A soft computing approach for rainfall retrieval from the TRMM microwave imager

A neural network model for rainfall retrieval over ocean from remotely sensed microwave (MW) brightness temperature (BT) is proposed. BT data are obtained from the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI). The BT values from different channels of TMI over the Pacific Ocean (163/spl deg/ to 177/spl deg/W and 18/spl deg/ to 34/spl deg/S) are the input features. The near-surface rainfall rate from the Precipitation Radar (PR) are considered as a target. The proposed model consists of a neural network with online feature selection (FS) and clustering techniques. A K-means clustering algorithm is applied to cluster the selected features. Different networks have been trained to give an instantaneous rainfall rate with all input features as well as with selected features obtained by applying the FS algorithm. It is found that the hybrid network utilizing FS and clustering techniques performs better. The developed network is also validated with two independent datasets on March 14, 2000 over the Atlantic Ocean having stratiform rain and on March 21, 2000 over the Pacific Ocean having both stratiform and convective rain. In both cases, the hybrid network performs well with correlation coefficient improving to 0.78 and 0.81, respectively, in contrast to 0.70 and 0.75 for the network with all features. The rainfall rate retrieved from the hybrid network is also compared with the TMI surface rain rate, and a correlation of 0.84 and 0.75 is found for the two events. The proposed hybrid model is validated with a Doppler Weather Radar, and correlation of 0.52 is observed.     

The beamfilling algorithm for retrieval of hydrometeor profileparameters from passive microwave measurements

The horizontal inhomogeneity of the atmosphere within a satellite microwave radiometer's field of view (FOV) has always been considered as a source of rainfall retrieval errors. The hydrometeor profile retrieval algorithm presented exploits it to obtain an approximation of a radiative transfer model, which allows relatively simple inversion. The atmosphere within the FOV is treated as a combination of horizontally homogeneous domains. Assuming that one of known “basic” hydrometeor profiles occurs in each domain, the inverse problem is reduced to a determination of “beamfilling coefficients.” The online procedure includes determination of beamfilling coefficients and a footprint-averaged hydrometeor profile as a linear combination of “basic” ones. Off-line procedures involve the selection of a minimum number of necessary “basic” brightness temperature vectors and correction of “basic” hydrometeor profiles to provide the best retrieval accuracy for a given cloud/radiative simulation. The performance of the algorithm is tested for both numerical simulations and TRMM/TMI data. Numerical simulation has allowed a comparison of the information content of radiometer measurements from SSM/I, TMI, and the future AMSR. The effectiveness of the algorithm is being tested for rain water integral and rain rate retrievals from TRMM TMI measurements     

Conductivity measurements at the interface between the sinteredconductor and dielectric substrate at microwave frequencies

A novel measuring technique of the effective conductivity at microwave frequencies for both the sintered conductor surface and the interface between conductor and dielectric materials was developed. In the measurement, a dielectric rod resonator is placed between two dielectric plates, one side of which is coated with a sintered conductor. For measuring the surface conductivity, the dielectric rod is sandwiched by the conductor side of the plates. On the other hand, for measuring the interface conductivity, the dielectric rod is sandwiched by the dielectric side of the plates. By the configuration, only interface conductivity contributes to the conducting loss of the resonator, thus allowing the measurement of the interface conductivity. Using the new technique, the frequency dependence of both the surface and interface conductivity of a sintered copper, formed on a glass ceramic substrate by the co-firing technique, was investigated in the frequency range from 11 to 34 GHz. It was confirmed that the values of interface conductivity of the sintered copper were smaller than the values of the surface conductivity     

A multifrequency algorithm for the retrieval of soil moisture on alarge scale using microwave data from SMMR and SSM/I satellites

