Summer Rainfall Seesaw between Hetao and the Middle and Lower Reaches of the Yangtze River and Its Relationship with the North Atlantic Oscillation

2017 ◽  
Vol 30 (17) ◽  
pp. 6629-6643 ◽  
Author(s):  
Dachao Jin ◽  
Zhaoyong Guan
Keyword(s):  
Rossby Wave ◽  
North Atlantic ◽  
Yangtze River ◽  
Lower Troposphere ◽  
Summer Rainfall ◽  
Northern China ◽  
Upper Troposphere ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Using the NCEP–NCAR reanalysis and other observational datasets, the authors have investigated the relationship of summer rainfall variations between the Hetao region of northern China and the middle and lower reaches of Yangtze River (MLRYR). The results have demonstrated that rainfall in Hetao varies out of phase with that in MLRYR on the interannual time scales. This phenomenon is referred to as the Hetao–Yangtze rainfall seesaw (HYRS). An HYRS index is defined to reveal both spatial and temporal features of HYRS. It is found that the North Atlantic Oscillation (NAO) affects the HYRS. In years when the NAO is in its positive phase, anomalous divergences in the lower troposphere and anomalous convergences in the upper troposphere are observed in regions of the Mediterranean and eastern Europe. The anomalous convergences in the upper troposphere occur as the positive Rossby wave source excites a circumglobal teleconnection (CGT) in the midlatitudes, exhibiting the eastward propagation of Rossby wave energy along the Asian jet. Meanwhile, the Eurasian–Pacific (EUP) teleconnection also affects the HYRS. Influenced mainly by the CGT pattern, the circulations over Hetao and MLRYR are consequently perturbed. The atmosphere over Hetao converges anomalously in the lower troposphere and diverges anomalously in the upper troposphere, facilitating more than normal rainfall there. At the same time, the atmosphere over MLRYR diverges anomalously in the lower troposphere and converges anomalously in the upper troposphere, resulting in more than normal summer rainfall in MLRYR. In this way, the north–south rainfall seesaw is formed. This NAO-induced rainfall seesaw is potentially useful for summer rainfall predictions in both MLRYR and the Hetao region of northern China.

The Extreme Drought Event during Winter–Spring of 2011 in East China: Combined Influences of Teleconnection in Midhigh Latitudes and Thermal Forcing in Maritime Continent Region

2013 ◽  
Vol 26 (20) ◽  
pp. 8210-8222 ◽  
Author(s):  
Dachao Jin ◽  
Zhaoyong Guan ◽  
Weiya Tang
Keyword(s):  
North Atlantic ◽  
Yangtze River ◽  
Lower Troposphere ◽  
The Philippines ◽  
Drought Event ◽  
The Yangtze River ◽  
Maritime Continent ◽  
Thermal Forcing ◽  
The North ◽  
The North Atlantic

Abstract The middle and lower reaches of the Yangtze River (MLRYR) in China experienced an extremely severe and persistent drought event from January to May of 2011. Using both the observational data and NCEP–NCAR reanalysis, features of the drought event and the related circulation anomalies were investigated. It is found that the precipitation during the investigated period of 2011 was deficient mostly along the Yangtze River. The water vapor diverged from MLRYR southward into the Bay of Bengal, South China Sea, and the Philippines. There were two factors facilitating the drought event. One was the quasi-stationary Rossby wave–related teleconnection, which propagated eastward at midhigh latitudes from the North Atlantic to East Asia, reinforcing the Siberian high and the East Asian trough, henceforth resulting in the divergence anomalies in MLRYR in the lower troposphere. This quasi-stationary wave train, though originating from the North Atlantic region, was not essentially related to the North Atlantic Oscillation. Another factor for the drought event was the persistent anomalous thermal forcing over the Maritime Continent, which induced the anomalous divergence in the upper troposphere in this region, building up an anomalous Hadley circulation with its ascent branch over the Maritime Continent and descent branch over MLRYR. This thermal forcing was possibly, but not necessarily, related to the La Niña event. The persistence of the drought event over MLRYR was due to the maintenance of the quasi-stationary waves at midhigh latitudes and the persistent anomalous thermal forcing in the Maritime Continent.

