Effect of different cold air intensities and their lagged effects on outpatient visits for respiratory illnesses in Handan in different seasons

本文利用2016年到2019年邯郸市气象要素和呼吸系统疾病门诊数据,分析了不同季节不同强度的冷空气过程及其对呼吸系统疾病的影响,结果显示:尽管呼吸系统疾病在冬季高发,夏季最低,但冷空气对呼吸系统疾病的影响在夏,春季最大,就诊人数分别在冷空气日后两天和五天增加18.4%和13.3%,而冬季就诊人数在冷空气日后三天仅增加3.2%.冷空气对疾病影响的滞后时间在夏,秋和冬季随冷空气强度的增加而减少,而春季的滞后时间总是很长.这些发现可为科学应对气候异常导致的人群健康风险提供针对性依据.

THE ROLE OF COLD AIR AND CHARACTERISTICS OF WATER VAPOR IN BOTH TCS NANMADOL (0428) AND IRMA (7427) MAKING LANDFALL ON CHINA IN WINTERTIME

The NCEP/NCAR reanalysis data are used to investigate the role of cold air and moisture characteristics during the evolution of two cases of tropical cyclones (Nanmadol and Irma) which made landfall on China in wintertime. The results are shown as follows. (1) The East Asia trough steered the cold air into the tropical ocean in early winter. The tropical cyclones moved in opposite directions with a high moving out to sea and the enhancement of the pressure gradient at the periphery played a role in maintaining and strengthening the intensity of the storms. The intrusion of weak cold air into the low levels of the tropical cyclones strengthened them by improving the cyclonic disturbance when they were still over the warm sea surface. When the cold air was strong enough and intruded into the eyes, the warm cores were damaged and stuffed before dissipation. (2) The tropical cyclones were formed in a convergence zone of moisture flux and their development could enhance the disturbance of water vapor convergence, thus strengthening the moisture convergence zone. However, when they were outside the moisture zone, the storms could not gain sufficient water vapor and became weak. There were no belts of strong moisture transportation during the wintertime tropical cyclone processes.

Some Characteristics of the Surface Boundary Layer of a Strong Cold Air Process over Southern China

In southern China, cold air is a common weather process during the winter season; it can cause strong wind, sharp temperature decreases, and even the snow or freezing rain events. However, the features of the atmospheric boundary layer during cold air passage are not clearly understood due to the lack of comprehensive observation data, especially regarding turbulence. In this study, four-layer gradient meteorological observation data and one-layer, 10-Hz ultrasonic anemometer-thermometer monitoring data from the northern side of Poyang Lake were employed to study the main features of the surface boundary layer during a strong cold-air passage over southern China. The results show that, with the passage of a cold air front, the wind speed exhibits low-frequency variations and that the wind systematically descends. During the strong wind period, the wind speed increases with height in the surface layer. Regular gust packets are superimposed on the basic strong wind flow. Before the passage of cold air, the wind gusts exhibit a coherent structure. The wind and turbulent momentum fluxes are small, although the gusty wind momentum flux is slightly larger than the turbulent momentum flux. However, during the invasion of cold air, both the gusty wind and turbulent momentum fluxes increase rapidly with wind speed, and the turbulent momentum flux is larger than the gusty wind momentum flux during the strong wind period. After the cold air invasion, this structure almost disappears.

ANALYSIS OF THE COLD AIR EFFECT ON AN EXTREME PRECIPITATION EVENT TRIGGERED BY AN INVERTED TROUGH OF TYPHOON HAIKUI(1211)

Based on intensive automatic weather station data, satellite cloud imagery, NCEP reanalyzed data, and the simulation results from mesoscale numerical models, this study analyzes the characteristics and formation mechanisms of the mesoscale convection system(MCS) during the extreme precipitation event that was triggered by a weakened low-pressure inverted trough of Typhoon Haikui on August 10/2012. The results of this study show that cold air at the rear of a northeastern cold vortex creates thermodynamic conditions favorable to the development of extreme precipitation. The main body of the cold air is northward located so that the cold air invades only the middle layer of the periphery of the inverted trough. Thus, the cold air minimally affects the lower layer, which results in a vertically distributed structure of the temperature advection that augments the formation and development of convective instability stratification. In the middle troposphere, the cold air encounters the convergent, ascending, warm moist air from the low-pressure inverted trough, leading to frontogenesis. The frontogenesis enhances wind convergence which, in turn, further enhances the frontogenesis, and the positive feedback between these two forces augments the development of meso- and small-scale convection systems in the rainstorm region and its vicinity, which strengthens the upward transportation of water vapor from low layers and thickening of water vapor convergence and results in local heavy rains.

