Decadal variability of tropical Pacific temperature in relation to solar cycles

We use the 8-year long satellite temperature data (2002–2010) from Atmospheric InfraRed Sounder (AIRS) and Atmospheric Microwave Sounding Unit (AMSU) on the Aqua satellite to identify temperature trends in the troposphere and low stratosphere over the Niño 3.4 region of the Tropical Pacific Ocean in the most recent 11-year solar cycle. Employing more extended sea surface temperature (SST) data for five solar cycles (1950–2009) in this region we show that the satellite trends reflect a typical decrease of the sea surface temperature (SST) in the Niño 3.4 region in the declining phase of the solar cycle. The magnitude of the SST decrease depends on the solar cycle and ranges between 0.07 K/yr and 0.27 K/yr for the last five solar cycles.     

Generalised variational assimilation of cloud-affected brightness temperature using simulated hyper-spectral atmospheric infrared sounder data

Assimilated channel brightness temperature data from infrared sounders accounting for cloud effects have a positive effect on weather forecasting, especially in weather-sensitive areas. When cloud effects are included, the channel brightness temperature deviations follow a non-Gaussian distribution. However, classical variational data assimilation follows a Gaussian distribution. When processing the cloud-affected brightness temperature, useful data are lost through the cloud detection process, thus assimilating some channel brightness temperatures with weight function peaks above the cloud top. Furthermore, strict quality control of brightness temperature removes outliers. By adopting the generalised variational assimilation method, which assumes that errors follow a non-Gaussian distribution, this paper assimilates the cloud-affected brightness temperature using simulated data for the hyper-spectral atmospheric infrared sounder (AIRS). A channel set is formed by dynamically selecting AIRS channels. The experiments for retrieving temperature and humidity data demonstrate that the generalised variational assimilated cloud-affected brightness temperature method performs better than the classical method.     

Vertical mass and moisture structure from TIROS-N

During the First Global GARP Experiment (FGGE), global determinations of mass and moisture were made from TIROS-N (and NOAA-6) infrared and microwave sounding radiance measurements. At NESS in Washington, the meteorological data were produced operationally with a horizontal resolution of 250 km for inclusion in the FGGE level II-b data sets intended for application to large scale numerical analysis and prediction models. High horizontal resolution (50 km) sounding data sets are being produced by NESS and the Space Science and Engineering Center at the University of Wisconsin and at the NASA/Goddard Space Flight Center for special case studies of the “Special Observing Periods” of FGGE.Results are presented to display the characteristics of the sounding data at different resolutions. For the low horizontal resolution data, an evaluation is shown by comparisons of global analyses made only from satellite soundings over land and sea, and those made operationally by the National Meteorological Center, which excluded satellite sounding data over continental areas, but included all conventional data sources. For the high horizontal resolution sounding data, results are presented to demonstrate the delineation of small scale temperature and moisture features which are consistent with the meteorological processes involved.     

面向装备RUL预测的平行仿真技术

装备平行仿真是系统建模与仿真领域的新兴仿真技术,已经成为研究热点。在装备维修保障领域中,分析了装备剩余寿命（RUL）预测存在的突出问题,即模型参数固定、不具备自适应演化能力,成为阻碍实现装备剩余寿命自适应预测的首要因素。结合装备平行仿真理论,在建模分析的基础上提出了面向装备剩余寿命预测的平行仿真框架,该框架以Wiener状态空间模型为基础仿真模型,在动态注入的装备退化观测数据驱动下,利用期望最大化（EM）算法在线更新模型参数,并利用卡尔曼滤波（KF）算法实现仿真输出数据与观测数据的同化（DA）,从而实现仿真模型动态演化,使得仿真输出不断逼近装备真实退化状态,为准确预测剩余寿命提供高逼真度仿真模型和数据输出。以某轴承性能退化数据为数据驱动源,对该框架进行了验证,仿真结果表明平行仿真方法能准确仿真装备性能退化过程,在提高预测精度的基础上实现了装备剩余寿命的自适应预测,有力证明了平行仿真方法的可行性和有效性。      

Development and performance evaluation of tropospheric scintillation model on Ku-band satellite link over Akure,Nigeria

