China’s Recent Progresses in Polar Climate Change and Its Interactions with the Global Climate System

During the recent four decades since 1980,a series of modern climate satellites were launched,allowing for the measurement and record-keeping of multiple climate parameters,especially over the polar regions where traditional observations are difficult to obtain.China has been actively engaging in polar expeditions.Many observations were conducted during this period,accompanied by improved Earth climate models,leading to a series of insightful understandings concerning Arctic and Antarctic climate changes.Here,we review the recent progress China has made concerning Arctic and Antarctic climate change research over the past decade.The Arctic temperature increase is much higher than the global-mean warming rate,associated with a rapid decline in sea ice,a phenomenon called the Arctic Amplification.The Antarctic climate changes showed a zonally asymmetric pattern over the past four decades,with most of the fastest changes occurring over West Antarctica and the Antarctic Peninsula.The Arctic and Antarctic climate changes were driven by anthropogenic greenhouse gas emissions and ozone loss,while tropical-polar teleconnections play important roles in driving the regional climate changes and extreme events over the polar regions.Polar climate changes may also feedback to the entire Earth climate system.The adjustment of the circulation in both the troposphere and the stratosphere contributed to the interactions between the polar climate changes and lower latitudes.Climate change has also driven rapid Arctic and Southern ocean acidification.Chinese researchers have made a series of advances in understanding these processes,as reviewed in this paper.

An addition of medium-dose ATG to conditioning regimens favours the long-term survival of patients with allogeneic hematopoietic stem cell transplantation

Long-term survival of 116 leukemia/MDS patients received allo-SCT conditioned by a regimen with ATG-F or without ATG-F was analysed, together with the impact of ATG-F on the long-term survival, GVHD and disease relapse. Seventy patients received an ATG-F containing conditioning regimen FBCA, and 46 patients received a non-ATG-F FBC regimen. The FBCA regimen was associated with a 5-year survival of 65.4% in the complete HLA-matched group and 39.3% in the HLA-mismatched group. The difference between the two groups was significant (P = 0.012). For the FBC conditioning regimen, the 5-year overall survival of HLA-matched patients and the HLA-mismatched patients was 34.2% and 24.2% respectively (P = 0.216). The incidence of cGVHD was 32.9% and 83.6% in the FBCA and FBC condition regimen group respectively. Only 2.9% of the cases showed extensive cGVHD in the FBCA group while it was 69.4% in the FBC group (P = 0.00). Multivariate analysis indicated that relapse was related to the disease status and HLA typing, but unrelated to the conditioning regimens whether or not ATG-F was used (HR 0.54, P = 0.109). We conclude that the addition of ATG-F to conditioning regimen favours the longterm survival of allo-SCT.

Arctic sea ice bordering on the North Atlantic and inter-annual climate variations

Variations of winter Arctic sea ice bordering on the North Atlantic are closely related to climate variations in the same region. When winter North Atlantic Oscillation (NAO) index is positive (negative) anomaly phase, Icelandic Low is obviously deepened and shifts northwards (southwards). Simultaneously, the Subtropical High over the North Atlantic is also intensified, and moves northwards (southwards). Those anomalies strengthen (weaken) westerly between Icelandic Low and the Subtropical High, and further result in positive (negative) sea surface temperature (SST) anomalies in the mid-latitude of the North Atlantic, and increase (decrease) the warm water transportation from the mid-latitude to the Barents Sea, which causes positive (negative) mixed-layer water temperature anomalies in the south part of the Barents Sea. Moreover, the distribution of anomaly air temperature clearly demonstrates warming (cooling) in northern Europe and the subarctic regions (including the Barents Sea) and cooling

Arctic Climate Changes Based on Historical Simulations(1900-2013) with the CAMS-CSM

