Overview of Wind Lidar Techniques and Current Related Developments at the Technical University of Catalonia
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paper_title: Edge technique: theory and application to the lidar measurement of atmospheric wind

paper_content:

The edge technique is a new and powerful method for measuring small frequency shifts. With the edge technique a laser is located on the steep slope of a high-resolution spectral filter, which produces large changes in transmission for small frequency shifts. A differential technique renders the frequency shift measurement insensitive to both laser and filter frequency jitter and drift. The measurement is shown to be insensitive to the laser width and shape for widths that are less than the half-width of the edge filter. The theory of the measurement is given with application to the lidar measurement of wind. The edge technique can be used to measure wind with a lidar by using either the aerosol or molecular backscattered signal. Examples of both measurements are presented. Simulations for a ground-based lidar at 1.06 μm using reasonable instrumental parameters are used to show an accuracy for the vector components of the wind that is better than 0.5 m/s from the ground to an altitude of 20 km for a 100-m vertical resolution and a 100-shot average. For a 20-m vertical resolution and a 10-shot average, simulations show an accuracy of better than 0.2 m/s in the first 2 km and better than 0.5 m/s to 5 km.
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paper_title: Wind Measurements with an Incoherent Lidar

paper_content:

Abstract : Atmospheric structures can be measured with incoherent optical radars (lidars). Because these structures drift with the wind, they can serve as a tracer for remote sensing of the wind vector. For this purpose, a dual monostatic scanning lidar system is available to measure the atmosphere simultaneously in two different directions over a maximum range of about 1 km. The transit time of identified patterns between two sensing points in the horizontal plane provides in combination with the geometry of the lidar, sufficient information to derive the horizontal wind vector. The method is based on cross-correlation techniques. To determine the spatial wind vector as a function of altitude it is sufficient to measure in three different upward directions. This can be realized with a triple lidar or with a single lidar by measuring consecutively in three different directions and using an equivalent but more extended inversion method.
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paper_title: Remote Sensing Of Three-Dimensional Winds With Elastic Lidar: Explanation Of Maximum Cross-Correlation Method

paper_content:

Maximum cross-correlation provides a method to remotely determine highly resolved three-dimensional fields of horizontal winds with elastic lidar throughout large volumes of the planetary boundary layer (PBL). This paper details the technique and shows comparisons between elastic lidar winds, remotely sensed laser Doppler velocimeter (LDV) wind profiles, and radiosonde winds. Radiosonde wind data were acquired at Barcelona, Spain, during the Barcelona Air-Quality Initiative (1992), and the LDV wind data were acquired at Sunland Park, New Mexico (N.M.), during the Border Area Air-Quality Study (1994). Comparisons show good agreement between the different instruments, and demonstrate the method useful for air pollution management at the local/regional scale. Elastic lidar winds could thus offer insight into aerosol and pollution transport within the PBL. Lidar wind fields might also be used to nudge or improve initialization and evaluation of atmospheric meteorological models.
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paper_title: Calculation of area-averaged vertical profiles of the horizontal wind velocity from volume-imaging lidar data

paper_content:

Area-averaged horizontal wind measurements are derived from the motion of spatial inhomogeneities in aerosol backscattering observed with a volume-imaging lidar. Spatial averaging provides high precision, reducing sample variations of wind measurements well below the level of turbulent fluctuations, even under conditions of very light mean winds and strong convection or under the difficult conditions represented by roll convection. Wind velocities are measured using the two-dimensional spatial cross correlation computed between successive horizontal plane maps of aerosol backscattering, assembled from three-dimensional lidar scans. Prior to calculation of the correlation function, three crucial steps are performed: (1) the scans are corrected for image distortion by the wind during a finite scan time; (2) a temporal high pass median filtering is applied to eliminate structures that do not move with the wind; and (3) a histogram equalization is employed to reduce biases to the brightest features.
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paper_title: Wind Measurements with an Incoherent Lidar

paper_content:

Abstract : Atmospheric structures can be measured with incoherent optical radars (lidars). Because these structures drift with the wind, they can serve as a tracer for remote sensing of the wind vector. For this purpose, a dual monostatic scanning lidar system is available to measure the atmosphere simultaneously in two different directions over a maximum range of about 1 km. The transit time of identified patterns between two sensing points in the horizontal plane provides in combination with the geometry of the lidar, sufficient information to derive the horizontal wind vector. The method is based on cross-correlation techniques. To determine the spatial wind vector as a function of altitude it is sufficient to measure in three different upward directions. This can be realized with a triple lidar or with a single lidar by measuring consecutively in three different directions and using an equivalent but more extended inversion method.
---
paper_title: Remote Sensing Of Three-Dimensional Winds With Elastic Lidar: Explanation Of Maximum Cross-Correlation Method

paper_content:

Maximum cross-correlation provides a method to remotely determine highly resolved three-dimensional fields of horizontal winds with elastic lidar throughout large volumes of the planetary boundary layer (PBL). This paper details the technique and shows comparisons between elastic lidar winds, remotely sensed laser Doppler velocimeter (LDV) wind profiles, and radiosonde winds. Radiosonde wind data were acquired at Barcelona, Spain, during the Barcelona Air-Quality Initiative (1992), and the LDV wind data were acquired at Sunland Park, New Mexico (N.M.), during the Border Area Air-Quality Study (1994). Comparisons show good agreement between the different instruments, and demonstrate the method useful for air pollution management at the local/regional scale. Elastic lidar winds could thus offer insight into aerosol and pollution transport within the PBL. Lidar wind fields might also be used to nudge or improve initialization and evaluation of atmospheric meteorological models.
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Title: Overview of Wind Lidar Techniques and Current Related Developments at the Technical University of Catalonia

Section 1: INTRODUCTION
Description 1: Introduce the concept of spatially resolved wind speed measurements and various remote sensing systems like sodar, radar, and lidar. Mention complementary techniques and basic measurement principles.

Section 2: DOPPLER DETECTION
Description 2: Explain the operation and principles behind Doppler lidar, focusing on Doppler shift detection.

Section 3: Coherent detection lidar
Description 3: Detail the coherent detection lidar systems, their advantages, limitations, and applications.

Section 4: Direct Detection Doppler lidar
Description 4: Describe direct detection Doppler lidar systems, different optical frequency discriminators, and their advantages for high-altitude measurements.

Section 5: Present work at the UPC: wind Doppler lidar
Description 5: Discuss the current developments in wind Doppler lidar by the Technical University of Catalonia, including principles, techniques, and prototype design.

Section 6: DIRECT MOTION DETECTION
Description 6: Outline the technique for direct motion detection in elastic lidars, focusing on retrieval of wind velocity fields from aerosol concentration patterns.

Section 7: Lines-of-sight pattern sensing
Description 7: Explain the first approach of direct motion detection using laser beam scanning in various directions for wind measurement.

Section 8: Area/Volume sensing
Description 8: Describe area/volume motion detection methods based on displacement detection in satellite imaging and scanning patterns.

Section 9: Present work at the UPC: correlation wind lidar
Description 9: Discuss the development and application of correlation wind lidar at the Technical University of Catalonia, highlighting methods and techniques used.

Section 10: SUMMARY
Description 10: Summarize the different atmospheric wind lidar techniques, comparing their suitability for various scenarios and future development directions.

Section 11: ACKNOWLEDGEMENTS
Description 11: Acknowledge the support and funding received from various institutions and projects.