DOPPLER RADAR ECHO CHARACTERISTICS FOR COLD AIR INTRUDING INTO TYPHOON CHANCHU

With Doppler radar data from Shantou and Xiamen and the National Centers for Environmental Prediction and the National Center for Atmospheric Research （NCEP/NCAR） reanalysis data, the characteristics of a short-term heavy rainstorm on 17 May 2006 caused by Typhoon Chanchu are studied. Doppler radar data indicates that during the period from 1800 to 1900 May 17, the azimuthal phases of the positive and negative radial wind maximums are asymmetric around the core radius of the typhoon, i.e., the radial wind on the left side of the track is anomalously larger than that on the right side. Studies show that this is induced by the intrusion of cold air （northeasterly wind）, which is primarily located at the mid-lower layers, lower than 4 kin; this is due to the intruding cold air that forces the atmosphere to uplift, enhancing the release of instability energy, which triggers the heavy precipitation. During the late stage of the cold air activity, the typhoon is rapidly weakened. Consistent with the radar-observed intrusion of cold air, the NCEP/NCAR reanalysis of wind data also shows that there are obvious large scalar wind values at the mid-lower layers （approximately 1-3 km） to the left of the typhoon center （1800 May 17）, and in all regions--except those affected by the intruding cold air--the wind speeds on the right side of the track remain larger than those on the left side. Furthermore, the Rankine model results confirm that northeasterly cold air is introduced to the typhoon at the mid-lower layers to the left of the track. Calculations also point out that there exists a frontal zone with high θse that tilts from southeast to northwest with height and the super heavy rainstorm occurring in the south of Fujian province lies just near the fxontal zone.

Air-sea fluxes of heat and momentum over the Yellow Sea during cold air outbreaks

The impact of sea surface waves on air-sea fluxes of heat and momentum over the Yellow Sea caused by cold fronts during cold air outbreak(CAO)events is investigated through numerical experiments with a FVCOM-SWAVE(Finite-Volume Coastal Ocean Model-Surface WAVE)wave-current coupled model.Two typical types of cold fronts,i.e.,those respectively from the north and from the west,are simulated and compared to each other and with monthly mean.During cold seasons,currents in the Yellow Sea are weaker than that during warm seasons.As a result,waves show a more prominent impact.The numerical simulations suggested that both the heat and momentum fluxes are significantly enhanced during CAO events;and they could be a few times larger than the monthly average of a five-year mean.The enhancement is highly sensitive to the features of CAOs.Specifically,it depends on the cold front orientation,intensity and evolution.One mechanism that strengthens the two fluxes is via sea waves.For the CAOs that are studied,an increase in sea wave height by 50%can double the maximal momentum flux,and cause an increase in heat flux by 10-160 W/m^2.

Effects of cryogenic cold air jet cutting on chip break in metal machining

The half-dry cutting employs cryogenic compressed air cooled down to (10 to 40) and a micro-dosage of lubricating oil, called cryogenic cold air jet cutting was studied. On the basis of a comparative experiment on dry and cryogenic cold air jet cuttings carried out for grade 45 steel, the effects of cryogenic cold air jet on the breaking of chips were discussed. The experimental results reveal that in the valid ranges of pressure and temperature, the cryogenic cold air jet widens the chip breaking areas effectively. When the cutting depth is not greater than 1 mm, the influence of chip breaking is much more significant. But different injecting angle of cold air has different influence on the chip-break. From the experiment, the optimized jet injecting angle, temperature effecting range and pressure working range of cold air are obtained. These results can offer a foundation for industrial manufacturing.