The Chinese Academy of Meteorological Sciences Climate System Model(CAMS-CSM) is a newly developed global climate model that will participate in the Coupled Model Intercomparison Project phase 6. Based on historical simulations(1900-2013), we evaluate the model performance in simulating the observed characteristics of the Arctic climate system, which includes air temperature, precipitation, the Arctic Oscillation(AO), ocean temperature/salinity,the Atlantic meridional overturning circulation(AMOC), snow cover, and sea ice. The model-data comparisons indicate that the CAMS-CSM reproduces spatial patterns of climatological mean air temperature over the Arctic(60°-90°N) and a rapid warming trend from 1979 to 2013. However, the warming trend is overestimated south of the Arctic Circle, implying a subdued Arctic amplification. The distribution of climatological precipitation in the Arctic is broadly captured in the model, whereas it shows limited skills in depicting the overall increasing trend. The AO can be reproduced by the CAMS-CSM in terms of reasonable patterns and variability. Regarding the ocean simulation, the model underestimates the AMOC and zonally averaged ocean temperatures and salinity above a depth of 500 m, and it fails to reproduce the observed increasing trend in the upper ocean heat content in the Arctic. The largescale distribution of the snow cover extent(SCE) in the Northern Hemisphere and the overall decreasing trend in the spring SCE are captured by the CAMS-CSM, while the biased magnitudes exist. Due to the underestimation of the AMOC and the poor quantification of air–sea interaction, the CAMS-CSM overestimates regional sea ice and underestimates the observed decreasing trend in Arctic sea–ice area in September. Overall, the CAMS-CSM reproduces a climatological distribution of the Arctic climate system and general trends from 1979 to 2013 compared with the observations, but it shows limited skills in modeling local trends and interannual variability.

Lag influences of winter circulation conditions in the tropical western Pacific on South Asian summer monsoon

By means of monthly mean NCEP/NCAR data analyses, this note investigates the lag influences of winter circulation conditions in the tropical western Pacific on South Asian summer monsoon through the methods of composite, correlation and statistical confident test. The results indicate clearly that winter climate variations in the equatorial western Pacific would produce significant influences on the following South Asian summer monsoon, and with the lapse of time the lag influences show clearly moving northward and extending westward features. When winter positive (negative) sea level pressure anomalies occupy the equatorial western Pacific, there is an anticyclonic (cyclonic) circulation anomaly appearing in the northwestern Pacific. With the lapse of time, the anticyclonic (cyclonic) circulation anomaly gradually moves to northeast, and its axis in the west-east directions also stretches, therefore, easterly (westerly) anomalies in the south part of the anticyclonic (cyclonic) circulation anomaly

The leading correlation of the winter Aleutian Low with surface air temperature during the subsequent summer over the Arctic and its possible mechanism

The variations of surface air temperature(SAT)over the Arctic are closely related to global climate change.Based on reanalysis datasets and a newly defined Aleutian Low intensity index,we found a good correlation between intensity of winter Aleutian Low and the SAT over the Arctic during the subsequent summer.Explanations were given using correlation analysis,composite analysis,and singular value decomposition methods.When intensity of winter Aleutian Low was weaker,sea surface temperature appeared higher in the North Pacific in the subsequent spring and summer,resulting in mean meridional circulation anomalies and 500 hPa geopotential height anomalies in spring and summer.Anomalous upward motion in mid-latitudes and downward motion in high latitudes(Ferrel cell weakening)transported the warmer air to the north from lower layer to the upper layer followed by increases in the SAT over the Arctic.Anomalous downward motion over about 75°N also caused consequent adiabatic warming and contributed to inhibit the heat transportation from surface to upper layer.Negative 500 hPa geopotential height anomalies existed in mid-latitudes and positive anomalies existed in high latitudes.The pattern(low-in-south and high-in-north)benefited from increasing the inflow volume flux of the Bering Strait,which also made the SAT over the Arctic increase.The results of this study reveal the process that the summer SAT over the Arctic was modulated by interannual variability of intensity of winter Aleutian Low.