Abstract
Abstract. Accurate representation of ozone in the extratropical upper troposphere (UT) remains a challenge. However, the implementation of hyper-spectral remote sensing using satellite instruments such as the Tropospheric Emission Spectrometer (TES) provides an avenue for mapping ozone in this region, from 500 to 300 hPa. As a polar orbiting satellite TES observations are limited, but in this paper they are combined with geostationary satellite observations of water vapor. This paper describes a validation of the Multi-sensor UT Ozone Product (MUTOP). MUTOP, based on a statistical retrieval method, is an image product derived from the multiple regression of remotely sensed TES ozone, against geostationary (GOES) specific humidity (remotely sensed) and potential vorticity (a modeled dynamical tracer in the UT). These TES-derived UT ozone mixing ratios are compared to coincident ozonesonde measurements of layer-average UT ozone mixing ratios made during the NASA INTEX/B field campaign in the spring of 2006; the region for this study is effectively the GOES west domain covering the eastern North Pacific Ocean and the western United States. This intercomparison evaluates MUTOP skill at representing ozone magnitude and variability in this region of complex dynamics. In total, 11 ozonesonde launch sites were available for this study, providing 127 individual sondes for comparison; the overall mean ozone of the 500–300 hPa layer for these sondes was 78.0 ppbv. MUTOP reproduces in~situ measurements reasonably well, producing an UT mean of 82.3 ppbv, with a mean absolute error of 12.2 ppbv and a root mean square error of 16.4 ppbv relative to ozonesondes across all sites. An overall UT mean bias of 4.3 ppbv relative to sondes was determined for MUTOP. Considered in the context of past TES validation studies, these results illustrate that MUTOP is able to maintain accuracy similar to TES while expanding coverage to the entire GOES-West satellite domain. In addition MUTOP provides six-hour temporal resolution throughout the INTEX-B study period, making the visualization of UT ozone dynamics possible. This paper presents the overall statistical validation as well as a selection of ozonesonde case studies. The case studies illustrate that error may not always represent a lack of TES-derived product skill, but often results from discrepancies driven by observations made in the presence of strong meteorological gradients.
Highlights
Extensive scientific effort has been directed toward accurately characterizing ozone variability in the extratropical upper troposphere (UT); ozone prediction in this region from 500 to 300 hPa is difficult due to the presence of fine-scale filamentary features that shift with weather patterns, and the layer’s position as a mixing region between stratospheric and tropospheric reservoirs of air (Gettleman et al, 2011; Bowman et al, 2007; Fairlie et al, 2007, Wernli and Sprenger, 2007)
Plots of time series comparisons between ozonesondemeasured layer-average UT ozone and multi-sensor estimates of layer-average UT ozone are provided in Fig. 3 for the sounding sites with more than ten launches during the Intercontinental Chemical Transport Experiment Phase B (INTEX-B) study period
The Multi-sensor UT Ozone Product (MUTOP) results for Kelowna, British Columbia track the synoptic/dynamic response of the ozonesondes going from ∼150 ppb down to ∼60 ppb, and later capture two more spikes over 150 ppb as the UT responded to the passage of upper level troughs
Summary
Extensive scientific effort has been directed toward accurately characterizing ozone variability in the extratropical upper troposphere (UT); ozone prediction in this region from 500 to 300 hPa is difficult due to the presence of fine-scale filamentary features that shift with weather patterns, and the layer’s position as a mixing region between stratospheric and tropospheric reservoirs of air (Gettleman et al, 2011; Bowman et al, 2007; Fairlie et al, 2007, Wernli and Sprenger, 2007). While these chemical models are constantly being improved, interest in accurately capturing the presence and variability of ozone in the UT suggests that new methods, based on satellite observations specific to the upper troposphere, may provide a realistic companion approach
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