Abrupt change of winter temperature over the Mongolian Plateau during 1961-2017

Studying the abrupt change of winter temperature(ACWT)over the Mongolian Plateau(MP,including Inner Mongolia Autonomous Region and State of Mongolia)is of great significance for understanding the spatiotemporal distribution of temperature and the mechanism of global climate change.Monthly temperature data during 1961–2017was collected,and the abrupt change point was determined by the Mann–Kendall test and sliding ttest,to analyze the characteristics and causes of ACWT.The results showed that(a)The winter temperature has rapidly increased with a trend of 0.41℃/10a,which was significantly higher than that of the rest area of Chinese mainland,indicating that climate change in the MP was more sensitive to global warming.(b)The abrupt change point occurred in 1988,with temperature of-15.5℃and-14.1℃before and after abrupt change,respectively.The ACWT in 50°N was 1–3 years later than that in 40°N,and the isotherms of different temperatures moved northward by 10–200 km,especially-16℃isotherms moved approximately 200 km northward after 1988.(c)The Arctic Oscillation(AO)and Mongolian High(MH)anomaly affects winter temperature over the MP.When the AO is unusually strong,the MH and East Asian winter monsoon are weak,and southerly winds prevail in most regions,which is not conducive to the cold air developing southward,leading to higher winter temperature in the MP.Overwise,abnormally northerly winds prevail and temperature is low.Meanwhile,the abrupt change time of AO occurred in 1987 before winter temperature.It shows that the AO indirectly causes winter temperatures to rise by influencing the MH and is also the main driving factor of ACWT.

Placental Abruption Following Snakebites Envenomation: A Case Report and Literature Review

Background: Snakebite envenomation in pregnancy is uncommon. It can lead to a poor outcome in both the mother and the fetus. We describe our approach to envenomation in pregnancy based on the currently available evidence. Case: We reported two case of snakebite in the third trimester of pregnancy having caused placental abruption with expelling a fresh still born baby and a live baby. In both cases, consumption coagulopathy occurred. managed by polyvalent anti-snake and blood transfusion. Their investigations became normal and they were discharged of hospitalization. Conclusion: Snakebite envenomation in pregnant is a maternal and fetal emergency. Treatment must be quick and well adapted.

Unpredictable Placental Abruption: Case Series

Background: The diagnosis of placental abruption is primarily clinical, but findings from imaging, laboratory, and postpartum pathologic studies can be used to support the clinical diagnosis. In patients with classic symptoms, fetal heart rate abnormalities, intrauterine fetal demise, and/or disseminated intravascular coagulation strongly support the clinical diagnosis and indicate extensive placental separation. In a few cases, placental separation has not been recognized and was only identified upon cesarean section as an incidental finding. Objectives: To describe the clinical presentations and pregnancy outcomes of placental abruption cases that are not diagnosed before cesarean delivery, termed “unpredictable placental abruption” and also cases diagnosed before cesarean delivery, termed “predictable placental abruption”. Methods: A retrospective analysis of 100 cases of placental abruption was identified by cesarean delivery at Tu Du hospital from September 2018 to May 2019. Clinical variables were compared between the unpredictable and predictable groups. The unpredictable group consists of cases that are not diagnosed before cesarean delivery, while the predictable cases were identified placental separation before cesarean delivery. The maternal and fetal outcomes were also studied. Results: In 100 cases of placental, abruption by gross clinical examination of the placenta at the time operation revealed that, 33% were unpredictable. Placental abruption attributed to maternal complications included one case of total hysterectomy (1%) with no cases of disseminated intravascular coagulation (DIC), shock or maternal death;specifically, this case of total hysterectomy appeared with predictable one. There were two cases of stillbirths. Among the 98 live neonates, 15 cases (14.7%) experienced severe birth asphyxia resulting in eight neonatal deaths;two of which were caused by heart disease and necrotizing enterocolitis. Sixty-three neonates were delivered prematurely (61.74%), with mean gestational age of 34.64 ± 3.32 weeks. Among the 33 unpredictable cases, there were no stillbirths but 60.6% and 12.1% experienced moderate and severe asphyxia, respectively. All unpredictable cases had obvious indications of cesarean section but the basic symptoms and signs of acute placental abruption included the onset of preterm labor, unspecified intrapartum hemorrhage, hypertonic uterine contractions and fetal distress for emergency caesarian section;however there were also cases where there were no symptoms and signs. Conclusions: Unpredictable placental abruption cases—not suspected of having abruption, termed—“concealed” or “chronic” placental abruption, may have variable clinical manifestations and better pregnancy outcomes.

