NEW DEFINITION FOR NORTH HUAIHE RIVER RAINY SEASON AND ATMOSPHERIC CIRCULATION CHARACTERISTICS IN PRECIPITATION ANOMALY YEARS

In this article, a new definition for the North Huaihe River rainy season (NHRS) is presented using summer daily precipitation in East China and subtropical high ridge axis at 500 hPa. By calculating the annual precipitation amounts in the NHRS and Meiyu of the Yangtze-Huaihe Rivers basin (YHMY) from 1961 to 2009, the dates of precipitation beginning and ending as well as the duration of the two rainy seasons in the 49 years are analyzed. Atmospheric circulation characteristics in positive and negative precipitation anomaly years during the NHRS are also studied. Results are shown as follows. (1) The new definition for the NHRS is much easier to use. It involves only two meteorological factors, making its application more practical. It can also distinguish two rainy periods of the NHRS more objectively. (2) The average duration of the NHRS is similar to that of the YHMY, except that its average dates of beginning and ending are about one week later than those of the YHMY. The average precipitation of the NHRS is slightly less than that of the YHMY, and the yearly precipitation variation of the two rainy seasons are similar to each other with no obvious increasing or decreasing trend in the 49 years, but with distinguished decadal and inter-annual variations. (3) In positive precipitation anomaly years, the South Asian high moves more northward and more eastward, the western Pacific subtropical high is located more northward and westward, and the summer monsoon is stronger than normal, resulting in the convergence of the warm and moist southwesterly airflow from the west side of the subtropical high and the cold air from the north side of the northeast trough in North Huaihe River basin.

The Kinetic Energy Budget and Circulation Characteristics of the Tropical Storm Irma during AMEX Phase Ⅱ

By using the data from observation on the Chinese research vessel Xiang Yang Hong No.5 and other sources during AMEX phase II, the kinetic energy budget and circulation characteristics of the tropical storm Irma were analyzed.Irma formed on the ITCZ of the Southern Hemisphere. During the formative stage of the storm, the SE trades and monsoon westerlies on both sides of the ITCZ strengthened, and more importantly, there was a strong divergent flow in upper troposphere. These contributed to the intensification of Irma. At the time when Irma formed, the Richardson number (Ri) in middle and lower troposphere was much smaller than that prior to and post the formation.When Irma intensified rapidly, the area-averaged kinetic energy in the general flow increased in the whole troposphere . The largest contribution came from kinetic energy generation term, -[v.(?)(?)] .indicates that there existed a strong ageostrophic accetration. As to the generation term , the conversion of available potential energy to kinetic energy, - |ωα|, made the largest contribution. This illustrates the importance of internal sources and of the ensemble effect of cumulus convection to the kinetic energy.To the increase of area-averaged eddy kinetic energy during the rapid intensification of Irma, the most impor tant source in the whole troposphere was the dissipation term - [E'], that should be interpreted as the. feeding of eddy kinetic energy from smaller to larger scale disturbances. Another important source was generation term, - [v' (?)(?)'], in the lower troposphere. Rather small contribution came from the energy conversion from the kinetic energy of area-mean flow to eddy kinetic energy. Therefore, the eddy kinetic energy of the developing tropical disturbance extracted both from smaller an, .arger scale motions. The former was much more important than the latter In addition, the disturbance acting as a generator and exporter, generated and exported eddy kinetic energy to the environmental atmosphere.

Characteristics and Mechanisms of Persistent Wet–Cold Events with Different Cold-air Paths in South China

We investigate the characteristics and mechanisms of persistent wet–cold events(PWCEs)with different types of coldair paths.Results show that the cumulative single-station frequency of the PWCEs in the western part of South China is higher than that in the eastern part.The pattern of single-station frequency of the PWCEs are“Yangtze River(YR)uniform”and“east–west inverse”.The YR uniform pattern is the dominant mode,so we focus on this pattern.The cold-air paths for PWCEs of the YR uniform pattern are divided into three types—namely,the west,northwest and north types—among which the west type accounts for the largest proportion.The differences in atmospheric circulation of the PWCEs under the three types of paths are obvious.The thermal inversion layer in the lower troposphere is favorable for precipitation during the PWCEs.The positive water vapor budget for the three types of PWCEs mainly appears at the southern boundary.

