scholarly journals What Leads to Persisting Surface Air Temperature Anomalies from Winter to Following Spring over Mid- to High-Latitude Eurasia?

2020 ◽  
Vol 33 (14) ◽  
pp. 5861-5883 ◽  
Author(s):  
Renguang Wu ◽  
Shangfeng Chen
Keyword(s):  
Atmospheric Circulation ◽  
Air Temperature ◽  
North Atlantic ◽  
High Latitude ◽  
Surface Air Temperature ◽  
Circulation Anomaly ◽  
The North ◽  
Anomaly Pattern ◽  
The North Atlantic ◽  
Atmospheric Circulation Anomaly

AbstractSurface air temperature (SAT) anomalies tend to persist from winter to the following spring over the mid- to high latitudes of Eurasia. The present study compares two distinct cases of Eurasian SAT anomaly evolution and investigates the reasons for the persistence of continental-scale mid- to high-latitude Eurasian SAT anomalies from winter to following spring (termed persistent cases). The persisting SAT anomalies are closely associated with the sustenance of large-scale atmospheric circulation anomaly pattern over the North Atlantic and Eurasia, featuring a combination of the North Atlantic Oscillation/Arctic Oscillation (NAO/AO) and the Scandinavian pattern, from winter to spring. The combined circulation anomalies result in SAT warming over most of mid- to high-latitude Eurasia via anomalous wind-induced temperature advection. The sustenance of atmospheric circulation anomaly pattern is related to the maintenance of the North Atlantic triple sea surface temperature (SST) anomaly pattern due to air–sea interaction processes. The Barents Sea ice anomalies, which form in winter and increase in spring, also partly contribute to the sustenance of atmospheric circulation anomalies via modulating thermal state of the lower troposphere. In the cases that notable SAT warming (cooling) in winter is replaced by pronounced SAT cooling (warming) in the subsequent spring—termed reverse cases—the North Atlantic SST anomalies become small and the Greenland Sea ice change is a response to atmospheric change in spring. Without the support of lower boundary forcing, the atmospheric circulation anomaly pattern experiences a reverse in the spatial distribution from winter to spring likely due to internal atmospheric processes.

scholarly journals Interdecadal Changes in the Relationship between Interannual Variations of Spring North Atlantic SST and Eurasian Surface Air Temperature

2017 ◽  
Vol 30 (10) ◽  
pp. 3771-3787 ◽  
Author(s):  
Shangfeng Chen ◽  
Renguang Wu
Keyword(s):  
Atmospheric Circulation ◽  
North Atlantic ◽  
Surface Air Temperature ◽  
The North ◽  
Anomaly Pattern ◽  
Sst Anomaly ◽  
The North Atlantic ◽  
Atmospheric Circulation Anomalies ◽  
The Relationship ◽  
Interdecadal Changes

Abstract This study investigates interdecadal changes in the relationship between interannual variations of boreal spring sea surface temperature (SST) in the North Atlantic and surface air temperature (SAT) over the mid-to-high latitudes of Eurasia during 1948–2014. Analyses show that the connection between the spring North Atlantic tripole SST anomaly pattern and the Eurasian SAT anomalies has experienced marked interdecadal shifts around the early 1970s and mid-1990s. The connection is strong during 1954–72 and 1996–2014 but weak during 1973–91. A diagnosis indicates that interdecadal changes in the connection between the North Atlantic SST and Eurasian SAT variations are associated with changes in atmospheric circulation anomalies over Eurasia induced by the North Atlantic tripole SST anomaly pattern. Further analyses suggest that changes in atmospheric circulation anomalies over Eurasia are related to changes in the position of atmospheric heating anomalies over the North Atlantic, which may be due to the change in mean SST. Marked atmospheric heating anomalies appear over the tropical western North Atlantic during 1954–72 and 1996–2014 but over the subtropical central-eastern North Atlantic during 1973–91. Barotropic model experiments confirm that different background flows may also contribute to changes in anomalous atmospheric circulation over Eurasia.