Abrupt Climate Change around 4 ka BP:Role of the Thermohaline Circulation as Indicated by a GCM Experiment

A great deal of palaeoenvironmental and palaeoclimatic evidence suggests that a predominant temperature drop and an aridiflcation occurred at ca. 4.0 ka BP. Palaeoclimate studies in China support this dedution. The collapse of ancient civilizations at ca. 4.0 ka BP in the Nile Valley and Mesopotamia has been attributed to climate-induced aridification. A widespread alternation of the ancient cultures was also found in China at ca. 4.0 ka BP in concert with the collapse of the civilizations in the Old World. Palaeoclimatic studies indicate that the abrupt climate change at 4.0 ka BP is one of the realizations of the cold phase in millennial scale climate oscillations, which may be related to the modulation of the Thermohaline Circulation (THC) over the Atlantic Ocean. Therefore, this study conducts a numerical experiment of a GCM with SST forcing to simulate the impact of the weakening of the THC. Results show a drop in temperature from North Europe, the northern middle East Asia, and northern East Asia and a significant reduction of precipitation in East Africa, the Middle East, the Indian Peninsula, and the Yellow River Valley. This seems to support the idea that coldness and aridification at ca. 4.0 ka BP was caused by the weakening of the THC.

Nonlinear Feature of the Abrupt Transitions between Multiple Equilibria States of an Ecosystem Model

Based on a five-variable theoretical ecosystem model, the stability of equilibrium state and the nonlinear feature of the transition between a grassland state and a desert state are investigated. The approach of the conditional nonlinear optimal perturbations （CNOPs）, which are the nonlinear generalization of the linear singular vectors （LSVs）, is adopted. The numerical results indicate that the linearly stable grassland and desert states are nonlinearly unstable to large enough initial perturbations on the condition that the moisture index # satisfies 0.3126 〈 μ 〈 0.3504. The perturbations represent some kind of anthropogenic influence and natural factors. The results obtained by CNOPs, LSVs and Lyapunov vectors （LVs） are compared to analyze the nonlinear feature of the transition between the grassland state and the desert state. Besides this, it is shown that the five-variable model is superior to the three-variable model in providing more visible signals when the transitions occur.

Abrupt Climate Changes of Holocene

This paper is a review of studies of abrupt climate changes(ACCs) during the Holocene published during the past ten years.North Atlantic cold events are indicators of ACCs.As indicated by North Atlantic ice-rafted debris(IRD),there were nine confirmed cold events during the Holocene,occurring at 11.1 kyr,10.3 kyr,9.4 kyr,8.1 kyr,5.9 kyr,4.2 kyr,2.8 kyr,1.4 kyr,and 0.4 kyr respectively according to most representative results from Bond et al.(1997).However,the identification of chronology has been made with some uncertainties.Considerable climatic proxy data have shown that,during the cold events,substantial climate abnormalities have occurred widely across the globe,particularly in the areas surrounding the North Atlantic.These abnormalities were in the form of high-latitude cold in the both hemispheres,expansion of the Westerlies to low latitudes,drought in the monsoon regions,recession of summer monsoons,and intensification of the winter monsoons.Studies have indicated that the four ACCs occurring in the early Holocene may be related to freshwater pulses from ice melting in the northern part of the North Atlantic,and the other five ACCs that occurred during the middle and late Holocene may be related to the decreased solar activity.

