Studies for the Odin sub-millimetre radiometer. II. Retrieval methodology

2002 ◽  
Vol 80 (4) ◽  
pp. 341-356 ◽  
Author(s):  
Ph. Baron ◽  
Ph. Ricaud ◽  
J de la Noë ◽  
J EP Eriksson ◽  
F Merino ◽  
...  
Keyword(s):  
Frequency Band ◽  
Estimation Method ◽  
High Sensitivity ◽  
Optimal Estimation ◽  
Forward Model ◽  
Model Errors ◽  
Target Species ◽  
Spectral Parameters ◽  
Chlorine Monoxide ◽  
Standard Code

This paper presents the first algorithm developed to retrieve atmospheric vertical profiles of trace gases from calibrated spectra measured by the sub-millimetre radiometer (SMR) onboard the Odin satellite. An estimation of atmospheric profiles is obtained by means of an inversion of the spectra using the Optimal Estimation Method. Great attention is paid to the study of the simultaneous retrieval of several species and nonlinearity effects. The measurement response is defined to give the altitude domain of a good retrieval. Main sources of measurement and forward model errors are characterized and separated into two categories: the fixed errors and the variable errors. We define a standard retrieval strategy that can be applied to theoretically investigate any frequency band of any observing Odin mode. For each frequency band, two categories of species are defined: the target species, i.e., the main species to be retrieved, and the interfering species, i.e., molecules emitting an interfering radiance in the observed band. The standard code is based upon an inversion of spectra using a linearized forward model and simultaneously estimates target species and interfering species. As an example, inversions of synthetic noise-free spectra of ozone and chlorine monoxide within an autocorrelator band ranging from 501.18 to 501.58 GHz are shown to behave as expected in the middle stratosphere and in the lower mesosphere. The error analysis shows retrieval limitations in the lower stratosphere that are mainly induced by the high sensitivity of the retrieval to parameters such as tangent height, accuracy in the vertical profile of the interfering species, and spectral parameters of both target lines and interfering lines. PACS Nos.: 42.68Ay, 07.07Df, 07.57Kp

scholarly journals First application of the optimal estimation method to retrieve temperature from pure rotational raman scatter lidar measurements

2018 ◽  
Vol 176 ◽  
pp. 01011
Author(s):  
S. Mahagammulla Gamage ◽  
A. Haefele ◽  
R.J. Sica
Keyword(s):  
Estimation Method ◽  
Optimal Estimation ◽  
Forward Model ◽  
Temperature Calibration ◽  
Lidar Measurements ◽  
Raman Scatter ◽  
Calibration Coefficients

We present the application of the Optimal Estimation Method (OEM) to retrieve atmospheric temperatures from pure rotational Raman (PRR) backscatter lidar measurements. A forward model (FM) is developed to retrieve temperature and tested using synthetic measurements. The OEM offers many advantages for this analysis, including eliminating the need to determine temperature calibration coefficients.

scholarly journals Stratospheric Ozone Density Retrieval Using the Optimal Estimation Method (OEM)

2018 ◽  
Vol 176 ◽  
pp. 03006
Author(s):  
Ghazal Farhani ◽  
R. J. Sica ◽  
Sophie Godin-Beekmann ◽  
Alexander Haefele
Keyword(s):  
Traditional Method ◽  
Inverse Method ◽  
Stratospheric Ozone ◽  
Estimation Method ◽  
Optimal Estimation ◽  
Uncertainty Budget ◽  
Forward Model ◽  
Differential Absorption ◽  
Differential Absorption Lidar

We use an Optimal Estimation Method (OEM) to retrieve ozone profiles from the CANDAC Stratospheric Ozone Differential Absorption Lidar in Eureka, Canada. The OEM is a well known inverse method in which a forward model (FM) is used to describe the instrument and geophysical situation. We have developed a FM and are testing its validity using synthetic measurements. We will present the advantages of using OEM retrievals over the traditional method, including a full uncertainty budget.

