Identification

Title

Convective momentum transport associated with the Madden-Julian Oscillation based on a reanalysis dataset

Abstract

A better understanding of multiscale interactions within the Madden-Julian oscillation (MJO), including momentum exchanges, is critical for improved MJO prediction skill. In this study, convective momentum transport (CMT) associated with the MJO is analyzed based on the NOAA Climate Forecast System Reanalysis (CFSR). A three-layer vertical structure associated with the MJO, as previously suggested in the mesoscale momentum tendency profile based on global cloud-resolving model simulations, is evident in the subgrid-scale momentum tendency from the CFSR. Positive (negative) subgrid-scale momentum tendency anomalies are found near the surface, negative (positive) anomalies are found in the low to midtroposphere, and positive (negative) anomalies in the upper troposphere are found within and to the west (east) of the MJO convection. This tends to damp the MJO circulation in the free atmosphere, while enhancing MJO winds near the surface. In addition, it could also reduce the MJO eastward propagation speed and lead to the backward tilt with height in the observed MJO structure through a secondary circulation near the MJO center. Further analyses illustrate that this three-layer vertical structure in subgrid-scale momentum tendency largely balances the grid-scale momentum transport of the zonal wind component u, mainly through the transport of seasonal mean u by the MJO-scale vertical motion. Synoptic-scale systems, which were previously proposed to be essential for the u-momentum transport of the MJO, however, are found to play a minor role for the total grid-scale momentum tendency. The above momentum tendency structure is also confirmed with the ECMWF analysis for the Year of Tropical Convection (YOTC) that lends confidence to these above results based on the CFSR.

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document

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http://n2t.net/ark:/85065/d7xp764b

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Dataset language

eng

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geoscientificInformation

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title

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reference date

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publication

effective date

2016-01-01T00:00:00Z

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publication

effective date

2015-07-15T00:00:00Z

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Copyright 2015 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be "fair use" under Section 107 or that satisfies the conditions specified in Section 108 of the U.S. Copyright Law (17 USC, as revised by P.L. 94-553) does not require the Society's permission. Republication, systematic reproduction, posting in electronic form on servers, or other uses of this material, except as exempted by the above statements, requires written permission or license from the AMS. Additional details are provided in the AMS Copyright Policies, available from the AMS at 617-227-2425 or amspubs@ametsoc.org. Permission to place a copy of this work on this server has been provided by the AMS. The AMS does not guarantee that the copy provided here is an accurate copy of the published work.

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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

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pointOfContact

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