德令哈大气水汽中δ~(18)O的时间变化特征——以2005年7月～2006年2月为例

大气水汽中氧稳定同位素是研究气候现代过程的重要手段.根据测得的青藏高原东北部德令哈2005年7月~2006年2月大气水汽中δ18O以及观测的气象要素,分析了德令哈大气水汽中δ18O的变化特征以及与温度、比湿的关系.研究结果表明,德令哈大气水汽中δ18O季节变化显著,夏季值高于冬季值;在取样期间存在较大的波动,波动幅度超过37‰;受温度季节变化影响,德令哈大气水汽中δ18O的日变化与日平均温度之间存在着明显的正相关关系;德令哈大气水汽中δ18O与大气中水汽含量的关系较复杂,研究发现在季节尺度上,冬季大气水汽中δ18O与空气比湿成正相关关系,但在夏季,大气水汽中δ18O显著受到降水的影响而与空气比湿显现相反的关系;德令哈大气水汽中δ18O值低于当地降水中δ18O值,它们之间平均差值?δ18O为10.7‰;德令哈大气水汽中δ18O值受到降水事件的影响,在7,8月间相对偏低,模拟结果显示,降水事件使德令哈大气水汽中δ18O值在7,8月间平均偏低7‰.     

晴天及阴天条件下WRF模式中几种边界层参数化方案的对比分析研究

利用WRF模式中5种常用边界层参数化方案(ACM2、YSU、BouLac、MYJ和MYNN2.5)及美国能源部大气辐射观测试验(ARM)寿县综合观测数据(2008年8—12月),对比分析了晴天及阴天条件下,不同参数化方案对典型农田下垫面气象要素及边界层结构的模拟效果,结果表明:(1)模式对于云层状况的模拟,非局地方案ACM2和YSU方案优于局地方案.(2)对于近地层气象要素,晴天和阴天条件下均是ACM2方案对于2 m温度和比湿的模拟效果最好,MYJ方案对于风向风速的模拟效果最好.(3)对于位温及比湿垂直廓线的模拟,晴天和阴天条件下均是非局地方案(ACM2和YSU)对白天的模拟效果优于局地方案;ACM2方案对夜间弱稳定层结和逆湿结构的模拟最优;(4)对于风速垂直廓线的模拟,白天不稳定条件下,晴天条件MYJ方案最优,阴天MYNN2.5方案的模拟效果最好;夜间弱稳定条件下,晴天条件ACM2方案与观测值之间的偏差最小,阴天YSU方案模拟效果最好;(5)总体而言,在对典型农田下垫面进行模拟时,晴天和阴天条件下均是ACM2方案更具优势.     

德令哈大气水汽中δ^18 O的时间变化特征——以2005年7月-2006年2月为例

大气水汽中氧稳定同位素是研究气候现代过程的重要手段．根据测得的青藏高原东北部德令哈2005年7月-2006年2月大气水汽中δ^18 O以及观测的气象要素,分析了德令哈大气水汽中δ^18 O的变化特征以及与温度、比湿的关系．研究结果表明,德令哈大气水汽中δ^18 O季节变化显著,夏季值高于冬季值;在取样期间存在较大的波动,波动幅度超过37‰;受温度季节变化影响,德令哈大气水汽中δ^18 O的日变化与日平均温度之间存在着明显的正相关关系;德令哈大气水汽中δ^18 O与大气中水汽含量的关系较复杂,研究发现在季节尺度上,冬季大气水汽中δ^18 O与空气比湿成正相关关系,但在夏季,大气水汽中δ^18 O显著受到降水的影响而与空气比湿显现相反的关系;德令哈大气水汽中δ^18 O值低于当地降水中δ^18 O值,它们之间平均差值△δ^18 O为10．7‰;德令哈大气水汽中δ^18 O值受到降水事件的影响,在7,8月间相对偏低,模拟结果显示,降水事件使德令哈大气水汽中δ^18 O值在7,8月间平均偏低7‰．     

