Atmospheric temperature sounding with the Fourier spectrometer

Preliminary results of a space experiment using the IKFS-2 infrared sounder (Meteor-M2 satellite) showed high-quality of measurements of spectra of the outgoing thermal radiation of the atmosphere–surface system and the adequacy of developed IR radiation atmospheric models in the 15-μm carbon gas absorption band used to recover the vertical profiles of the atmospheric temperature. Outgoing radiation spectra measured by IKFS-2 instruments make it possible to restore vertical temperature profiles with errors close to 1K in most of the 0–30 km high-altitude region, except for the lower troposphere and altitudes above 30 km, where these errors are close to 2–3K.     

Determining the accuracy of estimation of the two-dimensional stratospheric temperature field based on satellite measurements of limb radiation in the CO2 15-μm absorption band with high spectral resolution

The problem of reconstructing the temperature distribution along optical paths from satellite measurements of the Earth’s limb radiation in the CO₂ 15-μm absorption band with a high spectral resolution is formulated and analyzed on the basis of numerical experiments performed in accordance with the MIPAS experiment. It is shown that the two-dimensional temperature field can be obtained through the processing of radiation measurements on paths with different target heights provided that spectral channels with essentially different optical thicknesses are used. The error in the stratospheric temperature determination varies from 1.8 to 5.6 K and depends on the target height of the optical path and the distance from the target point. The best horizontal resolution is 73–100 km, and it is achieved for optical paths with a target height of about 18–20 km.     

Comparison between refraction angles measured in the Microlab-1 experiment and calculated on the basis of an atmospheric general circulation model

The differences between the refraction angles measured and calculated for the reanalyses of the European Centre for Medium-Range Weather Forecasts were statistically analyzed on the basis of 64 radio occultation events recorded by the Microlab-1 satellite. It is shown that, for minimum ray heights below 20 km, the main contribution to the differences is made by spatial refractive-index fluctuations neglected by the model. The power spectral density of these fluctuations is mainly concentrated within the vertical wave-number range 0.5–10 rad/km. For heights above 30 km, the deviations are mainly determined by ionospheric disturbances and may vary several times during changes of the site and time of observations. This suggests that the results of satellite radio-occultation sounding of the neutral atmosphere can be used as an indirect quantitative estimate of local discrepancies between the actual field of the refractive index and its values calculated on the basis of a hydrodynamic atmospheric general circulation model.     

Ground-based measurements of total column of hydrogen chloride in the atmosphere near St. Petersburg

We present ground-based spectroscopic measurements of the total hydrogen chloride in the atmosphere of Peterhof near St. Petersburg from April 2009 to March 2012. The well-known computer code SFIT-2 (Zephyr-2) was used to interpret the spectra of the solar IR radiation. The random and systematic errors of total column (TC) HCl measurements did not exceed 3.8 and 4.5%. The seasonal behavior of TC HCl in Peterhof is characterized by the presence of a maximum in March–April and a minimum in October–November. There are also extremely small TC HCl values in January–February. The time behavior obtained for Peterhof agrees well with data from nearest stations in the NDACC international network. The ground-based measurements of the TC HCl were compared with satellite measurements with the help of ACE-FTS and MLS instruments. The direct comparisons of coincident (within a day) and collocated (within 500 km) satellite and ground-based measurements showed a correspondence of results within their total errors.     

Determination of the total ozone content from data of satellite IR Fourier-spectrometer

Examples of retrieval of the total ozone content (TOC) from the spectra of outgoing thermal radiation measured by the IRFS-2 device on the Meteor-M no. 2 meteorological satellite are presented. The technique, developed by the authors and based on an artificial neural network (ANN) approach with the use of TOC measurements by the satellite OMI device, is applied. A comparison of the results with the data of independent TOC measurements has shown their agreement within 2–5% for global ensemble and within 3–6% for separate latitudes and seasons. The errors estimated for IRFS-2 TOC measurements are close to the errors in measurements by a similar IASI device from the MetOp (EUMETSAT) satellite.     

