Contribution of Global Warming and Atmospheric Circulation to the Hottest Spring in Eastern China in 2018

The spring of 2018 was the hottest on record since 1951 over eastern China based on station observations,being 2.5°C higher than the 1961−90 mean and with more than 900 stations reaching the record spring mean temperature.This event exerted serious impacts in the region on agriculture,plant phenology,electricity transmission systems,and human health.In this paper,the contributions of human-induced climate change and anomalous anticyclonic circulation to this event are investigated using the newly homogenized observations and updated Met Office Hadley Centre system for attribution of extreme events,as well as CanESM2(Second Generation Canadian Earth System Model)simulations.Results indicate that both anthropogenic influences and anomalous anticyclonic circulation played significant roles in increasing the probability of the 2018 hottest spring.Quantitative estimates of the probability ratio show that anthropogenic forcing may have increased the chance of this event by ten-fold,while the anomalous circulation increased it by approximately two-fold.The persistent anomalous anticyclonic circulation located on the north side of China blocked the air with lower temperature from high latitudes into eastern China.Without anthropogenic forcing or without the anomalous circulation in northern China,the occurrence probability of the extreme warm spring is significantly reduced.

Effects of topography on the sub-tidal circulation in the southwestern Huanghai Sea(Yellow Sea)in summer

A nested circulation model system based on the Princeton ocean model （POM） is set up to simulate the currentmeter data from a bottom-mounted Acoustic Doppler Profiler （ADP） deployed at the 30 m depth in the Lunan（South Shandong Province, China） Trough south of the Shandong Peninsula in the summer of 2008, and to study the dynamics of the circulation in the southwestern Huanghai Sea （Yellow Sea）. The model has reproduced well the observed subtidal current at the mooring site. The results of the model simulation suggest that the bottom topography has strong steering effects on the regional circulation in summer. The model simulation shows that the Subei （North Jiangsu Province, China）coastal current flows north- ward in summer, in contrast to the southeastward current in the center of the Lunan Trough measured by the moored currentmeter. The analyses of the model results suggest that the southeastward current at the mooring site in the Lunan Trough is forced by the westward wind-driven current along the Lunan coast, which meets the northward Subei coastal current at the head of the Haizhou Bay to flow along an offshore path in the southeastward direction in the Lunan Trough. Analysis suggests that the Subei coastal current, the Lunan coastal current, and the circulation in the Lunan Trough are independent current systems con- trolled by different dynamics. Therefore, the current measurements in the Lunan Trough cannot be used to represent the Subei coastal current in general.

Effects of anthropogenic forcing and atmospheric circulation on the record-breaking welt bulb heat event over southern China in September 2021

In September 2021,southern China witnessed an extreme high-temperature and high-humidity event.The average regional wet bulb globe temperature(WBGT)anomaly(relative to 1961-1990 mean)in 110.0°-120.0°E,27.5°-32.5°N region was the highest on record at 3.28°C and exceeded three times the observed standard deviation.To investigate the underlying causes,we examine the effects of anthropogenic forcings and anomalous circulation patterns on this event using the multi-model ensembles from the Coupled Model Intercomparison Project Phase 6.Results indicate that 2021-like events would happen extremely rarely without anthropogenic warming(would not occur in counterfactual world simulations)and have become a 1-in-16-year event in the factual world.For the threshold of the second most extreme year,the occurrence probability of extreme WBGT events increases approximately 50 times due to the impact of anthropogenic forcings.The effect of anthropogenic warming under similar atmosphere circulation increases the probability of extreme WBGT events by 13-60 times,and that of corresponding circulation patterns under the same anthropogenic warming increases the probability by 1.3-1.8 times.