North Hemispheric winter air temperature variability and its linkage to North Pacific and North Atlantic SST modes?

2020 ◽  
Author(s):  
Binhe Luo ◽  
Dehai Luo ◽  
Aiguo Dai ◽  
Lixin Wu
Keyword(s):  
North America ◽  
Air Temperature ◽  
North Atlantic ◽  
North Pacific ◽  
Wave Train ◽  
Surface Air Temperature ◽  
Eastern North America ◽  
The North ◽  
The North Atlantic ◽  
The North Pacific

<p>Winter surface air temperature (SAT) over North America exhibits pronounced variability on sub-seasonal-to-interdecadal timescales, but its causes are not fully understood. Here observational and reanalysis data from 1950-2017 are analyzed to investigate these causes. Detrended daily SAT data reveals a known warm-west/cold-east (WWCE) dipole over midlatitude North America and a cold-north/warm-south (CNWS) dipole over eastern North America. It is found that while the North Pacific blocking (PB) is important for the WWCE and CNWS dipoles, they also depend on the phase of the North Atlantic Oscillation (NAO). When a negative-phase NAO (NAO-) concurs with PB, the WWCE dipole is enhanced (compared with the PB alone case) and it also leads to a warm north/cold south dipole anomaly in eastern North America; but when PB occurs with a positive-phase NAO (NAO<sup>+</sup>), the WWCE dipole weakens and the CNWS dipole is enhanced. In particular, the WWCE dipole is favored by a combination of eastward-displaced PB and NAO<sup>-</sup> that form a negative Arctic Oscillation. Furthermore, a WWCE dipole can form over midlatitude North America when PB occurs together with southward-displaced NAO<sup>+</sup>.The PB events concurring with NAO<sup>-</sup> (NAO<sup>+</sup>) and SAT WWCE (CNWS) dipole are favored by the El Nio-like (La Nia-like) SST mode, though related to the North Atlantic warm-cold-warm (cold-warm-cold) SST tripole pattern. It is also found that the North Pacific mode tends to enhance the WWCE SAT dipole through increasing PB-NAO<sup>-</sup> events and producing the WWCE SAT dipole component related to the PB-NAO<sup>+</sup> events because the PB and NAO<sup>+</sup> form a more zonal wave train in this case.</p>

The AMV phase-dependence of the connection between February NAO and March surface air temperature over the Tibetan Plateau

2021 ◽  
Author(s):  
Jingyi Li ◽  
Fei Li ◽  
Shengping He ◽  
Huijun Wang ◽  
Yvan J Orsolini
Keyword(s):  
Tibetan Plateau ◽  
Air Temperature ◽  
Rossby Wave ◽  
North Atlantic ◽  
Wave Train ◽  
Surface Air Temperature ◽  
The Tibetan Plateau ◽  
The North ◽  
Rossby Wave Train ◽  
The North Atlantic

<p>The Tibetan Plateau (TP), referred to as the “Asian water tower”, contains one of the largest land ice masses on Earth. The local glacier shrinkage and frozen-water storage are strongly affected by variations in surface air temperature over the TP (TPSAT), especially in springtime. This study reveals a distinct out-of-phase connection between the February North Atlantic Oscillation (NAO) and March TPSAT, which is non-stationary and regulated by the warm phase of the Atlantic Multidecadal Variability (AMV+). The results show that during the AMV+, the negative phase of the NAO persists from February to March, and is accompanied by a quasi-stationary Rossby wave train trapped along a northward-shifted subtropical westerly jet stream across Eurasia, inducing an anomalous adiabatic descent that warms the TP. However, during the cold phase of the AMV, the negative NAO does not persist into March. The Rossby wave train propagates along the well-separated polar and subtropical westerly jets, and the NAO−TPSAT connection is broken. Further investigation suggests that the enhanced synoptic eddy and low-frequency flow (SELF) interaction over the North Atlantic in February and March during the AMV+, caused by the enhanced and southward-shifted storm track, help maintain the NAO anomaly pattern via positive eddy feedback. This study provides a new detailed perspective on the decadal variability of the North Atlantic−TP connections in late winter−early spring.</p>

Why Does a Colder (Warmer) Winter Tend to Be Followed by a Warmer (Cooler) Summer over Northeast Eurasia?

