TC4 campaign results: validating the Aura OMI total ozone data in tropics with the airborne CAFS and DIAL ozone measurements.

Highly resolved UV and Visible actinic flux measurements were taken by the CCD Actinic Flux Spectrometer (CAFS) instrument (R. Shetter, NCAR) onboard the NASA DC8 aircraft as part of the Tropical Composition, Clouds and Climate Coupling (TC4) campaign in Costa Rica. The partial ozone column above the aircraft products were derived from the CAFS actinic flux measurements as part of the continuous validation of the Aura ozone products. Although substantial parts of the NASA DC8 flights were flown in the clouds that somewhat inhibited the CAFS ozone retrieval algorithm, a sizable data set of partial ozone columns along the tracks of the Aura satellite were obtained. Preliminary analysis of the CAFS measurements shows the ability of the CAFS retrieval to produce good quality ozone data from measurements taken under thin cirrus clouds. Partial ozone column data above the aircraft were derived under conditions of high-sun and low ozone. The set of combined CAFS and climatological ozone data was used for validation of the Ozone Monitoring Instrument (OMI) total ozone column under low ozone and high-sun conditions. In addition, we will present preliminary results of comparisons between the OMI total ozone column and combined stratospheric ozone columns derived from the CAFS measurements and tropospheric ozone columns integrated from the Differential Airborne Lidar (DIAL) measurements onboard the NASA DC8 aircraft. We will also discuss results of the OMI total ozone column validation during the TC4 campaign, preliminary comparisons between DIAL tropospheric ozone columns and 4D climatology for the summer tropical troposphere, and address similarities and differences between the TC4 (tropical summer) and CR-AVE06 (tropical winter) campaign results. Results of the analysis will include estimates of uncertainties in the CAFS retrievals due to its limited sensitivity to the ozone distribution above the aircraft altitude, as well as uncertainties due to effects of the bright surfaces (clouds) on the CAFS and OMI ozone retrievals.