Role of the Tibetan Plateau on the Annual Variation of Mean Atmospheric Circulation and Storm-Track Activity*

2013 ◽  
Vol 26 (14) ◽  
pp. 5270-5286 ◽  
Author(s):  
Sun-Seon Lee ◽  
June-Yi Lee ◽  
Kyung-Ja Ha ◽  
Bin Wang ◽  
Akio Kitoh ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Atmospheric Circulation ◽  
North Pacific ◽  
Annual Variation ◽  
Storm Track ◽  
Monsoon Circulation ◽  
The Tibetan Plateau ◽  
The Pacific ◽  
Storm Track Activity ◽  
Midwinter Suppression

Abstract This study reexamines how the Tibetan Plateau (TP) modulates the annual variation of atmospheric circulation and storm-track activity based on the Meteorological Research Institute's atmosphere–ocean coupled model experiments with a progressive TP uplift from 0% to 100% of the present height. Three major roles of the TP on atmospheric circulation and storm-track activity are identified. First, consistent with a previous finding, the TP tends to intensify the upper-level jet and enhance baroclinicity in the North Pacific Ocean but significantly weaken storm-track activity over the TP, East Asia, and the western North Pacific during the cold season. Second, the TP amplifies stationary waves that are closely linked to transient eddies. In particular, the TP enhances the Siberian high and the Aleutian low, which together contribute to the strengthening of the East Asian winter monsoon circulation and the weakening of storm-track activity. Third, the TP significantly modulates the subseasonal variability of the Pacific storm-track (PST) activity. In particular, the TP tends to suppress PST activity during midwinter despite the fact that it strengthens baroclinicity along the Pacific jet. The midwinter suppression of PST activity, which is well reproduced in a control run with a realistic TP, gradually disappears as the TP height decreases. Major factors for the midwinter suppression of the PST associated with the TP include the 1) destructive effect of an excessively strong jet leading to an inefficiency of barotropic energy conversion, 2) reduction of baroclinicity over the northern part of the TP, and 3) subseasonally varying SST change and resulting moist static energy.

scholarly journals Comments on “The Source of the Midwinter Suppression in Storminess over the North Pacific”

2011 ◽  
Vol 24 (19) ◽  
pp. 5187-5191 ◽  
Author(s):  
Edmund K. M. Chang ◽  
Yanjuan Guo
Keyword(s):  
North Pacific ◽  
Feature Tracking ◽  
Storm Track ◽  
Northern Asia ◽  
The North ◽  
Relative Minimum ◽  
The Pacific ◽  
Storm Track Activity ◽  
The North Pacific ◽  
Midwinter Suppression

In a recent paper, Penny et al. employed feature tracking to investigate why there is a relative minimum in storminess during winter within the Pacific storm track. They concluded that reduced upstream seeding, especially seeding from northern Asia, is the main “source” of the midwinter suppression of the Pacific storm track. Results presented here show that during midwinter months when upstream seeding is as strong as that in spring/fall, the Pacific storm track is not significantly stronger than average and is still much weaker than that in spring/fall, suggesting that the strength of upstream seeding cannot be the primary cause of the midwinter suppression of Pacific storm-track activity.

The Source of the Midwinter Suppression in Storminess over the North Pacific

2010 ◽  
Vol 23 (3) ◽  
pp. 634-648 ◽  
Author(s):  
Sandra Penny ◽  
Gerard H. Roe ◽  
David S. Battisti
Keyword(s):  
Growth Rates ◽  
Feature Tracking ◽  
Storm Track ◽  
Static Stability ◽  
The Tibetan Plateau ◽  
The North ◽  
The Pacific ◽  
Upper Level ◽  
The North Pacific ◽  
Midwinter Suppression

Abstract Feature-tracking techniques are employed to investigate why there is a relative minimum in storminess during winter within the Pacific storm track (the midwinter suppression). It is found that the frequency and amplitude of disturbances entering the Pacific storm track from midlatitude Asia are substantially reduced during winter relative to fall and spring and that the magnitude of this reduction is more than sufficient to account for the midwinter supression. Growth rates of individual disturbances are calculated and compared to expectations from linear theory for several regions of interest. Although there are discrepancies between linear expectations and observed growth rates over the Pacific, the growth of disturbances within the Pacific storm track cannot explain why the midwinter suppression exists. Furthermore, it is determined that the development of a wintertime reduction in storminess over midlatitude Asia is consistent with linear expectations, which predict a wintertime minimum in Eady growth rates in this region, mainly because of increased static stability. Several other mechanisms that may contribute to the initiation of the midwinter suppression over midlatitude Asia are discussed, including the interaction between upper-level waves and topography, the behavior of waves upwind of the Tibetan Plateau, and the initiation of lee cyclones.

Baroclinic Development in Observations and NASA GSFC General Circulation Models

2006 ◽  
Vol 134 (4) ◽  
pp. 1161-1173 ◽  
Author(s):  
Dennis P. Robinson ◽  
Robert X. Black
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
General Circulation ◽  
Storm Track ◽  
Model Simulations ◽  
The North ◽  
The Pacific ◽  
The North Atlantic ◽  
The North Pacific ◽  
Midwinter Suppression

