Science objectives of the ozone monitoring instrument

The Ozone Monitoring Instrument (OMI) flies on NASA's Earth Observing System AURA satellite, launched in July 2004. OMI is an ultraviolet/visible (UV/VIS) nadir solar backscatter spectrometer, which provides nearly global coverage in one day, with a spatial resolution of 13 km/spl times/24 km. Trace gases measured include O/sub 3/, NO/sub 2/, SO/sub 2/, HCHO, BrO, and OClO. In addition OMI measures aerosol characteristics, cloud top heights and cloud coverage, and UV irradiance at the surface. OMI's unique capabilities for measuring important trace gases with daily global coverage and a small footprint will make a major contribution to our understanding of stratospheric and tropospheric chemistry and climate change along with Aura's other three instruments. OMI's high spatial resolution enables detection of air pollution at urban scales. Total Ozone Mapping Spectrometer and differential optical absorption spectroscopy heritage algorithms, as well as new ones developed by the international (Dutch, Finnish, and U.S.) OMI science team, are used to derive OMI's advanced backscatter data products. In addition to providing data for Aura's prime objectives, OMI will provide near-real-time data for operational agencies in Europe and the U.S. Examples of OMI's unique capabilities are presented in this paper.     

Band residual difference algorithm for retrieval of SO/sub 2/ from the aura ozone monitoring instrument (OMI)

The Ozone Monitoring Instrument (OMI) on EOS/Aura offers unprecedented spatial and spectral resolution, coupled with global coverage, for space-based UV measurements of sulfur dioxide (SO/sub 2/). This paper describes an OMI SO/sub 2/ algorithm (the band residual difference) that uses calibrated residuals at SO/sub 2/ absorption band centers produced by the NASA operational ozone algorithm (OMTO3). By using optimum wavelengths for retrieval of SO/sub 2/, the retrieval sensitivity is improved over NASA predecessor Total Ozone Mapping Spectrometer (TOMS) by factors of 10 to 20, depending on location. The ground footprint of OMI is eight times smaller than TOMS. These factors produce two orders of magnitude improvement in the minimum detectable mass of SO/sub 2/. Thus, the diffuse boundaries of volcanic clouds can be imaged better and the clouds can be tracked longer. More significantly, the improved sensitivity now permits daily global measurement of passive volcanic degassing of SO/sub 2/ and of heavy anthropogenic SO/sub 2/ pollution to provide new information on the relative importance of these sources for climate studies.     

The ozone monitoring instrument

The Ozone Monitoring Instrument (OMI) flies on the National Aeronautics and Space Administration's Earth Observing System Aura satellite launched in July 2004. OMI is a ultraviolet/visible (UV/VIS) nadir solar backscatter spectrometer, which provides nearly global coverage in one day with a spatial resolution of 13 km/spl times/24 km. Trace gases measured include O/sub 3/, NO/sub 2/, SO/sub 2/, HCHO, BrO, and OClO. In addition, OMI will measure aerosol characteristics, cloud top heights, and UV irradiance at the surface. OMI's unique capabilities for measuring important trace gases with a small footprint and daily global coverage will be a major contribution to our understanding of stratospheric and tropospheric chemistry and climate change. OMI's high spatial resolution is unprecedented and will enable detection of air pollution on urban scale resolution. In this paper, the instrument and its performance will be discussed.     

2006-2014年南京都市圈对流层NO2时空变化特征及污染源分析

基于OMI(Ozone Monitoring Instrument, OMI)卫星传感器监测得到的2006年1月-2014年12月南京都市圈对流层NO2柱浓度数据和土地利用类型数据,利用余弦曲线函数和HYSPLIT后向轨迹模型,分析了研究区对流层NO2时空分布特征以及污染物的来源。研究发现,2006-2014年南京都市圈对流层NO2柱浓度呈现出逐年增长的趋势和冬高夏低的季节变化特征;研究区对流层NO2污染物主要来自两个方面：大气气流的输送作用影响了研究区对流层NO2季节性变化;不同的土地利用类型影响了南京都市圈的对流层NO2柱浓度。     

