青海高寒草甸退化演替中的植被指数   总被引：2，自引：0，他引：2  

邢学刚  颜长珍  逯军峰  翟晓慧  贾浩巍  谢家丽 《中国沙漠》2021,41(3):203-213

随着气候变化和人为活动干扰,高寒草甸退化已成为青藏高原严重的生态环境问题,精准识别其退化程度并制定相应恢复策略,对实现高寒草甸可持续发展具有重要意义。目前,低空间分辨率MODIS数据为草地遥感监测的主要数据源,但难以满足景观破碎度或异质性较强地区的应用。本研究基于野外调查资料,利用多源遥感数据（MODIS、Landsat、Sentinel-2）研究不同空间分辨率归一化植被指数（NDVI）对高寒草甸退化演替的响应,为准确评估青藏高原高寒草甸退化程度提供依据。结果表明：（1）随着高寒草甸退化,植被群落优势种演化趋势为禾草—矮嵩草—小嵩草—杂草群落;植被高度和生物量先快速下降,然后缓慢下降或趋于稳定,植被覆盖度和NDVI的变化呈相反特征。（2）随着湿地草甸旱化,植被群落优势种从藏嵩草演变为矮嵩草或小嵩草,湿地旱化初期植被高度、生物量和覆盖度平均值略低于原生湿地,NDVI略大于原生湿地,差异不显著。（3）植被高度、覆盖度和生物量与Sentinel-2或Landsat的NDVI相关性均优于MODIS,说明Sentinel-2和Landsat的NDVI对高寒草甸退化演替过程更加敏感,采用该数据能更准确评估高寒草甸退化程度。  相似文献   

新陈代谢GM(1,1)模型在建筑物沉降预测中的应用研究     

翟信德  高飞  徐文兵 《现代测绘》2008,31(1):13-15

本文针对传统GM(1,1)模型存在的不足,建立了新陈代谢GM(1,1)沉降预测模型.并以某建筑物沉降为例对比两模型的预测值,结果表明新陈代谢GM(1,1)模型在处理该类数据上更加具有一定的优势.  相似文献   

杭州地区大范围暴雨、局地暴雨和强对流的特征分析     

翟国庆 《大气科学》1987,11(2):202-208

本文根据杭州地区60个暴雨和强对流例子.通过对大范围暴雨、局地暴雨和强对流的对比分析,得到:风的垂直切变尤其是在边界层具有一定强度;三者湿度条件有一定差别,但差别比华北要小;强对流的不稳定度大于暴雨,而大范围暴雨与局地暴雨差别则不明显.  相似文献   

论孔兹岩——地球上特殊地质过程的记录     

翟明国 《地质学报》2022,96(9):2967-2997

近些年来，孔兹岩成为前寒武纪地质、变质地质以及大陆演化研究中一个使用非常普遍的词。在不少的文章中，孔兹岩被赋予特定的地质含义。例如，在变质作用中联系到高温- 高压麻粒岩相或者是高温—超高温变质作用；在地质历史中，代表元古宙的特定时期；在构造环境中联想到古老大陆边界或者克拉通盖层，等等。这些说明孔兹岩类岩石的研究具有重要的意义。经过仔细分析，还可看到不同的研究者对于孔兹岩的定义、岩石组合和出露规律、变质环境和变质历史、构造指示意义诸方面的理解都存在很大的差异，甚至有时各说各话，不利于交流或产生歧义和误解。因此，有必要对孔兹岩一词的定义以及它的使用做一个梳理和界定，对其内涵、构造意义以及相关问题进行讨论。这就是本文的初衷。此外，本文还认为，华北的古元古代孔兹岩类的原岩是与其他沉积岩共生的富铝沉积岩，由于它们经历了高级变质作用，因此有相当比例的沉积岩变成原地- 准原地重熔的花岗岩，并与变质的基性岩墙或岩体密切共生。含孔兹岩的沉积岩系具有沉积环境稳定的特点，不含或罕见火山岩层，是在新太古代克拉通化和古元古代 “静寂期”之后的代表性裂谷型沉积组合。“静寂期”超过200 Ma，使得古老的陆壳有长期和充裕的风化时间，沉积物具有充分的搬运和分选特点，伴有厚层碳酸盐沉积，并以含有较普遍或较频繁出现的碳质黑色页岩夹层而与太古宙的沉积岩石相区别。华北的孔兹岩类的分布以及特点，具有全球可比性，对于理解可能的休伦裂谷事件和相伴随的大氧化事件具有举足轻重的意义；同时对于理解古元古代末期成山纪（Orosirian）的构造事件以及构造体制的重要转变也有不可替代的作用。孔兹岩是地球特殊地质过程的记录。  相似文献   

基于土壤理化性质估计土壤水分特征曲线Van Genuchten模型参数   总被引：2，自引：1，他引：1  

李爽  赵相杰  谢云  翟俊瑞  刘刚  高晓飞  李晶  高燕 《地理科学》2018,38(7):1189-1197

在东北黑土区采集了不同侵蚀强度黑土土样,测定其土壤水分、机械组成、有机质和容重等指标,利用Rosetta模型估计了Van Genuchten模型的参数,并将估算土壤水分与实测土壤水分对比,评价了选择不同土壤理化性质指标的模拟精度,及该方法对东北黑土的适宜性。结果表明：选择4个或6个土壤性质指标,尺度参数（α）和形状参数（n）的差异较大,采用6指标时,α增大,n减小。修正VG模型参数m与n的关系后,模型拟合精度明显提高,其中6指标的计算结果好于4指标,但拟合值偏大,需进一步较正。Rosetta模型适用于砂粒含量小于46%,粘粒含量大于28%的东北黑土。  相似文献   

