scholarly journals A new lidar design for operational atmospheric wind and cloud/aerosol survey from space

2020 ◽  
Author(s):  
Didier Bruneau ◽  
Jacques Pelon
Keyword(s):  
Weather Prediction ◽  
Radiative Properties ◽  
Large Field ◽  
Horizontal Wind ◽  
Line Of Sight ◽  
Profile Measurement ◽  
Random Errors ◽  
Fabry Perot ◽  
Wind Profiles ◽  
Selection Of

Abstract. Global wind profile measurement has for long been a first priority for numerical weather prediction. The demonstration from ground-based observations that a double-edge Fabry-Perot interferometer could be efficiently used for deriving wind profiles from the molecular scattered signal in a very large atmospheric vertical domain has led to the choice of the direct detection technique in space and the selection of the Atmospheric Dynamic Mission (ADM) Aeolus by ESA in 1999. ADM-Aeolus was successfully launched in 2018, after the technical issues raised for the lidar development have been solved, providing first global wind profiles from space in the whole troposphere. Simulated and real time assimilation of the projected horizontal wind information were able to confirm the expected improvements in forecast score, validating the concept of a wind profiler using a fixed line-of-sight lidar from space. The question is raised here about consolidating results gained from ADM-Aeolus mission with a potential operational follow-on instrument. Maintaining the configuration of the instrument as close as possible to the one achieved (UV emission lidar with a single slanted line-of-sight) we revisit the concept of the receiver by replacing the arrangement of the Fizeau and Fabry-Perot interferometers with a unique Quadri-channel Mach-Zehnder (QMZ) interferometer which relaxes the system operational constraints and extends the observation capabilities to recover the radiative properties of clouds. This ability is meeting first and second profiling priorities of the meteorological forecasting community on atmospheric dynamics and radiation. We discuss the optimization of the key parameters that may preside to the selection of a high performance system. The selected optical path difference (3.2 cm) of the QMZ leads to a very compact design allowing the realization of a high quality interferometer and offering a large field-angle acceptance. Performance simulation of horizontal wind speed measurements with different backscatter profiles shows results in agreement with the targeted ADM-Aeolus random errors, using an optimal 45° line-of-sight angle. The Doppler measurement is, from principle, unbiased by the atmospheric conditions (temperature, pressure, particle scattering) and only weakly affected by the instrument calibration errors. The study of the random systematic errors arising from the uncertainties in the instrumental calibration and in the modelled atmospheric parameters used for the backscatter analysis shows a limited impact under realistic conditions. The particle backscatter coefficients can be retrieved with uncertainties better than a few percent in the boundary layer and in semi-transparent clouds. Extinction coefficients and depolarization ratio can be derived accordingly.

scholarly journals A new lidar design for operational atmospheric wind and cloud/aerosol survey from space

2021 ◽  
Vol 14 (6) ◽  
pp. 4375-4402
Author(s):  
Didier Bruneau ◽  
Jacques Pelon
Keyword(s):  
Atmospheric Dynamics ◽  
Radiative Properties ◽  
Single Line ◽  
Large Field ◽  
Horizontal Wind ◽  
Line Of Sight ◽  
Profile Measurement ◽  
Fabry Perot ◽  
Wind Profiles ◽  
Selection Of