Abrupt temperature change and a warming hiatus from 1951 to 2014 in Inner Mongolia, China

An abrupt temperature change and a warming hiatus have strongly influenced the global climate.This study focused on these changes in Inner Mongolia, China. This study used the central clustering method, Mann-Kendall mutation test and other methods to explore the abrupt temperature change and warming hiatus in three different temperature zones of the study region based on average annual data series.Among the temperature metrics investigated, average minimum temperature(Tnav) shifted the earliest,followed by average temperature(Tnv) and average maximum temperature(Txav). The latest change was observed in summer(1990 s), whereas the earliest was observed in winter(1970 s). Before and after the abrupt temperature change, Tnav fluctuated considerably, whereas there was only a slight change in Txav.Before and after the abrupt temperature change, the winter temperature changed more dramatically than the summer temperature. Before the abrupt temperature change, Tnav in the central region(0.322°C/10 a)and west region(0.48°C/10 a) contributed the most to the increasing temperatures. After the abrupt temperature change, Tnav in winter in the central region(0.519°C/10 a) and in autumn in the west region(0.729°C/10 a) contributed the most to the temperature increases. Overall, in the years in which temperature shifts occurred early, a warming hiatus also appeared early. The three temperature metrics in spring(1991)in the east region were the first to exhibit a warming hiatus. In the east region, Txav displayed the lowest rate of increase(0.412°C/a) in the period after the abrupt temperature change and before the warming hiatus,and the highest rate of increase after the warming hiatus.

RESEARCH ON DISTURBED MECHANISM OF THERMAL NOISES OF THE SURFACE IN ABRUPT GEOTHERMAL ANOMALY

Geothermal anomaly as a physical phenomenon of an active and latent volca nic area would be well recog-nized,and abrupt geothermal anomaly should also be understood.However,in practical work,thermal infrare d remote sensing techniques are frequently u sed to monitor geothermal flows of th e earth.But then,except for this typ e of thermal source in the surface thermal field,there still exist a lot of noises in th e area where the abrupt geothermal an omaly is generat-ed.By Analyzing the reason,we find t hat it is brought about by the non-bou ndless projection characteristics of objects.These noises may be divided into two c lasses:system noises and random noises.If disturbed noises have comparative sta-ble time sequence law and space sequence law,the noises are called system noises.And because system noises have a certain law,it is easy to remove the n oises.On the contrary,if disturbed noises have not law of time sequence a nd space sequence,the noises are called random noises.The random noises have the character of non-linearity,uncertainty and indeterminism.For this case,this p aper discusses the disturbed mechan ism of these noises as well as how to re move them..

Trends and abrupt changes in surface vapor content over Tarim Basin during the last 50 years

The surface vapor content has a close correlation with the generation of precipitation. Based on the atmospheric circulation data and surface vapor content data from 37 weather stations across the Tarim Basin dur- ing 1961-2010, the paper analyzed the vapor variation trend, period, abrupt changes and their causes. The results show that the increase trend of surface vapor content over the Tarim Basin mostly conforms with the average trend coefficient of 0.48. There were 3 centers displaying a trend of high vapor increase and 3 centers displaying a low vapor increase. These centers were distributed in strips and blocks across the basin from northeast to southwest. Notable inter-decadal variations in annual and seasonal vapor contents occurred in the Tarim Basin during the 50 years of the study period, with more vapor after the mid-1980s and less vapor in the 1960s and the 1970s. The significant increase in vapor content in the 50 year period occurred mostly in the 1980s and the 1990s. The in- creasing trend across the four seasons was strongest in summer, reaching 0.43, and weakest in spring. Great variations existed between the spring trend and the annual, summer, autumn and winter trends. During the 50-year study period, there are distinguishable periods of 4-6 years and 8-10 years in which the annual and seasonal vapor contents varied alternately between low and high concentrations. The annual vapor content and that of the four individual seasons all changed abruptly in about the mid-1980s （a〈0.05）. The west wind circulation, Tibetan Plateau circulation and the annual mean temperatures of the Tarim Basin are the main factors that influenced the surface vapor content over the study area, of which the Tibetan Plateau circulation may be the most important one.

