Photolysis rates in correlated overlapping cloud fields: Cloud-J 7.3c
A new approach for modeling photolysis rates (<i>J</i> values) in atmospheres with fractional cloud cover has been developed and is implemented as Cloud-J – a multi-scattering eight-stream radiative transfer model for solar radiation based on Fast-J. Using observations of the vertical co...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2015-08-01
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| Series: | Geoscientific Model Development |
| Online Access: | http://www.geosci-model-dev.net/8/2587/2015/gmd-8-2587-2015.pdf |
| Summary: | A new approach for modeling photolysis rates (<i>J</i> values) in atmospheres with
fractional cloud cover has been developed and is implemented as Cloud-J – a
multi-scattering eight-stream radiative transfer model for solar radiation
based on Fast-J. Using observations of the vertical correlation of cloud
layers, Cloud-J 7.3c provides a practical and accurate method for modeling
atmospheric chemistry. The combination of the new maximum-correlated cloud
groups with the integration over all cloud combinations by four quadrature
atmospheres produces mean <i>J</i> values in an atmospheric column with
root mean square (rms) errors of 4 % or less compared with 10–20 % errors
using simpler approximations. Cloud-J is practical for chemistry–climate
models, requiring only an average of 2.8 Fast-J calls per atmosphere vs.
hundreds of calls with the correlated cloud groups, or 1 call with the
simplest cloud approximations. Another improvement in modeling <i>J</i> values,
the treatment of volatile organic compounds with pressure-dependent cross
sections, is also incorporated into Cloud-J. |
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| ISSN: | 1991-959X 1991-9603 |