The sensitivity of microwave emission at different frequencies to soil moisture in bare and vegetated soils has been investigated using experimental data. Since the best frequency for the measurement of soil moisture (L-band) is absent in current satellite sensors, it is necessary to seek alternative solutions. An algorithm is proposed for the retrieval of soil moisture based on the sensitivity to moisture of both the brightness temperature and the polarization index at C-band, one that is able to correct for the effect of vegetation by means of the polarization index at X-band. The algorithm has been tested by using experimental data collected with airborne microwave radiometers on agricultural areas and validated by using the data sets of special sensor microwave/imager (SMM/I) and scanning multichannel microwave radiometer (SMMR). These research activities are planned in view of coming new satellites: AQUA (NASA) and ADEOS-II (NASDA), which will be launched by the end of 2001. These will have new generation microwave radiometers (AMSR-E and AMSR) onboard, which show much better characteristics with respect to the previous sensors, in particular an enhanced spatial resolution     

Multivariate statistical methods for modeling and analysis of wafer probe test data

Probe testing following wafer fabrication can produce extremely large amounts of data, which is often used to inspect a final product to determine if the product meets specifications. This data can be further utilized in studying the effects of the wafer fabrication process on the quality or yield of the wafers. Relationships among the parameters may provide valuable process information that can improve future production. This paper compares many methods of using the probe test data to determine the cause of low yield wafers. The methods discussed include two classes of traditional multivariate statistical methods, clustering and principal component methods and regression-based methods. These traditional methods are compared to a classification and regression tree (CART) method. The results for each method are presented. CART adequately fits the data and provides a "recipe" for avoiding low yield wafers and because CART is distribution-free there are no assumptions about the distributional properties of the data. CART is strongly recommended for analyzing wafer probe data.     

A statistical approach for determining radiometric precisions andaccuracies in the calibration of synthetic aperture radar imagery

A model that estimates a relative error bound for the radiometric calibration of synthetic aperture radar (SAR) imagery is presented. This model is based on a statistical `Coefficient of Variation of Error Model', which produces a relative error bound by propagating the measured or estimated uncertainties in the radar system parameters utilized to correct digitally processed SAR image intensity values. Using this model, algorithms are generated for absolute and relative radiometric calibration of SAR imagery. These algorithms are parametrically exercised using radar system parameters from an existing airborne SAR system to determine their impact on the relative error bound     

Microwave link dual-wavelength measurements of path-averageattenuation for the estimation of drop size distributions and rainfall

Microwave attenuation measurements at 25 and 38 GHz made on a 2.3-km microwave link are employed to estimate drop size distributions (DSD), rainfall rate, and rainfall accumulation. A theoretical model for the propagation of microwaves in a link system sets forth the basis for the development of a dual-wavelength analytical technique to invert two parameters of a path-average gamma DSD. The DSDs obtained from the technique are evaluated in conjunction with point measurements performed with a 2-D video disdrometer. Additionally, the DSDs yield path-average rainfall rates and rainfall accumulation which are compared with path-average measurements from a network of optical and tipping bucket rain gauges located beneath the link path, and with estimates based on empirical power law relations     

FY-3C微波湿温探测仪118 GHz和183 GHz通道辐射特性仿真分析

我国第二代极轨气象卫星的第三颗星——风云三号C星(FY-3C)已于2013年9月发射.为探讨微波湿温探测仪大气探测通道对大气参数的探测能力,采用威斯康星大学的非流体静力学中尺度模式系统(UW-NMS)模拟Katrina飓风的基础数据集,结合微波辐射传输模式,正演模拟分析了微波湿温探测仪118 GHz和183 GHz通道的辐射特性.仿真结果表明118 GHz和183 GHz通道作为星载亚毫米波大气探测通道,能够提供更加精细的大气温度和湿度廓线信息;冰态粒子的散射作用可使(118.75±5.0)GHz和(183.31±7.0)GHz通道亮温分别下降108 K和76 K,新增的探测频点和通道能提升对云雨大气的探测能力;118 GHz和183 GHz通道亮温对云中各种水凝物粒子响应的模拟分析结果证明了这两组通道在云中水凝物分布特性反演方面的潜在探测能力;大气中雨水含量的增加可以导致(118.75±5.0)GHz通道亮温下降4.5 K,118 GHz对液态粒子特有的响应能力,显示了其作为降水反演频点的优势;大气中雪粒子含量的增加会使(118.75±5.0)GHz通道亮温下降10 K,可利用该通道探测云中的雪晶含量.     

