巴丹吉林沙漠典型湖泊湖气界面水一热交换特征

利用2012年8月-2013年7月在巴丹吉林沙漠腹地典型湖泊上用涡动相关系统观测的湍流资料,分析了湍流方差统计特征、微气象特征,计算了湍流热通量和湖泊蒸发量,初步结论为：①湖面上局地环流复杂,湍流三维风速的标准差与稳定度(Z/L)之间满足1/3次律。②湖面辐射分量具有明显季节变化和日变化特征,结冰期和非结冰期能量分配不同,冬季湖泊将储存的能量向大气传递;潜热通量和感热通量季节变化存在差异,但均有明显的昼夜变化特征。③湖气界面的感热通量在不同的月份也存在差异,感热以湖泊向大气传递为主;潜热通量夏半年远大于冬半年,在一天中6:00-8:00时处于最低值,15:00-16:00时达到峰值,在冬季会出现潜热向下输送现象。感热通量和潜热通量日变化呈负相关,湖面有效能量主要分配给潜热,湖泊同周围环境以水汽交换为主。④湖面平均蒸发速率为3.97 mm/d,累计蒸发量为1450±10 mm/a,同期的蒸发量是降水量的20多倍,湖泊主要靠地下水补给。这些结论可为进一步研究巴丹吉林沙漠腹地湖泊群的水循环及补给来源提供参考。     

地表热通量对陕南强降水的影响

通过对2002年6月8～9日陕南大暴雨天气过程中地表感热和潜热通量的数值模拟表明:地表感热、潜热通量和温度的区域性分布与高原东部特殊的地形分布有关,地表热通量和温度的等值线与地形等高线大致平行,平原低洼地区和山脉所在地特征明显,从而可以说明地形热力状况在陕西强降水中发挥重要作用;地表潜热作用大于地表感热,去掉地表潜热的作用后,模式对降水的模拟结果与实况偏差较大;地表感热使山脊降水减少,使平原、山谷降水增加,这与夜间的山谷风环流密不可分。     

巴丹吉林沙漠高大沙山近地层温湿廓线与能量交换特征

利用兰州大学冰川与沙漠研究中心科学观测实验站2015—2016年获得的高大沙山微气象数据,分析了巴丹吉林沙漠温湿廓线结构、土壤分层温度、辐射通量等特征,利用组合法和一维热传导方程分别计算了湍流通量及土壤热通量。结果表明：（1）近地层大气自下而上呈现近似等温或逆温分布,冬季逆温层厚度大于夏季。（2）初次观测到逆湿现象,比湿夏季最大,冬季最小,秋季和春季次之,全年平均约为4.2 g·kg^-1,高于塔克拉玛干沙漠。（3）土壤热通量在2月底至5月初振幅较大;感热通量具有显著的平均日变化特征,潜热通量平均日变化平稳,以0 W·m^-2为中心上下波动。能量交换以感热通量为主,陆-气温度差异是沙山感热通量变化的主要影响和控制因子。     

热带太平洋海域感热、潜热通量的时空特征*

本文利用“中美热带西太平洋海气相互作用研究”第1-8航次海面气象观测资料,计算分析了热带太平洋感热潜热通量的时空特征.分析结果表明在赤道海域,潜热通量远远大于感热通量.潜热和感热通量是从海面向大气输送的,且具有明显的年际变化和季节变化,日变化变幅甚小.     

