scholarly journals New flexible retrieval for gusts and mean winds from Doppler wind lidars, tested for various scanning configurations

2021 ◽  
Author(s):  
Julian Steinheuer ◽  
Carola Detring ◽  
Frank Beyrich ◽  
Ulrich Löhnert ◽  
Petra Friederichs ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Least Squares ◽  
Sonic Anemometer ◽  
Fixed Number ◽  
Attractive Alternative ◽  
Time Interval ◽  
Wind Vector ◽  
Wind Gusts ◽  
Least Squares Fit ◽  
Double Beam

<p>In the Field Experiment on Sub-Mesoscale Spatio-Temporal Variability in Lindenberg (FESSTVaL, www.fesstval.de) various phenomena in the atmospheric boundary layer are investigated. One goal is to detect wind gusts from measurements of a Doppler wind lidar (DWL). DWL’s allow the determination of wind vector profiles with a high vertical resolution (∼ 30 m) and therefore are an attractive alternative to metorological towers.</p><p>However, obtaining wind gusts from DWL measurements is not trivial because a monostatic lidar provides only a radial velocity, i.e., only one component of a three-dimensional vector per individual beam. Measurements in at least three linearly independent directions are therefore necessary to derive the wind vector. These must be performed sequentially, which prolongs the time interval for determining the wind vector and therefore limits the time resolution of the derived wind vector. In order to retrieve wind gusts, wind maxima of a few seconds, one needs to operate the instrument in a quick scanning mode. In this presentation, we show results from different scanning modes and discuss the method for retrieving wind gusts. We tested various configurations with respect to their ability to detect gusts and mean winds at the Boundary Layer Field Site in Falkenberg in autumn 2019. The DWL configurations that measure different lines-of-sight with rapid temporal repetitions have a lower signal-to-noise ratio (SNR) but the highest chance of detecting gusts.</p><p>We have developed a new retrieval method that skips prior SNR filtering and instead iteratively removes a fixed number of measurements that do not match a least-squares-fit. The least-squares-fit is then recalculated on the reduced set of measurements, and if necessary, this step is repeated. With appropriate retrieval steps and iteration criteria, our results suggest that prior filtering can be omitted.</p><p><br>We present the results of our new retrieval for eight different DWL configurations consisting of double-beam swinging, step-stare modes, and continuous-scanning modes. The evaluation is done by a comparison of the minimum, maximum and mean wind speed at 90 m a.g.l. against the reference measurements of a sonic anemometer that is located nearby. Ongoing work is addressing further comparison of our retrieved wind variables with unmanned aerial vehicles from the FESSTVaL campaign in summer 2020.</p>

New flexible retrieval for gusts and mean winds from Doppler wind lidars

2021 ◽  
Author(s):  
Julian Steinheuer ◽  
Carola Detring ◽  
Frank Beyrich ◽  
Ulrich Löhnert ◽  
Stephanie Fiedler
Keyword(s):  
Radial Velocity ◽  
Sonic Anemometer ◽  
Three Dimensional ◽  
Time Interval ◽  
Wind Vector ◽  
Meteorological Tower ◽  
Wind Retrieval ◽  
Retrieval Technique ◽  
Wind Gusts ◽  
Spatio Temporal

<p>Phenomena in the atmospheric boundary layer are investigated in the Field Experiment on Sub-Mesoscale Spatio-Temporal Variability in Lindenberg (FESSTVaL, www.fesstval.de). Our aim is the retrieval of wind gusts from measurements of a Doppler wind lidar (DWL). DWLs allow the determination of wind vector profiles with high vertical resolution (∼30 m) and represent an alternative to classical meteorological tower observations. They can receive signals from altitudes higher than towers and are flexible in positioning. However, the retrieval of wind gusts from DWL measurements is not trivial because a monostatic lidar provides only one radial velocity, i.e., only one component of a three-dimensional vector, and measurements in three linearly independent directions are necessary to derive the wind vector. These have to be performed sequentially which limits the achievable time resolution, while wind gusts are short-lived phenomena. Therefore, we have developed a new wind retrieval that is applicable to different scanning configurations and various requested time resolutions. We tested several DWL configurations in autumn 2019 using DWL systems ’StreamLine’ from Halo Photonics and evaluated gust peaks and the 10min mean wind at 90 m height against data from a sonic anemometer at the meteorological tower. The most useful configuration for retrieving wind gusts is a fast continuous scan mode (CSM) that completes a full circulation cone within 3.4s. During this time interval, about eleven radial velocity measurements are completed. This fast CSM configuration was again successfully operated over a three-months period in summer 2020. We found that CSM paired with our new retrieval technique provides gusts which compare well to classical anemometer measurements from a meteorological tower. Future work includes the application of the new retrieval to DWL data during the FESSTVaL campaign in 2021 when DWL measurements are planned at different sites in order to study the sub-mesoscale variability of wind gusts.</p>