NUMERICAL SIMULATIONS OF HEATING ANOMALY EFFECTS OF TIBETAN PLATEAU ON CIRCULATION IN SUMMER

A 5-layer numerical model with p-σ incorporated coordinate system and primitive equations is used to simulate the effects of heating anomaly at and over the Tibetan(Qinghai-Xizang)Plateau on the circulations in East Asia in sum- mer,The model is described briefly in the text and the results are analysed in somewhat detail.Results show that the sur- face albedo,the drag coefficient,the evaporation rate and the ground temperature all have large influences on the circula- tion near the Plateau and in East Asia.When the heating at the surface increases,the Tibetan high in the upper troposphere intensifies,too.Its area enlarges and its axis tilts to northwest.The upper tropical easterly increase and shifts to north.The southwesterly in the lower troposphere,in consistence,also increases.The cross-equatorial low-lev- el currents along Somali and South India are influenced to increase their speeds while those over North Australia de- crease.The land low over the Asian Continent deepens.Meanwhile the upward motions over the land of east China and over the Indo-China Peninsula intensify and therefore the precipitation over those areas increases.However,along the coastal area of China the upward motions and therefore the precipitation decrease. Atmospheric heat source anomaly has large influence on the circulation,too.Simulated results indicate that heat source anomaly in the lower atmosphere over the Plateau influences the intensity and the position of the monsoon circu- lation while that in the upper atmosphere only affects the intensity.The heating status over the Plateau has slight influ- ence on the westerly jet,north of the Plateau,while it has strong effect on the subtropical jet at the mid and low latitudes.

Effect of Removing Toxic Substances Combined with Activating Blood Circulation on Stabilizing the Atherosclerotic Plaque and Unstable Angina

The therapeutic effects of activating blood circulation to remove stasis of Chinese medicine （CM） in the prevention and treatment of atherosclerotic diseases such as coronary artery disease and angina are generally acknowledged. In recent years, to further improve the therapeutic effects of those Chinese herbs on such diseases, we have carried out a series of studies of CM medications with the function of clearing heat and removing toxic substances combined with activating blood circulation to remove stasis.

Effect of opening the Drake Passage on the oceanic general circulation:A box model study

The impacts of opening the Drake Passage(DP) on the oceanic general circulation are examined.When the DP is open,wind stress at mid-and high latitudes gives rise to a wind-driven gyre,which induces a meridional heat exchange between mid-and high latitudes in the Southern Ocean.After the opening of the DP,the Antarctic Circumpolar Current(ACC) forms and its associated strong temperature front blocks the heat transport from mid-latitudes to high latitudes.A simple box model is formulated,in which the effects of the wind stress(for the case of DP closed) and the thermal front(for the case of DP open) on the variability of Antarctic Bottom Water(AABW) and North Atlantic Deep Water(NADW) are explored.The sensitivity experiments demonstrate that:(1) When the DP is closed,the enhancement of the wind-driven gyre leads to the decline of AABW formation in the Southern Ocean and the increase of NADW formation in the North Atlantic.As a result,water in high latitudes of the Southern Ocean becomes warmer,so does the bottom water of global ocean.(2) When the DP is open,there is no formation of AABW until the intensity of thermal front along ACC exceeds a threshold value(it is 4.03℃ in our model).Before the formation of AABW,temperature in most of the oceans is higher than that after the formation of AABW,which usually leads to the cooling of high latitudes of the Southern Hemisphere and the bottom water in global ocean.When the strength of the thermal front is lower than the critical value,there is no AABW formation,and temperature in most of the oceans is slightly higher.These results demonstrate that during the opening of the DP,changes in wind stress and the formation of the thermal front in the Southern Ocean can substantially affect the formation of AABW and NADW,thus changing the state of meridional overturning circulation in the global ocean.

EFFECT OF PLANETARY AND SYNOPTIC SCALE WAVES IN MAINTAINING MERIDIONAL CIRCULATIONS AT MID AND LOW LATITUDES

Following Wu and Chen(1989), in terms of the elliptical differential equation with mean meridional stream function, an equation similar in form to that developed by Kuo (1956) and by use of time average statistics of atmospheric circulation in wavenumber domains at the same intervals of time, a study is made of the con- tribution of the internal forcing of the atmosphere in two space scales to mean meridional circulation. Re- sults show that planetary waves have considerable influence on the intensity of the upper center of the bi- Hadley cell, and, in contrast, synoptic-scale waves exert vital effect on the Ferrel cell, and that in the Northern Hamisphere(NH)such internal forcings by planetary- and synoptic-scale waves are comparable on mean merid- ional circulations whereas the latter contribute far more than the former in the Southern Hemisphere (SH). Further, in the northern winter (summer)the contribution of heat (angular momentum) transport of planetary waves allows the descending (ascending) branch to occur as far as around 40°N, some kind of effect that makes quite important contribution to the winter (summer) monsoon circulation in eastern Asia.

EFFECT OF THE THERMAL FORCING ON THE SECONDARY CIRCULATION OF TYPHOONS

A non-dimensional secondary circulation equation for typhoons has been derived and then 11-yr com- positing typhoon data were used to estimate the thermally forced secondary circulation.The main results have been obtained as follows: (1)The diabatic heating and Cu vertical heat mixing are major thermal forcing factors.They have the same magnitude of order.(2)The effects of eddy flux and Cu horizontal mixing of heat are of minor im- portance.(3)Ekman pumping and Cu vertical heat mixing cooperatively work.This feedback process is favorable for the enhancement of the secondary circulation of typhoons.

