Evaluating the impact and significance of meteorological factors upon dust storm occurrence

In this article, the quantitative impact and significance of factors on dust storm occurrence have been analyzed in detail, based on spring daily data sets of 17 meteorological factors and dust storm records during the period of 1954–2005 for 60 gauge stations distributed over Gansu Province of China. Results show that daily mean and maximum wind speeds and evaporation have a positive effect on dust storm occurrence, i.e., their increase can result in an increase of dust storm occurrence. Inversely, daily mean and minimum relative humidity, lowest surface air pressure, vapor pressure and number of sunny hours have a negative effect on dust storm occurrence. However, daily mean and highest surface air pressure; mean, highest and lowest surface air temperature; and precipitation of 20:00–08:00, 08:00–20:00 and 20:00–20:00 have a positive effect on dust storm occurrence in some places but negative in other places. On average, daily maximum and mean wind speeds, direction of the maximum wind, number of sunny hours and evaporation have a significant effect on dust storm occurrence in Gansu Province, but precipitation of 20:00–08:00, 08:00–20:00 and 20:00–20:00, and mean surface air pressure and temperature all have a minor influence upon dust storm occurrence.     

塔克拉玛干沙漠沙尘演变及气候因素分析

Based on the sand dust storms data and climatic data in 12 meteorological stations around sand dust storm originating areas of the Taklimakan Desert, we analyzed the trends of the number of dust storm days from 1960 to 2005 as well as their correlations with temperature, precipitation, wind speed and the number of days with mean wind speed 〉 5 m/s. The results show that the frequency of dust storm events in the Taklimakan region decreased with the elapse of time. Except Ruoqiang and Minfeng, in the other 10 meteorological stations, the frequency of dust storm events reduces, and in 4 meteorological stations of Kuqa, Korla, Kalpin and Hotan, the frequency of dust storm events distinctly decreases. The temperature has an increasing trend, while the average wind speed and the number of days with mean wind speed ≥ 5 m/s have decreasing trends. The correlation analysis between the number of days of dust storms and climatic parameters demonstrates that wind speed and the number of days with mean wind speed 〉 5 m/s have strong positive correlation with the number of days of dust storms, with the correlations coefficients being 0.743 and 0.720 （p〈0.01）, respectively, which indicates that strong wind is the direct factor resulting in sand dust storms. Whereas precipitation has significant negative correlation with the number of days of dust storms （p〈0.01）, and the prior annual precipitation has also negative correlation, which indicates that the prior precipitation restrains the occurrence of sand dust storms, but this restraining action is weaker than the same year＇s precipitation. Temperature has negative correlation with the number of dust storm days, with a correlations coefficient of -0.433 （p〈0.01）, which means that temperature change also has impacts on the occurrence of dust storm events in the Taklimakan region.     

Analyses of spring mean circulations for major and minor dust storm years in China–Mongolia area

To better understand the dust storm (hereafter DS) inducing circulation in the China–Mongolia (CM) DS activity area, the spring mean circulation features and differences on lower levels in three subregions of the CM DS area for the major- and minor-DS years have, as a whole (not partly), been analyzed, utilizing the National Centers for Environmental Prediction and the National Center for Atmospheric Research (NCEP/NCAR) reanalyzed gridded data, the observed DS frequency data in the CM area, and the composite analysis method. The main conclusions are as follows: (1) Judging from the differences in the DS-inducing systems, dust origins, paths of invading cold air, and main DS-strike areas, the whole CM DS area is roughly divided into the three subregions: the East-, Middle- and West-CM subregions (in this paper, referred to as E-, M-, and W-CM). (2) In major DSs during spring over the E-CM, the middle- and lower-level troughs or cyclones over the Japan Sea and northeastern China (NEC) dominate. The invading cold air along the northeastern (NE) or north by east (NE) path often causes the DS in the E-CM region. But nearly the opposite is true in minor DS during spring in E-CM. (3) In the major DS during spring over the M-CM region, the Mongolian troughs or cyclones are the main DS-inducing systems. The strong invading cold air along the northwestern (NW)- or north by west (Nw) path causes the DSs in the M-CM region. (4) In the major DSs during spring over the W-CM region, the South Xinjiang heat lows prevail, the intruding cold air has a western path, and creates the DSs in South Xinjiang. (5) In the past 50 years, the DSs over the M-CM region have had the most severe impact on the preceding three subregions of the CM DS area. Overall, DS activities over all of three regions of the CM area decreased in the past (particularly, over M- and W-CM regions since the mid-1980s. But there existed a short and sudden increasing in E-CM in the years 2000–2002. (6) It is circulation changes and desertification evolutions that cause the yearly and decadal changes of DS in CM area, especially the former. With the backdrop of global warming in the future, perhaps the decreased DS activities over M- and W-CM will persist for some time again, and special attention should be paid to ones over E-CM or to the individual DS events over M- and W-CM.     