鄱阳湖水体夏季气温效应

本文讨论了定量计算湖泊纯水体气温效应的方法,在计算鄱阳湖水体夏季纯水体气温效应值的基础上,重点分析鄱阳湖水体夏季气温效应的特征、强度和分布,其结果是鄱阳湖水体夏季对湖区气温影响呈热源效应。表现在提高了湖区夏季平均气温,湖中心棠荫站比湖外高O.1—1.0℃,纯水体气温效应为0.4℃。随着距水体距离的增大,气温效应也逐渐减弱,水体影响气温的范围约为10—40km。由于湖区夏季受到副热带高压控制,陆风比湖风旺盛,气温效应夜间比白天强,加上地形的作用,影响范围南部比北部大。1980—1987年间的7、8月考察资料也和上述结果相吻合。     

北京城市化对夏季大气边界层结构及 降水的月平均影响

为克服针对一次或几次天气过程研究城市化对边界层结构及降水影响的局限性,尝试研究北京城市化对夏季大气边界层结构及降水的月平均影响,本文首先总结了2006年8月份的主要天气过程,分析了气象站观测的10 m高度风速、2 m高度气温、2 m高度比湿和24 h降水的月平均分布特征,然后利用WRF/Noah/UCM模拟系统,进行了该月30个个例的高分辨率数值模拟及检验分析,并通过多组不同城市化情景的敏感性试验对比分析了城市化对夏季大气边界层结构及降水的月平均影响.研究表明:本文所用对高分辨率数值模拟结果进行月平均的方法可以较合理地模拟出城市化对大气边界层结构及降水的影响,并再现观测到的各站风频差异.8月份,北京城市化对气温的影响高度白天约为800 m,近地面气温升高1℃以上;夜间约为200 m,对近地面气温的影响达到最大(1.4℃以上).白天,城市化使城市及下风向的一些区域风速略有减小;夜间,城市及周边区域200 m以下风速明显减小,且在100 m左右高度处风速减小最明显,减小达0.8 m/s以上.城市化白天使700 m以下比湿减小,近地面处减小达1.2g/kg以上,夜间使近地面空气比湿略有减小.城市化对城市区域平均降水量的影响随城市发展的不同阶段而不同.初步模拟分析表明, 北京城市化已使上风向区域以及城区三环以内降水量减少,海淀和昌平降水明显增加.     

东太湖水温变化与水-沉积物界面热通量初探

水温对沉水植被的生长和分布具有重要作用,水-沉积物界面热通量对浅水湖泊水温变化的影响值得关注.东太湖是我国东部典型的草型浅水湖区,采用自2013年11月至2015年10月对东太湖湖心进行的不同深度水体及沉积物温度高频观测数据,结合东太湖表层沉积物的热力学性质计算了水-沉积物界面热通量,分析了东太湖水温和水-沉积物界面热通量的变化特征并探讨了其影响因素.结果表明：东太湖各深度水体日升温过程随水深增加后延,升温过程夏季延长,冬季缩短;表层水温日变幅最大,底层水温日变幅次之,沉积物温度日变幅最小,各深度温度日变幅夏季最小、冬季最大;春季和夏季升温过程中各深度日均温变化沿水深存在约1天的延迟,秋季和冬季无此现象;2015年与2014年东太湖温度变化趋势相同,同比月均温差与气温差呈线性相关.沉积物8：00-19：00向水体放热增加或从水体吸热减少,19：00至次日8：00放热减少或吸热增加;3-9月从水体吸热,为热汇,10月至次年2月向水体放热,为热源,沉积物全年为湖泊热源;逐日水-沉积物界面热通量每月6至15日存在相对年变幅较小幅度的正弦式波动.水温和水-沉积物界面热通量的变化主要受太阳辐射和气温的影响,二者对气象参数的响应具有迟滞现象;水-沉积物界面热通量与水温呈负相关,其变化相对水温迟滞,水-沉积物界面热交换的主要作用为缓冲湖泊水体的热量变化;夏季,沉水植物能降低湖泊各层水温和垂向水温差.     

