共查询到20条相似文献，搜索用时 140 毫秒
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Jianping LI Tiejun XIE Xinxin TANG Hao WANG Cheng SUN Juan FENG Fei ZHENG Ruiqiang DING 《大气科学进展》2022,39(4):625-642
In this paper,we investigate the influence of the winter NAO on the multidecadal variability of winter East Asian surface air temperature(EASAT)and EASAT decadal prediction.The observational analysis shows that the winter EASAT and East Asian minimum SAT(EAmSAT)display strong in-phase fluctuations and a significant 60-80-year multidecadal variability,apart from a long-term warming trend.The winter EASAT experienced a decreasing trend in the last two decades,which is consistent with the occurrence of extremely cold events in East Asia winters in recent years.The winter NAO leads the detrended winter EASAT by 12-18 years with the greatest significant positive correlation at the lead time of 15 years.Further analysis shows that ENSO may affect winter EASAT interannual variability,but does not affect the robust lead relationship between the winter NAO and EASAT.We present the coupled oceanic-atmospheric bridge(COAB)mechanism of the NAO influences on winter EASAT multidecadal variability through its accumulated delayed effect of~15 years on the Atlantic Multidecadal Oscillation(AMO)and Africa-Asia multidecadal teleconnection(AAMT)pattern.An NAO-based linear model for predicting winter decadal EASAT is constructed on the principle of the COAB mechanism,with good hindcast performance.The winter EASAT for 2020-34 is predicted to keep on fluctuating downward until~2025,implying a high probability of occurrence of extremely cold events in coming winters in East Asia,followed by a sudden turn towards sharp warming.The predicted 2020/21 winter EASAT is almost the same as the 2019/20 winter. 相似文献
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Xiangdong ZHANG Yunfei FU Zhe HAN James E.OVERLAND Annette RINKE Han TANG Timo VIHMA Muyin WANG 《大气科学进展》2022,39(4):553-565
Three striking and impactful extreme cold weather events successively occurred across East Asia and North America during the mid-winter of 2020/21.These events open a new window to detect possible underlying physical processes.The analysis here indicates that the occurrences of the three events resulted from integrated effects of a concurrence of anomalous thermal conditions in three oceans and interactive Arctic-lower latitude atmospheric circulation processes,which were linked and influenced by one major sudden stratospheric warming(SSW).The North Atlantic warm blob initiated an increased poleward transient eddy heat flux,reducing the Barents-Kara seas sea ice over a warmed ocean and disrupting the stratospheric polar vortex(SPV)to induce the major SSW.The Rossby wave trains excited by the North Atlantic warm blob and the tropical Pacific La Nina interacted with the Arctic tropospheric circulation anomalies or the tropospheric polar vortex to provide dynamic settings,steering cold polar air outbreaks.The long memory of the retreated sea ice with the underlying warm ocean and the amplified