利用OI 135.6 nm夜气辉辐射探测电离层峰值电子密度及电子总含量的研究

测量夜间135.6 nm大气气辉辐射强度是目前有效的电离层探测方式之一,我国即将在风云三号卫星上搭载仪器,利用该波段夜气辉辐射测量来反演电子总含量(本文所指电子总含量表示卫星高度以下大气柱的电子含量)及峰值电子密度,因此非常有必要开展相关的气辉发光模型及反演研究.在介绍氧原子135.6 nm波段夜气辉激发机制基础上,考虑辐射在传输过程中受到大气氧原子的散射及氧气分子的吸收,采用迭代法求解包含多次散射及大气吸收衰减的辐射传输方程,得到该波段的体发射率,最终通过考虑包含辐射传输的路径积分计算得到135.6 nm气辉辐射强度值.对结果的分析表明:该气辉模型能较好地描述体发射率随高度的分布特征,计算得到的135.6 nm夜气辉辐射强度在不同时空及太阳活动的分布与相应条件下峰值电子密度(N_mF₂)及电子总含量(TEC)的分布基本一致.相同的时空及太阳活动输入条件下,模式计算的135.6 nm夜气辉辐射强度与国外同类模式结果的值平均偏差约为3%.文中最后介绍了通过135.6 nm夜气辉的辐射强度探测来反演电离层峰值电子密度N_mF₂及电子总含量TEC的反演方法.     

高层大气测风用地基F-P干涉仪的数值模拟

热层大气风场、温度场对热层-电离层耦合研究、热层环流特性研究以及太阳活动和地磁活动研究等有着重要意义,同时其也是航天器飞行环境预报的重要物理基础.目前,由于热层所处位置较高,大气非常稀薄,风场探测难度较大,因此针对热层大气风场的探测手段非常少.Fabry-Perot（FP）光学干涉仪可通过观测气辉来进行风场探测,其对成像系统像质要求不高,在设计中无需过分追求像质,已经成为热层风场测量的重要工具.由于风场观测气辉的辐射强度非常微弱,因此必须进行FP干涉仪测量系统优化,获得相对较强的辐射强度,以提高风场测量精度.但目前,对FP干涉仪系统优化方面的研究较少,且在测风误差评价方面的工作也不充实.本文通过热层测风用固定间距标准具地基FP干涉仪数值模型的建立,解决FP干涉仪设计过程中各参量的优化问题,并提出一种新的测风误差估算方法.数值模型结果分析表明,在目前探测器观测技术水平下,采用全部干涉环参与计算并结合像元合并技术进行风速反演可最大限度地提高测量精度.此外,由于气辉辐射强度是影响热层大气风场测量精度的重要因素,因此在仪器测风精度性能评价时需确定观测对象强度,即气辉的辐射强度.     

Application of tomographic inversion in studying airglow in the mesopause region

It is pointed out that observations of periodic nightglow structures give excellent information on atmospheric gravity waves in the mesosphere and lower thermosphere. The periods, the horizontal wavelengths and the phase speeds of the waves can be determined from airglow images and, using several cameras, the approximate altitude of the luminous layer can also be determined by triangulation. In this paper the possibility of applying tomographic methods for reconstructing the airglow structures is investigated using numerical simulations. A ground-based chain of cameras is assumed, two-dimensional airglow models in the vertical plane above the chain are constructed, and simulated data are calculated by integrating the models along a great number of rays with different elevation angles for each camera. After addition of random noise, these data are then inverted to obtain reconstructions of the models. A tomographic analysis package originally designed for satellite radiotomography is used in the inversion. The package is based on a formulation of stochastic inversion which allows the input of a priori information to the solver in terms of regularization variances. The reconstruction is carried out in two stages. In the first inversion, constant regularization variances are used within a wide altitude range. The results are used in determining the approximate altitude range of the airglow structures. Then, in the second inversion, constant non-zero regularization variances are used inside this region and zero variances outside it. With this method reliable reconstructions of the models are obtained. The number of cameras as well as their separations are varied in order to find out the limitations of the method.     

