Combined Effects of the British–Baikal Corridor Pattern and the Silk Road Pattern on Eurasian Surface Air Temperatures in Summer

2021 ◽  
Vol 34 (9) ◽  
pp. 3707-3720
Author(s):  
Xinyu Li ◽  
Riyu Lu ◽  
Joong-Bae Ahn
Keyword(s):  
Large Scale ◽  
Western Siberia ◽  
Surface Air Temperature ◽  
Combined Effects ◽  
High Latitudes ◽  
Eurasian Continent ◽  
Air Temperatures ◽  
Silk Road Pattern ◽  
Air Temperature Anomalies ◽  
The Silk Road

AbstractThe summer British–Baikal Corridor pattern (BBC) and the Silk Road pattern (SRP) manifest as zonally oriented teleconnections in the high and middle latitudes, respectively, of the Eurasian continent. In this study, we investigate the combined effects of the BBC and SRP on surface air temperatures over the Eurasian continent. It is found that the combination of the BBC and SRP results in two kinds of well-organized, large-scale circulation anomalies: the zonal tripole pattern and the Ω-like pattern in the 200-hPa geopotential height anomalies. The zonal tripole pattern is characterized by opposite variations between western Siberia/western Asia and Europe/central Asia/central Siberia, and the Ω-like pattern manifests as consistent variations over midlatitude Europe, western Siberia, and central Asia. Correspondingly, the resultant large-scale surface air temperature anomalies feature the same zonal tripole pattern and Ω-like pattern, respectively. Further results indicate that these two patterns resemble the two leading modes of surface air temperature anomalies over the middle to high latitudes of Eurasia. This study indicates that the temperature variations in the middle and high latitudes of Eurasia can be coordinated and evidently explained by the combination of the BBC and SRP, and it contributes to a more comprehensive understanding of the large-scale Eurasian climate variability.

scholarly journals Polar Amplification and Ice Free Conditions under 1.5, 2 and 3 °C of Global Warming as Simulated by CMIP5 and CMIP6 Models

Atmosphere ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1494
Author(s):  
Fernanda Casagrande ◽  
Francisco A. B. Neto ◽  
Ronald B. de Souza ◽  
Paulo Nobre
Keyword(s):  
Global Warming ◽  
Temperature Response ◽  
Surface Air Temperature ◽  
The Arctic ◽  
Polar Regions ◽  
High Latitudes ◽  
Near Surface ◽  
Polar Amplification ◽  
Air Temperatures ◽  
Average Rise

One of the most visible signs of global warming is the fast change in the polar regions. The increase in Arctic temperatures, for instance, is almost twice as large as the global average in recent decades. This phenomenon is known as the Arctic Amplification and reflects several mutually supporting processes. An equivalent albeit less studied phenomenon occurs in Antarctica. Here, we used numerical climate simulations obtained from CMIP5 and CMIP6 to investigate the effects of +1.5, 2 and 3 °C warming thresholds for sea ice changes and polar amplification. Our results show robust patterns of near-surface air-temperature response to global warming at high latitudes. The year in which the average air temperatures brought from CMIP5 and CMIP6 models rises by 1.5 °C is 2024. An average rise of 2 °C (3 °C) global warming occurs in 2042 (2063). The equivalent warming at northern (southern) high latitudes under scenarios of 1.5 °C global warming is about 3 °C (1.8 °C). In scenarios of 3 °C global warming, the equivalent warming in the Arctic (Antarctica) is close to 7 °C (3.5 °C). Ice-free conditions are found in all warming thresholds for both the Arctic and Antarctica, especially from the year 2030 onwards.

scholarly journals Role of Large-Scale Circulation and Terrain in Causing Extreme Heat in Western North China

2016 ◽  
Vol 29 (7) ◽  
pp. 2511-2527 ◽  
Author(s):  
Ruidan Chen ◽  
Riyu Lu
Keyword(s):  
Large Scale ◽  
North China ◽  
Surface Air Temperature ◽  
Extreme Heat ◽  
Large Scale Circulation ◽  
Air Temperatures ◽  
Higher Temperature ◽  
Upper Level ◽  
Topographic Relief

