From: Volker Wulfmeyer (vow at ucar.edu)
Organization: NCAR/ATD

Research Area: CLIMATE

Mission scenario: Validation of satellite-borne water vapor measurements

Water vapor is the key variable in our understanding of the earth's atmosphere. To investigate the role of water vapor in climate, there is urgent need for accurate spaceborne water vapor measurements (error <5%) with a resolution of 1km vertically and 20x20km horizontally (see e.g. the Global Water Vapor Project (GVaP) Science and Implementation Plan). Particularly there is a large uncertaintly in our knowledge with respect to upper tropospheric humidity (UTH).

HIAPER will be equipped with a new water vapor differential absorption lidar (DIAL), an active remote sensing system which measures water vapor profiles throughout the troposphere with high resolution and accuracy. This system allows for comprehensive intercomparisons with satellite retrievals. As HIAPER will be equipped with additional instrumentation giving the required background information, such as temperature profiles and brightness temperatures, the intercomparisons can lead to an improvement of satellite retrieval techniques.

Flight plan: HIAPER will fly above the tropopause and follow the footprints of polar orbiting satellites such as the NOAA satellites with the TOVS package (in the future also IASI, ADEOS-II and TOMS). The flight track should be as long as possible to reduce sampling and statitical errors.

Instrumentation: Water vapor DIAL, drop sondes, upward and downward looking microwave radiometers as well as IR spectrometers or FTIR.

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