EOS／MODIS卫星遥感监测四川省森林火灾的阈值设置研究

本文以2004年4~6月四川省农业气象中心EOS/MO-DIS资料为基础,参照四川省护林防火办公室的地面森林火灾观测资料,在充分研究EOS/MODIS传感器性能的基础上,通过多次试验研究,根据四川林区的气候特点,设置合理的川西山区森林火灾遥感监测参数,提高了森林火灾遥感监测的准确性。     

EOS/MODIS卫星遥感监测四川省森林火灾的阈值设置研究

本文以2004年4～6月四川省农业气象中心EOS/MODIS资料为基础,参照四川省护林防火办公室的地面森林火灾观测资料,在充分研究EOS/MODIS传感器性能的基础上,通过多次试验研究,根据四川林区的气候特点,设置合理的川西山区森林火灾遥感监测参数,提高了森林火灾遥感监测的准确性.     

EOS／MODIS卫星资料在贵州省林火监测中的应用

在森林火灾预防和扑救中,及时而准确地监测森林火灾和火环境的变化是各级防火人员最为关注的问题之一。对于大面积森林火灾,依靠地面人力和飞机监测,不但费用高,而且工作繁杂,特别是对于盲区的监测计算精度低。借助于卫星遥感和林火地理信息系统,进行计算机统计分析,可以克服这些不足,提供较为详细的森林火灾有关数据。该文介绍EOS／MODIS卫星遥感资料在贵州省森林火灾监测的应用,从理论上分析EOS／MODIS数据林火信息的识别和提取的原理及方法。     

基于遥感和地理信息系统的河南省森林防火系统

河南森林火灾较多,给森林资源造成较大损失。由于在火灾预警、监测、救灾中,没有一套有效的现化化的手段,常常延误较多的扑救时间,造成不必要的经济和森林资源的损失。在多年森林火灾遥感监测的基础上,利用“3S”技术,从森林火灾预警—监测—扑救等过程入手,建立了自动化、流程化的河南省森林遥感防火系统。介绍了河南省森林遥感防火系统的主要技术思路及各部分主要功能。该系统的资料接收、处理、服务等都实现了软件支持,并利用“3S”技术,使火点监测图像、气象和森林火险预报与地理信息叠加。     

甘肃省森林、草原火灾的成因分析

简要介绍了利用NOAA极轨气象卫星资料监测森林 ,草原火灾的原理 ,结合实际工作经验 ,阐明了引起甘肃省森林、草原火灾的成因、林牧区的地理分布及特点     

气象卫星资料在森林火灾监测中的应用

本文综述国内外森林火灾监测中如何利用气象卫星辐射观测资料,介绍了林火监测原理、监测效果、存在问题与发展前景.     

森林火灾天气等级确定及监测预报方法

利用内蒙古和山西两地1994－1999年6次特大森林火灾的气候资料，探讨了火灾发生的环境条件和天气气候条件，并建立了森林火险天气等级、监测和预报方法。     

湖南省森林火灾时空分布特征及其气象成因分析

利用湖南省2008-2017年10年森林火灾数据、卫星MODIS和VIIRS监测资料及常规气象资料，统计分析了湖南省森林火灾时空分布特征，分析结果表明：近10年湖南省森林火灾高发月份是2、3、4月， 3月最多，总次数为3800次，森林火灾在邵阳发生次数最多，郴州、长沙和永州次之。森林火灾受灾面积最大的是永州市、怀化市、邵阳市，达6800-7500公顷。重点分析了2018年2月14-19日湖南致灾严重的森林火灾过程与气象条件的关系，结果表明，森林火灾期间，气温偏高、相对湿度较小，降水量少，平均风速一般超过0.5m/s，火灾严重时段最大风速增大到6m/s左右，风向以偏东风和偏南风为主，湖南高低空受上下一致的西南风气流控制，天气形势较稳定。     

森林火灾的 CINRAD/SA 雷达监测

对 2007 年浙江省南部地区 10 次距离雷达站 5～100 km、不同规模的森林火灾进行分析,发现温州新一代多普勒天气雷达 CINRAD/SA 能对森林火灾进行监测.雷达分析发现,火灾引起的回波具有水平尺度小、回波顶高度低、回波强度强等和地物回波相类似的特征,径向速度图上一般有辐散速度对的出现,并具有不同于气象回波的特征.受地理位置和天气系统等影响,发生在大陆山区的森林火灾其回波特征较海岛和沿海山区的森林火灾更为显著.本文还对应用雷达监测森林火灾的前景和局限性进行了分析.雷达回波可以识别、监测不同规模森林火灾的发生和演变,为森林火灾的监测提供了崭新的手段,也为多普勒天气雷达的应用拓展新的领域.     