Analysis and Discussion of a Strong Cold Air Process in Spring

Based on NCEP 1°×1°daily reanalysis data and conventional surface observation data,the potential vortex theory was used to analyze a strong cold air activity process of Karamay during May 15-16,2019.The results showed that the weather had obviously baroclinic characteristic.A strong cold tongue extended straight to Central Asia from the high latitude area,and the cold air was strong and deep.The driving effect of cold trough could accelerate it to move southward.The Aral Sea low vortex obstructed the warm air in the north in high latitude area,and the southwest air flow in the front of the vortex conducted to the transportation of water vapor to Central Asia.Compared with the climate average field of 1981-2010,the northwest flow at 500 hPa in May of 2019 was aggressive,which had frequently influenced Xinjiang by cold air from the north high latitude regions.The east flow of the bottom layer not only input cold air to Karamay,but also formed the windward slope effect with the terrain.Moreover,it increased the vertical wind shear and induced the upward movement.The center of high potential vorticity with high latitude fell southward,and the center of low potential vorticity in Central Asia moved eastward rapidly.They combined and then moved toward Xinjiang,which made the strong cold air erupt rapidly.When the right side of the moved axis of the high potential vorticity center and the strong west flow superposed over the Karamay area,the center of the strong rainfall area appeared 6 h later.

Analysis of Cold Air and Precipitation in Central and Eastern China, 2-5 October, 2022

This paper used potential height field data published by the China National Climate Center and the US NCEP reanalysis data. A study was conducted on a strong cold wave weather process in central and eastern China from October 2 to 5, 2022. The results show that this weather process is a cold air weather process of “horizontal trough to vertical” type from the east of Novaya Zemlya Island. Cold air passes through Russia and Mongolia south, controlling northern China. The precipitation process is caused by the combination of high-altitude trough, ground front, warm and humid air flow, and precipitation weather formed by the influence of warm and humid air due to the 700 hPa shear line. The northern Sichuan Basin and the middle and lower reaches of the Yellow River in China can precipitate almost 50 mm. Water vapor is transported from the South China Sea to central and eastern China by the southwest warm and humid air flow along the west side of the West Pacific Subtropical High. Water vapor is concentrated over the precipitation area through horizontal convergence and is the most important source of water vapor causing precipitation.

Analysis of a Large Scale Cold Air Weather Process in China during January 2021

This study uses data provided by the National Meteorological Information Center of China, Japan Meteorological Agency (JMA) and National Oceanic Atmospheric Administration (NOAA) Physical Sciences Laboratory of the USA to analyze a cold air weather process at the beginning of January 2021. Synoptic analysis is mainly used to summarize synoptic laws or patterns based on observational data, and describe and infer weather processes. The main conclusions are as follows: The cold air travels south along the northwest path, affecting most of China. During the cold wave process, the first cold air is weak, which has a certain cooling effect on northern China. The second cold air was guided by the low vortex, the accumulation in the transverse groove of Mongolia was strengthened, and the cooling effect was significant. The southwest jet showed an increasing trend, and the water vapor transport conditions were good. However, due to the relatively gentle southern branch system, the warm and humid air flow was weak and the precipitation level was small. The purpose of this study is to better understand a large-scale cold air weather process in January 2021 in China.

NUMERICAL STUDY OF COLD AIR IMPACT ON RAINFALL REINFORCEMENT ASSOCIATED WITH TROPICAL CYCLONE TALIM(2005):I.IMPACT OF DIFFERENT COLD AIR INTENSITY

