1. Remote-sensing profiling instruments in Helsinki Testbed Jani Poutiainen / FMI with Hannu Talvitie / Vaisala
Wind profiler
RASS
Sodar
Ceilometers
Doppler lidar
POSS
Not included: weather radars

2. Wind Profiler at Malmi Airport
LAP-3000 wind profiler (8/ /2006)
RASS for virtual temperature profiling (10/ /2006)
Remote access from Vaisala (Boulder and Vantaa) and FMI
Pulse Doppler RAdio Detection And Ranging device
Transmission pulse of electromagnetic energy with target backscattering.
The profiler computes height by using the time interval between transmission of the pulse and reception of the return signal.
Wind speed and direction are obtained with Doppler principle, i.e. wave will shift in frequency because of the motion of the target relative to the observer.
Maximum backscattering power occurs when atmospheric irregularities are about half the size of the radar wavelength (Bragg scatter).
– perturbance in refractive index
– backscatter from hydrometeors
Local horizontal uniformity of the wind field is assumed.
For detailed info, see:

3. VAISALA LAP3000 SPECIFICATIONS
Operating frequency MHz
Minimum height m
Maximum height 2-5km
Range resolution 60, 100, 200, 400m;
Testbed configuration 102m
Wind speed accuracy <1 m/s
Wind direction accuracy <10 °
Averaging time minutes
RF power output W peak
Antenna Electrically steerable micropatch phased-array panels
Aperture m2 (4 panels)
Direction Zenith and ±15,5º from zenith in orthogonal directions
Beamwidth ~9º
MTBF 40,000 hours
Other operating frequencies 915, 920, 924, 1280, 1299, MHz

4. Approaching low pressure system
Sea breeze

5. Effects on profiler range performance
Dependence on atmospheric conditions.
Rapid and significant changes.
Affecting conditions: humidity, turbulence, precipitation, high winds and temperature.
Dependence on ground/sea clutter environment, available radio frequency emission bandwidth, aircrafts and birds.
Vertical profiles of mean availability for the wind measurements at various sites (Dibbern et al., 2003)

6. Radio acoustic sounding system (RASS)
Profiles of virtual temperature, i.e. temperature uncompensated for humidity or pressure.
Continuous acoustic sine wave synchronized to RADAR frequency, about 2.6 kHz (half wavelength).
Acoustic wave acts as an artificial target.
Profiler receives resulting backscatter and effectively measures the speed of sound.
Sound speed is related to air temperature thus temperature information can be calculated.
Profiler gathers wind velocity data for the largest portion of an averaging period and virtual temperature data for the remaining portion. In Testbed configuration, typically 27 min for wind and 3 min for temperature measurement.
Strong winds may transport the acoustic signal away from vertical alignment.
Atmosphere absorbs the acoustic signal, much determined by temperature, humidity and pressure.
Frequency kHz
Minimum height m
Maximum height km
Range resolution 60, 100, 200, 400m
In Testbed conf: lowest range 149 m, up to m, step 62 m
Temperature accuracy 1 °C
Averaging time minutes
Sound pressure 1 m above transducer 132 dB
Aperture m2 (4 sources)

7. Data examples Descending inversion
Approaching cloud deck first warms upper layer (above 250 m) until cooling finally starts with clearing (17:30).
At the same time, closer to ground ( m) cooling takes place with northerly winds.
Descending
inversion

8. Sodar model: REMTECH PA1 Location at Malmi, 08-11/2006
Panu Maijala
VTT
Sodar model: REMTECH PA1
Location at Malmi, 08-11/2006
Emission of acoustic pulse and detection of echo Doppler frequency shift. Echo signal relates to thermal turbulence in the atmosphere.
Sounds like a bird singing
Linux based measurement system
Number of elements
Type of elements
Nominal central operating frequency (Hertz) 9 (up to 15 optional) frequencies are emitted on each tilted beam during one «beep» Antenna size (meters) (Supporting structure not included) Antenna weight including supporting structure Acoustic Power
Maximum range
Average range in typical conditions  52
Motorola/Remtech
2250
0.65 x 0.65
25 Kg
1 W
2000 m
1300 m

9. Ceilometers in the Testbed domain
7 pcs of CT25K (FMI)
Cloud heights and amounts
6 pcs of CL31
Cloud heights, amounts and backscatter profile
Nurmijärvi, Röykkä
Mäntsälä, Purola
Porvoo, Tirmo
Helsinki, Vallila
Vantaa, Vantaanlaakso
Helsinki, Malmi

