Impact of a convectively forced gravity wave drag parameterization in NCAR CCM3

Hye Yeong Chun, In Sun Song, Jong Jin Baik, Young Joon Kim

Research output: Contribution to journalArticle

33 Citations (Scopus)

Abstract

A parameterization of gravity wave drag forced by subgrid-scale cumulus convection (GWDC) proposed by Chun and Baik is implemented into the National Center for Atmospheric Research Community Climate Model (NCAR CCM3) and its effect on perpetual January and July climate is investigated. The cloud-top gravity wave stress is concentrated in the intertropical convergence zone where persistent deep cumulus clouds exist. The resultant zonal wind acceleration due to the breaking of convectively forced gravity waves is predominantly found in the tropical lower stratosphere with westerly acceleration above cloud top and easterly acceleration just below it. Since the parameterized gravity waves are stationary relative to convective clouds, wave breaking occurs mainly in the tropical lower stratosphere where the zonal wind is weak enough for wave saturation. It is shown that the GWDC parameterization significantly alleviates the systematic model biases of zonal-mean zonal wind and temperature. In particular, excessive easterlies in the tropical stratosphere and excessive cold temperatures in the tropical lower stratosphere are reduced by more than 50% by including the GWDC parameterization. The horizontal wind divergence field in the tropical upper troposphere and lower stratosphere is also significantly improved with the GWDC parameterization. The impact of the GWDC parameterization extends to mid- to high latitudes through planetary wave activity in the winter hemisphere. The increased amplitude of zonal wavenumber 3 in the January Northern Hemisphere and the increased amplitude of zonal wavenumber 2 in the July Southern Hemisphere lead to significant improvements in model performance. The impact of the GWDC parameterization on Eliassen-Palm (EP) flux divergence forcing by stationary waves is generally opposite to that by transient waves in the extratropics, especially in the Northern Hemisphere wintertime. Hence, the zonal-mean zonal wind change by the GWDC parameterization occurs mainly in the Tropics by direct gravity wave drag forcing.

Original languageEnglish
Pages (from-to)3530-3547
Number of pages18
JournalJournal of Climate
Volume17
Issue number18
DOIs
Publication statusPublished - 2004 Sep 15

Fingerprint

gravity wave
drag
parameterization
stratosphere
zonal wind
cumulus
Northern Hemisphere
divergence
convective cloud
wave breaking
planetary wave
intertropical convergence zone
standing wave
westerly
Southern Hemisphere
troposphere
climate modeling
temperature
convection
saturation

All Science Journal Classification (ASJC) codes

  • Atmospheric Science

Cite this

Chun, Hye Yeong ; Song, In Sun ; Baik, Jong Jin ; Kim, Young Joon. / Impact of a convectively forced gravity wave drag parameterization in NCAR CCM3. In: Journal of Climate. 2004 ; Vol. 17, No. 18. pp. 3530-3547.
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abstract = "A parameterization of gravity wave drag forced by subgrid-scale cumulus convection (GWDC) proposed by Chun and Baik is implemented into the National Center for Atmospheric Research Community Climate Model (NCAR CCM3) and its effect on perpetual January and July climate is investigated. The cloud-top gravity wave stress is concentrated in the intertropical convergence zone where persistent deep cumulus clouds exist. The resultant zonal wind acceleration due to the breaking of convectively forced gravity waves is predominantly found in the tropical lower stratosphere with westerly acceleration above cloud top and easterly acceleration just below it. Since the parameterized gravity waves are stationary relative to convective clouds, wave breaking occurs mainly in the tropical lower stratosphere where the zonal wind is weak enough for wave saturation. It is shown that the GWDC parameterization significantly alleviates the systematic model biases of zonal-mean zonal wind and temperature. In particular, excessive easterlies in the tropical stratosphere and excessive cold temperatures in the tropical lower stratosphere are reduced by more than 50{\%} by including the GWDC parameterization. The horizontal wind divergence field in the tropical upper troposphere and lower stratosphere is also significantly improved with the GWDC parameterization. The impact of the GWDC parameterization extends to mid- to high latitudes through planetary wave activity in the winter hemisphere. The increased amplitude of zonal wavenumber 3 in the January Northern Hemisphere and the increased amplitude of zonal wavenumber 2 in the July Southern Hemisphere lead to significant improvements in model performance. The impact of the GWDC parameterization on Eliassen-Palm (EP) flux divergence forcing by stationary waves is generally opposite to that by transient waves in the extratropics, especially in the Northern Hemisphere wintertime. Hence, the zonal-mean zonal wind change by the GWDC parameterization occurs mainly in the Tropics by direct gravity wave drag forcing.",
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Impact of a convectively forced gravity wave drag parameterization in NCAR CCM3. / Chun, Hye Yeong; Song, In Sun; Baik, Jong Jin; Kim, Young Joon.

In: Journal of Climate, Vol. 17, No. 18, 15.09.2004, p. 3530-3547.

Research output: Contribution to journalArticle

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