scholarly journals Stochastic Forcing of Ocean Variability by the North Atlantic Oscillation

2009 ◽  
Vol 39 (1) ◽  
pp. 162-184 ◽  
Author(s):  
Kettyah C. Chhak ◽  
Andrew M. Moore ◽  
Ralph F. Milliff
Keyword(s):  
North Atlantic Oscillation ◽  
Ocean Circulation ◽  
Rossby Wave ◽  
North Atlantic ◽  
Large Scale ◽  
Western Boundary ◽  
Stochastic Forcing ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract At middle and high latitudes, the magnitude of stochastic wind stress forcing of the ocean by atmospheric variability on synoptic time scales (i.e., “weather” related variability) is comparable to that of the seasonal cycle. Stochastic forcing may therefore have a significant influence on the ocean circulation, climate, and ocean predictability. Here, the influence of stochastic forcing associated with the North Atlantic Oscillation on the subtropical gyre circulation of the North Atlantic is explored in an eddy-permitting quasigeostrophic framework. For the North Atlantic winds used in this study, the root-mean-square of the annual average Ekman pumping velocity of the seasonal cycle between 35° and 52°N is 1.3 × 10−7 m s−1, while the wintertime standard deviation of the stochastic component of the North Atlantic Oscillation over the same latitude band is 2.2 × 10−7 m s−1. Significant stochastically induced variability in the ocean circulation occurs near the western boundary region and along the western margins of the abyssal plains associated with vortex stretching, energy release from the mean flow, and the generation of topographic Rossby waves. Variability arises from a combination of two effects, depending on the measure of variance used: growth of unstable modes of the underlying circulation and modal interference resulting from their nonnormal nature, which dominates during the first 10 days or so of perturbation growth. Near the surface, most of the variability is associated with large-scale changes in the barotropic circulation, although more than 20% of the energy and enstrophy variability is associated with small-scale baroclinic waves. In the deep ocean, much of the stochastically induced variability is apparently due to topographic Rossby wave activity along the continental rise and ocean ridges. Previous studies have demonstrated that rectification of topographic Rossby wave–induced circulations in the western North Atlantic may contribute to the western boundary current recirculation zones. The authors suggest that a source of topographic Rossby wave energy, significant enough to rectify the mean ocean circulation, may arise from stochastic forcing by large-scale atmospheric forcing, such as the North Atlantic Oscillation and other atmospheric teleconnection patterns.

Spring Dust over the Tibetan Plateau and Connections with North Atlantic SST Variability

2021 ◽  
Author(s):  
Chao Xu ◽  
Yaoming Ma ◽  
Jiehua Ma ◽  
Chao You ◽  
Huijun Wang
Keyword(s):  
North Atlantic ◽  
Tarim Basin ◽  
Wave Train ◽  
Lower Troposphere ◽  
Lower Atmosphere ◽  
The Tibetan Plateau ◽  
Upper Troposphere ◽  
The North ◽  
The North Atlantic ◽  
Spring Dust