Analysis on the Gale Climate Characteristics and Circulation Situation in Jinzhou Area

Based on the gale observation data in 5 observation stations in Jinzhou area from 1973 to 2007,the gale trend and the periodic change in Jinzhou area were analyzed by using the linear trend estimation method and the spectral analysis method. Meanwhile,the circulation situation characteristics and the spatial-temporal distribution characteristics of gale in four seasons were discussed by surveying generally the weather charts. The results showed that the gale in Jinzhou area presented the fluctuation decline trend and had 3.5,7.0 years periodic changes. The gale in spring is the most and in summer was the least. It was less in winter and autumn. Seen from the analysis on the circulation situation,the gale circulation situation in Jinzhou area was similar to in Liaoning. The circulation situation in spring was basically consistent with in autumn,winter. The main situations had 3 kinds:north high south low(west high east low) ,two high clipping low,south high north low(east high west low) . In summer,the regional gale weather was mainly caused by the meso-micro scale system.

Circulations and Thermodynamic Characteristics of Different Patterns of Rainstorm Processes in the Eastern Foot of Helan Mountain

Based on the observational hourly precipitation data and the European Centre for Medium-Range Weather Forecasts(ECMWF)Reanalysis 5(ERA5)products from 2006 to 2020,22 rainstorm processes in the eastern foot of Helan Mountain are objectively classified by using the hierarchical clustering method,and the circulation characteristics of different patterns are comparatively analyzed in this study.The results show that the occurrences of rainstorm processes in the eastern foot of Helan Mountain are most closely related to three circulation patterns.PatternsⅠandⅢmainly occur in July and August,with similar zonal circulations in synoptic backgrounds.Specifically,the South Asia high and the western Pacific subtropical high are stronger and more northward than those in normal years.The frontal systems in westerlies are inactive,while the water vapor from the ocean surface in the south is mainly transported to the rainstorm area by the southerly jet stream at 700 h Pa.The dynamic lifting anomalies are relatively weak,the instability of atmospheric stratification is anomalously strong,and thus the localized severe convective rainstorm is more significant.Comparatively,rainstorm processes of patternⅠare accompanied by stronger and deeper ascending motions,and the warm-sector rainstorm is more extreme.PatternⅢshows a stronger and deeper convective instability,accompanied by larger low-level moisture.Rainstorm processes of patternⅡmainly occur in early summer and early autumn,presenting a meridional circulation pattern of high in the east and low in the west in terms of geopotential height.Moreover,the two low-level jets transporting the water vapor northward from the ocean on the east of China encounter with the frontal systems in westerlies,which makes the ascending motion in patternⅡanomalously strong and deep.The relatively weak instability of atmospheric stratification causes weak convection and long-lasting precipitation formed by the confluence of cold air and warm air.This study may help improve rainstorm forecasting in arid regions.

Climate Characteristics of High Temperature Weather in Xi'an City in Recent 59 Years

[Objective] The aim was to study the characteristics of high temperature in Xi’an City over the last 59 years. [Method] By dint of daily highest temperature in the Xi’an observatory, the climate characteristics of high temperature at different intensities and the high attitude circulation were studied by statistical method. [Result] Over the last 59 years, there were 22.95 high temperature days each year on average in Xi’an City, which occurred from the last ten days of April to the first ten days of September. Most high temperature days occurred in the last ten days of July, followed by that in the last ten days of June. There were two peak values in the last ten days of June and last ten days of July when temperature ≥38.0 ℃. For the hottest day, it occurred most in the last twenty days of June, followed by July, and rarely in August. The interannual changes in the high temperature day, hot day and hottest day showed one-little and one-much trend. It was much from 1950s to 1960s, from 1970s to 1980s and then grew more after 1990s. The annual extreme highest temperature took place in the last twenty days of June, and then in the last ten days of July. Its interannual changes showed high-low-high trend. The high temperature appeared most often in July and also lasted for the longest duration. The hot day lasted for two days. The hottest days of ≥40.0 ℃ were very rare. The circulation of high temperature generally fell into one of four categories: continental high pressure controlling type, subtropical high controlling type, strip high pressure controlling type and northwest airstream controlling type. [Conclusion] The study provided references for the forecast and pre-warning of high temperature.

