共查询到19条相似文献，搜索用时 328 毫秒
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2010年春季至夏季在中山站附近的固定冰面开展了固定冰反照率观测.在春夏过渡期,观测期间的表面反照率呈下降趋势,平均反照率从9月的0.80下降到12月的0.62,整个观测期间的平均值为0.70.雪厚是影响反照率变化的重要因子,融化前期的反照率受表面温度影响较大,干雪期反照率对表面温度并不敏感.降雪可通过增加表面雪厚和减小表面积雪粒径显著增加反照率,云层则可通过吸收入射太阳光中的近红外波段增加反照率,降雪和阴天反照率可比晴天观测平均增加0.18和0.06;吹雪则可通过改变积雪光学厚度导致反照率发生显著变化.受太阳天顶角变化和积雪变性的共同影响,晴天或少云时的反照率在上午随太阳天顶角呈准线性递减,下午则几乎不发生变化;最高值、最低值分别出现在凌晨和下午.本文提出了一组分别表述厚干雪、薄干雪和湿雪反照率日变化的参数化方案,通过太阳天顶角的线性函数隐式考虑进了积雪变性的影响.相比常数反照率方案,该参数化方案能有效提高对反照率日变化的估算能力. 相似文献
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收集康定地震区及周边（99.6°~105.2°E，27.8°~33.0°N范围内）连续GPS观测站的资料求解站速度场，采用刚性-线弹性运动方程计算方法，拟合计算得到研究区域规格网格点（0.4°×0.4°）的速度值和主应变率值。基于该结果分析研究区内的运动特征和应变场变化情况，并讨论其与地震孕育发生的关系。分析结果表明，芦山7.0级地震发生前研究区呈现应变能量积累态势，而地震之后研究区呈应变能量释放调整态势，2014年康定地震的发生就是该区构造运动调整下的产物。 相似文献
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2016年12月8日呼图壁县发生MS6.2地震，由于初始定位误差较大，余震序列分布离散，对呼图壁地震的发震断层尚不清楚。本研究采用CAP方法反演主震及余震中MS ≥ 3.5地震的震源机制解，并采用双差定位方法对余震进行重定位，得到了637个地震的震源参数。结果显示，呼图壁地震主震的最佳双力偶节面解为：节面Ⅰ走向82°，倾角18°，滑动角61°；节面Ⅱ走向292°，倾角74°，滑动角98°。其中节面Ⅱ为本次地震的破裂面。重定位后，主震的震源位置被重定为（86.36°E，43.79°N），震源深度14 km，根据余震的分布特点、震源机制解特征和区域构造特征，呼图壁地震的发震断层并不是南倾的准噶尔南缘断裂，而是在其北边的霍尔果斯-玛纳斯-吐谷鲁断裂带上的一个反冲断层。在北天山区域内，由于构造反转的作用，存在诸多倾角在45°~55°之间的北倾的断层。根据GPS的资料显示，天山北部地区的应力在新生代晚期已开始积累，这增加了天山北部前缘的发震概率。 相似文献
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洱海湖气界面水汽和二氧化碳通量交换特征 总被引：2，自引：0，他引：2
基于2012年涡动相关法取得的洱海湖气之间湍流通量资料,计算了湖面反照率、空气动力学粗糙度和整体输送系数等湖气交换过程的基本物理参数;分析高原湖泊表面动量通量、感热通量、潜热通量和二氧化碳通量的变化特征及其主要的控制因子;采用神经网络法对缺失蒸发量数据进行填补,估算了洱海湖面全年蒸发量。2012年全年蒸发量为（1165±15）mm,大于年实际降水量（2012年的年降水量为818mm）。洱海局地环流在全年范围内较显著;全年主导风向为东南（谷风／湖风）和西北风（山风／陆风）。高原湖泊感热通量通常只有每平方米几十瓦,通常午后感热通量为负值;即湖面向大气输送热量。夏季湖泊大气界面感热通量最大值出现在清晨,与湖气温差的出现时间一致;在白天湖面的有效能量主要分配为潜热通量;湖气温差和水汽压差分别是感热通量和潜热通量日变化的主要控制因子。湖气界面二氧化碳通量除夏季存在弱的吸收外,其余季节（冬季）表现为弱的排放。湖面反照率的季节变化规律与太阳高度角的季节变动有关,同时湖面反照率与水的浑浊度等有关。与实际观测得到的湖面反照率相比,CLM4湖泊模式在冬季低估（夏季高估）了湖面反照率。 相似文献
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本文应用ISOLA近震全波形方法，以2017年1月4日西藏仲巴4.7级地震为例，反演稀疏台网记录的中小地震震源机制解。该地震反演所得最佳双偶机制参数为：节面Ⅰ的走向109°/倾角85°/滑动角-177°，节面Ⅱ的走向19°/倾角88°/滑动角-4°，最佳矩心位置为30.590°N、83.784°E，最佳质心深度为6km，矩震级MW4.6。震源机制反演结果表明此次地震是一次走滑型为主的事件，其与震源区域附近历史地震震源机制解具有相同性质。本文还应用CSPS初动扫描法，利用P波初动资料和近震波形联合约束反演此次地震的震源机制，并与ISOLA近震全波形反演结果进行比较，结果表明，联合少量台站的的三分量波形数据，能够定量地判断最佳震源机制解，降低了P波初动反演结果的非唯一性，同时也约束了由于少量台站参与全波形反演引起的解的不稳定性。本文研究为中小地震震源参数测定提供了一种简单有效的方法，具有较高的稳定性和可靠性。 相似文献
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采用CAP（Cut and Paste）方法反演了2016年1月21日青海门源MS6.4地震的震源机制解，其最佳双力偶解节面I走向339°，倾角49°，滑动角111°：节面Ⅱ走向129°，倾角45°，滑动角68°，矩震级MW5.92，矩心震源深度约为9 km，地震破裂类型为逆冲型地震。结合余震序列展布及震区的活动构造特征，判定发震断层面为节面I，推测此次地震的发震断裂为冷龙岭断裂。 相似文献
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地震频次场是描述地震发生频次时空特征的一种数学方法。将2008年5月12日汶川8.0级地震震中附近区域（30.0°~33.0° N、101.5°~105.5° E）作为研究对象,以自然正交函数展开方法分析频次场典型场时间因子的时间变化特征。当取前8个特征值对应的典型场时,拟合精度可达0.936 8;其中6个典型场显示有异常变化,占总场比重的0.691 1;异常出现时间最早在2004年9月,即震前3年7个月,最迟在震前1个多月,表现出短临异常特征。研究结果表明利用地震频次场方法能够较为理想地提取汶川8.0级地震震前异常。 相似文献
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2019年6月17日在四川宜宾市长宁县（28.34°N，104.90°E）发生MS6.0地震，余震发育。本文利用区域测震台网的地震观测数据基于CAP方法计算了28°~29°N，104°~105°E范围内的14个MS>3.0以上地震的震源机制解，结合全球矩心矩张量目录和部分前人研究结果中该区域的共27个震源机制解数据，应用MSATSI软件反演了研究区域的应力场。将研究区域按0.1°×0.1°划分成25个应力网格，最终得到9个网格的应力分布结果，大多数应力场方向稳定，根据主震所在应力网格点得到主震的断层类型为主逆冲型。本文研究成果为四川长宁地区的孕震机理、活动构造以及地震趋势判定提供了可靠的参考依据。 相似文献