Detection and attribution of abrupt climate changes in the last one hundred years

Based on physical backgrounds, the four time series of the Guliya （Tibetan plateau） ice core （GIC） 5180, and three natural factors, i.e. the rotation rate of earth, sunspots, and E1 Nino-Southern Oscillation （ENSO） signals, are decomposed into two hierarchies, i.e. more and less than 10-year hierarchies respectively, and then the running t-test is used to reanalyse the data before and after filtering with the purpose of investigating the contribution of natural factors to the abrupt climate changes in the last one hundred years. The results show that the GIC 5180 evolved with a quasi-period of 7-9 years, and the abrupt climate changes in the early 1960s and in the period from the end of the 1970s to the beginning of the 1980s resulted from the joint effect of the two hierarchies, in other words, the two interdecadal abrupt changes of climate in the last one hundred years were global. The interannual variations of ENSO and sunspots were the important triggering factors for the abrupt climate changes in the last one hundred years. At the same time, the method of Information Transfer （IT） is employed to estimate the contributions of ENSO signals and sunspots activities to the abrupt climate changes, and it is found that the contribution of the interannual variation of ENSO signals is relatively large.

Abrupt changes of radiolarian fauna at 600 and 120 ka B. P. in the southern South China Sea and their paleoceanographic implications

Abrupt changes in radiolarian composition are discovered over the last 600 and 120 ka B. P. based on quantitative analyses of radiolarians in ~ 17957 - 2 of the southern South China Sea. The distinct changes at 600 ka B. P. could correspond to the onset of the 100 ka cycle during the glacial and interglacial periods. This abrupt change in the 100 ka cyclicity at 600 ka B. P. occurred also in the magnetic susceptibility signal that is obtained from and paleosol sequences of the China Loss Plateau. The larger amplitude and stronger cyclicity in the susceptibility signal after 600 ka B. P. reflect the prominent change in the intensity of the monsoon, induced by an enhancement of the momsoon circula- tion. Stronger seasonality during the glacial period in the South China Sea, resulted from strengthening of winter monsoon, might lead to the changes in the radiolarian composition at 600 and 120 ka B. P. It can be suggested that only species adapted to a broader temperature range might have been able to live in this environment. Therefore, the abrupt changes in radiolarian composition at 600 and 120 ka B. P. could be attributed to the stronger so differences between summer and winter that were caused by the striking change in the intensity of the monsoon circulation.

Holocene Abrupt Climate Shifts and Mid-Holocene Drought Intervals Recorded in Barkol Lake of Northern Xinjiang of China

Study results in this paper have indicated that the Holocene climate in Xinjiang, Northwestem China has been alternating between wet and dry conditions, and was punctuated with a series of abrupt climate shifts. A sediment core taken from Barkol Lake in the northern Xinjiang of Northwest China was analyzed at 1 cm interval for grain-size distribution. Abrupt climate shifts revealed by the grain-size proxy occurred at ca 1.4, 3.0, 4.3, 5.6, 8.0 cal kyr B.E, which were well correlated to both the abrupt shifts recorded in the North Atlantic Ocean （NAO） and the Holocene sea surface temperature （SST） cooling events in the Arabian Ocean. The correlation indicated that the climatic changes in the extreme arid Northwest China were associated with the NAO, probably via the North Atlantic Oscillation-affected westerly winds. The strength and position of westerly winds probably modulated the Siberian-Mongolian high- pressure system （winter monsoon）, and played an important role in climate change of Northwest China. Moreover, an evident drought interval during the middle Holocene was also revealed by grain-size proxy.

Early warning signals of abrupt temperature change in different regions of China over the past 50 years

In this paper, the early warning signals of abrupt temperature change in different regions of China are investigated. Seven regions are divided on the basis of different climate temperature patterns, obtained through the rotated empirical orthogonal function, and the signal-to-noise temperature ratios for each region are then calculated. Based on the concept of critical slowing down, the temperature data that contain noise in the different regions of China are preprocessed to study the early warning signals of abrupt climate change. First, the Mann-Kendall method is used to identify the instant of abrupt climate change in the temperature data. Second, autocorrelation coefficients that can identify critical slowing down are calculated. The results show that the critical slowing down phenomenon appeared in temperature data about 5-10 years before abrupt climate change occurred, which indicates that the critical slowing down phenomenon is a possible early warning signal for abrupt climate change, and that noise has less influence on the detection results of the early warning signals. Accordingly, this demonstrates that the model is reliable in identifying the early warning signals of abrupt climate change based on detecting the critical slowing down phenomenon, which provides an experimental basis for the actual application of the method.

