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21.
Monitoring glacier and supra-glacier lakes from space in Mt. Qomolangma region of the Himalayas on the Tibetan Plateau in China 总被引:4,自引:2,他引:4
Alfred Stein 《山地科学学报》2009,6(3):211-220
Because of the large number and remoteness, satellite data, including microwave data and optical imagery, have commonly been used in alpine glaciers surveys. Using remote sensing and Geographical Information System (GIS) techniques, the paper presents the results of a multitemporal satellite glacier extent mapping and glacier changes by glacier sizes in the Mt. Qomolangma region at the northern slopes of the middle Himalayas over the Tibetan Plateau. Glaciers in this region have both retreated and advanced in the past 35 years, with retreat dominating. The glacier retreat area was 3.23 km2 (or o.75 km^2 yr^-1 during 1974 and 1976, 8.68 km^2 (or 0.36 km^2 yr^-1 during 1976 and 1992, 1.44 km^2 (or 0.12 km^2 yr^-1) during 1992-2ooo. 1.14 km^2 (or 0.22 km^2 yr^-1 during 2000-2003, and 0.52 km^2 (or 0.07 km^2 yr^-1 during 2003-2008, respectively. While supra-glacier lakes on the debris-terminus of the Rongbuk Glacier were enlarged dramatically at the same time, from 0.05 km^2 in 1974 increased to 0.71 km^2 in 2008, which was more than 13 times larger in the last 35 years. In addition, glacier changes also showed spatial differences, for example, glacier retreat rate was the fastest at glacier termini between 5400 and 5700 m a.s.l than at other elevations. The result also shows that glaciers in the middle Himalayas retreat almost at a same pace with those in the western Himalayas. 相似文献
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通过对甘肃临夏松鸣岩地区紫果云杉树轮宽度的分析, 发现研究区树轮标准宽度年表与降水、PDSI相关低, 而与当地3~10月平均最高温(3月至10月月平均最高温的算术平均值)相关最高(r=0.578, p<0.0001, n=62)。 在此基础上, 利用多元回归技术设计转换方程, 重建了研究区1818年以来3~10月平均最高温, 重建序列的方差解释量达40% (调整自由度后为38%)。重建序列中高温年与低温年的年份大致相当, 分别为14.9% 和12.9%; 重建时段可以分为4个温暖期(1818~1854年、1882~1900年、1937~1966年和2001~2012年)和3个寒冷期(1855~1881年、1901~1936年和1967~2000年), 可与秦岭西部的温度重建结果进行良好的对比; 研究区在20世纪后期(2001~2012年平均最高温比1970~1980年平均最高温)有明显的升温趋势, 上升0.77℃。空间分析表明, 临夏地区3~10月平均最高气温变化具有一定的空间代表性, 可以反映黄土高原西部地区气温的历史变化。功率谱分析(MTM)检测出该重建序列在过去195年中存在42.74a, 7.79~3.18a和2.77a的准周期震荡, 可能与PDO和ENSO大尺度海洋耦合作用有关。 相似文献
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Qiufang Shao Yue Shi Zhiying Xiang Huaiyong Shao Wei Xian Peihao Peng Chengying Li Qiurong Li 《Journal of the Indian Society of Remote Sensing》2018,46(4):569-580
Located on the southeast edge of the Qinghai-Tibetan plateau, Aba County is the core area of the Returning Grazing Land to Grassland Project (RGLGP) on the plateau. For the purpose of monitoring the grassland change before and after the grassland protection project in Aba County, Landsat images acquired in 1996, 2003 and 2009 were analyzed. Using Spectral Mixture Analysis (SMA) model, sub-pixel fractions of land cover components were obtained: bright vegetation (BV), dark vegetation (DV), bright soil (BS), dark soil (DS) and water. Fraction images present the distribution and proportions of typical