塔克拉玛干沙漠腹地冬季大气边界层O3廓线分析

为了揭示塔克拉玛干沙漠腹地冬季大气边界层O3的浓度变化特征,利用系留气艇于2008年1月18—25日在塔中地区进行了大气边界层O3观测试验,结合相关资料,初步分析了塔中地区冬季边界层O3浓度垂直分布特征及其与温度、湿度的关系。其结果是:①塔中地区臭氧浓度集中分布在10~50 ppb之间,其中试验期间观测到O3最大浓度值56.1 ppb,最小浓度为2.6 ppb,臭氧的最大浓度基本都在40 ppb左右,日平均浓度为34.4 ppb。②大气边界层O3的浓度廓线可分为峰值型、均匀型、增长型3种,其中均匀型所占比重最大。③大气边界层O3浓度与温度、湿度密切相关,逆温及空气中水汽的增加会导致臭氧浓度降低。④大气边界层O3有明显的日变化,越贴近地面日变化越明显,其变化特征与太阳辐射有着密切关系。臭氧浓度夜晚较低,日出后开始增加,午后达到一天中的最大值;随着日落,臭氧浓度开始减小,在清晨达到最小值;臭氧浓度日最大值出现在17:00,最小值出现在08:00。     

塔中春季晴天近地层温度、湿度和风速廓线特征

利用最新安装的塔中"80 m观测塔梯度探测系统"资料,详细分析了塔中春季晴天近地层80 m高度内平均温度、湿度和风速廓线日变化分布特征,得出以下一些结果:(1)温度廓线有夜间辐射型、早上过渡型、白天日射型和傍晚过渡型四种.夜间近地层大气层结稳定,呈逆温特征;最强逆温出现在凌晨06时,此时,80 m高度温差为11.1 ℃.白天,近地层80 m内温度递减率在2.7～5.2 ℃/100 m之间,大气一直处于超绝热不稳定状态.(2)湿度廓线有日夜之分.夜间,30 m以下比湿随高度增高急剧变小,30 m以上比湿随高度增加而增大,大气呈逆湿特征.白天,比湿随时间一直逐渐变小.在近地层30～50 m之间有一个厚度约20 m的逆湿层,全天都存在.(3)风速廓线也有日夜之分.夜间稳定层结,廓线风速值以比对数关系更快的速度向上递增,曲线弯向风速轴.白天不稳定层结,廓线风速值以比对数关系较慢的速度向上递增,曲线弯向高度轴.只有在10 m以下高度,日夜间的风廓线近似遵循对数律关系.     

The variation characteristics and effect factors of surface ozone concentration in the Taklimakan Desert hinterland

Based on automatic continuous surface ozone concentration observation data from June 10, 2010 to March 20, 2012 in the Taklimakan Desert hinterland, combined with corresponding meteorological data, the temporal, seasonal and daily variation characteristics of surface ozone concentrations under different weather conditions were analyzed. At the same time, the main fac- tors affecting ozone variation are discussed. Results show that： （1） Daily variation of ozone concentration was characterized by one obvious peak, with gentle changes during the night and dramatic changes during the day. The lowest concentration was at 09：00 and the highest was at 18：00. Compared to urban areas, there was a slight time delay. （2） Ozone concentration variation had a weekend effect phenomenon. Weekly variation of ozone concentration decreased from Monday to Wednesday with the lowest in Wednesday, and increased after Thursday with the highest in Sunday. （3） The highest monthly average concentration was 89.6 I.tg/m3 in June 2010, and the lowest was 32.0 ~g/m3 in January 2012. Ozone concentration reduced month by month from June to December in 2010. （4） Ozone concentration in spring and summer was higher than in autumn and winter. The variation trend agreed with those in other large and medium-sized cities. （5） Under four different types of weather, daily ozone concentration var- ied most dramatically in sunny days, followed by slight variation in rain days, and varied gently in cloudy days. Ozone concentra- tion varied inconspicuously before a sandstorm appearance, and dropped rapidly at the onset of a sandstorm. （6） Daily variation of radiation was also characterized by a single peak, and the variation was significantly earlier than ozone concentration variation. Sun radiation intensity had a direct influence on the photochemical reaction speed, leading to variation of ozone concentration. （7） Daily average ozone concentration in dust weather was higher than in slight rain and clear days. The variation of near surface ozone concentration could also be affected by meteorological factors such as relative humidity, wind speed, wind direction and sunshine hours. Thus, numerous factors working together led to ozone pollution.     

