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 Organization

NO 27
Acronym HKO
Name Hong Kong Observatory
Address 1
Address 2 Hong Kong Observatory
Address 3 134A Nathan Road, Kowloon, Hong Kong.
Country/Territory Hong Kong, China
Website http://www.hko.gov.hk

 Contact(s)

Name W.H. Leung
Prefix Mr.
Email whleung@hko.gov.hk
Organization No 27
Organization acronym HKO
Organization name Hong Kong Observatory
Organization country/territory Hong Kong, China
Address 1
Address 2
Address 3
Country/territory Hong Kong, China
Tel +852 2926 8421
Fax +852 2375 2645
Last updated date 2021-10-18


Name David H.Y. Lam
Prefix Dr.
Email dlam@hko.gov.hk
Organization No 27
Organization acronym HKO
Organization name Hong Kong Observatory
Organization country/territory Hong Kong, China
Address 1
Address 2
Address 3
Country/territory Hong Kong, China
Tel +852 2926 8024
Fax +852 2375 2645
Last updated date 2021-10-18


 Background observation
 UTC+08:00
 ppm
 2009-05-01 00:00:00 - 2010-10-31 23:59:59: NIST
 2010-11-01 00:00:00 - 2021-02-26 23:59:59: WMO CO2 X2007
 2021-02-27 00:00:00 - 9999-12-31 23:59:59: WMO CO2 X2019
 9999-12-31 00:00:00 - 2020-10-31 23:59:59: LI-820 from LI-COR Biosciences Ltd.(NDIR)
 2020-11-01 00:00:00 - 9999-12-31 23:59:59: LI-850 from LI-COR Biosciences Ltd.(NDIR)
 9999-12-31 00:00:00 - 9999-12-31 23:59:59: 4 (m)
 1 second
 The LI-820/LI-850 CO2 analyzer is calibrated once every two weeks (based on past experience of the stability of the analyzer; the zero drift as well as the overall system drift is less than 2 ppm in two weeks' time). During the calibration, secondary standard gases of concentration ~400 ppm and ~600 ppm are used for performance check and span calibration of the LI-820/LI-850 respectively. Before the calibration of LI-820/LI-850, the secondary gases are checked for any drift using a LI-7000 CO2 analyzer which is calibrated using the NOAA standard gases.

Before the calibration, the LI-820/LI-850 is checked for its performance using the ~400 ppm secondary standard gas and a zero gas.
1. The ~400 ppm standard gas is applied to check for any instrument drift;
2. The zero gas is applied to check for any zero drift;
3. The measured data from steps (1) and (2) are kept for future ref.;
4. Due to the limitation of LI-820/LI-850, only the zero and span calibration are carried out;
5. The LI-820/LI-850 is set zero using the zero gas and then the span point is set using the ~600 ppm secondary standard gas;
6. Finally, the performance of LI-820/LI-850 at around 400 ppm is checked using the ~400 ppm secondary standard gas and the data is kept for future reference.
 1. 1-minute average CO2 concentration is calculated from 60 1-second data once every minute;
2. The time series of the raw 1-minute average CO2 concentration is first examined manually to identify any suspicious/erroneous data. Erroneous data are not used for compilation of the hourly and daily mean.
3. Hourly mean CO2 concentration is derived from the 1-minute average;
4. Daily mean CO2 concentration is derived from the hourly mean.
 [Hourly] Please refer to the "data processing" section
 [Daily] Please refer to the "data processing" section
 [Monthly] Monthly mean are derived from the daily mean
 0: Background data
1: Data possibly affected by pollution
2: Insufficient number of averaging data
3: Invalid data
 Valid (background): 0 
 Valid: 1
 Valid: 2
 Invalid: 3
 Operational/Reporting
 Since May 2009 up to 31 October 2020, instrument used for measuring carbon dioxide concentration was LI-820 from LI-COR Biosciences Ltd. Carbon dioxide concentration in ambient moist air was measured and reported.

From 1 November 2020 onwards, a new instrument, LI-850, also from LI-COR Biosciences Ltd., has been employed to measure carbon dioxide concentration. This sensor measures carbon dioxide as well as water vapour concentration in air, thereby making moisture correction possible through simple post-processing of the data. Carbon dioxide concentration in dry air has been reported from 1 November 2020 onwards.
 Wind direction:
 Wind speed:
 Relative humidity:
 Precipitation amount:
 Air pressure:
 Air temperature:
 Dew point temperature:
 Sea water temperature:
 Sea surface water temperature:
 Sea water salinity:
 Sea surface water salinity:
Meteorological data may remain as first provided, even when greenhouse gas data are updated.