CFD Investigation of the Influence of Volute Geometrical Variations on Hydrodynamic Characteristics of Circulator Pump

Improper design of volute geometry can be the main cause that leads to unsteady pressure pulsation and radial force in pumps. Therefore, it is important to understand the influence of volute geometrical parameters on hydrodynamic characteristics of pump and the mechanism. However, the existing studies are limited to investigate the influence of only one or two volute geometrical parameters each time, and a systematic study of the influence of the combinations of different volute geometrical parameters on the pump＇s hydrodynamic characteristics is missing. In this paper, a study on the understanding of the influence of volute geometrical variations on hydrodynamic characteristics of a high speed circulator pump by using computational fluid dynamics（CFD） technology is presented. Five main volute geometrical parameters D3, A8, a0, j0 and Rt are selected and 25 different volute configurations are generated by using design of experiments（DOE） method. The 3D unsteady flow numerical simulations, which are based on the SST k-w turbulence model and sliding mesh technique provided by CFX, are executed on the 25 different volute configurations. The hydraulic performance, pressure pulsation and unsteady radial force inside the pump at design condition are obtained and analyzed. It has been found that volute geometrical parameters D3 and A8 are major influence factors on hydrodynamic characteristics of the pump, while a0, j0 and Rt are minor influence factors. The minimum contribution from both D3 and A8 is 58% on head, and maximum contribution from both D3 and A8 is 90% on pressure pulsation. Regarding the pressure pulsation intensity, two peaks can be found. One is in the tongue area and the other is in the diffusor area. The contributions are around 60% from tongue and 25% from diffusor, respectively. The amplitude of pressure pulsation has a quadratic polynomial functional relationship with respect to D3/D2 and A8/A（10）, and fluctuating level of radial force has a quadratic polynomial functional relationship with respect to D3/D2. While for the other volute parameters a0, j0 and Rt, no special function has been found related to pressure pulsation and radial force. The presented work could be a useful guideline in engineering practice when designing a circulator pump with low hydrodynamic force.

GENERATOR VIBRATION FAULT DIAGNOSIS METHOD BASED ON ROTOR VIBRATION AND STATOR WINDING PARALLEL BRANCHES CIRCULATING CURRENT CHARACTERISTICS

Rotor vibration characteristics are first analyzed, which are that the rotor vibration of fundamental frequency will increase due to rotor winding inter-turn short circuit fault, air-gap dynamic eccentricity fault, or imbalance fault, and the vibration of the second frequency will increase when the air-gap static eccentricity fault occurs. Next, the characteristics of the stator winding parallel branches circulating current are analyzed, which are that the second harmonics circulating current will increase when the rotor winding inter-turn short circuit fault occurs, and the fundamental circulating current will increase when the air-gap eccentricity fault occurs, neither being strongly affected by the imbalance fault. Considering the differences of the rotor vibration and circulating current characteristics caused by different rotor faults, a method of generator vibration fault diagnosis, based on rotor vibration and circulating current characteristics, is developed. Finally, the rotor vibration and circulating current of a type SDF-9 generator is measured in the laboratory to verify the theoretical analysis presented above.