In 2005,significant rainfall reinforcement and severe disaster was induced by tropical cyclone(TC) Talim after it made landfall on the east of China.Observational analyses show that it has relationship with cold air intrusion.For investigating the impact of cold air intensity,we make use of Weather Research and Forecasting(WRF) model,the synthesizer of NCEP/NCAR reanalysis data and Japan regional spectral model data,to carry out numerical experiments.Results show that rainfall reinforcement occurs in all experiments.Different intensity of cold air can modify the rainfall distribution and intensity significantly.In the rainfall center,the increment maximum of rainfall is twice as large as that of the minimum.Moderate cold air intrusion may result in the strongest rainfall reinforcement.Different cold air intensity can lead to different motion of low-level convergence lines and fronts.There is a good relationship between the rainfall region and the eastern part of the front.On one hand,strong cold air weakens the TC intensity by its intrusion into the TC center and results in weak convergence and a convergent zone and a rain band shifted southward.On the other hand,weak cold air reduces the convergence and moves the convergent zone and rain band northward.Moderate cold air intrusion maintains strong low-level convergence and high-level divergence,keeping strong upward motion over certain regions.Consequently,the rain band begins to stagnate and rainfall reinforces abruptly therein.

EFFECT OF DRY COLD AIR ACTIVITY ON THE OFFSHORE RAPID INTENSIFICATION OF SUPER TYPHOON SAOMAI(2006): A NUMERICAL SIMULATION RESEARCH

Employing the mesoscale WRF(Weather Research and Forecast) model, Super Typhoon Saomai(2006) is simulated. The variation of track and intensity and its offshore rapid intensification process are well demonstrated by the model, and the temperature and humidity patterns associated with the dry cold air activity and their impact on and mechanism of the offshore rapid intensification of Saomai are mainly studied in this paper. The results indicate that high-resolution water vapor imagery can visually reveal the development, evolution, interaction as well as the mutual complementation of the dry cold air activity accompanied with the development of Saomai. The offshore rapid intensification phenomenon of Saomai is closely related to the dry cold air which originates from the upper- and mid-troposphere. Besides, the dry cold air from the upper troposphere is stronger than that from the mid-troposphere.Saomai intensifies as the dry cold air from the northwest moves toward its circulation but weakens when the dry cold air from the southwest is drawn into the storm. Dry cold airflows and their cold advection effect caused by the downward motion across the isentropic surface are favorable to the development of Saomai. The dry cold air always moves along an isentropic surface from the upper troposphere to the mid-troposphere around the typhoon circulation and contributes to Saomai's abrupt intensity change.

Characteristics of Dry Cold Air Intrusion in a Typical Strong Storm

Taking a typical strong storm in Guizhou on April 5, 2017 for example, the diagnosis analysis used the water vapor cloud and the initial field of EC thin grid, including physical quantity, surface and upper air meteorological observation, as well as radar observation data. For the environment parameter analysis, small CAPE value tended to underestimate storm intensity on potential forecast stage, strong vertical wind shear revealed the strong dry cold air was the important intensity factors of the storm. The water vapor cloud map can be used to monitor the most important features, the dry zone, the wet zone and the boundary between them. When dry intrusion is found, it can be used as one of the bases for the development of heavy rain. Dry cold air intrusion on high-level was traced by water vapor images. And in this process, the analyses revealed the role of dry cold air’s influence on intensity of the storm.

Analysis on the Process of a Convective Rainstorm of Stationary Front Triggered by Weak Cold Air

Based on the conventional meteorological data and the NCEP/NCAR 1&#176 × 1&#176 reanalysis data and those related to mid-scale automatic station, satellite cloud picture and radar return, with the dynamic diagnosis analysis method, an analysis is made on the process of the convective rainstorm of quasi-stationary front triggered by the weak cold air on June 4-7, 2014, showing: 1) the process occurred in the event of convection of a stationary front triggered by the eastward moving south trough and the southward moving weak cold air from west under the background of circulation of two ridges and one trough at the Asian-European mid-high latitude and weakening and southeastward moving subtropical high;2) a system configuration that contributes to convective rainstorms formed in the event of the convergence of low-level moisture, upper-level divergence and the continuous vertical ascending motion after the 200 hPa upper-level jet stream moved westwards from east and the 850 hPa southwest jet stream intensified;3) after the intrusion by weak cold air of the meso-scale katallobaric area formed by the accumulated warm moist air of Guangxi before the intrusion, the warm moist air rose to trigger convection;convection cells developed and spread nearby the boundary between anallobaric area and katallobaric area, during which total 5 MCSs developed and each formed a rainstorm center at the part where the MCSs coincide;a meso-scale katallobaric area forms and develops 2 - 5 hours earlier than convection, so that it is also a warning of heavy rains.

