THE CHARACTERISTICS OF 500 hPa GEOPOTENTIAL AND SST FIELD OF EXTREMELY SEVERE COLD MONTHS IN SOUTH CHINA WINTER

The region of south China is sometimes subject to major climatic catastrophes in winter. To have a clear understanding, the time in which extremely severe cold months occur in the south China wintertime over the past 45 years are determined and characteristics of the 500-hPa geopotential fields and SST fields are studied for the simultaneous and preceding 6-month periods. Similarity exists in the 500-hPa geopotential fields between each current severely cold month, with the geopotential pattern of being high in the north, but low in the south, of Asian-Pacific region and meridional circulation developing. The work presents anomalies of the months with significant differences in the 500-hPa geopotential field of the previous periods. The SSTA is continuous in the distribution from each extremely severe cold winter month back to the 6 months leading up to it for the region of south China while the SST pattern is of El Ni?o in January and the preceding 1 ~ 6 months for equatorial eastern Pacific but of La Ni?a in February and December. It is concluded that the prediction of severely cold winter months are possible with the use of the geopotential field at 500 hPa and the SST fields for the months ahead of the target time.

THE CHARACTERISTICS OF GENERAL CIRCULATION, POLAR ICE AND SNOW DAYS / COVER OF EXTREMELY SEVERE COLD MONTHS IN SOUTH CHINA WINTER

The work has made a statistic study of the variations of extremely severe cold winter months in the south of China and general circulation and external forcing factors in preceding periods. The result shows that from the current month to the preceding March the subtropical high in the west Pacific is persistently weak or located more to the east and south. When the summer monsoon is weak in East Asia in the year before, the winter monsoon will be strong in the current year in which the extremely severe cold month occurs. The Asian polar vortex expands in the preceding July, August and September and the current winter. The Tibetan Plateau has fewer days of snow cover in the November and December before the cold month occurs. There is less snow in the Tibetan Plateau in the preceding winter / spring of each extremely severe cold month. There are more polar ice in the polar Region Ⅳ for the 11 months before the current February, especially the previous March through August, and in Region Ⅱin January ~ November before the current cold month of December but less ice in Region Ⅲ in March ~ August.

Risk factors of posttraumatic cerebral infarction in patients with severe and extremely severe head injury

Objective To explore pathogenesis and risk factors for posttraumatic cerebral infarction (PTCI) in patients with severe and extremely severe head injuries for the purpose of providing clues for reducing occurrence of PTCI and case-fatality. Methods Gender,age,Glasgow coma scale (GCS) ,the presence or absence of basicranial fracture,cerebral hernia or infection,surgical modality,hypotension,and the use of diuretics

Differences and similarities between extremely severe oligozoospermia and cryptozoospermia in intracytoplasmic sperm injection

Patients with extremely severe oligozoospermia （ESO） and cryptozoospermia （CO） are suitable using intracytoplasmic sperm injection （ICSI） as an infertility treatment. However, some andrologists are confused to distinguish ESO and CO in clinic diagnose. This study was designed for the first time to evaluate and compare patients with ESO and CO to determine whether these are useful clinical distinctions. A total of 270 infertile men in our center were classified into four groups as Group nonobstruction azoospermia （NOA, n = 44）, Group ESO （n = 78）, Group CO （n = 40）, and Group obstruction azoospermia （OA, n = 108）. Comparisons of the volume of bilateral testes, the level of follicle stimulating hormone （FSH） and inhibin B were obtained in four groups. Then comparisons of fertilization rates, cleavage rate, and excellent embryos rate were obtained when couples performed ICSh All indexes （volume of bilateral testis, level of FSH and inhibin B） in Groups ESO and CO were no difference, while Groups OA versus NOA, OA versus ESO, and OA versus CO were significant differences （P 〈 0.05）. The rates of fertilization were no differences in Groups ESO and CO while Groups OA versus ESO, OA versus CO were significant differences （P 〈 0.05）. Therefore, the spermatogenic functions in patients with CO and ESO were similar, better than NOA but worse than OA. However, it would be helpful to evaluate their spermatogenesis using testicular biopsies, especially accompanied azoospermia in clinical practice.