塔克拉玛干沙漠腹地几种植物根系分形特征

在塔克拉玛干沙漠腹地采用全根挖掘法挖掘河西菊(Hexinia polydichowma(Ostenf.)H.L.Yang)、沙拐枣(Calligonuin roborovskii A.Los.)、罗布麻(Apocynum venetum L.)、阿克苏牛皮消(Cynanchum amplexicaule Hemsl)根系.运用分形理论对其分形特征进行研究,分析根系分支状况以及根系分形特征与拓扑特征之间的关系.研究发现:(1)在塔克拉玛干沙漠腹地,四种植物根系具有很好的分形特征,分形维数大小与拓扑参数连接总数、外部连接数之间具有较好的相关关系.(2)根丰度是描述根系在土层中扩展能力的有效指标,与根系长度、平均连接长度之间具有很好的指数关系分别可以用以下方程表示:y1=2.7 694e1.5496x,y2=0.0369e2.0 267x(其中y1、y2分别为总根长、平均连接长度,R2分别为:0.9 353、0.9 832),根丰度直接反映了根系空间占有能力与营养物质的吸收效率.通过对塔克拉玛干沙漠腹地四种植物根系分支状况与分形特征的研究表明.分形理论可以很好的反映根系空间占有能力与资源吸收效率,所以说分形理论是对根系几何、功能特征进行定量化研究的有效方法.     

塔克拉玛干沙漠腹地两种灌木有效根系密度分布规律的研究

在塔克拉玛干沙漠腹地通过分层分段挖掘法对滴灌条件下多枝柽柳(Tamarix ramosis-sima)和梭梭(Haloxylon ammodendron)幼苗根区有效根长密度和有效根重密度空间分布进行了研究。结果表明:梭梭幼苗平均有效根系密度为多枝柽柳幼苗的3倍左右。在垂直方向上,两种灌木的有效根系密度的变化因树种而异,多枝柽柳幼苗随土层深度的增加呈指数递减,而梭梭幼苗随土层深度的增加呈单峰型曲线。在水平方向上,两种灌木幼苗有效根系密度均随距离植株基径距离的增加呈指数递减。非线性参数拟合分析表明:采用RD=eA BX CZ函数模型能较好地反映滴灌条件下多枝柽柳幼苗的有效根系密度的空间分布。     

Validation of AIRS-Retrieved atmospheric temperature data over the Taklimakan Desert

The Taklimakan Desert, the world's second largest desert, plays an important role in regional climate change. Previous studies on its spatial temperature features suffered from sparse conventional detection data, but the Atmospheric Infrared Sounder(AIRS) provides excellent temperature retrievals with high spatiotemporal resolution. Validation of AIRS temperature retrievals over desert regions with high land-surface emissivity, the key contributor to inversion error, is essential before using these data in regional weather/climate modeling. This paper examines the correlation coefficients, root mean square error(RMSE) and mean BIAS between AIRS-retrieved atmospheric temperature data and radiosonde observations(RAOBs) in the Taklimakan Desert hinterland and oases in the morning and at dusk. Firstly, the AIRS retrievals are consistent with RAOBs and are more consistent in the morning than at dusk. The consistency is better over a small-scale desert oasis than over a large-scale oasis in the morning and exhibits the opposite trend at dusk. The correlation coefficient over the hinterland is high in the morning but negative at dusk due to high desert-surface emissivity. Second, the RMSEs, which are all smaller than 3 K, are generally higher over desert sites than over oasis sites and slightly lower over a small-scale oasis than over a large-scale oasis in the morning. At dusk, the RMSEs are higher over desert sites than over oases and slightly higher over a small-scale oasis than over a large-scale oasis. Furthermore, the RMSEs are generally higher in the morning than at dusk over a large-scale oasis and lower in the morning than at dusk over a small-scale oasis. Third, the absolute mean BIAS values are mostly lower than 1 K. In the morning, relative to RAOB temperatures, the retrieval temperatures are higher over desert sites but lower over oasis sites. At dusk, the retrieval temperatures are lower than RAOB temperatures over both desert and oasis sites. The retrieval temperatures are higher than RAOB temperatures over desert sites in the morning but slightly lower at dusk. Most absolute mean BIAS values are higher in the morning than at dusk over both oasis and desert sites. Finally, the consistency between the AIRS and RAOB temperature data is high from 700 hPa to 100 hPa in the morning and from 700 hPa to 300 hPa at dusk. The difference between the AIRS and RAOB temperature data is generally higher in the morning than that at dusk. The RMSE differences between the AIRS and RAOB data are slightly lower in the morning than at dusk and are lower in the middle layers between 700 hPa and 150 hPa than in the layers above 150 hPa during both the morning and night. The BIAS is lower in the morning than at dusk below 300 hPa but higher in the upper layers. Moreover, the BIAS value is positive in the middle layers between 500 hPa and 150 hPa and negative at other levels at both times. Generally, the AIRS retrieval temperatures are reliable and can be used in further studies in the Taklimakan Desert.     