NOAA/AVHRR遥感监测森林火灾的准确性研究

四川地处长江上游,增加森林植被,减少森林火灾,对于治理水土流失,改善生态环境,促进长江流域经济发展,具有重要意义.NOAA/AVHRR的各个通道对于监测森林火灾都有重要作用,通过选择合理的参数值,可有效提高NOAA/AVHRR对森林火灾的监测能力.本文以2003年的地面林(荒)火资料及四川省农气中心NOAA/AVHRR卫星遥感资料为基础,经多次试验,认为选择T3>317.0K 、R2<0.12、T4>260K、15K相似文献   

遥感-测站相结合的动态雪深反演方法初探

该文结合2000年专用传感器微波成像仪(SSM/I)的亮温数据和我国观测站雪深资料,提出了一种遥感-测站相结合的动态雪深反演方法,试图用统计关系的时空动态化方案克服理论上亮温与不同类型积雪之间物理关系的复杂性,从而提高测站稀疏区和雪盖边缘区的雪深反演精度。其最大特点在于反演系数并不固定,而随时间和空间变化,较好地改善了单一系数反演方法中积雪物理性质的区域性差异和时间(季节)性差异带来的反演误差。初步分析表明:这种遥感-测站相结合的反演方法所得的积雪空间分布连续性好,在雪盖边缘区和站点稀疏区也能得到较合理的雪深数据;与静态遥感反演法和可见光雪盖面积相比,这种方法克服了它们在华北和华中低估雪盖面积的缺点,积雪面积分布更接近真实场,对西部积雪分布的反演也有一定改善。     

一种新的资料同化方法

为寻求一种快速有效的四维变分资料同化(英文缩写4DVar)作了有意义的尝试,提出了映射观测的新概念和反向四维变分资料同化的新思路,并以此为基础建立了三维变分映射资料同化(英文缩写为3DVM:3-DimensionalVariational data assimilation of Mapped observation)。该方法与传统的四维变分资料同化一样,不仅考虑了模式的动力和物理约束,使得同化后的初值与模式协调,而且通过模式方程对同化窗口中不同时刻的观测资料作了最佳拟合。与传统四维变分同化方法不同的是,由3DVM得到的初值不在同化窗口的始端,而在窗口的末端。正是所求初值时刻的改变,使得该方法的计算代价大大减少,几乎与三维变分资料同化(英文缩写3DVar)相当,这实际上是用3DVar的代价实现了4DVar的功能。同时,由于3DVM不再需要切线性和伴随近似来计算代价函数的梯度也提高了同化的精度。对具体的台风个例(Dan)用AMSU-A反演的温度场进行变分同化模拟试验,发现3DVM能比传统4DVar产生更好的初值,而且所花计算时间只需4DVar的1/7。     

A New Approach to Data Assimilation

A significant attempt to design a timesaving and efficient four-dimensional variational data assimilation (4DVar) has been made in this paper, and a new approach to data assimilation, which is noted as 'three-dimensional variational data assimilation of mapped observation (3DVM)' is proposed, based on the new concept of mapped observation and the new idea of backward 4DVar. Like the available 4DVar, 3DVM produces an optimal initial condition (IC) that is consistent with the prediction model due to the inclusion of model constraints and best fits the observations in the assimilation window through the model solution trajectory. Different from the 4DVar, the IC derived from 3DVM is located at the end of the assimilation window rather than at the beginning conventionally. This change greatly reduces the computing cost for the new approach, which is almost the same as that of the three-dimensional variational data assimilation (3DVar). Especially, such a change is able to improve assimilation accuracy because it does not need the tangential linear and adjoint approximations to calculate the gradient of cost function. Therefore, in numerical test, the new approach produces better IC than 4DVar does for 72-h simulation of TY9914 (Dan), by assimilating the three-dimensional fields of temperature and wind retrieved from the Advanced Microwave Sounding Unit-A (AMSU-A) observations. Meanwhile, it takes only 1/7 of the computing cost that the 4DVar requires for the same initialization with the same retrieved data.     

帕默尔旱度模式在绵阳干旱研究中的应用

本文引用帕默尔旱度模式建模思路和建模方法,对其中可能蒸散量计算方法进行修正,采用国际通用的彭曼-蒙蒂斯公式,利用绵阳1954~2007年的气象资料和部分年份的土壤湿度观测资料,建立绵阳的帕默尔旱度模式,并将实际旱情与计算的帕默尔干旱指数进行了对比验证,帕默尔旱度模式能较好地反映实际旱情。      

海岛测站大风资料代表性的数值模型分析

对大风情形下实际海岛的风场结构进行数值模拟,结果表明海岛测风明显受海岛地形的影响。通常运用对数或指数风廓线公式,对海岛测风资料作简单高度换算以得到海面10 m风速的订正方法一般是不合理的。通过海岛测站观测值与模拟值的对比分析,说明借助数值模拟寻求测风资料订正方法的必要性与可能性。     

用一种新的同化方法同化降水量资料

Observations of accumulated precipitation are extremely valuable for effectively improving rainfall analysis and forecast. It is, however, difficult to use such observations directly through sequential assimilation methods, such as three-dimensional variational data assimilation or an Ensemble Kalman Filter. In this study, the authors illustrate a new approach that makes effective use of precipitation data to improve rainfall forecast. The new method directly obtains an optimal solution in a reduced space by fitting observations with historical time series generated by the model; it also avoids the implementation of tangent linear model and its adjoint. A lot of historical samples are produced as the ensemble of precipitation observations with the fully nonlinear forecast model. The results show that the new approach is capable of extracting information from precipitation observations to improve the analysis and forecast. This method provides comparable performance with the standard four- dimensional variational data assimilation at a much lower computational cost.     

