Global and Regional Water Vapor Variability from the New NASA Water Vapor Project-MEaSUREs (NVAP-M) Dataset

The depiction of global water vapor and its variability is made possible by a wide variety of observing systems, each with its own strengths and limitations. Passive microwave satellite systems historically measure the total column amount over ocean only, infrared water vapor retrievals are only available over clear regions, and ground-based measurements are limited in time and space. Assembling these parts and leveraging their strengths to create a global record of water vapor is a challenge. The NASA Water Vapor Project (NVAP) dataset is a global (land and ocean) water vapor dataset created by merging multiple sources of atmospheric water vapor to form global gridded fields of total and layered precipitable water vapor. Under the NASA Making Earth Science Data Records for Research Environments (MEaSUREs) program, NVAP has been reprocessed and extended, increasing its 14-year coverage to include 22 years (1988-2009) of data. NVAP-M is available globally at either daily, 1 degree or 6-hourly, ½ degree resolution. It is observationally driven, with minimal dependence on numerical model fields, making it useful for comparison to models. Preliminary analysis of the NVAP-M shows considerable variability in both total precipitable water (TPW) and layered water vapor at both global and regional scales. Water vapor variability on daily, interannual, and decadal time scales will be discussed and comparisons of the behavior of water vapor with that of other atmospheric variables (e.g. temperature) will be made. The challenges in creating a consistent, multi-decadal climate record of water vapor will also be discussed.