Ground-based measurements of total ozone content by the infrared method

To interpret the ground-based measurements of the spectra of direct solar infrared radiation with the help of a Brucker Fourier-spectrometer, a technique for determining the total ozone content (TOC) was developed and implemented. The TOC was determined using six spectral intervals of an ozone-absorption band of 9.6 μm and the shortwave panel of a carbon-dioxide-absorption band of 15 μm, where the impact of other atmospheric parameters on the measured solar radiation was reduced to a minimum. The potential errors of the infrared method for determining the TOC for the chosen spectral scheme with the influence of measurement errors and vertical profiles of temperature are less than 1% for different signal-to-noise ratios and zenith angles of the sun. We analyzed 269 high-resolution (0.005–0.008 cm^?1) spectra of solar infrared radiation measured in Peterhof over 52 days from March to November, 2009. The resulting values of TOC were compared with the results of independent ground-based TOC measurements in Voeikovo (Main Geophysical Observatory) using a Dobson spectrophotometer and an M-124 ozonometer, as well as with the Ozone Monitoring Instrument (OMI) satellite data. The mean errors between the results of TOC measurements with the help of the three ground-based probes constitute no more than 0.4%. The rms errors between data obtained by the Brucker spectrometer and the given satellite and ground-based probes constitute 3–4%. A comparison between different series of measurements indicated that the upper estimate for the error of TOC measurements by the Brucker spectrometer was 2.5–3% (when the possible spatial and temporal errors in measurements are disregarded). An analysis of the diurnal variations in the TOC measurements for stable atmospheric conditions yields an upper estimate of ～3 DU (around 1%) for the random component of error in TOC measurements by the Brucker spectrometer.     

基于人工神经网络的海水漫射衰减系数的遥感反演方法

利用NOMAD数据集建立了基于人工神经网络的漫射衰减系数Kd490的反演算法。该人工神经网络是3层的反向传输神经网络。其结构为输入层有4个节点,它们分别对应4个波段443,490,555,665 nm的遥感反射比,隐含层有10个节点,输出层1个节点对应于漫衰减系数Kd490。利用另一独立的现场测量数据集(COASTLOOC)印证该反演算法的性能。结果表明,该研究建立的反演算法的性能明显好于业务化SeaWiFS算法,略好于Lee等人的半分析算法。     

On the influence of the 11-year cycle of solar activity on quasi-biennial variations in ozone and temperature in the Canadian sector of the arctic

An analysis of the high-latitude ozone balloon sounding data derived from Canadian stations shows that, in the maximum of the 11-year cycle of solar activity (SA), the ozone content in the lower stratosphere is higher than in the SA minimum and, in the SA maximum, the lower stratosphere is warmer and the troposphere is colder than in the SA minimum. The ozone and temperature responses to the equatorial quasi-biennial oscillation (QBO) in the opposite phases of the 11-year cycle of SA show substantial differences: in the SA maximum, the QBO effects in the ozone and temperature cover a wider range of heights, the maxima of the effects manifest themselves at 5–10 km higher, and their amplitudes exceed the amplitudes of the effects in the SA minimum. The results indicate that the QBO is one of the “conductors” of the influence of the 11-year SA cycle in the Canadian sector of the Arctic.     

利用西北印度洋船测数据评估基于卫星的海表面温度

本文描述了一次夏季在西北印度洋进行的调查船水文测量,用船测数据评估卫星海面表温度,并寻找影响海表面温度误差的主要因素。我们考虑了两种卫星数据,第一种是微波遥感产品——热带降雨测量任务微波成像仪TMI数据,另外一种是融合了微波,红外线,以及少部分观测数据的融合数据产品——可处理海表温度和海冰分析OSTIA数据。结果表明融合数据的日平均海表面温度的平均误差和均方根误差都比微波遥感小。这一结果证明了融合红外线遥感,微波遥感以及观测数据来提高海表面温度数据质量的必要性。此外,我们分析了海表面温度误差与各项水文参数之间的相关关系,包括风速,大气温度,想对湿度,大气压力,能见度。结果表明风速与TMI海表面温度误差的相关系数最大。而大气温度是影响OSTIA海表面温度误差最重要的因素;与此同时,想对湿度与海表面温度误差的相关系数也很高。     

Space and time variations in the fine structure of the upper atmosphere according to acoustic sounding data

