Ultraviolet actinic flux in clear and cloudy atmospheres: model calculations and aircraft-based measurements

GUSTAVO G. PALANCAR; R. E. SHETTER; S. R. HALL; BEATRIZ M. TOSELLI; SASHA MADRONICH

COPERNICUS PUBLICATIONS

Año: 2011 vol. 11 p. 5457 - 5457

ltraviolet (UV) actinic fluxes measured with twoScanning Actinic Flux Spectroradiometers (SAFS) aboardthe NASA DC-8 aircraft are compared with the TroposphericUltraviolet-Visible (TUV) model. The observationsfrom 17 days in July–August 2004 (INTEX-NA fieldcampaign) span a wide range of latitudes (28 N–53 N),longitudes (45W–140 W), altitudes (0.1–11.9 km), ozonecolumns (285–353 DU), and solar zenith angles (2–85).Both cloudy and cloud-free conditions were encountered.For cloud-free conditions, the ratio of observed to clearsky-model actinic flux (integrated from 298 to 422 nm) was1.01±0.04, i.e. in good agreement with observations. Theagreement improved to 1.00±0.03 for the down-wellingcomponent under clear sky conditions. In the presence ofclouds and depending on their position relative to the aircraft,the up-welling component was frequently enhanced (by asmuch as a factor of 8 relative to