卫星遥感与6G通信遥感一体化

卫星遥感是人类实现高分辨率对地观测的重要手段,已逐步成为支撑经济社会发展以及国防安全的重要组成。6G追求通信遥感计算深度融合,通信遥感一体化成为其重要的特征。回顾了国内外卫星遥感的发展历程,概述了卫星遥感系统现有的体系结构和6G时代通信遥感一体化体系架构,阐述了人工智能驱动的典型卫星遥感技术和最新研究进展。针对6G时代卫星通信遥感一体化的趋势,探讨了实现“一星多用、多星组网、多网融合、智能服务”组合型发展的技术挑战和发展趋势。     

A methodology for surface soil moisture and vegetation opticaldepth retrieval using the microwave polarization difference index

A methodology for retrieving surface soil moisture and vegetation optical depth from satellite microwave radiometer data is presented. The procedure is tested with historical 6.6 GHz H and V polarized brightness temperature observations from the scanning multichannel microwave radiometer (SMMR) over several test sites in Illinois. Results using only nighttime data are presented at this time due to the greater stability of nighttime surface temperature estimation. The methodology uses a radiative transfer model to solve for surface soil moisture and vegetation optical depth simultaneously using a nonlinear iterative optimization procedure. It assumes known constant values for the scattering albedo and roughness, and that vegetation optical depth for H-polarization is the same as for V-polarization. Surface temperature is derived by a procedure using high frequency V-polarized brightness temperatures. The methodology does not require any field observations of soil moisture or canopy biophysical properties for calibration purposes and may be applied to other wavelengths. Results compare well with field observations of soil moisture and satellite-derived vegetation index data from optical sensors     

Millimeter-wave radiometric observations of the troposphere: acomparison of measurements and calculations based on radiosonde andRaman lidar

A comparison of clear-air brightness temperatures is performed between radiometric measurements and atmospheric radiative transfer calculations. The measurements were made using the NASA Goddard Space Flight Center's Millimeter-wave Imaging Radiometer (MIR) in a series of airborne and ground-based atmospheric experiments at six millimeter-wave frequencies: 89; 150; 183.3±1, ±3, ±7; and 220 GHz. With the inclusion of the 220 GHz channel, these measurements are the first passive observations of the atmosphere made simultaneously at the six frequencies. The MIR was operated concurrently with supporting meteorological instruments (radiosonde and Raman lidar) to construct a paired set of both spatially and temporally coincident calibrated brightness temperatures and atmospheric profile parameters. Calculated brightness temperatures based on the measured atmospheric profile parameters were obtained using a numerical radiative transfer model. Incremental water-vapor weighting functions were used to study the impact of radiosonde hygrometer errors on the radiative transfer calculations. The aircraft-based brightness temperature comparisons are generally within 3 K for the channels sensitive to the lower atmospheric levels (89, 150, 183.3±7, and 220 GHz), but show discrepancies of up to 11 K for the opaque channels (183.3±1 and ±3 GHz) caused primarily by radiosonde bias. The ground-based calculations are similarly found to be sensitive to hygrometer errors in the lower atmosphere. Ground-based comparisons between MIR observations and lidar-based calculations are typically within ±6 K     

Statistical properties of tropical rainfall intensity measured in Nigeria,for microwave and millimetre wave applications

The statistical properties of measured rainfall intensity, using a rapid response raingauge at Ile-Ife, a Southern Station in Nigeria, are presented in a form suitable for the study of tropical rain attenuation at microwave and millimetre wave bands. The seasonal variation of rainfall intensity is considered in terms of four climatological seasons of the year and the annual cumulative distribution of rainfall rate is compared with theccir curve for zone 1. The frequency of events of various peak rain rates and the duration of rain rates have been analysed. The results of the annual and worst-month analysis of the data are compared with those obtained in other parts of the world.     

