Scientific Theme: Advanced Modeling and Observing Systems

Theme report: Climate System Variability
ACCOMPLISHMENTS FOR GMD03.1:
This work evaluated the quality of tropospheric ozone information derived from the ground-based Dobson and
Brewer measurements. A newly developed Umkehr ozone-profile retrieval algorithm allowed separation of the
tropospheric ozone measurement into two or three layers. The Umkehr-retrieved tropospheric ozone data were
validated through comparisons with co-incident ozonesonde measurements of high vertical resolution. The analysis
concentrated on the short-term and long-term tropospheric ozone variability detected by co-incident and co-located
Dobson and Brewer data, along with ozone profiles from ozonesondes available from Boulder, CO, and Hilo, HI.
Analyses suggest that the Dobson Umkehr technique is capable of monitoring short-term variability in tropospheric
ozone. It can explain about 50% of the variability measured by ozonesondes. It was found that the one-day coincident
data have higher correlation coefficients than the two-day window for Boulder, but not for Mauna Loa. In
addition, correlation coefficients calculated for co-incident Umkehr and ozonesonde data were found to be relatively
large (40-60%) and statistically significant in the troposphere, although the highest correlation (70%) was found in
the lower stratosphere. Ozonesonde data smoothed with the corresponding Umkehr Averaging Kernel function
showed larger correlation coefficients (up to 80%) as compared to comparisons using layer-integrated ozonesonde
data. Based on correlation analysis, Dobson Umkehr data can capture tropospheric ozone variability. The Umkehr
method is capable of measuring long-term changes in tropospheric ozone [Petropvalovskikh et al., AGU, 2006].
Correlation between co-incidental sonde and Dobson ozone measurements (in excess of a
priori) as function of Umkehr layer (~5 km wide) for (right) MLO station record during 1985-
2005, and (left) Boulder station records during 1985-2005 time period. Black lines represent
results for layer-integrated ozonesonde data, red lines show results for Umkehr smoothed
ozonesonde data.
MILESTONE GMD03.2:
Optimize and validate algorithm for ozone column retrievals from photo-actinic flux hyper-spectral
measurements on board an aircraft under a variety of atmospheric conditions. Provide data to
OMI/AURA satellite validation campaigns.
ACCOMPLISHMENTS FOR GMD03.2:
This research is in support of Aura satellite validation activities. The solar radiation measurement instrumentation
was developed by the National Center for Atmospheric Research group (R. Shetter) and deployed on the NASA
WB-57 and DC-8 aircraft platforms in several Aura Validation Experiment (AVE) campaigns. These instruments
are CCD-based Actinic Flux Spectroradiometers (CAFS) to determine the down- and up-welling UV and visible
actinic flux as a function of wavelength. The Ozone Monitoring Instrument (OMI) total ozone columns and
Microwave Limb Sounder (MLS) integrated ozone profiles were validated in the tropical region. The CR-AVE
campaign base in Costa Rica took place in January and February of 2006. The CAFS observations were taken
aboard the NASA WB-57 flights co-incident with the OMI ozone observation (~10,900 data points). The average
difference between OMI DOAS (Differential Optical Absorption Spectroscopy) and CAFS total ozone column
estimates was -5.4 DU with a standard deviation of 5.2 DU. The average difference between OMI TOMS (Total
Ozone Mapping Spectrometer) and CAFS total ozone column estimates was -4.2 DU with a standard deviation of
4.1. Comparisons of the OMI and the CAFS total ozone residuals suggest dependence on the total ozone column in
both versions of the OMI retrieved data. These differences are well within the validation requirements of ±2% for
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