The results of studying variations in the fine layered structure of the upper atmosphere (heights of 20–140 km) according to data obtained from acoustic sounding within the range of infrasonic waves are given. The sources of infrasounds were surface explosions equivalent to 10 kg to 70 t of TNT. These explosions were set off in different seasons in different regions of Russia. Experimental data obtained in 1981–2011 have been analyzed. It has been found that the fine structure in the form of vertically distributed layered formations occurs in the upper atmosphere in all seasons. Moreover, the vertical distribution of both air-temperature and wind-velocity inhomogeneities in the upper atmosphere may be invariable over a time interval of no less than several hours. It has also been found that, throughout the entire atmospheric thickness from the stratopause to the lower thermosphere heights (up to 140 km), the instantaneous height distribution of layered air-temperature and wind-velocity inhomogeneities may remain almost unchanged during a time interval of no less than 20 min.     

人工神经网络在南海近海面气温反演中的应用研究

基于人工神经网络方法,利用海面水温、海面风速以及海面气压反演南海近海面气温,采用的基础数据集是国际综合海洋-大气数据集(International Comprehensive Ocean-Atmosphere Data Set,2.4 Release,ICOADS2.4)1981—2008年的观测资料,其中1981—2000年的观测资料用来建立模型,2001—2008年的观测资料用来进行模型检验。采用的人工神经网络方法是引入动量因子并采用批处理梯度下降法的BP(Back propagation)算法。试验结果表明,基于人工神经网络建立的近海面气温反演方法明显优于多元线性回归方法,尤其是在春季和冬季,海面水温、海面风速以及海面气压与近海面气温之间存在较强的非线性关系,人工神经网络的优势更加明显。总体而言,人工神经网络在各月的反演效果较均衡,均方根误差介于1.5—1.8℃之间,平均绝对误差为1.1—1.3℃。     

Forecasting of chlorophyll-a concentrations in South San Francisco Bay using five different models

Accurate and reliable eutrophication level forecasting models are necessary for characterizing complicated water quality processes in bays. In this study, the ability of coupled discrete wavelet transform (DWT) with artificial neural network (ANN) and multi linear regression (MLR) (WANN and WMLR), ANN, MLR and genetic algorithm-support vector regression (GA-SVR) models for chlorophyll-a level forecasting applications were considered. The data used to develop and validate the models were monthly chlorophyll-a (Chl-a) data recorded from January 1994 to December 2013 were obtained from the NO.36 station located in the South San Francisco bay, USA. In the proposed WANN and WMLR models, the observed time series of Chl-a were decomposed to sub time series at different scales by DWT. Afterwards, the sub time series were used as input data to the ANN and MLR systems to predict the 1 month ahead Chl-a. Also the genetic algorithm was linked to SVR models to search for the optimal SVR parameters. The relative performance of the proposed models was compared together and the results showed that the WANN models were found to provide more accurate monthly Chl-a forecasts compared to the other models. The determination coefficient was 0.87, −0.04, 0.31, −2.36 and 0.24 for the WANN, WMLR, ANN, MLR and GA-SVR models, respectively. In addition, the WANN model predicted extreme Chl-a values precisely. The results indicate that the WANN models are a promising new method for eutrophication level forecasting in bays such as those found in South San Francisco Bay.     

接收机自主完好性监测算法及其性能分析

完好性是卫星导航系统的重要性能参数,接收机自主完好性监测作为用户端的完好性监测方法具有低成本、实施方便的优势。基于统计理论,给出RAIM算法统计检测量的设计方法,推导了阈值的确定方法及RAIM可用性判定方法。对一天中2880个采样时刻的RAIM性能进行仿真分析,结果表明,RAIM算法对于固定伪距误差的故障和慢变故障有良好的监测效果,排除故障星之后的定位误差可以保持在正常的水平。     

Interhemispheric distinctions between the polar vortex positions in the winter stratosphere and mesosphere from measurements with a SABER instrument aboard the TIMED satellite