<p>Dust is a major component of atmospheric aerosol worldwide, greatly affecting regional and global climate. A dust belt can be clearly found at altitudes higher than 6 km over the downwind direction of the TP at latitudes of around 30°–40°N, crossing the Pacific Ocean and extending to North America during spring. Dust is uplifted to the midtroposphere over the source regions; then, frequent, deep, dry convection prevailing over the TP during spring can cause convective overshooting that uplifts the dust aerosols to the upper troposphere. The TP thus acts as a channel for transporting dust from the lower atmosphere to the upper troposphere, enabling the long-range zonal transport of dust around the Northern Hemisphere. Estimated spring dust mass flux (DMF) showed a significant declining trend over the TP during 2007-2019. The total spring DMF across the TP was mainly affected by DMFs over the Tarim Basin, while the spring DMF across the TP in the mid-troposphere was also connected with DMFs over the northwest Indian Peninsula and Central Asia. Inter-annual variability of spring DMF across the TP was strongly correlated with the North Atlantic winter sea surface temperature (SST) tripole. The North Atlantic winter SST tripole anomalies persist into the subsequent spring, and induce a corresponding atmosphere response. A strong positive North Atlantic winter SST tripole anomaly strengthens the upper-level westerly jets, enhancing air flow towards the TP mid-troposphere; together, these circulation patterns cause anomalous cyclonic conditions in the lower troposphere, especially over the Tarim Basin, via the eastwards propagation of a Rossby wave train. These atmospheric circulation conditions are likely to increase the frequency of dust occurrence and promote the transport of dust onto the TP.</p>

North Atlantic Summertime Anticyclonic Rossby Wave Breaking: Climatology, Impacts, and Connections to the Pacific Decadal Oscillation

2018 ◽  
Vol 32 (2) ◽  
pp. 485-500 ◽  
Author(s):  
Breanna L. Zavadoff ◽  
Ben P. Kirtman
Keyword(s):  
Rossby Wave ◽  
North Atlantic ◽  
Pacific Decadal Oscillation ◽  
Wave Breaking ◽  
Reanalysis Data ◽  
Tropical Cyclogenesis ◽  
Rossby Wave Breaking ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract Anticyclonic Rossby wave breaking (RWB) is characterized by the rapid and irreversible deformation of potential vorticity (PV) contours on isentropic surfaces manifesting as a pair of meridionally elongated high- and low-PV tongues that transport extratropical stratospheric air equatorward and tropical tropospheric air poleward, respectively. Previous studies have noted connections between different types of RWB and the modulation of localized atmospheric phenomena such as the North Atlantic Oscillation (NAO) and tropical cyclogenesis. Despite being the season in which anticyclonic RWB events are most prevalent, no work has focused solely on the frequency, genesis, or variability of the synoptic environment surrounding the equatorward branch of anticyclonic RWB events during the North Atlantic summertime, providing motivation for this study. Using 58 years (1960–2017) of NCEP–NCAR reanalysis data, a comprehensive spatiotemporal climatology of North Atlantic equatorward anticyclonic RWB identified on the 350-K isentropic surface is developed and the synoptic environment surrounding these events from time- and high-PV-tongue centroid-relative perspectives is investigated. Consistent with previous studies, composites suggest that high-PV tongues associated with equatorward anticyclonic RWB introduce anomalously dry, stable extratropical air into the tropical environment, subsequently inhibiting convection there. Additionally, a connection between atmospheric responses to Pacific decadal oscillation (PDO) sea surface temperature (SST) anomalies and the intrabasin frequency of anticyclonic RWB events is uncovered and explored. Results from this study may aid short- to medium-range forecasts of North Atlantic tropical convection, with applications extending into the field of tropical cyclogenesis forecasting.

scholarly journals Links between Rossby Wave Breaking and the North Atlantic Oscillation–Arctic Oscillation in Present-Day and Last Glacial Maximum Climate Simulations

