Comparison of multiple datasets with gridded precipitation observations over the Tibetan Plateau   总被引：2，自引：0，他引：2  

Qinglong You  Jinzhong Min  Wei Zhang  Nick Pepin  Shichang Kang 《Climate Dynamics》2015,44(3-4):791-806

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基于MODIS数据的水体识别指数方法的比较研究     

王净  李亚春  景元书 《气象科学》2009,29(3):342-347

从典型地物光谱曲线分析入手,MODIS数据的第7、2、1波段对植被、陆地、水体区分明显。本文对长三角太湖流域地区,采用MODIS数据以五种常水体识别进行水体信息提取,然后分别从目视解译效果、水体区分度的计算和提取的水体面积三方面来对这五种指数方法进行比较和评价。结果表明,在应用MODIS数据进行水体识别时,比值植被指数（RVI,Ratio Vegetation Index）和混和水体指数（CIWI,Combined Index of Normalized Difference Water Index）模型的目视解译效果较好,且CIWI指数具有水陆区分度较大和水体面积提取精度较高的优点。  相似文献   

Self-organization of planetary electromagnetic waves in the E-region of the ionosphere     

《Journal of Atmospheric and Solar》2003,65(6):661-671

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Potential climatic transitions with profound impact on Europe     

Anders Levermann  Jonathan L. Bamber  Sybren Drijfhout  Andrey Ganopolski  Winfried Haeberli  Neil R. P. Harris  Matthias Huss  Kirstin Krüger  Timothy M. Lenton  Ronald W. Lindsay  Dirk Notz  Peter Wadhams  Susanne Weber 《Climatic change》2012,110(3-4):845-878

We discuss potential transitions of six climatic subsystems with large-scale impact on Europe, sometimes denoted as tipping elements. These are the ice sheets on Greenland and West Antarctica, the Atlantic thermohaline circulation, Arctic sea ice, Alpine glaciers and northern hemisphere stratospheric ozone. Each system is represented by co-authors actively publishing in the corresponding field. For each subsystem we summarize the mechanism of a potential transition in a warmer climate along with its impact on Europe and assess the likelihood for such a transition based on published scientific literature. As a summary, the ‘tipping’ potential for each system is provided as a function of global mean temperature increase which required some subjective interpretation of scientific facts by the authors and should be considered as a snapshot of our current understanding.  相似文献   

1918—2010年天津降水指数变化特征   总被引：5，自引：0，他引：5       下载免费PDF全文

段丽瑶  刘爱霞  史珺 《气候变化研究进展》2012,8(3):171-177

利用天津1918—2010年逐日降水资料,分析了天津7个降水指数的长期变化趋势。结果发现:天津年降水量和降水日数年际差异较大,没有显著的趋势性变化。从1980年开始天津降水量和日数开始变小(少),方差也变小,四季中秋季降水量呈显著的增加趋势,夏季呈减少趋势,冬、春季变化较小。各极端降水指数中,均表现为线性趋势不明显,年际变化较大,20世纪90年代以来降水强度偏小,但呈缓慢的增加趋势,大雨日数也处于偏少阶段,大雨贡献率偏小,并呈减小趋势。四季中秋季连续5 d最大降水量呈显著的增加趋势,减少了秋季干旱的发生,最长连续无降水日数多发生在冬春季,近年来有增加的趋势。  相似文献   

热带气旋外围环流影响下深圳高温的定量估算     

张丽  申双和  孙向明 《气象》2010,36(4):37-42

利用NCEP再分析资料提供的风、湿度、垂直速度等资料及深圳地面观测数据,分析热带气旋外围环流造成深圳高温的原因。基于热力学能量方程,估算各因子的增温率和增温比例。结果表明:非绝热加热项是深圳高温的热量基础,增温比例为90.2%,平均增温率为0.83℃·h~(-1),假设8:00-14:00时增温率不变,计算出平均情况下,非绝热加热项使14时温度比08时增加5.0℃。其次湿度减小引起的增温、气流下沉增温、暖平流是深圳出现高温的重要因素,各自的增温比例分别为7.6%、3.8%、7.0%,总的增温率为0.17℃·h~(-1),计算出平均情况下,这3项可使14时温度比08时增加1.12℃。即热带气旋外围环流影响下,非绝热加热项对增温贡献最大,其中由于空气相对湿度小,定压比热减小,增温贡献较大;空气干绝热下沉增温使局地温度升高,但贡献较小;暖平流使局地温度的升高,贡献较大。  相似文献   

用于污水处理的人工湿地的基质、植物及其配置   总被引：18，自引：0，他引：18  

徐德福  李映雪 《湿地科学》2007,5(1):32-38

从工程角度探讨了人工湿地中基质与植物的筛选以及配置问题。基质是人工湿地不可缺少的组成部分,大部分物理、化学和生物反应等都在基质中进行。不同基质对污染物的净化能力存在明显差异,筛选对污染物净化能力强的当地材料作为人工湿地基质,不但能提高人工湿地的净化能力和使用寿命,还能减少人工湿地的投资成本。植物在人工湿地中有着重要的作用,包括直接吸收氮、磷和重金属等污染物质,提高人工湿地的渗透系数,增强根际微生物活性和输送氧气到根际增加根际的溶解性氧含量等,但不同植物对污染物的净化能力也存在很大差异,选用本地区净化力强的植物用于人工湿地,一方面可以提高人工湿地对污染物的去除效率,另一方面可以减少引用外来植物的投资成本,还可以避免引用外来植物造成的生物入侵危险。在筛选人工湿地基质和植物的基础上合理的配置基质和植物是提高人工湿地净化效率的重要保障。  相似文献   