Monitoring air pollution in China from geostationary satellite: A synthetic study using simulated observations

We simulated geostationary satellite observations to assess the potential for high spatial-and temporal-resolution monitoring of air pollution in China with a focus on tropospheric ozone(O_3), nitrogen dioxide(NO_2), sulfur dioxide(SO_2), and formaldehyde(HCHO). Based on the capabilities and parameters of the payloads onboard sun-synchronous satellites, we simulated the observed spectrum based on a radiative transfer model using a geostationary satellite model. According to optimal estimation theory, we analyzed the sensitivities and retrieval uncertainties of the main parameters of the instrument for the target trace gases. Considering the retrieval error requirements of each trace gas, we determined the major instrument parameter values(e.g., observation channel, spectral resolution, and signal-to-noise ratio). To evaluate these values, retrieval simulation was performed based on the three-dimensional distribution of the atmospheric components over China using an atmospheric chemical transportation model. As many as 90% of the experiments met the retrieval requirements for all target gases. The retrieval precision of total-column and stratospheric O_3 was 2%. In addition, effective retrieval of all trace gases could be achieved at solar zenith angles larger than 70°. Therefore, the geostationary satellite observation and instrument parameters provided herein can be used in air pollution monitoring in China. This study offers a theoretical basis and simulation tool for improving the design of instruments onboard geostationary satellites.     

FY-3气象卫星紫外臭氧总量探测仪辐亮度在轨定标与反演结果分析

FY-3气象卫星上搭载的紫外臭氧总量探测仪TOU是我国自主开发研制的首台用于全球臭氧总量定量测量的探测仪,自发射以来已成功在轨运行近两年.由于TOU发射前辐亮度定标存在偏差,为了得到高精度的产品,TOU必须进行在轨定标.本文介绍了基于辐射传输模式计算对TOU辐亮度进行在轨道定标的方法,定标过程中用于模拟辐亮度计算的臭氧总量由与TOU观测时刻相近的国外臭氧总量探测仪器MetOp/GOME-2提供.文章将在轨定标后TOU的反演结果与AURA/OMI以及地基的产品进行比较,结果表明,用辐射传输模式对TOU辐亮度进行在轨定标的方法是可行的,反演结果能够真实地反映臭氧的时空分布特性,在全球部分地基观测站所处的位置上对TOU, OMI以及地基的臭氧总量进行比较的结果表明,TOU与OMI的相对偏差均方根约为2.52%,TOU与地基以及OMI与地基观测结果之间的相对偏差均方根分别为4.45%和3.89%.     

湖泊水色遥感研究进展

从卫星传感器、大气校正、光学特性测量、生物光学模型及水体辐射传输、水质参数反演方法等方面,系统分析了湖泊水色遥感的发展现状.湖泊水体物质组份的复杂性以及卫星传感器与实际需求的矛盾决定了湖泊水色遥感的难度.目前湖泊水色遥感在一些关键问题上仍没有实质性进步,离水色遥感监测的业务化尚有一段距离.令人欣慰的是,卫星传感器以及水色遥感反演算法的不断发展和进步,让我们看到了胜利的曙光.     

Infrared Radiation in the Mesosphere and Lower Thermosphere: Energetic Effects and Remote Sensing

This paper discusses the formation mechanisms of infrared radiation in the mesosphere and lower thermosphere (MLT), the energetic effects of the radiative absorption/emission processes, and the retrieval of atmospheric parameters from infrared radiation measurements. In the MLT and above, the vibrational levels of the molecules involved in radiative transitions are not in local thermodynamic equilibrium (LTE) with the surrounding medium, and this then requires specific theoretical treatment. The non-LTE models for CO₂, O₃, and H₂O molecules are presented, and the radiative cooling/heating rates estimated for five typical atmospheric scenarios, from polar winter to polar summer, are shown. An optimization strategy for calculating the cooling/heating rates in general circulation models is proposed, and its accuracy is estimated for CO₂. The sensitivity of the atmospheric quantities retrieved from infrared observations made from satellites to the non-LTE model parameters is shown.     

Correlations of mesospheric variability and their relation to the large-scale circulation during polar winter

WINDII data from the Upper Atmosphere Research Satellite show an integrated OH emission rate systematically increasing with decreasing airglow peak altitude. A Spectral Airglow Temperature Imager (SATI) at 74°N shows strong positive correlations between the integrated emission rate and the rotational OH temperature. Taken together, the two correlations are consistent with vertical motions of the mesopause region, over periods from hours to winter to winter. SABER data are consistent with these correlations. The O₂ atmospheric band shows much weaker correlations. The SATI mesospheric temperatures also correlate with Resolute Bay temperatures for the 22.5 km level, a mesosphere–stratosphere relationship.     