1960-2012年内蒙古寒潮时空变化特征(英文)

In this study, we analyzed the spatiotemporal variation of cold surges in Inner Mongolia between 1960 and 2012 and their possible driving factors using daily minimum temperature data from 121 meteorological stations in Inner Mongolia and the surrounding areas. These data were analyzed utilizing a piecewise regression model, a Sen+MannKendall model, and a correlation analysis. Results demonstrated that(1) the frequency of single-station cold surges decreased in Inner Mongolia during the study period, with a linear tendency of –0.5 times/10a(–2.4 to 1.2 times/10a). Prior to 1991, a significant decreasing trend of –1.1 times/10a(–3.3 to 2.5 times/10a) was detected, while an increasing trend of 0.45 times/10a(–4.4 to 4.2 times/10a) was found after 1991. On a seasonal scale, the trend in spring cold surges was consistent with annual values, and the most obvious change in cold surges occurred during spring. Monthly cold surge frequency displayed a bimodal structure, and November witnessed the highest incidence of cold surge.(2) Spatially, the high incidence of cold surge is mainly observed in the northern and central parts of Inner Mongolia, with a higher occurrence observed in the northern than in the central part. Inter-decadal characteristic also revealed that high frequency and low frequency regions presented decreasing and increasing trends, respectively, between 1960 and 1990. High frequency regions expanded after the 1990 s, and regions exhibiting high cold surge frequency were mainly distributed in Tulihe, Xiao’ergou, and Xi Ujimqin Banner.(3) On an annual scale, the cold surge was dominated by AO, NAO, CA, APVII, and CQ. However, seasonal differences in the driving forces of cold surges were detected. Winter cold surges were significantly correlated with AO, NAO, SHI, CA, TPI, APVII, CW, and IZ, indicating they were caused by multiple factors. Autumn cold surges were mainly affected by CA and IM, while spring cold surges were significantly correlated with CA and APVII.     

2001-2013年华北地区植被覆盖度与干旱条件的相关分析（英文）

Climate change is one of the most important factors that affect vegetation distribution in North China. Among all climatic factors, drought is considered to have the most significant effect on the environment. Based on previous studies, the climate drought index can be used to assess the evolutionary trend of the ecological environment under various arid climatic conditions. It is necessary for us to further explore the relationship between vegetation coverage(index) and climate drought conditions. Therefore, in this study, based on MODIS-NDVI products and meteorological observation data, the Palmer Drought Severity Index(PDSI) and vegetation coverage in North China were first calculated. Then, the interannual variations of PDSI and vegetation coverage during 2001–2013 were analyzed using a Theil-Sen slope estimator. Finally, an ecoregion perspective of the correlation between them was discussed. The experimental results demonstrated that the PDSI index and vegetation coverage value varied over different ecoregions. During the period 2001–2013, vegetation coverage increased in the southern and northern mountains of North China, while it showed a decreasing trend in the Beijing-Tianjin-Tangshan City Circle area and suburban agricultural zone located in Hebei Province and Henan Province). Over 13 years, the climate of the northeastern part of North China became more humid, while in the southern part of North China, it tended to be dry. According to the correlation analysis results, 73.37% of North China showed a positive correlation between the vegetation coverage and climate drought index. A negative correlation was observed mainly in urban and suburban areas of Beijing, Tianjin, Hebei Province, and Henan Province. In most parts of North China, drought conditions in summer and autumn had a strong influence on vegetation coverage.     