STUDY OF PHYSICAL PROCESSES AFFECTING THE TRANSFORMATION OF COLD AIR OVER LAND AFTER OUTBREAK OF COLD WAVES IN EAST ASIA

Authors have studied the transformation processes of cold air over land in East Asia for eight cases which occurred in different months of 1981.First,the surface eddy sensible and latent heat fluxes,and drag coefficient were estimated according to the approach of similarity theory.Then,the apparent heat source,the apparent moisture sink,and solar and long-wave radiative heating(or cooling)were further calculated through the budget method and physical parameterization algorithm.It has been found that the cold air immediately starts the transformation process over land once it moves away from its region of origin.In winter,the degree of transformation of cold air mass gradually intensi- fied as it travelled southeastward;while arriving in the ocean,the cold air mass underwent the most significant transfor- mation process.In summer,the most vigorous transformation of thermal and moisture fields was observed in North China and Mongolian region,with much greater intensity than that in winter.

NUMERICAL EXPERIMENT WITH PROCESSES FOR EFFECT OF AUSTRALIAN COLD AIR ACTIVITY ON EAST-ASIAN SUMMER MONSOON

Based on diagnostic results,a numerical study is made of the processes of Australian cold air activity affecting East Asian summer monsoon by using Kuo-Qian P-σ incorporated coordinate five-layer primitive equation spherical band model.Analysis is done of the response to the Southern Hemisphere circulation with and without cold air activity in Australia of the flow,rainfall and diabatic heating fields in the monsoon area of Asia,especially,East Asia,with special attention to the intensification and northward march of the monsoon due to the activity.It is found that the processes for the effect transmission are very analogous to the meridional propagation of quasi-40-day oscillation,together with the meridional wind disturbance showing south-north travel and the flow/rainfall fields exhibitirg corresponding movement in this direction,only with a 12-day lag.

Cold Air Activities in July 2004 and Its Impact on Intense Rainfalls over Southwest China

The severe rainfall events in the mid-summer of July 2004 and the roles of cold air in the formation of heavy precipitation are investigated by using daily observational precipitation data of China and NCEP/NCAR reanalysis. The results show that the severe rainfalls in Southwest China are closely related to the cold air activities from the mid-high latitudes, and the events take place under the cooperative effects of mid-high latitude circulation and low latitude synoptic regimes. It is the merging of a cold vortex over mid-latitudes with the northward landing typhoon and eastward Southwest China Vortex, as well as the abrupt transformation from a transversal trough into an upright one that causes three large alterations of mid-high atmospheric circulation respectively in the early and middle ten days of this month. Then, the amplitude of long waves soon magnifies, leading to the unusual intrusion of cold air to low-latitude areas in the mid-summer. Meanwhile, the warm and humid southwest summer monsoon is quite active. The strong interactions of cold air and summer monsoon over Southwest China result in the large-scale convective rainfalls on the southern side of cold air. With regard to the activities of cold air, it can influence rainfalls in three prominent ways. Firstly, the incursion of upper-level cold air is often accompanied by partial southerly upper-level jet. The ascending branch of the corresponding secondary circulation, which is on the left front side of the jet center, provides the favorite dynamic upward motion for the rainfalls. Secondly, the southward movement of cold air contributes to the establishment of atmospheric baroclinic structure, which would lead to baroclinic disturbances. The atmospheric disturbances associated with the intrusion of cold air can destroy the potential instability stratification, release the convective available potential energy （CAPE） and finally cause convective activities. In addition, the advection processes of dry and cold air at the upper level along with the advection of humid and warm air at the lower level are rather significant for the reestablishment of potential instability in the precipitation area, which is one of the crucial factors contributing to persistent rainfalls.