Existing amplitude scintillation prediction models often perform less satisfactorily when deployed outside the regions where they were formulated. This necessitates the need to evaluate the performance of scintillation models developed in one region using data data from other regions while documenting their relative errors. Due to its variation with elevation angle, frequency, other link parameters and meteorological factors, we employed three years (January 2016 to December 2018) of concurrently measured satellite radio beacons and tropospheric weather parameters to develop a location-based amplitude scintillation prediction model over the Earth-space path of Akure (7.17^oN, 5.18^oE), South-western Nigeria. The satellite beacon measurement used Tektronix Y400 NetTek Analyzer at 1 s integration time while meteorological parameters, namely; temperature, pressure and relative humidity were measured using Davis Vantage Vue weather station at 1 min integration time. Comparative study of the model’s performance with nine (9) existing scintillation prediction models indicates that the best and worst performing models, in terms of root mean square error (RMSE), are the Statistical Temperature and Refractivity (STN) and direct physical and statistical prediction (DPSP) models with values 11.48 and 51.03 respectively. Also, worst month analysis indicates that April, with respective enhancement and fade values of 0.88 and 0.90 dB for 0.01% exceedance, is the overall worst calendar month for amplitude scintillation.     

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。      

Evaluation of three high-resolution satellite precipitation estimates: Potential for monsoon monitoring over Pakistan

Multi-sensor precipitation datasets including two products from the Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA) and estimates from Climate Prediction Center Morphing Technique (CMORPH) product were quantitatively evaluated to study the monsoon variability over Pakistan. Several statistical and graphical techniques are applied to illustrate the nonconformity of the three satellite products from the gauge observations. During the monsoon season (JAS), the three satellite precipitation products captures the intense precipitation well, all showing high correlation for high rain rates (>30 mm/day). The spatial and temporal satellite rainfall error variability shows a significant geo-topography dependent distribution, as all the three products overestimate over mountain ranges in the north and coastal region in the south parts of Indus basin. The TMPA-RT product tends to overestimate light rain rates (approximately 100%) and the bias is low for high rain rates (about ±20%). In general, daily comparisons from 2005 to 2010 show the best agreement between the TMPA-V7 research product and gauge observations with correlation coefficient values ranging from moderate (0.4) to high (0.8) over the spatial domain of Pakistan. The seasonal variation of rainfall frequency has large biases (100–140%) over high latitudes (36N) with complex terrain for daily, monsoon, and pre-monsoon comparisons. Relatively low uncertainties and errors (Bias ±25% and MAE 1–10 mm) were associated with the TMPA-RT product during the monsoon-dominated region (32–35N), thus demonstrating their potential use for developing an operational hydrological application of the satellite-based near real-time products in Pakistan for flood monitoring.     

Remote sounding of atmospheric gravity waves with satellite limb and nadir techniques

Recent advances in satellite techniques hold great potential for mapping global gravity wave (GW) processes at various altitudes. Poor understanding of small-scale GWs has been a major limitation to numerical climate and weather models for making reliable forecasts. Observations of short-scale features have important implication for validating and improving future high-resolution numerical models. This paper summarizes recent GW observations and sensitivities from several satellite instruments, including MLS, AMSU-A, AIRS, GPS, and CLAES. It is shown in an example that mountain waves with horizontal wavelengths as short as 30 km now can be observed by AIRS, reflecting the superior horizontal resolution in these modern satellite instruments. Our studies show that MLS, AMSU-A and AIRS observations reveal similar GW characteristics, with the observed variances correlated well with background winds. As a complementary technique, limb sounding instruments like CRISTA, CLAES, and GPS can detect GWs with better vertical but poorer horizontal resolutions. To resolve different parts of the broad GW spectrum, both satellite limb and nadir observing techniques are needed, and a better understanding of GW complexities requires joint analyses of these data and dedicated high-resolution model simulations.     

ROPP反演软件算法及其精度分析

介绍了ROPP反演软件中无线电掩星反演的算法与精度分析. 采用COSMIC卫星2008年1 月1日全天的附加相位数据, 反演得到折射率、温度、压强与湿度等参数, 并与CDAAC 相应结果进行对比. 实验结果表明, 在30km高度以下, 折射率、压强和湿度的相对 误差在2%以内, 温度误差不超过2K.      

Validation of the operational IASI level 2 processor using AIRS and ECMWF data

The algorithms being implemented in EUMETSAT’s IASI Level 2 Product Processing Facility are validated with real case situations using AIRS data and comparing the retrieved atmospheric states with ECMWF analyses. The tests have been performed for clear-sky ocean scenes during daytime.

