Title: Photolysis rates in correlated overlapping cloud fields: Cloud-J 7.3c

Abstract

Here, a new approach for modeling photolysis rates (J 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 J 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 J values, the treatment of volatile organic compounds with pressure-dependent cross sections, is also incorporated into Cloud-J.

Authors:

Prather, M. J.

Publication Date:

Fri Aug 14 00:00:00 EDT 2015

Research Org.:

Univ. of California, Irvine, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER)

OSTI Identifier:

1210106

Alternate Identifier(s):

OSTI ID: 1454258

Grant/Contract Number:  

SC0012536

Resource Type:

Published Article

Journal Name:

Geoscientific Model Development (Online)

Additional Journal Information:

Journal Name: Geoscientific Model Development (Online) Journal Volume: 8 Journal Issue: 8; Journal ID: ISSN 1991-9603

Publisher:

Copernicus Publications, EGU

Country of Publication:

Germany

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES