high (R2 ~ 0.93). A sensitive test showed that the main reason responsible for that underestimation is the experimental AERONET COD used as input in the simulations, which has been retrieved from zenith radiances in the visible range. In this sense, effective COD in the erythemal interval were derived from an iteration procedure based on searching the best match between modeled and experimental UVER values for each selected overcast case. These effective COD values were smaller than AERONET COD data in about 80 % of the overcast cases with a mean relative difference of 22 %. Article in Journal/Newspaper Aerosol Robotic Network CentAUR: Central Archive at the University of Reading Tive ENVELOPE(12.480,12.480,65.107,65.107) Atmospheric Chemistry and Physics 12 23 11723 11732 |
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Open Polar |
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CentAUR: Central Archive at the University of Reading |
op_collection_id |
ftunivreading |
language |
English |
description |
This paper evaluates the relationship between the cloud modification factor (CMF) in the ultraviolet erythe- mal range and the cloud optical depth (COD) retrieved from the Aerosol Robotic Network (AERONET) "cloud mode" algorithm under overcast cloudy conditions (confirmed with sky images) at Granada, Spain, mainly for non-precipitating, overcast and relatively homogenous water clouds. Empirical CMF showed a clear exponential dependence on experimental COD values, decreasing approximately from 0.7 for COD=10 to 0.25 for COD=50. In addition, these COD measurements were used as input in the LibRadtran radia tive transfer code allowing the simulation of CMF values for the selected overcast cases. The modeled CMF exhibited a dependence on COD similar to the empirical CMF, but modeled values present a strong underestimation with respect to the empirical factors (mean bias of 22 %). To explain this high bias, an exhaustive comparison between modeled and experimental UV erythemal irradiance (UVER) data was performed. The comparison revealed that the radiative transfer simulations were 8 % higher than the observations for clear-sky conditions. The rest of the bias (~14 %) may be attributed to the substantial underestimation of modeled UVER with respect to experimental UVER under overcast conditions, although the correlation between both dataset was high (R2 ~ 0.93). A sensitive test showed that the main reason responsible for that underestimation is the experimental AERONET COD used as input in the simulations, which has been retrieved from zenith radiances in the visible range. In this sense, effective COD in the erythemal interval were derived from an iteration procedure based on searching the best match between modeled and experimental UVER values for each selected overcast case. These effective COD values were smaller than AERONET COD data in about 80 % of the overcast cases with a mean relative difference of 22 %. |
format |
Article in Journal/Newspaper |
author |
Anton, M. Alados-Arboledas, L. Guerrero-Rascado, J. L. Costa, M. J. Chiu, J. Christine Olmo, F. J. |
spellingShingle |
Anton, M. Alados-Arboledas, L. Guerrero-Rascado, J. L. Costa, M. J. Chiu, J. Christine Olmo, F. J. Experimental and modeled UV erthemal irradiance under overcast conditions: the role of cloud optical depth |
author_facet |
Anton, M. Alados-Arboledas, L. Guerrero-Rascado, J. L. Costa, M. J. Chiu, J. Christine Olmo, F. J. |
author_sort |
Anton, M. |
title |
Experimental and modeled UV erthemal irradiance under overcast conditions: the role of cloud optical depth |
title_short |
Experimental and modeled UV erthemal irradiance under overcast conditions: the role of cloud optical depth |
title_full |
Experimental and modeled UV erthemal irradiance under overcast conditions: the role of cloud optical depth |
title_fullStr |
Experimental and modeled UV erthemal irradiance under overcast conditions: the role of cloud optical depth |
title_full_unstemmed |
Experimental and modeled UV erthemal irradiance under overcast conditions: the role of cloud optical depth |
title_sort |
experimental and modeled uv erthemal irradiance under overcast conditions: the role of cloud optical depth |
publisher |
Copernicus Publications |
publishDate |
2012 |
url |
https://centaur.reading.ac.uk/30210/ https://centaur.reading.ac.uk/30210/1/acp-12-11723-2012.pdf |
long_lat |
ENVELOPE(12.480,12.480,65.107,65.107) |
geographic |
Tive |
geographic_facet |
Tive |
genre |
Aerosol Robotic Network |
genre_facet |
Aerosol Robotic Network |
op_relation |
https://centaur.reading.ac.uk/30210/1/acp-12-11723-2012.pdf Anton, M., Alados-Arboledas, L., Guerrero-Rascado, J. L., Costa, M. J., Chiu, J. C. <https://centaur.reading.ac.uk/view/creators/90003721.html> and Olmo, F. J. (2012) Experimental and modeled UV erthemal irradiance under overcast conditions: the role of cloud optical depth. Atmospheric Chemistry and Physics, 12 (23). pp. 11723-11732. ISSN 1680-7316 doi: https://doi.org/10.5194/acp-12-11723-2012 <https://doi.org/10.5194/acp-12-11723-2012> |
op_doi |
https://doi.org/10.5194/acp-12-11723-2012 |
container_title |
Atmospheric Chemistry and Physics |
container_volume |
12 |
container_issue |
23 |
container_start_page |
11723 |
op_container_end_page |
11732 |
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1802644812085592064 |