tropospheric blocking highs from the midlatitudes to the Arctic intermittently fueled the increased transient eddy heat flux to sustain the SSW over a long time period.The displaced or split SPV centers associated with the SSW played crucial roles in substantially intensifying the tropospheric circulation anomalies and moving the jet stream to the far south to cause cold air outbreaks to a rarely observed extreme state.The results have significant implications for increasing prediction skill and improving policy decision making to enhance resilience in“One Health,One Future”. 相似文献
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QIN Xiao-Hao 《大气和海洋科学快报》2010,3(3):170-175
In this paper, several sets of observing system simulation experiments (OSSEs) were designed for three typhoon cases to determine whether or not the additional observation data in the sensitive regions identified by conditional nonlinear optimal perturbations (CNOPs) could improve the short-range forecast of typhoons. The results show that the CNOPs capture the sensitive regions for typhoon forecasts, which implies that conducting additional observation in these specific regions and eliminating initial errors could reduce forecast errors. It is inferred from the results that dropping sondes in the CNOP sensitive regions could lead to improvements in typhoon forecasts. 相似文献
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With temperatures increasing as a result of global warming,extreme high temperatures are becoming more intense and more frequent on larger scale during summer in China.In recent years,a variety of researches have examined the high temperature distribution in China.However,it hardly considers the variation of temperature data and systems when defining the threshold of extreme high temperature.In order to discern the spatio-temporal distribution of extreme heat in China,we examined the daily maximum temperature data of 83 observation stations in China from 1950 to 2008.The objective of this study was to understand the distribution characteristics of extreme high temperature events defined by Detrended Fluctuation Analysis(DFA).The statistical methods of Permutation Entropy(PE)were also used in this study to analyze the temporal distribution.The results showed that the frequency of extreme high temperature events in China presented 3 periods of 7,10—13 and 16—20 years,respectively.The abrupt changes generally happened in the 1960s,the end of 1970s and early 1980s.It was also found that the maximum frequency occurred in the early 1950s,and the frequency decreased sharply until the late 1980s when an evidently increasing trend emerged.Furthermore,the annual averaged frequency of extreme high temperature events reveals a decreasing-increasing-decreasing trend from southwest to northeast China,but an increasing-decreasing trend from southeast to northwest China.And the frequency was higher in southern region than that in northern region.Besides,the maximum and minimum of frequencies were relatively concentrated spatially.Our results also shed light on the reasons for the periods and abrupt changes of the frequency of extreme high temperature events in China. 相似文献