Distinctions between the longitudinal structures of circulation in the stratosphere and mesosphere/lower thermosphere of the Northern and Southern hemispheres are investigated on the basis of the temperature and geopotential distributions obtained with a SABER instrument (TIMED satellite) in the months of February and August in 2002–2005. The positions of the winter cyclone and polar vortex at stratospheric and mesospheric heights in 2002–2005 are compared to the climatic data over 1978–1998. At stratospheric heights, the mean position of the polar vortex’s center over several years changed insignificantly during the specified years (several degrees in latitude and longitude) in both the Southern and Northern hemispheres. At mesosphere/lower thermosphere heights, the polar vortex occupies the same position in the Southern Hemisphere each year during 2002–2005, and this position agrees with the estimates for 1996–1997. Parameters of stationary planetary waves with the zonal wave number 1 (SPW1) in the fields of temperature, geopotential, and wind are calculated from data on the temperature and geopotential. The height profiles of SPW1 amplitudes and phases calculated from the SABER instrument data for August in the Southern Hemisphere are in good agreement with the profiles of amplitudes and phases obtained from the direct wind measurements with HRDI and WINDII instruments. A strong interannual variability of SPW1 parameters is observed in the Northern Hemisphere. The calculation of the Eliassen-Palm flux and its divergence has shown that SPW1 penetrates into the mesosphere mainly from the stratosphere and slows down the zonal mean flux. However, in the Southern Hemisphere, there is a regular additional SPW1 source with the center at a height of about 65 km and a latitude of 55°S. Such a SPW1 source is, on average, absent in the Northern Hemisphere during 2002–2005; however, in some years (for example, in February 2004), its existence is possible.     

Experimental study of the angular method for the determination of the sea surface temperature from space in the 8–12 μm window

The structure of the field of outgoing into space radiation for the 8–12 m spectral interval is studied using the data of satellite observations of the oceans. The regularity found is employed to substantiate the angular method for the sea surface temperature (SST) reconstruction. The band of the angles of view is determined in which the error of the SST reconstructon does not exceed 0.3°C with the assigned error of the satellite measurements of radiation temperatures of 0.05°C.UDK 551.507.362.2Translated by Mikhail M. Trufanov.     

Large-Scale Errors in ERS Altimeter Data

A method is described for mapping time-uncorrelated large-scale errors in satellite altimeter sea surface heights. Standard deviations of differences between pairs of successive measurements at track crossovers are computed, and the functional dependence of these deviations on absolute time difference is used to estimate the errors of individual measurements. This is first applied to all of ERS-1,2 altimeter data in the Pacific Ocean, yielding average errors of 3.2 cm in the deep ocean (>1 km) and 4.7 cm in the shallow seas (<1 km). The procedure is repeated for variable latitude bands, each with a full range of possible time differences, yielding a meridional profile of computed errors, ranging from 2.6 cm near the Antarctic continent (67–60S) and South Subtropical regions (25–5S) to 3.5 cm in the Antarctic Circumpolar Current (60–45S) and the Northern Hemisphere Subtropical and Subpolar Gyres. Finally, coarse-resolution maps of these errors are produced by subdividing the Pacific Ocean into latitude-longitude bins, each large enough to contain a sufficient number of samples for the functional fits. The larger errors are in Northwest and Subtropical Pacific, especially in South China Sea (4.3 to 4.5 cm) and off northern Australia (5.4 cm), while the smaller errors (2.5 to 3 cm) are in Northeast Pacific, central Tropical Pacific and near Antarctica in Southeast Pacific Ocean. These are lower bounds on altimeter errors, as they do not include contributions from time-correlated errors. We find that the computed error fields are not correlated with sea level standard deviations, thus disproving the notion that altimeter error variance can be scaled with the variance of sea surface height data.     

Height-latitude structure of the vertical component of the migrating semidiurnal tide in the upper mesosphere and lower thermosphere region (80–100 km)

The height-latitude distributions of parameters of the vertical wind component of the semidiurnal tide were calculated for the mesosphere and lower thermosphere (MLT) region (80–100 km) on the basis of empirical height-latitude distributions of the monthly mean parameters of variations in the horizontal wind component of the migrating semidiurnal tide. The constructed distributions are compared with the results of a numerical modeling of the migrating semidiurnal tide with the aid of a model of global circulation in the middle and upper atmosphere, as well as with the parameters of semidiurnal temperature variations obtained from the data of satellite measurements. It is shown that different models yield the distributions of parameters of semidiurnal variations, which agree within the errors of their values. The presence of high-latitude regions of local maximal amplitudes is a specific feature of the distributions of parameters of semidiurnal variations in the vertical wind constructed in the course of this work. On the whole, at heights of about 90 km and higher, semidiurnal variations in the vertical wind exceed the prevailing vertical wind in amplitude.     

