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Leong Wai Siu and Kenneth P. Bowman

) demonstrated the importance of diabatic heating in simulating the NAMA using a mesoscale numerical model. Chao and Chen (2001) asserted that land–sea contrasts and orography are important for simulating the North American monsoon. Other thermal forcings may also be important. The heaviest North American monsoon precipitation is located along the Sierra Madre Occidental in northwestern Mexico; however, the heaviest precipitation in the western Hemisphere (WH) falls in the equatorial Pacific and Atlantic

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Simona Bordoni and Tapio Schneider

forcing undergo transitions from a linear, viscous regime to a nonlinear, angular-momentum-conserving regime beyond a threshold forcing value; they suggested that this threshold behavior may account for the rapid onset of monsoons. The nonlinear axisymmetric theory of Plumb and Hou (1992) has been extended in several studies to account for the influences of moist convection ( Emanuel 1995 ; Zheng 1998 ), of a subtropical continent ( Privé and Plumb 2007a , b ), and of moisture–dynamics feedbacks

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R. J. Haarsma and J. D. Opsteegh

Utrecht, Utrecht, The Netherlands (Manuscript received 12 October 1988, in final form I0 April 1989) We have investigated the nonlinear steady-state response of a barotropic model to an estimate of the observedanomalous tropical divergence forcing for the El Nifio winter of 1982/83, The 400 mb climatological fl0w wasmade a forced solution of the model by adding a relaxation forcing. The Rayleigh friction coefficient (~-~ -- 20days) was chosen such that this solution is marginally stable. The

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Edwin K. Schneider, Lennart Bengtsson, and Zeng-Zhen Hu

between the simulated and observed low-pass evolution of the wintertime NAO index, including a positive trend, at least for the mid-1960s through the mid-1990s. Rodwell et al. (1999) relate this resemblance to forcing by North Atlantic SST anomalies (SSTAs) and find no evidence for tropical forcing. Hoerling et al. (2001) find the forcing from the extratropics and the tropical Atlantic to be small and therefore attribute the resemblance in the low-frequency behavior and trend of an index closely

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Andrew J. Majda, Boris Gershgorin, and Yuan Yuan

1. Introduction The low-frequency response to changes in external forcing or other parameters for various components of the climate system is a central problem of contemporary climate change science. Examples include the response of the mean and variance of the low-frequency teleconnection patterns of the atmosphere in addition to more familiar functions such as the mean temperature response in a global warming scenario. Leith (1975) suggested that if the climate system satisfied a suitable

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J. C. Alpert and S. K. Avery

OCTOBER 19~3 J.C. ALPERT, M. A. GELLER AND S. K. AVERY 2467'The Response of Stationary Planetary Waves to Tropospheric Forcing~ J. C. ALPERT AND M. A. GELLERLaboratory for Planetary Atmospheres, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 S. K. AVERY2Department of Electrical Engineering, University of Illinois, Urbana 61801(Manuscript received 2 February 1983, in final

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Mauro Dall’Amico and Joseph Egger

noise forcing as a data basis ( section 3 ). Systematic variations of grid size, time series length, sampling interval, and the number of variables are conducted in section 4 in order to study their effect on how well the EME reproduces the dynamics of the studied system. The conclusions are outlined in section 5 . The results of this part of the paper provide guidelines for the application of this methodology to any problem in (and beyond) the atmospheric sciences. Real data of limited length

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Steven L. Mullen

VOL. 44, NO. 1 JOURNAL OF THE ATMOSPHERIC SCIENCES I JANUARY 1987 Transient Eddy Forcing of Blocking Flows STEVEN L. MULLEN* National Center for Atmospheric Research,** Boulder, CO 80307 (Manuscript received 2 January 1986, in final form 1 July 1986) ABSTRACT The net forcing of blocking flows by transient eddies having synoptic time scales is examined within

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Brian F. Farrell and Petros J. Ioannou

1. Introduction A comprehensive understanding of the dynamics of linear systems is fundamental to physical science and, while linear systems arise in a wide variety of contexts, in this work we have in mind the particular examples of the dynamics of perturbations to the tangent linear forecast and data assimilation error systems. Among important problems in dynamical system theory is understanding the response of a linear system to forcing distributed in time. In the context of linear forecast

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Hye-Yeong Chun, In-Sun Song, and Takeshi Horinouchi

generated by cumulus clouds have high frequencies and they contribute significantly to the momentum forcing required for driving the quasi-biennial oscillation and semiannual oscillation ( Dunkerton 1997 ; Hamilton 1998 ). Compared with mountain-induced gravity waves, it is not straightforward to understand how convective sources generate gravity waves. In the literature, three generation mechanisms (thermal forcing, obstacle, and mechanical oscillator mechanisms) have been proposed ( Lane et al. 2001

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