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探讨和总结了古雷电研究的4种方法:①地质记录中的古气候标志方法;②氧同位素测量古温度方法;③冰川冰期与气候冷暖方法;④史料记载的研究方法。应用这4种方法分别对史前气候变迁下的古雷电进行描述,然后再从史料记载中,浓缩了古雷电的记录,分析了古雷电印象。 相似文献
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卫星云图定量处理辅助系统原理和应用 总被引：6，自引：0，他引：6
通过云体强度描述和参数计算方法的介绍 ,阐明了这些方法的天气学意义 ,给出了常见云系的数学模型建模方法和一般数学表达式 ,提出了处理系统的应用范围和前景。 相似文献
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根据递阶辨识原理,研究了类多变量方程误差系统和类多变量方程误差ARMA系统递阶随机梯度方法和递阶梯度迭代方法、递阶最小二乘方法和递阶最小二乘迭代方法.进一步利用多新息辨识理论,推导了递阶多新息梯度辨识方法和递阶多新息最小二乘辨识方法.为减小计算量,推导了基于滤波的类多变量方程误差ARMA系统递阶辨识方法和递阶多新息辨识方法.讨论了几个典型辨识算法的计算量,并给出了计算参数估计的步骤. 相似文献
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用遥感技术进行土壤水分监测已有30多年的历史,国内外学者在此领域做了不少的探索和研究。通过分析各种遥感土壤水分监测方法的特点,将其归纳为：基于土壤热惯量的方法、基于植被指数的方法、基于温度和植被指数的方法、基于植被蒸散的方法,以及基于微波遥感的方法等五类,分别介绍了各类土壤水分监测方法的提出及其发展、演变,同时也提出了土壤水分遥感监测在实际运用中仍然存在的问题。 相似文献
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综合分析国内外风速预报相关文献,从物理方法、统计与机器学习方法、组合方法3个方面对超短期风速预报方法的研究现状进行归纳总结,对比了主要预报方法的优缺点,给出了不确定分析和误差评价指标,探讨了在超短期风速预报研究中应重点解决的问题和发展方向。 相似文献
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Fuhai Geng Changjie Cai Xuexi Tie Qiong Yu Junlin An Li Peng GuangQiang Zhou Jianming Xu 《Journal of Atmospheric Chemistry》2009,62(3):229-247
Qualification of the sources of volatile organic compounds (VOCs) and their effects on city air pollution are crucial issues
to develop an effective air pollution control strategy in many polluted large cities of China. In this study, the VOC concentrations
measured in Shanghai, China from 2006 to 2008 are analyzed. A receptor model (PCA/APCS; Principal Component Analysis/Absolute
Principal Component Scores) is applied for identifying the contributions of individual VOC sources to VOC concentrations.
Using the PCA/APCS technique, five and four surrogated VOC sources are classified in the center of Shanghai city in summer
and in winter. In summer, the five VOC sources include PCs1 (liquefied petroleum gas/natural gas leakage and gasoline evaporation),
PCs2 (vehicle related emissions), PCs3 (solvent usages), PCs4 (industrial productions), and PCs5 (biomass/biofuel/coal burning
and other natural sources). In winter, the four VOC sources include PCw1 (liquefied petroleum gas/natural gas leakage and
gasoline evaporation), PCw2 (solvent usages and industrial productions), PCw3 (vehicle related emissions), and PCw4 (biomass/biofuel/coal
burning). The result suggests that during summer, 24, 28, 17, 18, and 13% of the measured VOC concentrations were estimated
due to the PCs1, PCs2, PCs3, PCs4, and PCs5 VOC sources, respectively. During winter, 17, 48, 23, and 12% of the measured
VOC concentrations were attributed to the PCw1, PCw2, PCw3, and PCw4 VOC sources, respectively. For aromatic concentrations,
35% of the concentrations were resulted from solvent usage (PCs3), following by industrial productions (PCs4) of 27%, and
vehicle emissions (PCs2) of 19%. For alkene concentrations, the two largest contributors were due to gasoline industrial and
vehicle emissions in both summer and winter. For alkane concentrations, the largest sources were due to gasoline industrial
emissions (PCs1) and vehicle emissions (PCs2) in summer. In winter, vehicle emissions (PCw3), solvent usages/industrial productions
(PCw2), and gasoline industrial emissions (PCw1) were the major sources. For halo-hydrocarbon concentrations, biomass/biofuel/coal
burning and other natural sources were the major sources in both summer and winter. 相似文献
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B. Pohl N. Fauchereau Y. Richard M. Rouault C. J. C. Reason 《Climate Dynamics》2009,33(7-8):1033-1050
After removing the annual cycle, a principal component analysis is applied to the daily outgoing longwave radiation anomaly field, used here as a proxy for atmospheric convection. The analysis is carried out over the southern African region (7.5°E–70°E, 10°S–40°S) for austral summer (November through February) for the period 1979–1980 to 2006–2007. The first five principal components (PC) are retained. The first two PCs describe spatial patterns oriented north-west to south-east from tropical southern Africa (SA) to the mid-latitudes. They are interpreted to be different possible locations for synoptic-scale tropical–temperate troughs (TTT), one dominant rainfall-producing synoptic system in the region. The phase relationship between these two PCs describes a tendency for these TTT to propagate eastwards from SA to the Mozambique Channel and southern Madagascar. The next three PCs describe convective fluctuations, respectively, located over the north-west, the south and the centre of SA. Their time series are significantly associated with Madden–Julian oscillation (MJO) activity in the tropics. However, we find that TTT systems are statistically independent of the MJO, i.e. they are equally liable to occur during any phase of the MJO. Three PCs out of five also show a significant association with El Niño southern oscillation, confirming that El Niño years mostly coincide with suppressed convection at the intraseasonal time-scales, a result consistent with its impact on seasonal averages diagnosed in previous studies. 相似文献
