scholarly journals A generalized simulation capability for rotating- beam scatterometers

2019 ◽  
Vol 12 (7) ◽  
pp. 3573-3594 ◽  
Author(s):  
Zhen Li ◽  
Ad Stoffelen ◽  
Anton Verhoef
Keyword(s):  
Incidence Angle ◽  
Retrieval Algorithm ◽  
Wind Vector ◽  
Response Functions ◽  
Rotating Beam ◽  
Retrieval Performance ◽  
Wind Retrieval ◽  
Figures Of Merit ◽  
Spatial Response

Abstract. Rotating-beam wind scatterometers exist in two types: rotating fan-beam and rotating pencil-beam. In our study, a generic simulation frame is established and verified to assess the wind retrieval skill of the three different scatterometers: SCAT on CFOSAT (China France Oceanography SATellite), WindRad (Chinese Wind Radar) on FY-3E, and SeaWinds on QuikSCAT. Besides the comparison of the so-called first rank solution retrieval skill of the input wind field, other figures of merit (FoMs) are applied to statistically characterize the associated wind retrieval performance from three aspects: wind vector root mean square error, ambiguity susceptibility, and wind biases. The evaluation shows that, overall, the wind retrieval quality of the three instruments can be ranked from high to low as WindRad, SCAT, and SeaWinds, where the wind retrieval quality strongly depends on the wind vector cell (WVC) location across the swath. Usually, the higher the number of views, the better the wind retrieval, but the effect of increasing the number of views reaches saturation, considering the fact that the wind retrieval quality at the nadir and sweet swath parts stays relatively similar for SCAT and WindRad. On the other hand, the wind retrieval performance in the outer swath of WindRad is improved substantially as compared to SCAT due to the increased number of views. The results may be generally explained by the different incidence angle ranges of SCAT and WindRad, mainly affecting azimuth diversity around nadir and number of views in the outer swath. This simulation frame can be used for optimizing the Bayesian wind retrieval algorithm, in particular to avoid biases around nadir but also to investigate resolution and accuracy through incorporating and analyzing the spatial response functions of the simulated Level-1B data for each WVC.

scholarly journals A Generalized Simulation Capability for Rotating Beam Scatterometers

2018 ◽  
Author(s):  
Zhen Li ◽  
Ad Stoffelen ◽  
Anton Verhoef
Keyword(s):  
Incidence Angle ◽  
Retrieval Algorithm ◽  
Pencil Beam ◽  
Wind Vector ◽  
Response Functions ◽  
Rotating Beam ◽  
Retrieval Performance ◽  
Wind Retrieval ◽  
Spatial Response

Abstract. Rotating-beam wind scatterometers exist in two types: rotating fan-beam and rotating pencil-beam. In our study, a generic simulation frame is established and verified to assess the wind retrieval skill of the three different scatterometers: SCAT on CFOSAT, WindRad on FY-3E and SeaWinds on QuikScat. Besides the comparison of the so-called 1st rank-solution retrieval skill of the input wind field, other Figure of Merits (FoMs) are applied to statistically characterize the associated wind retrieval performance from three aspects: wind vector root mean square error, ambiguity susceptibility, and wind biases. The evaluation shows that, overall, the wind retrieval quality of the three instruments can be ranked from high to low as WindRad, SCAT, and SeaWinds, where the wind retrieval quality strongly depends on the Wind Vector Cell (WVC) location across the swath. Usually, the higher the number of views, the better the wind retrieval, but the effect of increasing the number of views reaches saturation, considering the fact that the wind retrieval quality at the nadir and sweet swath parts stays relatively similar for SCAT and WindRad. On the other hand, the wind retrieval performance in the outer swath of WindRad is improved substantially as compared to SCAT due to the increased number of views. The results may be generally explained by the different incidence angle ranges of SCAT and WindRad, mainly affecting azimuth diversity around nadir and number of views in the outer swath. This simulation frame can be used for optimizing the Bayesian wind retrieval algorithm, in particular to avoid biases around nadir, but also to investigate resolution and accuracy through incorporating and analysing the spatial response functions of the simulated Level-1B data for each WVC.

scholarly journals The Passive Microwave Neural Network Precipitation Retrieval Algorithm for Climate Applications (PNPR-CLIM): Design and Verification

2021 ◽  
Vol 13 (9) ◽  
pp. 1701
Author(s):  
Leonardo Bagaglini ◽  
Paolo Sanò ◽  
Daniele Casella ◽  
Elsa Cattani ◽  
Giulia Panegrossi
Keyword(s):  
Neural Network ◽  
Passive Microwave ◽  
Retrieval Algorithm ◽  
Climate Data ◽  
High Quality ◽  
Data Record ◽  
Global Precipitation ◽  
Climate Data Record