A high-accuracy method for simulating the XCO_2 global distribution using GOSAT retrieval data

A high-accuracy surface modeling(HASM)method based on the fundamental theorem of surfaces,is developed to simulate XCO_2 surfaces using the GOSAT retrieval XCO_2 data.Two tests are designed to investigate the simulation accuracy.The first test divides the existing satellite retrieval XCO2 data into training points and testing points,and simulates the XCO2 surface using the training points while computing the simulation error using the testing points.The absolute mean error(MAE)of the testing points is 1.189 ppmv,and the corresponding values of the comparison methods,Ordinary Kriging,IDW,and Spline are1.203,1.301,and 1.355 ppmv,respectively.The second test simulates the XCO_2 surface using all the satellite retrieval points and uses the TCCON(Total Carbon Column Observing Network)site observation values as the ture values.For the six typical TCCON sites,the HASM simulation MAE is 1.688 ppmv,and the satellite retrieval MAE at the same sites is 2.147 ppmv.These results indicate that HASM can successfully simulate XCO_2 surfaces based on satellite retrieval data.     

Large-scale traveling atmospheric disturbances (LSTADs) in the thermosphere inferred from CHAMP,GRACE, and SETA accelerometer data

Densities derived from accelerometer measurements on the GRACE, CHAMP, and Air Force/SETA satellites near 490, 390, and 220 km, respectively, are used to elucidate global-scale characteristics of traveling atmospheric disturbances (TADs). Several characteristics elucidated in numerical simulations are confirmed in this study, namely: (1) propagation speeds increase from the lower thermosphere to the upper thermosphere; (2) propagation to the equator and even into the opposite hemisphere can occur; (3) greater attenuation of TADs occurs during daytime and at higher levels of solar activity (i.e., more wave activity during nighttime and solar minimum), presumably due to the greater influence of ion drag. In addition, we find that the occurrence of significant TAD activity emanating from the auroral regions does not reflect a clear relation with the level of planetary magnetic activity as measured by Kp. There is also evidence of waves originating in the tropics, presumably due to convective sources; to some extent this may contribute to the Kp and solar flux relationships noted above. Further elucidation of local time, season, and altitude dependences of TAD propagation characteristics may be forthcoming from density measurements from the GOCE and Swarm missions.     

Radiation Fog Prediction Using a Simple Numerical Model

—A simple one-dimensional numerical-analytical model was developed by Meyer and Rao (1995) to predict the onset of radiation fog. The model computes radiative cooling and turbulent diffusion of heat and vapor through the lower boundary layer and produces heat and vapor fluxes at the soil–atmosphere interface. The model is designed for Air Force forecasters who have access to a personal computer, an early evening surface observation of the dry bulb and dewpoint temperature, wind speed, the lapse rate in the upper boundary layer, and the previous 24-h precipitation amount. These initial data are used to predict the diurnal variation of the dry bulb and dewpoint temperatures at 10 m above the surface. In accordance with conventional synoptic observing practices, fog is defined as a restriction of the surface visibility generally to less than 1000 m. Fog is assumed to occur in the model predictions when the dewpoint depression falls to less than 1°C. Observations, from several Air Force bases for selected days when fog was observed to occur, were used to test the model. The present model with default parameters appears to predict the onset of fog slightly ahead of its occurrence. Better verification results are expected when site-relevant parameters are used in model predictions.     

A comparison of atmospheric CO2 concentration GOSAT-based observations and model simulations