Comparison of performance between rescaled range analysis and rescaled variance analysis in detecting abrupt dynamic change

In the present paper, a comparison of the performance between moving cutting data-rescaled range analysis （MC- R/S） and moving cutting data-rescaled variance analysis （MC-V/S） is made. The results clearly indicate that the operating efficiency of the MC-R/S algorithm is higher than that of the MC-V/S algorithm. In our numerical test, the computer time consumed by MC-V/S is approximately 25 times that by MC-R/S for an identical window size in artificial data. Except for the difference in operating efficiency, there are no significant differences in performance between MC-R/S and MC-V/S for the abrupt dynamic change detection. Mc-R/s and MC-V/S both display some degree of anti-noise ability. However, it is important to consider the influences of strong noise on the detection results of MC-R/S and MC-V/S in practical application

STUDY ON TRANSMISSION MECHANISM OF THERMAL INFRARED REMOTE SENSING FOR ABRUPT GEOTHERMAL ANOMALY IN VOLCANIC REGION

Experiment researches have proven that there is an obvious phenomenon of abrupt geothermal anomaly in volcanic region in the forewarning period of volcano eruption, which is closely related to the geological structure, the cause, the scale and the type of volcano etc. On the other hand, this kind of geothermal anomaly is an important sign to monitor volcano activity by thermal infrared remote sensing techniques. This paper discusses the feature of abrupt geothermal anomaly, the transmission mechanism of geothermal anomaly and the radiation transmission mechanism of heat field of terrene in volcanic region. By analyzing mechanism of terrene temperature rising by way of conduction and convection of heat, we have presented the transmission equation of atmosphere for thermal infrared radiation based on the effective radiation of objects. The related problems of noise interference in the processes of transmission for thermal infrared radiation will be discussed in the later paper.

EVIDENCE FOR ABRUPT CLIMATIC CHANGES ON NORTHWESTERN MARGIN OF EAST ASIAN MONSOON REGION DURING LAST DEGLACIATION

Based on investigations of the Zhongwei Nanshan aeolian section situated in the southeastern margin of Tengger Desert, carbon-14 and TL (thermoluminescence) dating results and paleoclimatic proxies such as magnetic susceptibility and grain size, we inferred that the northwestern margin of East Asian monsoon region experienced abrupt climatic changes during the last deglaciation. Six oscillation events were identified: Oldest Dryas, Bolling, Older Dryas, Allerod, Intra-Allerod Cold Period (IACP) and Younger Dryas (YD). The summer monsoon was weaker during Oldest Dryas and Younger Dryas when the winter monsoon was stronger. However, during the B/A (Bolling/Allerod) period, the summer monsoon strengthened, reflected by magnetic susceptibility, when the winter monsoon also became strong, which is different from the paleoclimatic pattern established in the East Asian monsoon region. Furthermore, the summer monsoon was nearly in phase with the climate changes inferred from the oxygen isotopic records of Greenland ice cores. It could be speculated that the variations of the sea ice cover in the high latitudes of the North Hemisphere affected the high pressure of Asian continent and the changes of the winter monsoon inland. On the other hand, the sea ice cover variations might have indirectly caused the occurrence of ENSO events that has tightly been related to the summer monsoon in northwest margin of East Asian monsoon region.

A Typical Mode of Seasonal Circulation Transition: A Climatic View of the Abrupt Transition from Drought to Flood over the Middle and Lower Reaches of the Yangtze River Valley in the Late Spring and Early Summer of 2011

In this study, the seasonal transition of precipitation over the middle and lower reaches of the Yang-tze River Valley (YRV) from late spring to early summer is investigated. The results show that the seasonal transition of precipitation exhibits multi-modes. One of these modes is characterized by an abrupt transition from drought to flood (ATDF) over the middle and lower reaches of the YRV in the seasonal transition of precipitation. It is shown that the ATDF event from May to June 2011 is simply one prominent case of the ATDF mode. The ATDF mode exhibits an obvious decadal variability. The mode has occurred more frequently since 1979, and its amplitude has apparently strengthened since 1994. From the climatic view, the ATDF mode configures a typical seasonal circulation transition from winter to summer, for which the winter circulations are prolonged, and the summer circulations with the rainy season are built up early over the YRV.