Simulation on the spatio-temporal distribution and emission flux of dust aerosol over East Asia in 2000–2009

A regional climate model (RegCM3), coupled with an online dust module, is used to simulate the spatio-temporal distribution and emission flux of dust aerosol (smaller than 20 μm in diameter) over East Asia in the period from 2000 to 2009. The model performance is firstly evaluated against available observations. Simulation results show that the model can capture the characteristics of spatio-temporal distribution of dust aerosol very well over East Asia. There always exist two extremes of dust aerosol optical depth (AOD) and column burden (CB), one is in the Taklimakan Desert of Xinjiang Uygur Autonomous Region, China, and the other is in the Badain Jaran Desert of Inner Mongolian Autonomous Region, China. The maximum value of CB appears in spring, secondary maximum in winter and minimum in autumn. To the east of 110°E, dust is transported eastward from a maximum center at a height of 700 hPa over the East Asian continent. Dust emission sources are mainly located in the Taklimakan Desert, Badain Jaran Desert, North Qinghai-Tibetan Plateau and Southwest Mongolia. There is also an obvious seasonal variation of dust emission flux (EF). Annual mean dust EF is 1,015.34 mg/(m 2 ·d), of which 62.4% and 2.3% are re-deposited onto the East Asian continent through a dry and wet deposition process, respectively, and the remaining 35.3% is injected into the atmosphere or subject to long-range transport.     

Distribution of winter-spring snow over the Tibetan Plateau and its relationship with summer precipitation in Yangtze River

The distribution of winter-spring snow cover over the Tibetan Plateau(TP) and its relationship with summer precipitation in the middle and lower reaches of Yangtze River Valley(MLYRV) during 2003–2013 have been investigated with the moderate-resolution imaging spectrometer(MODIS) Terra data(MOD10A2) and precipitation observations. Results show that snow cover percentage(SCP) remains approximately 20% in winter and spring then tails off to below 5% with warmer temperature and snow melt in summer. The lower and highest percentages present a declining tendency while the middle SCP exhibits an opposite variation. The maximum value appears from the middle of October to March and the minimum emerges from July to August. The annual and winter-spring SCPs present a decreasing tendency. Snow cover is mainly situated in the periphery of the plateau and mountainous regions, and less snow in the interior of the plateau, basin and valley areas in view of snow cover frequency(SCF) over the TP. Whatever annual or winter-spring snow cover, they all have remarkable declining tendency during 2003–2013, and annual snow cover presents a decreasing trend in the interior of the TP and increasing trend in the periphery of the TP. The multi-year averaged eight-day SCP is negatively related to mean precipitation in the MLYRV. Spring SCP is negatively related to summer precipitation while winter SCP is positively related to summer precipitation in most parts of the MLYRV. Hence, the influence of winter snow cover on precipitation is much more significant than that in spring on the basis of correlation analysis. The oscillation of SCF from southeast to northwest over the TP corresponds well to the beginning, development and cessation of the rain belt in eastern China.     

Radiative forcing and temperature response of dust aerosols over East Asia in the latest decade

A regional climate model, RegCM3, coupled with an online dust module, is used to simulate the radiative forcing (RF) and temperature response of dust aerosols over East Asia in the latest decade (2000–2009). The simulation results show that the geographical and seasonal differences of dust aerosols distribution over East Asia are obvious. There exist two extremes of dust aerosols with column burden (CB) greater than 1,000 mg/m²; one is in the Taklimakan Desert of the Xinjiang Uigur Autonomous Region, China, and the other is in the Badain Jaran Desert of the Inner Mongolian Autonomous Region, China. The maximum value of CB appears in spring, the secondary maximum in winter, and the minimum in autumn. The RF of dust aerosols has distribution characteristics similar to CB. The regional averaged RF over East Asia at the top of atmosphere (TOARF) is ?1.72 W/m² in spring and ?1.17 W/m² in autumn, and that at the surface (SURRF) is ?4.34 W/m² in spring and ?2.33 W/m² in autumn. The temperature at the surface is decreased by dust aerosols; the regional averaged temperature decrease over East Asia is 0.154 °C in spring and 0.085 °C in autumn. There are different impacts of dust aerosols on air temperature at different heights. The air temperature is decreased by dust aerosols in the lower troposphere, but the extent of the decrease diminishes with increasing height. The air temperature is in fact increased by dust aerosols at the height of 300–400 hPa in spring, which is greatly different from that in autumn.     