中国廊坊(39.4°N,116.7°E)中间层和低热层潮汐的季节变化

本文利用中国廊坊站(39.4°N,116.7°E)流星雷达在2012年4月1日至2013年3月31日期间的水平风场观测数据,分析了廊坊上空中间层和低热层(MLT,80~100 km)大气纬向风、经向风潮汐的季节变化特征.研究表明:廊坊MLT区域周日潮汐和半日潮汐波动比较显著,有明显的季节变化特征.周日潮汐振幅在88 km以下为半年变化,极大值位于2-3月和10月,极小值位于冬、夏季;在88 km以上为周年变化,振幅冬末春初最强,夏季最弱.周日潮汐相位在秋、冬季比春、夏季提前.半日潮汐主要呈现半年变化,在5月和9月最强,冬、夏季最弱.半日潮汐相位在春、夏季比秋、冬季提前.此外,廊坊风场潮汐的观测结果与WACCM4模式模拟结果进行比较,结果表明两者的主要特征相似,在细节上有显著区别.与40°N附近其他站点风场潮汐观测结果的比较结果表明中纬度MLT风场潮汐有显著的随经度变化特性.     

黄壁庄水库降水效应的分析

根据黄壁庄水库地区建库前后多年的降水量资料,采用回归分析和综合系数法。分析了大型水厍水体对其周围地区降水量的影响。结果表明,建库使得该地区降水量的时空分布发生了变化。全年和6—9月、10—2月三个时段的降水量比建库前有所减少,而春季(3—5月)降水量比建库前略有增加。在离库边一定的距离范围内(约5—10km),为水库对降水量的主要影响范围。     

COSMIC大气掩星与SABER/TIMED探测温度数据比较

本文利用2009年1月-2011年12月共3年的COSMIC大气掩星观测数据与SABER/TIMED探测数据开展15~60 km大气温度数据的比较分析研究,计算COSMIC与SABER/TIMED探测温度的绝对偏差(T_SABER-T_COSMIC),并统计其平均温度偏差和标准偏差,分析温度偏差随高度、纬度和季节的分布特征,为COSMIC大气掩星与SABER/TIMED探测数据的应用提供更多的参考依据.结果表明:COSMIC与SABER/TIMED数据所反映的温度随高度的变化特征是一致的,数据的大体趋势吻合较好.全球范围的平均温度偏差在38 km左右接近于0 K,在38 km以上,平均温度偏差表现为负的系统性偏差,且随着高度逐渐增大,在38 km以下,平均温度偏差表现为正的系统性偏差,在23 km左右存在极大值,约为2.7 K.COSMIC与SABER/TIMED温度偏差的分布存在着随纬度和季节的变化特征,35 km以下,平均温度偏差在高纬地区和冬季较小,低纬地区和夏季较大,35 km以上,平均温度偏差在高纬地区和冬季较大,低纬地区和夏季较小.温度偏差的标准偏差在低纬地区和夏季较小,高纬地区和冬季较大.纬圈平均的温度偏差在南北半球的分布基本呈对称结构.     

基于卫星资料的北京陆表水体的热环境效应分析

应用不同分辨率的卫星资料对北京水体类别、密云水库及城区典型水体的热环境特性及城区水体对其周围热环境影响进行研究分析.利用2006年的MODIS卫星地表温度产品对北京不同类型的地表温度研究显示:就北京四季平均状态来说,水体类别在白天具有降温作用,在秋季和冬季夜晚具有保温作用,在春季和夏季夜晚具有降温作用.利用NOAA/AVHRR卫星资料对密云水库的研究分析显示:密云水库在夏季白天具有"冷湖效应",夜晚具有"暖湖效应";密云水库在冬季未结冰时白天和夜间具有"暖湖效应",在结冰时白天具有"冷湖效应"而晚上无冷暖效应.利用FY-3A/MERSI、NOAA/AVHRR和Landsat-TM卫星资料对北京城区典型水体监测结果显示:城区水体不会有热岛现象出现,大面积的水体易出现"冷岛效应".利用2008年夏季Landsat-TM卫星资料对城区典型水体和天坛公园绿地500 m范围内的建筑地温研究分析显示:城区水体温度明显低于天坛公园绿地.城区各水体周边100 m范围内建筑区地温平均下降1.2℃;100～200 m内下降0.6℃;200～300 m内下降0.4℃,300 m范围外无明显变化.天坛公园绿地周边仅100 m内的建筑区地温下降,下降值为0.4℃.这些研究结果表明:卫星资料能有效监测水体的热环境效应,大面积的水体是降低城市地表热岛效应的重要来源,北京城区水体对周边最大300 m范围内的建筑区地表温度具有降温效应.     

