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Title: Mesoscale disturbances in the tropical stratosphere excited by convection: Observations and effects on the stratospheric momentum budget

Abstract

The importance of the momentum flux of topographically generated mesoscale gravity waves to the extratropical middle atmosphere circulation has been well established for over a decade. Estimates of the zonal forcing due to tropical mesoscale gravity waves, however, are hampered by lack of data on their primarily convective sources. The advent of aircraft measurements over tropical convective systems now makes such estimates possible without the use of ad hoc assumptions about amplitudes and phase speeds. Aircraft measurements from NASA's 1980 Panama and 1987 STEP/Australia Missions show that convectively generated disturbances observed just above the tropopause have horizontal scales comparable to those of the underlying anvils (about 50--100 km) with peak-to-peak isentropic surface variations of about 300--400 m. Satellite imagery of tropical anvil evolution indicates a typical lifetime of about five hours. Assuming that each convective system's impact on the stratosphere can be modeled as a time-dependent [open quotes]mountain[close quotes] with the preceding spatial and time scales, the excited spectrum of gravity waves can be calculated. A suitable quasi-linear wave-mean flow interaction parameterization and satellite-derived cloud area statistics can then be used to evaluate the zonal acceleration as a function of altitude induced by gravity waves from mesoscale convective systems. Themore » results indicate maximum westerly accelerations due to breaking mesoscale gravity waves of almost 0.4 m s[sup [minus]1]/day in the upper stratosphere (in the region of the semiannual oscillation) during September, comparable to but probably smaller than the accelerations induced by planetary-scale Kelvin waves. Calculated easterly accelerations due to breaking mesoscale gravity waves in the QBO region below 35 km are smaller, accounting for about 10% of the required zonal acceleration. 35 refs., 14 figs., 1 tab.« less

Authors:
; ;  [1];  [2];  [3]
  1. NASA/Ames Research Center, Moffett Field, CA (United States)
  2. San Jose State Univ., CA (United States)
  3. Synernet, Fremont, CA (United States)
Publication Date:
OSTI Identifier:
6531276
Resource Type:
Journal Article
Journal Name:
Journal of the Atmospheric Sciences; (United States)
Additional Journal Information:
Journal Volume: 50:8; Journal ID: ISSN 0022-4928
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; GRAVITY WAVES; MATHEMATICAL MODELS; STRATOSPHERE; ATMOSPHERIC CIRCULATION; AUSTRALIA; CONVECTION; DATA ANALYSIS; DISTURBANCES; MOMENTUM TRANSFER; PANAMA; TROPICAL REGIONS; TROPOPAUSE; AUSTRALASIA; CENTRAL AMERICA; DEVELOPED COUNTRIES; DEVELOPING COUNTRIES; EARTH ATMOSPHERE; ENERGY TRANSFER; HEAT TRANSFER; LATIN AMERICA; MASS TRANSFER; TROPOSPHERE; 540110*

Citation Formats

Pfister, L, Scott, S, Loewenstein, M, Bowen, S, and Legg, M. Mesoscale disturbances in the tropical stratosphere excited by convection: Observations and effects on the stratospheric momentum budget. United States: N. p., 1993. Web. doi:10.1175/1520-0469(1993)050<1058:MDITTS>2.0.CO;2.
Pfister, L, Scott, S, Loewenstein, M, Bowen, S, & Legg, M. Mesoscale disturbances in the tropical stratosphere excited by convection: Observations and effects on the stratospheric momentum budget. United States. https://doi.org/10.1175/1520-0469(1993)050<1058:MDITTS>2.0.CO;2
Pfister, L, Scott, S, Loewenstein, M, Bowen, S, and Legg, M. 1993. "Mesoscale disturbances in the tropical stratosphere excited by convection: Observations and effects on the stratospheric momentum budget". United States. https://doi.org/10.1175/1520-0469(1993)050<1058:MDITTS>2.0.CO;2.
@article{osti_6531276,
title = {Mesoscale disturbances in the tropical stratosphere excited by convection: Observations and effects on the stratospheric momentum budget},
author = {Pfister, L and Scott, S and Loewenstein, M and Bowen, S and Legg, M},
abstractNote = {The importance of the momentum flux of topographically generated mesoscale gravity waves to the extratropical middle atmosphere circulation has been well established for over a decade. Estimates of the zonal forcing due to tropical mesoscale gravity waves, however, are hampered by lack of data on their primarily convective sources. The advent of aircraft measurements over tropical convective systems now makes such estimates possible without the use of ad hoc assumptions about amplitudes and phase speeds. Aircraft measurements from NASA's 1980 Panama and 1987 STEP/Australia Missions show that convectively generated disturbances observed just above the tropopause have horizontal scales comparable to those of the underlying anvils (about 50--100 km) with peak-to-peak isentropic surface variations of about 300--400 m. Satellite imagery of tropical anvil evolution indicates a typical lifetime of about five hours. Assuming that each convective system's impact on the stratosphere can be modeled as a time-dependent [open quotes]mountain[close quotes] with the preceding spatial and time scales, the excited spectrum of gravity waves can be calculated. A suitable quasi-linear wave-mean flow interaction parameterization and satellite-derived cloud area statistics can then be used to evaluate the zonal acceleration as a function of altitude induced by gravity waves from mesoscale convective systems. The results indicate maximum westerly accelerations due to breaking mesoscale gravity waves of almost 0.4 m s[sup [minus]1]/day in the upper stratosphere (in the region of the semiannual oscillation) during September, comparable to but probably smaller than the accelerations induced by planetary-scale Kelvin waves. Calculated easterly accelerations due to breaking mesoscale gravity waves in the QBO region below 35 km are smaller, accounting for about 10% of the required zonal acceleration. 35 refs., 14 figs., 1 tab.},
doi = {10.1175/1520-0469(1993)050<1058:MDITTS>2.0.CO;2},
url = {https://www.osti.gov/biblio/6531276}, journal = {Journal of the Atmospheric Sciences; (United States)},
issn = {0022-4928},
number = ,
volume = 50:8,
place = {United States},
year = {Thu Apr 15 00:00:00 EDT 1993},
month = {Thu Apr 15 00:00:00 EDT 1993}
}