Numerical Study for Characteristic Change of Asian Summer Monsoon Circulation and Its Influence Mechanism during the EI Nino Period

In this paper, the relation between Asian summer monsoon circulation and sea surface temperature anomalies over equatorial central-eastern Pacific is investigated by using a global spectral model. This model has nine layers in the vertical and the model variables are represented in the horizontal as truncated expansions of the surface spherical harmonics with rhomboidal truncation at wave number 15. The model involves comparatively complete physical processes and parameterizations with mountains.Using the above model, two experimental schemes are designed, namely control case and anomalous sea surface temperature case. The above two schemes are respectively integrated for forty days and the simulated results are obtained from the last 30-day averaged simulations.The simulations show that positive SST anomalies over equatorial central-eastern Pacific weakens Indian monsoon circulation,decreases precipitation in Indian sub-continent whereas it intensifies East Asian monsoon circulation and increases precipitation in East Asian area. All these results reflect the characteristics of Asian summer monsoon during the El Nino period. In this paper, SST anomalies over equatorial central-eastern Pacific have a direct influence on the intensity and position of subtropical high via the wave train over Northern Hemisphere, which is similar to that suggested by Nitta(1987) and the wave train over Southern Hemisphere has an influence on the intensity of Muscarene high and Australia high resulting in affecting cross equatorial flow. As a result, atmospheric interior heat sources and sinks are redistributed because of the change of cross equatorial flow. And the response of atmosphere to the new heat source and sink has a significant influence on Asian summer monsoon.

Research Progress and Outlook of Low Temperature Chilling Injury in Northeast China

Focused on the major agro-meteorological disaster in northeast China area—low temperature chilling injury,the research progresses of low temperature chilling injury in northeast China were reviewed systematically.The basic concepts which included the connotation and extension of chilling damage,the circulation characteristics and effect factors which formed summer low temperature in northeast China,the prediction,forecast and defense of low temperature chilling injury were summarized and done the outlook.

Analysis and Forecasting Model of Durative Hightemperature in Late Spring and Early Summer in 2009

This paper analyzed characteristics of Pingliang City's continuous hot weather from late spring to early summer in 2009.The result showed that,when the daily maximum temperature in some parts of cities had run up to 32℃ or above,the number of days reached the top in recent 40 years.The average temperature,average maximum temperature,surface maximum temperature and surface average temperature in most parts of the city broke history record.Based on the analysis of characteristics of the 500 hPa circulation,which resulted in durative high temperature weather,3 kinds of the high temperature circulation patterns were summarized.It was the continental warm high pressure that resulted in the durative high temperature weather in June,2009.Meanwhile,by using European numerical forecast product and MOS,the forecasting method of high temperature,from June to August,was set up.The method had been used in June,and its high-temperature forecasting accuracy in 24,48,72,96,120 hours had respectively amounted to 76.6%,69.5%,61.4%,58.1% and 51.9%.

CHARACTERIZATION AND CAUSAL ANALYSIS OF TEMPORAL AND SPATIAL VARIATION IN DRY-WET CONDITIONS IN AUTUMN IN SOUTHWEST CHINA

Based on the daily precipitation and temperature data of 97 stations in Southwest China(SW China) from1960 to 2009, a dry-wet index is calculated. The spatiotemporal variation characteristics of dry-wet conditions,precipitation and temperature are studied. Then the abnormal atmospheric circulation characteristics are discussed using reanalysis data. The results show that SW China has exhibited an overall trend of autumnal drought since the late1980 s, and this drought trend became more significant early in the 2000 s, especially in the eastern SW China. Autumnal dry-wet variation in southwestern China showed two major modes: consistent change across the entire region and opposing changes in the eastern and western regions. The spatial distribution of dry-wet anomalies was more significantly affected by precipitation, while temporal variation in dry-wet conditions was more strongly influenced by temperature. The former mode is affected by the anomalies of the precedent SST near the Western Pacific Warm Pool,the Western Pacific Subtropical High, the East Asian Trough and the South Trough. The latter mode is related to the wind anomalies in the eastern SW China and the vertical movement in the western and eastern SW China. These are the main influencing factors for the autumn dry-wet variation in SW China, which are of great significance to the prediction of drought.

