Comparative analysis of SBUV/2 and HALOE ozone profiles and trends

Abstract

The Halogen Occultation Experiment (HALOE) (version 19) ozone vertical profiles are compared with the data obtained by the second generation Solar Backscatter Ultraviolet (SBUV)/2 instruments from the National Oceanic and Atmospheric Administration's NOAA-11 and NOAA-16 satellites using its version 8 algorithm. We examine the inverse noise-weighted mean percent differences between the HALOE and SBUV/2 ozone profiles at near coincident points and obtain a bias of less than 9% from 40 to 1.5 mb for the NOAA-11 and NOAA-16 satellite data records, with few exceptions. The weighted root mean square (RMS) differences between the HALOE and SBUV/2 observations are generally between 4 and 15% for pressure levels 40-1.5 mb. The RMS differences are larger for the NOAA-16 SBUV/2 data for higher latitudes. We also analyze the time-dependent differences between the two instruments in order to establish whether there is a significant relative drift. The slopes of time series of differences between the HALOE ozone profiles and the NOAA-11 and NOAA-16 SBUV/2 retrievals are, by and large, less than 1% per year and 2% per year, respectively. These results suggest a changing calibration in the NOAA-11 SBUV/2 instrument. Then we investigate the differences between ozone trends determined by the HALOE and SBUV/2 instruments. Trend differences are less than 0.5% per year in almost all latitude bands at pressure levels 10 and 3 mb. There are statistically significant biases of about 0.7% per year at 5 mb from 20°S to 50°N, and the trend differences are less than 1.3% per year at 60°-30°S. Copyright 2007 by the American Geophysical Union.