Analysis of Characteristics of Snow Accumulation and Its Meteorological Influencing Factors during a Snowstorm Process in Ulanqab City

Based on the data of national observation stations of CMISS system,artificial encrypted observation data of snow depth,ERA5 reanalysis data,the snowfall process in Ulanqab City from March 17 to 19,2022 was analyzed.It is found that the influencing system of the snowfall process was upper-air trough combined with ground inverted trough.Snowfall was not proportional to snow depth,and the relationship between the maximum snow depth and total snowfall varied in different value intervals.A large intensity of snowfall was a necessary condition for the formation of abundant accumulated snow when ground temperature was higher than 0℃.After the formation of accumulated snow,ground temperature changed less,and it was easy to produce accumulated snow as ground temperature was lower.The lower the temperature,the more conducive to the generation of accumulated snow.

Analysis of a Type Ⅱ Snowstorm Process in the Early Spring of 2022 in Ulanqab

Based on the observation data of meteorological stations,Doppler radar observation data of Ulanqab City,and ERA-5 reanalysis data,a snowstorm process in Ulanqab City from March 17 to 18,2022 was analyzed.The results show that this was a type Ⅱ snowstorm process generated under the joint influence of upper trough and ground low inverted trough and frontal cyclone.The main period of snowfall can be divided into two time stages,and the total snowfall was more in the south and less in the north,which was consistent with that of average specific humidity field.Water vapor conditions provided by strong water vapor transport and convergence,strong upward movement shown by large vertical velocity field,and the suction action of high-and low-layer divergence and convergence were the reasons for the hourly heavy snowfall on the 18^(th).During the process,radar echoes were mainly sheet-shaped,and composite reflectivity was 15-25 dBZ in most areas.The zero speed line in the first period was positively"S"-shaped,and there was warm advection and southwest wind.On the morning of the 18^(th),after the cold front transited the city,Ulanqab City was gradually controlled by northwest wind,and the snow tended to end.

Spatial and Temporal Distribution Characteristics of Snowstorm in Ulanqab City in Recent 30 Years

Based on the data of daily snowfall and weather phenomena of 11 national meteorological stations in Ulanqab City from 1991 to 2020,the spatial and temporal distribution characteristics of snowstorm were analyzed.The results show that the snowstorm in Ulanqab had obvious seasonal distribution characteristics,mainly happening in spring(March-May)and autumn(September-November).It also had obvious regional distribution in space,and the snowstorm center appeared in Chahar Right Wing Middle Banner and Jining District,namely the east side of the Yinshan Mountain.In the past 30 years,the amount of snowstorm in the whole year in Ulanqab showed a certain fluctuation trend,and the number of snowstorm days had shown an obvious upward trend since 2011.

Reflection on China's Disaster Prevention and Mitigation Construction after Rainstorm and Snowstorm

On July 10,2004,Beijing was hit by the rainstorm that has not been seen for many years,which caused water accumulation in many places of the urban area,power supply interruption in many places,and traffic paralysis for nearly 5 h. On July 12,2004,the rainstorm in Shanghai lasted less than 1 h,but it caused 7 deaths,more than 20 injuries,extensive power outages and traffic paralysis. At the end of 2005,the continuous snowfall in Weihai City of Shandong Province for half a month caused direct economic losses of over 200 million yuan,and the continuous heavy snowfall had a serious impact on people’s lives. From July 17 to 23,2021,Henan Province suffered a rare extremely heavy rainstorm in history,with a direct economic loss of 120.6 billion yuan. Faced with such urban meteorological disasters and other types of urban disasters,combined with the current situation of disaster prevention and reduction in China,what will managers,decision-makers,and experts and scholars think about from them.

Analysis of Snowstorm Process in Northeast China during 5-9 November, 2021

In November 2021, Northeast China had more precipitation than in the same period. Among them, Heilongjiang and Jilin provinces in the Northeast China were the highest precipitation in the same period. I study a snowfall weather process from November 5 to 9, which mainly includes dynamic situation, synoptic background and situation. The results show that: In the middle and high latitudes of Eurasia, circulation is adjusted from zonal to meridional with large fluctuations. The northerly wind behind the trough continuously transports the polar cold air to the south. The northwest airflow behind the trough led the cold air to erupt to the southeast. In the process of moving southward, the cold air meets the warm and humid air in front of the trough, causing snowfall in the northeast. The southerly airflow and southeasterly airflow on the east side of the vortex continued to transport warm and humid airflow from the Yellow Sea and the Sea of Japan, which enhanced the snowfall.