基于MAX-DOAS 的淮北地区NO2柱浓度观测研究

基于多轴差分吸收光谱技术 (MAX-DOAS) 反演 NO2 柱浓度的方法, 构建了相应的地基 MAX-DOAS 系统, 开 展了 NO2 柱浓度变化特征的观测。反演中选取天顶方向的光谱作为参考光谱, 通过非线性最小二乘法反演出 NO2 斜柱浓度 (SCD), 结合不同观测方向的斜柱浓度得到 NO2 差分斜柱浓度 (dSCD), 再利用几何近似法得到大气质量 因子 (AMF), 最终获取 NO2 垂直柱浓度 (VCD)。于 2019 年 6 月至 2020 年 5 月在淮北地区开展了为期一年的外场 实验, 研究结果表明淮北地区 NO2 VCD的月均值在观测期间内呈现倒“U”型变化, 在 12 月份达到最高值 2.13×1016 molecules·cm−2, 在 8 月份达到最低值 5.23×1015 molecules·cm−2。将 MAX-DOAS 观测结果的日均值与 OMI 卫星 (云 系数分别为 0 < FeC ≤ 0.1 和 0 < FeC ≤ 0.3) 测量结果进行对比, 发现两者具有较好的相关性 (R2 = 0.88, R2 = 0.90), 表明 MAX-DOAS 不仅可以准确反演出 NO2 垂直柱浓度, 还可以验证卫星数据。     

基于MAX-DOAS观测的淮北冬季NO2变化特征

基于2018年12月8日~12月31日淮北地区多轴差分吸收光谱技术(MAX-DOAS)获得的太阳散射光谱观测数据,反演了该地区NO2对流层柱浓度, 并分析了冬季不同天气下NO$_2$浓度日变化特征。观测结果表明NO2浓度高值出现在12月18日~12月27日期间,日均值最大值6.83×10¹⁶ molecules/cm²出现在12月27日,约为日均值最低值的2.9倍。结合风场轨迹模型研究了不同大气条件下的风场,发现在NO2浓度较低时段主要为 偏北风场, NO2浓度高值时段偏南风场增加,表明城区产生的污染向观测区域进行了输送。将MAX-DOAS结果与OMI卫星结果进行了 对比,发现两者具有较好的一致性(R²=0.88)。     

基于OMI卫星数据结合车载DOAS技术修正的NOx排放通量估算

与搭载在EOS AURA卫星上的OMI（Ozone Monitoring Instrument）探测器相比,由车载被动差分吸收光谱（differential optical absorption spectroscopy,DOAS）技术获得的NO2柱浓度数据空间分辨率更高,因而能够更准确的反映出NO2时空分布情况,利用OMI NO2 Level2数据产品重构2013年6月石家庄及周边区域的NO2柱浓度分布,结合风场数据分析NO2柱浓度沿风场方向的空间分布,同时,使用车载被动DOAS系统对西南通道即石家庄-保定-北京路段进行走航观测,获取车载DOAS NO2柱浓度分布数据,使用指数修正高斯（exponentially-modified Gaussian,EMG）拟合方式,分别拟合OMI NO2 数据和经过地基DOAS数据修正后的OMI NO2 数据得到NOx排放通量分别为195.8 mol/s、160.6 mol/s。经过地基DOAS数据修正的NOx排放量小于卫星估算值,可能是由于卫星的空间分辨率较低导致的。     