A Study on a Snowband Associated with a Coastal Front and Cold-Air Damming Event of 3-4 February 1998 along the Eastern Coast of the Korean Peninsula

A 24-h simulation with the Advanced Regional Prediction System （ARPS） nonhydrostatic model is performed for the heavy snowfall event of 3-4 February 1998 along the eastern coast of Korean Peninsula; the results are used to understand the snowfall process, including why the precipitation maxima formed along the Yeongdong coastal region rather than over the mountain slope and ridge top during. The numerical simulation with a 4-kin horizontal grid spacing and 43 levels reproduces very well the narrow snowband located off the eastern Korean coast, away from, instead of over, the Yeongdong coastal mountain range. The general evolution of the snowband agrees quite well with radar observations, while the water-equivalent precipitation amount agrees reasonably well with radar precipitation estimate. The simulation results clearly show that the snow band developed due to the lifting by a coastal front that developed because of the damming of cold air against the eastern slope of the coastal mountain range. The damming was enhanced by the advection of cold air by a tow-level mountain-parallel jet from the north, formed due to geostrophic adjustment as the on-shore upslope air was decelerated by the mountain blocking. As the onshore flow weakened later due to synoptic-scale flow pattern change, the cold front propagated off shore and the precipitation dissipated.

Understanding the physical processes in the evolution of a cold air outbreak over China in late November 2022 from a Lagrangian perspective

From 26 November to 1 December 2022,intense cold air masses swept across China from northwest to south,resulting in a nationwide cold air outbreak(CAO)case characterised by drastic and sudden temperature drops with rain,snow and strong winds.The physical processes that dominate the intensification of the cold air masses during this CAO event remain unclear.In this study,the evolution of the CAO case,which is indicated by the dry static energy(DSE),is investigated using a novel approach in the framework of Lagrangian backtracking.The dominant processes can be identified by decomposing the DSE change into four diabatic heating terms due to shortwave radiation,longwave radiation,latent heat and turbulent processes.Overall,in this case,most of the cold air parcels originated from the east of Novaya Zemlya and crossed Central Siberia before reaching China.Thus,these air parcels mainly manifested on the northwest‒southeast path.The duration of the cold air intensification differed between subregions.The cold air parcels experienced long cooling periods(approximately 9 d)before reaching northern China(i.e.Northwest,North and Northeast China),whilst the southern parts(i.e.Central,East and South China)underwent relatively short cooling periods(6-8 d).Accordingly,the cold air affecting northern China is more intense than that affecting the southern parts,especially for East and South China.For all six subregions,longwave radiative cooling is identified as the dominant contributor to the cold air intensification,and the latent heat processes as the secondary contributor.The weakening of cold air parcels as they approach and pass over these regions is driven by turbulent processes and shortwave heating.Central Siberia and Lake Baikal are identified as key areas for the intensification of cold air passing over both regions.In addition,air parcels affecting Northwest China are intensely cooled as they pass over the Junggar Basin,while the North China Plain is a key area for cooling air parcels reaching Central,East and South China.From a Lagrangian perspective,these findings provide insights into the physical processes driving the behaviour of cold air parcels,which would help understand the mechanisms involved in the past changes and future projections in CAOs.

Field experimental study on the cooling effect of mine cooling system acquiring cold source from return air

With the increase of mining depth, more and deeper coal mines are limited by heat disaster. The cooling energy in deep mine cooling system comes from mine water inrush or ground cooling tower, but we cannot adopt the two methods because mine water inrush in many old coal mines in China is limited. What is more, the cooling pipelines cannot be put in narrow pit-shaft. To settle the problem above, according to the characteristics of Zhangxiaolou Coal Mine, this paper adopts the deep mine return air as the cooling energy for deep mine cooling system. In addition, we carried out cite test to extract cold energy from return air. Through monitoring the water quantity, water temperature of cooling system and air temperature, we got the thermodynamic equilibrium parameters during the cooling energy acquisition analysis and the effect of cooling system that the temperature and humidity on working face are respectively reduced to 8-12 ℃ and 8-15% through cooling. This research offers experimental reference for deep mine cooling which lacks cooling energy.