The Empirical Orthogonal Function (EOF) retrievals show very good performance, with retrieved atmospheric states standard deviations between 1 and 2 K in temperature and 10% and 20% in relative humidity when compared with ECMWF analysis in the troposphere. The EOF retrievals show relatively smooth profiles.

Results from an iterative retrieval show a standard deviation between 2 and 3 K in temperature and 10% and 30% in relative humidity when compared with ECMWF analyses in the troposphere. They tend to show meteorologically reasonable discontinuities in both temperature and relative humidity. This seems to be the reason why they do not compare as well with ECMWF analyses as the EOF retrievals do. Whether they are closer to reality or not will have to be tested with co-located radiosondes or similar more accurate data, which generally do not exhibit such smooth vertical profiles as ECMWF analyses do.     

基于BP神经网络的纳卫星轨道温度预测

为了实现纳卫星在轨温度的预测,在对纳卫星热系统动态特性模型分析的基础上,建立BP神经网络预测模型实现纳卫星在轨温度的预测.通过分析纳卫星热系统动态特性模型,得到用于BP神经网络预测模型的输入、输出变量以及训练神经网络所需的数据样本.BP神经网络预测模型分别以纳卫星外壳、辐射器、舱内仪器的热流及温度值为神经网络输入、输出,预测纳卫星10s后的轨道温度.经验证,神经网络预测模型预测结果与纳卫星实际轨道温度吻合较好,表明神经网络预测模型是快捷有效的.      

Sensitivity analysis for air temperature profile estimation methods around the tropopause using simulated Aqua/AIRS data

A sensitivity analysis is performed to investigate potential improvements to the accuracy of air temperature profile retrievals near the tropopause. A simple inversion method is employed to identify and remove redundant spectral channels from the retrievals using simulated data for the high-spectral resolution sounder AIRS (Atmospheric Infrared Sounder) on the Aqua satellite. Bayesian optimal theory and inverse technique are applied for the atmospheric temperature profile retrievals, and the 15 μm CO₂ absorption bands (620–750 cm⁻¹) are chosen for this study. Sequentially elimination of redundant channels is directly integrated into the inverse scheme for the temperature profile, in order to accurately retain the valuable channels and remove all the redundant channels, for accurate retrieval of the temperature profile. Also, the tropopause and troposphere are treated differently in the inverse scheme to improve the retrieval accuracy in the tropopause. Results of a sensitivity analysis based on this method, for the Tropical and Middle-Latitude Summer models simulated by MODTRAN4.0, show that the estimated accuracies are improved by 2 K around the tropopause, and are only changed by less than 0.2 K in the troposphere.     

风云一号气象卫星地面应用系统

介绍了风云一号气象卫星资料接收处理系统,此系统由北京、广州、乌鲁木齐三个地面站和设于卫星气象中心的资料处理中心组成,也能兼顾接收处理NOAA 和GMS 气象卫星的资料。     

ARIMA-SVR组合模型在卫星遥测参数预测中的应用

为辅助卫星在轨运行提供决策分析支持，结合卫星遥测参数的时间序列特性，利用一种ARIMA-SVR组合预测方法，通过对卫星遥测参数进行预测，判定实际遥测数据是否处于正常范围。该组合模型利用ARIMA模型对预处理后的数据进行线性拟合，并利用SVR模型对数据的非线性部分进行补偿。以KX09卫星星敏A的温度遥测数据为基础，分别利用组合模型对短期及中期星敏A温度进行预测，得出短期和中期均方根误差（RMSE）分别为0.768和0.968，相比单一ARIMA模型，短中期RMSE分别提高46.2%和16.4%。此外，对该卫星陀螺B的x轴角速度进行了短中期预测:短期预测中，组合模型比单一ARIMA模型的RMSE提高71.2%；中期预测中，组合模型比单一ARIMA模型的RMSE提高64.2%。实验结果表明，ARIMA-SVR组合模型为保证卫星在轨正常运行提供了有效的决策分析支持。      

The impact of different background errors in the assimilation of satellite radiances and in-situ observational data using WRFDA for three rainfall events over Iran

