This is an old revision of the document!
Table of Contents
Ceilometer CT25K
Mentor: S. Steinke.
Principle
A ceilometer measures the cloud base height, i.e. the ceiling in aviation. It is based on the light detecting and ranging (LIDAR) principle, i.e. it sends laser pulses and measures the backscattered light. From travel time the distance of the back scattering object can be determined. From strength and attenuation of the backscattered signal the backscatter coefficient is determined. The instrument identifies cloud bases by the strong increase of the backscatter coefficient. If the lower clouds are transparent it can detect up to three distinct cloud layers. We use the backscatter profile for an estimate of boundary layer height.
Instrument
Current setup at Research Center Jülich on the roof of IEK-8: on the left hand side the RPG HATPRO-TOPHAT, on the right hand side the Vaisala CT25K ceilometer.
Data
<html> <a href=“http://gop.meteo.uni-koeln.de/~hatpro/jue/ceilo/current/index.html” target=“_blank”> <img src=“http://gop.meteo.uni-koeln.de/~hatpro/jue/ceilo/current/bscat.png” width=420> </a> click to enlarge </html>
History
Specifications
See manual section 1.2.6 page 22)
Parameter | Specification |
---|---|
Wavelength | 905 nm |
Pulse Power | 16 W typical |
Pulse energy | 1.6μJ ±20%1) |
Average Power | 8.9 mW |
Pulse Width | 100 ns |
Repetition Rate: | 5.57 kHz |
Range resolution | 50ft = 30m (see here) |
Time resolution | 15sec |
Range | 0…25,000 ft. (0…7.5 km) |
Laser Divergence | ± 0.53×0.75 mrad (edge×diagonal2)) |
Field-of-View Divergence | ± 0.66 mrad |
Telescope diameter | 145mm |
Size | 760 x 280 x 245 mm |
Power Consumption | 365 W |
Weight | 40 kg |