land cover components in this study. Fractions BV and BS were chosen as two indicators for grassland degradation. Thereafter, Change Vector Analysis (CVA) model was applied on the two indicators. After the performance of the CVA model, change results which consisted of both grassland degradation and vegetation re-growth were obtained, showing the change patterns of grassland degradation and vegetation re-growing in Aba County between two gaps: from 1996 to 2003 (before the RGLGP) and from 2003 to 2009 (after the RGLGP). The change patterns of grassland degradation and vegetation re-growing can effectively assist in the development of environmental restoration measures and in the RGLGP plans for the Qinghai-Tibetan plateau. 相似文献
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开展森林小气候研究,对于协调生物与环境的关系、保护生物多样性以及实现森林的可持续高效管理,都是十分重要的。选择5月和10月典型的晴朗无风天气条件,以侧柏纯林为对照,研究了郁闭度为0.25、0.54和0.87的侧柏-山毛桃群落演替初期小气候特征。结果表明,侧柏-山毛桃混交林对春季和秋季林内空气温度的早间增温效应和午间降温效应,随着郁闭度增加而增大。春季的高温峰值出现在15时,晚于秋季的高温峰值13时。春季和秋季林内10 cm处地温日间呈持续增加趋势,春季以郁闭度为0.25的B点为最高,秋季侧柏纯林在12时前为最低,14时后为最高。春季林内空气相对湿度从07时到11时呈快速降低的趋势,然后逐渐缓慢回升;而秋季林内的相对湿度,随着郁闭度的增加而增大,但日间变化幅度比较小。无论春季还是秋季,侧柏和山毛桃的叶片温度日间变化均呈先升高后缓慢降低的趋势。春季郁闭度对侧柏和山毛桃的叶片温度影响不显著,但秋季11-15时,随着郁闭度的增加,叶片温度有降低的趋势。在太行山区,以山毛桃为保护树种,快速提高侧柏-山毛桃混交林的郁闭度,对有效地改善林内小气候,促进森林更新和管理都是十分重要的。 相似文献
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From stable carbon isotope analysis of tree-rings of Chinese pine (Pinus tabulaeformis) from Mt. Helan, China, we found that high-δ13C values were related to high mean temperatures from June to August (T
68), and Iow-δ13C values corresponded to low T
68. From these data, a transfer function has been used to reconstruct summer temperatures (T
68) for the Mt. Helan region. The explained variance of reconstruction is 34.9% (F=15.01, p<0.001). The time period containing the highest summer temperatures in northern China (late 1920-1930s) was confirmed by our
reconstruction. The data indicate that there is a tele-connection between summer temperatures in Mt. Helan area and sea-surface-temperatures
in the tropical Pacific. The extreme low temperature periods around the years of 1920 and 1947 for Mt. Helan region correspond
well to the cold climate in the tropical Pacific. Along with other analyses, this suggests that climate variations in the
Mt. Helan region are driven not only by local events, but also by the global climate. Significant periodicities appearing
in the reconstruction are 2.56 and 2.63 years. 相似文献
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一次强降水天气过程的中尺度分析 总被引:4,自引:0,他引:4
利用每小时增强显示红外云图,云顶黑体温度(TBB)和常规气象资料,分析了1993年8月3-6日华北原及西北地区东部一次暴雨-大暴雨过程,揭示了产生大暴雨的中α尺度过流系统的发生发展,讨论了环境场条件及天气尺度系统间的相互作用对暴雨云团的重要性,并用物理量诊断探讨雨团形的物理机制。 相似文献
30.
通过对秦岭东端华山地区油松树木年轮宽度序列的分析研究,探讨了华山地区油松对气候环境响应的敏感性,结果表明在华山地区油松对气温和降水的响应均高于华山松,与 5~6月平均温度相关较高,且通过了0.01显著性信度检验。在此基础上,我们重建了华山地区 1558~2006年间 5~6月的平均温度,重建序列的方差解释量达到41%。结果显示: 华山过去449年中,大部分年份 5~6月平均温度在平均值附近波动,变幅不大; 重建序列可与秦岭南五台 5~7月温度序列进行良好对比,其年际间相关系数达到了0.49(N=246, p<0.0001)。华山地区20世纪 20~30年代初的暖期略偏低; 20世纪30年代中期至50年代是整个重建时段中低温持续时间较长的时段; 20世纪60年代之后,气温波动平缓; 从20世纪70年代开始快速升温,对全球变暖有较强响应。 相似文献