Issue 10: Water vapor retrievals

All of the above concerns likely need to be addressed for water vapor retrievals as well.

 Response from Kevin Trenberth:
In the tropics, where temperature variability is less, it may be worthwhile trying to reverse the above and produce a water vapor product.  But recall you can not get both without assumptions or values from elsewhere.

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3 Comments

  1. Seth Gutman

    Consolidated Comments from Gutman, Yoe and Reale

    Seth Gutman's Response
    I think this issue has been well covered in the above discussions.

    Tony Reale's Response
    It occurs to me that perhaps the refractivity difference (COSMIC minus calculated) where calculated is based only on the NWP T (moist) only could be used to retrieve the moisture "independent" (so to speak) of the NWP moisture (which could then be compared to the NWP moisture, collocated sonde moisture and associated calculated and observed refractivities to validate / judge ... ). This means the T from NWP would not change (except perhaps through covariance...) but as an "experiment" it may prove "better" than trying to unravel the parsing (which is clearly NWP dependent).
    One thing that clearly needs to be understood are the details of the 1dvar (background error, etc) and as stated earlier the first guess must be stored (I don't think that respective multiple iteration guesses are needed but if they exist it wouldn't hurt to include them at least on an experimental basis)

  2. Ben Ho

    Response from Ben Ho

    We have quantified the comparability of water vapor from different COSMIC satellites in Figs. 7-11 in response to issue 1.

    In issue 7, we have also demonstrated the potential usefulness of 1D-var water vapor as a baseline humidity monitoring network for the lower troposphere.

    Studies have shown (not listed) that atmospheric perceptible water (PW) from ground-based GPS has accuracy of < 2 mm. With consistent antenna type, ground-based GPS may provide consistent PW value with climate quality. If that is the case, quality of COSMIC 1D-var water vapor may be further quantified using PW derived from ground-based GPS. This will be for a future study.

  3. Jens Wickert

    Response from Jens Wickert

    I agree with Kevin, we have the ambiguity between dry and wet term of the refractivity, which we get from GPS RO, and only can solve for by additional assumptions or data. But water vapour data product should not be "completely" useless.