西南地区冬季气温和降水的时空变化

In recent years,the socio-economic impacts of winter extreme climate events have underscored the importance of winter climate anomalies in Southwest China (SWC).The spatio-temporal variability of surface air temperature (SAT) and precipitation in SWC and their possible causes have been investigated in this paper based on observational data from 1961 to 2010.The results indicate that SAT anomalies in SWC have two dominate modes,one is homogenous,and the other a zonal dipole.The former is caused by the anomalies of East Asian winter monsoon;the latter arises from the anomalies of both subtropical west Pacific high and regional cold air in lower troposphere.The most dominant mode of precipitation anomalies in SWC is homogenous and it has a high correlation with northern hemisphere annular mode (NAM,AO).Neither NAM nor ENSO has significant impacts on SAT in SWC.The anomalies of NAM are associated with the anomalies of tropical circulations,and there-fore precipitation over the SWC.When NAM is in positive (negative) phase,the winter pre-cipitation is more (less) than normal in SWC.Winter precipitation increase over the whole SWC is associated with the El Nino.However,during La Nina winter,the pattern is not uni-form.There is an increase in precipitation over the central parts and a decrease in western and eastern parts of SWC.The severe drought in SWC in winter 2010 is more likely caused by anomalies of NAM,not El Nino.     

春季天气变率对华北沙尘暴频次的影响

利用欧洲中期数值天气预报中心再分析资料及地面台站观测资料,分析华北春季沙尘暴日数与500 hPa月平均环流及与近地面环流天气变率长期变化的关系,分析时段为1962~2000年。研究发现华北地区春季沙尘暴频次与东亚地区中高纬度500 hPa高度场有显著的负相关,相关中心区在蒙古国及西伯利亚一带,这可能说明高空环流场在这种形势下易于造成高纬度冷空气南下,因此使得华北沙尘暴频次增加。天气过程是形成沙尘暴的直接原因,东亚地区天气变率存在明显的年际和长期变化,研究发现天气变率与沙尘暴频次之间有非常显著的关系：当天气尺度变率增大 (减少) 时,沙尘暴频次也增加 (减少)。其中具体分析了850 hPa低压和地面冷高压活动与沙尘暴的关系,发现东北低压及自蒙古和西伯利亚南下的冷空气活动都对华北沙尘暴频次有明显的影响。近40年来东亚天气变率有显著的减弱趋势,这也在很大程度上解释了沙尘暴频数的显著减少。另外,北极涛动对东亚天气变率和华北沙尘暴频次的年际变化也有一定的影响,北极涛动强的年份华北沙尘暴次数偏少。     

北极涛动异常对西北地区东部沙尘暴频次的影响

利用西北地区东部沙尘暴日数资料、北极涛动指数资料、东亚高低空大气环流形势场资料,分析了沙尘暴日数与北极涛动的关系,进而研究了北极涛动异常年东亚大气环流分布特征,探讨了北极涛动影响西北地区东部沙尘暴的可能途径。结果表明：西北地区东部沙尘暴频次呈波动减少之势,20世纪80年代中期发生气候突变;北极涛动指数与西北地区东部沙尘暴频次显著负相关,二者年际、年代际变化都有较好的应关系,北极涛动正位相年,西北地区东部沙尘暴偏少,反之亦然。究其原因：北极涛动异常对东亚冬季风强度、东亚高低空气压场、风场分布形势有重要影响：北极涛动正位相年,东亚冬季风、蒙古高压均偏弱;500 hPa高度场上,春季西风带纬向环流占优势,极涡面积偏小,强度偏弱,贝加尔湖阻塞高压异常强盛,蒙古国及我国华北和西北地区位于贝加尔湖阻塞高压底部的暖区里,地面至高空西北风偏弱;在这种形势下,整个中高纬度冷空气势力较弱,活动次数偏少,不利于大风、寒潮天气的发生,因此沙尘暴频次也偏少。而北极涛动负位相年基本相反。     

