A global water vapor data set obtained by merging the SSMI and MODIS data

[1] At present, the column amount of atmospheric water vapor over clear land surfaces and over oceanic areas with sun glint is operationally retrieved from radiances measured with near-IR channels of the Moderate Resolution Imaging SpectroRadiometer (MODIS) instruments on board the NASA Terra and Aqua Spacecraft platforms. TPW over oceans has also been derived operationally from radiances measured by the Special Sensor Microwave Imagers (SSMI) on board different spacecraft. We report in this letter that a global water vapor data product with improved quality can be obtained by merging the monthly-mean MODIS near-IR TPW data over land and the SSMI TPW data over water surfaces. Major characteristics of the seasonal variations of TPW are described. Examples of water vapor anomalies associated with the 2002 El Nino event are presented. We expect that the merged TPW data product will have useful applications for the study of the global hydrological cycle.