The atmospheric circulation patterns influencing the frequency of spring sand-dust storms in the Tarim Basin

Using NCEP/NCAR reanalysis data and the sand-storm frequency data fi＇om 37 weather stations in the Tarim Basin for the period 1961-2009, the relationship between the frequency of spring sandstorms in the Tafim Basin and the associated atmospheric circu- lation pattems is analyzed in this study. We found significantly negative correlations between sandstorm frequency and the 500-hPa geopotential height over the Paris Basin and midwestem Mongolia, while there were positive correlations over the Ural River region. The rising of the 500-hPa geopotential height in midwestem Mongolia and its falling over the Ural region corre- spond to a weakening of the large-scale wave patterns in the Eurasian region, which directly causes the frequency of the sand-dust storms in the Tarim Basin to decline. Also, the abrupt decline in the spring sandstorm frequency in the Tarim Basin observed in the last half-century is associated with profound changes in the atmospheric circulation in these key regions. At the interannual scale, the strengthened cyclonic atmospheric circulation patterns in the western part of Mongolia and the anticyclonic patterns over the East European plains at 500-hPa geopotential height, are responsible for frequent sandstorm occurrences in the Tarim Basin.

Relationship between thermal anomalies in Tibetan Plateau and summer dust storm frequency over Tarim Basin,China

The dust storm is the most important and frequent meteorological disaster over Tarim Basin, which causes huge damages on local social economics. How to predict the springtime and summertime dust storm oc- currence has become a hot issue for meteorologists. This paper employed the data of dust storm frequency and 10-m wind velocity at 35 stations over Tarim Basin and the reanalysis data from the National Center for Environ- mental Prediction and the National Center for Atmospheric Research （NCEP/NCAR） during 1961-2007 to study the relationship between dust storm frequency （DSF） in summer over Tarim Basin and the thermal anomalies in Tibetan Plateau in May by using the statistical methods, such as Empirical Orthogonal Function （EOF）, correlation and binomial moving average. The results show when negative anomalies in Tibetan Plateau and positive anomalies in its southern region are present along 30~N （the second mode of surface temperature anomalies by EOF decomposition） in May, the time coefficient （PC2） plays an important role in summer DSF variation and has a close relation with the summer DSF at both inter-annual and decadal time scales. When negative anomalies in Tibetan Plateau and positive anomalies are present in its southern region （PC2 in positive phase）, there is an anomalous anticyclone in North China, which weakens the northwest wind and is not beneficial for cold air moving from high latitude to the Tarim Basin, and the circulation pattern is hard to result in dust storm weather. Furthermore, the sea level pressure （SLP） increased over Tarim Basin and the direction of SLP gradient reversed, which resulted in the 10-m wind velocity slowing down, so the DSF decreased. From above all, it can be conclude that the thermal anomalies in Tibetan Plateau in May has important effects on the summertime dust storm frequency over Tarim Basin and the PC2 can be used as a prediction factor for the summertime dust storm occurrence.

Dust Storms in North China in 2002: A Case Study of the Low Frequency Oscillation

The low frequency oscillation in both hemispheres and its possible role in the dust weather storm events over North China in 2002 are analyzed as a case study. Results show that the Aleutian Low is linked with the Circumpolar Vortex in the Southern Hemisphere on a 30-60-day oscillation, with a weak Circumpolar Vortex tending to deepen the Aleutian Low which may be helpful for the generation of dust storm events. The possible mechanism behind this is the inter-hemispheric interaction of the mean meridional circulation, with the major variability over East Asia. The zonal mean westerly wind at high latitudes of the Southern Hemisphere in the upper level troposphere may lead that of the Northern Hemisphere, which then impacts the local circulation in the Northern Hemisphere. Thus, the low frequency oscillation teleconnection is one possible linkage in the coupling between the Southern Hemisphere circulation and dust events over North China. However, the interannual variation of the low frequency oscillation is unclear.