Effect of Snowstorm on Winter Wheat Production in Tacheng Basin in 2009

Located in Eurasia inland,Tacheng Basin belongs to arid and semi-arid climate region in middle temperate zone,and the main crops include winter wheat,spring wheat,maize,seeding-watermelon,sugar beet and so on,while winter wheat is the main food crop.From November 2009 to March 2010,a snowstorm which occurred every 60 years appeared in Tacheng Basin,and there was more snowfall in five continuous months,while this snowfall broke through the extreme value in history and reached a historic high.Based on the comparison between practical monitoring data and history data of winter wheat,the effects of snowstorm on winter wheat production were analyzed.

Horizontal distribution and levels of heavy metals in the biggest snowstorm in a century in Shenyang,China

The horizontal distribution and levels of heavy metals in the biggest snowstorm in Shenyang since 1904 were investigated by analyzing 4 metals (As,Cd,Pb,and Cu) in a series of ultraclean samples collected from 17 sites distributed in different regions of the Shenyang area,China.The results showed that the concentrations of all the 4 heavy metals in snow from the industrial regions were high,up to 7.3 (As),2.2 (Cd),850.0 (Pb),and 0.197-20.2 (Cu)μg/kg,respectively.In the suburb,in contrast,their concentration...

Observational Analyses of Baroclinic Boundary Layer Characteristics during One Frontal Winter Snowstorm

The evolution and characteristics of the baroclinic boundary layer for one frontal winter snowstorm were analyzed by using the well-documented dataset during Intensive Observation Period (IOP) 17 of STORM-FEST. It is found that when the warm moist air was lifted across the front, a great amount of latent heat release because of snowing increased the frontal temperature contrast to intensify frontogenesis. It is shown in the zig-zag section diagram of potential temperature that when the frontogenesis got stronger, a cold trough was formed and both low-level jet (LLJ) and upper-level jet (ULJ) emerged ahead of the front. In the strongest stage of frontogenesis, the frontal contrast of potential temperature of cold trough reached as high as 20 K. Hereafter the LLJ ahead of the front tended to weaken and the LLJ behind the front tended to strengthen. The frontal circulation system was dominated by the cold air advection behind the front, which transported the cold air behind the front forward to the warm area ahead of the front to weaken the cold trough and finally frontolysis occurred. It is shown by the analyses of turbulent characteristics of frontal baroclinic boundary-layer that the vertical shear (WV) above the boundary layer was very large, and the pumping of the strong wind shear in turbulent energy budget made the characteristic variables within the PBL well mixed. Sufficient moisture carried by southerly flow from the Mexico Gulf, and the strong baroclinity of the frontal boundary layer played key roles in this frontal winter snowstorm, and the large-scale ULJ behind the cold front is also advantageous to the development of the convective boundary layer.

A QUANTITATIVE STUDY FOR ABNORMAL FREEZING RAINS AND SNOWSTORMS IN SOUTHERN CHINA IN EARLY 2008

A quantitative diagnosis is carried out for the upward branch of a local meridional circulation over southern China(SC) during the abnormal snowstorms with severe freezing rain from 10 January to 3 February 2008.The diagnostic study shows that the upward branch is mainly associated with the zonal advection of westerly momentum and meridional temperature advection instead of the latent heating(which is commonly the dominant factor in many other storm cases).The corresponding weather analyses indicate that(1) the zonal advection of westerly momentum represents the effect of the upper-level divergence on the anticyclone-shear side in the entrance of a 200 hPa westerly jet with a westward deviation from its climatological location over southwestern Japan;(2) the meridional temperature advection represents the interaction between the mid-lower layer(850 to 400 hPa) warm advection over SC(ahead of temperature and pressure troughs with the latter trough deeper than the former in the Bay of Bengal) and cold advection over north China(steered by an underlying flow at 500 hPa);(3) the relatively weak vapor transport(compared to that of spring,summer and autumn) from the Bay of Bengal and the South China Sea to SC and the existence of a temperature inversion layer in the lower troposphere over SC diminish the effect of latent heating.With the significant increase of vapor transport after 24 January,the role of latent heating is upgraded to become the third positive contributor to the upward branch over SC.

Eddy Kinetic Energy Study of the Snowstorm over Southern China in January 2008

The energetics of the third stage of a snowstorm over China was analyzed using ECWMF data.The analysis of the energy budget for the Middle East trough and the western Pacific trough that developed toward China on 25-28 January 2008 showed the advection of the geopotential by the ageostrophic wind to be both a crucial source and the primary sink of the eddy kinetic energy centers associated with the troughs.The magnitudes of the energy conversion terms,interaction kinetic energy conversion and baroclinic conversion,were too small to explain the development of the energy centers and the jet streaks.The energy centers gained energy at their entrance regions via the convergence of the ageostrophic geopotential fluxes,and then lost energy at their exit regions by the same fluxes.At the entrance regions,the fluxes converged,increasing the geopotential gradient,which generated a stronger geostrophic wind and higher kinetic energy,resulting in an ascending motion in this area.When the troughs moved to China,the ascending motion caused by the convergence of the fluxes at entrance region intensified the snowstorms over central and southern China.