scholarly journals Quality assessment of ground-based microwave measurements of chlorine monoxide, ozone, and nitrogen dioxide from the NDSC radiometer at the Plateau de Bure

2004 ◽  
Vol 22 (6) ◽  
pp. 1903-1915 ◽  
Author(s):  
P. Ricaud ◽  
P. Baron ◽  
J. de La Noë
Keyword(s):  
Microwave Radiometer ◽  
Estimation Method ◽  
Optimal Estimation ◽  
Temporal Variations ◽  
Data Sets ◽  
Site Location ◽  
Data Set ◽  
Chlorine Monoxide ◽  
Slow Drift ◽  
Retrieval Scheme

Abstract. A ground-based microwave radiometer dedicated to chlorine monoxide (ClO) measurements around 278GHz has been in operation from December 1993-June 1996 at the Plateau de Bure, France (45° N, 5.9° E, 2500m altitude). It belongs to the international Network for the Detection of Stratospheric Change. A detailed study of both measurements and retrieval schemes has been undertaken. Although dedicated to the measurements of ClO, simultaneous profiles of O3, ClO and NO2, together with information about the instrumental baseline, have been retrieved using the optimal estimation method. The vertical profiles have been compared with other ground-based microwave data, satellite-borne data and model results. Data quality shows: 1) the weak sensitivity of the instrument that obliges to make time averages over several hours; 2) the site location where measurements of good opacities are possible for only a few days per year; 3) the baseline undulation affecting all the spectra, an issue common to all the microwave instruments; 4) the slow drift of some components affecting frequencies by 3-4MHz within a couple of months. Nevertheless, when temporally averaging data over a few days, ClO temporal variations (diurnal and over several weeks in winter 1995) from 35-50km are consistent with model results and satellite data, particularly at the peak altitude around 40km, although temporal coincidences are infrequent in winter 1995. In addition to ClO, it is possible to obtain O3 information from 30-60km whilst the instrument is not optimized at all for this molecule. Retrievals of O3 are reasonable when compared with model and another ground-based data set, although the lowermost layers are affected by the contamination of baseline remnants. Monthly-averaged diurnal variations of NO2 are detected at 40km and appear in agreement with photochemical model results and satellite zonally-averaged data, although the amplitude is weaker than the other data sets. This NO2 result highlights the great potential of the retrieval scheme used.

scholarly journals An Optimal Estimation Retrieval Algorithm for Microwave Humidity Sounding Channels with Minimal Scan Position Bias

2019 ◽  
Vol 36 (3) ◽  
pp. 409-425 ◽  
Author(s):  
Richard M. Schulte ◽  
Christian D. Kummerow
Keyword(s):  
Incidence Angle ◽  
Optimal Estimation ◽  
Precipitable Water ◽  
Forward Model ◽  
Retrieval Algorithm ◽  
Model Errors ◽  
Inversion Algorithm ◽  
Liquid Water Path ◽  
Small Satellites ◽  
Cloud Liquid Water Path

AbstractA flexible and physical optimal estimation-based inversion algorithm for retrieving atmospheric water vapor and cloud liquid water path from passive microwave radiometers over the global oceans is presented. The algorithm’s main strength lies in its ability to explicitly account for forward model errors that depend on the Earth incidence angle (EIA) at which a given radiometer measurement is made. Validation of total precipitable water (TPW) retrieved from Microwave Humidity Sounder (MHS) measurements against near-coincident estimates of TPW from SuomiNet GPS ground stations shows that retrieved TPW values agree closely with SuomiNet estimates, and somewhat better than values from the Microwave Integrated Retrieval System that are retrieved from the same MHS instruments. More importantly, it is found that the inclusion of appropriate forward model error assumptions, which are tailored to the EIA and sea surface temperature of the scene being considered, are able to almost entirely eliminate EIA-dependent biases in retrieved TPW. This result holds true across all satellites currently carrying an MHS instrument, despite the fact that only measurements from one satellite are used to estimate forward model errors. The consistency achieved by the retrieval algorithm across all view angles suggests that other inversion algorithms, particularly those for cross-track-scanning radiometers and potential future constellations of small satellites, would benefit from the inclusion of nuanced error assumptions that consider the effect of EIA.