The variation of ionospheric slab thickness over equatorial ionization area crest region     

《Journal of Atmospheric and Solar》2007,69(8):947-954

The GPS-derived total electron content (TEC) and NmF2 are measured at the Chung-Li ionosonde station (24.9°N, 121°E) in order to study the variations in slab thickness (τ) of the ionosphere at low-latitudes ionosphere during 1996–1999, corresponding to half of the 23rd solar cycle. This study presents the diurnal, seasonal, and solar flux variations in τ for different solar phases. The seasonal variations show that the average daily value is greater during summer and the reverse is true during equinox in the equatorial ionization anomaly (EIA) region. Moreover, the τ values are greater during the daytime (0800–1600 LT) and nighttime (2000–0400 LT) for summer and winter, respectively. The diurnal variation shows two abnormal peaks that appear during the pre-sunrise and post-sunset hours. The peak values decrease as the sunspot number increases particularly for the pre-sunrise peak. Furthermore, the variation in the F-peak height (hpF2) indicates that a thermospheric wind toward the equator leads to an increase in hpF2 and an enhancement in τ during the pre-sunrise period. Furthermore, the study shows the variations of τ values for different geophysical conditions such as the geomagnetic storm and earthquake. A comprehensive discussion about the relation between τ and the geophysical events is provided in the paper.  相似文献   

Investigation of Primary Factors Affecting the Variation of Modeled Oak Pollen Concentrations: A Case Study for Southeast Texas in 2010     

Wonbae Jeon  Yunsoo Choi  Anirban Roy  Shuai Pan  Daniel Price  Mi-Kyoung Hwang  Kyu Rang Kim  Inbo Oh 《Asia-Pacific Journal of Atmospheric Sciences》2018,54(1):33-41

Oak pollen concentrations over the Houston-Galveston-Brazoria (HGB) area in southeastern Texas were modeled and evaluated against in-situ data. We modified the Community Multi-scale Air Quality (CMAQ) model to include oak pollen emission, dispersion, and deposition. The Oak Pollen Emission Model (OPEM) calculated gridded oak pollen emissions, which are based on a parameterized equation considering a plant-specific factor (C _e ), surface characteristics, and meteorology. The simulation period was chosen to be February 21 to April 30 in the spring of 2010, when the observed monthly mean oak pollen concentrations were the highest in six years (2009-2014). The results indicated C _e and meteorology played an important role in the calculation of oak pollen emissions. While C _e was critical in determining the magnitude of oak pollen emissions, meteorology determined their variability. In particular, the contribution of the meteorology to the variation in oak pollen emissions increased with the oak pollen emission rate. The evaluation results using in-situ surface data revealed that the model underestimated pollen concentrations and was unable to accurately reproduce the peak pollen episodes. The model error was likely due to uncertainty in climatology-based C _e used for the estimation of oak pollen emissions and inaccuracy in the wind fields from the Weather Research and Forecast (WRF) model.  相似文献   

Important meteorological variables for statistical long-term air quality prediction in eastern China     

Libo?Zhang  Yongqiang?LiuEmail authorView author&#;s OrcID profile  Fengjun?Zhao 《Theoretical and Applied Climatology》2018,134(1-2):25-36

Weather is an important factor for air quality. While there have been increasing attentions to long-term (monthly and seasonal) air pollution such as regional hazes from land-clearing fires during El Niño, the weather-air quality relationships are much less understood at long-term than short-term (daily and weekly) scales. This study is aimed to fill this gap through analyzing correlations between meteorological variables and air quality at various timescales. A regional correlation scale was defined to measure the longest time with significant correlations at a substantial large number of sites. The air quality index (API) and five meteorological variables during 2001–2012 at 40 eastern China sites were used. The results indicate that the API is correlated to precipitation negatively and air temperature positively across eastern China, and to wind, relative humidity and air pressure with spatially varied signs. The major areas with significant correlations vary with meteorological variables. The correlations are significant not only at short-term but also at long-term scales, and the important variables are different between the two types of scales. The concurrent regional correlation scales reach seasonal at p < 0.05 and monthly at p < 0.001 for wind speed and monthly at p < 0.01 for air temperature and relative humidity. Precipitation, which was found to be the most important variable for short-term air quality conditions, and air pressure are not important for long-term air quality. The lagged correlations are much smaller in magnitude than the concurrent correlations and their regional correction scales are at long term only for wind speed and relative humidity. It is concluded that wind speed should be considered as a primary predictor for statistical prediction of long-term air quality in a large region over eastern China. Relative humidity and temperature are also useful predictors but at less significant levels.  相似文献