Characteristics of Two General Circulation Patterns During Floods over the Changjiang-Huaihe River Valley

Characteristics of the atmospheric general circulation during the catastrophic floods over the ChangjiangHuaihe River Valley （CHRV） are investigated. There are two precipitation patterns over China in the CHRV flood years： the CHRV flood-whole country-wet （P1） pattern and the CHRV flood-south （north） side-dry （P2） pattern. The circulation analysis results show that there are obvious differences between the NH 500- hPa geopotential height fields of P1 and P2 precipitation patterns. The establishment of East Asia-Atlantic （EAA） correlation chain （the South China Sea （SCS） high-the Meiyu trough-the Okhotsk Sea high over East Asia） is a critical condition for excessive summer precipitation over the CHRV, while the European blocking high plays an important role in determining the precipitation pattern over China in the CHRV flood years. Besides, the relation between the EAA correlation chain and the sea surface temperature anomaly （SSTA） in the North Pacific is also studied.

ON THE RELATIONSHIP BETWEEN PRECIPITATION ANOMALIES IN THE FIRST RAINING SEASON (APRIL-JUNE) IN SOUTHERN CHINA AND SST OVER OFFSHORE WATERS IN CHINA

Precipitation anomalies in the first raining season of southern China were analyzed,with the suggestion that there are obvious interannual variation of peak values.In the raining season,the general tendency of precipitation is not obvious and the anomalous oscillation is multi-scale.Corresponding to years of more or less precipitation in the raining season,there are sharply opposite distribution across the nation in the simultaneous periods.In addition,by studying the distribution of correlation between anomalous precipitation in southern China in the first raining season and SSTA over offshore waters of China in the preceding period (June ～August of the previous year),a sensitive zone of waters has been found that has steady effect on the precipitation of southern China in the season.Discussions are also made of the sensitive period,its simultaneous SSTA and subsequent anomalous circulation field in relation to precipitation anomalies and simultaneous circulation field in the first raining season of southern China.In the last part of the work,relationship between the SSTA in the sensitive zone and global SSTA is analyzed.A possible mechanism by which SSTA in offshore Chinese waters affects the precipitation anomalies in the first raining season of southern China is put forward.

Analysis of a Rare Continuous Rainy Process in Midsummer

[Objective] The research aimed to analyze a rare low temperature and rainy weather process which happened in Anhui Province from July 22 to August 14,2009.[Method] Based on the data of conventional observation,NCEP analysis field and automatic station,a rare low temperature and rainy weather process which occurred in Anhui Province from July 22 to August 14,2009 was analyzed.The formation reason of continuous rainy process in midsummer was discussed.The circulation characteristics and influence systems of continuous rainy process were revealed.On the base,the influences of configuration of circulation fields and difference of physical quantity fields at high and low layers on range and intensity of precipitation were analyzed.[Result] According to the circulation situation and influence system,the continuous rainy process could be divided into four stages:July 22-24,from July 27 to August 1,August 4-8 and August 9-14.Moreover,it was respectively affected by northeast low vortex,cold and warm air,high-level low trough,typhoon and periphery of subtropical high at four stages.The maintenance of big specific humidity zone provided sufficient water vapor condition for the continuous rainy weather.The rainstorm appeared in dense zone of specific humidity line,where the specific humidity >13 g/kg in the humidity front zone.A temperature trough maintained at 850 hPa.The cold air which continued to diffuse and go south was main reason of the abnormally low temperature during the continuous rainy period.Moreover,it provided ascending motion condition for precipitation maintenance.[Conclusion] The research provided references for actual forecast of continuous rainy weather.

Characteristics of the Current Sales and Circulation System in China

1. The sales and circulation system, taking by automakers in the lead, basically formed. The jointly managed and joint companies, established in the mid-1980%, have become gradually dominant element in the system. Along with the steady growth of auto production in the coming years, these companies will be getting stronger and stronger, with their sales and circulation networks being further perfected.