An offshore eddy in the California current system part II: Surface manifestation

Ship and satellite observations taken over the last thirty years show that mesoscale patterns of sea surface temperature (SST) in the California Current System are consistently found throughout the year and usually occur in approximately the same geographical locations. Typically, these patterns are more pronounced in fall/winter than in spring/summer. The temporal and spatial characteristics of these persistent feature were examined with satellite infrared (IR) measurements during winter 1980–1981. In January 1981, a ship surveyed the vertical structure of several physical, chemical, and biological parameters beneath one of these SST features centered near 32°N, 124°W. The surface IR pattern had a length scale of 200 km and a time scale of about 100 days. It disintegrated following the first two storms of the winter season. Motion studies of the pattern in late October indicated an anticyclonic rotation with maximum velocities of 50 cm s^?1 at 50 km from the axis of rotation. As a unit, the pattern advected southward with an average speed of 1 cm s^?1. Thermal fronts, determined from the satellite imagery, were strongest (0.4°C km^?1) along the rim of the pattern and were advected anticyclonically with the pattern; their length scales were 20–30 km in the along-front direction and less than 10 km wide. The hydrographic data revealed a three-layer structure beneath the surface pattern; a 75 m deep surface layer, a cold-core region from 75 to 200 m depth, and a warm-core eddy extending from 250 to 1450 m. The anticyclonic motion of the surface layer was caused by a geostrophic adjustment to the surface dynamic height anomaly produced by the subsurface warm-core eddy. The IR pattern observed from space reflects the horizontal structure of the surface layer and is consistent with a theoretical model of a mean horizontal SST gradient perturbed by a subsurface density anomaly. Ship of opportunity SST observations collected by the National Marine Fisheries are shown to resolve mesoscale patterns. For December 1980, the SST pattern near 32°N, 124°W represented a 2°C warm anomaly compared with the 20-year mean monthly SST pattern.     

卫星遥感业务系统海表温度误差控制方法

提高卫星遥感海表温度的反演精度是各种反演模型追求的目标,也是遥感系统业务化应用的关键.据相关文献报道,在晴空无云的条件下遥感海表温度的精度达到了0.5℃,但考虑到影响海表温度反演精度的多种因素,在遥感业务系统真正实现SST精度在1℃以内是非常困难的.在北太平洋渔场速报制作系统中,对遥感海表温度与船测温度误差统计显示均方根误差达到5.71℃,匹配点误差分布显示存在大量较大的负误差值,最大的为-17.2℃,遥感温度图也反映出存在片状温度低值区,这些区域很可能被错误地当作冷涡或冷锋区,严重干扰渔情分析,这些异常的温度误差很难通过海表温度反演模式和云检测技术来消除.采用一种标准海表温度参考图用于温度误差控制技术,可有效地检测温度反演异常值,将均方根值从5.71℃降低到1.75℃,如果采用2℃阈值控制计算均方根值,则海表温度精度达到0.785℃.该方法基本消除了遥感海表温度的低值现象,明显提高了遥感海表温度的精度,并已成功地应用于北太平洋渔区的海况速报产品制作中.     

On the behavior of stratospheric ozone in the western Arctic during the 2003–2004 winter and spring

We present the results of simultaneous measurements of variations in the ozone layer in the north-western Arctic conducted with the help of different instruments. It is shown that, in the winter of 2003–2004, when the stratosphere was relatively warm and the wave activity was high, spatial inhomogeneities in the field of ozone distribution were observed. For April 2004, we detect a decrease in the ozone content in the range of heights between 25 and 40 km. This decrease was recorded simultaneously by the HALOE, SAGE, and POAM satellite instruments.