October 18, 2013

POLDER 2 - WATER VAPOR CONTENT

WATER VAPOR CONTENT



The total column water vapor content (TCWV) is retrieved in clear-sky conditions from two channels located beside and in an H2O gaseous absorption band (respectively 865 and 910 nm). Assuming that the surface reflectance variation is small between these two close bands, the 910 to 865 nm reflectance ratio is a function of the atmosphere transmission which is related to the water vapor content. This relation is parameterized with a polynomial fit, whose coefficients were determined by using SSM/I TCWV collocated observations over ocean. Spectral variations of the land surface reflectivity are accounted for by a correction factor using the atmospheric window 765 and 865 nm reflectances. Water vapor retrieval are performed for all clear-sky pixels over land and for clear-sky and specular reflexion (glint) situations over ocean.

A more complete description can be downloaded from the "ERB, WV & clouds" algorithm documents for POLDER-2. If there are further questions regarding the water vapor content derivation, please contact Dr. M. Vesperini (at LOA).

See below the main parameters related to water vapor content that appear in the level-2 POLDER "ERB, WV & clouds" product.

UH2OTotal column precipitable water vapor of the clear part of the superpixel [g cm-²]
Click to view image
SD(UH2O)Standard Deviation of water vapor estimates [g cm-²]

See below the main parameters related to water vapor content that appear in the level-3 POLDER "ERB, WV & clouds" product.

M(UH2O)Monthly mean of the total column precipitable water vapor [g cm-²].
Click to view image
TD(UH2O)Temporal standard Deviation of the total column precipitable water vapor [g cm-²].


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