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Stream surface albedo plays a key role in the energy balance of rivers and streams that are exposed to direct solar radiation. Most physically based analyses and models have incorporated a constant stream albedo between 0.03 and 0.10, based primarily on measurements from low‐gradient streams with low suspended sediment concentrations. However, albedo should vary with solar elevation angle, suspended sediment concentration, aeration, and fraction of direct versus diffuse radiation. The objective of this study was to quantify the dependence of albedo of mountain streams on the controlling factors and to develop a predictive model for use in physically based analysis and modelling of stream temperature, especially for future climate and land‐use scenarios. Stream surface albedo was measured at nine sites with a variety of gradients and suspended sediment characteristics in the southern Coast Mountains of British Columbia, Canada. As expected, albedo of low‐gradient, non‐white water (flatwater) streams increased with solar elevation angle, suspended sediment concentration, and proportion of diffuse to direct solar radiation, ranging between 0.025 during cloudy periods over clear water to 0.25 for turbid water at elevation angles of less than 20°. Albedo was enhanced in steep reaches or at channel steps and cascades where flow was visibly aerated, with a range of 0.09 to 0.33. In clear weather, albedo exhibited notable diurnal variability at flatwater sampling sites. For example, during late summer, surface albedo typically fluctuated between 0.08 and 0.15 on a daily basis at a flatwater site on the highly turbid, glacier‐fed Lillooet River. Multiple regression models explained approximately 60% and 40% of the variance under cross validation for flatwater and white water data subsets, respectively, with corresponding root mean square errors of approximately 0.02 and 0.06. 相似文献
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The effect of sunrise in time variations in the electric field in the near-Earth atmosphere at the Kamchatka Paratunka observatory has been studied. Twenty-nine records under fair-weather conditions have been selected. It has been indicated that the estimated effect parameters—the times of the effect’s onset and field strength maximum relative to the sunrise time, as well as the ratio of the strength maximum to its value before sunrise and the effect duration—coincide with the previously published data. Thereby, the conclusion is confirmed that the sunrise effect in diurnal variations in the electric field in the near-Earth atmosphere is related to the turbulence and convection processes in the atmospheric boundary layer at a change in atmospheric temperature. 相似文献
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The data of the DMSP F7 spacecraft are used for studying the influence of the geomagnetic dipole tilt angle on the latitudinal position of auroral
precipitation boundaries in the nighttime (2100–2400 MLT) and daytime (0900–1200 MLT) sectors. It is shown that, in the nighttime
sector, the high-latitude zone of soft diffuse precipitation (SDP) and the boundary of the polar cap (PC) at all levels of