AN EXPERIMENTAL SIMULATION ON THE MECHANICAL EFFECT OF TIBETAN PLATEAU ON ZONAL CIRCULATION OF STRATIFIED ATMOSPHERE

The present work is intended to simulate, in a rotating annulus of stratified liquid, the me-chanical effect of the Xizang (Tibetan) Plateau on the zonal circulation. The main featuresof three flow patterns around the plateau for different Rossby number R and rotating Eulernumber E are analysed. and a division diagram of the flow pattern in (R, E) plane is given.It has been found that under the condition that similarity criterions R and E of the experimentalfluid are the same as those existing in the atmosphere for monthly mean states in spring, au-tumn and winter months, the experimental results are satisfied for the following weathersystems over the plateau and its vicinities: the low vortex, trough and shear line over thesoutheast part of the plateau, the tilted ridge over the northwest part of the plateau, the troughpatterns over the upstream and dewnstream of the plateau, the vertical circulation structure, thejets on both north and southeast sides of the plateau, and so on. This shows that the mechanicaleffect of the Tibetan Plateau on the general circulation over East Asia deserves close atten-tion.

EFFECTS OF THREE-DIMENSIONAL STRUCTURE OF HEATING FIELD ON THE SUMMER MONSOON CIRCULATION IN ASIA

In this paper,a primitive equation linear wave model is used to examine the effects of three-dimen- sional structure of heating field on the behavior of stationary planetary waves in summer and to compare the roles of different heating functions for the formation and maintenance of summer monsoon circulation in Asia.It is shown that the aloft heating connected with the latent heating,especially the deep condensation heating associated with the cumulus convection in low latitudes,plays a crucial part in the Asian summer mon- soon and the structures of planetary wave responses are quite sensitive to the vertical distribution of heating.

Dynamics of local extreme rainfall of super Typhoon Soudelor (2015) in East China

The characteristics and dynamics associated with the distribution, intensity, and triggering factors of local severe precipitation in Zhejiang Province induced by Super Typhoon Soudelor(2015) were investigated using mesoscale surface observations, radar reflectivity, satellite nephograms, and the final(FNL) analyses of the Global Forecasting System(GFS) of the National Center for Environmental Prediction(NCEP). The rainfall processes during Soudelor's landfall and translation over East China could be separated into four stages based on rainfall characteristics such as distribution, intensity, and corresponding dynamics. The relatively less precipitation in the first stage resulted from interaction between the easterly wind to the north flank of this tropical cyclone(TC) and the coastal topography along the southeast of Zhejiang Province, China. With landfall of the TC in East China during the second stage, precipitation maxima occurred because of interaction between the TC's principal rainbands and the local topography from northeastern Fujian Province to southwestern Zhejiang Province. The distribution of precipitation presented significant asymmetric features in the third stage with maximal rainfall bands in the northeast quadrant of the TC when Soudelor's track turned from westward to northward as the TC decayed rapidly. Finally, during the northward to northeastward translation of the TC in the fourth stage, the interaction between a mid-latitude weather system and the northern part of the TC resulted in transfer of the maximum rainfall from the north of Zhejiang Province to the north of Jiangsu Province,which represented the end of rainfall in Zhejiang Province. Further quantitative calculations of the rainfall rate induced by the interaction between local topography and TC circulation(defined as "orographic effects") in the context of a one-dimensional simplified model showed that orographic effects were the primary factor determining the intensity of precipitation in this case,and accounted for over 50% of the total precipitation. The asymmetric distribution of the TC's rainbands was closely related to the asymmetric distribution of moisture resulted from changes of the TC's structure, and led to asymmetric distribution of local intense precipitation induced by Soudelor. Based on analysis of this TC, it could be concluded that local severe rainfall in the coastal regions of East China is closely related to changes of TC structure and intensity, as well as the outer rainbands. In addition, precipitation intensity and duration will increase correspondingly because of the complex interactions between the TC and local topography, and the particular TC track along large-scale steering flow. The results of this study may be useful for the understanding, prediction, and warning of disasters induced by local extreme rainfall caused by TCs, especially for facilitating forecasting and warning of flooding and mudslides associated with torrential rain caused by interactions between landfalling TCs and coastal topography.