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    I  have been involved in a project with researchers from NASA JPL and Georgia Tech University called the Global OZone Chemistry And Related trace gas Data records for the Stratosphere (GOZCARDS). The goal of the GOZCARDS project is to provide commonly-formatted Earth System Data Records (ESDRs) of stratospheric composition, of high relevance to the issue of ozone decline and recovery. The GOZCARDS project is part of the NASA Making Earth Science data records for Use in Research for Earth Science (MEaSUREs) program, aimed on improving the quality and availability of long-term ESDRs. The merged HCl, O3, and H2O data sets are now publicly available.

    My main responsibility was the creation of a merged H2O data record. The data records used to construct the merged H2O record are drawn from satellite-derived monthly-zonal-averages from 1991 to the present. The satellite data sets used are from the Halogen Occultation Experiment (HALOE) from 1991 to 2005, the UARS Microwave Limb Sounder (UMLS) from 1991 to 1993, and on-going (since 2004) measurements from the Aura Microwave Limb Sounder (AMLS) and the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS).  The following is a summary of creating this merged record.

    Summary of Iterative Approach to Merging Different Satellite Instruments


    Figure 1: Left Panel: Time series of monthly-zonal-averaged H2O derived from AURA MLS (red dots), ACE FTS (cyan dots), HALOE (blue dots) and the Merged (brown dots with standard deviations) in the overlap period. Right Panel: Time series of monthly-zonal-averaged H2O derived from AURA and UARS MLS (red dots), ACE FTS (cyan dots), HALOE (blue dots) and the Merged (brown dots) between October 1991, through December 2012.

    From the overlap period, Aug-2004 to Nov-2005 (See Figure 1, left panel):

    –           AMLS, ACE-FTS

    –          Refis created from co-located AMLS and ACE-FTS points

    –          Offsets are then calculated for both instruments based on Ref0

    –          Ref1 is then created from the available Ref0 and adjusted AMLS

    –           AMLS, ACE-FTS, HALOE

    –          Ref2 is then created from a weighted average of co-located Ref1 and HALOE


    –          Offsets are then calculated for HALOE and Ref1 based on Ref2

    –          Ref3 is then created from the available Ref2 and adjusted Ref1

    –          Offsets are then calculated for all 3 instruments based on Ref3  (this has already been done for HALOE)

    AMLS, ACE-FTS, and HALOE are then adjusted using the derived offsets and averaged (at collocated points with other instruments) to create the merged set. UMLS is then merged in by using the adjusted HALOE (Oct. 91 – Apr. 93) as reference. See Figure 1, right panel. Figure 2 shows the tropical tape recorder derived from the merged water vapor measurements.


    Figure 2: Derived merged water vapor time series in the tropics (20 S to 20 N).


    Comparisons with a climate data record produced by researchers at NOAA ESRL is currently underway.