geomagnetic activity are located at higher and lower latitudes relative to the equinox period in winter and summer, respectively.
The position of boundaries of the diffuse auroral precipitation zone (DAZ) located equatorward from the auroral oval does
not depend on the season. In the daytime sector, the inverse picture is observed: the SDP precipitation zone takes the most
low-latitude and high-latitude positions in the winter and summer periods, respectively. The total value of the displacements
from winter to summer of both the nighttime and daytime boundaries of the PC is ∼2.5°. A diurnal wave in the latitudinal position
of the nighttime precipitation boundaries is detected. The wave is most pronounced in the periods of the winter and fall seasons,
is much weaker in the spring period, and is almost absent in summer. The diurnal variations of the position of the boundaries
are quasi-sinusoidal oscillations with the latitude maximum and minimum at 0300–0500 and 1700–2100 UT, respectively. The total
value of the diurnal displacement of the boundaries is ∼2.5° of latitude. The results obtained show that, undergoing seasonal
and diurnal variations, the polar cap is shifted as a whole in the direction opposite to the changes in the tilt angle of
the geomagnetic dipole. The seasonal displacements of the polar cap and its diurnal variations in the winter period occur
without any substantial changes in its area. 相似文献
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M. P. Petrov A. Yu. Terzhevik N. I. Palshin R. E. Zdorovennov G. E. Zdorovennova 《Water Resources》2005,32(5):496-504
Based on the analysis of data of many-year actinometric observations, a considerable temporal (interannual, seasonal, synoptic, and diurnal) and spatial variability of the albedo of the snow-and-ice cover of a shallow lake is shown. The ranges of variations in the albedo of snow and ice for a wide spectrum of the state of surface and weather conditions are presented. The variability of the thickness and structure of snow-and-ice cover is analyzed for different periods in winter. The results of field experiments aimed to determine the degree of absorption of solar radiation by snow and ice are presented. The effective coefficients of absorption of solar radiation by snow and ice are determined. The comparison of the observed and calculated values of the under-ice radiation has shown that the determined coefficients adequately describe the absorption of solar radiation by snow-and-ice cover. 相似文献
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This study analyzes the TEC data during 1998–2007, observed by the AREQ (16.5°S, 71.5°W) GPS station to investigate the equatorial ionospheric variations under geomagnetic quiet-conditions. The diurnal TEC values generally have a maximum value between 1330 and 1500 LT and a minimum around 0500 LT. For the seasonal variation, the semi-annual variation apparently exists in the daytime TEC with two peaks in equinoctial months. In contrast, this semi-annual variation is not found in the nighttime. Furthermore, the results of the annual variation show that the correlation between the daytime TEC value and the solar activity factor is highly positive. 相似文献
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Tephra deposition on glaciers and ice sheets on Mars: Influence on ice survival, debris content and flow behavior 总被引：1，自引：1，他引：0