2020 ◽  
Vol 33 (17) ◽  
pp. 7255-7274
Author(s):  
Shangfeng Chen ◽  
Renguang Wu ◽  
Wen Chen ◽  
Kai Li
Keyword(s):  
Atmospheric Circulation ◽  
North Atlantic ◽  
Wave Train ◽  
The Arctic ◽  
The North ◽  
Atmospheric Wave ◽  
Anomaly Pattern ◽  
Sst Anomaly ◽  
The North Atlantic ◽  
Sst Anomalies

AbstractThis study reveals a pronounced out-of-phase relationship between surface air temperature (SAT) anomalies over northeast Eurasia in boreal winter and the following summer during 1980–2017. A colder (warmer) winter over northeast Eurasia tends to be followed by a warmer (cooler) summer of next year. The processes for the out-of-phase relation of winter and summer SAT involve the Arctic Oscillation (AO), the air–sea interaction in the North Atlantic Ocean, and a Eurasian anomalous atmospheric circulation pattern induced by the North Atlantic sea surface temperature (SST) anomalies. Winter negative AO/North Atlantic Oscillation (NAO)-like atmospheric circulation anomalies lead to continental cooling over Eurasia via anomalous advection and a tripolar SST anomaly pattern in the North Atlantic. The North Atlantic SST anomaly pattern switches to a dipolar pattern in the following summer via air–sea interaction processes and associated surface heat flux changes. The summer North Atlantic dipolar SST anomaly pattern induces a downstream atmospheric wave train, including large-scale positive geopotential height anomalies over northeast Eurasia, which contributes to positive SAT anomalies there via enhancement of downward surface shortwave radiation and anomalous advection. Barotropic model experiments verify the role of the summer North Atlantic SST anomalies in triggering the atmospheric wave train over Eurasia. Through the above processes, a colder winter is followed by a warmer summer over northeast Eurasia. The above processes apply to the years when warmer winters are followed by cooler summers except for opposite signs of SAT, atmospheric circulation, and SST anomalies.

scholarly journals Atlantic Ocean Influence on Middle East Summer Surface Air Temperature

2020 ◽  
Author(s):  
Muhammad Azhar Ehsan ◽  
Dario Nicolì ◽  
Fred Kucharski ◽  
Mansour Almazroui ◽  
Michael Tippett ◽  
...  
Keyword(s):  
Middle East ◽  
Atlantic Ocean ◽  
Air Temperature ◽  
North Atlantic ◽  
Surface Air Temperature ◽  
Ocean Model ◽  
Boreal Summer ◽  
Multidecadal Variability ◽  
The North ◽  
The North Atlantic

<p>Middle East surface air temperature (ME−SAT), during boreal summer (June to August: JJA), shows robust multidecadal variations for the period 1948−2016. Here using observational and reanalysis datasets as well as coupled atmosphere−ocean model simulations, we linked the observed summer ME−SAT variability to the multidecadal variability of sea surface temperature (SST) in the North Atlantic Ocean (AMV). This Atlantic−ME connection during summer involves ocean−atmosphere interactions through multiple ocean basins, with an influence from the Indian Ocean and the Arabian Sea. The downstream response to Atlantic SST is a weakening of the subtropical westerly jet stream that impacts summer ME−SAT variability through a wave−like pattern in the upper tropospheric levels. The Atlantic SST response is further characterized by positive geopotential height anomalies in the upper levels over the Eurasian region and dipole−like pressure distribution over the ME lower levels. For positive Atlantic SST anomalies, this pressure gradient initiates anomalous low−level southerly flow, which transports moisture from the neighboring water bodies toward the extremely hot and dry ME landmass. The increase in atmospheric moisture reduces the longwave radiation damping of the SAT anomaly, increasing further ME−SAT. A suite of Atlantic Pacemaker experiments skillfully reproduces the North Atlantic−ME teleconnection. Our findings reveal that in observations and models the Atlantic Ocean acts as a critical pacemaker for summer ME−SAT multidecadal variability and that a positive AMV can lead to enhanced summer warming over the Middle East.</p>

scholarly journals Enhanced Linkage between Eurasian Winter and Spring Dominant Modes of Atmospheric Interannual Variability since the Early 1990s

