Dispersion characteristics and circulation associated with boreal summer westward travelling mixed-Rossby gravity wave-like disturbances

Dispersion characteristics and circulation associated with boreal summer westward travelling... AbstractAn algorithm has been developed to track synoptic-scale, westward travelling mixed-Rossby gravity (MRG) wave-like disturbances with a cross equatorial component. Applied to space-time filtered, meridional wind data, this algorithm finds locations with Gaussian-shaped wind structure stated in the solutions of shallow water equations (SWE). Based on 850hPa meridional wind from the global National Centers for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR) dataset, local and instantaneous wave properties including the occurrence time, wavenumber, intrinsic frequency and magnitude were examined. It was found that these low-level MRG-wave like disturbances can be classified into a longer wavelength group and a shorter wavelength group. While most waves identified in the eastern Pacific give longer wavelengths, disturbances in the western Pacific tend to have a wider range of wavenumbers. Composite analysis revealed that, east of ~140°E, low-level disturbances are characterized by cross-equatorial wind anomalies with alternating signs, thus consistent with the MRG wave solution. West of ~140°E, they appear as northeast-to-southwest tilted eddies that propagate northwestward. Examination of their energetics suggests that such a tilting structure is favorable to the maintenance of these transients, due to the meridional shear of background zonal wind west of ~140°E in off-equatorial Pacific. Farther east, the confluent nature of the low-level background flow plays a dominant role in maintaining the MRG-wave like disturbances due to barotropic conversion. Finally, there is evidence of downward energy dispersion in the mid to upper levels suggesting that that upper-level wave activity might be important in triggering these low-level waves in the Pacific basin. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of the Atmospheric Sciences American Meteorological Society

Dispersion characteristics and circulation associated with boreal summer westward travelling mixed-Rossby gravity wave-like disturbances

Loading next page...
 
/lp/ams/dispersion-characteristics-and-circulation-associated-with-boreal-V7RkdX9Pkg
Publisher
American Meteorological Society
Copyright
Copyright © American Meteorological Society
ISSN
1520-0469
D.O.I.
10.1175/JAS-D-16-0245.1
Publisher site
See Article on Publisher Site

Abstract

AbstractAn algorithm has been developed to track synoptic-scale, westward travelling mixed-Rossby gravity (MRG) wave-like disturbances with a cross equatorial component. Applied to space-time filtered, meridional wind data, this algorithm finds locations with Gaussian-shaped wind structure stated in the solutions of shallow water equations (SWE). Based on 850hPa meridional wind from the global National Centers for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR) dataset, local and instantaneous wave properties including the occurrence time, wavenumber, intrinsic frequency and magnitude were examined. It was found that these low-level MRG-wave like disturbances can be classified into a longer wavelength group and a shorter wavelength group. While most waves identified in the eastern Pacific give longer wavelengths, disturbances in the western Pacific tend to have a wider range of wavenumbers. Composite analysis revealed that, east of ~140°E, low-level disturbances are characterized by cross-equatorial wind anomalies with alternating signs, thus consistent with the MRG wave solution. West of ~140°E, they appear as northeast-to-southwest tilted eddies that propagate northwestward. Examination of their energetics suggests that such a tilting structure is favorable to the maintenance of these transients, due to the meridional shear of background zonal wind west of ~140°E in off-equatorial Pacific. Farther east, the confluent nature of the low-level background flow plays a dominant role in maintaining the MRG-wave like disturbances due to barotropic conversion. Finally, there is evidence of downward energy dispersion in the mid to upper levels suggesting that that upper-level wave activity might be important in triggering these low-level waves in the Pacific basin.

Journal

Journal of the Atmospheric SciencesAmerican Meteorological Society

Published: Dec 4, 2017

References

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 12 million articles from more than
10,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Unlimited reading

Read as many articles as you need. Full articles with original layout, charts and figures. Read online, from anywhere.

Stay up to date

Keep up with your field with Personalized Recommendations and Follow Journals to get automatic updates.

Organize your research

It’s easy to organize your research with our built-in tools.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

Monthly Plan

  • Read unlimited articles
  • Personalized recommendations
  • No expiration
  • Print 20 pages per month
  • 20% off on PDF purchases
  • Organize your research
  • Get updates on your journals and topic searches

$49/month

Start Free Trial

14-day Free Trial

Best Deal — 39% off

Annual Plan

  • All the features of the Professional Plan, but for 39% off!
  • Billed annually
  • No expiration
  • For the normal price of 10 articles elsewhere, you get one full year of unlimited access to articles.

$588

$360/year

billed annually
Start Free Trial

14-day Free Trial