Have a look to this website of the IUP Bremen: http://www.iup.uni-bremen.de/amcdoas/

Here you can find links to data and also relevant literature.

You're talking about the Precipitable water:

http://www.esrl.noaa.gov/psd/data/gridded/data.ncep.reanalysis2.surface.html

Guilherme.

Thank you Dr. Wittrock and Dr. Martins

Can you explain how the water path can be related to pollution events?

Dear Sir I want to speculate if there is a relation between increase in water vapour which might have played a role in reducing the pollutant concentration.

Air pollution is a phenomenon at the surface. The concentrations of pollutants are high when the bottom layer of the atmosphere is very thin, in other words when its vertical extent is small, in the order of hundreds of meters or even less. The LWP is the total amount of water vapor in the whole of the vertical column; I therefore do not see that there is a relation between the two.

In addition: air pollution is related to high humidities, specifically fog. The reason is that in such situations the layer is stagnant.

You can get IASI satellite measurements on this link :

http://www.pole-ether.fr/etherTypo/index.php?id=1584&L=1

Here are two links for GOME, SCIAMACHY and GOME-2 H2O maps, documentation etc.

http://atmos.eoc.dlr.de/gome2/index_gome2b.html

http://www.globvapour.info/

For downloading GOME-2 L2 H2O data (after registration by email at: [email protected]):

ftp://[email protected]/gome2ol/

You have to decide whether you want precipitable water (PW) data for a specific site or on average for a grid cell. In the former case, you might use observations from GPS-PW sites, AERONET or SKYNET sunphotometers, or radiosondes. Obviously, such observations may or may not exist at the specific location of interest.

Sources of gridded data are plenty, as already covered in previous answers. I would add the one I like most, from the NASA-MERRA reanalysis, which covers the period since 1979 to now at a relatively fine spatial resolution of 1/2x2/3° and a hourly temporal resolution.

PW data are also available at various sites around the world from the Atmospheric Radiation Measurement (ARM) Climate Research Facility program. See:

http://www.arm.gov/measurements/precipwater

Measurements from microwave radiometers are of particular interest, as they provide "all weather" observations, and pretty accurate when interested in integrated quantities such as PW.