Abstract Comparative diagnostic analyses of developing synoptic-scale baroclinic disturbances in NCEP–NCAR reanalyses and the NASA–NCAR (NASCAR) and Aries [NASA’s Seasonal-to-Interannual Prediction Project (NSIPP)] general circulation model simulations are performed. In particular, lag composite analyses of wintertime cyclonic and anticyclonic events occurring in the North Pacific and North Atlantic storm tracks are constructed to pursue a synoptic and dynamic characterization of eddy development. The data are also seasonally stratified to study aspects of the North Pacific midwinter suppression phenomenon. Winter-averaged results indicate that the model-simulated events are generally too weak in amplitude, particularly in the upper troposphere. For the North Pacific storm track, model-simulated events are also anomalously distended in the meridional direction. The existing model biases in eddy structure and magnitude lead to anomalously weak baroclinic energy conversions for both cyclonic and anticyclonic events over the North Pacific. For the North Atlantic storm track the NASCAR model provides a very good representation of the structure of developing cyclonic events. However, growing North Atlantic cyclones in the NSIPP model are anomalously weak and horizontally too isotropic (meridionally retracted). These latter two characteristics are also observed in both models for developing anticyclonic flow anomalies over the North Atlantic. The relative weakness of NSIPP synoptic events over the North Atlantic region is largely responsible for the 50% deficiency in areal-averaged baroclinic energy conversions. Conversely, the NASCAR model climatology features anomalously strong temperature gradients over the western North Atlantic that provide local enhancements to the baroclinic energy conversion field. A seasonally stratified diagnostic analysis reveals that the simulated climatological storm tracks over the North Pacific undergo larger spatial migrations during the cool season compared to observations. It is further determined that the suppression of synoptic eddy activity observed in the Pacific storm track is associated with a relative midwinter weakness in the magnitude of the growing cyclonic anomalies. Specifically, during midwinter the cyclonic perturbations entering the Pacific storm track are deficient in magnitude compared to their early and late winter counterparts. It is also discovered that the midwinter suppression pattern over the North Pacific region has a clear organized extension upstream into Siberia, the region from which incipient upper-tropospheric short-wave features emanate. This behavior is found in both observations and the model simulations. The results herein support the idea that the North Pacific midwinter suppression phenomenon is linked to a midwinter weakness in the upstream formation of upper-level short waves, leading to anomalously weak “seeding” of baroclinic disturbances in the Pacific storm track.

scholarly journals Is Pacific Storm-Track Activity Correlated with the Strength of Upstream Wave Seeding?

2012 ◽  
Vol 25 (17) ◽  
pp. 5768-5776 ◽  
Author(s):  
Edmund K. M. Chang ◽  
Yanjuan Guo
Keyword(s):  
Feature Tracking ◽  
Storm Track ◽  
Central Pacific ◽  
The North ◽  
The Pacific ◽  
North Asia ◽  
Storm Track Activity ◽  
The Relationship ◽  
The North Pacific ◽  
Midwinter Suppression

Abstract In this paper, the relationship between upstream seeding over north Asia and downstream storm-track activity over the North Pacific in midwinter and spring/fall has been analyzed using 45 years of variance and feature-tracking statistics. It is shown that for each season, interannual variations in upstream seeding and downstream storm-track activity are largely uncorrelated. Moreover, during midwinter months in which the upstream seeding from north Asia is about as strong as that during a typical spring/fall month, the downstream storm track in central Pacific is still significantly weaker during midwinter than that during spring/fall. In addition, during cool seasons in which the midwinter suppression is more pronounced in the upstream seeding region, the suppression is not significantly enhanced in the downstream Pacific storm track. A recent study suggested that reduced upstream seeding from north Asia is the main “source” of the midwinter suppression of the Pacific storm track. Results presented in this study suggest that it is unlikely that the weakness in upstream seeding is the primary cause of the midwinter suppression.

Mongolian Mountains Matter Most: Impacts of the Latitude and Height of Asian Orography on Pacific Wintertime Atmospheric Circulation

2017 ◽  
Vol 30 (11) ◽  
pp. 4065-4082 ◽  
Author(s):  
R. H. White ◽  
D. S. Battisti ◽  
G. H. Roe
Keyword(s):  
Tibetan Plateau ◽  
Atmospheric Circulation ◽  
General Circulation ◽  
Circulation Model ◽  
General Circulation Models ◽  
The Tibetan Plateau ◽  
Contributing Factors ◽  
The Pacific ◽  
Upper Level ◽  
Hemisphere Winter

Abstract The impacts of Asian orography on the wintertime atmospheric circulation over the Pacific are explored using altered-orography, semi-idealized, general circulation model experiments. The latitude of orography is found to be far more important than height. The Mongolian Plateau and nearby mountain ranges, centered at ~48°N, have an impact on the upper-level wintertime jet stream that is approximately 4 times greater than that of the larger and taller Tibetan Plateau and Himalayas to the south. Key contributing factors to the importance of the Mongolian mountains are latitudinal variations in the meridional potential vorticity gradient and the strength of the impinging wind—both of which determine the amplitude of the atmospheric response—and the structure of the atmosphere, which influences the spatial pattern of the downstream response. Interestingly, while the Mongolian mountains produce a larger response than the Tibetan Plateau in Northern Hemisphere winter, in April–June the response from the Tibetan Plateau predominates. This result holds in two different general circulation models. In experiments with idealized orography, varying the plateau latitude by 20°, from 43° to 63°N, changes the response amplitude by a factor of 2, with a maximum response for orography between 48° and 53°N, comparable to the Mongolian mountains. In these idealized experiments, the latitude of the maximum wintertime jet increase changes by only ~6°. It is proposed that this nearly invariant spatial response pattern is due to variations in the stationary wavenumber with latitude leading to differences in the zonal versus meridional wave propagation.

scholarly journals Impacts of Two East Asian Atmospheric Circulation Modes on Black Carbon Aerosol Over the Tibetan Plateau in Winter

2020 ◽  
Vol 125 (12) ◽  
Author(s):  
Tiangang Yuan ◽  
Siyu Chen ◽  
Lin Wang ◽  
Yaoxian Yang ◽  
Hongru Bi ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Black Carbon ◽  
Atmospheric Circulation ◽  
East Asian ◽  
The Tibetan Plateau ◽  
Black Carbon Aerosol
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