沙区绿化对区域气候影响的数值模拟研究

利用GCM-SSiB全球大气环流谱模式,设计两组数值模拟试验(即控制试验(CE)和绿化面积扩大试验(GE))。研究了大陆绿化对我国区域气候变化的影响。模拟结果表明:沙区绿化后,年平均地表温度升高,海平面气压下降,纬向风速减弱、夏季风增强,冬季风减弱,夏季低空上升运动加强,冬季下沉运动减弱,降雨量显著增加,低层大气比湿、地表蒸发量、感热及潜热通量亦增加。绿化后气候趋向暖湿,极有利于生态环境建设和荒漠化的进一步治理。     

祁连山地区生态环境恶化对环境影响的数值模拟

利用中尺度模式MM5,依据祁连山地区复杂地形下生态环境恶化的事实,设计了一个控制试验和一个敏感性试验,数值模拟结果表明:MM5模式能够较好地模拟祁连山地区的降水;祁连山地区生态环境恶化对周围地区甚至较远地区的降水会产生较大的影响,区域平均降水减少约2％,对本地区的生态环境很不利;模拟区域感热通量增大,潜热通量减小,但是潜热通量变化的绝对值大于感热通量变化的绝对值,因此热通量是减小的;模拟区域气温和地面温度升高,同时土壤温度也升高。     

ERA40中北半球高纬地区冬季气候变化和冰-气相互作用特征分析

利用欧洲中期天气预报中心(ECMWF)再分析资料(ERA40)分析了最近几十年冬季北半球高纬地区的气候变化和冰-气相互作用特征。在全球增暖背景下,冬季北半球高纬地区增温幅度更大,但温度变化明显具有区域性特点。20世纪70年代末期开始,格陵兰海、巴伦支海及欧亚大陆大部分区域和北美大陆部分区域在增暖,而拉布拉多海、格陵兰和白令海峡区域却变冷。与此对应,中央北极区及气候冰岛低压中心海平面气压在降低,而再往南区域海平面气压在升高。从20世纪70年代开始,格陵兰海和巴伦支海给大气的感热通量和潜热通量增多,这说明由于气温增加,使得海冰密集度减小,海冰对海气感热通量和潜热通量交换的隔离层作用减小,通量交换大大增加。而在挪威海非海冰区,由于气温增加,海气温差减小,海洋给大气的感热通量和潜热通量减少。在拉布拉多海,由于气温降低,海气温差增大,使得海洋给大气的感热通量和潜热通量增加,有利于拉布拉多海海冰的增多。海平面气压、海冰密集度及表面感热通量和潜热通量之和对大气表面温度 EOF 展开第一模时间系数的线性回归结果均与各自的EOF 展开第一模空间分布特征接近。     

海冰在海气交换中的作用及其与海雾的关系

本文用了 1 999年夏季中国首次北极科学考察队对海冰、大气和海洋进行的同步和准同步的综合立体观测所获取的资料 ,研究海冰在海 气相互作用中扮演的角色。发现海冰的种类、分布、冰厚等变化对海气热交换都有重要影响。在浮冰区海洋以潜热的形式向大气输送热量 ,潜热通量与浮冰密集度的大小密切有关 ,浮冰越少潜热通量越大 ,潜热通量约为2 1～ 2 3 .6W /m2 ,潜热通量大于感热通量 ;在冰盖和大浮冰块上 ,大气以感热的形式向冰雪面上输送热量。新生的浮冰区或冰间湖是海气热交换最激烈的地方 ,是气候最敏感的区域 ,是北冰洋蒸汽雾生成的重要条件。用层结大气整体动力学输送法 ,计算了一次大范围的蒸汽雾过程的海气热交换 ,海洋向大气输送的热量总功率约为 1 4 8亿千瓦 ,相当于中国发电能力的 69倍 ,相当于大西洋向北冰洋输送热量平均功率的 1 / 2 0。北冰洋的夏季能够形成各种类型的海雾 :辐射雾、蒸汽雾和平流雾 ,其重要原因就是因为海冰的存在 ,使下垫面的性质复杂化 ,海气交换复杂化。     