基于MAX-DOAS的对流层NO2和气溶胶光学厚度遥测反演

随着全球工业化速度加快和人口的增多,大气环境问题日益突出,NO2和气溶胶在大气化学中扮演着重要的角色。地基多轴差分吸收光谱技术（MAX-DOAS）基于被动DOAS原理,近年来已成功应用于大气痕量气体柱浓度和气溶胶光学厚度（AOD）测量方面。本文基于被动DOAS算法对合肥秸秆燃烧期间NO2柱浓度以及气溶胶光学厚度进行了观测,并把对流层柱浓度和臭氧监测仪(Ozone Monitoring Instrument, OMI)结果进行对比;测量的气溶胶光学厚度和太阳光度计（CE318）进行了对比。结果表明,MAX-DOAS测量结果要高于卫星值,11月6日MAX-DOAS测量NO2柱浓度日均值为OMI的1.9倍;二者在无云条件下一致性较好;MAX-DOAS反演AOD和太阳光度计结果相关性在0.9以上。     

Extension of GPM dual-frequency iterative retrieval method with DSD-profile constraint

A new Dual-Frequency Precipitation Radar (DPR) will be included on the Global Precipitation Measurement (GPM) core satellite which will succeed the highly successful Tropical Rainfall Measuring Mission satellite launched in 1997. New dual-frequency drop-size distribution (DSD) and rain-rate estimation algorithms are being developed to take advantage of the enhanced capabilities of the DPR. It has been shown previously that a backward-iteration algorithm can be embedded within a single-loop feedback model to retrieve the rain rate. However, the single-loop model is unable to correctly estimate DSD profiles for a significant portion of global median-volume-diameter, D/sub o/, and normalized DSD intercept parameter, N/sub w/, combinations in rain because of a multiple-value solution space. For the remaining D/sub o/,N/sub w/ pairs, another retrieval method is necessary. This paper proposes a dual-loop model, in which the intercept parameter, N/sub w/, of the DSD is constrained in its vertical profile, to guide the algorithm to correct convergence. This allows an additional constraint on the DSD values estimated by the iterative algorithm and helps to retrieve correct DSD values in the regions where the iterative approach alone fails. To demonstrate feasibility of the proposed method, three test cases representative of many DSD and profile combinations are discussed. The first case is a constant vertical profile of the DSD parameters. The second case examines linear variation of the DSD parameters, and the third case examines how measurement error affects the retrieval process. In each case, the proposed constraint on the intercept parameter is implemented, and the results are discussed. Using the constraint, the dual-loop algorithm is able to retrieve reasonable values for the DSDs and rain-rate profiles and extend the convergence region of the algorithm.     

基于MAX-DOAS的大气对流层SO2垂直柱浓度遥测

基于多轴差分吸收光谱技术（MAX-DOAS）获得了对流层SO2垂直柱浓度。采用不同参考谱和不同波段来获得SO2差分斜柱浓度,通过对比发现,当圈天顶光谱作为参考谱的反演误差最小,且全天相对稳定波动小,误差小于5%。通过六个波段的对比选取了最优反演波段为307.5~315 nm。结合地面气象数据对2015年10月14日~18日的污染过程进行了研究,数据分析表明风速和风向是影响监测点SO2浓度的两个重要因素,城市和电厂产生的SO2会在东风和南风的影响下向监测点输送。通过研究表明,MAX-DOAS能够准确反演大气对流层SO2垂直柱浓度信息,对于探究城市大气对流层SO2垂直柱浓度、卫星校验、模型校验以及污染输送的研究具有重要意义。     

基于多轴差分吸收光谱技术的对流层HCHO柱浓度测量研究

HCHO是城市大气污染物中的重要组分.采用多轴差分吸收光谱仪(MAX-DOAS)于2008年夏季对北京上空对流层HCHO斜柱浓度进行了测量,研究了HCHO差分吸收光谱处理算法,考虑了温度和I0效应对气体吸收截面的影响,并对大气Ring效应进行了校正.采用几何近似的方法计算了对流层大气质量因子,并将HCHO斜柱浓度转换成垂直柱浓度,得到了实验期间对流层HCHO的垂直柱浓度时间序列,并且HCHO垂直柱浓度早晚比较低,约在中午最高. MAX-DOAS HCHO垂直柱浓度与GOME-2卫星和SCIAMACHY卫星结果具有较好的相关性.     

