TIEGCM集合卡尔曼滤波同化模型设计及初步试验

选择参数化的电离层热层理论模型TIEGCM作为背景模型,基于COSMIC掩星观测的电子密度廓线数据,应用集合卡尔曼滤波方法建立全球电离层电子密度同化模型,实现了全球电离层的电子密度同化.同化结果表明,该同化模型能将观测资料有效同化到背景模式中,获得全球三维电离层电子密度.与背景模式相比,同化得到的电子密度相对于观测值的偏差显著下降.对于有同化和无同化参与的试验,N_mF₂的标准偏差分别降低约60%和20%.此外,分组同化与同时同化的结果对比显示,平均偏差改善基本一致,同时同化后的标准偏差在峰值高度以上略有减小.      

基于电子密度同化的热层大气密度预报方法

采用热层电离层耦合模式TIEGCM和集合卡尔曼滤波同化方法,利用同化COSMIC电离层掩星电子密度数据优化热层电离层参量,并将模式预报的大气密度与CHAMP卫星大气密度数据进行对比,分别开展模拟和实测数据的同化预报实验.在模拟数据同化实验中,状态向量包含温度、风场和离子成分的实验结果表明,仅优化温度即可达到最优的热层大气密度预报效果.在实测数据同化实验中,将温度作为状态向量参数,优化结果表明,循环同化过程中模式预报的大气密度相对偏差的均方根误差在48h内从38%减小到27%,同化稳定时间至少需要30h.预报过程中大气密度预报效果的改善持续时间为34h.这表明电子密度同化能够改善热层大气密度的预报精度,设计的实验方案合理可行,可获得较长的预报时效.      

全球电离层地图TEC数据的插值算法

由IGS工作组提供的全球电离层地图(GIM)是电离层重要的应用数据.卫星高度计能够提供全球实时的电离层延迟误差校正.利用GIM数据,以Jason-3时空分辨率进行电离层总电子含量(TEC)的时间维度插值和空间维度插值,其中空间维度插值采用了Kriging插值和双线性插值两种方法.针对两种插值方法得到的总电子含量,与平滑...     

数据同化在空间天气学中的应用

由太阳活动引起的耀斑和日冕物质抛射等短时间尺度变化的空间天气事件会影响并危害地球磁层、电离层、中高层大气、卫星运行安全以及人类健康,因此对这些空间天气事件的预测显得尤为重要。数据同化在稀疏观测和异步采集的情况下能够增加模型的预测能力,对模型变量进行自洽分析。在数值预报中引入数据同化方法,能够提高预测可信度。本文从数据同化方法的角度出发,主要分析了数据同化目前在大气、电离层、磁层、太阳及其他行星科学研究中的应用,并初步讨论了数据同化未来在空间天气方面的应用。      

利用F区电离层特性参量获取等效中性风的方法及讨论

讨论利用电离层特性参量获取F层峰值高度附近中性风信息的三类方法.这些方法主要有:传统的和改进的伺服理论方法、借助电离层模式和数据同化思想的方法和刘立波等提出的方法.并以美国Millstone Hill非相干散射雷达浓度剖面和离子速度数据,以及澳大利亚Beveridge(37°S,144°E)FPI风场和测高仪数据为个例,初步考察利用电离层特性数据导出的等效中性风与观测值的一致性.     

电离层特征参量的自相关原理插值方法

通过选用合适的电离层平稳性参数, 建立相应的正定自相关系数模型, 利用自相关分析原理, 提出了一种针对电离层特征参量历史缺失数据插值处理的新方法. 该方法能够提高Muhtarov 和Kutiev 在1999 年提出的自相关系数法的插值精度, 通常情况下可以把误差降低1 到2 个百分点以上, 有时甚至能降低接近9 个百分点, 在很大程度上改善了对电离层历史缺失数据的插值处理效果. 此外, 本文还对插值误差随季节、太阳活动性和地理纬度等的变化规律进行了分析.      

利用RDSS系统测量数据提取电离层TEC参数的研究

提出了一种基于无线测定卫星业务(RDSS)系统观测数据提取电离层TEC参数的方法,利用此方法计算分析了2006年5月地面中心地区电离层垂向TEC的日变化趋势.研究结果表明,利用RDSS系统观测数据提取的电离层垂向TEC,在北京时间每日凌晨0400时左右达到最小值,在午后1400时左右达到最大值,符合电离层TEC参数受太阳活动影响较大的物理规律.结果说明研究方法是可行且有效的,文章还对可能存在的误差进行了探讨.      

