Differences

This shows you the differences between two versions of the page.

--- ceilo [2020/08/31 16:50] – [Composite products using data from HATPRO] bpospich
+++ ceilo [2022/01/20 22:00] (current) – [Instruments at JOYCE / University of Cologne] bpospich
@@ Line 1: / Line 1: @@
-====== Ceilometer ======
+====== Ceilometer observations ======
 {{:wiki:instruments:ceilo_jenoptik_05.jpg?direct&500|Ceilometer ©B. Pospichal}} \\
@@ Line 7: / Line 7: @@
 ===== Principle =====
 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.
@@ Line 13: / Line 15: @@
   * Vertically pointing observations with integration times of 15 seconds
-  * Vertical resolution 15 m, maximum range 15 km
-  *
 ===== JOYCE-CF Standard Operation Procedures =====
-  * Standard measurement mode is vertically pointing, 1 second integration time
+  * Standard measurement modes are
-  * Every 15 minutes one elevation scan with following angles: 42°, 30°, 19°, 10.2°, 5.4°  (duration ~100 seconds) for improved resolution of temperature profiles in lowest 1000 m above ground
+  * Vertical resolution 15 m, maximum range 15 km  (CHM15k)
-  * Every 30 minutes one azimuth scan at 30° elevation angle with 5° azimuth resolution (duration ~3 minutes) for horizontal variability of IWV and LWP
+  * Vertical resolution 30 m, maximum range 7.5 km  (CT25K)
-===== Data quality assurance procedures =====
-  * Automatic rain detection (data are flagged in case of rain detected by rain sensor)
-  * Offset corrections for liquid water path
-  * O-B statistics from atmospheric models for brightness temperature offset correction available
-  * Spectral consistency checks
-  * Thresholds for Level 2 data products
-  * Housekeeping data analysis
-  * Visual data inspection
 ===== Data availability =====
@@ Line 40: / Line 33: @@
 | 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    |
@@ Line 48: / Line 42: @@
 ===== Link to current observations =====
-Current observations at [[http://gop.meteo.uni-koeln.de/~Hatpro/dataBrowser/dataBrowser4.html?site=JOYCE&date=-1&UpperLeft=Ceilo_ct25k_Backscatter&UpperRight=Ceilo_ct25k_Boundarylayer-height&LowerRight=Ceilo_chm15k_raw&LowerLeft=Ceilo_chm15k_SNR|quicklook archive]]
+Current observations at [[http://atmos.meteo.uni-koeln.de/~hatpro/dataBrowser/dataBrowser4.html?site=JOYCE&date=-1&UpperLeft=Ceilo_ct25k_Backscatter&UpperRight=Ceilo_ct25k_Boundarylayer-height&LowerRight=Ceilo_chm15k_raw&LowerLeft=Ceilo_chm15k_SNR|quicklook archive]]
@@ Line 54: / Line 48: @@
 ===== Measurement examples =====
-{{wiki:examples:tophat_200621_jue_l1.png?direct&400|TOPHAT-TB}}
+{{wiki:examples:200202_ct25k_jue_l0b.png?direct&400|CT25-K}}
-{{wiki:examples:tophat_200621_jue_l2a.png?direct&400|TOPHAT-IWV-LWP}} \\
+{{wiki:examples:20200803_jenoptik_ceilo_snr_version1.png?direct&400|SNR CHM15k}} \\
-//Time series of brightness temperatures (left) and Integrated Water Vapor / Liquid Water Path (right)//
+//Left: Time series from CT25K (backscatter and cloud base height) on 2 February 2020, right: Time series from CHM15k (signal-to-noise ratio plus cloud and aerosol layers) on 3 August 2020 //
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 ^ Instrument name      ^ current location       ^ in operation since          ^  features          ^
 | [[ct25k|Vaisala CT25K]]    | JOYCE    | 2007   |     |
-| [[chm15k|LUFFT CHM15k]]    | JOYCE    | 2013   | Level 2 products are derived from this instrument    |
+| [[chm15k|Jenoptik/Lufft CHM15k]]    | JOYCE    | 2013   | Level 2 products are derived from this instrument    |