Tracking a Severe Pollution Event in Beijing in December 2016 with the GRAPES–CUACE Adjoint Model     

Chao?Wang  Xingqin?AnEmail author  Shixian?Zhai  Zhaobin?Sun 《Acta Meteorologica Sinica》2018,32(1):49-59

We traced the adjoint sensitivity of a severe pollution event in December 2016 in Beijing using the adjoint model of the GRAPES–CUACE (Global/Regional Assimilation and Prediction System coupled with the China Meteorological Administration Unified Atmospheric Chemistry Environmental Forecasting System). The key emission sources and periods affecting this severe pollution event are analyzed. For comaprison, we define 2000 Beijing Time 3 December 2016 as the objective time when PM_2.5 reached the maximum concentration in Beijing. It is found that the local hourly sensitivity coefficient amounts to a peak of 9.31 μg m^–3 just 1 h before the objective time, suggesting that PM_2.5 concentration responds rapidly to local emissions. The accumulated sensitivity coefficient in Beijing is large during the 20-h period prior to the objective time, showing that local emissions are the most important in this period. The accumulated contribution rates of emissions from Beijing, Tianjin, Hebei, and Shanxi are 34.2%, 3.0%, 49.4%, and 13.4%, respectively, in the 72-h period before the objective time. The evolution of hourly sensitivity coefficient shows that the main contribution from the Tianjin source occurs 1–26 h before the objective time and its peak hourly contribution is 0.59 μg m^–3 at 4 h before the objective time. The main contributions of the Hebei and Shanxi emission sources occur 1–54 and 14–53 h, respectively, before the objective time and their hourly sensitivity coefficients both show periodic fluctuations. The Hebei source shows three sensitivity coefficient peaks of 3.45, 4.27, and 0.71 μg m^–3 at 4, 16, and 38 h before the objective time, respectively. The sensitivity coefficient of the Shanxi source peaks twice, with values of 1.41 and 0.64 μg m^–3 at 24 and 45 h before the objective time, respectively. Overall, the adjoint model is effective in tracking the crucial sources and key periods of emissions for the severe pollution event.  相似文献   

Changes in Extreme Maximum Temperature Events and Population Exposure in China under Global Warming Scenarios of 1.5 and 2.0°C: Analysis Using the Regional Climate Model COSMO-CLM     

Mingjin?Zhan  Xiucang?Li  Hemin?Sun  Jianqing?Zhai  Tong?Jiang  Yanjun?WangEmail author 《Acta Meteorologica Sinica》2018,32(1):99-112

We used daily maximum temperature data (1986–2100) from the COSMO-CLM (COnsortium for Small-scale MOdeling in CLimate Mode) regional climate model and the population statistics for China in 2010 to determine the frequency, intensity, coverage, and population exposure of extreme maximum temperature events (EMTEs) with the intensity–area–duration method. Between 1986 and 2005 (reference period), the frequency, intensity, and coverage of EMTEs are 1330–1680 times yr^–1, 31.4–33.3°C, and 1.76–3.88 million km², respectively. The center of the most severe EMTEs is located in central China and 179.5–392.8 million people are exposed to EMTEs annually. Relative to 1986–2005, the frequency, intensity, and coverage of EMTEs increase by 1.13–6.84, 0.32–1.50, and 15.98%–30.68%, respectively, under 1.5°C warming; under 2.0°C warming, the increases are 1.73–12.48, 0.64–2.76, and 31.96%–50.00%, respectively. It is possible that both the intensity and coverage of future EMTEs could exceed the most severe EMTEs currently observed. Two new centers of EMTEs are projected to develop under 1.5°C warming, one in North China and the other in Southwest China. Under 2.0°C warming, a fourth EMTE center is projected to develop in Northwest China. Under 1.5 and 2.0°C warming, population exposure is projected to increase by 23.2%–39.2% and 26.6%–48%, respectively. From a regional perspective, population exposure is expected to increase most rapidly in Southwest China. A greater proportion of the population in North, Northeast, and Northwest China will be exposed to EMTEs under 2.0°C warming. The results show that a warming world will lead to increases in the intensity, frequency, and coverage of EMTEs. Warming of 2.0°C will lead to both more severe EMTEs and the exposure of more people to EMTEs. Given the probability of the increased occurrence of more severe EMTEs than in the past, it is vitally important to China that the global temperature increase is limited within 1.5°C.  相似文献   

First observation of domoic acid and its isomers in shellfish samples from Shandong Province,China     

Zheng  Guanchao  Wu  Haiyan  Guo  Mengmeng  Peng  Jixing  Zhai  Yuxiu  Tan  Zhijun 《中国海洋湖沼学报》2022,40(6):2231-2241

Journal of Oceanology and Limnology - A total of 133 shellfish samples were collected in seven cities of Shandong Province, China, from May to October, 2019. The domoic acid (DA) concentrations...  相似文献   

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一次飑线大风天气过程成因分析   总被引：1，自引：0，他引：1  

陈伟斌  陈见  赵金彪  翟丽萍 《气象研究与应用》2015,36(1)

利用常规气象资料、自动站资料、多普勒雷达资料及NCEP再分析资料,分析了2014年3月31日广西大风天气过程的环境背景场、层结结构、垂直风切变场、局地层结特征、物理量配置、雷达回波及地面风场特征,得到一些有意义的结论,可以为此类天气过程预报提供参考。  相似文献