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Analysis of a snowfall Process in North China during February 12-13, 2022

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Journal of Geoscience and Environment Protection 2022年第10期10卷 126-143页

作者： Weibo Shan School of Atmospheric Sciences Nanjing University of Information Science and Technology Nanjing China

This research analyzed a snowfall process in north China during February 12-13, 2022. By using synoptic and numerical analysis, it is concluded that this snowfall process was mainly caused by trough, low-level vortex, shear line and Siberian High. Meanwhile, an easterly wind that transports water vapor from the Bohai to North China, was the water resource of the snowfall process. Relative humidity in the low atmosphere was above 80%, providing an excellent humidity condition for snowfall. Positive vorticity and convergence induced upward motion, which offered conditions for snowfall. Numerical reconstruction is also used to show the range and the intensity of the snowfall process.

关键词： Vortex Trough snowfall Numerical Reconstruction

Environmental factors influencing snowfall and snowfall prediction in the Tianshan Mountains, Northwest China

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Journal of Arid Land 2019年第1期11卷 15-28页

作者： ZHANG Xueting LI Xuemei LI Lanhai ZHANG Shan QIN Qirui Faculty of Geomatics Lanzhou Jiaotong University Gansu Provincial Engineering Laboratory for National Geographic State Monitoring State Key Laboratory of Desert and Oasis Ecology Xinjiang Institute of Ecology and Geography Chinese Academy of Sciences

snowfall is one of the dominant water resources in the mountainous regions and is closely related to the development of the local ecosystem and economy. snowfall predication plays a critical role in understanding hydrological processes and forecasting natural disasters in the Tianshan Mountains, where meteorological stations are limited. Based on climatic, geographical and topographic variables at 27 meteorological stations during the cold season(October to April) from 1980 to 2015 in the Tianshan Mountains located in Xinjiang of Northwest China, we explored the potential influence of these variables on snowfall and predicted snowfall using two methods: multiple linear regression(MLR) model(a conventional measuring method) and random forest(RF) model(a non-parametric and non-linear machine learning algorithm). We identified the primary influencing factors of snowfall by ranking the importance of eight selected predictor variables based on the relative contribution of each variable in the two models. Model simulations were compared using different performance indices and the results showed that the RF model performed better than the MLR model, with a much higher R^2 value(R^2=0.74; R^2, coefficient of determination) and a lower bias error(RSR=0.51; RSR, the ratio of root mean square error to standard deviation of observed dataset). This indicates that the non-linear trend is more applicable for explaining the relationship between the selected predictor variables and snowfall. Relative humidity, temperature and longitude were identified as three of the most important variables influencing snowfall and snowfall prediction in both models, while elevation, aspect and latitude were of secondary importance, followed by slope and wind speed. These results will be beneficial to understand hydrological modeling and improve management and prediction of water resources in the Tianshan Mountains.

关键词： snowfall prediction snowfall fraction random forest multiple linear regression predictor variables Tianshan Mountains

Numerical Study on Microphysical Processes of Two Different snowfall Cases in Northern China

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Acta meteorologica Sinica 2007年第4期21卷 420-437页

作者：孙晶王鹏云李想逯莹 Institute of Atmospheric Physics Chinese Academy of Sciences Chinese Academy of Meteorological Sciences Shuangyashan Meteorological Bureau of Heilongjiang Province

In this paper, two snowfall cases under different weather conditions in northern China are simulated by using the meso scale model MM5. Two-way nesting structure of domains is designed for each case. Among the explicit schemes of MM5, the Reisner graupel scheme is selected to describe the microphysical process. The simulated snow-bands of two cases are basically consistent with observations. The simulated results of microphysical processes are mainly discussed. The hydrometeors and their sources and sinks under different weather backgrounds are described. The feedback effects of microphysical processes on the thermal and dynamic processes are also discussed. Method that outputs the accumulative sources and sinks per hour is used to analyze the distribution characteristics of hydrometeors during the strongest snowfall period. Two sensitivity tests （called heat test and drag test） are conducted to examine the effects of microphysical processes on cloud produced by the latent heat and drag force. Results have shown that the distribution of particles has a close relation with temperature. The temperature of Beijing snowfall is under 0℃ and there exist vapor and solid phase particles, while Liaoning snowfall has vapor, liquid, and solid phase particles due to the warm temperature. The distribution of these particles is not the same at different development stages. From the analyses of the characteristics of sources and sinks, it is found that snow is mainly produced by the deposition and accretion with ice. Cloud water is crucial to graupel. The melting of ice-phase particles enhances the rain production. The results of heat tests and drag tests reveal that the microphysical processes have interacted with the dynamic and thermal processes. Latent heat release of hydrometeors feeds back positively on snowfall while the drag force not. At last, comparisons of simulated results have been done between the two different kinds of snowfall cases. The microphysical processes o