塔克拉玛干沙漠腹地潜水水位对单井抽水的响应

塔里木沙漠公路防护林生态工程以地下水为灌溉水源,全线采用节水滴灌方式灌溉。全线共有108口水源井,水源井间距约4 km。以第69号水源井(38°41′12″N、83°22′16″E)为例,在距水源井120 m范围内设置了7个地下水监测井,利用潜水水位的动态观测数据,分析了抽水过程中水位的时空变化规律。研究结果表明:持续抽水过程中潜水水位变化可分为快下降和慢速下降两个阶段;潜水水位恢复过程可分为快速上升和慢速上升两个阶段。水位下降和上升的速度变化形成水位的空间差异,即降落漏斗的形成和消失。利用稳定流抽水试验计算得出含水层渗透系数为12.85 m/d。     

塔克拉玛干沙漠腹地起伏地形近地层微气象特征

利用2018年10月8日至2019年1月31日塔克拉玛干沙漠腹地起伏地形上高大沙垄高点和低点的温度、相对湿度、风速和大气压同步观测资料,对比分析沙漠起伏地形上秋冬季的微气象特征。结果表明:塔克拉玛干沙漠腹地高大沙垄造成的地形起伏,使得沙垄高点和沙垄低点气温、比湿和风速日变化差异明显。沙垄高点和沙垄低点气温差异主要体现在夜间,与沙漠腹地夜间存在逆温现象有关,表现出沙垄高点气温明显高于沙垄低点,观测期气温差异平均值为6.6 ℃。沙垄低点气温日较差高于沙垄高点。2018年10、11、12月,气温随高度变化出现逆温现象与沙垄高点气温高于沙垄低点气温在时间上相互对应。两个站点比湿较小,平均比湿分别为0.68 g·kg^-1和0.99 g·kg^-1。比湿日变化趋势随季节发生显著变化,主要与大气稳定度增加、冬季水汽增多及夜间逆湿现象逐渐显著相关。地形位置较高的沙垄高点风速比沙垄低点大,风速差异主要体现在夜间。2018年11月2、14、15、20日和2019年1月30日,沙垄高点风速维持在1.9~4.6 m·s^-1,平均3.2 m·s^-1,沙垄低点风速维持在0.8~4\^5 m·s^-1,平均2.5 m·s^-1。     

Analysis of mass concentration of atmospheric particulate matter in a sandstorm course and its affecting factors in the Taklimakan Desert