含有开关参数化物理过程的模式变分资料同化的非光滑优化方法:几个理论问题

时间、空间上离散的模式如果含有带开关的参数化物理过程，某些对应的变分同化问题可以看成为非光滑优化问题。本系统地讨论了与此相关的几个理论问题。首先，利用次梯度这个非光滑优化中的基本概念可以对通常的伴随方程的解进行清楚的解释和定义。利用一个带对流调整的多层扩散模式，演示了通常的伴随方程的解在奇异点处不是由代价函数的Gateaux导数构成，而是代价函数的一个次梯度。其次，在非光滑优化的框架下对现有的解决这类问题的方法进行了评述。这些方法包括：（1）利用光滑优化方法和通常的伴随模式，并且讨论了这个方法的收敛条件；（2）正则化方法。这个方法是把模式中不光滑的项用光滑的项近似，以把问题变为光滑优化问题。（3）次梯度方法。这个方法利用通常的伴随模式来计算一个次梯度，是收敛的算法，不过收敛速度很慢。（4）非光滑优化中的Bundle方法。这个方法比次梯度方法收敛得快，不过需要利用所有的次梯度信息。由于计算所有的次梯度十分困难，现有的Bundle方法大都进行了一些改变，仅需要用户能够计算出一个次梯度。不过这个改变是无奈的，多个次梯度的信息可以提高Bundle方法的效率。本最主要的工作是提出了集值伴随方程的概念。集值伴随模式可以在奇异点处计算出所有支撑次梯度，因此利用集值伴随方程有可能提出基于Bundle方法的更好算法。     

Soil moisture: a residual problem underlying AGCMs

This paper critically reviews and intercompares land surface schemes (LSSs) as used in atmospheric general circulation models (AGCMs) to simulate soil moisture and its response to a warmer climate, and potential evapotranspiration approaches as used in operational soil moisture monitoring and in predicting the response of soil moisture to a warmer climate. AGCM predictions of overall soil moisture change are in broad agreement but disagree sharply in some regions. Intercomparison projects have sought to evaluate the LSSs used by AGCMs for both accuracy and consistency. These studies have found that different LSSs can produce very different simulations even when supplied with identical atmospheric forcing. As well, LSSs that produce similar surface results from present-day or control climates often diverge when forced with climatic change data. Furthermore, no single LSS has been identified that produces an adequate simulation of all of temperature, moisture, evapotranspiration and runoff. AGCM LSSs must resolve the surface energy balance (SEB) in order to compute realistic heat fluxes between with the atmospheric model. LSSs have been used with AGCMs in both on-line (fully coupled) and off-line modes. In off-line climatic change experiments, AGCM predictions of atmospheric temperature and precipitation have been used, along with model downward radiative fluxes at the surface, to drive their own uncoupled LSS. However, there are simple non-energy-balance methods for estimating evapotranspiration that have been traditionally used in agricultural and meteorological applications. These schemes compute a potential evapotranspiration (PE) based on temperature and/or net radiation inputs, with the PE modified based on the availability of soil moisture. Operational PE approaches have also been used with AGCM data in off-line climate change experiments. The advantages of this approach are that it is simpler and requires less information, although (like the off-line SEB approach) it leaves out the simulation of feedbacks between the surface and the atmosphere.Although the SEB approach is essential for LSSs that must be coupled to AGCMs, this does not necessarily make it superior to an off-line operational PE LSS when it comes to quantities such as soil moisture. The quality of current observational data is insufficient to demonstrate that either approach is better than the other. Both approaches should continue to be used and intercompared when predicting the impacts of climatic change on soil moisture.     

Automated estimation of local wind enhancement in Novorossisk

A new concept of automated evaluation of local wind maximum speed in mountain regions is considered. The approach is based on taking into account the empirical dependence between the maximum registered wind enhancement in a particular district and prognostic evaluations of background meteorological parameters less detailed in space. Empirical dependencies are established for the Novorossisk region from the data of spring and fall of 2008. It is shown that the new approach complements the technology of maximum wind speed evaluation at the ground currently in use. In most cases, it allows rather accurate evaluation of expected local wind enhancement up to 20–30 m/s in Novorossisk in warm period.     

Field measurement of air-sea gas transfer: A methodical search

In order to obtain field data of ocean-atmosphere gas transfer coefficients, it is preferable to measure the interfacial gas flux in the air rather than in the water. This approach has been reported in the literature for CO₂. However, it is shown here that ²²²Rn and methyliodide, CH₃I, may be more suitable gases for air-side flux measurements.