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Remote sensing measurements of the CO 2 mixing ratio in the planetary boundary layer using cloud slicing with airborne lidar
Author(s) -
Ramanathan Anand K.,
Mao Jianping,
Abshire James B.,
Allan Graham R.
Publication year - 2015
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2014gl062749
Subject(s) - lidar , remote sensing , trace gas , planetary boundary layer , cirrus , absorption (acoustics) , slicing , environmental science , troposphere , mixing ratio , cloud top , boundary layer , geology , atmospheric sciences , optics , satellite , physics , computer science , astronomy , world wide web , thermodynamics
We have measured the CO 2 volume mixing ratio (VMR) within the planetary boundary layer (PBL) using cloud slicing with an airborne pulsed integrated path differential absorption (IPDA) lidar from flight altitudes of up to 13 km. During a flight over Iowa in summer 2011, simultaneous measurement of the optical range and CO 2 absorption to clouds and the ground were made using time‐resolved detection of pulse echoes from each scattering surface. We determined the CO 2 absorption in the PBL by differencing the two lidar‐measured absorption line shapes, one to a broken shallow cumulus cloud layer located at the top of the PBL and the other to the ground. Solving for the CO 2 VMR in the PBL and that of the free troposphere, we measured a ≈15 ppm (4%) drawdown in the PBL. Both CO 2 VMRs were within ≈3 ppm of in situ CO 2 profile measurements. We have also demonstrated cloud slicing using scatter from thin, diffuse cirrus clouds and cumulus clouds, which allowed solving for the CO 2 VMR for three vertical layers. The technique and retrieval algorithm are applicable to a space‐based lidar instrument as well as to lidar IPDA measurements of other trace gases. Thus, lidar cloud slicing also offers promise toward space‐based remote sensing of vertical trace gas profiles in the atmosphere using a variety of clouds.