关键词： snowfall mesoscale model MM5 microphysical process sources and sinks

Analysis of a Beijing Heavy snowfall Related to an Inverted Trough in November 2009

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Atmospheric and Oceanic Science Letters 2010年第3期3卷 127-131页

作者： LI Jin ZHAO Si-Xiong and YU Feil Iustinate of Aomospherc Phyrics Chinese Acadeny of SciencesBeying 100029.China Gradtuate Unrversiy of the Chinese Academy of Seience Bejing 100049China Beijing Weather Office Beijing 100089China

This paper studies a heavy snowfall in Beijing that took place on 1 November 2009. The date of the snowfall was about one month earlier than the average. The National Centers for Environmental Prediction (NCEP) reanalysis data, conventional data, and Automatic Weather Station (AWS) data are utilized to explore the reasons for the snowfall and the influencing systems. The main conclusions are as follows: (1) It is revealed from the average geopotential height and average temperature fields at 500 hPa that the large scale circulation in November 2009 was favorable to snowfall. The cold-dry air from West Siberia and the warm-moist air from the Bay of Bengal converged in North China. In addition, it was found from the average moisture flux field at 700 hPa that the main water vapor source was in the Bay of Bengal. (2) Not only the "return current", as usually accepted, but also the inverted trough on the current had an important contribution to the snowfall. The inverted trough could produce the obvious upward motion that is an important environmental condition of snowfalls. (3) More attention should be paid to mesoscale systems such as mesolows during the cold season because of their importance, though they do not occur as frequently as in the warm season. It should be pointed out that AWS data are very useful in mesoscale system analysis during both warm and cold seasons.

关键词： cold wave snowfall precipitation type inverted trough mesolow

RESEARCH ON MOIST SYMMETRIC INSTABILITY IN A STRONG snowfall IN NORTH CHINA

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Acta meteorologica Sinica 1995年第4期9卷 456-467页

作者：王建中丁一汇 Chinese Academy of Meteorological Sciences Beijing 100081

The concept of wet bulb potential vorticity and SCAPE (slantwise convective available potential energy) is used to calculate the horizontal and vertical distribution of moist symmetric instability including convective symmetric instability (CSI) and local symmetric instability (LSI) in the process of a storm snowfall in North *** potential contribution of moist symmetric instability to a narrow storm snowfall belt occurring in the Hetao and Lindong,Linxi region of Inner Mongolia and the relationship between moist symmetric instability and direction of the basic flow,wind shear and moisture are *** is found that the strong snowfall belt is almost parallel with negative value area of wet bulb potential vorticity at low levels in the vicinity of snow *** the dynamical mechanism of the strong snowfall center in the Lindong,Linxi region is different from that in the Hetao *** former is induced by frontogenetical forcing with weak symmetric instability in the warm section of frontal area and the latter triggered by obvious moist symmetric instability.

关键词： snowfall mesoscale moist symmetric instability(MSI)

snowfall Shift and Precipitation Variability over Sikkim Himalaya Attributed to Elevation-Dependent Warming

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Journal of Atmospheric Science Research 2023年第4期6卷 1-25页

作者： Pramod Kumar Khushboo Sharma Department of Geology Sikkim UniversityTadongGangtokSikkim737102India

Sikkim Himalaya hosts critical water resources such as glacial,rain,and snow-fed springs and *** change is adversely affecting these resources in various ways,and elevation-dependent warming is prominent among *** study is a discussion of the elevation-dependent warming(EDW),snowfall shift,and precipitation variability over Sikkim Himalaya using a high-resolution ERA5-land ***,the findings show that the Sikkim Himalaya region is experiencing a warming trend from south to *** majority of the Sikkim Himalayan region shows a declining trend in snowfall.A positive advancement in snowfall trend(at a rate of 1 mm per decade)has been noticed above 4500 *** S/P ratio indicates a shift in snowfall patterns,moving from lower elevations to much higher *** suggests that snowfall has also transitioned from Lachung and Lachen(3600 m)to higher elevated ***,the seasonal shifting of snowfall in the recent decade is seen from January-March(JFM)to February-April(FMA).Subsequently,the preceding 21 years are being marked by a significant spatiotemporal change in temperature,precipitation,and *** potent negative correlation coefficient between temperature and snowfall(–0.9),temperature and S/P ratio(–0.5)suggested the changing nature of snowfall from solid to liquid,which further resulted in increased lower elevation *** entire Sikkim region is transitioning from a cold-dry to a warm-wet weather *** the climate change scenario,a drop in the S/P ratio with altitude will continue to explain the rise in temperature over mountainous regions.