Study on Possible Mechanism of Terrain Influence on Cold-flow Snowstorm

[Objective] The research aimed to study the possible mechanism of terrain effect on cold-flow snowstorm.[Method] By using the meso-scale numerical model(WRF),a cold-flow snowstorm weather process in Shandong Peninsula was carried out numerical simulation and terrain sensitivity contrast test.The possible reason of terrain effect on falling zone and strength of snowstorm was deeply analyzed from water vapor,thermodynamic field and so on.[Result] The mountain terrain in Shandong Peninsula had great influences on falling zone and strength of cold-flow snowstorm.The strength of snowstorm obviously increased,and the snowfall center obviously moved northward.The main reason was that terrain caused the low-level wind field convergence and vertical movement in the troposphere strengthened.Then,the spatial distribution of water vapor and snow water content in the cold-flow snowstorm process obviously changed.So,the whole snowstorm process was affected.[Conclusion] The mountain terrain in Shandong Peninsula was the important element which needed to be focused on considering in the forecast analysis of cold-flow snowstorm weather process.

A Neural Network Method for Monitoring Snowstorm: A Case Study in Southern China

It has been observed that low temperature, rainfall, snowfall, frost have never occurred over the past 50 years in the southern China, and weather in this area is very complex, so the monitoring equipments are few. Optical and thermal infrared remote sensing is influenced much by clouds, so the passive microwave Advanced Microwave Scanning Radiometer-Earth Observing System （AMSR-E） data are the best choice to monitor and analyze the development of disaster. In order to improve estimation accuracy, the dynamic learn- ing neural network was used to retrieve snow depth. The difference of brightness temperatures of TB18.7v and TB36.sv, TBI8.7H and TB36.sH, TB23,sv and TB89v, TBz3.8H and TB89H are made as four main input nodes and the snow depth is the only one output node of neural network. The mean and the standard deviation of retrieval errors are about 4.8 cm and 6.7 cm relative to the test data of ground measurements. The application analysis indicated that the neural network can be utilized to monitor the change of snow intensity distribution through passive microwave data in the complex weather of the southern China.

A Study on Snowstorm Weather in Coastal Area of Western Antarctic

In this paper, based on the observational data of 1995 in the Chinese Antarctic Great Wall Station the snowstorm is studied synoptically. It is found that there are two kinds of snowstorms with different physical characteristics and that the happening of snowstorm is always accompanied by a near-ground level inversion layer. The function of the inversion layer is analyzed, too. It is indicated that the strong ESE-wind type snowstorm is mainly caused by katabatic wind and gradient wind together. This idea is new and different from the general concept that there is no katabatic wind in the western Antarctic area.

Analysis on the Heavy Snowstorm Process in Northeast China during March 3-5 in 2007

Based on the routine observation data,the satellite cloud images and so on,the synoptics analysis and the diagnostic analysis of physical quantity field were used to analyze the heavy snowstorm process which happened in Northeast China during March 3-5 in 2007.The results showed that the main influence systems in the process were the eastward shift and up north of southern cyclone,the combination of south and north branches upper troughs in 500 hPa.The dynamic mechanisms of heavy snowstorm formation were the strong ascending movement which was caused by the configuration of high-layer divergence and low-layer convergence,the generation and maintenance of deep and thick positive vorticity in the middle and low layers.The sufficient water vapor in the East China Sea and the South China Sea which was brought by 700 hPa by south low-level jet stream reached Northeast China.The falling zones of strong precipitation were consistent with the big value zones of 850 hPa positive vorticity and 200 hPa positive divergence.Meanwhile,the intensity of temperature advection and the position of cold warm transition zone could reflect well the intensity and falling zone of precipitation.

Diagnostic Study of a Winter Snowstorm Event

A diagnostic study of a winter snowstorm event was presented.The results showed that some factors were of importance to the formation of the snow gush.Most of the factors were similar to those for summer ram gush.while Shetomperuare stratification structure was important to distinguish snow from rain.