Abstract Previous studies have suggested that, because of its particular location on the southeastern lee side of mountains, extreme heat (EH) over western north China (WNC) is affected by the foehn phenomenon. In this study, the EH days during summer over this region are categorized into foehn-favorable EH and no-foehn EH, according to whether there are anomalous northwesterlies over mountains, and composite analyses are performed on them. The analyzed results indicate that the no-foehn EH is characterized by an anticyclonic anomaly and a large-scale higher surface air temperature, while the foehn-favorable EH is featured by a cyclonic anomaly to the northeast and a localized higher temperature. Associated with the cyclonic anomaly, northwesterlies prevail over the mountain surface and provide a favorable environment for the occurrence of the foehn effect over WNC, which is located on the southeastern lee side of mountains. That is, both cyclonic and anticyclonic anomalies can induce EH over WNC (i.e., foehn-favorable EH and no-foehn EH, respectively). Further investigation indicates that large-scale cyclonic and anticyclonic anomalies tend to favor local descent and ascent anomalies over the lee side, respectively, through interaction with the particular terrain. Therefore, large-scale circulations and local terrain-induced winds play an offsetting role in affecting the surface air temperatures over WNC, and EH occurs when anomalous large-scale anticyclone or terrain-induced descent dominate. This study implies that attention should be paid to not only the upper-level/large-scale circulations but also to their impact on lower-level/local winds for temperature variability over the places with great topographic relief worldwide.

scholarly journals Structure of the Western Tibetan Vortex inconsistent with a thermally-direct circulation

2021 ◽  
Author(s):  
Xiao-Feng Li ◽  
Jingjing Yu ◽  
Shaofeng Liu ◽  
Jingzhi Wang ◽  
Lei Wang
Keyword(s):  
Large Scale ◽  
Surface Air Temperature ◽  
Circulation Model ◽  
Circulation Pattern ◽  
Net Radiation ◽  
Near Surface ◽  
Radiative Balance ◽  
Air Temperatures ◽  
Western Tibetan Plateau ◽  
Global Atmospheric Circulation

AbstractThe Western Tibetan Vortex (WTV) is a large-scale circulation pattern identified from year-to-year circulation variability, which was used to understand the causal mechanisms for slowdown of the glacier melting over the western Tibetan Plateau (TP). A recent argument has suggested the WTV is the set of wind field anomalies resulting from variability in near-surface air temperatures over the western TP (above 1500 m), which, in turn, is likely driven by the surface net radiation. This study thereby evaluates the above putative thermal-direct mechanism. By conducting numerical sensitivity experiments using a global atmospheric circulation model, SAMIL, we find a WTV-like structure cannot be generated from a surface thermal forcing imposed on the western TP. A thermally-direct circulation generated by the surface or near surface heating is expect to cause upward motions and a baroclinic structure above it. In contrast, downward motions and a quasi-barotropic are observed in the vertical structure of the WTV. Besides, we find variability of the surface net radiation (sum of the surface shortwave and longwave net radiation) over the western TP can be traced back to the WTV variability based on ERA5 data. The anticyclonic (cyclonic) WTV reduces (increases) the cloudiness through the anomalous downward (upward) motions, causes more (less) input shortwave net radiation and thereby more (less) surface net radiations, resulting in the warmer (cooler) surface and near-surface air temperature over the western TP. The argument is constructive in encouraging examination of the radiative balance processes that complements previous studies.

scholarly journals Variations of oxygen-18 in West Siberian precipitation during the last 50 yr

2013 ◽  
Vol 13 (11) ◽  
pp. 29263-29301 ◽  
Author(s):  
M. Butzin ◽  
M. Werner ◽  
V. Masson-Delmotte ◽  
C. Risi ◽  
C. Frankenberg ◽  
...  
Keyword(s):  
General Circulation ◽  
Large Scale ◽  
Western Siberia ◽  
Surface Air Temperature ◽  
Circulation Model ◽  
Extended Period ◽  
Global Network ◽  
Simulated Precipitation ◽  
Precipitation Δ18o

