Identification

Title

Evidence for the influence of the Quasi-Biennial Oscillation on the Semiannual Oscillation in the tropical middle atmosphere

Abstract

The semiannual oscillation (SAO) in zonally averaged zonal winds develops just above the quasi-biennial oscillation (QBO) and dominates the seasonal variability in the tropical upper stratosphere and lower mesosphere. The magnitude, seasonality, and latitudinal structure of the SAO vary with the phase of the QBO. There is also an an-nual oscillation (AO) whose magnitude at the equator is smaller than those of the SAO and QBO but not negligible. This work presents the relation between the SAO, QBO, AO, and time-mean wind in the tropical upper stratosphere and lower mesosphere using winds derived from satellite geopotential height observations. The winds are generally more westerly during the easterly phase of the QBO. The SAO extends to lower altitudes during periods where the QBO is characterized by deep easterly winds. The differences in the SAO associated with the QBO are roughly con-fined to the latitudes where the QBO has appreciable amplitude, suggesting that the mechanism is controlled by verti-cal coupling. The westerly phases of the SAO and AO show downward propagation with time. This analysis suggests that forcing by dissipation of waves with westerly momentum is responsible for the westerly acceleration of both the SAO and AO. The timing and structure of the easterly phases of the SAO and AO near the stratopause are consistent with the response to meridional advection of momentum across the equator during solstices; it is not apparent that lo-cal wave processes play important roles in the easterly phases in the region of the stratopause.

Resource type

document

Resource locator

Unique resource identifier

code

http://n2t.net/ark:/85065/d7736vx2

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

2023-07-01T00:00:00Z

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

Copyright 2023 American Meteorological Society (AMS).

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

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 date

2023-08-18T19:23:28.436834

Metadata language

eng; USA