1990-2020年间念青唐古拉山中段北坡边坝地区冰川变化及气候响应

念青唐古拉山作为青藏高原东南缘重要山古冰川分布区,受季风影响,各区域冰川变化特征差异明显。论文通过Landsat TM/ETM+/OLI资料、ASRTMGDEM与气象数据,采用比值—阈值法、目视解译和VOLTA模型,结合实地考察,对1990—2020年间念青唐古拉山中段北坡边坝地区现代冰川进退状况、面积变化、冰储量变化以及冰川变化对气候变化响应特征进行研究。结果表明：① 1990—2020年5条冰川(玉贡拉冰川、玛拉波冰川、祥格拉冰川、孔嘎冰川、贡日—庚东冰川)末端高程逐渐升高,面积和冰储量分别减少30.38 km²和4.64 km³,总体缩减并呈现加速趋势。② 冰川冰储量减少0.14~1.92 km³,总体变化率为0.40%·a^-1。2020年上述5条冰川储量占1990年冰川储量的比例分别为0.70、0.99、0.98、0.91和0.82,显示出冰川规模越大,在短时间尺度的变化量越小。③ 气象数据分析显示,1990—2020年研究区冰川变化受气温升高主导,平均气温变化率为0.51 ℃。水热组合呈现温度升高—降水减少,且在最后10 a日益显著,预测未来冰川变化仍受气温控制并呈加速退缩趋势。④ 区域对比研究表明,念青唐古拉山冰川面积变化总体呈退缩状态,但各区域冰川变化特征差异明显。同时,不同研究方法对同一冰川区冰储量模拟结果相差较大,相对误差范围为34.45%~115.49%,精确的冰储量可对比研究方法仍有待进一步研究。     

利用轨迹大数据进行城市道路交叉口识别及结构提取

交叉口是城市交通路网生成、更新的重要组成部分。本文基于车辆时空轨迹大数据,提出了一种城市交叉口自动识别方法。该方法首先通过轨迹跟踪识别轨迹数据中包含的车辆转向点对;然后基于距离和角度的生长聚类方法进行转向点对的空间聚类,并采用基于局部点连通性的聚类方法识别交叉口;最后利用交叉口范围圆和转向点对提取城市各级别路网下的交叉口结构。以武汉市出租车轨迹大数据为例,对武汉市城区内189个交叉口进行了探测。试验结果表明,本文所提方法可以准确地从轨迹大数据中识别出城市交叉口及其结构。     

Impact of ambient temperature on spring-based relative gravimeter measurements

In this paper, we investigate the impact of ambient temperature changes on the gravity reading of spring-based relative gravimeters. Controlled heating experiments using two Scintrex CG5 gravimeters allowed us to determine a linear correlation (R \(^{2}>\) 0.9) between ambient temperature and gravity variations. The relation is stable and constant for the two CG5 we used: ?5 nm/s\(^{2}/^\circ \)C. A linear relation is also seen between gravity and residual sensor temperature variations (R \(^{2}>\) 0.75), but contrary to ambient temperature, this relation is neither constant over time nor similar between the two instruments. The linear correction of ambient temperature on the controlled heating time series reduced the standard deviation at least by a factor of 2, to less than 10 nm/s\(^{2}\). The laboratory results allowed for reprocessing the data gathered on a field survey that originally aimed to characterize local hydrological heterogeneities on a karstic area. The correction of two years of monthly CG5 measurements from ambient temperature variations halved the standard deviation (from 62 to 32 nm/s\(^{2}\)) and led us to a better hydrological interpretation. Although the origin of this effect is uncertain, we suggest that an imperfect control of the sensor temperature may be involved, as well as a change of the properties of an electronic component.     