北冰洋浮冰和开阔海面上的能量平衡特征

利用中国首次北极考察队于 1 999年 8月 1 9日～ 2 4日在北冰洋浮冰区获得的大气近地层垂直廓线和辐射等资料 ,依据相似理论方法 ,对比分析了北冰洋无冰海面和冰面上热平衡参数的变化特征。结果表明 ,海面与大气和冰面与大气之间相互作用的边界层物理过程差异十分明显。冰面吸收的净辐射仅为海面的 6%左右 ,主要消耗于感热输送和冰面融化过程 ,不足部分由水汽在冰面上凝结释放的潜热和冰中的热通量来补充。海面吸收的净辐射主要消耗于潜热输送过程 ,占净辐射的 50 % ,其余热量传向水体深层和用于感热输送 ,分别占净辐射的 2 6%和 2 4 %。由此可见 ,在北冰洋夏季 ,无冰海面有大量的水汽向大气输送 ,这对研究北冰洋地区大气边界层的季节变化过程是至关重要的     

黄土高原半干旱区陆面温度和能量的气候特征分析

利用黄土高原半干旱区“定西陆面过程综合观测试验站”2004年11月至2005年10月的各种陆面物理量综合资料,比较系统地研究了黄土高原半干旱区土壤温度、降水量、地表反照率、地表辐射分量和能量平衡分量的年变化和日变化特征及其影响机制。结果显示,黄土高原陆面过程特征与其他地区有很大不同。土壤温度变化向下传播速度约为2.5~3.5 h/10cm;地表反照率随土壤湿度的增大而减小,两者的相关系数达到了0.5338;而地表反照率随降雪量增大而增大,与降雪量的相关系数为0.6645;长波辐射年最大值出现的时间比总辐射迟1个月左右,年平均日变化中地表和大气对太阳辐射加热大约需要1个小时的响应时间; 潜热通量夏季是冬季的5倍多,感热通量有了两个比较明显的峰值,潜热通量、感热通量和土壤热通量的日峰值比净辐射滞后30 min~1 h。     

The role of Pacific water in the dramatic retreat of arctic sea ice during summer 2007

A model study is conducted to examine the role of Pacific water in the dramatic retreat of arctic sea ice during summer 2007.The model generally agrees with the observations in showing considerable seasonal and interannual variability of the Pacific water inflow at Bering Strait in response to changes in atmospheric circulation. During summer 2007 anomalously strong southerly winds over the Pacific sector of the Arctic Ocean strengthen the ocean circulation and bring more Pacific water into the Arctic than the recent(2000-2006) average.The simulated summer(3 months) 2007 mean Pacific water inflow at Bering Strait is 1.2 Sv,which is the highest in the past three decades of the simulation and is 20%higher than the recent average.Particularly ,the Pacific water inflow in September 2007 is about 0.5 Sv or 50%above the 2000-2006 average.The strengthened warm Pacific water inflow carries an additional 1.0×10~(20) Joules of heat into the Arctic,enough to melt an additional 0.5 m of ice over the whole Chukchi Sea.In the model the extra summer oceanic heat brought in by the Pacific water mainly stays in the Chukchi and Beaufort region,contributing to the warming of surface waters in that region.The heat is in constant contact with the ice cover in the region in July through September.Thus the Pacific water plays a role in ice melting in the Chukchi and Beaufort region all summer long in 2007,likely contributing to up to 0.5 m per month additional ice melting in some area of that region .     

北极阿拉斯加巴罗地区夏季降水化学特征

本文根据１９９４年８～９月份阿拉斯加北坡巴罗地区降水的实测资料，初步探讨了本区夏季降水的化学特征及环境意义。结果表明：巴罗地区夏季降水的ｐＨ值比冬季高，平均值接近与大气ＣＯ２平衡时纯水的酸度状况；电导率值普遍较低，个别电导率值较高的样品可能与海盐粒子有关；样品的主要离子浓度与北极其它地区和青藏高原的降水化学成分相当，ｅｘＳＯ４２－基本接近于零，反映了受人类活动影响非常小的自然本底状况。研究认为巴罗地区是进行北极地区现代环境状况研究的理想地区之一。     

