3.7.2. CT25K¶
3.7.2.1. Introduction¶
The CT25K is a ceilometer manufactured by Vaisala. They measure the atmospheric backscatter and can determine cloud heights for multiple layers. Ceilometers work with an invisible eye safe laser that shoots directly upwards into the air. The CT25K is an older version than the CL31. It gives worse results than the CL31.
3.7.2.2. Manufacturer and Model¶
Model |
Brand |
Type |
|---|---|---|
CT25K |
Vaisala |
Ceilometer |
3.7.2.3. Output definitions¶
Ouput definition ID |
File Identifier |
Level Number |
QAQC notes |
File time resolution |
|---|---|---|---|---|
CT25K_BSC |
CT25K-%LETTER_BSC_%SITE |
0 |
30sec |
|
CT25K_BSC |
CT25K-%LETTER_BSC_%SITE |
1 |
30sec |
|
CT25K_CLD |
CT25K-%LETTER_CLD_%SITE |
0 |
30sec |
|
CT25K_CCW30 |
CT25K-%LETTER_CCW30_%SITE |
1 |
15min |
3.7.2.4. Processing code¶
Code used to process raw data: https://github.com/Urban-Meteorology-Reading/Operations-CEIL
3.7.2.5. Variables measured by instrument¶
Variable ID |
Full Name |
Unit |
Lower Threshold |
Upper Threshold |
Files present (Output definition ID,Level No,Time resolution) |
|---|---|---|---|---|---|
beta |
height normalised backscatter |
10-8.m-1.sr-1 |
CT25K_BSC,1,30sec |
||
beta_tR |
smoothed backscatter in height and time |
10-8.m-1.sr-1 |
CT25K_BSC,1,30sec |
||
BG_light |
background light |
mV |
0.0 |
CT25K_CLD,0,30sec |
|
BSC |
height normalised backscatter |
10-8.m-1.sr-1 |
CT25K_BSC,0,30sec |
||
BSC_sum |
sum of detected normalised backscatter |
10-8.m-1.sr-1 |
CT25K_CLD,0,30sec |
||
CBH |
Cloud Base Height |
m |
0.0 |
CT25K_CCW30,1,15min |
|
CC_high |
high cloud amount |
% |
0.0 |
100.0 |
CT25K_CCW30,1,15min |
CC_low |
low cloud amount |
% |
0.0 |
100.0 |
CT25K_CCW30,1,15min |
CC_medium |
medium cloud amount |
% |
0.0 |
100.0 |
CT25K_CCW30,1,15min |
CLD_Height_L1 |
cloud height level 1 |
m a.s.l. |
0.0 |
CT25K_CLD,0,30sec |
|
CLD_Height_L2 |
cloud height level 2 |
m a.s.l. |
0.0 |
CT25K_CLD,0,30sec |
|
CLD_Height_L3 |
cloud height level 3 |
m a.s.l. |
0.0 |
CT25K_CLD,0,30sec |
|
CLD_status |
cloud_detection_status |
dimensionless |
CT25K_CLD,0,30sec |
||
clear |
Percentage of clear sky within time frame |
% |
0.0 |
100.0 |
CT25K_CCW30,1,15min |
contamination |
window contamination |
mV |
CT25K_CLD,0,30sec CT25K_CCW30,1,15min |
||
nSamples |
nSamples |
samples/interval |
CT25K_CCW30,1,15min |
||
pulse |
laser pulse energy |
% |
0.0 |
CT25K_CLD,0,30sec CT25K_CCW30,1,15min |
|
receiver |
receiver sensitivity |
% |
CT25K_CLD,0,30sec CT25K_CCW30,1,15min |
||
SNR |
Signal to Noise Ratio |
dimensionless |
CT25K_BSC,1,30sec |
||
tilt |
tilt angle |
degree |
CT25K_CLD,0,30sec CT25K_CCW30,1,15min |
||
Tlaser |
laser temperature |
Celsius |
CT25K_CLD,0,30sec CT25K_CCW30,1,15min |
||
vis_z |
vertical_visibility |
m a.s.l. |
CT25K_CLD,0,30sec CT25K_CCW30,1,15min |
||
vis_z_max |
maximum visibility |
m a.s.l. |
0.0 |
CT25K_CLD,0,30sec |