Decameter mid-latitude sporadic-E irregularities in relation with gravity waves

HF radar observations of mid-latitude sporadic-E irregularities carried out with the Valensole radar in South France are compared with simultaneous ionosonde measurements underneath the irregularity zones. In a previous study of Valensole radar data, it has been shown that HF backscatter from the night-time mid-latitude E region is usually associated with largescale wave-like modulations. To obtain more information on the geophysical conditions prevailing during backscatter events, a new experiment was performed which also included a vertical ionosonde beneath the scattering region. The data to be presented here are from two periods when radar scattering appeared simultaneously with large variations in the virtual height and the Doppler velocity of F-layer reflected echoes measured with the vertical ionosonde, indicating very clearly the passage of atmospheric gravity waves (AGWs). The effect of the atmospheric waves on the sporadic-E layer is not always as marked as it is in the F region. In the first event, the passage of the AGWs is accompanied by an upward followed by a downward movement of the Es-layer. The apparent descending movement of the Es-layer from 135 to 110km in less than 10 min corresponded to a positive (downward) Doppler velocity of 35 m/s measured by the vertical ionosonde, and was accompanied by a range variation in the radar scattering region with a negative rate of about 90–110 m/s. In the second event, the Es-layer is not as strongly disturbed as in the previous one, but, nevertheless, the range variations of the scattering region can still be associated with height fluctuations of the Es-layer.     

Impact of reservoir operation and climate change on the hydrological regime of the Sesan and Srepok Rivers in the Lower Mekong Basin

The transboundary Sesan and Srepok sub-basins (2S) are the “hot-spot” areas for reservoir development in the Lower Mekong region, with 12 reservoirs built in the Vietnam territory. This study examines the impacts of reservoir operations in Vietnam and projected climate change on the downstream hydrologic regime of the 2S Rivers by jointly applying the Soil Water Assessment Tool (SWAT) and Water Evaluation and Planning (WEAP) models. Different scenarios of reservoir operation are considered and simulated to assess their impact on annual, seasonal, and monthly flow regimes under maximum hydropower capacity generation with and without taking into account the minimum flow requirement downstream near the Vietnam border with Cambodia. The precipitation and temperature projections from the high-resolution regional climate model HadGEM3-RA under two Representative Concentration Pathways, 4.5 and 8.5, of HadGEM2-AO are used as future climate change scenarios for the impact assessment. The study results show that reservoir operation leads to an increase in the dry season stream flows and a decrease in the wet season stream flows. The monthly flow regime exhibits considerable changes for both the Sesan and Srepok Rivers but with different magnitudes and patterns of increase and decrease. Climate change is likely to induce considerable changes in stream flows, though these changes are comparatively lower than those caused by reservoir operation. Climate change is likely to have both counterbalancing and reinforcing effects over the impact of reservoir operation, reducing changes during dry season but increasing changes in most of the other months.     

南极海冰面积变化特性及其与赤道太平洋海表面温度的联系

南极海冰面积变化特性及其与赤道太平洋海表面温度的联系陈锦年,乐肯堂,于康玲,张彦臣（中国科学院海洋研究所,青岛２６６０７１）（青岛海洋大学,青岛２６６００３）关键词南极海冰面积,赤道太平洋海表面温度,厄尔尼诺１引言８０年代以前,人们对南极实地考察、资...     

论中国湖泊渔业发展趋势

由封闭到开放、从无序到有序演进, 是中国湖泊渔业发展的客观规律。目前中国湖泊渔业已迈过广封闭式的原始渔业, 半封闭式的传统渔业, 向开放式的耗散结构渔业前进.中国湖泊渔业巧妙利用多维空间进行立体开发的多种开放经笄模式, 如根据水层深浅开展立体利用, 根据地形特点进行不同形式的围栏养殖, 根据而积大小分别采取保护、增殖、养殆措施, 这些都取得r初步成功。现代开放式湖泊渔业继续向纵深发展, 呈现向耗散结构渔业逼近的趋势。     

Weathering,erosion and sediment composition in a high‐gradient river,Calabria, Italy