Anomalous sea-ice reduction in the Eurasian Basin of the Arctic Ocean during summer 2010

During the summer of 2010 ice concentration in the Eurasian Basin, Arctic Ocean was unusually low. This study examines the sea-ice reduction in the Eurasian Basin using ice-based autonomous buoy systems that collect temperature and salinity of seawater under the ice along the course of buoy drift. An array of GPS drifters was deployed with 10 miles radius around an ice-based profiler, enabling the quantitative discussion for mechanical ice divergence/convergence and its contribution to the sea-ice reduction. Oceanic heat fluxes to the ice estimated using buoy motion and mixed-layer (ML) temperature suggest significant spatial difference between fluxes under first-year and multi-year ice. In the former, the ML temperature reached 0.6 K above freezing temperature, providing >60–70 W m^?2 of heat flux to the overlying ice, equivalent to about 1.5 m of ice melt over three months. In contrast, the multiyear ice region indicates nearly 40 W m^?2 at most and cumulatively produced 0.8 m ice melt. The ice concentration was found to be reduced in association with an extensive low pressure system that persisted over the central Eurasian Basin. SSM/I indicates that ice concentration was reduced by 30–40% while the low pressure persisted. The low ice concentration persisted for 30 days even after the low dissipated. It appears that the wind-forced ice divergence led to enhanced absorption of incident solar energy in the expanded areas of open water and thus to increased ice melt.     

Observed transport estimates between the North Atlantic and the Arctic Mediterranean in the Iceland–Scotland region

The Arctic Mediterranean is the ocean area north of the Greenland-Scotland Ridge. Exchanges between this region and the North Atlantic both provide the main source for production of North Atlantic Deep Water and supply heat and salt to the northern oceans. The exchange occurs through several gaps in the ridge; in terms of volume flux the Iceland-Scotland Gap is the most important one as it carries more than half the total, with approximately three quarters of the total inflow and one third of the total outflow. The Nordic WOCE observational system was initiated to monitor the exchanges through this gap and it has provided data that allow estimates of typical fluxes and their seasonal variation. The flux measurements show that most of the Atlantic inflow to the Arctic Mediterranean returns as overflow and hence the processes forming intermediate and deep waters in the Arctic Mediterranean are the main forcing mechanism for the Atlantic inflow. The inflow between Iceland and Scotland seems to be a maximum in late winter while the Faroe Bank Channel overflow is strongest in late summer. Using the results from the Nordic WOCE system it has been possible to interpret historical observations from Ocean Weather Ship Station M and conclude that the flux of the Faroe Bank Channel overflow decreased in magnitude from 1950 to 2000.     

广州市冬夏季热岛的空间格局及其差异分析

利用2003年夏季和冬季两景Landsat ETM图像的热红外波段反演了广州市地表温度(LST)的空间变化,并对冬季和夏季热岛空间分布特征的差异及成因进行了分析。结果表明,广州市冬季和夏季热岛的空间分布具有明显的规律性,并且空间分布、强度差异很大;夏季热岛集中区主要是建筑物和道路等非渗透表面组成地域以及人口最密集区域,冬季热岛的分布主要与工业区和运输业的分布相伴。引起这种差异的原因主要是城市能耗布局、下垫面性质、冬夏季生物学和热学特征综合作用的结果。     

敦煌戈壁冬夏季地表辐射与能量平衡特征对比研究

利用敦煌戈壁夏（2006年7月）、冬（2007年1月1—10日）季观测得到的微气象资料,比较了夏、冬季敦煌戈壁的地表辐射平衡、能量平衡特征。分析了地表反照率（Albedo）与土壤特性的关系,发现地表反照率和表层土壤温度日变化呈反相关;冬季地表反照率和土壤湿度的线性相关差,夏季地表反照率和土壤湿度的线性相关性好;地表反照率和土壤热通量呈反相关,并且冬季二者的拟合性好于夏季。分析了降水前后各能量通量的变化,发现阵雨时感热H是变小的,降雨过后H和净辐射Rn有明显的增大,土壤热通量Gn在降雨过后也有增大,潜热LE变化微弱,对阵性降水强迫后的非平衡态的张弛时间大约为3 d。     