Abstract. Global wind profile measurement has, for a long time, been a first priority for numerical weather prediction. The demonstration, from ground-based observations, that a double-edge Fabry–Pérot interferometer could be efficiently used for deriving wind profiles from the molecular scattered signal in a very large atmospheric vertical domain has led to the choice of the direct detection technique in space and the selection of the Atmospheric Dynamics Mission (ADM)-Aeolus by the European Space Agency (ESA) in 1999. ADM-Aeolus was successfully launched in 2018, after the technical issues raised by the lidar development had been solved, providing the first global wind profiles from space in the whole troposphere. Simulated and real-time assimilation of the projected horizontal wind information was able to confirm the expected improvements in the forecast score, validating the concept of a wind profiler using a single line-of-sight lidar from space. The question is raised here about consolidating the results gained from ADM-Aeolus mission with a potential operational follow-on instrument. Maintaining the configuration of the instrument as close as possible to the one achieved (UV emission lidar with a single line of sight), we revisit the concept of the receiver by replacing the arrangement of the Fizeau and Fabry–Pérot interferometers with a unique quadri-channel Mach–Zehnder (QMZ) interferometer, which relaxes the system's operational constraints and extends the observation capabilities to recover the radiative properties of clouds. This ability to profile wind and cloud/aerosol radiative properties enables the meeting of the two highest priorities of the meteorological forecasting community regarding atmospheric dynamics and radiation. We discuss the optimization of the key parameters necessary in the selection of a high-performance system, as based on previous work and development of our airborne QMZ lidar. The selected optical path difference (3.2 cm) of the QMZ leads to a very compact design, allowing the realization of a high-quality interferometer and offering a large field angle acceptance. Performance simulation of horizontal wind speed measurements with different backscatter profiles shows results in agreement with the targeted ADM-Aeolus random errors, using an optimal 45∘ line-of-sight angle. The Doppler measurement is, in principle, unbiased by the atmospheric conditions (temperature, pressure, and particle scattering) and only weakly affected by the instrument calibration errors. The study of the errors arising from the uncertainties in the instrumental calibration and in the modeled atmospheric parameters used for the backscattered signal analysis shows a limited impact under realistic conditions. The particle backscatter coefficients can be retrieved with uncertainties better than a few percent when the scattering ratio exceeds 2, such as in the boundary layer and in semi-transparent clouds. Extinction coefficients can be derived accordingly. The chosen design further allows the addition of a dedicated channel for aerosol and cloud polarization analysis.

scholarly journals Evaluation of wind profiles from the NERC MST Radar, Aberystwyth, UK

2014 ◽  
Vol 7 (5) ◽  
pp. 4589-4621
Author(s):  
C. F. Lee ◽  
G. Vaughan ◽  
D. A. Hooper
Keyword(s):  
Wind Speed ◽  
Standard Error ◽  
Random Error ◽  
Sampling Error ◽  
Weather Prediction ◽  
Horizontal Wind ◽  
Wind Speeds ◽  
Mst Radar ◽  
Wind Profiles ◽  
Aspect Sensitivity

Abstract. This study quantifies the uncertainties in winds measured by the Aberystwyth Mesosphere-Stratosphere-Troposphere (MST) radar (52.4° N, 4.0° W), before and after its renovation in March 2011. 127 radiosondes provide an independent measure of winds. Differences between radiosonde and radar-measured horizontal winds are correlated with long-term averages of vertical velocities, suggesting an influence from local mountain waves. These local influences are an important consideration when using radar winds as a measure of regional conditions, particularly for numerical weather prediction. In those applications, local effects represent a source of sampling error additional to the inherent uncertainties in the measurements themselves. The radar renovation improved the SNR of measurements, with correspondingly improved altitude coverage. It also corrected an under-estimate of horizontal wind speeds attributed to beam formation problems, due to component failure pre-renovation. The standard error in radar-measured winds averaged over half-an-hour increases with wind speed and altitude, and is 0.6–2.5 m s−1 (5–20% of wind speed) for post-renovation horizontal winds. Pre-renovation values are typically 0.4 m s−1 (0.03 m s−1) larger. The standard error in radial velocities is < 0.04 m s−1. Eight weeks of special radar operation are used to investigate the effects of echo power aspect sensitivity. Corrections for echo power aspect sensitivity remove an underestimate of horizontal wind speeds, however aspect sensitivity is azimuthally anisotropic at the scale of routine observations (≈ 1 h). This anisotropy introduces additional random error into wind profiles. For winds averaged over half-an-hour, the random error is around 3.5% above 8 km, but as large as 4.5% in the mid-troposphere.

scholarly journals A Method for Retrieving Mean Horizontal Wind Profiles from Single-Doppler Radar Observations Contaminated by Aliasing

2004 ◽  
Vol 132 (6) ◽  
pp. 1399-1409 ◽  
Author(s):  
Jidong Gao ◽  
Kelvin K. Droegemeier ◽  
Jiandong Gong ◽  
Qin Xu
Keyword(s):  
Radial Velocity ◽  
Wind Profile ◽  
Doppler Radar ◽  
Random Noise ◽  
Simulated Data ◽  
Horizontal Wind ◽  
Random Errors ◽  
The Mean ◽  
Wind Profiles ◽  
Full Volume

