Aura MLS


Global OZone Chemistry And Related trace gas Data records for the Stratosphere

This site provides information and access to a commonly-formatted Earth system data record (ESDR) for stratospheric composition, of high relevance to the issue of ozone decline and recovery. High-quality long-term ozone and related trace gas data records are needed to (a) evaluate and understand composition changes in the atmosphere and (b) constrain model representations of atmospheric dynamics and photochemistry.

The datasets are drawn from zonal mean satellite-derived global stratospheric composition measurements from 1979 onward, as well as from GMAO MERRA (meteorological analyses) for temperature. The satellite-based abundance measurements come from past missions (e.g., SAGE, HALOE data) as well as ongoing missions (ACE-FTS and Aura MLS). The planned data records are provided as time series monthly zonal average profiles (versus pressure) as a function of latitude, for temperature and the following species: hydrogen chloride (HCl), ozone (O3), water vapor (H2O), nitric acid (HNO3), and nitrous oxide (N2O).

To quantify the impact of inorganic bromine on stratospheric ozone loss, accurate measurements of its abundance are needed. However, because of their low abundances (several ppt), relatively few measurements have been made of its constituents. Therefore Bry is typically estimated from stratospheric measurements of BrO, combined with estimates of the other constituents from photochemical models. One current problem is that estimates of Bry from measurements of stratospheric BrO obtained by various satellite and balloon-borne instruments show some disagreement.

The establishment of such commonly-formatted data records involves careful screening and production of "source" datasets (zonal means from the original instrument (Level 2) data), the evaluation of offsets (biases) between various datasets, and assessments of spatial and temporal consistency.

Data Information

Oct. 2019 Update: Besides the original (version 1.01) data (through year 2012), updated files (through year 2018) have been provided for ozone (version 2.20). Files for additional years will be provided on a yearly basis, as long as the data are deemed useful for scientific investigations. Some comments/caveats will be provided in the updated “README” document for data users (e.g., depending on the species and time period). See Froidevaux et al. (2015) for an overview of the original GOZCARDS data sets, and Froidevaux et al. (2019) for information on version 2.20 ozone, also used by others in the literature (e.g., see the WMO Ozone Assessment Report, 2018, and references therein).

Caveats and future plans: There have been no GOZCARDS data updates, so far, using the more recent (version 4) ACE-FTS (Atmospheric Chemistry Experiment-Fourier Transform Spectrometer) data sets. This is best done after a careful evaluation of long-term drifts in either MLS or ACE-FTS data, and the relative drifts between these two sets of time series. For some species (H2O, and maybe N2O), GOZCARDS updates would best be produced after MLS version 5 data are reprocessed, in order to account for at least part of the MLS-related drifts for these species (see, e.g., Froidevaux et al., 2019).

Data for the MEaSURES GOZCARDS project are hosted by the Goddard Earth Science Data and Information Services Center (GES-DISC). This MEaSUREs GOZCARDS Earth System Data Record (ESDR) consists of products generated with a focus on stratospheric ozone and related chemical species. The products include zonal average time series derived from "Level 2" products based primarily on measurements from satellite-borne instruments, and largely from NASA missions studying the Earth's stratosphere since the late 1970s. The merged dataset (time series in various latitude/pressure bins) follow the source datasets being merged together, after adjustments for a combination of the offsets that mitigate data discontinuities (average biases) between the different instruments' measurements. Data users should make sure they are familiar with the README Document for the Global OZone Chemistry And Related trace gas Data records for the Stratosphere (GOZCARDS) project before attempting to use the data.

The Data Sources Table summarizes the GOZCARDS products (stratospheric species name or temperature (T)), and source datasets. The products' files generally include source datasets (individual instrument records) as well as merged datasets, based on a combination of instruments. The product types in the GOZCARDS files are species Volume Mixing Ratio (VMR) or T time series on a latitude/pressure grid (10° monthly zonal averages). Note that the 10° latitude bins have centers at 85S, 75S, ...75N, 85N. Also, the pressure grid is based on pressure = 1000 (hPa) x 10(-n/6) with n = 0,1,2... and maximum coverage being from 1000 to 0.01 hPa. Refer to the Data Sources Table for recommended pressure ranges for individual GOZCARDS datasets.

Also the chart at the bottom provides a timeline of satellite missions and instruments considered for the GOZCARDS project and the creation of a stratospheric composition ESDR. Dotted lines indicate some degradation in coverage during the ending phase of some missions (SAGE II, UARS MLS); HALOE also suffered from poorer coverage in the second half of the UARS mission.


Links to various readers and data applications that can be used for GOZCARDS data analysis.

Ncview is a visual browser for netCDF format files. Typically you would use ncview to get a quick and easy, push-button look at your netCDF files. You can view simple movies of the data, view along various dimensions, take a look at the actual data values, change color maps, invert the data, etc. It runs on UNIX platforms under X11, R4 or higher. For more information, check out the README file; you can also see a representative screen image (GIF, 66K) of ncview in action.

NetCDF Toolbox
MEXNC is a mex-file interface to NetCDF files for MATLAB, and has roughly a one-to-one equivalence with the C API for NetCDF. In fact, there's no better introduction to MEXNC than to read the NetCDF User's Guide for C provided by Unidata. It currently compiles with NetCDF library versions 3 and higher, and if it is built with 3.6.0 or higher, you may get the benefit of Large File Support if your OS supports it. Here's a general overview of mexnc.

NetCDF Format Description


Below are links to information about the various data sets that are used by the GOZCARDS project; please see the README document for further information.