Analysis on the Physical Mechanism of Snowstorm Generated by the South Cyclone

[Objective] The research aimed to study the physical mechanism of snowstorm which was generated by the south cyclone. [Method] By using the routine meteorological observation data, satellite data and MM5 mode output data, the snowstorm weather in the east of Heilongjiang Province during March 4-6, 2007 was analyzed. The physical mechanism of snowstorm which was generated by the south cyclone was discussed. [Result] Jianghuai cyclone advanced northward to generate the snowstorm. In the middle and high latitudes, the good cold air must coordinate with it. Meanwhile, the south cyclone provided the good high temperature condition and the rich water vapor condition for the snowstorm generation. The snowstorm generation must have the close coordination of airflows in the high and low levels, and the strong convergence ascending movement was generated. The vertical movement made that the atmospheric energy could be transformed. When the snowstorm was generated, there was the strong vertical ascending movement in the high altitude. The snowstorm falling zone was in the north side of big value zone. The variation of TBB cloud top temperature intensity as the time had the good guidance role for forecasting the starting time of strong snowfall. The convergence center of water vapor flux divergence and the zone where the temperature drew point difference in 925 hPa layer ≤ 4 ℃ had the good corresponding relationships with the snowstorm falling zone and the snowfall strong center. It provided the good reference index for forecasting the falling zone and strong center of snowstorm. Under the restriction of moist potential vorticity conservation, for the leaning of θe surface, the atmospheric horizontal wind was vertical, or the wet baroclinicity increased, which could cause the significant development of vertical vorticity. The bigger θe surface leaning was, the stronger the cyclonic vorticity was. It was easy to cause the strong precipitation weather. When the high-altitude dry cold air invaded and glided along θe ridge surface, the unstable energy was induced to release, which provided the energy for the snowstorm generation. The dry invasion process was also the strong snowfall generation process, and the snowstorm falling zone was in the steep and dense zone of θe. [Conclusion] The research provided the theory basis for the prediction and forecast of rainstorm weather.

Circulation Characteristics Analysis on A Rare Light Rain Changing to Snowstorm Weather

By using the ground,high-altitude conventional observation data and NCEP global reanalysis data,the circulation background and the snowfall causes of light rain changing to snowstorm weather process in Panjin during February 12-13 in 2009 were analyzed in detail.Focusing on the rain and snow phase state conversion time,the effects of precipitation phase state transformation time on this precipitation forecast were discussed.The results showed that the circulation adjustment,the eastward shift and down south of polar vortex and the frequent activity of cold air were the main factors which caused the precipitation was obviously more in February in Panjin.The direct reasons which caused the strong snowfall in Panjin were that the warm and cold air evenly matched for a long time,and the southwest jet provided the sufficient water vapor condition.

A Case study of a snowstorm at the Great Wall Station,Antarctica

A case of a snowstorm at the Great Wall Station was studied using data of NCEP（National Centers for Environmental Prediction） analysis,in situ observations and surface weather charts.The storm occurred on August 29th, 2006,and brought high winds and poor horizontal visibility to the region.It was found that the storm occurred under the synoptic situation of a high in the south and a low in the north.A low-level easterly jet from the Antarctic continent significantly decreased the air temperature and humidity.Warm air advection at high level brought sufficient vapor from lower latitudes for the snowstorm to develop. The dynamic factors relating to strong snowfall and even the development of a snowstorm were deep cyclonic vorticity at middle and low levels,the configuration of divergence at high level and convergence at low level,and strong vertical uplift.There was an inversion layer in the low-level atmosphere during the later phase of the storm.This vertical structure of cold air at low levels and warm air at high levels may have been important to the longevity of the snowstorm.

Aerodynamic Behavior of Snowflakes on an Uneven Road Surface during a Snowstorm

The removal of snow from a road or railroad results in an uneven surface and thus the formation of snowdrifts. However, the effect of a surface bump on the scale of a snowdrift is not clear. Snowdrift wind tunnel tests have long been performed to predict the snow cover distribution due to a snowstorm. However, such tests require a large-scale experimental device, have high installation and maintenance costs, and are not easy to perform. The present study thus used a small water tunnel that is easier to implement. The snowdrift pattern for the real phenomenon of a cube model was reproduced using the small water tunnel and the performance of the tunnel thus verified. The snowdrift water tunnel was then used to predict the snowdrift distribution for uneven surfaces. The tunnel well reproduced the snow cover distribution when the sedimentation velocity ratio and Stokes number in the water tunnel test were the same as those for the real phenomenon, again verifying the performance of the water tunnel test.

Verification of Mongolian Cyclone-Induced Snowstorm Model Forecast in Jilin Province, China

Situation field forecast and rainfall forecast in typical numerical forecast models including EC (The European Centre for Medium-Range Weather Forecasts), t639 (T639 Global Forecast System) and Japanese model were verified by set statistics and TS (Threat Score) scoring based on 8 cases of Mongolian cyclone-induced snowstorm in Jilin Province in this paper. As shown by the results, for the forecast of Mongolian cyclone location and intensity, EC has significantly higher accuracy than Japanese model and t639, and there is a high likelihood that it forecasts the southerly cyclone location, relatively fast movement and comparatively weak intensity within 72 hours;for snowfall forecast, Japanese model shows significantly higher accuracy than other models, especially it has obviously stronger ability to forecast the heavy rainfall above snowstorm than other models, while WRF model (The Weather Research and Forecasting Model) has strong forecast ability of normal snowfall;for normal snowfall, the 72-hour missing forecast rate is higher than false forecast rate in all the models.