We examine the consequences of pyroclastic deposits being emplaced onto ice layers on Mars, both those in the polar caps and those forming glaciers on the flanks of some of the large shield volcanoes. We show that layers of pyroclasts greater than a few meters in thickness, whether emplaced cold (as fall deposits) or hot (as pyroclastic density current deposits) act almost exclusively to protect ice layers beneath them from sublimation, irrespective of whether they are emplaced at high or low elevations or high or low latitudes. Layers less than about 2 m thick, on the other hand, can cause significant ice loss by raising the surface temperature due to their low albedo and then transmitting that increased temperature to the underlying ice, especially on a diurnal time scale. This can have a significant bearing on the emplacement history of polar water ice and on the survival time of glacial ice on shield volcano flanks. A key factor in the latter case is the timing of the episodic volcanic activity relative to the cycles of climate change driven by Mars' obliquity and eccentricity variations. 相似文献
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利用F2层峰值处的Chapman标高Hm可以构建电离层顶部的电子浓度剖面.本文通过对北京站(40.3°N,116.2°E)从2010年1月到2014年5月的电离层频高图人工度量后获得了F2层峰值处的Chapman标高Hm,分析研究了Hm随周日、季节和太阳活动变化,并探讨了Hm与F2层特征参数foF2、hmF2以及IRI底部厚度参数B0的相关性.研究表明,(1)北京地区标高Hm的周日变化明显,在正午左右有最大值,夏季和春秋季的最小值出现在午夜左右,而冬季有两个谷值,在日出后和20:00LT左右; Hm在日出前有较小的增加,但不是很明显;(2)白天标高Hm有明显的季节变化,夏季最强,冬季最弱,而夜间的季节变化较小;(3)Hm随太阳活动的增强而增大,地磁扰动会引起Hm偏离正常水平;(4)Hm与hmF2相关性很弱,但白天和夜间各自的相关性较强,并且夜间大于白天;Hm与B0有很强的相关性;(5)由IRI2012给出的B0与Hm在冬季的相关性很小,表明IRI模式还需要进一步改进. 相似文献
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The zone of anomalous diurnal variations in foF2, which is characterized by an excess of nighttime foF2 values over daytime ones, has been distinguished in the Southern Hemisphere based on the Intercosmos-19 satellite data.
In English literature, this zone is usually defined as the Weddell Sea anomaly (WSA). The anomaly occupies the longitudes
of 180°–360° E in the Western Hemisphere and the latitudes of 40°–80° S, and the effect is maximal (up to ∼5 MHz) at longitudes
of 255°–315° E and latitudes of 60°–70° S (50°–55° ILAT). The anomaly is observed at all levels of solar activity. The anomaly
formation causes have been considered based on calculations and qualitative analysis. For this purpose, the longitudinal variations
in the ionospheric and thermospheric parameters in the Southern Hemisphere have been analyzed in detail for near-noon and
near-midnight conditions. The analysis shows that the daytime foF2 values are much smaller in the Western Hemisphere than in the Eastern one, and, on the contrary, the nighttime values are
much larger, as a result of which the foF2 diurnal variations are anomalous. Such a character of the longitudinal effect mainly depends on the vertical plasma drift
under the action of the neutral wind and ionization by solar radiation. Other causes have also been considered: the composition
and temperature of the atmosphere, plasma flows from the plasmasphere, electric fields, particle precipitation, and the relationship
to the equatorial anomaly and the main ionospheric trough. 相似文献