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Global 3-D climatology of atmospheric water vapor from space borne radiometric measurements


Major programmes issued by the international community (in
particular GEWEX - Global Energy and Water EXperiment) have
addressed fundamental deficiencies in the present understanding
of moist atmospheric processes and the role of the water budget
in meteorology and climatology. In particular, the lack of a
comprehensive and accurate global moisture data set is hampering
essential studies in atmospheric and climate sciences. The
project aims to produce such a dataset.

Methods to infer atmospheric water vapour or liquid water include
spaceborne remote sensors, upper-air sondes, surface and airborne
in-situ sensors. Each of these have strengths and weaknesses
mainly related to the accuracy, the vertical and spatial
resolutions, the spatial and temporal coverage.

Although the present capabilities are limited in some important
respects, it is now well recognized that the value of an even not
perfect distribution of the global description of the water
vapour is extremely high at this time.

We propose to take full advantage of the above mentioned methods
to derive a climatology of the global distribution of the water
vapour/liquid using a combination of satellite observations
(TOVS- HIRS and MSU, SSM-I, AVHRR) and other determinations
(radiosondes, analyses, and ground-based lidar).

This climatology will span over a two year period and will be
complemented by simultaneously retrieved atmospheric and surface
parameters: air mass type, cloud and rain detection, temperature
profiles, cloud parameters, surface temperature and
characteristics - sea ice, snow -.

The complementarity of TOVS and SSM-I will make this analysis as
complete as possible (ocean, land, sea-ice).

The spatial/temporal resolution of the output products will be a
compromise between the resolutions of the various components
entering the water monitoring of this study: TOVS, SSM-I and
AVHRR retrievals, radiosondes measurements, analyses products,

Furthermore we intend to assess the accuracy of the derived
products from measurement intercomparisons. Such intercomparison
experiments will aim at developing a full quantitative
characterization of each of the various sensing/measuring
systems. This cross- checking between the accuracies may lead to
updatings and improvements of the presently available algorithms:
this is also part of our proposal.

The coming microwave sounders (AMSU-A and B) and the high
spectral resolution infrared sounders (IASI/CNES-ASI/ESA,
AIRS/EOS/NASA) should provide enhanced vertical resolution. We
propose to analyze the requirements for the definition of new
algorithms capable of matching the expected performances from
these new sensors.

Funding Scheme

CSC - Cost-sharing contracts


Ecole Polytechnique
91128 Palaiseau

Participants (3)

Consiglio Nazionale delle Ricerche (CNR)
Contrada S. Loya
85050 Tito Scalo Potenza
Bundesstrasse 55
20146 Hamburg
5,Princetonplein 5
3584 CC Utrecht