scholarly journals Recent Strengthened Impact of the Winter Arctic Oscillation on the Southeast Asian Surface Air Temperature Variation

Atmosphere ◽  
2019 ◽  
Vol 10 (4) ◽  
pp. 164 ◽  
Author(s):  
Shangfeng Chen ◽  
Linye Song
Keyword(s):  
Southeast Asia ◽  
Air Temperature ◽  
Arctic Oscillation ◽  
Surface Air Temperature ◽  
Southeast Asian ◽  
The Arctic ◽  
Interdecadal Change ◽  
Northerly Wind ◽  
The North ◽  
The Impact

A previous study indicated that the Arctic Oscillation (AO) and Siberian High (SH) are two important drivers for the interannual variation of winter surface air temperature (SAT) over southeast Asia. This study reveals that the impact of the winter SH on the southeast Asian SAT was stable. By contrast, the connection between the winter AO and southeast Asian SAT displays a pronounced interdecadal change around the late-1990s. Significant impact of the winter AO on the southeast Asian SAT can only be detected after the late-1990s. The result shows that change in the impact of the winter AO on southeast Asian SAT was mainly attributed to change in the spatial structure of the AO. Before the late-1990s, significant atmospheric signals related to the winter AO were confined to the North Atlantic region and the atmospheric anomalies over Eurasia were weak. As such, impact of the winter AO on the southeast Asian SAT was weak. By contrast, after the late-1990s, winter AO displays a more zonally symmetric structure, with significant negative sea level pressure (SLP) anomalies over the Arctic, and positive anomalies over mid-latitudes. Specifically, the positive SLP anomalies over East China induce clear northerly wind anomalies over southeast Asia, which lead to negative SAT anomalies there via wind-induced temperature advection. Hence, the winter AO has a significant impact on the southeast Asian SAT after the late-1990s. Further analysis shows that after the late-1990s, hindcast skill of the winter southeast Asian SAT anomalies was enhanced when taking both the winter AO and SH into account.

scholarly journals Multidecadal Changes in the Influence of the Arctic Oscillation on the East Asian Surface Air Temperature in Boreal Winter

Atmosphere ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 757 ◽  
Author(s):  
Hainan Gong ◽  
Lin Wang ◽  
Wen Chen
Keyword(s):  
East Asia ◽  
Air Temperature ◽  
North Pacific ◽  
Arctic Oscillation ◽  
Regional Climate ◽  
East Asian ◽  
Surface Air Temperature ◽  
The Arctic ◽  
Boreal Winter ◽  
The Impact

The time-varying influences of the wintertime Arctic Oscillation (AO) on the concurrent East Asian surface air temperature (EAT) are investigated based on JRA-55 reanalysis data. Results reveal that there are multidecadal variations in the influences of wintertime AO on the EAT during 1958–2018. Before the mid-1980s, the impact of winter AO on the simultaneous EAT is weak and confined northward of 40° N over East Asia. After the mid-1980s, by contrast, the winter AO’s influence is stronger and can extend southward of 25° N over East Asia. The multidecadal variations of the winter AO–EAT relationship are mainly modulated by the magnitudes of the North Pacific center of the winter AO. During the periods with strong North Pacific center of the winter AO, in association with the positive phase of the winter AO, the low-level southeasterly anomalies on the west side of the anticyclone over North Pacific bring warm air from the ocean to East Asia and lead to a significant winter AO–EAT relationship. In contrast, the southerly anomalies are weak and even reversed to northerly over the coast of East Asia during the periods with weak North Pacific center of winter AO, which confines the influence of winter AO on northern East Asia and lead to an insignificant winter AO–EAT relationship. Our finding provides new insight into the understanding of the decadal changes of AO’s impacts on the regional climate.

scholarly journals Spatiotemporal Characteristics of the Dominant Modes of Surface Air Temperature Interannual Variations over South China during the Spring-to-Summer Transition

