Spaceborne measurements of atmospheric CO2 by high-resolution NIR spectrometry
of reflected sunlight: An introductory study
Kuang, Z., J. Margolis, G. C. Toon, D. Crisp, Y. L. Yung
GEOPHYSICAL RESEARCH LETTERS, VOL. 29, NO. 15, 10.1029/2001GL014298, 2002
We introduce a strategy for measuring the column-averaged CO2 dryair volume
mixing ratio XCO2 from space. It employs high resolution spectra of reflected
sunlight taken simultaneously in near-infrared (NIR) CO2 (1.58-µm
and 2.06-µm) and O2 (0.76-µm) bands. Simulation experiments,
show that precisions of ~0.3-2.5 ppmv for XCO2 can be achieved from individual
clear sky soundings for a range ofatmospheric/surface conditions when the
scattering optical depth is less than ~0.3. When averaged over many clear
sky soundings, random errors become negligible. This high precision facilitates
the identification and correction of systematic errors, which are recognized
as the most serious impediment for the satellite XCO2 measurements. We
briefly discuss potential sources of systematic errors, and show that some
of them may result in geographically varying biases in the measured XCO2.
This highlights the importance of careful calibration and validation measurements,
designed to identify and eliminate sources of these biases. We conclude
that the 3-band, spectrometric approach using NIR reflected sunlight has
the potential for highly accurate XCO2 measurements.
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Zhiming Kuang <firstname.lastname@example.org>