Tropical tropospheric ozone derived using Clear-Cloudy Pairs (CCP) of TOMS measurements M. J. Newchurch1, D. Sun1, J. H. Kim2, and X. Liu1,3 1Atmospheric Science Department, University of Alabama in Huntsville, Huntsville, Alabama 2Department of Atmospheric Science, Pusan National University, Korea 3Now at Harvard Smithsonian Astrophysical Observatory, Cambridge, Massachusetts
Abstract. Using TOMS total-ozone measurements over high-altitude cloud locations and nearby paired
clear locations, we describe the Clear-Cloudy Pairs (CCP) method for deriving tropical
tropospheric ozone. The high-altitude clouds are identified by measured
380 nm reflectivities greater than 80% and Temperature Humidity InfraRed (THIR) measured cloud-top pressures
less than 200 hPa. To account for locations without high-altitude clouds, we apply a zonal sine
fitting to the stratospheric ozone derived from available cloudy points, resulting in a wave-one
amplitude of about 4 DU. THIR data is unavailable after November 1984, so we extend the
CCP method by using a reflectivity threshold of 90% to identify high-altitude clouds and
remove the influence of high-reflectivity-but-low-altitude clouds with a lowpass frequency
filter. We correct ozone retrieval errors associated with clouds, and ozone retrieval errors due
to sun glint and aerosols. Comparing CCP results with Southern Hemisphere ADditional
OZonesondes (SHADOZ) tropospheric ozone indicates that CCP tropospheric ozone and
ozonesonde measurements agree, on average, to within 3 ± 1 DU standard error of the mean.
The most significant difference between CCP and ozonesonde tropospheric ozone can be
explained by the low Total Ozone Mapping Spectrometer (TOMS) version-7 retrieval
efficiency of ozone in the lower troposphere.
Citation: Newchurch, M. J., Sun, D., Kim, J. H., and Liu, X.: Tropical tropospheric ozone derived using Clear-Cloudy Pairs (CCP) of TOMS measurements, Atmos. Chem. Phys., 3, 683-695, doi:10.5194/acp-3-683-2003, 2003.