Dynamic Stability Analysis of Caisson Breakwater in Lifetime Considering the Annual Frequency of Severe Storm

In the dynamic stability analysis of a caisson breakwater, most of current studies pay attention to the motion characteristics of caisson breakwaters under a single periodical breaking wave excitation. And in the lifetime stability analysis of caisson breakwater, it is assumed that the caisson breakwater suffers storm wave excitation once annually in the design lifetime. However, the number of annual severe storm occurrence is a random variable. In this paper, a series of random waves are generated by the Wen Sheng-chang wave spectrum, and the histories of successive and long-term random wave forces are built up by using the improved Goda wave force model. It is assumed that the number of annual severe storm occurrence is in the Poisson distribution over the 50-year design lifetime, and the history of random wave excitation is generated for each storm by the wave spectrum. The response histories of the caisson breakwater to the random waves over 50-year design lifetime are calculated and taken as a set of samples. On the basis of the Monte Carlo simulation technique, a large number of samples can be obtained, and the probability assessment of the safety of the breakwater during the complete design lifetime is obtained by statistical analysis of a large number of samples. Finally, the procedure of probability assessment of the breakwater safety is illustrated by an example.

Sand-dust storms in China: temporal-spatial distribution and tracks of source lands

Sand-dust storm is a special natural disaster that frequently occurs in deserts and their surrounding areas. With the data published onSurface Meteorological Monthly Bulletin andSurface Chart during 1971–1996, the temporal-spatial distribution and annual variation of sand-dust storms are analyzed on the basis of the case study of atmospheric processes. Furthermore, the tracks and source areas of sand-dust storms are determined with the aid of GIS. The results show that except some parts of Qinghai Province and Inner Mongolia as well as Beijing, sand-dust storms decrease apparently in time and space in recent decades in China. Sand-dust storms occur most frequently in spring, especially in April. According to their source areas, sand-dust storms are classified into two types, i.e., the inner-source and outer-source sand-dust storms. Most of the outer-source sand-dust storms move along the north and west tracks. The north-track outer-source sand-dust storms always intrude into China across the Sino-Mongolian border from Hami, a city in the eastern part ofXinjiang, to Xilin Gol, a league in Inner Mongolia, while the west-track ones intrude into China from both southern and northern Xinjiang. The source lands of inner-source sand-dust storms concentrate in the Taklimakan Desert and its surrounding areas in southern Xinjiang, southern part of the Junggar Basin in north of Xinjiang, the Hexi Corridor in western Gansu Province, the dry deserts of Inner Mongolia and the Qaidam Basin in Qinghai.

The influence of different underlying surface on sand-duststorm in northern China

In this paper, a quantitative research on the relationship between different underlying surface and sand-dust storm has been made by using 40 years meteorological data of five different types of underlying surface in northern China, which include farmland, grassland, sandland, gobi and salt crust. These metrological data comprise sand-dust storm days and strong wind days. By analyzing, we can find that there are certain correlations between the days of sand-dust storm and strong wind for different underlying surface, which has great influence on sand-dust storm. But there are pronounced differences in different types of underlying surface. The sand-dust storm days of grassland, gobi and salt crust, with smaller interannual variation are obviously less than strong wind days. On the other hand, the sand-dust storm days of farmland and sandland increase evidently, even in many years, are much more than strong wind days. The differences are mainly induced by the influencing mechanism of different underlying surface on sand-dust storm. Grassland, gobi and salt crust with stable underlying surface are not prone to sand-dust storm under strong wind condition. Whereas, the underlying surface of farmland and sandland is unstable, that is easy to induce sand-dust storm under strong wind condition.

Detecting sand-dust storms using a wind-profiling radar

Sand-dust storm is a type of disastrous weather, typically occurring in arid and semi-arid climates. This study selected a region in the hinterlands of the Taklimakan Desert, called the Tazhong region, as the experimental area to quantitatively estimate the particle concentrations of sand-dust storms using the boundary layer wind-profiling radar. We thoroughly studied the radar echo signals and reflectivity factor features during the sand-dust storms. The results indicate that（1） under sand-dust storm conditions, boundary layer wind-profiling radar cannot capture the complete information regarding horizontal wind velocity and direction, but it can obtain the backscattering intensity of sand-dust storms; and（2） during sand-dust storms particle size distributions in the surface layer closely resemble log-normal distributions, with sand-dust particles sizes of 90–100 μm accounting for the maximum particle probability. Retrieved particle size distributions at heights of 600, 800, and 1000 m follow log-normal distributions, and the expected value of particle diameter decreases gradually with increasing height. From the perspective of orders of magnitude, the retrieved results for particle number concentrations and mass concentrations are consistent with previous aircraft-detected results, indicating that it is basically feasible to use boundary layer wind-profiling radar to quantitatively detect the particle concentrations of dust storms.