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1引言在自动站投入使用前绝大多数气象站使用的是EL型风向风速计,其瞬间风速是通过风速指示计人工测得的,人为因素大,精度不够,但人工测量给大风重要天气报、大风危险和解除报提供了依据,不会出现大风记录和报文之间的矛盾现象,而自动站的大风记录却不一样,其记录的大风的起止时间,极大风速及出现的时间是非常精确的,要求值班员实时注意查看自动站的大风记录,避免漏报、错报。由于自动站采集控制软件SAWSS在处理大风记录时存在不足,当大风达到不同的发报标准时不能及时报警,以提醒值班人员作出相应的处理,所以极易造成过时报,甚至漏报。 相似文献
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气象水文灾害的防灾减灾教育培训新进展 总被引：1，自引：0，他引：1
智协飞 《南京气象学院学报》2007,30(6):885-889
简要综述了第十届世界气象组织教育与培训大会的主题报告内容.本次大会主要讨论防灾减灾的气象水文教育与培训等问题,集中讨论了"备灾-预防和早期预警"、"减灾-应急、救援和重建"和"跨学科培训"等3个主题,强调集合数值预报系统对于估计出现极端天气事件的风险非常重要,同时必须培训气象、水文工作者使用集合预报中的概率预报信息.中国气象灾害监测、预测和预警已经从单纯提供一般意义上的气象灾害信息提升到有利于社会经济发展的气象灾害服务,既考虑自然因子也考虑经济发展的影响.在跨学科培训方面,将管理知识和气象知识结合起来,可以取得非常好的效果.大会建议提高世界气象组织区域培训中心以及各国气象水文部门培训单位的培训能力,主要通过提供防灾减灾的专门培训单元,对自然灾害风险管理短期课程进行指导,重视各国气象水文部门对于管理和传播领域培训的需求. 相似文献
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作物系数是计算作物蒸散量的关键参数。利用2006—2008年和2011年辽宁锦州玉米农田生态系统的涡度相关、气象、作物发育期及叶面积指数观测数据,分析不受水分胁迫条件下玉米逐日作物系数特征及其与叶面积指数的关系。研究表明:作物系数与玉米农田实际蒸散均呈单峰型变化,约在7月末至8月初达到最大值 (玉米开花吐丝期)。在此基础上,建立了不受水分胁迫条件下玉米逐日作物系数与叶面积指数关系 (达到0.01显著性水平), 同时,采用积温表示的标准化生育期方法模拟相对叶面积指数,并建立了逐日作物系数与相对叶面积指数关系 (达到0.01显著性水平),解决了无叶面积观测地区玉米逐日实际蒸散量的计算。研究结果可为玉米农田用水管理以及灌溉措施的制定提供参考。 相似文献
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玉米冠层内光合有效辐射(PAR)的大小直接影响冠层内叶片的光合作用,进而影响玉米净第一性生产力或作物产量的准确评估。为弄清玉米冠层内光合有效辐射的分布规律及其影响因子,基于锦州玉米农田生态系统于2006年生育期的光合有效辐射观测数据和叶面积指数动态观测数据,对玉米冠层光合有效辐射的垂直分布特征及其影响因子进行了分析。结果表明:玉米冠层内不同垂直层次叶片的PAR分布随生育期变化显著,与叶面积指数呈显著的负相关(R2=0.89);玉米冠层光合有效辐射的消光系数K值在生育期呈动态变化,约为0.76,且表现为苗期较大、生育后期较小。分析表明,在进行光合有效辐射及与此密切相关的光合作用模拟时,应考虑消光系数的动态变化。 相似文献
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采用MODIS数据重构夏玉米归一化植被指数生长曲线,提取并建立特征点位对应日期与作物进入不同物候期的实际日期之间的最佳匹配关系。研究表明:使用改进的SG（Savitzky-Golay）迭代滤波对最大值合成后的植被指数时间序列做平滑处理并进行Logistic曲线拟合,可得到时间分辨率为1 d的作物生长过程曲线,经与2013-2014年物候期实测数据匹配,选择利用动态阈值1提取七叶期,均方根误差为5.4 d;利用曲率最小值提取拔节期,均方根误差为6.4 d;利用动态阈值2提取抽雄期,均方根误差为6.0 d。经2015年物候期实测数据验证,3个关键物候期的遥感监测误差均在6 d以内。利用该方法可提高基于遥感数据开展大面积作物物候期监测识别的效率和准确率。 相似文献
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张兵 《南京气象学院学报》2018,10(1):1-5
光学遥感利用可见光、近红外和短波红外传感器对地物进行特定电磁谱段的成像观测,是遥感科技中发展最早,也是目前对地观测和空间信息领域中应用最为广泛的技术手段.随着近年来光学成像、电子学与空间技术的飞速发展,高空间、高光谱和高时间分辨率遥感技术不断取得新突破,为光学遥感图像处理与应用技术发展创造了前所未有的机遇和广阔前景.本文首先概述了光学遥感的基本原理和发展历程,然后重点介绍了光学遥感图像的数据特点及光学遥感图像处理技术与方法,阐述了光学遥感在生态环境、自然资源和国防安全等领域的应用情况,讨论了未来光学遥感信息技术与应用发展的几个主要方向和趋势. 相似文献
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同化观测数据可为作物生长模型的区域应用提供支持。该文定义了观测数据对模型参数的约束性,研究发现华北夏玉米观测数据对WOFOST模型的可约束参数主要包括初始总干物重、不同发育阶段的比叶面积、初始最大CO2同化速率、叶片衰老系数、初始土壤有效水、最大根深日增量以及初始根深的初始土壤水分含量等。建立了基于参数约束性分析的观测数据与作物生长模型同化方法和流程, 利用优化算法进行作物生长模型所有参数和变量初值的敏感性分析,遴选出各状态变量的敏感参数;根据拟合度与优化结果之间关系进行敏感参数的约束性分析,获得不同变量的可约束参数;组合优化可约束参数得到各参数最优值,由此实现了观测数据与作物生长模型的同化。约束性体现了观测数据对模型参数或变量初值的控制能力,可约束参数作为待优化参数使数据模型同化获得了最优结果。 相似文献
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在田间试验资料基础上，采用改进的发育模型和分区作物参数，结合前人有关研究成果建立了东北玉米区域动力模型，并利用模型模拟了12站40年 (1961~2000年) 玉米生长发育过程。确定抽雄期延迟天数为低温冷害指标，分析了历史低温冷害年及减产情况。模拟了典型冷害年和40年气候平均的0.25°×0.25°网格点玉米生长发育过程, 探讨了与区域气候模式结合进行低温冷害预报的方法。主要结论有:①玉米发育模型能够较好地模拟玉米发育期和发育期对低温冷害的响应，以抽雄期延迟天数为冷害指标评估的历史冷害发生状况基本符合历史实况。②模型有一定的模拟玉米生长量对低温冷害响应的能力，但还需要更多的试验数据校正品种参数，完善模型。③利用GIS技术，结合区域化的作物参数运行区域作物模型，是作物模型区域化应用的一种解决方案。④东北玉米区域动力模型解释性好，根据确定的害指标，以区域气候模式输出结果驱动玉米模型可以模拟和预测低温冷害，是农业气象灾害预测预报的一个有益的尝试。 相似文献
