Identification

Title

On the secular trend of COx and CO₂ in the lower thermosphere

Abstract

An analysis of recent observations (2004-2013) made by the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) instrument indicate that total carbon (COx = CO + CO₂) has been increasing rapidly in the lower thermosphere, above 10-3 hPa (90 km). The estimated trend (~9% per decade) is about a factor of 2 larger than the rate of increase that can be ascribed to anthropogenic emissions of CO₂ (~5% per decade). Here we investigate whether the observed trends of CO₂ and COx can be reproduced using the Whole Atmosphere Community Climate Model (WACCM), a comprehensive global model with interactive chemistry, wherein vertical eddy diffusion is estimated from a parameterization of gravity wave breaking that can respond to changes in the model climate. We find that the modeled trends of CO₂ and COx do not differ significantly at any altitude from the value expected from anthropogenic increases of CO₂ and that WACCM does not produce significant changes in eddy diffusivity. We show that the discrepancy between model and observations cannot be attributed to uncertainties associated with geophysical noise and instrumental effects, to difficulties separating a linear trend from the 11 year solar signal, or to sparse sampling by ACE-FTS. Estimates of the impact of vertical diffusion on CO₂ in the model indicate that a large increase in Kzz (~30% per decade) would be necessary to reconcile WACCM results with observations. It might be possible to ascertain whether such a large change in vertical mixing has in fact taken place by examining the trend of water vapor in the upper mesosphere.

Resource type

document

Resource locator

Unique resource identifier

code

http://n2t.net/ark:/85065/d7t72k0s

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

2016-04-16T00:00:00Z

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