Evidence of Correlation between High Frequency Geomagnetic Variations and Seismicity in the Caribbean

An analysis between the hourly distribution of earthquakes in three areas of the Caribbean and the high-frequency variations of the geomagnetic field is presented. The number of earthquakes selected for each zone is between 10,000 and 43,000, which guarantees a statistically significant distribution. The hourly distributions of seismicity in all areas show a bay-shape distribution with a significant increase in the number of earthquakes at night, from 11 PM to 5 AM. For example, in eastern Cuba 36.7% of earthquakes occur at that time, representing 11.7% over 25% in the absence of any time preference. Geomagnetic disturbances were compiled from several years to be able to make a statistically significant hourly distribution of their occurrence, being determined by sudden changes in the magnetic field at a short period of 1 minute. In this sense, geomagnetic data were processed between the years 2011-2016, recorded by the geostationary satellite GOES13 and the magnetic ground station SJG in San Juan, Puerto Rico. The result shows a significant correlation between hourly earthquakes distribution and high-frequency geomagnetic variations. The time-varying conductivity response of Earth’s interior also correlates with seismicity. The theory behind this correlation could be related to the piezoelectric phenomena and the electromagnetic force induced when the magnetic field is disturbed.

Sand-dust Storm, Population and Environment in Northwest China

Sand-dust storms are the result of the integrated influences of climate, geography, society and human factors. A theoretical framework is built to explain the coherence of population growth, agriculture change and environmental degradation. On the basis of the analysis of the causes of the sand-dust storm in terms of human factors, a discussion will be given to show that these factors are internally consistent with the theoretical framework. After that, it will look at China's Agenda 21 and try to find relevant measures to reduce such large sand-dust storms happening in Northwest China and eventually make this area develop sustainably.

A Simulation Study on Channel Estimation for Cooperative Communication System in Sand-dust Storm Environment

There are many factors that influence the propagation of electromagnetic wave in the sand-dust storm environment, the scattering effect of dust particle is one of the major factors, so this paper focuses on the dust particles scattering function. The scattering of dust particles inevitably brings the multipath transmission of the signal, multipath propagation will bring the multipath fading of the signal. In this paper, we first investigate the use of AF and DF modes in a sand-dust storm environment. Secondly, we present a low-order modulation method should be used in cooperative communication system. Lastly, we evaluate the system performance for both of the moving nodes and power allocation. Experimental results validate the conclusion of theoretical derivation: the multipath fading is one of the main factors that affect the quality of signal transmission. Cooperative communication technology has good anti-fading ability, which can guarantee the signal transmission timely and correctly.

PROBLEMS CONCERNING SAND-DUST STORMS IN NORTHWEST CHINA

This paper describes an exceptionally severe sand-dust storm that occurred in Northwest China in 1993, and outlines the damage, characteristics and formative factors of the sand-dust storm and the demarcation of its prone zones, laying emphasis on the countermeasures to prevent and reduce such disasters. Finally the authors suggest setting up protective systems for oases and taking action to rehabilitate the blown sand-land on the northern side of the Great Wall on the Loess Plateau.

Seasonal Prediction of Tropical Cyclones and Storms over the Southwestern Indian Ocean Region Using the Generalized Linear Models