Satellite observations of atmospheric CO2 are able to truly capture the variation of global and regional CO2 concentration.The model simulations based on atmospheric transport models can also assess variations of atmospheric CO2 concentrations in a continuous space and time,which is one of approaches for qualitatively and quantitatively studying the atmospheric transport mechanism and spatio-temporal variation of atmospheric CO2 in a global scale.Satellite observations and model simulations of CO2 offer us two different approaches to understand the atmospheric CO2.However,the difference between them has not been comprehensively compared and assessed for revealing the global and regional features of atmospheric CO2.In this study,we compared and assessed the spatio-temporal variation of atmospheric CO2 using two datasets of the column-averaged dry air mole fractions of atmospheric CO2(XCO2)in a year from June 2009 to May 2010,respectively from GOSAT retrievals(V02.xx)and from Goddard Earth Observing System-Chemistry(GEOS-Chem),which is a global 3-D chemistry transport model.In addition to the global comparison,we further compared and analyzed the difference of CO2 between the China land region and the United States(US)land region from two datasets,and demonstrated the reasonability and uncertainty of satellite observations and model simulations.The results show that the XCO2 retrieved from GOSAT is globally lower than GEOS-Chem model simulation by 2 ppm on average,which is close to the validation conclusion for GOSAT by ground measures.This difference of XCO2 between the two datasets,however,changes with the different regions.In China land region,the difference is large,from 0.6 to 5.6 ppm,whereas it is 1.6 to 3.7 ppm in the global land region and 1.4 to 2.7 ppm in the US land region.The goodness of fit test between the two datasets is 0.81 in the US land region,which is higher than that in the global land region(0.67)and China land region(0.68).The analysis results further indicate that the inconsistency of CO2concentration between satellite observations and model simulations in China is larger than that in the US and the globe.This inconsistency is related to the GOSAT retrieval error of CO2 caused by the interference among input parameters of satellite retrieval algorithm,and the uncertainty of driving parameters in GEOS-Chem model.     

利用全极化微波辐射计资料反演台风境内海面风场

作为一种新兴的被动遥感技术,全极化微波辐射计不仅可以提供海面风速产品,还可以提供海面风向产品.以往利用全极化微波辐射计观测亮温进行海面风场反演仅在晴空条件下进行,本文通过对观测亮温结合台风区域海面风场的分布特征进行分析,验证了全极化微波辐射计具有在台风等恶劣天气条件下进行海面风场观测的能力.基于敏感性分析实验,确定使用6.8 GHz和10.7 GHz等低频通道组合可进行台风区域内海面风场反演.其中,海面风速反演使用基于统计的多元线性回归算法,同时对海面温度、大气水汽含量、云中液态水含量及降水强度等物理量进行反演计算,为海面风向反演做准备.海面风向反演使用物理统计法进行,借鉴散射计风向反演使用的最大似然估计法.通过在全极化辐射传输前向模型中加入降水对大气透过率的影响、设计第三和第四Stokes通道亮温环境影响修正函数,在实现台风区域内海面风向反演的同时减小了反演误差.通过对“云娜”台风境内海面风场进行数值计算,验证了本文反演算法的可行性,并对反演误差的空间分布特征进行了分析.将2004年各台风过程的海面风场反演结果与散射计风场产品进行对比,海面风速和海面风向反演的均方根误差分别为1.64 m·s^-1和18.02°.     

A high-accuracy method for simulating the XCO<Subscript>2</Subscript> global distribution using GOSAT retrieval data

A high-accuracy surface modeling (HASM) method based on the fundamental theorem of surfaces, is developed to simulate XCO₂ surfaces using the GOSAT retrieval XCO₂ data. Two tests are designed to investigate the simulation accuracy. The first test divides the existing satellite retrieval XCO₂ data into training points and testing points, and simulates the XCO₂ surface using the training points while computing the simulation error using the testing points. The absolute mean error (MAE) of the testing points is 1.189 ppmv, and the corresponding values of the comparison methods, Ordinary Kriging, IDW, and Spline are 1.203, 1.301, and 1.355 ppmv, respectively. The second test simulates the XCO₂ surface using all the satellite retrieval points and uses the TCCON (Total Carbon Column Observing Network) site observation values as the ture values. For the six typical TCCON sites, the HASM simulation MAE is 1.688 ppmv, and the satellite retrieval MAE at the same sites is 2.147 ppmv. These results indicate that HASM can successfully simulate XCO₂ surfaces based on satellite retrieval data.     

重力波诱导OH气辉分布的变化

利用全隐欧拉格式和全球热层-电离层-中间层-电动力学环流耦合模式（TIME GCM） ,本文分析了非线性重力波在向上传播过程中对OH气辉廓线的影响,结果表明,当较小垂直 尺度重力波经过OH气辉发射层时,对其峰值分布有明显的影响,有时会出现双峰现象,说明 非线性重力波传播是引起气辉双峰分布的一个直接原因;重力波在中层顶区域的破碎 在OH气辉分布均有不同程度的表现,这不仅可以解释一些实际的观测,同时也对利用OH气辉 观测分析重力波传播特性有明显的指示意义.      

