Research Projects

Tropical Ozone Trends as an Indicator of Changes in the Brewer-Dobson Circulation?

Proposal Summary

We started this project to merge together ozone records from two satellites and the ozonesonde network. The focus was on the tropics to try to understand if the apparent negative trend in ozone above the tropical tropopause was caused by the speed-up of the Brewer-Dobson circulation. We started by looking at the seasonal variation of ozone from the various instruments. We found an interesting pattern with latitude and altitude of the magnitude of the annual cycle of ozone. The magnitude was maximum in the midlatitudes of both hemispheres, but there was a secondary maximum located just above the tropical tropopause. This maximum was shifted toward the northern tropics. This suggested the necessity to look at the tropics separately in the two hemispheres, particularly with respect to the timing of the uplift from the Brewer-Dobson circulation and mixing from mid-latitudes. Models obtain a variety of results that may be useful in understanding their transport differences. Our inital paper on this topic can be found here.

The Impact of Spectral Irradiance Variations on the Atmosphere and Climate: Model Simulations and Observations

Proposal Summary

This project started by examining the difference between the ozone response to solar variations due to two different renditions of the variation of solar ultraviolet radiation over a solar cycle. An important result was the realization that the response of ozone was very different for wavelengths less than 242 nm compared to wavelengths greater than 242 nm. Below 242 nm uv photolyzes both O2 and O3. The photolysis of O2 is dominant and leads to a positive response of ozone to the solar cycle. Above 242 nm uv photolyzes only O3 leading to a negative response of ozone to the solar cycle. The net response as a function of altitude depends on the relative variation of uv as a function of wavelength with the solar cycle. Our paper can be found here.

Merged Ozone Data (MOD)

MOD web page

Total Ozone Data Table
V8.6 TOMS/SBUV Through July 2015

The SBUV and TOMS instruments have been measuring the total column and profile of ozone in the stratosphere since 1978. We have put together a Merged Ozone Data page to describe the intercalibration of instruements to form a merged time series of ozone. The paper describing the first version of the data set can be found here. An updated paper describing the current (2015) MOD data set based on Version 8.6 SBUV measurements is found here.