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Long-Term Trend of Temperature Derived by Statistical Downscaling Based on EOF Analysis 总被引：1，自引：0，他引：1 
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下载免费PDF全文 This study analyzes the ability of statistical downscaling models in simulating the long-term trend of temperature and associated
causes at 48 stations in northern China in January and July 1961–2006. The statistical downscaling models are established
through multiple stepwise regressions of predictor principal components (PCs). The predictors in this study include temperature
at 850 hPa (T850), and the combination of geopotential height and temperature at 850 hPa (H850+T850). For the combined predictors,
Empirical Orthogonal Function (EOF) analysis of the two combined fields is conducted. The modeling results from HadCM3 and
ECHAM5 under 20C3M and SERS A1B scenarios are applied to the statistical downscaling models to construct local present and
future climate change scenarios for each station, during which the projected EOF analysis and the common EOF analysis are
utilized to derive EOFs and PCs from the two general circulation models (GCMs). The results show that (1) the trend of temperature
in July is associated with the first EOF pattern of the two combined fields, not with the EOF pattern of the regional warming;
(2) although HadCM3 and ECHAM5 have simulated a false long-term trend of temperature, the statistical downscaling method is
able to well reproduce a correct long-term trend of temperature in northern China due to the successful simulation of the
trend of main PCs of the GCM predictors; (3) when the two-field combination and the projected EOF analysis are used, temperature
change scenarios have a similar seasonal variation to the observed one; and (4) compared with the results of the common EOF
analysis, those of the projected EOF analysis have been much more strongly determined by the observed large-scale atmospheric
circulation patterns. 相似文献
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Summary Daily precipitation affinity areas are established for Wales by means of S-mode Principal Components Analysis (PCA) and Cluster Analysis, using data for the autumn-winter (September-January) period, 1982–87, subset according to surface wind direction. Relatively strong PCA simple structures were found for five wind directions clockwise from south to north, using the OBLIMIN rotation for the first four (south to northwest) and the VARIMAX rotation for the last (north). Whilst interpretation of many of the most significant Prinicipal Components (PCs) was difficult in strictly meteorological or climatological terms, the precipitation areas produced by clustering based on the most important PCs, yielded a continuum of change in areal organisation with progressively changing wind direction. Only the far southwest and northwest of the country appear in every area map, although superficially, northeastern, English border and southeastern areas were present on most. The derived areas bear only small overall resemblance to currently used forecasting areas.With 9 Figures 相似文献
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Wintertime variability of Mediterranean precipitation and its links with large-scale circulation anomalies 总被引：1，自引：0，他引：1
A standard principal component analysis has been performed over the Mediterranean and over the larger European region on monthly precipitation anomalies for the winters between 1979 and 1995. The main centres of action of the associated EOFs are very similar for the two regions and the two sets of PCs are highly correlated with each other. Focusing on the Mediterranean region, the same analysis has been performed using 500?hPa geopotential height monthly anomalies taken from the operational NCEP analysis. Comparing the two sets of PCs associated with upper-air and surface data, a strong correlation has been found suggesting the presence of a two-way link between regional precipitation patterns and large-scale circulation anomalies. For both fields, the largest fraction of variance is explained by the North Atlantic Oscillation, while smaller but still substantial fractions are explained by other known patterns of large-scale variability such as the Eastern Atlantic pattern and the Euro-Atlantic blocking. No detectable connection has been found between Mediterranean precipitation patterns and El Niño SST anomalies during winter. With respect to temporal variability, significant trends have been found over most European areas during the winters considered. The associated pattern is characterised by a substantial increase of precipitation over western Scandinavia and a general decrease over southern Europe. This result is confirmed by analysing data from stations located in northern Italy. 相似文献