Atmosphere ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 65
Author(s):  
Fen Wang ◽  
Yaokun Li ◽  
Jianping Li
Keyword(s):  
Heat Flux ◽  
Air Temperature ◽  
South China ◽  
Surface Heat Flux ◽  
Surface Air Temperature ◽  
Surface Heat ◽  
Shortwave Radiation ◽  
Northerly Wind ◽  
The North ◽  
Land Surfaces

The surface air temperature (SAT) interannual variability during the spring-to-summer transition over South China (SC) has been decomposed into two dominant modes by applying empirical orthogonal function (EOF) analysis. The first EOF mode (EOF1) is characterized by homogenous SAT anomalies over SC, whereas the second EOF mode (EOF2) features a dipole SAT anomaly pattern with opposite anomalies south and north of the Yangtze River. A regression analysis of surface heat flux and advection anomalies on the normalized principle component time series corresponding to EOF1 suggests that surface heat flux anomalies can explain SAT anomalies mainly by modulating cloud-shortwave radiation. Negative cloud anomalies result in positive downward shortwave radiation anomalies through the positive shortwave cloud radiation effect, which favor warm SAT anomalies over most of SC. For EOF2, the distribution of advection anomalies resembles the north–south dipole pattern of SAT anomalies. This suggests that wind-induced advection plays an important role in the SAT anomalies of EOF2. Negative SAT anomalies are favored by cold advection from northerly wind anomalies over land surfaces in high-latitude regions. Positive SAT anomalies are induced by warm advection from southerly wind anomalies over the ocean in low-latitude regions.

Contrasting Impacts of the Arctic Oscillation on Surface Air Temperature Anomalies in Southern China between Early and Middle-to-Late Winter

2015 ◽  
Vol 28 (10) ◽  
pp. 4015-4026 ◽  
Author(s):  
Jinqing Zuo ◽  
Hong-Li Ren ◽  
Weijing Li
Keyword(s):  
Mediterranean Sea ◽  
Air Temperature ◽  
Arctic Oscillation ◽  
Southern China ◽  
Phase Relationship ◽  
Surface Air Temperature ◽  
The Arctic ◽  
Late Winter ◽  
Upper Level ◽  
The Arctic Oscillation

Abstract In the boreal winter, the Arctic Oscillation (AO) evidently acts to influence surface air temperature (SAT) anomalies in China. This study reveals a large intraseasonal variation in the relationship between the winter AO and southern China SAT anomalies. Specifically, a weak in-phase relationship occurs in December, but a significant out-of-phase relationship occurs in January and February. The authors show that the linkage between the AO and southern China SAT anomalies strongly depends on the AO-associated changes in the Middle East jet stream (MEJS) and that such an AO–MEJS relationship is characterized by a significant difference between early and middle-to-late winter. In middle-to-late winter, the Azores center of high pressure anomalies in the positive AO phase usually extends eastward and yields a significantly anomalous upper-level convergence over the Mediterranean Sea, which can excite a Rossby wave train spanning the Arabian Sea and intensify the MEJS. In early winter, however, the Azores center of the AO is apparently shifted westward and is mainly confined to the Atlantic Ocean; in this case, the associated change in the MEJS is relatively weak. Both observational diagnoses and experiments based on a linearized barotropic model suggest that the MEJS is closely linked to the AO only when the latter generates considerable upper-level convergence anomalies over the Mediterranean Sea. Therefore, the different impacts of the AO on the MEJS and the southern China SAT anomalies between early and middle-to-late winter are primarily attributed to the large intraseasonal zonal migrations of the Azores center of the AO.

