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- Title
Photolysis rates in correlated overlapping cloud fields: Cloud-J 7.3.
- Authors
Prather, M. J.
- Abstract
A new approach for modeling photolysis rates (J values) in atmospheres with fractional cloud cover has been developed and implemented as Cloud-J - a multi-scattering eight-stream radiative transfer model for solar radiation based on Fast-J. Using observed statistics for the vertical correlation of cloud layers, Cloud-J 7.3 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 represented by four quadrature atmospheres produces mean J values in an atmospheric column with root-mean-square 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 J values, the treatment of volatile organic compounds with pressure-dependent cross sections is also incorporated into Cloud-J.
- Subjects
PHOTOLYSIS (Chemistry); CLOUD computing; ATMOSPHERIC chemistry; SOLAR radiation; ROOT-mean-squares; COMPUTER simulation of radiative transfer
- Publication
Geoscientific Model Development Discussions, 2015, Vol 8, Issue 5, p4051
- ISSN
1991-9611
- Publication type
Article
- DOI
10.5194/gmdd-8-4051-2015