Analytical Solution for Well Design with Respect to Discharge Ratio

For a well in the vicinity of a surface water body, a formula is developed that relates the share of bank filtrate on total pumpage, that is, the discharge ratio, on one side, to basic well and aquifer characteristics on the other. The application of the formula is demonstrated for solving the inverse problem: for an aimed discharge ratio, well characteristics (pumping rate, distance to shore) can be determined. Other useful applications of the formula are outlined.     

Are peatlands cool humid islands in a landscape?

This study proposed that due to their high standing water tables that peatlands would be cold humid islands within their landscape, and especially so relative to farmland on mineral soils. To test this hypothesis, we measured air temperature and humidity at 17 locations along a 7.8 km transect across the UK's largest lowland raised bog from February 2018 to January 2019. Air temperature and humidity were measured hourly for 1 year and supported with spot albedo measurements. The study represented a factorial experiment with respect to sites of measurement, the type of land use (peat vs. arable land) and time of sampling over both the seasonal and diurnal cycles. We show that: (a) That although mean annual temperature was not significantly different between arable and peatlands, the arable land showed a decreased amplitude to its seasonal cycle – this is the reverse of the expected pattern. (b) The albedo of the peatland was significantly lower than that of arable land showing that vegetated peatland still absorbed more solar radiation. (c) The specific humidity was lower on the peatland than on the surrounding arable land. The study showed that while shrubby vegetation exists over a peatland then energy budgets are more likely to be dominated by the lower aerodynamic resistance and lower albedo of the vegetated peatland relative to arable land. Thus, shrub-dominated peatlands will not be a cold humid island in their landscape.     

白洋淀水陆下垫面上行星边界层空间变动研究

利用三维非静力中尺度模式ARPS,对白洋淀地区水陆非均匀下垫面上大气边界层结构及其变动进行了模拟研究.结果表明,晴天弱背景下,白洋淀地区陆地大气比湿高于水域的情况发生在白天大部分时间内,是普遍存在的一种现象,该现象首先出现在近地层,然后不断向高空延伸,与水陆两种不同的下垫面特征密切相关.由于水陆下垫面的差异,导致水域感热和潜热通量全天较小,变化平稳,而陆地日间感热和潜热通量较大,且潜热高于感热.水陆两地近地层湍流运动状态存在较大差异,湍流输送在水陆比湿空间变动过程中起决定性作用.形成的局地环流同样影响着水陆比湿的空间变动,主要表现在环流上下支对近地层湍流发展以及水汽的垂直输送的影响.陆地上空水汽主要来源于土壤植被的蒸发蒸腾,而来自水域的仅占很少一部分.     

Hydrogeomorphic types of glacially created kettle holes in North-East Germany

Kettle holes are glacially created, small, shallow, depressional wetlands collecting their water from internal or closed catchments in young moraine landscapes. Their water body is defined by having a maximum of 1 ha in extent. Mostly they undergo a wet-dry circle. In North-East Germany, kettle holes are widely spread, mostly on arable land. They are characterised by large differences in hydroperiod (HP), size, shape and edge steepness. They also have a high potential for both, geomorphic structural diversity and biological species diversity. However, kettle holes are subject to pollution, drainage and structural reduction that result from intensive land use practices.Although kettle holes in Germany are protected by law, protection strategies are not specific enough with respect to the variability of kettle holes, especially of HP. Therefore, the study objective was to characterise hydrogeomorphic (HGM) kettle hole types to create a basis for a decision support system with regard to the selection of the type dependent conservation and management measures.In three agricultural landscapes in North-East Germany, geomorphological and hydrological variables of 268 kettle holes (HP, shore overflow tendency, depth, area, form, shore width and slope) as well as those of their catchments (area, wetland to catchment area ratio, relief) were investigated from 1993 to 2003. By statistical analysis of datasets of 144 kettle holes, 10 HGM kettle hole types were defined. The basic types are “silted fen type” and “open-water type”. Basic subtypes of the latter type are “storage type”, “shore overflow type” and “puddle type”. Differences in spreading of kettle hole types in dependency on landscape relief were found.     