Tropical cyclones (TCs) and storms (TSs) are among the devastating events in the world and southwestern Indian Ocean (SWIO) in particular. The seasonal forecasting TCs and TSs for December to March (DJFM) and November to May (NM) over SWIO were conducted. Dynamic parameters including vertical wind shear, mean zonal steering wind and vorticity at 850 mb were derived from NOAA (NCEP-NCAR) reanalysis 1 wind fields. Thermodynamic parameters including monthly and daily mean Sea Surface Temperature (SST), Outgoing Longwave Radiation (OLR) and equatorial Standard Oscillation Index (SOI) were used. Three types of Poison regression models (i.e. dynamic, thermodynamic and combined models) were developed and validated using the Leave One Out Cross Validation (LOOCV). Moreover, 2 × 2 square matrix contingency tables for model verification were used. The results revealed that, the observed and cross validated DJFM and NM TCs and TSs strongly correlated with each other (p ≤ 0.02) for all model types, with correlations (r) ranging from 0.62 - 0.86 for TCs and 0.52 - 0.87 for TSs, indicating great association between these variables. Assessment of the model skill for all model types of DJFM and NM TCs and TSs frequency revealed high skill scores ranging from 38% - 70% for TCs and 26% - 72% for TSs frequency, respectively. Moreover, results indicated that the dynamic and combined models had higher skill scores than the thermodynamic models. The DJFM and NM selected predictors explained the TCs and TSs variability by the range of 0.45 - 0.65 and 0.37 - 0.66, respectively. However, verification analysis revealed that all models were adequate for predicting the seasonal TCs and TSs, with high bias values ranging from 0.85 - 0.94. Conclusively, the study calls for more studies in TCs and TSs frequency and strengths for enhancing the performance of the March to May (MAM) and December to October (OND) seasonal rainfalls in the East African (EA) and Tanzania in particular.

电离层暴时经验模型STORM在中国区域的适应性研究

利用中国区域内9个垂测站1976—1987年一个太阳活动周期的电离层暴时f_0F_2数据,统计分析了电离层暴事件的等级,以及不同等级的电离层暴随季节和地磁纬度的分布特征.研究发现,中小型电离层暴在春秋季发生的概率较大,不同季节的发生次数与地磁纬度具有明显的关系.利用STORM模型对电离层暴时f_0F_2和大型及特大型电离层暴时f_0F_2的预测值与月中值进行了比较.结果表明,除了冬季误差增大外,发生电离层暴时STORM模型能够有效地改善月中值模型.增加中国的暴时数据,并提高对冬季的暴时参数f_0F_2的预测是改善STORM模型的重要因素.建立合适的暴时指数来预测f_0F_2是未来研究的重点.

The Variability of Spring Sand-Dust Storm Frequency in Northeast Asia from 1980 to 2011

The characteristic distributions of regional sand-dust storm （SDS） weather processes over Northeast Asia from 1980 to 2011 were investigated using the shared WMO surface station meteorological data, atmospheric sounding data, China high density weather data, NCEP/NCAR reanalysis data, as well as the archived original weather maps of China. The concentration-weighted trajectory （CWT） method was used to calculate the SDS frequency from the discrete station data and to track the large-scale regional SDS weather processes in Northeast Asia. A spline trend analysis method was employed to investigate the variability of the SDS weather systems. The results show that during 1980-2011, the SDS weather processes exhibit both a historical persistence and abrupt transitions with an approximate 10-yr high-low occurrence oscillation. Through composite analysis of atmospheric circulation during high and low SDS years, it is found that the SDS occurrences are closely related to the anomalies of arctic vortex and midlatitude westerly, and the circulation patterns around the Lake Baikal. During the high frequency years, the meridianal flows in the upper and mid troposphere above the high SDS corridor in East Asia （from the Lake Balkhash along Northwest and North China, Korean Peninsula, meridianal flows during the low SDS frequency years, the midlatitude regions. and Japan Islands） are apparently stronger than the favoring the development and transport of SDSs in the midlatitude regions.

Diurnal and Seasonal Variations of Rain Rate and Rain Attenuation on Ku-Band Satellite Systems in a Tropical Region: A Synthetic Storm Techniques Approach

In this paper, a time-varying rain characterization and diurnal variation in the Ku-band satellite systems simulated with synthetic storm techniques (SST) over a tropical location in Nigeria have been presented. Three years’ rain rate time-series data measured by a raingauge located inside the Federal University of Technology Akure, Nigeria were utilized for the purpose of this work. The analysis is based on the CDF of one-minute rain rate;time-series simulated annual/seasonal and diurnal rain rate, rain attenuation statistics and fade margins observed over four time intervals: 00:00-06:00, 06:00-12:00, 12:00-18:00 and 18:00-24:00. In addition, comparison was also made between the synthesized values and rain attenuation statistics, at 12.245 GHz for a hypothetical downlink from EUTELSAT W4/W7 satellite in the area. It could be observed that at 99.99% link availability, the fade margin as high as ~20 dB may be required at Ku band uplink frequency bands in this area. We also observed that the communication downlinks working in the early morning and early to late in the evening hours must be compensated with an appropriate Down-Link Power Control (DLPC) for optimum performances during severe atmospheric influences in the region.

