A ceilometer measures the cloud base height, called 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 caluclating visibility from the backscatter coefficient and identifying the height from which on you cant see the ground any more. If the lower clouds are transparent it can detect up to three distinct cloud layers. In cloud free cases we can use the backscatter profile for an estimate of boundary layer height.
At JOYCE, two different ceilometers are installed. One Vaisala CT25K and one Jenoptik/Lufft CHM15k instrument.
Most of the following data products are provided via the SAMD database. If you would like to have additional data or recent data that have not been uploaded to SAMD yet, please fill the data request sheet and send it to email@example.com
|Dataset||Temporal resolution||File size||Filename||Retrieval / Remarks|
|Uncalibrated attenuated backscatter (background corrected)||15 seconds||1 file per day (30 MB)||sups_joy_ceilo00_l1_beta_v00_YYYYMMDDHHMMSS.nc||from CHM15k, available on SAMD|
|Mixing layer height||15 minutes||1 file per day (0.02 MB)||sups_joy_ceilo00_l2_zmlaa_v01_YYYYMMDDHHMMSS.nc||from CHM15k, available on SAMD|
|Cloud base height||15 minutes||1 file per day (0.28 MB)||sups_joy_ceilo00_l2_zcb_v00_YYYYMMDDHHMMSS.nc||from CHM15k, available on SAMD|
|Backscatter, cloud base height||15 seconds||1 file per day (25 MB)||YYYYMMDD_JOYCE_CHM120109_000.nc||from CHM15k|
|Backscatter, cloud base height||15 seconds||1 file per day (6 MB)||YYMMDD_ct25k_jue_l0b.nc||from CT25K|
Current observations at quicklook archive
At JOYCE, two ceilometers are installed and running continuously. The CT25K has been installed since 2007, while the more powerful CHM15k was added in 2013. Please visit the sub-pages for more details.