scholarly journals Midwinter Suppression of the Pacific Storm Track Activity as Seen in Aircraft Observations

2003 ◽  
Vol 60 (11) ◽  
pp. 1345-1358 ◽  
Author(s):  
Edmund K. M. Chang
Keyword(s):  
Storm Track ◽  
The Pacific ◽  
Aircraft Observations ◽  
Storm Track Activity ◽  
Midwinter Suppression

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.

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.

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.

scholarly journals Dynamics of Synoptic Eddy and Low-Frequency Flow Interaction. Part II: A Theory for Low-Frequency Modes

2006 ◽  
Vol 63 (7) ◽  
pp. 1695-1708 ◽  
Author(s):  
F-F. Jin ◽  
L-L. Pan ◽  
M. Watanabe
Keyword(s):  
Storm Track ◽  
Low Frequency ◽  
Prototype Model ◽  
Mean Flow ◽  
Zonal Scale ◽  
Synoptic Eddy ◽  
The Pacific ◽  
Storm Track Activity ◽  
Recurrent Patterns ◽  
The Antarctic

Abstract Amidst stormy atmospheric circulation, there are prominent recurrent patterns of variability in the planetary circulation, such as the Antarctic Oscillation (AAO), Arctic Oscillation (AO) or North Atlantic Oscillation (NAO), and the Pacific–North America (PNA) pattern. The role of the synoptic eddy and low-frequency flow (SELF) feedback in the formation of these dominant low-frequency modes is investigated in this paper using the linear barotropic model with the SELF feedback proposed in Part I. It is found that the AO-like and AAO-like leading singular modes of the linear dynamical system emerge from the stormy background flow as the result of a positive SELF feedback. This SELF feedback also prefers a PNA-like singular vector as well among other modes under the climatological conditions of northern winters. A model with idealized conditions of basic mean flow and activity of synoptic eddy flow and a prototype model are also used to illustrate that there is a natural scale selection for the AAO- and AO-like modes through the positive SELF feedback. The zonal scale of the localized features in the Atlantic (southern Indian Ocean) for AO (AAO) is largely related to the zonal extent of the enhanced storm track activity in the region. The meridional dipole structures of AO- and AAO-like low-frequency modes are favored because of the scale-selective positive SELF feedback, which can be heuristically understood by the tilted-trough mechanism.

scholarly journals Reply

2011 ◽  
Vol 24 (19) ◽  
pp. 5192-5194 ◽  
Author(s):  
S. M. Penny ◽  
G. H. Roe ◽  
D. S. Battisti
Keyword(s):  
Pacific Ocean ◽  
Interannual Variability ◽  
Storm Track ◽  
Central Pacific ◽  
Central Pacific Ocean ◽  
Recent Comment ◽  
Full Dataset ◽  
The Pacific ◽  
Midwinter Suppression

Penny et al. recently showed that the midwinter suppression in storminess over the western and central Pacific Ocean is due to a reduction in the number and amplitude of “seed” disturbances entering the Pacific storm track from midlatitude Asia. In this reply, the authors strengthen the conclusions that were originally put forth and show that the apparent departure from this behavior presented in a recent comment originates in the commenters having undersampled the full dataset of interannual variability. It is shown that when the Pacific storm track is only weakly “seeded” by an upstream source, as is common during winter and uncommon during fall and spring, it is likely to be weaker than average, and this reduction is highly statistically significant and the amplitude compares well with the midwinter suppression.

scholarly journals Are the Northern Hemisphere Winter Storm Tracks Significantly Correlated?

2004 ◽  
Vol 17 (21) ◽  
pp. 4230-4244 ◽  
Author(s):  
Edmund K. M. Chang
Keyword(s):  
Northern Hemisphere ◽  
Storm Track ◽  
Reanalysis Data ◽  
Storm Tracks ◽  
The Pacific ◽  
Aircraft Observations ◽  
Highly Correlated ◽  
Hemisphere Winter ◽  
Aircraft Data ◽  
Northern Hemisphere Winter

Abstract In this study, the correlation between the Northern Hemisphere winter Pacific and Atlantic storm tracks is examined using the NCEP–NCAR reanalysis and the 40-yr ECMWF Re-Analysis (ERA-40), as well as unassimilated aircraft observations. By examining month-to-month variability in the 250-hPa meridional velocity variance, the correlation between the two storm track peaks is found to be as high as 0.5 during the winters between 1975/76 and 1998/99. Here, it is shown that the correlation between the two storm tracks can be clearly detected from the aircraft data. Further analyses of the reanalysis data show that the correlation can also be seen in other eddy variance and covariance statistics, including the poleward heat flux at the 700-hPa level. The correlation between the two storm tracks, as seen in both reanalysis datasets, is shown to be much weaker during the period 1957/58–1971/72, suggesting a possible regime transition from largely uncorrelated storm tracks to highly correlated storm tracks during the 1970s. However, during this earlier period, the number of aircraft observations is insufficient to verify the low correlation seen in the reanalyses. Thus, low biases in the reanalyses during the earlier period cannot be ruled out. An ensemble of four GCM simulations performed using the GFDL GCM forced by global observed SST variations between 1950 and 1995 has also been examined. The correlation between the two storm tracks in the GCM simulations is much lower (0.18) than that observed, even if the analysis is restricted to the GCM simulations from the period 1975/76–1994/95. A Monte Carlo test shows that the observed correlation and the GCM correlation are statistically distinct at the 1% level. Correlations between the Southern Hemisphere summer Pacific and Atlantic storm tracks have also been examined based on the reanalyses datasets. The results suggest that the amplitude of the SH summer Pacific and Atlantic storm tracks are not significantly correlated, showing that seeding of the Atlantic storm track by the Pacific storm track does not necessarily lead to significant correlations between the two storm tracks.

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.

Sign in / Sign up

Export Citation Format

Share Document