Identification

Title

Regional widening of tropical overturning: Forced change, natural variability, and recent trends

Abstract

The width of the tropical Hadley circulation (HC) has garnered intense interest in recent decades, owing to the emerging evidence for its expansion in observations and models and to the anticipated impacts on surface climate in its descending branches. To better clarify the causes and impacts of tropical widening, this work generalizes the zonal mean HC to the regional level by defining meridional overturning cells (RC) using the horizontally divergent wind. The edges of the RC are more closely connected to surface hydroclimate than more traditional metrics of regional tropical width (such as the sea level pressure ridge) or even than the zonal mean HC. Simulations reveal a robust weakening of the RC in response to greenhouse gas increases, along with a widening of the RC in some regions. For example, simulated widening of the zonal mean HC in the Southern Hemisphere appears to arise in large part from regional overturning anomalies over the Eastern Pacific, where there is no clear RC. Unforced interannual variability in the position of the zonal mean HC edge is associated with a more general regional widening. These distinct regional signatures suggest that the RCs may be well suited for the attribution of observed circulation trends. The spatial pattern of regional meridional overturning trends in reanalyses corresponds more closely to the pattern associated with unforced interannual variability than to the pattern associated with CO2 forcing, suggesting a large contribution of natural variability to the recent observed tropical widening trends.

Resource type

document

Resource locator

Unique resource identifier

code

http://n2t.net/ark:/85065/d7v127zf

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

2019-06-27T00:00:00Z

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