10. Vaisala CL31 Measurement range 0 ... 7.5 km
Measurement resolution 10 m or 5 m
Reporting interval s, selectable
Measurement interval 2 s default; 16 s in Testbed configuration
Laser source Indium Gallium Arsenide (InGaAs) Diode Laser
Center wavelength ± 10 nm at 25 °C
Operating Mode Pulsed
Nominal pulse properties at full range measurement:
Energy μWs ± 20%
Peak power 11 W typical
Width, 50% ns typical
Repetition rate kHz
Average power mW
Max Irradiance μW/cm² measured with 7 mm aperture
Beam divergence ±0.4 mrad x ±0.7 mrad
Measurement of cloud height and amount, or vertical visibility. And backscatter profile.
LIDAR technology (LIDAR = Light detection and ranging).
Laser pulses are sent out in a vertical or near-vertical direction.
The backscatter is caused by haze, fog, mist, virga, precipitation and clouds.
Knowing light speed and time delay between the launch and the detection of signal gives cloud base.
Transmitter
Receiver
Mirror
Lens

11. Mixing height estimation and Testbed-data
Noora Eresmaa
FMI
Mixing height estimation and Testbed-data
CL31-ceilometers
The 2-step algorithm is under development
An idealized backscattering profile B(z) is fitted to the measured profile by the formula
zSL corresponds to the lower mixing layer (Step1); zML to the upper one (Step2).
An example of the ceilometer profile fitting (15 April 2006 at 10:00 UTC in Vallila, Helsinki)

12. Multiple aerosol layers on 16.3.2006

13. Ground fog measurement with Vaisala Ceilometer CL31
Christoph Münkel
Vaisala
Ground fog measurement with Vaisala Ceilometer CL31
Strong and clearly structured signal from ground fog patches.

14. Doppler lidar – University of Salford & Halo photonics
Karen Bozier
Univ. of Salford
Doppler lidar – University of Salford & Halo photonics
Atmospheric backscatter and vertical wind velocity measurement. Measurements of the eddy dissipation rate and the integral length scale of turbulent eddies.
Construction: optical base unit, the weather-proof antenna and the signal processing and data acquisition unit.
Selectable parameters such as the length of the range gate, maximum range and number of pulses accumulated for each measurement and the spectral resolution.
Investigation of the day-night boundary layer transition.
Parameters Description/Value
Operating wavelength mm
Pulse Repetition Frequency 20 kHz
Energy per pulse 10 mJ
Beam divergence 50 mrad ~ 5cm at 1 km
Range gate 30 m
Minimum range 30 m
Maximum range up to 7 km dependant on atmospheric conditions
Temporal resolution 0.1 – 30 s

15. 9th August 2006 between 10:40 – 11:00 UTC.
Karen Bozier
Univ. of Salford
Top panel shows the atmospheric backscatter and the bottom panel shows vertical velocity data, negative velocities are downward motion and positive velocities are upward motion. The top panel shows that a higher backscatter layer from the ground up approximately 300 m. Correlation between the two panels shows that the convective up draughts are lofting the aerosol into the clearer air as the boundary layer develops during this time period. The lidar backscatter signal was exceptionally high due to the smoke plume from the Russian forest fires being advected over Southern Finland on 9th August The smell of smoke/burning was strong at Malmi airport during this time period and visibility was reduced by the haze. Black areas are where the signal was below the noise level and the data have been removed.
9th August 2006 between 10:40 – 11:00 UTC.

16. The picture above shows modeled distribution of particulate matter concentrations on the August 9th 2006 at 09:00 UTC (source: The unit in the given color scale is µg/m3. The picture below presents ceilometer Vaisala CL31 backscatter profiles at Helsinki Malmi site on the same day (08:57-09:03 UTC).

17. POSS – Precipitation occurrence sensor system
Järvenpää 12/05-
Malmi 12/05-05/06
Jokioinen 06/06-
Customs declaration until 11/08, Communications Regulatory Authority permission for extension in process.

18. Kenneth Wu
Met Service Canada
Precipitation detection
Type identification (dominant type): Drizzle ( L), Rain (R), Snow (S), Hail (A), Indeterminate ( P)
Intensity and rate estimation: Very light (-- ), Light ( - ), Moderate ( ), Heavy ( + )
Rain drop size distribution (DSD)
Doppler shifted frequency is proportional to the velocity component in the boresight of the antenna.
Mean power of the Doppler signal depends on: raindrop size, antenna pattern, transmitter power and window transmission losses.
Both amplitude and frequency from a single particle vary as it passes through the measurement volume.
Microwave ( GHz, 3cm) CW Doppler bi-static radar
43 mw nominal output power
Measurement range approx. 2 m
Measurement volume 30 m3
Heated TX/RX window with bird deterrent
Maximum total power consumption: 200W
Operates under all weather conditions