基于EMI观测的珠三角地区对流层NO2柱浓度时空变化特征分析

珠三角城市群作为我国最具发展活力的都市经济圈之一,近年来经济发展势头迅猛,但与此同时,珠三角地区大气污染问题也引起了广泛关注.在众多大气污染监测手段中,卫星遥感方法具有观测范围广、观测种类多、可长期连续观测、成本低等优点.EMI(Environmental trace gases monitoring instrume...     

Overview of the EOS aura mission

Aura, the last of the large Earth Observing System observatories, was launched on July 15, 2004. Aura is designed to make comprehensive stratospheric and tropospheric composition measurements from its four instruments, the High Resolution Dynamics Limb Sounder (HIRDLS), the Microwave Limb Sounder (MLS), the Ozone Monitoring Instrument (OMI), and the Tropospheric Emission Spectrometer (TES). With the exception of HIRDLS, all of the instruments are performing as expected, and HIRDLS will likely be able to deliver most of their planned data products. We summarize the mission, instruments, and synergies in this paper.     

EMI 南极臭氧柱总量反演研究

利用差分吸收光谱技术 (DOAS) 反演了我国首个星载大气痕量气体差分吸收光谱仪 (EMI) 的臭氧斜柱浓度 (SCD), 通过 SCIATRAN 辐射传输模型建立了大气质量因子 (AMF) 的查找表, 最终得到 EMI 的臭氧垂直柱浓度 (即 臭氧柱总量)。将 EMI、 OMI 和 TROPOMI 于 2018 年 11 月 2 日获得的南极区域臭氧柱总量进行了对比分析, 三者 均观测到南极中高纬度 (30◦ S∼70◦ S) 的臭氧高值区域与南极内陆 (75◦ S∼90◦ S) 的臭氧低值区域, 且 EMI 与 OMI、 TROPOMI 的臭氧柱总量相关性 (R2) 分别为 0.977 和 0.979。进一步将 EMI 反演的臭氧柱总量与南极长城站 (62.22 S, 58.96 W) 地基天顶散射光差分吸收光谱仪 (ZSL-DOAS) 反演的臭氧柱总量进行对比, 二者相关性 (R2) 为 0.926。     

直接测风激光雷达频率跟踪技术及对流层平流层大气风场观测

为了实现高精度连续探测对流层和平流层大气风场,搭建了一台直接测风激光雷达系统对对流层和平流层大气风场进行探测。该系统基于双边缘法布里-珀罗标准具的瑞利散射多普勒测风原理,使用转台式探测结构,通过频率跟踪的手段对频率漂移进行跟踪,确保测风的精度。实验结果表明,该系统对对流层和平流层大气风场探测效果良好,频率跟踪的范围为±50 MHz,可以大大减小频率漂移带来的风速误差。经过系统的稳定运行和长时间的观测,在40 km处测得的径向风速随机误差为8 m/s。径向风速合成为水平风速后,随机误差在38 km处最大为10 m/s左右。该系统白天探测高度为25 km,夜晚探测高度为38 km。与探空数据对比,风速误差均小于10 m/s,其中风速误差在±5 m/s的范围内的数据量约占75.8%,探测的风向误差与探空气球的趋势基本一致,误差范围在10°～20°之间,在15°范围内的数据量约占58.6%。将实测数据与探空数据进行统计分析,结果具有良好的一致性。该系统可以为对流层和平流层大气风场的探测提供数据支撑。     