Cross-Media Models of the Chesapeake Bay Watershed and Airshed

A continuous, deterministic watershed model of the Chesapeake Bay watershed, linked to an atmospheric deposition model is used to examine nutrient loads to the Chesapeake Bay under different management scenarios. The Hydrologic Simulation Program - Fortran, Version 11 simulation code is used at an hourly time-step for ten years of simulation in the watershed. The Regional Acid Deposition Model simulates management options in reducing atmospheric deposition of nitrogen. Nutrient loads are summed over daily periods and used for loading a simulation of the Chesapeake estuary employing the Chesapeake Bay Estuary Model Package. Averaged over the ten-year simulation, loads are compared for scenarios under 1985 conditions, forecasted conditions in the year 2000, and estimated conditions under a limit of technology scenario. Limit of technology loads are a 50%, 64%, and 42% reduction from the 1985 loads in total nitrogen, total phosphorus, and total suspended solids, respectively. Urban loads, which include point source, on-site wastewater disposal systems, combined sewer overflows, and nonpoint source loads have the highest flux of nutrient loads to the Chesapeake, followed by crop land uses.on assignment from NOAA Air Resources Laboratory     

大气阻力引起卫星轨道衰减的数值模拟

本文以德国低轨道卫星CHAMP为例,联合考虑地球扁率和大气阻力摄动的影响,对相应摄动方程进行数值积分,计算轨道根数变化,并进而计算得到卫星空间位置,由此模拟考察大气阻力引起的轨道高度衰减.模拟中使用综合考虑了太阳辐射和磁暴等多种因素影响的最新国际大气标准JB2008模式来计算热层大气密度. 选取CHAMP卫星轨道高度自然衰减（无点火提升卫星高度操作）的2005全年进行模拟;为了考察不同年份阻力系数的可能变化,对2002年1—3月处在较大高度的轨道也进行了模拟.考虑到CHAMP卫星的特殊几何构形及飞行高度的热层温度条件,取阻力系数大于2.8,并在一定范围内变化,以求得模拟与实际轨道衰减符合较好.结果表明,对于2005年,阻力系数为2.91时模拟得到的轨道高度的衰减与实际轨道衰减符合得最好,模拟与实际轨道半长轴全年的标准偏差为81m;在卫星高度稍高的2002年,模拟的最佳阻力系数为3.0;模拟所得最佳阻力系数值比传统使用的值2.2大30%以上.由于在模拟中忽略了高阶保守力分量,所得近/远地点高度没有出现实际轨道所显示的周期性起伏.     

Space- and ground-based CO2 measurements: A review

The climate warming is mainly due to the increase in concentrations of anthropogenic greenhouse gases, of which CO₂ is the most important one responsible for radiative forcing of the climate. In order to reduce the great estimation uncertainty of atmospheric CO₂ concentrations, several CO₂-related satellites have been successfully launched and many future greenhouse gas monitoring missions are planned. In this paper, we review the development of CO₂ retrieval algorithms, spatial interpolation methods and ground observations. The main findings include: 1) current CO₂ retrieval algorithms only partially account for atmospheric scattering effects; 2) the accurate estimation of the vertical profile of greenhouse gas concentrations is a long-term challenge for remote sensing techniques; 3) ground-based observations are too sparse to accurately infer CO₂ concentrations on regional scales; and 4) accuracy is the primary challenge of satellite estimation of CO₂ concentrations. These findings, taken as a whole, point to the need to develop a high accuracy method for simulation of carbon sources and sinks on the basis of the fundamental theorem of Earth’s surface modelling, which is able to efficiently fuse space- and ground-based measurements on the one hand and work with atmospheric transport models on the other hand.     

Reducing the Uncertainties in Direct Aerosol Radiative Forcing

Direct aerosol radiative forcing (DARF) remains a leading contributor to climate prediction uncertainty. To monitor the spatially and temporally varying global atmospheric aerosol load, satellite remote sensing is required. Despite major advances in observing aerosol amount, type, and distribution from space, satellite data alone cannot provide enough quantitative detail, especially about aerosol microphysical properties, to effect the required improvement in estimates of DARF and the anthropogenic component of DARF. However, the combination of space-based and targeted suborbital measurements, when used to constrain climate models, represents an achievable next step likely to provide the needed advancement.