Contribution of a pathway through the Arctic Ocean to the recent reduction in the ice cover

The sea ice cover in the Arctic Ocean has been reducing and hit the low record in the summer of 2007.The anomaly was extremely large in the Pacific sector. The sea level height in the Bering Sea vs.the Greenland Sea has been analyzed and compared with the current meter data through the Bering Strait.A recent peak existed as a consequence of atmospheric circulation and is considered to contribute to inflow of the Pacific Water into the Arctic Basin.The timing of the Pacific Water inflow matched with the sea ice reduction in the Pacific sector and suggests a significant increase in heat flux.This component should be included in the model prediction for answering the question when the Arctic sea ice becomes a seasonal ice cover.     

Heat flux calculations for Mackenzie and Yukon Rivers

This study analyzes long-term (40–60 years) discharge and water temperature records collected near the basin outlets of the Yukon and Mackenzie Rivers. It defines seasonal cycles of discharge, water temperature (WT), and heat flux (HF) for the basins, and compares their main features to understand their similarity and difference. Both rivers have similar hydrographs, i.e. low flows in winter and high discharge in summer, with the peak flood in June due to snowmelt runoff. Mackenzie River has many large lakes and they sustain the higher base flows over the fall/winter season. Mackenzie basin is large with high precipitation, thus producing 50% more discharge than the Yukon River to the Arctic Ocean. The WT regimes are also similar between the two rivers. Yukon River WT is about 2–3 °C warmer than the Mackenzie over the open water months. Both rivers have the highest WT in the mid summer and they transport large amount of heat to the polar ocean system. Yukon River monthly HF is lower by 10–60% than the Mackenzie mainly due to smaller discharge. Mackenzie River heat transport peaks in July, while the Yukon HF reaches the maximum in June and July. These results provide critical knowledge of river thermal condition and energy transport to the northern seas. They are useful for large-scale climate and ocean model development and validation, and climate/hydrology change research in the northern regions.     

Radiation climate variability in Svalbard: surface and satellite observations

This paper performs a climatological investigation of the surface radiation budget (SRB) in Svalbard, on the basis of the Norwegian Polar Institute's radiation measurements from Ny-Ålesund (1981-1997) and the NASA/Langley Surface Radiation Budget Dataset (1983-1991). The radiation climate is related to meteorological conditions and surface properties, and compared to surface radiation fluxes measured from space. The natural variability of the short-wave and long-wave radiation fluxes in Ny-Ålesund is generally governed by the large annual variation in the incoming light with polar night and polar day conditions, the large changes of surface albedo - especially during spring - and the atmospheric circulation with frequent cyclone passages during winter with alternating periods of warm, humid maritime air from the south and cold, dry Arctic air from the north.
Comparison with the satellite derived surface radiation fluxes shows that NyÅlesund is to a large extent influenced by the "ocean" climate to the west of Svalbard during the summer and autumn, but has a more "continental" radiation climate representative of the more central parts of the island during winter and spring. Ny-Ålesund is located in a fiord on the north-west coast of Svalbard, where the ocean cloud cover and the Arctic sea fog play an important role during the summer. During the winter and spring, however, the fiords are frozen and the drift ice covers a large extent of the surrounding ocean.     

A temperature inversion in "Chinese Arctic Research Expedition 1999

Using the boundary layer observation data collected by "Arctic Upper Air Observation 1999" in Chinese Arctic Research Expedition 1999, a strong temperature inversion in summer is studied. It shows that the intensity (6.3℃/(100 m)) is much stronger than the climatology average value in summer and winter. The temperature inversion took on a remarkable diurnal variation. The intensity of inversion gradually weakened from night to daytime.