Characteristics of the Current Sales and Circulation System in China

5 Former circulation enterprises finding new market position Those large-sized auto circulation enterprises, which used to lead the circulation system, have been suffering the twist and turns from the new system oriented by automakers. Their market shares shapely fell down and have emerged into chaos. Parts of them that are powerful enough have established new sales companies controlled by the

Inhomogeneity characteristics of snow in Northeast China

Based on 1961-2005 observed winter precipitation data in Northeast China, the temporal and spatial variations of snow concentration degree （SCD） and snow concentration period （SCP）, together with the circulation characteristics when there is a higher SCD, are computed and analyzed. Results show that SCD in Northeast China presents a yearly rising tendency and SCP decreases obviously. In terms of decadal variation, there is a 12-year periodic variation in PCP, and since the mid-1970s there has been an 8-year short periodic variation. As to spatial variation, SCD in winter of Northeast China has increased gradually from the eastern part to the western, and the minimum value of SCD occurs in the east of Jilin Province, while the high value center is observed in the central part of the province. For the whole Northeast China, the variation tendencies are consistent in the eastern and central parts, where SCD presents a rising tendency and SCP shows a decreasing tendency. SCD in the southwestern and northern parts has a slight rising tendency, with SCD in the southwestern part having the slightest increasing tendency, and SCP in the northern part showing the slightest decreasing tendency. When a high SCD value is observed, the whole region is controlled by the East Asian deep trough at 500 hPa, and the trough becomes deeper in the western part, while a high pressure, which is easily formed and intensified in the eastern part, makes the East Asian deep trough move eastward slowly. Upper-level jet stream and low-level jet stream co-exist, and the former is stronger and takes more of a southwestward position than the latter. The high value zone of water vapor transport over the Pacific is intensified obviously, and the extent also increases. Northeast China is influenced by the water vapor transported to the northwest along the north of the high value center.

Analysis on the Long-Lasting Freezing Rain and Snowstorm Event at the Beginning of 2008

In this paper,main characteristics of the long-lasting freezing rain and snowstorm event in southern China at the beginning of 2008,features of the related atmospheric circulation and the causes thereof are analyzed.During the event,patterns of the atmospheric circulation stayed stable;the polar vortex located in the northern part of the Eastern Hemisphere was strong with little movement;the cold front from the polar region and the active warm air mass from the tropical ocean confronted each other for a long time;the blocking high to the west of Baikal remained strong and steady;the trough over central and western Asia maintained its position for quite long with a group of little troughs splitting from it frequently;the dominant wind at 700 hPa was southwesterly while shears and vortexes at 850 hPa developed continually,providing the necessary low-level convergence for subsequent precipitation.Meanwhile,in the mid troposphere,eddies were generated over the Tibetan Plateau and positive vorticity disturbances in the Sichuan Basin propagated eastward to the coastal regions of eastern China.The western Pacific subtropical high was intensive with westward and northward migrations.The subtropical frontal zone was puissant and the north-south temperature gradient was large.Quasi-stationary fronts over South China and the Yunnan-Guizhou Plateau remained stable.Warm air masses over the tropical ocean were active,so was the trough in the southern branch of the westerlies over the Bay of Bengal.There were four episodes associated with this event.The first one was featured with the interaction of strong cold and warm air,while the other three with the quasi-stationary fronts over South China and the Yunnan-Guizhou Plateau as well as vigorous penetration of cold air from the north.The existence of the inversion layer and the thick melting layer were one of the main reasons for the long-lasting freezing rains.The main reason for the snowstorms was that the positive vorticity over the Sichuan Basin propagated eastward to the coastal regions of eastern China.Abundant water vapor and intense updraft also favored the heavy snows.

THE ALTERNATE-SEASONAL CORRELATION OF LONG—RANGE WEATHER PROCESS

In this paper,the correlation of meteorological elements at an interval of 5—7 months,i.e.,the alternate-seasonal correlation,is thoroughly analyzed.The results show that the alternate-seasonal correlation is an important phenome- non in the long-range weather process,and it has a significant latitude effect and seasonal variations.Furthermore,the relation between this phenomenon and SST in the North Pacific is discussed.