Paleomagnetic study of the Tunguska catastrophe epicenter

The Tunguska catastrophe occurred in the area of the East Siberian magnetic anomaly on June 30, 1908. The epicenter of the explosive destruction of the Tunguska cosmic body (TCB) was above the central neck of a paleovolcano (Mt. Stoikovich). According to the paleomagnetic data available, the bedrocks on the top of Mt. Stoikovich carry remanent magnetization, which is substantially higher than that in rocks from neighboring mountains. Analysis of the results of paleomagnetic measurements of rock samples collected in the vicinity of the Tunguska catastrophe epicenter showed that the destruction of the cosmic body was accompanied by the formation of multidirectional magnetic fields, which provide disturbances spreading over a distance of 25 km from the epicenter. The chaotic distribution pattern of magnetization vectors measured in the soil in the vicinity of the Tunguska catastrophe epicenter confirms the previously expressed assumption that destruction of the TCB was accompanied with multiple discharges. According to this, we can conclude that the matter of the Tunguska cosmic body was dispersed around the epicenter in a zone approximately 25 km in diameter.     

Neotectonic faulting and the Late Weichselian shoreline gradients in SW Norway

The Younger Dryas (YD) maximum highstand shoreline in SW Norway has traditionally been considered as being slightly concave, gradually steepening in the direction of uplift. This phenomenon is attributed to geoidal and isostatic effects near the former ice-sheet margin. On the basis of isolation basin data from the region, we have reconstructed this shoreline, and a Bølling-Allerød (B-A) lowstand shoreline, along three profiles in SW Norway. Along all profiles there are shore levels which, within the error limits estimated, cannot be captured by a single straight (or curved) shoreline. The anomalous shore levels occur near major fault zones and are interpreted to reflect differential uplift rates on opposite sides of faults, superimposed on the general glacio-isostatic tilting of the region. The inferred faulting is consistent with observations previously reported as neotectonic ‘claims’ in the region and shed new light on the deformational structures observed in seismic profiles of the fjord sediments. Excluding the anomalous shore levels, a straight shoreline with gradient ca. 1.1 m/km provides the best and most consistent representation of the YD shore levels along the three profiles. The B-A lowstand shoreline is constrained by fewer data points, but is approximately parallel-dipping the highstand shoreline. Our reconstructions imply a less steep YD maximum highstand shoreline compared to previous reconstructions, where gradients up to 1.4 m/km have been inferred. This may imply that the ice load effect on the lithosphere in SW Norway during the YD is less than previously assumed.     

龙滩库区库水加卸载过程深部电阻率变化与水库地震

广西龙滩库区于2009年度至2010年2个年度库水加卸载及渗透过程中,在交比屯、坪上、中良坪和向阳4个地点进行了5期次大地电磁定点测量,观测频段为320 Hz~1000 s.结合区域深部电性结构探测研究成果分析.结果显示,4个测点位于不同的岩性和深部电性结构区域,4个测点上观测的5期次视电阻率值发生变化的频段不同,位于库区中游的坪上、中良坪和向阳3个测点上5期次测量的视电阻率数值在频率1 Hz以下频段在高水位时段测量值小、在低水位时段测量值大,位于库首区域的交比屯测点在最高水位时段视电阻率数值最小,说明库水在加卸载及渗透过程中对地下介质有明显影响,库区上游库水渗透影响深度可达7 km左右,在坝首区域可达10 km.龙滩水库区4个地震丛集区中的3个地震丛集区的震源区位于具有低阻特性的二迭系下统和石炭系地层的下部,以岩溶水体诱发地震为主;位于坝首地震丛集区的震源区位于上宽下窄似"铆钉状"的高阻体下部,推测是因水库蓄水后水体压力增大和库水渗透作用下,在聚集高变形能的脆性高电阻体内部发生的地震.电磁探测结果说明库水渗透对龙滩水库区地震孕育和发生起着重要、直接的作用.     