Development and application of the Fraunhofer-diffraction method for measurements of plasma density fluctuations using infrared lasers

This paper is concerned with systematic developments of the Fraunhofer-diffraction method for studies of plasma density fluctuations in high-temperature plasmas using infrared lasers, namely (i) development of the general theory of the Fraunhofer-diffraction method, (ii) measurements of fluctuations propagating in an azimuthal direction, (iii) measurements of fluctuation intensities, and (iv) application in measurements on high-temperature plasmas.     

基于非均匀同区域线性CCD成像的卫星姿态调整与非线性定标方法

提出了对非均匀场景同一区域成像的卫星姿态调整及基于直方图匹配的线阵CCD非线性相对辐射定标方法.当在轨卫星需要执行相对辐射定标任务时,首先计算初始偏流角并调整卫星偏航角进入在轨定标成像模式;然后在定标成像过程中控制卫星偏航角,使得线阵CCD阵列的所有像元能够依次对同一区域成像;最后基于直方图匹配方法建立高精度非线性相对辐射定标模型.仿真实验给出了不同姿态对应的定标成像情况下的偏航角调整大小与调整周期,并分析了引起偏流角误差的因素及其对偏流角的不确定性.该方法既不需要地面均匀定标场等,也不需要统计分析大量在轨图像数据;且每一轨都可以执行定标任务,避免了卫星不同轨数据之间的不稳定性所带来的定标源自身不可靠问题.     

Variable-temperature loads for use in accurate noise measurements of cryogenically-cooled microwave amplifiers and mixers

We have demostrated the use of cryogenically-cooled variable-temperature loads for accurate noise measurements of low-noise cooled amplifiers and mixers in the microwave and millimeter wave range. The input noise temperature of the amplifier or mixer can be measured with an accuracy of ±1 K or better.     

Frequency measurements in the 10 μm infrared spectra of phosphine and allene

Sub-Doppler saturation spectra of phosphine and allene near 10 μm have been obtained using an offset locked waveguide CO₂ laser system. Frequency measurements and interpretations of the data are presented.     

Noninvasive infrared thermometry for application in skin biology.I. Model measurements and local measurements on the dorsal surface ofthe rabbit

Understanding thermal energy distribution is essential to interpret skin temperature for diagnosing various pathological and experimental conditions. The present paper investigates temperature data measurements acquired with an infrared thermometer system and in vivo temperature measurements on the backs of New Zealand rabbits. Local differences in skin temperature are significant around bony structures and in visceral areas. The results suggest that the location of experimental sites must be considered when interpreting data which use local temperature as an indicator of microvascular phenomena on the skin surface. Our techniques have proven valuable for quantifying thermal effects on small fields or skin lesions of experimental animals, and can be used noninvasively to measure the onset and transient vascular effects caused by noxious insults including laser radiation.     

The application of an expert system for information retrieval at the national archives

This paper describes a prototype computer system, designed to test the usefulness of expert information retrieval systems at the National Archives and Records Administration. The system engages in a dialogue with users who approach it with only vague requests for information, and helps them (1) clarify their request, and (2) efficiently locate the information they want.This is a backward-chaining, rule-based system that stores the compiled knowledge of expert archivists about records search as rules, and facts and metafacts about the records as lists. The system implements a simple logical model for how archivists navigate the Archives records, and provides a convenient format for interfacing with a database through list management.     

A new integration algorithm and its application to the analysis of symmetrical Cassegrain microwave antennas

An efficient numerical algorithm for physical optics (PO) analysis of reflectors is presented. Cylindrical symmetry of the reflector is not essential but is assumed for purposes of illustration, and this leads to the use of Fourier representation in the azimuthal variable. The algorithm is based on quadratic approximation of the phase and polynomial approximation of the remaining portion of the integrand. The necessary integrals are generated recursively and they involve the Fresnel integral. Additional efficiency is achieved by means of an interpolation scheme. Therein one interpolates all but the rapidly varying edge diffraction contribution to the integral and then adds the explicitly calculated edge contribution at each far-field point. A few illustrative examples are included.