Whole-Lake Metal Radiotracer Movement in Fertilized Lake Basins

1987 ◽  
Vol 44 (S1) ◽  
pp. s74-s82 ◽  
Author(s):  
Raymond H. Hesslein
Keyword(s):  
Boundary Layer ◽  
Least Squares ◽  
Settling Velocity ◽  
Benthic Boundary Layer ◽  
Experimental Lakes Area ◽  
Northwestern Ontario ◽  
Lake Model ◽  
Least Squares Fit ◽  
C And N ◽  
Loss Rates

Seven radiotracers: 75Se, 203Hg, 85Sr, 134Cs, 59Fe, 65Zn, and 60Co were added to the separated basins of Lake 226, Experimental Lakes Area, northwestern Ontario. The basins, L226N and L226S were part of an ongoing eutrophication experiment in which C, N, and P were being added to L226N and C and N to L226S. The radiotracers moved to the sediments by sorption to settling particles and by being directly absorbed. The loss rates ranged from 3–8%∙d−1. Areal distribution in the sediments was largely governed by the percent sorbed to particles. Both basins exhibited seasonal anoxic hypolimnia in which redissolution of 59Fe, 60Co, and 203Hg was great, of 75Se, 85Sr, and 65Zn only minimal, and of 134Cs negligible. The overall behavior of each of the isotopes was nearly identical in the two basins, partly due to interbasin mixing. A least squares fit of the affinity for particles and loss rates to a whole-lake model yielded a settling velocity of 0.18 m∙d−1 and a benthic boundary layer of 370 μm thickness.

scholarly journals Meteorological observations of the coastal boundary layer structure at the Bulgarian Black Sea coast

2011 ◽  
Vol 6 (1) ◽  
pp. 251-259 ◽  
Author(s):  
D. Barantiev ◽  
M. Novitsky ◽  
E. Batchvarova
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Black Sea ◽  
Vertical Structure ◽  
Sonic Anemometer ◽  
Sea Breeze ◽  
Turbulence Measurements ◽  
Black Sea Coast ◽  
Meteorological Observatory ◽  
Sea Coast

Abstract. Continuous wind profile and turbulence measurements were initiated in July 2008 at the coastal meteorological observatory of Ahtopol on the Black Sea (south-east Bulgaria) under a Bulgarian-Russian collaborative program. These observations are the start of high resolution atmospheric boundary layer vertical structure climatology at the Bulgarian Black Sea coast using remote sensing technology and turbulence measurements. The potential of the measurement program with respect to this goal is illustrated with examples of sea breeze formation and characteristics during the summer of 2008. The analysis revealed three distinct types of weather conditions: no breeze, breeze with sharp frontal passage and gradually developing breeze. During the sea breeze days, the average wind speed near the ground (from sonic anemometer at 4.5 m and first layer of sodar at 30–40 m) did not exceed 3–4 m s−1. The onset of breeze circulation was detected based on surface layer measurements of air temperature (platinum sensor and acoustic), wind speed and direction, and turbulence parameters. The sodar measurements revealed the vertical structure of the wind field.

Changes in total body calcium balance with exercise in the rat

1983 ◽  
Vol 55 (1) ◽  
pp. 201-204 ◽  
Author(s):  
A. D. LeBlanc ◽  
H. J. Evans ◽  
P. C. Johnson ◽  
S. Jhingran
Keyword(s):  
Least Squares ◽  
Voluntary Exercise ◽  
Calcium Balance ◽  
Sprague Dawley ◽  
Total Body Calcium ◽  
Sprague Dawley Rats ◽  
Least Squares Fit ◽  
Significant Change ◽  
Total Body ◽  
And Control

The purpose of this study was to evaluate the effect of deconditioning on the total body calcium in rats. Two separate experiments were performed using female Sprague-Dawley rats, 187-266 days of age. Total body calcium was measured in experimental and control rats during and following several weeks of voluntary exercise. The slope from the least-squares fit of total body calcium with time was used to obtain an average calcium balance for each animal during each study period. In both groups the exercised rats had a significantly decreased calcium balance after cessation of exercise, whereas no significant change was seen in nonexercised controls. In both groups, the exercised animals gained calcium at a significantly greater rate than controls. Our findings indicate that while exercised rats may gain calcium at a faster rate compared with nonexercising controls, the rate of gain following cessation of exercise is less than the controls.

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