2010 ◽  
Vol 23 (11) ◽  
pp. 2987-3008 ◽  
Author(s):  
Gwendal Rivière ◽  
Alexandre Laîné ◽  
Guillaume Lapeyre ◽  
David Salas-Mélia ◽  
Masa Kageyama
Keyword(s):  
North Atlantic Oscillation ◽  
Last Glacial Maximum ◽  
Rossby Wave ◽  
North Atlantic ◽  
Wave Breaking ◽  
Arctic Oscillation ◽  
Rossby Wave Breaking ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract Upper-tropospheric Rossby wave–breaking processes are examined in coupled ocean–atmosphere simulations of the Last Glacial Maximum (LGM) and of the modern era. LGM statistics of the Northern Hemisphere in winter, computed from the Paleoclimate Modeling Intercomparison Project Phase II (PMIP2) dataset, are compared with those from preindustrial simulations and from the 40-yr ECMWF Re-Analysis (ERA-40). Particular attention is given to the role of wave-breaking events in the North Atlantic Oscillation (NAO) for each simulation. Anticyclonic (AWB) and cyclonic (CWB) wave-breaking events during LGM are shown to be less and more frequent, respectively, than in the preindustrial climate, especially in the Pacific. This is consistent with the slight equatorward shift of the eddy-driven jets in the LGM runs. The most remarkable feature of the simulated LGM climate is that it presents much weaker latitudinal fluctuations of the eddy-driven jets. This is accompanied by less dispersion in the wave-breaking events. A physical interpretation is provided in terms of the fluctuations of the low-level baroclinicity at the entrance of the storm tracks. The NAO in the preindustrial simulations and in ERA-40 is characterized by strong latitudinal fluctuations of the Atlantic eddy-driven jet as well as by significant changes in the nature of the wave breaking. During the positive phase, the eddy-driven jet moves to the north with more AWB events than usual and is well separated from the subtropical African jet. The negative phase exhibits a more equatorward Atlantic jet and more CWB events. In contrast, the LGM NAO is less well marked by the latitudinal vacillation of the Atlantic jet and for some models this property disappears entirely. The LGM NAO corresponds more to acceleration–deceleration or extension–retraction of the Atlantic jet. The hemispheric point of view of the Arctic Oscillation exhibits similar changes.

scholarly journals A New Rossby Wave–Breaking Interpretation of the North Atlantic Oscillation

2008 ◽  
Vol 65 (2) ◽  
pp. 609-626 ◽  
Author(s):  
Tim Woollings ◽  
Brian Hoskins ◽  
Mike Blackburn ◽  
Paul Berrisford
Keyword(s):  
North Atlantic Oscillation ◽  
Rossby Wave ◽  
North Atlantic ◽  
Wave Breaking ◽  
Low Frequency ◽  
Rossby Wave Breaking ◽  
The North ◽  
The North Atlantic ◽  
Hemisphere Winter ◽  
The North Atlantic Oscillation

Abstract This paper proposes the hypothesis that the low-frequency variability of the North Atlantic Oscillation (NAO) arises as a result of variations in the occurrence of upper-level Rossby wave–breaking events over the North Atlantic. These events lead to synoptic situations similar to midlatitude blocking that are referred to as high-latitude blocking episodes. A positive NAO is envisaged as being a description of periods in which these episodes are infrequent and can be considered as a basic, unblocked situation. A negative NAO is a description of periods in which episodes occur frequently. A similar, but weaker, relationship exists between wave breaking over the Pacific and the west Pacific pattern. Evidence is given to support this hypothesis by using a two-dimensional potential-vorticity-based index to identify wave breaking at various latitudes. This is applied to Northern Hemisphere winter data from the 40-yr ECMWF Re-Analysis (ERA-40), and the events identified are then related to the NAO. Certain dynamical precursors are identified that appear to increase the likelihood of wave breaking. These suggest mechanisms by which variability in the tropical Pacific, and in the stratosphere, could affect the NAO.

Summer rainfall and wheat grain quality: Relationships with the North Atlantic Oscillation

Weather ◽  
2003 ◽  
Vol 58 (4) ◽  
pp. 155-164 ◽  
Author(s):  
Peter S. Kettlewell ◽  
David B. Stephenson ◽  
Mark D. Atkinson ◽  
Philip D. Hollins
Keyword(s):  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Grain Quality ◽  
Summer Rainfall ◽  
Wheat Grain ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation ◽  
Quality Relationships
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