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Daily precipitation totals at 55 sites were used to investigate geographic variability in winter (DJF) rainfall over Cumbria, NW England, over an 11-year period. Winter is the wettest season (>800?mm in the mountainous Lake District), with rainfall mechanisms closely linked to North Atlantic forcing. The Lamb weather type catalogue was used to identify rainfall distributions under different wind directions. Precipitation magnitude over Cumbria is much more sensitive to a change in wind direction than the geographic pattern in rainfall, with southwesterly (easterly) winds producing the highest (lowest) spatially averaged daily rainfall totals of 8.2?mm (0.6?mm). S-mode principal components analysis was used to identify the main patterns of precipitation variability. Three principal components (PCs) were retained as being statistically significant (cumulative explained variance for unrotated PCs?=?84.3%), with a correlated PC structure (direct oblimin rotation) best describing the spatial variance in rainfall. PC 1 has a very high index of strength (variance measure?=?40.9), indicating that there is one dominant rainfall pattern. PC 1 shows a gradient between wetter conditions in southwest Cumbria and over the central Lake District and drier conditions in NE Cumbria, and is usually caused by active zonal west to southwest flows. Almost of equal importance to PC 1 is PC 3 (variance measure?=?39.3), which has a more uniform rainfall distribution than PC 1 and is usually caused by fronts stalling over the region. PC 2, which shows an east to west decline in rainfall totals, is much less important than PCs 1 and 3 (variance measure?=?18.6). PC 2??s rainfall pattern can be caused by easterly flows with high pressure over Scandinavia and low pressure over the Continent, or by strong southwesterly flows, with depressions often centred over Scotland. Finally, cluster analysis was carried out to identify precipitation regions for all days and for each wind direction. Clusters were found to be largely stable to changes in wind direction, with stations in the central Lake District often clustered together, thus highlighting the importance of orographic enhancement of rainfall in this region. 相似文献
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降水作为全球水循环的重要组成,与人们的生产生活密切相关.有效的降水预测对于防灾减灾,以及经济的可持续发展至关重要.然而,由于影响降水过程的复杂性,当前降水预测还存在诸多挑战.针对我国东部夏季降水,我们提出年际增量结合经验正交分解的新统计预测方法.首先计算降水年际增量的主模态,然后针对主模态时间序列构建预测模型,用预测的... 相似文献
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FAN Li-Jun 《大气和海洋科学快报》2009,2(4):208-213
Monthly mean temperatures at 562 stations in China are estimated using a statistical downscaling technique. The technique used is multiple linear regressions （MLRs） of principal components （PCs）. A stepwise screening procedure is used for selecting the skilful PCs as predictors used in the regression equation. The predictors include temperature at 850 hPa （7）, the combination of sea-level pressure and temperature at 850 hPa （P＋T） and the combination of geo-potential height and temperature at 850 hPa （H＋T）. The downscaling procedure is tested with the three predictors over three predictor domains. The optimum statistical model is obtained for each station and month by finding the predictor and predictor domain corresponding to the highest correlation. Finally, the optimum statistical downscaling models are applied to the Hadley Centre Coupled Model, version 3 （HadCM3） outputs under the Special Report on Emission Scenarios （SRES） A2 and B2 scenarios to construct local future temperature change scenarios for each station and month, The results show that （1） statistical downscaling produces less warming than the HadCM3 output itself; （2） the downscaled annual cycles of temperature differ from the HadCM3 output, but are similar to the observation; （3） the downscaled temperature scenarios show more warming in the north than in the south; （4） the downscaled temperature scenarios vary with emission scenarios, and the A2 scenario produces more warming than the B2, especially in the north of China. 相似文献