The velocity–azimuth display (VAD) technique was designed to estimate the areal mean vertical profile of the horizontal wind above a ground-based Doppler radar. The method uses radial velocity observations under the assumption of a linear wind field, though it encounters difficulty when the observations are contaminated by velocity ambiguities, large noise, and when viable data exist only over a restricted azimuthal range. The method suggested in this paper uses gradients of radial velocity, rather than only the velocity itself, to derive wind profiles and thus is termed the gradient velocity–azimuth display (GVAD) technique. Both the VAD and GVAD methods are tested first on simulated data to examine their sensitivity to different type of errors in radial velocity. The retrieved mean wind profiles are shown to be insensitive to random errors in radial velocity, even at large amplitude. However, the VAD method is very sensitive to systematic errors caused by velocity ambiguities. The experiments indicate that if only 3% of a full-volume scan of radial wind data is contaminated by aliasing errors, the relative rms error in the mean wind profile retrieved by VAD can reach 50%. In contrast, GVAD is very robust to such errors. Application of GVAD to Weather Surveillance Radar-1988 Doppler (WSR-88D) data collected during the 3 May 1999 tornado outbreak show that it has the ability to obtain accurate wind profiles even when the observations contain large errors caused by velocity ambiguities and random noise.

scholarly journals On the derivation of zonal and meridional wind components from Aeolus horizontal line-of-sight wind

2021 ◽  
Author(s):  
Isabell Krisch ◽  
Neil P. Hindley ◽  
Oliver Reitebuch ◽  
Corwin J. Wright
Keyword(s):  
Lower Stratosphere ◽  
Weather Prediction ◽  
Meridional Wind ◽  
Atmospheric Dynamics ◽  
Horizontal Wind ◽  
Line Of Sight ◽  
Wind Component ◽  
Horizontal Line ◽  
Sigma Level ◽  
Wind Measurements

Abstract. Since its launch in 2018, the European Space Agency’s Earth Explorer satellite Aeolus has provided global height resolved measurements of horizontal wind in the troposphere and lower stratosphere for the first time. Novel datasets such as these provide an unprecedented opportunity for the research of atmospheric dynamics and provide new insights into the dynamics of the upper troposphere and lower stratosphere (UTLS) region. Aeolus measures the wind component along its horizontal line-of-sight, but for the analysis and interpretation of atmospheric dynamics, zonal and/or meridional wind components are most useful. In this paper, we introduce and compare three different methods to derive zonal and meridional wind components from the Aeolus wind measurements. We find that the most promising method involves combining Aeolus measurements during ascending and descending orbits. Using this method, we derive global estimates of the zonal wind in the latitude range 79.7° S to 84.5° N with errors of less than 5 ms−1 (at the 2-sigma level). Due to the orbit geometry of Aeolus, the estimation of meridional wind in the tropics and at midlatitudes is more challenging and the quality is less reliable. However, we find that it is possible to derive meridional winds poleward of 70° latitude with absolute errors typically below ±5 ms−1 (at the 2-sigma level). This further demonstrate the value of Aeolus wind measurements for applications in weather and climate research, in addition to their important role in numerical weather prediction.

scholarly journals Characteristics and performance of vertical winds as observed by the radar wind profiler network of China

2020 ◽  
Author(s):  
Boming Liu ◽  
Jianping Guo ◽  
Wei Gong ◽  
Lijuan Shi ◽  
Yong Zhang ◽  
...  
Keyword(s):  
Wind Speed ◽  
Numerical Weather Prediction ◽  
Weather Prediction ◽  
Vertical Wind ◽  
Horizontal Wind ◽  
Wind Profiler ◽  
Numerical Weather ◽  
And Performance ◽  
Wind Profiles ◽  
Vertical Winds

Abstract. Vertical wind profiles are the foundation for numerical weather prediction systems research. Large-scale vertical wind data have been previously documented from network observations in several countries, but the nationwide vertical wind observations are poorly understood in China. In this study, the salient characteristics and performance of vertical winds as observed by the radar wind profiler network of China was investigated, which consists of more than 100 stations instrumented with 1290-MHz Doppler radar designed primarily for measuring vertical-resolved winds. This network has good spatial coverage, with denser sites in coastal areas. The vertical wind profiles observed by this network can provide the horizontal wind direction, horizontal wind speed, and vertical wind speed for every 120 m interval within the height of 0 to 3 km. The availability of the radar wind profiler network has been investigated in terms of effective detection height, data acquisition rate, data confidence, and data accuracy. Further comparison analysis with reanalysis data indicated that the observation data at 89 stations are recommended, and 17 stations are unrecommended. The vertical wind profiles can serve as important input dataset assimilated into numerical weather prediction system at both regional and global scales.