During the course of a major sandstorm from April 17 to April 23, 2008 in the Taklimakan Desert, data pertaining to the mass concentrations of different-sized atmospheric particulate matter were observed continuously with Grimm 1.108, Thermo RP 1400a, TSP, and CAWS-600 instruments. The results showed that: (1) during the entire sandstorm process there were some differences between the daily mean particle concentration peaks and the hourly mean particle concentration peaks because the actual sandstorm lasted for only about 4 hr, whereas more particles were accumulated in the floating dust days before and after the actual sandstorm; (2) the intensity of the sandstorm was enhanced with the increase of wind speed, and this was related to the peak mass concentrations of atmospheric particulate matter; the wind speed directly affected the concentration of atmospheric particulate matter: the higher the wind speed, the higher the mass concentration (>0.23 μm was 39,496.5 μg/m³, and >20.0 μm was 5,390.7 μg/m³); (3) the concentration changes of PM₁₀ and TSP were also related to the course and intensity of the sandstorm; and (4) the mass concentration of atmospheric particulate matter had the following sequence during the dust weather: clear day < floating dust < floating and blowing dust < sandstorm. Temperature, relative humidity, and barometric pressure are important factors affecting the strength of storms, which could also indirectly affect the concentration change of atmospheric particulate matter.     

Vertical distribution characteristics of dust aerosol mass concentration in the Taklimakan Desert hinterland

The different height mass concentrations of dust aerosol data from the atmosphere environment observation station （Ta- zhong Station） was continuously observed by instruments of Grimm 1.108, Thermo RP 1400a and TSP from January of 2009 to February of 2010 in the Taklimakan Desert hinterland. Results show that： （1） The mass concentration value of 80 m PMl0 was higher, but PM2.5 and PM1.0 concentrations at 80 m was obviously lower than 4 m PMl0, and the value of 80 m PM1.0 mass concentration was the lowest. （2） The PM mass concentrations gradually decreased from night to sunrise, with the lowest concentration at 08：00, with the mass concentration gradually increased, up to the highest concentration around 18：00, and then decreased again. It was exactly the same with the changes of wind speed. （3） The high monthly average mass concentration of TSP mainly appeared from March to September, and the highest concentration was in April and May, subsequently gradually decreased. Also, March-September was a period with high value area of PM monthly average mass concentration, with the highest monthly average mass concentration of 846.0 p.g/m3 for 4 m PM~0 appeared in May. The concentration of PM10 was much higher than those of PM2.5 and PM1.0 at 80 m. There is a small difference between the concentration of PM2.5 and PM~ 0. Dust weather was the main factor which influenced the concentration content of the different diameter dust aerosol, and the more dust weather days, the higher content of coarse particle, conversely, fine particle was more. （4） The mass concentration of different diameter aerosols had the following sequence during dust weather： clear day 〈 blowing dust 〈 floating and blowing dust 〈 sandstorm. In different dust weather, the value of PM~o/TSP in fine weather was higher than that in floating weather, and much higher than those in blowing dust and sandstorm weather. （5） During the dust weather process, dust aerosol concentration gradually decreased with particle size decreasing. The dust aerosol mass concentration at different heights and diameter would have a peak value area every 3-4 days according to the strengthening process of dust weather.     

塔克拉玛干沙漠腹地边界层风场特征

利用CFL-03边界层风廓线雷达在塔中开展了边界层风场探测研究,根据2010年4月1日至2010年11月30日连续的边界层风场探测资料,分析了塔克拉玛干沙漠腹地大气边界层风场时空分布特征,得到了4月至11月各月的高空风廓线。结果表明,塔中春秋季风场结构类似,中高层多为西风,风速较大,低层多为东风,风速较小,整层风速与高度成正比;夏季高层风速变小,低层风速增大,东风层增厚,夏季塔中地区上空100～200 m高度层存在明显风速切变带。     

塔克拉玛干沙漠腹地塔中地区风沙流输沙特征研究

利用多种积沙仪,通过野外实时输沙观测,对塔克拉玛干沙漠腹地塔中的地表风沙流特征进行了分析,结论如下:(1)100 cm高度范围内,总输沙量的63.1%分布在20 cm高度内,72.4%分布在30 cm高度内,随高度的增加,输沙量呈负指数函数下降;由此可见,该地区的风沙活动主要集中在近地面20～30 cm高度范围内;(2...     

