Atmospheric Trace Gas Data Set Inter-Comparison Project


Over the last 30 years, satellite measurements have provided a wealth of knowledge regarding chemical trace gas abundances in the stratosphere. Data sets of chemical trace gases are widely used for empirical studies of stratospheric climate and variability, and for the validation of the representation of transport and chemistry in numerical models. A number of data sets from different ESA, CSA, and NASA satellite instruments are available, which vary in terms of measurement method, geographical coverage, spatial and temporal sampling and resolution, time period, and retrieval algorithm. It is often difficult for a user to determine which is the most reliable or useful data set for a particular application. Comparing numerical model output to different chemical data sets can lead to conflicting results which limits the value of model inter-comparison studies.

This project aims at assessing the available data sets of chemical trace gases and at a detailed inter-comparison of compiled atmospheric composition climatologies. In a first step, it will assess the current state of data availability from the multi-national suite of space-based instruments. The project will then assemble existing climatologies and compile new climatologies in collaboration with the instrument PIs. The main objective is a detailed comparison of climatologies of chemical trace gas species which will identify differences between the data sets. Where possible, an expert judgment on the source of those differences will be provided. The detailed results will be documented in a SPARC (Stratospheric Processes and Their Role in Climate) peer-reviewed report, which will serve as a guide to the use of long-term chemical data sets in empirical studies of climate and variability and in model-measurement comparison.