TOMS TROPICAL TROPOSPHERIC AND STRATOSPHERIC
COLUMN OZONE
DATA PRODUCTS: Tropospheric column ozone (TCO) and stratospheric
column ozone (SCO) measured in Dobson units (DU). All TCO and SCO
measurements were determined using TOMS Version 8 measurements of
column ozone and reflectivity.
TEMPORAL RESOLUTION: Monthly averages from January 1979 to the
present.
HORIZONTAL RESOLUTION: 5 degrees latitude by 5 degrees longitude.
LATITUDINAL COVERAGE: Central latitudes (in degrees) -12.5, -7.5,
-2.5, 2.5, 7.5, 12.5.
LONGITUDINAL COVERAGE: Central longitudes (in degrees) -177.5,
-167.5, ..., 177.5.
OVERVIEW OF CCD METHOD: Monthly averaged TCO and SCO data are derived
in the tropics for January 1979-present using the convective cloud
differential (CCD) method of Ziemke et al. (JGR, 1998). In the CCD
method total column ozone is derived from low reflectivity (R<0.2)
measurements and SCO follows from nearby column ozone measurements
taken above the tops of tropopause level clouds under conditions of
high reflectivity (R>0.9). Above-cloud column amounts (in 5 degree by
5 degree bins) are first evaluated in the Pacific region where
tropopause/near-tropopause level clouds are common. SCO is then
derived for every 5 degree latitude band for 120E eastward to 120W
using only the lowest values of above-cloud column amounts (it is the
average of these lowest column amounts over the Pacific that becomes
our estimated SCO). These SCO values from the Pacific region are then
assumed to represent SCO at all other longitudes in a given latitude
band. This assumption is based on the zonal characteristics of
tropical SCO as inferred from Stratospheric Aerosols and Gas
Experiment (SAGE) ozone, and as inferred from Upper Atmosphere Research
Satellite (UARS) microwave limb sounder (MLS) and halogen occultation
experiment (HALOE) ozone.
MISSING DATA: All months from May 1993 through July 1996. Other
months may have some missing data. Missing data are given a value of
zero.
ESTIMATED MEASUREMENT UNCERTAINTIES (2-SIGMA VALUES) IN TCO DATA: 3 DU
in the Pacific increasing uniformly to 6 DU over the Atlantic.
ESTIMATED MEASUREMENT UNCERTAINTIES (2-SIGMA VALUES) IN SCO DATA: 3 DU
in the Pacific increasing uniformly to 6 DU over the Atlantic.