Features of the Extremely Severe Drought in the East of Southwest China and Anomalies of Atmospheric Circulation in Summer 2006

The spatial-temporal features of the extremely severe drought and the anomalous atmospheric circulation in summer 2006 are analyzed based on the NCEP/NCAR reanalysis data,the characteristic circulation indices given by the National Climate Center of China,and the daily precipitation data of 20 stations in the east of Southwest China（ESC） from 1959 to 2006.The results show that the rainless period started from early June and ended in early September 2006 with a total of more than 80 days,and the rainfall was especially scarce from around 25 July to 5 September 2006.Precipitation for each month was less than normal,and analysis of the precipitation indices shows that the summer precipitation in 2006 was the least since 1959.The extremely severe drought in the ESC in summer 2006 was closely related to the persistent anomalies of the atmospheric circulation in the same period,i.e.,anomalies of mid-high latitude atmospheric circulation,western Pacific subtropical high（WPSH）,westerlies,South Asian high,lower-level flow,water vapor transport,vertical motion,and so on.Droughts usually occur when the WPSH lies anomalously northward and westward,or anomalously weak and eastward.The extreme drought in summer 2006 was caused by the former.When the WPSH turned stronger and shifted to the north and west of its normal position,and the South Asian high was also strong and lay eastward,downdrafts prevailed over the ESC and suppressed the water vapor transfer toward this area.At the same time,the disposition of the westerlies and the mid-high latitude circulation disfavored the southward invasion of cold air,which jointly resulted in the extremely severe drought in the ESC in summer 2006.The weak heating over the Tibetan Plateau and vigorous convective activities over the Philippine area were likely responsible for the strong WPSH and its northwestward shift in summer 2006.

Comparative Analysis of Climate Characteristics of Extremely Short-Time Severe Precipitation in Guizhou Based on Two Types of Rainfall Data

In order to fill the gaps of the research on the data of automatic weather stations(referred to as automatic stations)not used for the climate characteristics of extremely short-time severe precipitation in Guizhou Province,the climate characteristics of extremely short-time severe precipitation in Guizhou Province were compared and analyzed based on the hourly precipitation data of the automatic stations and the national weather stations(referred to as the national stations)from April to September during 2010-2019.The results show that the average state of maximum hourly precipitation of all stations(the automatic stations and the national stations)and national stations both are representative,but the data of all stations are more representative when the maximum hourly precipitation is extreme.The 99.5 th quantile is the most reasonable threshold of extremely short-time severe precipitation in each station.The spatial distribution of extremely short-time severe precipitation intensity in all stations and national stations is generally that the southern region is stronger than the northern region,and the intensity values are concentrated in the range of 40-50 mm/h.All stations data can better reflect the distribution characteristics of<40 and≥50 mm/h.The national stations data underestimates the precipitation intensity in the southern and northeastern marginal areas of Guizhou,and slightly exaggerates the precipitation intensity in the northern part of Guizhou.The monthly and diurnal variations of the frequency of extremely short-time severe precipitation in all stations and national stations are very obvious and the variation trend is the same,but the intensity of extremely short-time severe precipitation has no obvious monthly variation characteristics.There is no significant diurnal variation in the intensity of extremely short-time severe precipitation in all stations,but the diurnal variation in the data of national stations is significant.Since the frequency of extremely short-time severe precipitation in national stations is less,the diurnal variation in the intensity of extremely short-time severe precipitation in all stations is more statistically significant.

Drivers of the Severity of the Extreme Hot Summer of 2015 in Western China

Western China experienced an extreme hot summer in 2015,breaking a number of temperature records.The summer mean surface air temperature(SAT)anomaly was twice the interannual variability.The hottest daytime temperature(TXx)and warmest night-time temperature(TNx)were the highest in China since 1964.This extreme hot summer occurred in the context of steadily increasing temperatures in recent decades.We carried out a set of experiments to evaluate the extent to which the changes in sea surface temperature(SST)/sea ice extent(SIE)and anthropogenic forcing drove the severity of the extreme summer of 2015 in western China.Our results indicate that about 65%–72% of the observed changes in the seasonal mean SAT and the daily maximumand daily minimum(Tmin)temperatures over western China resulted from changes in boundary forcings,including the SST/SIE and anthropogenic forcing.For the relative role of individual forcing,the direct impact of changes in anthropogenic forcing explain about 42% of the SAT warming and 60%(40%)of the increase in TNxand Tmin(TXxand Tmax)in the model response.The changes in SST/SIE contributed to the remaining surface warming and the increase in hot extremes,which are mainly the result of changes in the SST over the Pacific Ocean,where a super El Ni?o event occurred.Our study indicates a prominent role for the direct impact of anthropogenic forcing in the severity of the extreme hot summer in western China in 2015,although the changes in SST/SIE,as well as the internal variability of the atmosphere,also made a contribution.