Abstract. Global warming is associated with large increase in surface air temperature and precipitation in Siberia. Here, we apply the isotope-enhanced atmospheric general circulation model ECHAM5-wiso to investigate the variability of δ18O in West Siberian precipitation and the underlying mechanisms during the last fifty years, and to assess the potential of a recently opened monitoring station in Kourovka (57.04° N, 59.55° E) to successfully track large-scale water cycle and climate change in this area. Our model is constrained to atmospheric reanalysis fields to facilitate the comparison with precipitation δ18O from observations. In Russia, annual-mean model surface temperatures agree within ±1.5 °C with climatological data, while the model tends to overestimate precipitation by 10–20 mm month−1. Simulated precipitation δ18O shows a southwest to northeast decreasing pattern. The simulated annual-mean and seasonal δ18O results are in overall good agreement with observations from 15 Russian stations of the Global Network of Isotopes in Precipitation between 1970 and 2009. Annual-mean model results and measurements are highly correlated (r2~0.95) with a root mean square deviation of ±1‰. The model reproduces the seasonal variability of δ18O, which parallels the seasonal cycle of temperature, and the seasonal range from −25‰ in winter to −5‰ in summer. Analysing model results for the extended period 1960–2010, long-term increasing trends in temperature, precipitation and δ18O are detected in western Siberia. During the last 50 yr, winter temperatures have increased by 1.8 °C. Annual-mean precipitation rates have increased by 2–6 mm month−1 50 yr−1. Long-term trends of precipitation δ18O are also positive but at the detection limit (<1‰ 50 yr−1). Regional climate is characterized by strong interannual variability, which in winter is strongly related to the North Atlantic Oscillation. In ECHAM5-wiso, regional temperature is the predominant factor controlling δ18O variations on interannual to decadal time scales with slopes of about 0.5‰ °C−1. Focusing on Kourovka, the simulated evolution of temperature, δ18O and, to a smaller extent, precipitation during the last fifty years is synchronous with model results averaged over entire western Siberia, suggesting that this site will be representative to monitor future isotopic changes this region.

scholarly journals Differences in the Silk Road Pattern and Its Relationship to the North Atlantic Oscillation between Early and Late Summers

2018 ◽  
Vol 31 (22) ◽  
pp. 9283-9292 ◽  
Author(s):  
Xiaowei Hong ◽  
Riyu Lu ◽  
Shuanglin Li
Keyword(s):  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Late Summer ◽  
Early Summer ◽  
Silk Road ◽  
The North ◽  
Eurasian Continent ◽  
Silk Road Pattern ◽  
The North Atlantic ◽  
The Silk Road

Abstract The Silk Road Pattern (SRP) is an upper-tropospheric teleconnection pattern along the Asian westerly jet in summer on the interannual time scale, and it exerts great influences on the climate of the Eurasian continent. Results in the present study indicate that the SRP exhibits considerable distinctions between early and late summers (i.e., 1 June–9 July and 10 July–31 August, respectively). The SRP is stronger and more geographically fixed in late summer in comparison with its counterpart in early summer. Furthermore, the SRP is closely connected with the summer North Atlantic Oscillation (SNAO) in late summer, but not in early summer. This closer connection in late summer is manifested clearly in the leading mode of upper-tropospheric meridional wind anomalies over the North Atlantic–Eurasian continent domain. The intensified SNAO–SRP relationship in late summer can be explained by the subseasonal change of the SNAO: albeit being a seesaw pattern common in both early and late summers, there is a shift of this pattern toward the northwest–southeast one in late summer from a north–south one in early summer. The southeastern pole of SNAO in late summer extends into the Eurasian continent, and efficiently triggers the SRP to propagate along the Asian jet. By contrast, the south pole of SNAO in early summer is confined over the North Atlantic and is thus less effective to trigger the SRP propagation.

scholarly journals VARIATIONS IN THE SURFACE AIR TEMPERATURE IN THE SOUTH OF SIBERIA AND THEIR RELATIONSHIP WITH LARGE-SCALE CIRCULATION PROCESSES IN THE ATMOSPHERE

2021 ◽  
pp. 75-84
Author(s):  
Elena V. Noskova ◽  
◽  
Victor A. Obyazov ◽  
Irina L. Vahnina ◽  
◽  
...  
Keyword(s):  
Air Temperature ◽  
Large Scale ◽  
Surface Air Temperature ◽  
Economic Effects ◽  
Winter Period ◽  
The South ◽  
Air Temperatures ◽  
South Of Siberia ◽  
Almost All ◽  
Continental Climate

The article analyzes changes in surface air temperature in the south of Siberia, in 8 regions of the Russian Federation. Based on the geographical and climatic approaches, the study area was divided into four zones. It is shown that interannual changes in air temperature both within the identified zones and between them are consistent, while changes in the series of average monthly air temperatures are not so unambiguous. The calculated values of the linear trends of long-term changes in the mean annual air temperature indicate that, despite its widespread significant increase, in the last decade, a slowdown in the temperature growth has been noted across the territory of southern Siberia. An increase in air temperature is observed in almost all months of the year, with the exception of the winter period, when, according to data from individual meteorological stations, a slight fall in temperature is noted. An assessment of the relationship between air temperature and circulation mechanisms, carried out using correlation analysis, indicates a significant influence of the Scandinavian teleconnection index practically throughout the year in zones related to areas of continental climate. In areas of a sharply continental climate, its influence decreases to some extent, especially in summer, although it remains the leading factor in some months. The ongoing climatic changes cannot but entail both positive and negative socio-economic effects. In this regard, the results of the research should be taken into account when developing mechanisms for adapting the economy to climate change at regional levels.