scholarly journals Industrial Plume Properties Retrieved by Optimal Estimation Using Combined Hyperspectral and Sentinel-2 Data

2021 ◽  
Vol 13 (10) ◽  
pp. 1865
Author(s):  
Gabriel Calassou ◽  
Pierre-Yves Foucher ◽  
Jean-François Léon
Keyword(s):  
Matched Filter ◽  
Estimation Method ◽  
Optimal Estimation ◽  
Model Parameters ◽  
Surface Reflectance ◽  
Sequential Method ◽  
Modal Radius ◽  
Sentinel 2

Stack emissions from the industrial sector are a subject of concern for air quality. However, the characterization of the stack emission plume properties from in situ observations remains a challenging task. This paper focuses on the characterization of the aerosol properties of a steel plant stack plume through the use of hyperspectral (HS) airborne remote sensing imagery. We propose a new method, based on the combination of HS airborne acquisition and surface reflectance imagery derived from the Sentinel-2 Multi-Spectral Instrument (MSI). The proposed method detects the plume footprint and estimates the surface reflectance under the plume, the aerosol optical thickness (AOT), and the modal radius of the plume. Hyperspectral surface reflectances are estimated using the coupled non-negative matrix factorization (CNMF) method combining HS and MSI data. The CNMF reduces the error associated with estimating the surface reflectance below the plume, particularly for heterogeneous classes. The AOT and modal radius are retrieved using an optimal estimation method (OEM), based on the forward model and allowing for uncertainties in the observations and in the model parameters. The a priori state vector is provided by a sequential method using the root mean square error (RMSE) metric, which outperforms the previously used cluster tuned matched filter (CTMF). The OEM degrees of freedom are then analysed, in order to refine the mask plume and to enhance the quality of the retrieval. The retrieved mean radii of aerosol particles in the plume is 0.125 μμm, with an uncertainty of 0.05 μμm. These results are close to the ultra-fine mode (modal radius around 0.1 μμm) observed from in situ measurements within metallurgical plant plumes from previous studies. The retrieved AOT values vary between 0.07 (near the source point) and 0.01, with uncertainties of 0.005 for the darkest surfaces and above 0.010 for the brightest surfaces.

scholarly journals A Modified Extended Kalman Filter for a Two-Antenna GPS/INS Vehicular Navigation System

Sensors ◽  
2018 ◽  
Vol 18 (11) ◽  
pp. 3809 ◽  
Author(s):  
Yushi Hao ◽  
Aigong Xu ◽  
Xin Sui ◽  
Yulei Wang
Keyword(s):  
Kalman Filter ◽  
Extended Kalman Filter ◽  
Navigation System ◽  
Adaptive Estimation ◽  
Estimation Method ◽  
Measurement Noise ◽  
Model Errors ◽  
State Process ◽  
Stability And Accuracy ◽  
The Impact

Recently, the integration of an inertial navigation system (INS) and the Global Positioning System (GPS) with a two-antenna GPS receiver has been suggested to improve the stability and accuracy in harsh environments. As is well known, the statistics of state process noise and measurement noise are critical factors to avoid numerical problems and obtain stable and accurate estimates. In this paper, a modified extended Kalman filter (EKF) is proposed by properly adapting the statistics of state process and observation noises through the innovation-based adaptive estimation (IAE) method. The impact of innovation perturbation produced by measurement outliers is found to account for positive feedback and numerical issues. Measurement noise covariance is updated based on a remodification algorithm according to measurement reliability specifications. An experimental field test was performed to demonstrate the robustness of the proposed state estimation method against dynamic model errors and measurement outliers.

scholarly journals On the limit to resolution and information on basal properties obtainable from surface data on ice streams