scholarly journals Evaluation of wind profiles from the NERC MST radar, Aberystwyth, UK

2014 ◽  
Vol 7 (9) ◽  
pp. 3113-3126 ◽  
Author(s):  
C. F. Lee ◽  
G. Vaughan ◽  
D. A. Hooper
Keyword(s):  
Wind Speed ◽  
Sampling Error ◽  
Signal To Noise Ratio ◽  
Weather Prediction ◽  
Horizontal Wind ◽  
Mountain Waves ◽  
Wind Speeds ◽  
Mst Radar ◽  
Wind Profiles ◽  
Aspect Sensitivity

Abstract. This study quantifies the uncertainties in winds measured by the Aberystwyth Mesosphere–Stratosphere–Troposphere (MST) radar (52.4° N, 4.0° W), before and after its renovation in March 2011. A total of 127 radiosondes provide an independent measure of winds. Differences between radiosonde and radar-measured horizontal winds are correlated with long-term averages of vertical velocities, suggesting an influence from local mountain waves. These local influences are an important consideration when using radar winds as a measure of regional conditions, particularly for numerical weather prediction. For those applications, local effects represent a source of sampling error additional to the inherent uncertainties in the measurements themselves. The radar renovation improved the signal-to-noise ratio (SNR) of measurements, with a corresponding improvement in altitude coverage. It also corrected an underestimate of horizontal wind speeds attributed to beam formation problems, due to pre-renovation component failure. The root mean square error (RMSE) in radar-measured horizontal wind components, averaged over half an hour, increases with wind speed and altitude, and is 0.8–2.5 m s−1 (6–12% of wind speed) for post-renovation winds. Pre-renovation values are typically 0.1 m s−1 larger. The RMSE in radial velocities is <0.04 m s−1. Eight weeks of special radar operation are used to investigate the effects of echo power aspect sensitivity. Corrections for echo power aspect sensitivity remove an underestimate of horizontal wind speeds; however aspect sensitivity is azimuthally anisotropic at the scale of routine observations (≈1 h). This anisotropy introduces random error into wind profiles. For winds averaged over half an hour, the RMSE is around 3.5% above 8 km, but as large as 4.5% in the mid-troposphere.

scholarly journals Characteristics and performance of wind profiles as observed by the radar wind profiler network of China

2020 ◽  
Vol 13 (8) ◽  
pp. 4589-4600 ◽  
Author(s):  
Boming Liu ◽  
Jianping Guo ◽  
Wei Gong ◽  
Lijuan Shi ◽  
Yong Zhang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Numerical Weather Prediction ◽  
Weather Prediction ◽  
Horizontal Wind ◽  
Wind Profiler ◽  
Numerical Weather ◽  
Spatial Coverage ◽  
And Performance ◽  
Wind Profiles

Abstract. Wind profiles are fundamental to the research and applications in boundary layer meteorology, air quality and numerical weather prediction. Large-scale wind profile data have been previously documented from network observations in several countries, such as Japan, the USA, various European countries and Australia, but nationwide wind profiles observations are poorly understood in China. In this study, the salient characteristics and performance of wind profiles as observed by the radar wind profiler network of China are investigated. This network consists of more than 100 stations instrumented with 1290 MHz Doppler radar designed primarily for measuring vertically resolved winds at various altitudes but mainly in the boundary layer. It has good spatial coverage, with much denser sites in eastern China. The wind profiles observed by this network can provide the horizontal wind direction, horizontal wind speed and vertical wind speed for every 120 m interval within the height of 0 to 3 km. The availability of the radar wind profiler network has been investigated in terms of effective detection height, data acquisition rate, data confidence and data accuracy. Further comparison analyses with reanalysis data indicate that the observation data at 89 stations are recommended and 17 stations are not recommended. The boundary layer wind profiles from China can provide useful input to numerical weather prediction systems at regional scales.

scholarly journals Initial Assessment of the Performance of the First Wind Lidar in Space on Aeolus