Late 20th century increase in northern Svalbard glacier-derived runoff tracked by encrusting coralline algae

2020 ◽  
Author(s):  
Steffen Hetzinger ◽  
Jochen Halfar ◽  
Zoltan Zajacz ◽  
Marco Möller ◽  
Max Wisshak
Keyword(s):  
Global Warming ◽  
Air Temperature ◽  
Surface Air Temperature ◽  
High Arctic ◽  
Climate System ◽  
Coralline Algae ◽  
The Arctic ◽  
Surface Ocean ◽  
The Impact ◽  
Arctic Surface

<p>The Arctic cryosphere is changing at a rapid pace due to global warming and the large-scale changes observed in the Arctic during the past decades exert a strong influence throughout the global climate system. The warming of Arctic surface air temperatures is more than twice as large as the global average over the last two decades and recent events indicate new extremes in the Arctic climate system, e.g. for the last five years Arctic annual surface air temperature exceeded that of any year since 1900 AD. Northern Spitsbergen, Svalbard, located in the High Arctic at 80°N, is a warming hotspot with an observed temperature rise of ~6°C over the last three decades indicating major global warming impacts. However, even the longest available datasets on Svalbard climatic conditions do not extend beyond the 1950s, inhibiting the study of long-term natural variability before anthropogenic influence. Ongoing climate trends strongly affect the state of both glaciers and seasonal snow in Svalbard. Modeled data suggest a marked increase in glacier runoff during recent decades in northern Svalbard. However, observational data are sparse and short and the potential effects on the surface ocean are unclear.<br>This study focuses on the ultra-high-resolution analysis of calcified coralline algal buildups growing attached to the shallow seafloor along Arctic coastlines. Analysis of these new annually-layered climate archives is based on the long-lived encrusting coralline algae <em>Clathromorphum compactum</em>, providing a historic perspective on recently observed changes. Here, we present a 200-year record of past surface ocean variability from Mosselbukta, Spitsbergen, northern Svalbard. By using algal Ba/Ca ratios as a proxy for past glacier-derived meltwater input, we investigate past multi-decadal-scale fluctuations in land-based freshwater contributions to the ocean surface layer. Our records, based on multiple coralline algal specimens, show a strong and statistically significant increasing trend in algal Ba/Ca ratios from the 1990s onwards, suggesting a drastic increase in land-based runoff at Mosselbukta. The drastic rate of increase is unprecedented during the last two centuries, directly capturing the impact of amplified surface air temperature warming on coastal high Arctic surface ocean environments.</p><p> </p>

scholarly journals An Investigation into the Impact of using Various Techniques to Estimate Arctic Surface Air Temperature Anomalies*

2015 ◽  
Vol 28 (5) ◽  
pp. 1743-1763 ◽  
Author(s):  
Emma M. A. Dodd ◽  
Christopher J. Merchant ◽  
Nick A. Rayner ◽  
Colin P. Morice
Keyword(s):  
Time Series ◽  
Sea Ice ◽  
Air Temperature ◽  
Surface Air Temperature ◽  
Meteorological Station ◽  
The Arctic ◽  
Test Bed ◽  
Recent Climate ◽  
The Impact ◽  
Mean Square Errors

Abstract Time series of global and regional mean surface air temperature (SAT) anomalies are a common metric used to estimate recent climate change. Various techniques can be used to create these time series from meteorological station data. The degree of difference arising from using five different techniques, based on existing temperature anomaly dataset techniques, to estimate Arctic SAT anomalies over land and sea ice was investigated using reanalysis data as a test bed. Techniques that interpolated anomalies were found to result in smaller errors than noninterpolating techniques relative to the reanalysis reference. Kriging techniques provided the smallest errors in estimates of Arctic anomalies, and simple kriging was often the best kriging method in this study, especially over sea ice. A linear interpolation technique had, on average, root-mean-square errors (RMSEs) up to 0.55 K larger than the two kriging techniques tested. Noninterpolating techniques provided the least representative anomaly estimates. Nonetheless, they serve as useful checks for confirming whether estimates from interpolating techniques are reasonable. The interaction of meteorological station coverage with estimation techniques between 1850 and 2011 was simulated using an ensemble dataset comprising repeated individual years (1979–2011). All techniques were found to have larger RMSEs for earlier station coverages. This supports calls for increased data sharing and data rescue, especially in sparsely observed regions such as the Arctic.

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