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Fifth National Climate Assessment - Read the Report

Measuring ozone in the tropics

Longitudinal cross-section of 1998–2016 SHADOZ ozonesonde total column ozone (O<sub>3</sub>) (red circles with ±1 standard deviation (SD) in light red shading) and the collective mean overpass columns from the Total Ozone Mapping Spectrometer (TOMS)-Ozone Monitoring Instrument (OMI)-Ozone Mapping Profiler Suite (OMPS) satellite instruments (black with ±1 SD black bars). Ozone concentration is measured in Dobson Units (DU). The typically 2% agreement between SHADOZ records and satellite measurements represents a marked improvement in data products since the 1990s, enabling more precise projections of feedbacks among ozone, temperature, and atmospheric dynamics in the tropics. Source: Thompson et al., 2017. <sup>[<a href="#_ftn1" name="_ftnref1" title="">1</a>]</sup></p><br clear="all"><hr align="left" size="1" width="33%"><p><sup><a href="#_ftnref1" name="_ftn1" title="">1</a></sup>&nbsp;Thompson, A. M., Witte, J. C., Sterling, C., Jordan, A., Johnson, B. J., Oltmans, S. J., … Thiongo, K. (2017). First reprocessing of Southern Hemisphere Additional Ozonesondes (SHADOZ) ozone profiles (1998–2016): 2. Comparisons with satellites and ground-based instruments. Journal of Geophysical Research: Atmospheres, 122.

Balloon-borne instruments measure ozone levels high in the tropical atmosphere, providing new data to help refine projections of future climate change as well as educational opportunities for students in participating countries.

Ozone is a powerful greenhouse gas and an important contributor to global climate change. Its impact on the climate is strongest in a region of Earth’s upper atmosphere (upper troposphere and lower stratosphere) where it influences the amount of energy that escapes to space. Ozone distribution in this region is influenced by the upward movement of warm air from the planet’s surface. Climate models have difficulty reproducing atmospheric circulation patterns in tropical regions in particular, and advancing model ability to capture the distribution of ozone near the Equator is an important goal in improving projections of climate change.

Balloon-borne instruments called ozonesondes capture detailed measurements of ozone variability throughout the tropical atmosphere that can help improve satellite estimates of tropical ozone and advance model understanding of ozone distribution mechanisms. The Southern Hemisphere ADditional OZonesondes (SHADOZ) project was initiated in 1998 by NASA/Goddard Space Flight Center with NOAA’s Global Monitoring Division and international coinvestigators. The project continues to launch ozonesondes biweekly at thirteen stations in the SHADOZ network, generating a dataset that provides the first long-term measurements of tropical ozone in the equatorial region. At present, there are around 7000 sets of archived SHADOZ ozone profiles from the Earth’s surface up to about 30 kilometers.

These data also support improved understanding of the impacts of climate warming on atmospheric circulation and the expansion of the tropics, and provide insight into linkages among tropical meteorology, ozone, and pollution. SHADOZ data are free to the public and serve as an educational tool for students, particularly in participating countries.