Comparison of Ozone, Nitrogen Dioxide, and Formaldehyde Columns Retrieved By TEMPO and Pandora – Asdc Tools and Results

Monitoring emissions of ozone, nitrogen dioxide, and formaldehyde is crucial for understanding the atmospheric composition and its impacts on air quality and climate. This study aims to evaluate the accuracy of retrievals of column amounts of these gases by the Tropospheric Emissions: Monitoring of Pollution (TEMPO) by comparing them against retrievals of the ground-based PANDORA instruments. Ozone retrievals are also compared against retrievals from measurements by the Earth Polychromatic Imaging Camera (EPIC) aboard the Deep Space Climate Observatory (DSCOVR).

The TEMPO is a visible and ultraviolet spectrometer flying aboard of a commercial telecommunications satellite, Intelsat 40e, in geostationary orbit over 91˚ W longitude, thus maintaining a continuous view of North America. High resolution measurements of radiance reflected by the Earth back to the instrument's detectors enable retrievals of columns of ozone, nitrogen dioxide, and formaldehyde involved in the chemical dynamics of Earth’s atmosphere. TEMPO V03 Beta Level 1, 2, and 3 data were recently made available from the Atmospheric Science Data Center (ASDC) via NASA EarthData Search.

Direct-Sun Pandora spectrometer is used to retrieve column amounts of trace gases in the atmosphere by means of differential optical absorption spectroscopy at numerous locations around the globe.

Radiance measurements by DSCOVR EPIC in 10 spectral bands overlapping with the TEMPO spectrum enable global retrievals of ozone columns about 16 times a day.

ASDC has developed a set of Jupyter notebooks dedicated to individual trace gases. The notebooks allow users to select a specific PANDORA station and a timeframe of interest. The code downloads the PANDORA dataset which is sub-set to the selected timeframe and all relevant TEMPO L2 granules. Time series of the gas column retrievals along with their uncertainties are then derived with accounting for the quality flags from both datasets. Since PANDORA measurements are significantly more frequent, a procedure computing their weighted averages at the times of TEMPO retrievals was incorporated to the notebooks allowing direct comparison of gaseous columns from two sensors against each other.

The results derived by the ASDC tools show a satisfactory match between the instruments. However, it was found that the discrepancies between them are site dependent. The findings of this study will contribute to understanding of the reliability and applicability of space-based trace gases monitoring for air quality applications. The results will enhance our understanding of atmospheric processes related to O₃, NO₂, and HCHO.