BROWSE

Related Researcher

Author

Lee, Myong-In
Climate-Environment Modeling Lab
Research Interests
  • Climate Change, Seasonal Prediction, Extreme Weather, Aerosol

ITEM VIEW & DOWNLOAD

Simulation of the intraseasonal variability over the Eastern Pacific ITCZ in climate models

Cited 5 times inthomson ciCited 4 times inthomson ci
Title
Simulation of the intraseasonal variability over the Eastern Pacific ITCZ in climate models
Author
Jiang, XiananWaliser, Duane E.Kim, DaehyunZhao, MingSperber, Kenneth R.Stern, William F.Schubert, Siegfried D.Zhang, Guang J.Wang, WanqiuKhairoutdinov, MaratNeale, Richard B.Lee, Myong-In
Keywords
Eastern Pacific warm pool; Intraseasonal variability; ITCZ
Issue Date
201208
Publisher
SPRINGER
Citation
CLIMATE DYNAMICS, v.39, no.3-4, pp.617 - 636
Abstract
During boreal summer, convective activity over the eastern Pacific (EPAC) inter-tropical convergence zone (ITCZ) exhibits vigorous intraseasonal variability (ISV). Previous observational studies identified two dominant ISV modes over the EPAC, i.e., a 40-day mode and a quasi-biweekly mode (QBM). The 40-day ISV mode is generally considered a local expression of the Madden-Julian Oscillation. However, in addition to the eastward propagation, northward propagation of the 40-day mode is also evident. The QBM mode bears a smaller spatial scale than the 40-day mode, and is largely characterized by northward propagation. While the ISV over the EPAC exerts significant influences on regional climate/weather systems, investigation of contemporary model capabilities in representing these ISV modes over the EPAC is limited. In this study, the model fidelity in representing these two dominant ISV modes over the EPAC is assessed by analyzing six atmospheric and three coupled general circulation models (GCMs), including one super-parameterized GCM (SPCAM) and one recently developed high-resolution GCM (GFDL HIRAM) with horizontal resolution of about 50 km. While it remains challenging for GCMs to faithfully represent these two ISV modes including their amplitude, evolution patterns, and periodicities, encouraging simulations are also noted. In general, SPCAM and HIRAM exhibit relatively superior skill in representing the two ISV modes over the EPAC. While the advantage of SPCAM is achieved through explicit representation of the cumulus process by the embedded 2-D cloud resolving models, the improved representation in HIRAM could be ascribed to the employment of a strongly entraining plume cumulus scheme, which inhibits the deep convection, and thus effectively enhances the stratiform rainfall. The sensitivity tests based on HIRAM also suggest that fine horizontal resolution could also be conducive to realistically capture the ISV over the EPAC, particularly for the QBM mode. Further analysis illustrates that the observed 40-day ISV mode over the EPAC is closely linked to the eastward propagating ISV signals from the Indian Ocean/Western Pacific, which is in agreement with the general impression that the 40-day ISV mode over the EPAC could be a local expression of the global Madden-Julian Oscillation (MJO). In contrast, the convective signals associated with the 40-day mode over the EPAC in most of the GCM simulations tend to originate between 150A degrees E and 150A degrees W, suggesting the 40-day ISV mode over the EPAC might be sustained without the forcing by the eastward propagating MJO. Further investigation is warranted towards improved understanding of the origin of the ISV over the EPAC.
URI
Go to Link
DOI
http://dx.doi.org/10.1007/s00382-011-1098-x
ISSN
0930-7575
Appears in Collections:
UEE_Journal Papers

find_unist can give you direct access to the published full text of this article. (UNISTARs only)

Show full item record

qr_code

  • mendeley

    citeulike

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

MENU