Monitoring CO 2 Sources and Sinks from Space with the Orbiting Carbon Observatory (OCO)

Transcription

1 NACP Remote Sensing Breakout Monitoring CO 2 Sources and Sinks from Space with the Orbiting Carbon Observatory (OCO) David Crisp, OCO PI (JPL/Caltech) January of 14, Crisp, NACP 2007 Page 1

2 What Processes Control Atmospheric CO 2? Carbon dioxide (CO 2 ) is the main: Atmospheric component of the global carbon cycle essential to life Man-made greenhouse gas CO 2 (parts per million) Only half of the CO 2 emitted by human activities is remaining in the atmosphere 2 of 14, Crisp, NACP 2007 Page 2

3 The Orbiting Carbon Observatory (OCO) OCO will acquire the space-based data needed to identify CO 2 sources and sinks and quantify their variability over the seasonal cycle Approach: Collect spectra of CO 2 and O 2 absorption in reflected sunlight over the sunlit hemisphere Use these data to resolve spatial and temporal variations in the column averaged CO 2 dry air mole fraction, X CO2 Validate measurements to ensure X CO2 accuracies of 1-2 ppm ( %) on regional scales at monthly intervals 3 of 14, Crisp, NACP 2007 Page 3

4 What is X CO2? Measured Spectra CO 2 O 2 Column Abundance Path Dependent Ratio X CO2 Path Independent Mixing Ratio 4 of 14, Crisp, NACP 2007 Page 4

5 Precise Measurements are Needed to Characterize CO 2 Sources and Sinks 380 X CO2 Precisions of ppm ( %) on regional scales could: Resolve pole to pole X CO2 gradients on Resolve regional (8ppm) scales pole to pole X CO2 Resolve gradients the on X CO2 regional seasonal scales cycle in the Resolve Northern the Hemisphere X CO2 seasonal cycle in the Northern Hemisphere Reduce surface CO 2 flux errors by about a factor of 10 5 of 14, Crisp, NACP 2007 Page 5 372

6 Making Precise CO 2 Measurements from Space High resolution spectra of reflected sunlight in near IR CO 2 and O 2 bands used to retrieve the column average CO 2 dry air mole fraction, X CO μm CO 2 band: Column CO μm CO 2 band: Column CO 2, Aerosols 0.76 μm O 2 A-band: Surface pressure, clouds, aerosols Why high spectral resolution? Enhances sensitivity, minimizes biases O 2 A-band CO μm CO μm Clouds/Aerosols, Surface Pressure Column CO 2 6 of 14, Crisp, NACP 2007 Clouds/Aerosols, H 2 O, Temperature Page 6

7 OCO Mission Implementation Approach Project Management (JPL) Single Instrument (Hamilton Sundstrand) Dedicated Spacecraft Bus (Orbital Sciences) Dedicated Taurus 3110 Launch Vehicle (Orbital) Mission Operations (JPL/Orbital Sciences) September 2008 Launch from Vandenberg AFB 7 of 14, Crisp, NACP 2007 Page 7

8 OCO Will Fly in the A-Train Coordinated Observations 1:26 aerosols, polarization TES T, P, H 2 O, O 3, CH 4, CO MLS O 3, H 2 O, CO HIRDLS T, O 3, H 2 O, CO 2, CH 4 OMI O 3, aerosol climatology CloudSat 3-D cloud climatology CALIPSO 3-D aerosol climatology AIRS T, P, H 2 O, CO 2, CH 4 MODIS cloud, aerosols, albedo OCO --CO 2 O 2 A-band p s, clouds, aerosols OCO files at the head of the A-Train, 4 minutes ahead of the Aqua platform 8 of 14, Crisp, NACP 2007 Page 8

9 OCO Observing Strategy Observing Modes Nadir Observations: tracks local nadir + Small footprint (< 3 km 2 ) isolates cloudfree scenes Low Signal/Noise over dark ocean Glint Observations: views glint spot + Improves Signal/Noise over oceans More interference from clouds Target Observations Tracks a stationary surface target to collect large numbers of soundings Data acquisition schedule: alternate between Nadir and Glint on 16-day intervals Acquire ~1 Target observation each day Glint Spot Ground Track Local Nadir 9 of 14, Crisp, NACP 2007 Page 9

10 OCO Sampling over a 16-Day Repeat Cycle Prevailing Winds OCO Sampling Rate/Coverage Glint: +75 o SZA, Nadir: +85 o SZA Longitude resolution 1.5 o samples/second collected along track over land and ocean 200 to 400 samples per degree of latitude along orbit track on day side of the Earth 7 and 14 million soundings over the globe once every 16 days. OCO 1-Day OCO 3-Days OCO Spatial Sampling Approach Measurements are collected along narrow ground tracks Subsequent orbit tracks are separated by ~24 o longitude 10 of 14, Crisp, NACP 2007 Clouds reduce number of usable samples Chevallier et al Page 10

11 Single Sounding Sensitivity Nadir Nadir Glint Nadir Nadir vs Glint over Ocean Nadir Combination of Glint and Nadir observations provides high sensitivity even over dark surfaces. 11 of 14, Crisp, NACP 2007 Page 11

12 Each OCO sounding describes the average mixing ratio along Horizontal Footprints an incoming optical path between the surface measurement footprint and the sun, an outgoing optical path that extends from the surface footprint and the spacecraft. θ o High resolution source-sink inversion calculations must account for the effective horizontal projections of the X CO2 columns retrieved from OCO data Incoming and outgoing components of a single Nadir sounding 12 of 14, Crisp, NACP 2007 Page 12

13 Space-based X CO2 Validation Strategy Ensures Accuracy and Early Acceptance A rigorous validation approach will speed acceptance of OCO data by the Science Community The space-based measurements must be validated against the surface CO 2 standard Selected Pending Global X CO2 FTS Network CO 2 Ground Network 13 of 14, Crisp, NACP 2007 Page 13

14 OCO Fills a Critical Measurement Gap CO 2 Error (ppm) ENVISAT SCIAMACHY Aqua AIRS NOAA TOVS GOSAT Flask Site 10 Flux Tower Aircraft OCO Spatial Scale (km) Globalview Network 14 of 14, Crisp, NACP 2007 Page 14