2018 ◽  
Vol 31 (9) ◽  
pp. 3575-3595 ◽  
Author(s):  
Shangfeng Chen ◽  
Renguang Wu ◽  
Wen Chen ◽  
Shuailei Yao
Keyword(s):  
Interannual Variability ◽  
Atmospheric Circulation ◽  
North Atlantic ◽  
Wave Train ◽  
Seasonal Prediction ◽  
Dominant Mode ◽  
The North ◽  
Anomaly Pattern ◽  
Sst Anomaly ◽  
The North Atlantic

The present study reveals a marked enhancement in the relationship between Eurasian winter and spring atmospheric interannual variability since the early 1990s. Specifically, the dominant mode of winter Eurasian 500-hPa geopotential height anomalies, with same-sign anomalies over southern Europe and East Asia and opposite-sign anomalies over north-central Eurasia, is largely maintained to the following spring after the early 1990s, but not before the early 1990s. The maintenance of the dominant atmospheric circulation anomaly pattern after the early 1990s is associated with a triple sea surface temperature (SST) anomaly pattern in the North Atlantic that is sustained from winter to the subsequent spring. This triple SST anomaly pattern triggers an atmospheric wave train over the North Atlantic through Eurasia during winter through spring. Atmospheric model experiments verify the role of the triple SST anomaly in maintaining the Eurasian atmospheric circulation anomalies. By contrast, before the early 1990s, marked SST anomalies related to the winter dominant mode only occur in the tropical North Atlantic during winter and they disappear during the following spring. The triple SST anomaly pattern after the early 1990s forms in response to a meridional atmospheric dipole over the North Atlantic induced by a La Niña–like cooling over tropical Pacific, and its maintenance into the following spring may be via a positive air–sea interaction process over the North Atlantic. Results of this analysis suggest a potential source for the seasonal prediction of the Eurasian spring climate.

Volcanic imprint in the North Atlantic climate variability as recorded by stable water isotopes of Greenland ice cores

2020 ◽  
Author(s):  
Hera Guðlaugsdóttir ◽  
Jesper Sjolte ◽  
Árný Erla Sveinbjörnsdóttir ◽  
Hans Christian Steen-Larsen
Keyword(s):  
Climate Variability ◽  
North Atlantic Oscillation ◽  
Atmospheric Circulation ◽  
North Atlantic ◽  
High Latitude ◽  
Ice Cores ◽  
Volcanic Eruptions ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract Volcanic eruptions are important drivers of climate variability on both seasonal and multi-decadal time scales as a result of atmosphere-ocean coupling. While the direct response after equatorial eruptions emerges as the positive phase of the North Atlantic Oscillation in the first two years after an eruption, less is known about high latitude northern hemisphere eruptions. In this study we assess the difference between equatorial and high latitude volcanic eruptions through the reconstructed atmospheric circulation and stable water isotope records of Greenland ice cores for the last millennia (1241-1979 CE), where the coupling mechanism behind the long-term response is addressed. The atmospheric circulation is studied through the four main modes of climate variability in the North Atlantic, the Atlantic Ridge, Scandinavian Blocking and the positive and negative phase of the North Atlantic Oscillation. We report a difference in the atmospheric circulation response after high latitude eruptions compared to the response after equatorial eruptions, where the positive phase of the North Atlantic Oscillation and the Atlantic Ridge seem to be more associated with equatorial eruptions while the negative phase of the North Atlantic Oscillation seems to follow high latitude eruptions. This response is present during the first five years and then again in years 8-12 after both equatorial and high latitude eruptions. Such a prolonged response is evidence of an ocean-atmosphere coupling that is initiated through different mechanisms, where we suspect sea ice to play a key role.

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