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Title: Scale Analysis of Moist Thermodynamics in a Simple Model and the Relationship between Moisture Modes and Gravity Waves

Abstract

Observations and theory of convectively coupled equatorial waves suggest that they can be categorized into two distinct groups. Moisture modes are waves whose thermodynamics are governed by moisture fluctuations. The thermodynamics of the gravity wave group, on the other hand, are rooted in buoyancy (temperature) fluctuations. On the basis of scale analysis, it is found that a simple nondimensional parameter—akin to the Rossby number—can explain the processes that lead to the existence of these two groups. This parameter, defined as N mode , indicates that moisture modes arise when anomalous convection lasts sufficiently long so that dry gravity waves eliminate the temperature anomalies in the convective region, satisfying weak temperature gradient (WTG) balance. This process causes moisture anomalies to dominate the distribution of moist enthalpy (or moist static energy), and hence the evolution of the wave. Conversely, convectively coupled gravity waves arise when anomalous convection eliminates the moisture anomalies more rapidly than dry gravity waves can adjust the troposphere toward WTG balance, causing temperature to govern the moist enthalpy distribution and evolution. Spectral analysis of reanalysis data indicates that slowly propagating waves ( c p ~ 3 m s −1 ) are likely to be moisture modes while fast wavesmore » ( c p ~ 30 m s −1 ) exhibit gravity wave behavior, with “mixed moisture–gravity” waves existing in between. While these findings are obtained from a highly idealized framework, it is hypothesized that they can be extended to understand simulations of convectively coupled waves in GCMs and the thermodynamics of more complex phenomena.« less

Authors:
 [1];  [2];  [3];  [4];  [5]
  1. Department of Climate and Space Science and Engineering, University of Michigan, Ann Arbor, Michigan
  2. Department of Atmospheric Sciences, University Of Washington, Seattle, Washington
  3. Program in Atmospheric and Oceanic Sciences, Princeton University, Princeton, New Jersey
  4. NOAA/Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
  5. NASA Goddard Institute for Space Studies, and Lamont-Doherty Earth Observatory, Columbia University, New York, New York
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1575795
Grant/Contract Number:  
SC0019495; KMI2018-03110
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: 12; Journal ID: ISSN 0022-4928
Publisher:
American Meteorological Society
Country of Publication:
United States
Language:
English

Citation Formats

Adames, Ángel F., Kim, Daehyun, Clark, Spencer K., Ming, Yi, and Inoue, Kuniaki. Scale Analysis of Moist Thermodynamics in a Simple Model and the Relationship between Moisture Modes and Gravity Waves. United States: N. p., 2019. Web. doi:10.1175/JAS-D-19-0121.1.
Adames, Ángel F., Kim, Daehyun, Clark, Spencer K., Ming, Yi, & Inoue, Kuniaki. Scale Analysis of Moist Thermodynamics in a Simple Model and the Relationship between Moisture Modes and Gravity Waves. United States. doi:10.1175/JAS-D-19-0121.1.
Adames, Ángel F., Kim, Daehyun, Clark, Spencer K., Ming, Yi, and Inoue, Kuniaki. Sun . "Scale Analysis of Moist Thermodynamics in a Simple Model and the Relationship between Moisture Modes and Gravity Waves". United States. doi:10.1175/JAS-D-19-0121.1.
@article{osti_1575795,
title = {Scale Analysis of Moist Thermodynamics in a Simple Model and the Relationship between Moisture Modes and Gravity Waves},
author = {Adames, Ángel F. and Kim, Daehyun and Clark, Spencer K. and Ming, Yi and Inoue, Kuniaki},
abstractNote = {Observations and theory of convectively coupled equatorial waves suggest that they can be categorized into two distinct groups. Moisture modes are waves whose thermodynamics are governed by moisture fluctuations. The thermodynamics of the gravity wave group, on the other hand, are rooted in buoyancy (temperature) fluctuations. On the basis of scale analysis, it is found that a simple nondimensional parameter—akin to the Rossby number—can explain the processes that lead to the existence of these two groups. This parameter, defined as N mode , indicates that moisture modes arise when anomalous convection lasts sufficiently long so that dry gravity waves eliminate the temperature anomalies in the convective region, satisfying weak temperature gradient (WTG) balance. This process causes moisture anomalies to dominate the distribution of moist enthalpy (or moist static energy), and hence the evolution of the wave. Conversely, convectively coupled gravity waves arise when anomalous convection eliminates the moisture anomalies more rapidly than dry gravity waves can adjust the troposphere toward WTG balance, causing temperature to govern the moist enthalpy distribution and evolution. Spectral analysis of reanalysis data indicates that slowly propagating waves ( c p ~ 3 m s −1 ) are likely to be moisture modes while fast waves ( c p ~ 30 m s −1 ) exhibit gravity wave behavior, with “mixed moisture–gravity” waves existing in between. While these findings are obtained from a highly idealized framework, it is hypothesized that they can be extended to understand simulations of convectively coupled waves in GCMs and the thermodynamics of more complex phenomena.},
doi = {10.1175/JAS-D-19-0121.1},
journal = {Journal of the Atmospheric Sciences},
number = 12,
volume = 76,
place = {United States},
year = {2019},
month = {12}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: 10.1175/JAS-D-19-0121.1

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