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Title: Diurnal Forcing and Phase Locking of Gravity Waves in the Maritime Continent

Abstract

Abstract An unfiltered zonal Hovmöller depiction of rainfall in the Maritime Continent (MC) reveals remarkable spatiotemporal continuity of zonally propagating disturbances with a diurnal period, which endure over multiple days and propagate faster than the individual convective storms they coupled with. This phenomenon and its sensitivity to the Madden–Julian oscillation (MJO) during the 2011/12 Dynamics of the MJO (DYNAMO) field campaign is examined here through a well-validated, convection-permitting model simulation conducted on a large domain. We find that these disturbances are zonally propagating diurnal gravity waves excited by vigorous nocturnal mesoscale convective systems over Sumatra and Borneo. These gravity waves are diurnally phase locked: their wavelength very closely matches the distance between these two islands (~1500 km), while their particular zonal phase speed (~±17 m s−1) allows them to propagate this distance in one diurnal cycle. We therefore hypothesize that these waves are amplified by resonant interaction due to diurnal phase locking. While these zonal gravity waves decouple from convection once beyond the MC, their divergent flow signature endures well across the Indian Ocean, provoking the notion that they may influence rainfall at far remote locations. The exact controls over this zonal phase speed remain uncertain; we note, however, thatmore » it is roughly consistent with diurnal offshore-propagating modes documented previously. Further study is required to tie this down, and more generally, to understand the sensitivity of these modes to background flow strength and the geography of the MC.« less

Authors:
 [1];  [1]
  1. Department of Meteorology and Atmospheric Science, and Center for Advanced Data Assimilation and Predictability Techniques, The Pennsylvania State University, University Park, Pennsylvania
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1560257
Grant/Contract Number:  
WACCEM
Resource Type:
Published Article
Journal Name:
Journal of the Atmospheric Sciences
Additional Journal Information:
Journal Name: Journal of the Atmospheric Sciences Journal Volume: 76 Journal Issue: 9; Journal ID: ISSN 0022-4928
Publisher:
American Meteorological Society
Country of Publication:
United States
Language:
English

Citation Formats

Ruppert, Jr., James H., and Zhang, Fuqing. Diurnal Forcing and Phase Locking of Gravity Waves in the Maritime Continent. United States: N. p., 2019. Web. doi:10.1175/JAS-D-19-0061.1.
Ruppert, Jr., James H., & Zhang, Fuqing. Diurnal Forcing and Phase Locking of Gravity Waves in the Maritime Continent. United States. doi:10.1175/JAS-D-19-0061.1.
Ruppert, Jr., James H., and Zhang, Fuqing. Tue . "Diurnal Forcing and Phase Locking of Gravity Waves in the Maritime Continent". United States. doi:10.1175/JAS-D-19-0061.1.
@article{osti_1560257,
title = {Diurnal Forcing and Phase Locking of Gravity Waves in the Maritime Continent},
author = {Ruppert, Jr., James H. and Zhang, Fuqing},
abstractNote = {Abstract An unfiltered zonal Hovmöller depiction of rainfall in the Maritime Continent (MC) reveals remarkable spatiotemporal continuity of zonally propagating disturbances with a diurnal period, which endure over multiple days and propagate faster than the individual convective storms they coupled with. This phenomenon and its sensitivity to the Madden–Julian oscillation (MJO) during the 2011/12 Dynamics of the MJO (DYNAMO) field campaign is examined here through a well-validated, convection-permitting model simulation conducted on a large domain. We find that these disturbances are zonally propagating diurnal gravity waves excited by vigorous nocturnal mesoscale convective systems over Sumatra and Borneo. These gravity waves are diurnally phase locked: their wavelength very closely matches the distance between these two islands (~1500 km), while their particular zonal phase speed (~±17 m s−1) allows them to propagate this distance in one diurnal cycle. We therefore hypothesize that these waves are amplified by resonant interaction due to diurnal phase locking. While these zonal gravity waves decouple from convection once beyond the MC, their divergent flow signature endures well across the Indian Ocean, provoking the notion that they may influence rainfall at far remote locations. The exact controls over this zonal phase speed remain uncertain; we note, however, that it is roughly consistent with diurnal offshore-propagating modes documented previously. Further study is required to tie this down, and more generally, to understand the sensitivity of these modes to background flow strength and the geography of the MC.},
doi = {10.1175/JAS-D-19-0061.1},
journal = {Journal of the Atmospheric Sciences},
number = 9,
volume = 76,
place = {United States},
year = {2019},
month = {9}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: 10.1175/JAS-D-19-0061.1

Citation Metrics:
Cited by: 5 works
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