Large-Scale Atmospheric Circulation Related to Frequent Rossby Wave Breaking near Japan in Boreal Summer

2020 ◽  
Vol 33 (15) ◽  
pp. 6731-6744
Author(s):  
Kazuto Takemura ◽  
Hitoshi Mukougawa ◽  
Shuhei Maeda
Keyword(s):  
Atmospheric Circulation ◽  
Rossby Wave ◽  
Wave Breaking ◽  
Large Scale ◽  
Boreal Summer ◽  
Rossby Wave Breaking ◽  
The Pacific ◽  
Silk Road Pattern ◽  
Large Scale Atmospheric Circulation ◽  
The Silk Road

AbstractRossby wave propagation along the Asian jet during boreal summer, such as the Silk Road pattern, frequently causes wave breaking near the Asian jet exit region. This study examines the statistical relationship between interannual variability of the Rossby wave breaking frequency near Japan and large-scale atmospheric circulation during the boreal summer. The Rossby wave breaking frequency in the midlatitudes climatologically shows its maximum near Japan, and significantly increases during La Niña years. The upper-tropospheric circulation regressed onto the Rossby wave breaking frequency near Japan in August shows large-scale anomalous convergence from the tropical central to eastern Pacific and divergence around the Indian Ocean. The consequent northward anomalous divergent wind over Eurasia contributes to enhancement and northward shift of the Asian jet. The Asian jet also shows meridional meandering with a phase of anomalous anticyclonic circulation near Japan accompanied by the frequent Rossby wave breaking, which is associated with the Silk Road pattern. The frequent Rossby wave breaking is related to southwestward intrusion of anomalous low potential temperature air mass toward the subtropical western North Pacific associated with an enhanced mid-Pacific trough. West of the southwestward cold-air intrusion, enhanced cumulus convection is seen around the northern Philippines, and the Pacific–Japan pattern is significantly seen in the lower troposphere. This result is consistent with a previous study that revealed a linkage mechanism between the Rossby wave breaking near Japan and the Pacific–Japan pattern through dynamically induced ascent resulting in an intrusion of high potential vorticity associated with the Rossby wave breaking.

Relationship between Warm Airmass Transport into the Upper Polar Atmosphere and Cold Air Outbreaks in Winter

2015 ◽  
Vol 72 (1) ◽  
pp. 349-368 ◽  
Author(s):  
Yueyue Yu ◽  
Ming Cai ◽  
Rongcai Ren ◽  
Huug M. van den Dool
Keyword(s):  
Air Temperature ◽  
Polar Region ◽  
Lower Troposphere ◽  
Surface Air Temperature ◽  
The Other ◽  
High Latitudes ◽  
Cold Air ◽  
Mass Circulation ◽  
Air Temperature Anomalies ◽  
Cold Air Outbreaks

Abstract This study investigates dominant patterns of daily surface air temperature anomalies in winter (November–February) and their relationship with the meridional mass circulation variability using the daily Interim ECMWF Re-Analysis in 1979–2011. Mass circulation indices are constructed to measure the day-to-day variability of mass transport into the polar region by the warm air branch aloft and out of the polar region by the cold air branch in the lower troposphere. It is shown that weaker warm airmass transport into the upper polar atmosphere is accompanied by weaker equatorward advancement of cold air in the lower troposphere. As a result, the cold air is largely imprisoned within the polar region, responsible for anomalous warmth in midlatitudes and anomalous cold in high latitudes. Conversely, stronger warm airmass transport into the upper polar atmosphere is synchronized with stronger equatorward discharge of cold polar air in the lower troposphere, resulting in massive cold air outbreaks in midlatitudes and anomalous warmth in high latitudes. There are two dominant geographical patterns of cold air outbreaks during the cold air discharge period (or 1–10 days after a stronger mass circulation across 60°N). One represents cold air outbreaks in midlatitudes of both North America and Eurasia, and the other is the dominance of cold air outbreaks only over one of the two continents with abnormal warmth over the other continent. The first pattern mainly corresponds to the first and fourth leading empirical orthogonal functions (EOFs) of daily surface air temperature anomalies in winter, whereas the second pattern is related to the second EOF mode.

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