A study of the early warning signals of abrupt change in the Pacific decadal oscillation

In recent years, the phenomenon of a critical slowing down has demonstrated its major potential in discovering whether a complex dynamic system tends to abruptly change at critical points. This research on the Pacific decadal oscillation(PDO) index has been made on the basis of the critical slowing down principle in order to analyze its early warning signal of abrupt change. The chaotic characteristics of the PDO index sequence at different times are determined by using the largest Lyapunov exponent(LLE). The relationship between the regional sea surface temperature(SST) background field and the early warning signal of the PDO abrupt change is further studied through calculating the variance of the SST in the PDO region and the spatial distribution of the autocorrelation coefficient, thereby providing the experimental foundation for the extensive application of the method of the critical slowing down phenomenon. Our results show that the phenomenon of critical slowing down, such as the increase of the variance and autocorrelation coefficient, will continue for six years before the abrupt change of the PDO index. This phenomenon of the critical slowing down can be regarded as one of the early warning signals of an abrupt change. Through calculating the LLE of the PDO index during different times, it is also found that the strongest chaotic characteristics of the system occurred between 1971 and 1975 in the early stages of an abrupt change(1976), and the system was at the stage of a critical slowing down, which proves the reliability of the early warning signal of abrupt change discovered in 1970 from the mechanism. In addition, the variance of the SST,along with the spatial distribution of the autocorrelation coefficient in the corresponding PDO region, also demonstrates the corresponding relationship between the change of the background field of the SST and the change of the PDO.

THE ABRUPT CHANGE OF TROPICAL CYCLONE NUMBER OVER THE WESTERN NORTH PACIFIC IN THE MID-1990s

Based on the CMA tropical cyclone(TC) best track data as well as the reanalysis datasets from the NCEP/NCAR and NOAA, the variation characteristics of TC number from 1949 to 2013 over the western North Pacific(including the South China Sea) are examined. Notably, the time series of TC number exhibits a significant abrupt change from more to less around 1995. Comparative analysis indicates that the environmental factors necessary to TC formation also change significantly around the mid-1990 s. After 1995, accompanying with anomalous warm sea surface temperature(SST) in western equatorial Pacific, a La Nia-like pattern in tropical Pacific appears obviously. However,compared with the period before 1995, the vertical upward movement decreases, vertical shear of tropospheric zonal wind increases, and sea level pressure(SLP) rises, all of which are unfavorable to TC formation and work together to make TC number reduce markedly after 1995. Furthermore, when the typical interannual more and less TCs years are selected in the two separate stages before and after 1995, the relative importance of oceanic and atmospheric environments in interannual TC generation is also investigated respectively. The results imply that the SST over the tropical Pacific exerts relatively important influence on TC formation before 1995 whereas the atmospheric circulation plays a more prominent role in the generation of TC after 1995.

Study on the Influence of Abrupt Climate Variation on the Vegetation Based on NDVI

[Objective] The research aimed to study the influence of abrupt climate variation on the vegetation based on NDVI. [Method] Based on NDVI and climate data in China during 1982-2000, by using Mann-kendall (MK) abrupt change detection method, the abrupt variations of climate and NDVI were detected. Then, the relationship between two kinds of abrupt variations was discussed. [Result] The large-area abrupt variations of monthly average temperature and rainfall happened in 1983, and the occurrence range in 1999 was the smallest. The large-area abrupt variation phenomenon of vegetation appeared in 1983 and 1984. The occurrence times of NDVI abrupt variation phenomenon which was induced by the abrupt variation of temperature was more than that of precipitation. The abrupt variation of rainfall wasn’t one of main reasons for the occurrence of NDVI abrupt variation phenomenon. The small-area abrupt variation of temperature was difficult to generate the immediate influence on the vegetation activity in the short time. The abrupt variation phenomenon of large-scale temperature would generate the long-term influence on the vegetation activity. [Conclusion] The research provided the theory basis for analyzing the abrupt variation phenomenon of climate.