塔克拉玛干沙漠腹地高大复杂纵向沙垄区沙丘分形特征

为了探讨塔克拉玛干沙漠小尺度风沙地貌形态特征,对沙漠腹地复杂纵向沙垄横断面的上覆沙丘的分形特征进行了研究。沙丘形态野外测量采用RTK(real-time kinematic)技术,并通过南方测绘软件(South Survey)量算形态特征参数。研究结果表明:(1)沙丘形态具有分形特征,饼状沙堆和沙片的分维数是1.292 2,新月形沙丘的分维数是1.286 6,简单线性沙丘的分维数是1.102 5,新月形沙丘链的分维数是1.085;(2)在不同地貌部位之间,分维数差异不大(1.0~1.3),变异系数为0.06,表明复杂纵向沙垄上覆沙丘形态有自相似性;(3)沙丘的各形态特征参数变异系数的空间变化趋势一致,且与分形维数呈显著的线性正相关(P<0.05),表明沙丘形态分形维数能客观反映沙丘形态特征。在塔克拉玛干沙漠腹地纵向沙垄区,沙丘形态分形维数可以作为反映风沙环境特征的定量指标。     

塔克拉玛干沙漠腹地近地面臭氧浓度变化特征及影响因素分析

利用塔克拉玛干沙漠腹地塔中地区2010年6月10日-2012年3月20日地表臭氧浓度连续自动观测数据,结合相应气象要素资料,对地表臭氧质量浓度的日、周、月、季节变化与不同天气条件下日变化特征进行了分析,同时探讨了影响臭氧浓度变化的主要因素。结果表明：①臭氧浓度日变化具有明显的单峰型日变化规律,夜间变化平缓,白天变化剧烈。09:00前后达到最低值,18:00前后达到最高值,出现时间稍迟于其他城市地区。②臭氧浓度变化具有“周末效应”现象。最高值出现在星期日,最低值出现在星期三;星期一至星期三浓度逐渐降低,星期四又逐渐上升。③最高月平均浓度出现在2010年6月,其浓度为89.6 μg·m-3,最低月平均浓度出现在2012年1月,其浓度为32.0 μg·m-3,2010年6-12月,浓度逐月降低。④春、夏季臭氧浓度较高,秋季和冬季明显低于春季和夏季,与大中型城市变化特征基本一致。⑤臭氧浓度日变化最剧烈的是晴天,其次为小雨天气,阴天日变化平缓。沙尘暴出现前,臭氧小时平均浓度变化较小,沙尘暴开始时浓度下降,且下降速度较快。⑥辐射变化也具有单峰型日变化规律,臭氧浓度变化明显晚于辐射变化,太阳辐射的强弱直接影响光化学反应速度,从而导致臭氧浓度的变化。⑦沙尘天气臭氧日平均浓度高于有间隙小雨天气和晴天。相对湿度、风速、风向、日照日数同时影响近地面臭氧浓度的变化,臭氧污染的发生是多种因素共同作用的结果。     

Geomorphology of sand dunes in the Northeast Taklimakan Desert

Three types of sand dunes exist in the Taklimakan Desert, namely compound/complex crescent dunes and crescent chains, compound dome dunes and compound/complex linear dunes. Besides these three compound/complex types, single simple dunes are also distributed throughout the sand sea. The compound/complex linear dunes are developed under acute bimodal wind regimes. Though the ratios of the resultant drift potential (RDP) and the drift potential (DP) are the same as that near the border and adjacent area of the sand sea, the compound/complex crescent and dome dunes are developed, respectively, because of divergence of the sand available, the stress of the sand-moving winds and the time scales of dune formation. The sand supply for the dunes is not from Lopo Nor in the east as previous studies suggested but mainly from local alluvial or lacustrine deposits. The grain size component does not correlate evidently to the morphology parameters of the sand dunes. Analyses of the DP and drift direction suggest that the northeast Taklimakan is an area of low wind energy and the resultant drift direction (RDD) coincides well with the distribution, morphology and scales of the dunes.     