关键词： Sikkim Himalaya EDW snowfall Seasonal shift Precipitation variability S/P ratio ERA5-land

Diagnostic Analysis of a snowfall Weather in Beijing,Tianjin and Hebei in 2010

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Meteorological and Environmental Research 2012年第1期3卷 32-35,40页

作者： ZHOU He-ling CHEN Min Langfang Meteorological Bureau in Hebei Province Langfang 065000China

[ Objective] The research aimed to analyze a local snowstorm weather process which happened in Beijing, Tianjin and Hebei during I - 4 January, 2010. [ Method] Based on routine meteorological observation data and NCEP/NCAR 2.5° ×2.5° grid data （four times every day）, a lo- cal snowstorm weather process which happened in Beijing, Tianjin and Hebei during 1 -4 January, 2010 was carried out diagnostic analysis by using composite analysis method. [Result] Circumfluence on the ground and strong cold advection in the rear of upper trough were the main weath- er system of the snowfall. The deep thick wet layer and strong water vapor convergence provided sufficient water vapor for snowfall. The divergence field of low-level convergence and high^level divergence, dynamic coupling effect of vorticity provided favorable dynamic condition upwardly for the occurrence of strong snowfall. The steep dense area of Oso, low temperature at the ground layer and inversion temperature at the high layer provided certain energy condition for the development of snowfall weather. [ Conclusion] The research provided theoretical basis for snowfall forecast in future.

关键词： snowfall Physical quantity Diagnostic analysis Beijing, Tianjin and Hebei China

Comparative Analysis of Two snowfall Weather Processes at Nanjing Airport in Early 2022

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Meteorological and Environmental Research 2022年第6期13卷 14-21页

作者： Xiaoyin YANG Xin YU Spring Airlines Shanghai 200050China 66199 Unit of PLA Beijing 100144China

In early 2022,two snowfalls of different magnitudes occurred in southern Jiangsu and Anhui,which had different impacts on the operation of Nanjing *** on NCEP reanalysis data and the WRF3.9 model,the weather condition and the physical quantity fields of two different situations were mainly compared and *** results show that the snowstorm occurred in the left front of the low-level jet stream and in the wind speed convergence area of the 700 h Pa shear *** reasonable configuration of the convergence area of the water vapor flux divergence and the rising motion field can be regarded as an important reason for the occurrence of the *** the comparative analysis of these two snowfalls of different magnitudes,the focus of the short-term forecast of heavy snowfall at Nanjing Airport was preliminarily drawn:the 0℃line at 700 h Pa basically pressed southward to the south of 31°N,and the 0℃line at 850 h Pa pressed southward to the south of 30°*** temperature was≤0℃,and temperature at 925-800 h Pa was≤-3 or-4℃;temperature at 700 h Pa was<0℃,and there was temperature inversion in the middle and lower *** the model forecast output field,the proportion of the mixing ratio of frozen precipitation in the near-surface atmosphere to the mixing ratio of water vapor that can condense into precipitation is very important,and can be used to determine the evolution of rain and snow boundaries and sleet areas or the south of rain and snow transition zone and precipitation phase.

关键词： snowfall Physical quantity field Comparative analysis

Five different types of lowered snow line in alpine valleys

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Journal of Mountain Science 2022年第1期19卷 73-84页

作者： Danijela STRLE Matej OGRIN Department of Geography University of LjubljanaLjubljana 1000Slovenia

The snow line for the same precipitation event in alpine valleys can vary greatly from valley to valley, even when the valleys are close together. Often this is not due to a difference in air mass, but to a different interaction of topography and topographyrelated meteorological conditions. By knowing the causes of a lowered snow line, we can better understand the differences in snow cover in alpine valleys at the same elevation over short distances or the differences in snow cover between alpine valleys and areas outside the valleys. As different types of lowered snow line respond differently to climate change, we can also understand future changes in snow conditions in alpine valleys. To better understand the process, we observed the temperature conditions during winter precipitation events on the territory of Eastern Julian Alps(Slovenia) over a period of two years, focusing on the height of the zero isotherm. Depending on atmospheric conditions, especially changes in the temperature profile and precipitation intensity during precipitation events, five causes of lowered snow line have been identified. These types can occur individually, but during multi-day snowfall events they occur frequently or in combination.

关键词： Latent cooling snowfall Topoclimate Mountain valleys Local climate Julian Alps