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NASA Technical Reports Server (NTRS) 20160006490: Lidar Observation...
by NASA Technical Reports Server (NTRS)
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Advanced knowledge in atmospheric CO2 is critical in
reducing large uncertainties in predictions of the Earth'
future climate. Thus, Active Sensing of CO2 Emissions
over Nights, Days, and Seasons (ASCENDS) from space was
recommended by the U.S. National Research Council to
NASA. As part of the preparation for the ASCENDS mission,
NASA Langley Research Center (LaRC) and Exelis, Inc. have
been collaborating in development and demonstration of
the Intensity-Modulated Continuous-Wave (IM-CW) lidar
approach for measuring atmospheric CO2 column from space.
Airborne laser absorption lidars such as the Multi-
Functional Fiber Laser Lidar (MFLL) and ASCENDS
CarbonHawk Experiment Simulator (ACES) operating in the
1.57 micron CO2 absorption band have been developed and
tested to obtain precise atmospheric CO2 column
measurements using integrated path differential
absorption technique and to evaluate the potential of the
space ASCENDS mission. This presentation reports the
results of our lidar atmospheric CO2 column measurements
from 2014 summer flight campaign. Analysis shows that for
the 27 Aug OCO-2 under flight over northern California
forest regions, significant variations of CO2 column
approximately 2 ppm) in the lower troposphere have been
observed, which may be a challenge for space measurements
owing to complicated topographic condition, heterogeneity
of surface reflection and difference in vegetation
evapotranspiration. Compared to the observed 2011 summer
CO2 drawdown (about 8 ppm) over mid-west, 2014 summer
drawdown in the same region measured was much weak
(approximately 3 ppm). The observed drawdown difference
could be the results of the changes in both
meteorological states and the phases of growing seasons.
Individual lidar CO2 column measurements of 0.1-s
integration were within 1-2 ppm of the CO2 estimates
obtained from on-board in-situ sensors. For weak surface
reflection conditions such as ocean surfaces, the 1- s
integrated signal-to-noise ratio (SNR) of lidar
measurements at 11 km altitude reached 376, which was
equivalent to a 10-s CO2 error 0.33 ppm. For the entire
processed 2014 summer flight campaign data, the mean
differences between lidar remote sensed and in-situ
estimated CO2 values were about -0.013 ppm. These results
indicate that current laser absorption lidar approach
could meet space measurement requirements for CO2 science
goals.
Date Published: 2016-11-19 02:10:40
Identifier: NASA_NTRS_Archive_20160006490
Item Size: 15357624
Language: english
Media Type: texts
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