中国北方沙尘暴现状及对策

中国北方主要包括:甘肃河西走廊及内蒙阿拉善盟;新疆塔克拉玛干沙漠周边地区;内蒙阴山北坡及浑善达克沙地毗邻地区和蒙陕宁长城沿线四个主要沙尘暴中心和源区。我国沙尘暴从20世纪50年代以来呈波动减少之势,90年代在减少中有回升,2000年和2001年更是急剧增加,预示着新一轮沙尘暴活跃期已经开始。生态环境恶化和气象条件的变化是我国北方沙尘暴增多的原因。目前人类控制天气的能力还很有限,减缓沙尘暴灾害频度与强度的关键在于搞好地面的生态保护与建设。坚持"预防为主、保护优先、防治并重"的生态保护与建设方针;建立和完善生态保护的法规和政策体系,停止导致生态环境继续恶化的一切生产活动,对于超出生态承载能力的地区可以采取一定的生态移民措施。     

一次强沙尘暴活动对中国城市空气质量的影响

对2006年4月8—12日发生在中国北方地区的一次强沙尘暴天气过程及其对中国大陆城市空气质量的影响进行了分析研究。结果表明：①造成此次沙尘天气过程的直接原因是伴随着西伯利亚强冷空气南下的冷锋自西北向东南方向的移动。沙尘暴鼎盛时期卫星观测的中国境内大气沙尘气溶胶指数（AI）的分布存在一个高值区和两个次高值区。高值区位于内蒙古西部地区、河西走廊和河套地区;两个次高值区分别位于塔克拉玛干沙漠及华北至东北地区。与此同时,地面观测的最小能见度小于10 km的气象站点分布最密集的地区也主要分布在上述3个区域。AI的分布与最小能见度的分布之间有着很好的一致性。②这次沙尘天气过程的影响范围主要在33°N以北。从西到东沙尘天气影响的程度逐渐减轻,受污染最严重的城市集中在西北地区东部。根据锋面过境时间与发生大气污染事件时间的对比可将受沙尘天气影响的城市大致分为两类：第一类城市大气污染事件发生在冷锋过境期间（Ⅰ类城市）,第二类城市大气污染事件发生在冷锋过境前（Ⅱ类城市）。Ⅰ类城市受沙尘过程影响发生空气污染事件的持续时间相对较短,空气污染事件主要出现在锋面过境前后。Ⅱ类城市受沙尘过程影响发生空气污染事件的持续时间相对较长,空气污染事件的出现时间要明显超前于锋面过境时间。两类城市的共同特征是能见度与空气污染指数（API）之间存在着良好的反位相关系。     

东亚沙尘区域时空变化特征分析

沙尘天气是东亚地区常见的灾害性天气之一,强沙尘天气的发生不仅导致建筑物倒塌、人畜伤亡、植被破坏,还会导致火灾、空气污染等环境问题,对人体健康、社会经济活动及其全球沙尘循环产生重要影响。然而从东亚地区沙尘天气在长时间序列区域特征角度上系统分析的研究较少。基于此,本文利用1981—2019年东亚地区697个地面气象站点沙尘数据,分析了其区域时空分布特征。结果表明：空间上,东亚沙尘天气集中在位于内陆干旱区的蒙古国和中国西北地区,其中弱沙尘天气集中在中国北方地区,而强沙尘天气则集中在蒙古国。月变化上,东亚沙尘天气集中在春季（3—5月份）,在相对低纬度的中国青藏高原北麓沙尘天气3月份最多,位于中纬度的中国北方大部分地区4月份最多,而较高纬度的哈萨克斯坦东部和蒙古国5月份最多。年际变化上,40a间东亚沙尘呈减少趋势,尤其是在2000年之后多项生态工程的有效实施下中国北方大部分区域沙尘天气显著减少,但近几年内蒙古中西部地区强沙尘天气呈增长趋势;在生态环境较脆弱的蒙古国和塔克拉玛干沙漠等区域弱沙尘天气和强沙尘天气均呈增长趋势。本研究对准确地掌握东亚沙尘分布特征和防范沙尘灾害具有重要意义。     

