HR: 1340h
AN: A13D-1505    [Abstracts]
TI: The Orbiting Carbon Observatory Mission: Fast Polarization Calculations Using the R-2OS Radiative Transfer Model
AU: * Natraj, V
EM: vijay@gps.caltech.edu
AF: California Institute of Technology, Department of Planetary Sciences, MC 150-21, 1200 E California Blvd, Pasadena, CA 91125, United States
AU: Boesch, H
EM: hartmut.boesch@le.ac.uk
AF: University of Leicester, Department of Physics and Astronomy, University Rd, Leicester, LE1 7RH, United Kingdom
AU: Spurr, R J
EM: rtsolutions@verizon.net
AF: RT Solutions Inc., 9 Channing St, Cambridge, MA 02138, United States
AU: Yung, Y L
EM: yly@gps.caltech.edu
AF: California Institute of Technology, Department of Planetary Sciences, MC 150-21, 1200 E California Blvd, Pasadena, CA 91125, United States
AB: The Orbiting Carbon Observatory (OCO) mission was proposed to quantify the sources and sinks of CO₂ by making highly precise measurements of its column abundance. The OCO spectrometers measure absorption of reflected sunlight at the top of the atmosphere (TOA) in three narrowband near infrared (NIR) spectral regions. The high precision requirements in conjunction with the polarization sensitivity of the instrument make it essential to account for polarization in the retrieval algorithm. We use a fast polarization correction algorithm based on the assumption that only two scattering events (two orders of scattering, 2OS) contribute to polarization. The 2OS model was used in conjunction with a scalar RT model (Radiant) to simulate OCO backscatter measurements. Computations were performed for different sites and seasons, spanning a variety of surface and aerosol types. The nadir (high spatial resolution) and glint (high signal to noise ratio over ocean) modes of operation were simulated. The aerosol extinction was also varied. The radiance errors using the Radiant/2OS (R-2OS) RT model are an order of magnitude (or more) smaller than errors arising from the use of the scalar model alone. Further, a linear error analysis study show that the errors in the retrieved column-averaged dry air mole fraction of CO₂ ( X_CO2) using the R-2OS model are much lower than the "measurement" noise and smoothing errors appearing in the inverse model. On the other hand, use of the scalar model alone induces errors that could dominate the retrieval error budget. The 2OS computation is also an order of magnitude faster than a full multiple scattering scalar calculation.
DE: 0360 Radiation: transmission and scattering
DE: 1640 Remote sensing (1855)
DE: 3359 Radiative processes
DE: 3360 Remote sensing
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting