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1.
气温是气象要素的重要组成部分,广泛用于全球气候变化、资源环境分析及灾害预警等多个领域.随着卫星遥感技术的发展,气温的估算趋向于遥感或遥感和GIS结合的方法.本文以浙江省为研究区域,利用了36个站点2013年逐日每10min一次的自动气象站气温观测数据和MODIS地表温度及其他参数产品,选用多元线性回归(自变量为地表温度、归一化植被指数、地表反照率、经度、纬度和高程)、温度植被指数以及多元线性回归插值方法进行气温估算,建立了研究区日最高气温最低气温估算模型,并比较了几种气温估算方法在研究区的适用性.结果表明:3种方法最高气温估算的决定系数(R~2)分别为0.96、0.91、0.97,均方根误差(R_(MSE))分别为1.84、2.75、1.49℃;多元线性回归和多元线性回归插值法最低气温估算的R~2分别为0.87、0.91,R_(MSE)分别为3.33、2.93℃,两者均为多元线性回归插值法得到的结果最好.空间分布结果显示,多元线性回归插值法能很好地反映由地形不同所带来的细节差异. 相似文献
2.
湖北省最高气温和最低气温的非对称变化 总被引:3,自引:1,他引:3
研究了湖北省1961~1995年,季,月时间尺度平均最高气温,最低气温和气温日较差的气候倾向率时空差异,结果表明,在年平均情况下,湖北省大部分地区最高气温有弱降温趋势,最低气温有明显增加趋势,气温日较差有显著减小趋势,还分析了气温日较差减小的三种类型,并指出最高,最低气温的变化趋势与日照百分率及大气相对湿度的变化趋势有关。 相似文献
3.
植被覆盖及其动态变化可以有效地反映出区域环境变化特征,监测植被变化在评价区域生态环境质量中是不可缺少的一部分。数据源采用Landsat遥感影像,在运用归一化植被指数及像元二分模型的基础上,提取出2002、2009、2018年珲春老龙口水库地表水源地植被覆盖度,并进行动态变化分析。结果表明:2002—2018年珲春老龙口水库地表水源地区平均植被覆盖度值呈先减少后增加的趋势,2009—2018年,该研究区植被覆盖度处于相对良好的状态,中高度植被覆盖区与高度植被覆盖区占总面积的比重达到86.99%。从空间上来看,地表水源地的东北部分植被覆盖度较高,由东向西呈降低趋势。高植被覆盖区变化明显,近20年内增加了1 818.80 km~2。政府政策、生态恢复工程、人类活动等是影响珲春老龙口水库地表水源地植被覆盖度的主要因素。 相似文献
4.
卫星遥感是监测大范围植被动态变化最有效的手段。随着中国遥感技术的发展,国产风云卫星也逐渐应用于植被变化研究,但有关国产风云卫星刻画植被动态变化表现方面仍不明晰。比较了国产风云卫星(FY-3C VIRR)和美国Terra卫星(MODIS)的归一化植被指数(normalized difference vegetation index, NDVI)产品在湖南省和江西省的时空一致性。结果表明:(1)两种卫星NDVI产品的空间分布与年、季、月的变化特征在湘赣地区有较好的一致性,江西省NDVI整体高于湖南省;(2)FY-3C和MODIS年均NDVI都呈现出2018年高于2017年和2019年的情况,基于MODIS的湘赣地区三年的年均NDVI(0.58)高出FY-3C(0.36)约60%;(3)FY-3C NDVI在各季节都整体低于MODIS NDVI,其中冬季差异最大,基于MODIS NDVI均值(0.42)约是FY-3C(0.21)的2倍,其余季节MODIS高出FY-3C约50%;(4)FY-3C NDVI与MODIS NDVI月变化趋势基本一致,二者年最大NDVI差异变化不大且较为稳定,年最小... 相似文献
5.
Reconstructing mean maximum temperatures of May-August from tree-ring maximum density in North Da Hinggan Mountains, China 总被引:2,自引:0,他引:2
Tree-ring samples from Dahurian Larch (Larix gmelinii (Rupr.) Rupr.) were collected at three sites in the northern Da Hinggan Mountains. Using samples measured by X-ray densitometry, measurements of tree-ring maximum latewood density chronologies of two sites were found to be significantly correlated with summer temperature. These two sites’ tree-ring series were combined to form a single standard regional chronology. This was used to reconstruct the May-August monthly mean maximum temperature for the period 1855-2008 AD, and it explained 39.5% of the total temperature variance. In the past 154 years, there were 4 cold periods (1874-1893, 1927-1948, 1951-1960 and 1992-2002) and 4 warm periods (1855-1873, 1894-1916, 1961-1991 and 2003-2008). The summer temperature rose more obviously than that of winter in this region. Having been validated by other temperature reconstructions from the surrounding area, the reconstruction could indicate the summer temperature changes of large-scale regions. 相似文献
6.
最值定理是高等数学的重要定理之一,为物理、化学、生物、工程、经济管理和社会等领域的最优化问题奠定了理论基础。由于最值定理具有高度的抽象性,学生很难深刻理解,这对后继课程的学习和将来的研究非常不利。为了帮助学生理解最值定理,借助函数的图像直观感知最值定理;通过最值定理的理论证明完成感性认识到理性认识的升华;利用最值定理中的辩证法思想,培养学生的辩证唯物主义的思维方式。 相似文献
7.
GONGDaoyi WANGShaowu ZHUJinhong 《科学通报(英文版)》2004,49(6):637-642
The relationship between the Arctic Oscillation (AO) and daily temperature variance of 150 Chinese stations are investigated in the present study for wintertime (1 November through 31 March) in the period of 1954--2001. Resuits show that the temperature variance significantly decreases during the high AO years,and increases in low AO cases. A key factor connecting them is the Siberian High,particularly the high-frequency fluctuations of the High.Within the seasonal time scale, the frequency of low-temperature extremes (daily temperature anomaly below-2σ,σ is the standard deviation of daily temperature for a given winter and a given station) displays an odd relation to the variance: a larger (smaller) variance is found to be associated with smaller (greater) frequency of low-temperature events. That is due to the non-normal distribution of the temperatures, and also influenced by the phases of AO. During the last 50 years or so, AO experiences a significant increasing trend, meanwhile the variance of daily sea level pressure (SLP) in the central region of Siberian High has decreased at a rate of-10.7%/10 a. These result in a significant weakening of the daily temperature variance in China with a trend of -4.1%/10 a, and a significant increase in the intra-seasonal low-temperature extremes at a rate of 0.16d/10 a. 相似文献
8.
江河源区近40年来气温变化特征的研究 总被引:2,自引:0,他引:2
通过对长江、黄河源区从1961—2001年的年平均气温、日最高气温、日最低气温随时间变化规律的分析得出:江河源区近40年来年平均气温、日最高气温、口最低气温随时间均呈增温态势;日最低气温的增温比日最高气温的增温更显著:20世纪90年代以米气温明显偏高;但也有新的特点:一月份日最高气温、日最低气温和日平均气温进人90年代不但没有变暖反而足降低的;80年代后期年平均气温、日最高气温、日最低气温发生了显著的变暖突变。 相似文献
9.
Methane (CH4) is the most important greenhouse gas and reactive trace gas in the atmosphere. Recently, it has been reported that terrestrial
plants can emit CH4 under aerobic conditions, which may call for reevaluation of the inventory of CH4 emissions in China. In this paper, those emissions over China and their effects on CH4 concentrations in lower troposphere were investigated. Firstly, based on the work of Keppler et al., the aerobic plant CH4 emission model (PLANTCH4) for China was established. And by using the database of normalized difference vegetation index
(NDVI) derived from NOAA/AVHRR, the distribution of net primary productivity (NPP) over China was simulated, and thereby,
for the first time, the amount and distribution of the newly identified source in China were estimated. Secondly, with the
aid of the three-dimensional atmospheric chemistry model system (MM5-CALGRID), the effects of the emissions were studied.
The results show that the annual aerobic plant CH4 emissions over China amount to 11.83 Tg, i.e. nearly 24% of Chinese total
CH4 emissions. And the major fraction (about 43%) comes from forests. When those emissions are considered in modeling, computed
countrywide mean surface concentration of CH4 is 29.9% higher than without them, with a maximum increase of 69.61 μg·m−3 in the south of Yunnan Province. In conclusion, to study CH4 emissions from terrestrial plants over China may have important implications for correctly estimating the contribution of
China to global CH4 budget, and may call for a reconsideration of the role of CH4 in global and regional environment and climate change.
Supported by National High-Tech Research & Development Program of China (Grant No. 2006AA06A307), National Basic Research
Program of China (Grant Nos. 2006CB403706 and 2006CB403703), and the Program for New Century Excellent Talents in University,
and Nanjing University Talent Development Foundation 相似文献
10.
根据1950~1999年的海温距平和中国夏季(6~8月)雨带分布类型资料,分析了各雨型与前期及同期热带太平洋和印度洋(21°S~21°N,29°E~81°W)海温异常的相关关系.分析表明,不同雨带类型和所对应同期及前期太平洋和印度洋海温有很好的相关关系. 相似文献