MIR measurements of atmospheric water vapor profiles

Three subjects related to atmospheric water vapor profiling using the 183.3 GHz absorption line are discussed. First, data acquired by an airborne millimeter-wave imaging radiometer (MIR) over ocean surface in the western Pacific are used to estimate three-dimensional (3D) distribution of atmospheric water vapor. The instrument's radiometric measurements with mixed vertical and horizontal polarizations require modifications to the retrieval algorithm used in the past. It is demonstrated that, after the modifications, the new algorithm can provide adequate retrieval of water vapor profiles, even though the measured data are of mixed polarizations. Next, the retrieved profiles, in terms of water vapor mixing ratio ρ (g/kg), are compared with those measured in near concurrence by dropsondes from a research aircraft in the western Pacific and by a ground-based Raman lidar at Wallops Island, Virginia. The ratio of the standard deviation to the mean ρ is found to be 0.12 at 0.25 km altitude and gradually degraded to 0.67 at the highest altitude of the retrieval of 10.25 km. Finally, the effect of the “initial guess” relative humidity profile on the final retrieved product is analyzed with respect to the condition for the convergent retrieval. It is found that the effect is minimal if the initial profile is not unrealistically different from the true one. If the initial profile is very different from the true one, the final retrieved product could be subject to a substantial error. Tightening of the convergent condition in the retrieval helped reduce magnitude of the error, but not remove it totally. It is concluded that an initial profile based on climatology is likely to provide most reliable retrieval results     

利用 IASI资料反演平流层大气温度

红外大气探测干涉分光仪(Infrared Atmospheric Sounding Interferometer, IASI)能够获取平流层的大气温度廓线,而且由其 提取的大气温度扰动信息可用于平流层的重力波特征分析。基于神经网络方法,利用典型 大气廓线库和大气辐射传输模式建立了由IASI反演25～60 km高度范围内的平流层大气温度廓 线的算式,并结合再分析资料对反演结果进行了检验。模拟试验结果表明,平流层大气 温度反演的偏差主要在0 K附近且不超过1 K,均方根误差处在2～6 K之间,且50～5 hPa之间的均方 根误差在3 K以内。对比验证结果表明,本文的平流层大气温度反演与欧洲中期天气预报中心(European Centre for Medium-range Weather Forecasts, ECMWF)的再分析资料在总体上具有可比性,而且反演速度更快,覆盖的区域更完整。     

被动多轴差分吸收光谱技术监测O4斜柱浓度误差修正方法研究

O₄斜柱浓度的准确获取,对气溶胶廓线反演具有重要意义。介绍了基于被动多轴差分吸收光谱仪（MAX-DOAS）监测O₄斜柱浓度的误差修正方法,用于准确获取O₄斜柱浓度。通过对比30°仰角O₄斜柱浓度MAX-DOAS测量结果和大气辐射传输模型模拟结果,获得修正系数,利用修正系数修正各个角度的斜柱浓度值,消除O₄吸收截面不准确造成的反演结果误差,提高了O₄斜柱浓度精度。研究方法应用于合肥地区O₄斜柱浓度的准确监测,为下一步气溶胶廓线精确反演提供了数据支持。     

The determination of surface salinity with the European SMOS space mission

The European Space Agency Soil Moisture and Ocean Salinity (SMOS) mission aims at obtaining global maps of soil moisture and sea surface salinity from space for large-scale and climatic studies. It uses an L-band (1400-1427 MHz) Microwave Interferometric Radiometer by Aperture Synthesis to measure brightness temperature of the earth's surface at horizontal and vertical polarizations (T/sub h/ and T/sub v/). These two parameters will be used together to retrieve the geophysical parameters. The retrieval of salinity is a complex process that requires the knowledge of other environmental information and an accurate processing of the radiometer measurements. Here, we present recent results obtained from several studies and field experiments that were part of the SMOS mission, and highlight the issues still to be solved.     

Modeling of optical waveguide poling and thermally stimulated discharge (TSD) charge and current densities for guest/host electro-optic polymers

A charge density and current density model of a waveguide system has been developed to explore the effects of electric field electrode poling. An optical waveguide is modeled during poling by considering the dielectric charge distribution, polarization charge distribution, and conduction charge generated by the poling field. The charge distributions are the source of poling current densities. The model shows that boundary charge current density and polarization current density are the major source of currents measured during poling and thermally stimulated discharge measurements. Charge distributions provide insight into the poling mechanisms and are directly related to E/sub A/ and /spl alpha//sub r/. Initial comparisons with experimental data show excellent correlation to the model results.