NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
LASE validation experiment: preliminary processing of relative humidity from LASE derived water vapor in the middle to upper troposphereLidar Atmospheric Sensing Experiment (LASE) is the first fully engineered, autonomous airborne DIAL (Differentials Absorption Lidar) system to measure water vapor, aerosols, and clouds throughout the troposphere. This system uses a double-pulsed Ti:sapphire laser, which is pumped by a frequency-doubled flashlamp-pumped Nd: YAG laser, to transmit light in the 815 mn absorption band of water vapor. LASE operates by locking to a strong water vapor line and electronically tuning to any spectral position on the absorption line to choose the suitable absorption cross-section for optimum measurements over a range of concentrations in the atmosphere. During the LASE Validation Experiment, which was conducted over Wallops Island during September, 1995, LASE operated on either the strong water line for measurements in middle to upper troposphere, or on the weak water line for measurements made in the middle to lower troposphere including the boundary layer. Comparisons with water vapor measurements made by airborne dew point and frost point hygrometers, NASA/GSFC (Goddard Space Flight Center) Raman Lidar, and radiosondes showed the LASE water vapor mixing ratio measurements to have an accuracy of better than 6% or 0.01 g/kg, whichever is larger, throughout the troposphere. In addition to measuring water vapor mixing ratio profiles, LASE simultaneously measures aerosol backscattering profiles at the off-line wavelength near 815 nm from which atmospheric scattering ratio (ASR) profiles are calculated. ASR is defined as the ratio of total (aerosol + molecular) atmospheric scattering to molecular scattering. Assuming a region with very low aerosol loading can be identified, such as that typically found just below the tropopause, then the ASR can be determined. The ASR profiles are calculated by normalizing the scattering in the region containing enhanced aerosols to the expected scattering by the "clean" atmosphere at that altitude. Images of the total ASR clearly depict cloud regions, including multiple cloud layers, thin upper level cirrus, etc., throughout the troposphere. New data products that are being derived from the LASE aerosol and water measurements include: 1) aerosol extinction coefficient, 2) aerosol optical thickness, 3) precipitable water vapor, and 4) relative humidity (RH). These products can be compared with airborne in-situ, and ground and satellite remote sensing measurements,. This paper presents a preliminary examination of RH profiles in the middle to upper troposphere that are generated from LASE measured water vapor mixing ratio profiles coupled with rawinsonde profiles of temperature and pressure.
Document ID
19980227689
Acquisition Source
Langley Research Center
Document Type
Conference Paper
Authors
Brackett, Vincent G.
(Science Applications International Corp. Hampton, VA United States)
Ismail, Syed
(NASA Langley Research Center Hampton, VA United States)
Browell, Edward V.
(NASA Langley Research Center Hampton, VA United States)
Kooi, Susan A.
(Science Applications International Corp. Hampton, VA United States)
Clayton, Marian B.
(Science Applications International Corp. Hampton, VA United States)
Ferrare, Richard A.
(NASA Langley Research Center Hampton, VA United States)
Minnis, Patrick
(NASA Langley Research Center Hampton, VA United States)
Getzewich, Brian J.
(Computer Sciences Corp. Hampton, VA United States)
Staszel, Jennifer
(Michigan Univ. Ann Arbor, MI United States)
Date Acquired
August 18, 2013
Publication Date
July 1, 1998
Publication Information
Publication: Nineteenth International Laser Radar Conference
Subject Category
Environment Pollution
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
Document Inquiry

Available Downloads

There are no available downloads for this record.
No Preview Available