冷锋型和蒙古气旋型沙尘天气过程典型个例对比分析

利用观测资料和NCEP再分析资料,对冷锋型和蒙古气旋型两类沙尘天气过程的典型个例进行对比分析。结果表明:斜压强迫在两类过程中均较为显著,冷锋型沙尘天气过程中,随高度降低高空槽明显加深;蒙古气旋型则在对流层低层（850 hPa）、中层（500 hPa）形成切断低压。冷锋型沙尘天气过程高空锋区位置较蒙古气旋型偏南,且南压更为明显;冷锋型沙尘天气过程沙尘天气区位置也较蒙古气旋型偏南,且主要向东南方向扩展。冷锋型地面高、低压强度对比明显大于蒙古气旋型,且地面风速与能见度的反相关性高于蒙古气旋型,锋后降温也较蒙古气旋型显著。冷锋型锋前上升运动中心位于700 hPa,锋后下沉运动中心位于600 hPa。蒙古气旋型气旋中心及其附近300 hPa以下均有强的上升运动。冷锋型锋面附近正涡度随高度增高而增大,蒙古气旋型气旋中心及其附近为正涡度。最后给出了冷锋型和蒙古气旋型沙尘天气过程的天气学概念模型。     

从沙尘暴变化趋势看全球气候变化

近年来人们对全球气候变化的问题尤为关注,因为,如今气候变化不仅仅是科学问题、环境问题,还是一个国际政治问题、经济问题,事关社会的长远发展.本研究以沙尘暴为切入点,在前人研究的基础上,总结了近年来沙尘暴及沙尘天气发生频率的变化趋势及其地域性差异,并进一步讨论了沙尘暴发生频率变化趋势与温度变化的响应机制,认为沙尘暴发生频率变化与气温变化呈负相关关系.近年来中国沙尘暴发生频率呈整体下降趋势,表明近年来中国气温有整体升高的趋势,这可能是全球变冷大趋势中的次级波动.     

我国北方春季沙尘暴与气候因子之关系

利用我国北方1954—2005年470个站点的春季沙尘暴资料和相应的气候资料,在合理区划沙尘暴易发地区的基础上,采用气象统计分析中的相关分析方法,对沙尘暴与气温、降水量、相对湿度、地温、风速、风蚀指数等气候因子间的相关性进行了统计分析,研究各个区域沙尘暴发生的气候特征,并提出了春季沙尘暴多发的简单气候概念模型。结果表明:①气候要素与我国北方春季沙尘暴的发生有一定的耦合关系,南疆的沙尘暴与气候要素的相关性最好,而北疆的最差。与沙尘暴相关性最好的气候因子是风速,其次是风蚀指数。②我国北方春季沙尘暴多发的简单的气候概念模型:前期（前冬）,北、南疆地区较常年多干冷的西北气流;青藏东南地区和柴达木地区多暖湿的西南气流;河西地区、河套地区和东北地区为冷湿的偏西气流偏多。同期（春季）,北、南疆地区较往年干燥且多大风;青藏东南地区和柴达木地区暖干;河西地区、河套地区和东北地区冷且多大风。     

2021年3月中旬东亚中部沙尘天气地面起尘量及源区贡献率估算

2021年3月中旬,东亚中部包括中国北方大部分地区,爆发了持续性的沙尘天气,引发了人们对于沙尘源区、防风固沙生态建设工程效益的高度关注.提出了一个新的地表起尘量估算方法,使用高精度、大范围的气象数据,计算了这次沙尘天气的地面起沙条件、大风过程中的输沙状况,估算了不同时刻的起尘量,获得了14、15日蒙古和中国北方荒漠地区...     

华北农牧交错带冬季降雪时空变化特征

基于华北农牧交错带冬季227个台站（1961-2012年）逐日降雪资料,采用多种统计诊断方法分析了冬季降雪的时空特征以及与环流因子的关系。结果表明：初冬降雪高值中心位于内蒙古东北部。在冬春之交时,降雪高值区移至华北南部。1960s和1970s为不同等级降雪的偏多时段,降雪的高值中心由内蒙西部（1960s）东移至河北、山西大部（1970s）。2000s以来大雪在山西、河北的北部地区最为显著,其次是呼伦贝尔地区。降雪频次的变化上可以发现,各区的大雪频次均呈减少趋势,其中Ⅵ区减少的趋势最为显著。在降雪偏少的时段（1980s、1990s）水汽输送较弱,呈西北—东南向;而在其他年代水汽输送较强,近10年水汽输送呈东南—西北向。在年代际上降雪总量与气温、AO指数呈反相关,而中等以上降雪量与气温和AO指数在内蒙古东北部大兴安岭、太行山脉等高海拔地区呈显著正相关。