Wind lidar @ Joyce

raw data from the halo photonics stream line wind lidar in Jülich

The instrument performs several scanning patterns and uses the remaining time for vertical staring.
Resolution is:
Scan patterns are currently:
An error estimate for the wind profiles can be found here.

Plots of current data:

current wind profile
wind profile from 3 different scans
VAD-plots
time height sections
w-statistics
hodograph
profiles
error and noise behaviour
technical data
VAD-36 scan
rhi scan


See also the Met-data from Jülich

current wind profile


Average profiles from DBS: speed on the left with solid=average, dashed=+/-stddev, dotted=min/max, dash-dotted=last,
direction on the right with large '+' symbol for the average, medium size '+' for average plus, minus stddev and tiny '+' for minimum and maximum.


wind profile from 3 different scans


Last profiles from DBS (left), VAD-3 (middle) and VAD-36 (right): In every of these plots you find:
left: wind speeds with horizontal speed (thick black) with error bars indicating total error (black), error from separation (magenta), error from doppler retrieval uncertainty (cyan) and an error estimate from the residuum of the retreival fit (grey). The red lines indicate vertical wind from scan retrieval (solid red) and the stddev of the vertical wind (dashed red)
middle: wind direction with error bars (black symbols) and doppler speed at the respective angle (gray lines). Refer to the axes in the upper part of the plot.
right: average backscatter with stddev.
For a comparison of wind retrievals from different subsets of the VAD-36 scan see vad_profiles.html
Click on images so enlarge


Profiles:
Left: thin lines: doppler components along beams in eastern, norhtern and vertical direction (dashed, dash-dotted and dotted)
thick lines: horizontal components in eastern (dashed) and northern direction (dash-dotted)
solid line and +-symbols: horizontal speed from instrument and from own calcualtion.
center: wind direction, +-symbols from instrument and x-symbols from own calcualtion
right: backscatter coeficient in vertical beam.


Velocity azimuth display (VAD): vectors give direction and speed of horizontal wind at time and height.
Vectors pointing upward indicate south wind, vectors pointing to the right indicate west wind.
Color shading gives the backscatter coefficient.
Wind vectors are determined by the instrument using the 'beam swing method', i.e. doppler velocities from three
beams are analysed to derive the three componentents of the wind vector at each level. Two of these beams
are tilted at an elavation of 75° and azimuth 0°(north) and 90° (east) and give the wind direction.
A third beam is vertical giving vertical velocity and thus can be used to calculate horizontal velocity from
the tilted beams.


VAD-plots


VAD as above for 00-24UTC from VAD-36 scans (left) and dbs scans (right).
The VAD-scan should not be mixed up with the VAD-plot:
The VAD-scan is a scan technique to measure wind profiles with a doppler profiler, the VAD-plot
shows horizontal wind vectors as function of time.



Time - height section of windspeed and direction in one colorcode.


speed vs time



dir vs time


time height sections


Time height section of vertical wind speed in the lower 2km. Gaps are due to wind profile measurements by DBS and VAD-3 (every 5 minutes) and conical scans for the VAD-36 technique (every 15minutes).



log(beta). Gaps are due to wind profile measurements by DBS and VAD-3 scans every 5 minutes and conical scans for the VAD-36 every 15 minutes.



Raw Time-height section of intensity. Data here is plotted versus index, gaps from above thus appear here as one pixel columns only.



Raw Time-height section of beta. Data here is plotted versus index, gaps from above thus appear here as one pixel columns only.



Raw Time-height section of log(intensity-1). Data here is plotted versus index, gaps from above thus appear here as one pixel columns only.



Raw Time-height section of log(beta). Data here is plotted versus index, gaps from above thus appear here as one pixel columns only.



Raw Time-height section of vertical wind speed. Data here is plotted versus index, gaps from above thus appear here as one pixel columns only.



'Bad' doppler values, i.e. values that are rejected due to intensity lower than threshold (~1.006)


w-statistics


Vertival velocity (blue = down, red = up) (left) and its histogram (right).



1 sec orignal values of vertival velocity (blue = down, red = up)



Standard deviation of vertival velocity σw in color shading and backscatter coefficient as isolines (left) and its pdf (right).