3.7.2.6. Serials¶
Serial |
Suffix |
|---|---|
LCBRV045 |
A |
Q |
|
R |
|
S |
|
T |
|
U |
|
V |
|
W |
|
X |
|
Y |
3.7.2.7. Deployments¶
3.7.2.7.1. Serial number: LCBR022¶
Site ID |
Start date |
End date |
|---|---|---|
2016-08-05 00:00 |
2016-08-19 00:00 |
|
2016-08-19 00:00 |
2016-09-02 00:00 |
3.7.2.7.2. Serial number: LCBRV098¶
Site ID |
Start date |
End date |
|---|---|---|
2016-05-25 00:00 |
2018-07-17 00:00 |
3.7.2.7.3. Serial number: LCBRV559¶
Site ID |
Start date |
End date |
|---|---|---|
2015-04-02 00:00 |
2015-06-05 00:00 |
|
2015-06-17 00:00 |
2015-12-31 00:00 |
|
2016-01-01 00:00 |
2020-08-01 00:00 |
3.7.2.7.4. Serial number: LCBRV017¶
Site ID |
Start date |
End date |
|---|---|---|
2016-06-03 00:00 |
2016-06-17 00:00 |
|
2016-06-17 00:00 |
2016-07-01 00:00 |
|
2016-07-01 00:00 |
2016-07-28 00:00 |
3.7.2.7.5. Serial number: LCBRV312¶
Site ID |
Start date |
End date |
|---|---|---|
2016-06-03 00:00 |
2016-07-15 00:00 |
|
2016-07-15 00:00 |
2016-07-28 00:00 |
|
2018-07-17 00:00 |
3.7.2.7.6. Serial number: LCBRV152¶
Site ID |
Start date |
End date |
|---|---|---|
2016-08-05 00:00 |
2016-08-19 00:00 |
|
2016-08-19 00:00 |
2016-10-03 00:00 |
3.7.2.7.7. Serial number: LCBR045¶
Site ID |
Start date |
End date |
|---|---|---|
2016-08-05 00:00 |
2016-09-19 00:00 |
|
2016-09-19 00:00 |
2016-12-02 00:00 |
|
2016-12-15 00:00 |
2017-11-10 00:00 |
3.7.2.7.8. Serial number: LCBR327¶
Site ID |
Start date |
End date |
|---|---|---|
2016-08-05 00:00 |
2016-09-02 00:00 |
|
2016-09-02 00:00 |
2016-09-19 00:00 |
|
2016-09-19 00:00 |
2016-10-03 00:00 |
3.7.2.7.9. Serial number: LCBRV010¶
Site ID |
Start date |
End date |
|---|---|---|
2016-06-03 00:00 |
2016-06-17 00:00 |
|
2016-06-17 00:00 |
2016-07-29 00:00 |
3.7.2.8. Photos¶
3.7.2.9. Supplementary information¶
Link |
Title |
Description |
|---|---|---|
https://www.manualslib.com/manual/1414094/Vaisala-Ct25k.html |
CT25K user manual |
Manual provided by Vaisala. If link has expired please please raise a GitHub Issues. |
3.7.2.10. Data acquisition¶
Data can be requested from Prof. Sue Grimmond (c.s.grimmond@reading.ac.uk).
3.7.2.11. References¶
Theeuwes, N. E., Barlow, J. F., Teuling, A. J., Grimmond, C. S. B. and Kotthaus, S. (2019) Persistent cloud cover over mega-cities linked to surface heat release. npj Climate and Atmospheric Science, 2. 15. ISSN 2397-3722 doi: https://doi.org/10.1038/s41612-019-0072-x
Kotthaus, S., O’Connor, E., M�nkel, C., Charlton-Perez, C., Haeffelin, M., Gabey, A. M. and Grimmond, C. S. B. (2016) Recommendations for processing atmospheric attenuated backscatter profiles from Vaisala CL31 ceilometers. Atmospheric Measurement Techniques, 9. pp. 3769-3791. ISSN 1867-8548 doi: https://doi.org/10.5194/amt-9-3769-2016
Tip
Stuck? the user guide is a useful place to start.
Please report issues at GitHub Issues. Go from the page with the problem - an automatic link will be inserted. Thanks.