Source rock lithology and immediate modifying processes, such as chemical weathering and mechanical erosion, are primary controls on fluvial sediment supply. Sand composition and Chemical Index of Alteration (CIA) of parent rocks, soil and fluvial sand of the Savuto River watershed, Calabria (Italy), were used to evaluate the modifications of source rocks through different sections of the basin, characterized by different geomorphic processes, in a sub‐humid Mediterranean climate. The headwaters, with gentle topography, produce a coarse‐grained sediment load derived from deeply weathered gneiss, having sand of quartzofeldspathic composition, compositionally very different from in situ degraded bedrock. Maximum estimated CIA values suggest that source rock has been affected significantly by weathering, and it testifies to a climatic threshold on the destruction of the bedrock. The mid‐course has steeper slopes and a deeply incised valley; bedrock consists of mica‐schist and phyllite with a very thin regolith, which provides large cobble to very coarse sand sediments to the main channel. Slope instability, with an areal incidence of over 40 per cent, largely supplies detritus to the main channel. Sand‐sized detritus of soil and fluvial sand is lithic. Estimated CIA value testifies to a significant weathering of the bedrock too, even if in this part of the drainage basin steeper slopes allow erosion to exceed chemical weathering. The lower course has a braided pattern and sediment load is coarse to medium–fine grained. The river cuts across Palaeozoic crystalline rocks and Miocene siliciclastic deposits. Sand‐sized detritus, contributed from these rocks and homogenized by transport processes, has been found in the quartzolithic distal samples. Field and laboratory evidence indicates that landscape development was the result of extensive weathering during the last postglacial temperature maximum in the headwaters, and of mass‐failure and fluvial erosional processes in the mid‐ and low course. Copyright © 2000 John Wiley & Sons, Ltd.     

Effects of self-attraction and loading at a regional scale: a test case for the Northwest European Shelf

The impact of the self-attraction and loading effect (SAL) in a regional 2D barotropic tidal model has been assessed, a term with acknowledged and well-understood importance for global models but omitted for boundary-forced, regional models, for which the implementation of SAL is non-trivial due to its non-local nature. In order to understand the impact of the lack of SAL effects in a regional scale, we have forced a regional model of the Northwest European Continental Shelf and the North Sea (continental shelf model (CSM)) with the SAL potential field derived from a global model (GTSM), in the form of a pressure field. Impacts have been studied in an uncalibrated setup and with only tidal forcing activated, in order to isolate effects. Additionally, the usually adopted simple SAL parameterization, in which the SAL contribution to the total tide is parameterized as a percentage of the barotropic pressure gradient (typically chosen 10%), is also implemented and compared to the results obtained with a full SAL computation. A significant impact on M2 representation is observed in the English Channel, Irish Sea and the west (UK East coast) and south (Belgian and Dutch Coast) of the North Sea, with an impact of up to 20 cm in vector difference terms. The impact of SAL translates into a consistent M2 amplitude and propagation speeds reduction throughout the domain. Results using the beta approximation, with an optimal domain-wide constant value of 1.5%, show a somewhat comparable impact in phase but opposite direction of the impact in amplitude, increasing amplitudes everywhere. In relative terms, both implementations lead to a reduction of the tidal representation error in comparison with the reference run without SAL, with the full SAL approach showing further impacted, improved results. Although the overprediction of tidal amplitudes and propagation speeds in the reference run might have additional sources like the lack of additional dissipative processes and non-considered bottom friction settings, results show an overall significant impact, most remarkable in tidal phases. After showing evidence of the SAL impact in regional models, the question of how to include this physical process in them in an efficient way arises, since SAL is a non-local effect and depends on the instantaneous water levels over the whole ocean, which is non-trivial to implement.     

基于手机位置数据的四川九寨沟7.0级地震人流分析

2017年8月8日四川九寨沟7.0级震后,浙江省地震局利用大数据采集了1031.99万条手机位置记录和4.46万个空间格网位置。本文结合24hr连续定位的手机数据,使用手机位置数据分别对九寨沟灾区人口从时间和地理维度上进行了量化分析,估计了多维人口分布的偏差,同时,探讨了剔除微观误差数据用户来估算灾区通讯基站退服分布的方法。该项工作为震后快速获取灾区人口实时动态分布提供了有效途径,同时也为地震灾害评估提供了较准确的依据。