Satellite radiances and in-situ observations are assimilated through Weather Research and Forecasting Data Assimilation (WRFDA) system into Advanced Research WRF (ARW) model over Iran and its neighboring area. Domain specific background error based on x and y components of wind speed (UV) control variables is calculated for WRFDA system and some sensitivity experiments are carried out to compare the impact of global background error and the domain specific background errors, both on the precipitation and 2-m temperature forecasts over Iran. Three precipitation events that occurred over the country during January, September and October 2014 are simulated in three different experiments and the results for precipitation and 2-m temperature are verified against the verifying surface observations. Results show that using domain specific background error improves 2-m temperature and 24-h accumulated precipitation forecasts consistently, while global background error may even degrade the forecasts compared to the experiments without data assimilation. The improvement in 2-m temperature is more evident during the first forecast hours and decreases significantly as the forecast length increases.     

气象卫星遥感海面温度的资料处理方法

气象卫星遥感海面温度的资料处理关键环节是云检测(筛选晴空区)和大气削弱订正。目前卫星气象中心的卫星海面温度处理业务系统中,针对美国的NOAA 卫星是利用国际上普遍使用的红外窗区多通道法。对于中国发射的风云一号(FY-1)气象卫星,由于星载辐射计只有一个红外窗区通道能用于大气削弱订正,为此专门开发了单通道海面温度处理方法。文章介绍了两种方法的基本原理、算法和处理结果举例,并对两种方法的特点作了简要评价。     

Rainfall estimation over a Mediterranean region using a method based on various spectral parameters of SEVIRI-MSG

The ultimate objective of this paper is the estimation of rainfall over an area in Algeria using data from the SEVIRI radiometer (Spinning Enhanced Visible and Infrared Imager). To achieve this aim, we use a new Convective/Stratiform Rain Area Delineation Technique (CS-RADT). The satellite rainfall retrieval technique is based on various spectral parameters of SEVIRI that express microphysical and optical cloud properties. It uses a multispectral thresholding technique to distinguish between stratiform and convective clouds. This technique (CS-RADT) is applied to the complex situation of the Mediterranean climate of this region. The tests have been conducted during the rainy seasons of 2006/2007 and 2010/2011 where stratiform and convective precipitation is recorded. The developed scheme (CS-RADT) is calibrated by instantaneous meteorological radar data to determine thresholds, and then rain rates are assigned to each cloud type by using radar and rain gauge data. These calibration data are collocated with SEVIRI data in time and space.     

Developing a stratospheric climatology from NMC analyses

The National Meteorological Center of the National Oceanic and Atmospheric Administration (NOAA) has archived global, daily synoptic analyses and computer gridded fields of geopotential height and temperature for 8 stratospheric pressure levels (70, 50, 30, 10, 5, 2, 1 and 0.4 mb) since the Autumn of 1978. More restricted analyses are available since 1964. The fields are discussed, with special emphasis on improvement of the data bases and analysis procedures. Included in the discussions are screening procedures for the climatological data base. Examples are given with regard to monthly mean energy, wind and hemispheric temperature patterns calculated as the initial development of a stratospheric dynamic climatology.     

Validate the IRI2007 model by the COSMIC slant TEC data during the extremely solar minimum of 2008

During 2008, the solar activity is extremely low. The satellite observations show that the ionospheric height and electron density is much lower than the predictions by the international reference ionosphere (IRI) model. In this paper, we compared the slant total electron content (TEC) observed by the COSMIC satellites during 2008 with the IRI model results. It is found that the IRI model with IRI2001 and IRI2001 Cor. topside options will always overestimate the electron density in both lower and higher altitudes. But the rest two topside options (NeQuick, and TTS) tend to overestimate the electron density in the F layer and underestimate it in the topside altitudes. The switch altitude between overestimation and underestimation and the latitude-local time distribution of the model deviation depend on the topside option. The current investigation might be useful for the model improvement as well as data assimilation work based on the IRI model and the LEO TEC data.     

卫星热平衡试验的温度预测与仿真模型

为了解决卫星热平衡试验中涉及的温度预测与变工况仿真试验问题,建立起星载仪器温度变化的双层集总参数模型,这一动态特性模型采用简单的嵌套结构,模型参数可以方便地运用系统辨识算法从卫星热平衡试验数据中获取,应用这一模型可以对不同星载仪器的温度变化进行分别的预测与仿真计算,从而大大减少了温度预测与仿真工作的计算量.对比研究表明:温度预测与仿真计算的结果与实际热平衡试验的结果一致.