4th symposium on lidar atmospheric applications

5.3 Advantages of a coordinated scanning Doppler lidar and cloud radar system for wind measurements

K. Träumner, J. Handwerker, A. Wieser, J. Grenzhäuser and C. Kottmeier

KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)

4th Symposium on Lidar Atmospheric Applications

5.3 Advantages of a coordinated scanning Doppler lidar and cloud radar system

for wind measurements


Institute for Meteorology and Climate Research, KITKarlsruhe, Germany




Contents

Horizontal wind– complementary profiles and

– identification of measurement errors

Vertical wind – in different atmospheric situations

– a new approach estimating rain-drop size-distributions

– complementary profiles of vertical velocity variance




Instrumental and experimental setup

2 µm Doppler lidar

35.5 GHz cloud radar

Collocated on Hornisgrinde mountain (Black Forest) and performing a coordinated scan strategy from June to August 2007, COPS campaign




Horizontal wind

lidarradar

Hypothesis: aerosol drifts with horizontal wind independent of it’s size

simultaneous measurements deliver same results




Horizontal wind



only lidar

both

only radar

no data

Increase of available information from 32% using only lidar to 51% using the combination.




Horizontal wind



only lidar

both

only radar

no data

0

10

20

30

40

50

60

70

<0.1 <1 <2 >5

mit ground clutter

ohne groundclutter

velocities differ by




0

10

20

30

40

50

60

70

<0.1 <1 <2 >5

mit ground clutter

ohne groundclutter

Horizontal wind



Ground clutterproblem


only lidar

both

only radar

no data




Horizontal wind



Ground clutterproblem

0

10

20

30

40

50

60

70

80

90

<0.1 <1 <2 >5

mit ground clutter

ohne groundclutter

involving ground clutterground clutter corrected


only lidar

both

only radar

no data




Vertical wind

Hypothesis: size dependent fall velocity of the larger aerosols and droplets

simultaneously measurements deliver different results due to different wavelengths of the instruments and so different scatter mechanism




Vertical wind

Clear air day82.1% agree better than 0.5 ms-1






Vertical wind

During rain

Mean difference of 3 ms-1






Vertical wind during rain

Lidar double peaks




Vertical wind during rain

Radar Rayleigh scattering

reflectivity proportional D6

Lidar optical scattering

backscatter proportional D2

Size dependent terminal fall velocity and γ distribution of rain-drop-size

Idea: Estimating rain drop size distribution from velocity difference

lidar

radar




Power spectra and vertical wind variance

Is vertical velocity variance influenced by the differences of measured vertical velocity?

Clear air conditions Light rain conditions

Clouds ?

lidarradar




Conclusions

• Increase of valid horizontal wind information• Little redundant measurements• Potential to detect measurement errors• Differences in vertical wind velocity due to terminal size

dependent fall velocities of scatterers• New approach to estimate rain drop size distribution from

different measured velocities• Clear air power spectra behave quite similar, potential to

extend profiles of vertical velocity variance into clouds

Measurement combination of a cloud radar and a Doppler lidar allows new measurement approaches.




Thanks

Thanks for attention.

For details please see manuscript.




Additionally information




Instrument specifications

0.1 … 25° s-1Up to 10° s-1Scan velocity

-5 … 185°45 … 135°Elevation angle

0 … 360°-3 … 363°Azimuth angle

72 m30 mSpatial resolution

350 m150 mLowest range gate

100512Range gates

4.5 kW30 kWPeak power

100 MHz50 MHzSampling rate

± 20 ms-1± 10.6 ms-1Unambiguous velocity

500 Hz5 kHzPulse repetition frequency

425 ns200 nsPulse width

2023 nm8.44 mmwavelength

Wind lidarCloud radar




Effect ground clutter correction

4th symposium on lidar atmospheric applications

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