This paper describes the Passive microwave Neural network Precipitation Retrieval algorithm for climate applications (PNPR-CLIM), developed with funding from the Copernicus Climate Change Service (C3S), implemented by ECMWF on behalf of the European Union. The algorithm has been designed and developed to exploit the two cross-track scanning microwave radiometers, AMSU-B and MHS, towards the creation of a long-term (2000–2017) global precipitation climate data record (CDR) for the ECMWF Climate Data Store (CDS). The algorithm has been trained on an observational dataset built from one year of MHS and GPM-CO Dual-frequency Precipitation Radar (DPR) coincident observations. The dataset includes the Fundamental Climate Data Record (FCDR) of AMSU-B and MHS brightness temperatures, provided by the Fidelity and Uncertainty in Climate data records from Earth Observation (FIDUCEO) project, and the DPR-based surface precipitation rate estimates used as reference. The combined use of high quality, calibrated and harmonized long-term input data (provided by the FIDUCEO microwave brightness temperature Fundamental Climate Data Record) with the exploitation of the potential of neural networks (ability to learn and generalize) has made it possible to limit the use of ancillary model-derived environmental variables, thus reducing the model uncertainties’ influence on the PNPR-CLIM, which could compromise the accuracy of the estimates. The PNPR-CLIM estimated precipitation distribution is in good agreement with independent DPR-based estimates. A multiscale assessment of the algorithm’s performance is presented against high quality regional ground-based radar products and global precipitation datasets. The regional and global three-year (2015–2017) verification analysis shows that, despite the simplicity of the algorithm in terms of input variables and processing performance, the quality of PNPR-CLIM outperforms NASA GPROF in terms of rainfall detection, while in terms of rainfall quantification they are comparable. The global analysis evidences weaknesses at higher latitudes and in the winter at mid latitudes, mainly linked to the poorer quality of the precipitation retrieval in cold/dry conditions.

A ‘Track-Wise’ Wind Retrieval Algorithm for the CYGNSS Mission

2019 ◽  
Author(s):  
Faozi Said ◽  
Zorana Jelenak ◽  
Jeonghwang Park ◽  
Seubson Soisuvarn ◽  
Paul S. Chang
Keyword(s):  
Retrieval Algorithm ◽  
Wind Retrieval

Phase-shifting digital holography with an unknown reference beam

2021 ◽  
Author(s):  
Roghayeh Yazdani ◽  
Hamidreza Fallah
Keyword(s):  
Digital Holography ◽  
Phase Retrieval ◽  
Reference Beam ◽  
Phase Shifting ◽  
Retrieval Algorithm ◽  
Reference Field ◽  
Digital Holograms ◽  
Noisy Conditions ◽  
Phase Retrieval Algorithm

In digital holography, errors of the reference field degrade the quality of the reconstructed object field. In this paper, we propose an effective method in phase-shifting digital holography in which the reference field does not need to be known and perfect. The unknown complex amplitudes of both reference and object fields are derived simultaneously. The method employs only five digital holograms and a single execution of a phase retrieval algorithm. So, the required measurements and algorithm executions in this method are fewer than those in other methods; it suggests a simpler and faster method. The effectiveness of the suggested method is indicated by simulation, under noise-free and noisy conditions. Moreover, the capability of the method to extract full information about the phase singularities in both fields is demonstrated.

New Statistical Figures of Merit for Color Quality of Solid-State Lamps

2019 ◽  
Vol 19 (12) ◽  
pp. 13-20
Author(s):  
A. Zukauskas ◽  
Rimantas Vaicekauskas ◽  
Feliksas Ivanauskas ◽  
Henrikas Vaitkevičius ◽  
Pranciškus Vitta ◽  
...  
Keyword(s):  
Solid State ◽  
Figures Of Merit ◽  
Color Quality

scholarly journals Optimization of production of the fermented milk beverage based on Tibetan kefir grains

2021 ◽  
Vol 247 ◽  
pp. 01003
Author(s):  
Rustem Khabibullin ◽  
Mahmud Adylov ◽  
Galina Ezhkova
Keyword(s):  
Shelf Life ◽  
Fermented Milk ◽  
Quality Characteristics ◽  
Response Functions ◽  
Functional Dependencies ◽  
Fermentation Conditions ◽  
Milk Fermentation ◽  
Kefir Grains ◽  
Central Composite

In recent years we have seen interest in Tibetan kefir grains (TKG) for production of fermented milk beverages. The article presents the results of the work on expanding the range of fermented milk beverages based on TKG, studying the influence of fermentation conditions on quality characteristics of beverages and their shelf life. The possibility of their optimization is shown. Using the method of Central Composite Design (CCD), response functions were obtained in the form of 2nd-order polynomials, and the numerical values of the coefficient of these dependencies were calculated. The conditions of milk fermentation by Tibetan kefir grains were optimized. The numerical values of the influencing factors are: the dose of inoculate is (60 ±2) g per 100 ml of the milk, fermentation duration -(30±3) h; fermentation temperature - (35±4)°C. We also studied the effect of sea buckthorn, chokeberry and lingonberry juice additives on the quality of fermented milk drinks and their shelf life. Using the same method CCD we determined the functional dependencies of sensory indicators and shelf life of the beverage on the added amount of berry juice and sucrose. According to the results of the conducted studies, the recipe of a fermented milk beverage was modified. The optimal content of the components (per 100 ml of the drink) is: juice – (12±2) ml, sucrose - (10±1) g.