2020 ◽  
Vol 237 ◽  
pp. 01010 ◽  
Author(s):  
Oliver Reitebuch ◽  
Christian Lemmerz ◽  
Oliver Lux ◽  
Uwe Marksteiner ◽  
Stephan Rahm ◽  
...  
Keyword(s):  
Current Knowledge ◽  
Weather Prediction ◽  
Systematic Errors ◽  
Global Scale ◽  
Initial Assessment ◽  
Horizontal Wind ◽  
Successful Launch ◽  
Wind Lidar ◽  
Wind Profiles ◽  
Doppler Wind Lidar

Soon after its successful launch in August 2018, the spaceborne wind lidar ALADIN (Atmospheric LAser Doppler INstrument) on-board ESA’s Earth Explorer satellite Aeolus has demonstrated to provide atmospheric wind profiles on a global scale. Being the first ever Doppler Wind Lidar (DWL) instrument in space, ALADIN contributes to the improvement in numerical weather prediction (NWP) by measuring one component of the horizontal wind vector. The performance of the ALADIN instrument was assessed by a team from ESA, DLR, industry, and NWP centers during the first months of operation. The current knowledge about the main contributors to the random and systematic errors from the instrument will be discussed. First validation results from an airborne campaign with two wind lidars on-board the DLR Falcon aircraft will be shown.

STUDY OF INACCURACY IN THE OPERATION OF THE MAIN CONTROLLER OF STB MACHINE

2019 ◽  
Keyword(s):  
Normal Distribution ◽  
Stable Process ◽  
Random Errors ◽  
Actual Length ◽  
Experimental Data Processing ◽  
Set Up ◽  
Main Regulator ◽  
Transmission Gear ◽  
Selection Of

At production of fabrics, including fabrics for agricultural purpose, an important role is played by the cor-rect adjustment of operation of machine main regulator. The quality of setup of machine main controller is determined by the proper selection of rotation angle of warp beam weaving per one filling thread. In the pro-cess of using the regulator as a result of mistakes in adjustment, wear of transmission gear and backlashes in connections of details there are random changes in threads length. The purpose of the article is the research of property of random errors of basis giving by STB machine regulator. Mistakes can be both negative, and positive. In case of emergence only negative or only positive mistakes operation of the machine becomes im-possible as there will be a consecutive accumulation of mistakes. As a result of experimental data processing for stable process of weaving and the invariable diameter of basis threads winding of threads it is revealed that the random error of giving is set up as linear function of the accidental length having normal distribution. Measurements of accidental deviations in giving of a basis by the main regulator allowed to construct a curve of normal distribution of its actual length for one pass of weft thread. The presented curve of distribution of random errors in giving of a basis is the displaced curve of normal distribution of the accidental sizes. Also we define the density of probability of normal distribution of basis giving errors connected with a margin er-ror operation of the main regulator knowing of which allows to plan ways of their decrease that is important for improvement of quality of the produced fabrics.

scholarly journals Line-of-Sight Winds and Doppler Effect Smearing in ACE-FTS Solar Occultation Measurements

Atmosphere ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 680
Author(s):  
Chris D. Boone ◽  
Johnathan Steffen ◽  
Jeff Crouse ◽  
Peter F. Bernath
Keyword(s):  
Atmospheric Chemistry ◽  
Doppler Effect ◽  
Line Of Sight ◽  
Measured Signal ◽  
Mixing Ratio ◽  
Model Calculations ◽  
Doppler Shifts ◽  
Solar Occultation ◽  
Wide Range ◽  
Wind Profiles

Line-of-sight wind profiles are derived from Doppler shifts in infrared solar occultation measurements from the Atmospheric Chemistry Experiment Fourier transform spectrometers (ACE-FTS), the primary instrument on SCISAT, a satellite-based mission for monitoring the Earth’s atmosphere. Comparisons suggest a possible eastward bias from 20 m/s to 30 m/s in ACE-FTS results above 80 km relative to some datasets but no persistent bias relative to other datasets. For instruments operating in a limb geometry, looking through a wide range of altitudes, smearing of the Doppler effect along the line of sight can impact the measured signal, particularly for saturated absorption lines. Implications of Doppler effect smearing are investigated for forward model calculations and volume mixing ratio retrievals. Effects are generally small enough to be safely ignored, except for molecules having a large overhang in their volume mixing ratio profile, such as carbon monoxide.

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