A numerical model of spring thermal bar development and energy exchange between a water body and the atmosphere at night

A mathematical model is used to assess the effect of temperature and relative air humidity on variations of long-wave radiation flux and the fluxes of sensible and latent heat at the water body-atmosphere interface at night in the period of spring thermal bar development. The effect of those fluxes on variations of the heat storage of the water body, the position of the thermal bar, and the velocity of its motion at night is evaluated.     

Airborne Lidar Observations of Water Vapor Variability in Tropical Shallow Convective Environment

An airborne downward-pointing water vapor lidar provides two-dimensional, simultaneous curtains of atmospheric backscatter and humidity along the flight track with high accuracy and spatial resolution. In order to improve the knowledge on the coupling between clouds, circulation and climate in the trade wind region, the DLR (Deutsches Zentrum für Luft- und Raumfahrt) water vapor lidar was operated on board the German research aircraft HALO during the NARVAL (Next Generation Aircraft Remote Sensing for Validation Studies) field experiment in December 2013. Out of the wealth of about 30 flight hours or 25,000 km of data over the Tropical Atlantic Ocean east of Barbados, three ~ 2-h-long, representative segments from different flights were selected. Analyses of Meteosat Second Generation images and dropsondes complement this case study. All observations indicate a high heterogeneity of the humidity in the lowest 4 km of the tropical troposphere, as well as of the depth of the cloud (1–2 km thick) and sub-cloud layer (~ 1 km thick). At the winter trade inversion with its strong humidity jump of up to 9 g/kg in water vapor mixing ratio, the mixing ratio variance can attain 9 (g/kg)², while below it typically ranges between 1 and 3 (g/kg)². Layer depths and partial water vapor columns within the layers vary by up to a factor of 2. This affects the total tropospheric water vapor column, amounting on average to 28 kg/m², by up to 10 kg/m² or 36%. The dominant scale of the variability is given by the extent of regions with higher-than-average humidity and lies between 300 and 600 km. The variability mainly stems from the alternation between dry regions and moisture lifted by convection. Occasionally, up to 100-km large dry regions are observed. In between, convection pushes the trade inversion upward, sharpening the vertical moisture gradient that is colocated with the trade inversion. In most of the water vapor profiles, this gradient is stronger than the one located at the top of the sub-cloud layer. Lidar observations in concert with models accurately reproducing the observed variability are expected to help evaluate the role these findings play for climate.     

Discharge of pyroclastic flows into the sea during the 1996–1998 eruptions of the Soufrière Hills volcano, Montserrat

Explosive eruptions of the Soufrière Hills volcano on the island of Montserrat in the West Indies generated pyroclastic flows that reached the sea on the east and southwest coasts between November 1995 and July 1998. Discharge of the flows produced two pyroclastic deltas off of the Tar and White River valleys. A marine geological survey was conducted in July 1998 to study the submarine extensions of both deltas. Detailed profiles of depth and sub-bottom structure were obtained using a CHIRP II/bubble pulser system. These profiles were compared with pre-eruption bathymetric data in order to identify areas of recent deposition and erosion. Deposition off the Tar and White River valleys was thickest nearest the coastline and deltas, and extended into deeper water up to 5 km from shore. The total volume of submarine pyroclastic deposits as of July 1998 was 73×10⁶ m³ DRE. Submarine pyroclastic deposits off the Tar River valley made up more than two-thirds of the total volume (55×10⁶ m³ DRE) and covered an area of approximately 5.0 km², which included the delta. The volume of submarine pyroclastic deposits in the White River area (18×10⁶ m³ DRE) is probably underestimated due to the lack of precise pre-eruption bathymetric data in areas greater than 2 km from shore. Growth of pyroclastic deltas at the mouths of the Tar and White River valleys continued to the edge of the submarine shelf where there was a steep break in slope. In the Tar River area pyroclastic material was distributed down the steep shelf break and into deeper water at least a few kilometers from shore. The material spread out radially, forming a submarine fan, where distribution was primarily controlled by bathymetry and slope.Editorial responsibility; J. Stix