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半透明云风矢量高度指定是卫星风矢量算法的重要部分,需要来自半透明云体的辐射和云下背景辐射两个变量。云下背景辐射发生在云层下面,未被卫星直接观测到,为了在半透明云风矢量高度指定算法中更精确地获得云下背景辐射,使用风矢量附近无云区的红外/水汽散点图,估计云下背景辐射。分析表明:在追踪区域里存在无云区的情况下,追踪区的最高红外亮温可代表红外通道的背景辐射;而水汽通道的背景辐射,却在红外亮温高值区段内水汽亮温相对较低区段。追踪区内找不到无云区时应扩大搜索范围,找到无云区后可估计云下背景辐射。在半透明云风矢量高度指定算法中使用云下背景辐射估计的改进算法前后,计算FY-2气象卫星进行风矢量,并将结果与欧洲中期天气预报中心（ECMWF）分析场进行对比表明,在半透明风矢量高度指定算法中使用云下背景辐射估计,FY-2气象卫星风矢量误差明显降低。 相似文献
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Snow albedo is an important factor influencing the snow surface energy budget and snow melting,
yet uncertainties remain in the calculation of spectrally resolved snow surface albedo because the spectral
composition (visible versus near infrared) of the incident solar radiation is seldom available. The influence
of the spectral composition of the incoming solar radiation on the snow surface albedo, snow surface energy
budget, and final snow ablation is investigated through sensitivity experiments of four snow seasons at two
open sites in the Alps by using a multi-layer Snow-Atmosphere-Soil-Transfer scheme (SAST). Since the snow
albedo in the near infrared (NIR) spectral band is significantly lower than that in the visible (VIS) band,
and almost the entire NIR part of the solar radiation is absorbed in the top layer of the snow pack, given
a fixed amount of incoming solar radiation, a lower VIS/NIR ratio implies that more NIR radiation is
reaching the ground surface and more is absorbed by the top layer of the snow pack, therefore, speeding
up the snow melting and increasing the surface runoff, although a lesser part of the solar radiation in
the visible band is transmitted into and trapped by the sub-layer of the snow pack. The above VIS/NIR ratio
effect of the incoming solar radiation can result in a couple of days difference in the timing of snow
ablation and it becomes more significant in late spring when the total solar radiation is intensified with
seasonal evolution. Snow aging also slightly intensifies this VIS/NIR ratio effect. 相似文献
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农作物主要生长参数自动观测技术综述 总被引：2，自引：0，他引：2
农作物生长参数是描述作物生长和评价环境条件（包括农业气象灾害）对作物生长影响的重要数据,也是预测产量、指导农田管理的重要依据。介绍作物覆盖度、发育期、株高等主要生长参数国内外自动观测技术的研究进展及应用,探讨相关技术的原理、方法、可行性及局限性。分析表明：利用CCD图像传感器实时获取作物图像,采用计算机视觉及图像处理技术能更精准、快速、直观、动态获得作物覆盖度、发育期、形态、叶面颜色等实况特征,还可作为卫星遥感大面积作物长势地面验证及更进一步开展作物病虫害、作物营养供给情况自动监测的基础,具有广阔的推广前景。 相似文献
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选取2015年12月25日及2016年1月18日两次覆盖湖北的重污染天气过程,利用FY-3A(B)/MERSI卫星资料和气象、环境监测资料,应用图像色彩处理技术、可见光近红外通道反射率分析等技术,开展对湖北地区霾的遥感识别研究。研究结果表明:以不同波段进行红绿蓝三通道合成时,霾可以被识别,其中以全可见光模式合成时,霾以灰白色为主,比周围的云雾区略暗;以可见光、近红外、红外三通道合成时,霾以紫色、紫灰色为主,云类识别精细;以可见光、近红外两通道增强显示合成时,霾以紫灰色为主,与晴空地表及云区差异明显,但易将由小粒子组成的薄卷云误判为霾,需通过云顶黑体亮温进行剔除。通过建立红外亮温和可见光反射率识别指标,可将霾与晴空、厚云区区分开来,但很难与低云/雾区进行有效区分,加入对有效粒子半径敏感的近红外通道反射率后,借助两者在粒子大小上的差异,可在一定程度上解决这一问题,并通过地面人工观测资料进行分析验证。 相似文献