Identification

Title

Observational evidence of 3-D cloud effects in OCO-2 CO2 retrievals

Abstract

The standard deviations of the distributions of Orbiting Carbon Observatory (OCO-2) measurements of CO2 (i. e., XCO2) increase in size in the presence of clouds. XCO2 and Moderate Resolution Imaging Spectroradiometer (MODIS) radiance and cloud fields, and OCO-2 A-band radiances, are analyzed in order to determine if this behavior is best described as a radiance-level retrieval artifact or by 3-D radiative transfer effects. Observations in clear-sky and fair weather cumulus scenes are analyzed. Scatter diagrams of XCO2 versus MODIS (and OCO-2) radiances are presented, and averages are calculated for each scene for several radiance bins. The averages vary little in clear skies but decrease markedly for cloudy scenes as radiances increase. These decreases are consistent with an interpretative framework provided by 3-D SHDOM radiative transfer calculations. Two 3-D metrics,.XCO2 and Have, are calculated and applied..XCO2 is the difference in XCO2 for the smallest and largest radiance bins. Have is a measure of the heterogeneity of the cloud radiance field. Lines of XCO2 and MODIS radiance for four target mode scenes have different slopes for clear and cloudy scenes, contrary to the radiance-level retrieval artifact interpretation. In contrast, the graph of.XCO2 and MODIS Have for the various scenes has a linear correlation coefficient of 0.92, consistent with the 3-D interpretation. Since the OCO-2 measurement requirement is 1 ppmv, the cloudy scene XCO2 standard deviations between 1.2 and 2.6 ppmv indicate that 3-D cloud effects add an important component to the XCO2 error budget.

Resource type

document

Resource locator

Unique resource identifier

code

http://n2t.net/ark:/85065/d7gt5qp9

codeSpace

Dataset language

eng

Spatial reference system

code identifying the spatial reference system

Classification of spatial data and services

Topic category

geoscientificInformation

Keywords

Keyword set

keyword value

Text

originating controlled vocabulary

title

Resource Type

reference date

date type

publication

effective date

2016-01-01T00:00:00Z

Geographic location

West bounding longitude

East bounding longitude

North bounding latitude

South bounding latitude

Temporal reference

Temporal extent

Begin position

End position

Dataset reference date

date type

publication

effective date

2017-07-11T00:00:00Z

Frequency of update

Quality and validity

Lineage

Conformity

Data format

name of format

version of format

Constraints related to access and use

Constraint set

Use constraints

Limitations on public access

None

Responsible organisations

Responsible party

contact position

OpenSky Support

organisation name

UCAR/NCAR - Library

full postal address

PO Box 3000

Boulder

80307-3000

email address

opensky@ucar.edu

web address

http://opensky.ucar.edu/

name: homepage

responsible party role

pointOfContact

Metadata on metadata

Metadata point of contact