多频GNSS电离层折射误差修正方法CSCD

针对电离层折射误差较大的特点,分别对GPS(Global Positioning System)和BDS(Bei Dou Navigation Satellite System)的单一频率的电离层折射误差进行了分析,并将不同频率进行线性组合,计算出组合后的电离层折射误差。此方法修正了双频一阶项、三频一阶项和三频二阶项电离层折射误差。由于电离层延迟修正的同时会放大观测噪声,为此分析比较了不同频率组合修正后的观测噪声,为最佳频率组合的选取提供了理论方法。     

新版亚大地区F2电离层频率预测方法

新版亚大地区F2电离层频率预测方法根据电离层参量与太阳黑子数12个月流动平均值R12的互相关原理, 使用R12代替了由重庆F2层临界频率导出的电离层指数Ic, 减小了R12转换为Ic时的误差; 并在原亚大地区F2电离层频率预测方法的基础上审慎地选择并增补了一些探测站的大量数据, 不再使用三组不 同R12值的B系数去插值, 避免了中间环节所带来的插值误差. 并对几种不同方法的预测结果进行了比较, 结果显示新版本的预测精度较高.      

基于北斗GEO卫星双频观测值连续监测电离层延迟

利用北斗GEO卫星观测数据直接计算电离层延迟。由于GEO卫星具有固定穿刺点和静地的特性,使得观测站监测电离层变化时可不考虑空间变化,并可进行连续不间断监测。通过分析北斗GEO卫星三种频率码伪距和载波相位观测值不同组合,选取B1&B2双频计算电离层延迟为最优组合,采用相位平滑伪距的方法计算电离层延迟TEC,相较其他电离层模型,该方法的优点是不会引入模型误差,可得到连续的高精度的电离层延迟监测结果。     

Fine structure of the ionospheric plasma bubbles observed by the OI 6300 and 5577 airglow images

Simultaneous measurements of the ionospheric airglow OI 630.0 nm and OI 557.7 nm emissions have been carried out by means of an all-sky CCD imager system at Cachoeira Paulista, since October 1998. During a developed phase of plasma depletion (bubble) in the equatorial anomaly region, both emissions show intensity depletions along the geomagnetic North—South direction, and also bifurcation of the bubbles. It is frequently observed that the OI 557.7 image shows more fine structure of the bubble than the OI 630.0. The amplitude of the intensity depletion was also larger for OI557.7 than OI630.0. This might be due to the difference in life time between the O(¹D) and O(¹S) states, which are responsible for the OI 630.0 and OI 557.7 emissions, respectively. The O(¹D) might be affected by thermal relaxation and diffusion processes before the radiative transition.     

Adelaide地区大气重力波的气辉观测

利用澳大利亚Adelaide(34.5°S,138.5°E)地区7年(1995-2001年)的OH和OI气辉观测数据,以及同地区中频雷达所测背景风场数据,通过最大熵谱分析方法,统计分析了该地区大尺度重力波的传播特性.结果表明,(1)在中层顶气辉观测区,利用OH气辉探测到48个重力波事件,利用OI气辉探测到29个重力波事件,这些重力波的周期和水平相速度分别集中在68 min和36 m/s左右,具有东南向的优势传播方向,平均仰角为8°～10°,接近水平方向传播;(2)通过OH气辉和OI气辉观测到了同一个重力波事件,并根据两个高度上观测到的扰动相位差判断该重力波为上行波.      

Ionospheric plasma bubble zonal drift: a methodology using OI 630 nm all-sky imaging systems

With the recent advances in all-sky imaging technology for nightglow emission studies, the F-region OI 630 nm emission has become an important tool for ionospheric/thermospheric coupling studies. At equatorial and low latitude regions, the all-sky imaging observations of the OI 630 nm emission show quasi north-south aligned intensity depletion bands, which are the optical signatures of large scale F-region plasma irregularities. By observing the motion of the intensity depleted bands it is possible to infer the ionospheric plasma zonal velocity of the depletion. The north-south aligned structures seen in the field of view of the all-sky imaging system corotate with the ionospheric plasma, so that by calculating the spatial displacements occurring during successive OI 630 nm emission images we can infer the ionospheric plasma drift velocity. However, the plasma bubbles have their own internal space-time dynamics leading to changes in their shape and dimensions and this may induce some errors in the calculated drift velocities. In this paper we take into account the space-time changes in the plasma bubbles in order to calculate the ionospheric plasma zonal drift velocities using the OI 630 nm nightglow emission.     