Ionospheric Effects of Geomagnetic Storms in Different Longitude Sectors

This paper analyzes the state of the ionosphere during two geomagnetic storms of a different intensity evolving in different sectors of local time in different seasons. There were used the data from a network of ionospheric stations located in the opposite longitudinal sectors of 80°-150° E and 250°-310° E.This analysis has permitted us to conclude that the detected differences in the variations of the disturbances are likely to be determined by the local time difference of the geomagnetic storm development, its intensity and by the different illumination conditions of the ionosphere.

The Effects of the Recurrent Storms on Fof2 at Ouagadougou Station during Solar Cycles 21-22

The present paper deals with the effect of recurrent activity on the foF2 diurnal variation at Ouagadougou station for solar cycles 21 and 22. The recurrent activity produces at daytime positive storm for all solar cycle phases. For all seasons, the recurrent activity causes positive storm during nighttime and has no effect during daytime. From this study, it emerges that a positive effect of the storm at this station may be explained by the thermospheric composition changes. Recurrent activity more occurs during the solar decreasing phase and during spring month. The storm strength shows solar cycle phase and seasonal dependence. The storm strength is the highest during the solar increasing phase and during summer months.

华南中小流域设计暴雨洪水同频率检验与重现水平推算

暴雨洪水同频率假定是否成立和暴雨洪水遭遇概率分布是中小流域设计洪水计算的依据,为检验其合理性,采用鉴江上游曹江流域典型强降水流域1967—2013年逐时暴雨洪水观测资料,分析了华南中小流域最大面雨量R和对应场次最大洪峰流量Q的边缘分布和联合分布的遭遇概率,并推算其设计重现水平。研究结果表明:暴雨和洪水同频遭遇概率较小;对于特定设计频率,洪峰流量与流域面雨量的遭遇概率随流域面雨量增大而增大;流域面雨量和洪峰流量的遭遇条件概率显示存在着多种防洪风险管理选择;相对于“或”联合重现期和“且”重现期,二次重现期更准确地反映R-Q组合的风险率。

Possible influence of Arctic Oscillation on dust storm frequency in North China

This study has investigated the influence of Arctic Oscillation （AO） on dust storm frequency in North China in spring seasons during 1961-2007. There is a significant linkage between dust storm frequency and AO; a negative （positive） AO phase is related to an increased （decreased） dust storm frequency in North China. This relationship is closely related to changes in the cold air activity in Mongolia. The cold air activity exerts large impacts on the dust storm frequency; the frequency of cold air activity over Mongolia not only positively correlates with the dust storm frequency in North China, but also shows a long-term decreasing trend that is an important reason for the long-term decreasing of dust storm frequency in North China. The AO has large influence on the frequency of cold air activity over Mongolia; a negative （positive） AO phase is highly related to an increased （decreased） frequency of cold air activity over Mongolia, which results in an increased （decreased） dust storm frequency in North China.

计及多维隐患因素的输变电设备中长期故障率建模方法

随着新能源并网比例的不断提高,电网装备水平和管理模式快速发展,电网的风险管理面临新的不确定因素挑战。本文提出一种计及多维隐患因素的输变电设备中长期故障率建模方法。该方法首先运用头脑风暴法汇总相关业务部门对不同类型设备风险隐患因素的经验化筛选结果,完成设备风险隐患因素的识别,再按照不同的维度对隐患因素进行归类,在对每一个维度的故障频度进行单独建模后,经加权得到设备的中长期故障率。通过西北电网750kV罐式断路器的风险评估案例分析,展示了所提方法的实际应用效果。