塔克拉玛干沙漠湍流尺度

利用塔克拉玛干沙漠腹地塔中地区近地层32 m高度涡动相关系统2009年1、4、7、10月的湍流观测数据,对流动沙漠地区不同稳定度下的湍流特征进行了分析。结果表明:(1)流动沙漠区在不同季节、不同稳定度条件下的近地层湍流欧拉时间自相关系数R_u(t)、R_v(t)、R_w(t)衰减存在明显的时间差异。春季R_w(t)的衰减最快,夏季3个方向的欧拉时间自相关系数衰减时间相近;(2)欧拉时间自相关系数主要表现出强衰减、逐渐衰减和缓慢衰减3种类型,沙尘天气的欧拉时间自相关系数衰减总体上要强于晴天;(3)湍流的时间积分尺度L_t(z)最小,L_t(x)和L_t(y)大小相近,在沙尘暴发生时,水平风速占主导,而垂直气流很难发展;(4)湍流的空间尺度在不同季节和不同稳定度条件下明显不同:L(x)平均值6.02 m,L(y)平均值6.90 m,L(z)平均值0.73 m;湍流水平空间尺度大多数情况下呈扁平的椭球体,且水平方向呈明显的椭圆形状。     

塔克拉玛干沙漠肖塘地区空气动力学粗糙度分析

利用塔克拉玛干沙漠北部肖塘地区梯度自动站2007年1月1日至2007年5月31日的观测数据,计算出该区域中性条件下粗糙度范围是1.00×10-11~1.65×10-3 m,平均粗糙度为6.05×10-5 m,接近沙粒粒径的1/30,与平坦沙面粗糙度相似。摩擦速度的范围是0.14~2.33 m·s-1,平均值1.24 m·s-1。粗糙度随下垫面性质变化明显,与稳定度呈正相关,与风速呈负相关,摩擦速度随粗糙度增大而减小。     

塔克拉玛干沙漠地表潜热时空特征分析

利用1979年3月至2004年2月月平均的NCEP/DOE再分析地表潜热资料,在分析塔克拉玛干沙漠四季潜热基本气候特征的基础上,通过EOF方法,对沙漠地表潜热异常变化的空间结构和时间演变趋势作了诊断研究。结果表明：①沙漠地区夏季潜热最大,春季和秋季次之,冬季最小;靠近山区的沙漠西部、西北部地区四季明显大于中、东部地区。②根据四季地表潜热距平场的EOF分析,该区潜热异常主要有全区一致型、南北差异型以及西北—东南差异型三种常见的分布模态。③25 a期间,塔克拉玛干沙漠地表潜热在第一空间尺度上四季都有不同程度增强的趋势;在第二空间尺度上,春季沙漠北部、西北部有减弱的趋势,南部、东南部有增强的趋势,而冬、夏、秋季变化趋势不是很大。     

塔克拉玛干沙漠夏季晴空对流边界层大涡模拟

为了探索塔克拉玛干沙漠夏季晴空对流边界层湍流结构和热对流运动规律,利用沙漠腹地探空及地表通量观测资料,开展了晴空对流边界层的大涡模拟研究。结果表明：（1）沙漠夏季晴空条件下,对流边界层湍能主要由地表热力浮力对流产生,机械剪切对边界层湍能的贡献较小,小尺度湍涡对湍能的耗散随高度呈减弱趋势,边界层湍能变化呈现间歇性特点。（2）沙漠夏季晴空边界层中存在着有组织的热对流泡现象,热泡最大上升速度可超过4.0 m·s^-1;沙漠热对流运动一般呈羽状和网状分布特征,在上升运动区周围伴随有大片的下沉辐散区域。（3）地表感热和逆温层顶盖强度是控制和影响沙漠对流边界层发展的两个重要因素,感热增大,对流边界层变暖且高度升高;感热减小,对流边界层变冷且高度降低。在感热不变的条件下,逆温层顶盖强度越强,越不利于对流边界层发展,反之则相反。     

塔克拉玛干沙漠起沙风况

塔克拉玛干沙漠大部分地区以东北风系为主,西南边缘由西北风系控制,西北边缘多以北风为主,南部边缘均有一定数量的偏南风出现。麦盖提、金星和民丰一带为东北风系和西北风系交替控制。有５种风况类型：窄风况型、宽风况型、双风况型、三风况型和多风况型,分别对应复合型横向、斜向、纵向沙垄、星状沙丘和穹状沙丘,起沙风速基本以若羌为高值区向沙漠西部减少。