Arctic — Antarctic night airglow comparisons

Airglow observations from Eureka, Canada (80° N) and South Pole (90° S) observatories have been made through the winters during the past 1/2 solar cycle. Seasonal and solar activity changes are evident. The intensities also show temporal variations due to wave activity, with periods from 6 hours to 15 days, particularly in the Arctic OI and Na emissions. Comparisons are made of the OH intensities measured at Eureka and South Pole during their respective winters.     

Ground and satellite-based observations of ionospheric plasma bubbles and blobs at 5.65° latitude in the Brazilian sector

This investigation uses simultaneous observations from all-sky imager system and an ionosonde collocated at Araguatins (5.65° S, 48.07° W and dip-latitude of 4.17° S), a near-equatorial region in Brazil. These simultaneous observations were used to investigate the occurrence of plasma bubbles and blobs in the field of the imaging system and their association with atypical range Spread-F signature in ionograms. Also, in-situ observation of plasma density from Swarm satellites were used to support the ground-based observations. Using a few cases, a methodology will be established to identify in the plasma blobs (atypical ESF) in the ionograms when there is the simultaneous observation of plasma bubbles and blobs in the field of view of the ionosonde. For this purpose, simultaneous sequence of OI 630.0 nm nightglow images and ionograms are presented for different case studies; 1. when there is the absence of a plasma bubble or blob, 2. when there is only the occurrence of plasma bubbles and 3. when there is the occurrence of plasma bubbles and blobs, in order to compare traces in the ionogram in all these case studies. With these we can cover all kinds of signatures in the ionograms corresponding to no irregularities, plasma bubbles only and plasma bubbles-blobs. These OI 630.0 nm nightglow and ionograms recorded simultaneously make it possible to establish a novel methodology to recognize in ionograms cases when there is the occurrence of Spread-F signature associated with bubble-blob in the FOV of the ionosonde.     

中国山西地区法布里-珀罗干涉仪测风能力及数据质量检验

介绍了中国气象局山西岢岚大气观测站(39°N, 112°E) 法 布里-珀罗干涉仪(FPI) 的基本 构造、测风能力、程序处理流程、数据质量控制方法以及检验情况. 岢 岚观测站FPI可以观测892.0 (OH)nm, 557.7 (OI)nm和630.0 (OI)nm 波 长处气辉谱线的多普勒移动, 分别计算对应87km, 97km和250km高度处 的大气风速和大气温度, 可给出中间层顶区域及热层风的大气潮汐和扰动 情况. 采用水平风模型(HWM)输出结果进行交叉检验, 对FPI测风数据质量进行验证. 结果显示, 岢岚大气观测站FPI仪器的测风数据 在长期趋势上与HWM模式的输出数据一致, 风速变化幅度有季节性差异, 数据质 量控制方法有效, 测风误差在87km高度处为5.7m·s-1, 97km处 为1.3m·s-1, 250km处为4.1m·s-1, 测风数据 通过了可靠性检验.      

Relevant aspects of equatorial plasma bubbles under different solar activity conditions

Observations of the OI 630 nm nightglow emission using a wide-angle imaging system have been carried out at Cachoeira Paulista (22.7° S, 45° W, 15.8° S dip latitude), Brazil during the period 1987 to 1999. The OI 630 nm images obtained during this period show frequently the optical signature of the plasma bubble (quasi north-south aligned depleted intensity regions). During the period studied a strong seasonal variation was noticed in the plasma bubble formations. Also, it was observed that, during high solar activity, the plasma bubble bifurcation occurrences were higher than during low solar activity. Important features from this set of observations are presented and discussed in this paper.     

Low ionization lines in high luminosity quasars: The calcium triplet

In order to investigate where and how low ionization lines are emitted in quasars we are studying a new collection of spectra of the CaII triplet at λ8498, λ8542, λ8662 observed with the Very Large Telescope (VLT) using the Infrared Spectrometer And Array Camera (ISAAC). Our sample involves luminous quasars at intermediate redshift for which CaII observations are almost nonexistent. We fit the CaII triplet and the OI λ8446 line using the Hβ profile as a model. We derive constraints on the line emitting region from the relative strength of the CaII triplet, OI λ8446 and Hβ.