2008 ◽  
Vol 2 (2) ◽  
pp. 167-178 ◽  
Author(s):  
G. H. Gudmundsson ◽  
M. Raymond
Keyword(s):  
Flow Line ◽  
Estimation Method ◽  
Optimal Estimation ◽  
Surface Flow ◽  
Ice Thickness ◽  
Ice Streams ◽  
Statistical Estimates ◽  
Surface Data ◽  
Highly Sensitive ◽  
Surface Measurements

Abstract. An optimal estimation method for simultaneously determining both basal slipperiness and basal topography from variations in surface flow velocity and topography along a flow line on ice streams and ice sheets is presented. We use Bayesian inference to update prior statistical estimates for basal topography and slipperiness using surface measurements along a flow line. Our main focus here is on how errors and spacing of surface data affect estimates of basal quantities and on possibly aliasing/mixing between basal slipperiness and basal topography. We find that the effects of spatial variations in basal topography and basal slipperiness on surface data can be accurately separated from each other, and mixing in retrieval does not pose a serious problem. For realistic surface data errors and density, small-amplitude perturbations in basal slipperiness can only be resolved for wavelengths larger than about 50 times the mean ice thickness. Bedrock topography is well resolved down to horizontal scale equal to about one ice thickness. Estimates of basal slipperiness are not significantly improved by accurate prior estimates of basal topography. However, retrieval of basal slipperiness is found to be highly sensitive to unmodelled errors in basal topography.

Reliability assessment of offshore dynamic scour protections using copulas

2018 ◽  
Vol 43 (5) ◽  
pp. 506-538 ◽  
Author(s):  
T Fazeres-Ferradosa ◽  
F Taveira-Pinto ◽  
X Romão ◽  
MT Reis ◽  
L das Neves
Keyword(s):  
Wind Farm ◽  
Estimation Method ◽  
Information Criterion ◽  
Probability Of Failure ◽  
Parametric Estimation ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Spectral Parameters ◽  
Peak Period ◽  
Kendall’S Τ

This article presents a methodology to assess the reliability of dynamic scour protections used to protect offshore wind turbine foundations. The computed probabilities of failure are based on a dataset of 124 months of hindcast data from the Horns Rev 3 offshore wind farm. Copula-based models are used to obtain the joint distribution function of the significant wave height and spectral peak period and to obtain the probability of failure of scour protections. The sensitivity of the probability of failure to each model is addressed. The influence of the duration of the waves’ time series is also studied. A sensitivity analysis of the probability of failure to physical constraints, such as the water depth, current’s velocity or the mean diameter of the armour units, is performed. The results show that probability of failure is dependent on the copula used to model the spectral parameters and the associated value of Kendall’s τ. It is shown that the copula presenting the best values of Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC) did not lead to the probabilities of failure that are closer to the non-parametric estimation, obtained by means of the bivariate version of the Kernel density estimation method. The application to the case study led to annual probabilities of failure, which are comparable with the values applied for other offshore components, according to the current offshore wind industry standards.

scholarly journals Physical Principles of a Piezo Accelerometer Sensitive to a Nearly Constant Signal

Sensors ◽  
2018 ◽  
Vol 18 (10) ◽  
pp. 3258 ◽  
Author(s):  
Valery Gupalov ◽  
Alexander Kukaev ◽  
Sergey Shevchenko ◽  
Egor Shalymov ◽  
Vladimir Venediktov
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Frequency Band ◽  
Linear Acceleration ◽  
High Sensitivity ◽  
Element Model ◽  
Wide Frequency Band ◽  
Piezoelectric Accelerometer ◽  
The Finite Element Model ◽  
Physical Principles

The paper considers the construction of a piezoelectric accelerometer capable of measuring constant linear acceleration. A number of designs are proposed that make it possible to achieve high sensitivity with small dimensions and a wide frequency band (from 10−5 Hz). The finite element model of the proposed design was investigated, and its output characteristic and scale factor (36 mV/g) were obtained.

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