Standard deviation of vertival velocity σw without (left) and with (right) lag 0 noise correction (left).


Integral euler time scale Tcorr (left) and resulting length scale Lcorr= σwTcorr (right)



Skewness of vertival velocity: without (left) and with (middle) the Lenschow et al 2000 noise correction and the histogram (right, of the not denoised).



Backscatter coefficient (β) (left) and its histogram (right).



Pseudo trajectories calculated from the the high pass filtered vertical wind speed:
zt(t,z0) = z0 + t0t w(zt(t'),t')-wm(zt(t'),t') dt'.
with wm(z,t') = the half hour average of the vertical wind speed.

hodograph


Hodograph from average wind of the DBS-3 scans with stddev and min,max for speed and direction...



Hodografs from last DBS- (left), VAD-3- (middle) and VAD-36-scan (right): In every of these plots you find:
left: wind speeds with horizontal speed (thick black) with total-error (black 2D error-bars), error from separation (magenta 2D error-bars) and sigma_w (red circles)
right: traces of the beams in the moving air at different heights (black:z=75m, gray:z=2.5km) in absolute coordinates (bottom right) in relative coordinates normalized with correlation length (top right)

profiles


Intensity profile



Beta profile (lefdt) and its moments (right): Variance (solid), skewness (dotted) and Kurtosis (dashed).




log(beta) and its moments variance, skewness and kurtosis (solid, dotted, dashed)




Vertical wind speed and its moments variance, skewness and kurtosis (solid, dotted, dashed)




Vertical wind speed histograms with mean (solid) and median (dotted) marked.



Backscatter coefficient histograms, for all data (black), updrafts (red) and downdrafts (blue). Mean and median are marked solid and dotted respectively.

error and noise behaviour


Top left: Profiles of noise (squares), standard deviation (diamonds) and maxium of w (triangles). Top right: profile of broadband SNR. Bottom left: noise versus broadband SNR. Bottom right: max(w) vs broadband SNR. Noise is estimated by extrapolating the autocovaraince function from lag 1 to lag 0. Standard deviation is corrected for this by substracting the noise. Solid line in lower left plot shows error estimate after Pearson et al. (2009), dashed line is the error estime for a direct detection, horizontal dotted line is standard devation of white noise in full bandwidth interval.

technical data


Beta versus intensity



Only positive beta values versus intensity, left linear, right logarithmic



Vertical wind speed versus intensity



Power spectrum of vertical velocity (dots) and fitted P(f) = 2 P0 /( 1 + (f Tstar)^n ) with n=5/3 (line with diamonds)
Normalized ogives from low to high frequencies and the resulting time/frequency scale which separates the spectrum at half total power (dashed lines).


Autocorrelation function with a=exp(-t/T*) fitted to first 10 values (solid), integral ∫0t acor(t') dt'/1000s (dotted)



Background vs time and 'height' (top), and Intensity values around 1 (bottom)


Background vs time (top) and vs range gate (=height) (bottom)


Background values after the pulse (red) and second pulse (blue). Colored numbers give the range gate numbers.


System log of its internal temperatur, humidity and power supply.


Volts versus power supply: both, when heating or cooling starts, supply goes down. Cooling starts at 30degC, heating at 18.5degC. Instruments goes into save mode (switch off) for temperatures above 41degC. Arrows indicate gaps in time series and how temperatur and voltage changed.


Schedule of the last hour.

VAD-36 scan


Doppler velocity from 'VAD-36 - scan'


log beta from VAD-36 scan


Residuum after profile fit


Profiles from fit to VAD-36 - scan data


Doppler speeds in VAD-36 - scan versus azimuth and fits (dotted lines)

RHI scan


Plot of RHI scan with shading according to backscatter coeficient and measured doppler components along beam as vectors.


Plot of RHI scan with shading according to interpolated backscatter coeficient and wind vectors (u,w) in RHI plane based on a combination of two neighboring beams.


Doppler component vd along beam from RHI scan versus x-coordinate for different heights (solid lines triangles, height in km at data points), and vd/cos(ele) = um + u' + w' tan(ele) (dotted line with asterisk) a measure for the average horizontal wind component um(z) plus component due to deviation vector (u',w').