scholarly journals Improvement of wind retrieval algorithm for Rayleigh Doppler lidar

2012 ◽  
Vol 61 (3) ◽  
pp. 030702
Author(s):  
Shen Fa-Hua ◽  
Shu Zhi-Feng ◽  
Sun Dong-Song ◽  
Wang Zhong-Chun ◽  
Xue Xiang-Hui ◽  
...  
Keyword(s):  
Retrieval Algorithm ◽  
Doppler Lidar ◽  
Wind Retrieval

scholarly journals Profiling wind and greenhouse gases by infrared-laser occultation: results from end-to-end simulations in windy air

2015 ◽  
Vol 8 (7) ◽  
pp. 2813-2825 ◽  
Author(s):  
A. Plach ◽  
V. Proschek ◽  
G. Kirchengast
Keyword(s):  
Wind Speed ◽  
Greenhouse Gases ◽  
Doppler Shift ◽  
Lower Stratosphere ◽  
Infrared Laser ◽  
Retrieval Algorithm ◽  
Upper Troposphere ◽  
Wind Retrieval ◽  
End To End ◽  
Thermodynamic Variables

Abstract. The new mission concept of microwave and infrared-laser occultation between low-Earth-orbit satellites (LMIO) is designed to provide accurate and long-term stable profiles of atmospheric thermodynamic variables, greenhouse gases (GHGs), and line-of-sight (l.o.s.) wind speed with focus on the upper troposphere and lower stratosphere (UTLS). While the unique quality of GHG retrievals enabled by LMIO over the UTLS has been recently demonstrated based on end-to-end simulations, the promise of l.o.s. wind retrieval, and of joint GHG and wind retrieval, has not yet been analyzed in any realistic simulation setting. Here we use a newly developed l.o.s. wind retrieval algorithm, which we embedded in an end-to-end simulation framework that also includes the retrieval of thermodynamic variables and GHGs, and analyze the performance of both stand-alone wind retrieval and joint wind and GHG retrieval. The wind algorithm utilizes LMIO laser signals placed on the inflection points at the wings of the highly symmetric C18OO absorption line near 4767 cm−1 and exploits transmission differences from a wind-induced Doppler shift. Based on realistic example cases for a diversity of atmospheric conditions, ranging from tropical to high-latitude winter, we find that the retrieved l.o.s. wind profiles are of high quality over the lower stratosphere under all conditions, i.e., unbiased and accurate to within about 2 m s−1 over about 15 to 35 km. The wind accuracy degrades into the upper troposphere due to the decreasing signal-to-noise ratio of the wind-induced differential transmission signals. The GHG retrieval in windy air is not vulnerable to wind speed uncertainties up to about 10 m s−1 but is found to benefit in the case of higher speeds from the integrated wind retrieval that enables correction of wind-induced Doppler shift of GHG signals. Overall both the l.o.s. wind and GHG retrieval results are strongly encouraging towards further development and implementation of a LMIO mission.

scholarly journals The Ozone Mapping and Profiler Suite (OMPS) Limb Profiler (LP) Version 1 aerosol extinction retrieval algorithm: theoretical basis

2018 ◽  
Vol 11 (5) ◽  
pp. 2633-2651 ◽  
Author(s):  
Robert Loughman ◽  
Pawan K. Bhartia ◽  
Zhong Chen ◽  
Philippe Xu ◽  
Ernest Nyaku ◽  
...  
Keyword(s):  
Spherical Shell ◽  
Theoretical Basis ◽  
Relaxation Method ◽  
Radiative Transfer Model ◽  
Aerosol Size Distribution ◽  
Retrieval Algorithm ◽  
Transfer Model ◽  
Aerosol Extinction ◽  
Horizontal Variations

Abstract. The theoretical basis of the Ozone Mapping and Profiler Suite (OMPS) Limb Profiler (LP) Version 1 aerosol extinction retrieval algorithm is presented. The algorithm uses an assumed bimodal lognormal aerosol size distribution to retrieve aerosol extinction profiles at 675 nm from OMPS LP radiance measurements. A first-guess aerosol extinction profile is updated by iteration using the Chahine nonlinear relaxation method, based on comparisons between the measured radiance profile at 675 nm and the radiance profile calculated by the Gauss–Seidel limb-scattering (GSLS) radiative transfer model for a spherical-shell atmosphere. This algorithm is discussed in the context of previous limb-scattering aerosol extinction retrieval algorithms, and the most significant error sources are enumerated. The retrieval algorithm is limited primarily by uncertainty about the aerosol phase function. Horizontal variations in aerosol extinction, which violate the spherical-shell atmosphere assumed in the version 1 algorithm, may also limit the quality of the retrieved aerosol extinction profiles significantly.

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