Month: November 2023

The notable feature for Thursday was the convergence by day’s end of all three sites at a similar lower level, about 10 ppm above background levels for well-mixed air. Higher than average winds from the north-east may have been a driver.  Please see here for details about the calibration improvements made since Phase 2.  Yesterday’s second figure showed the CO2 concentration in the stack plume from a Taiwanese coal-fired power station – and today’s is a similar plot from a Chinese research collaboration who flew a sensor-equipped drone through the plume from a gas-fired power plant in Shenzhen.

Daily Averages – Phase 3

Daily Averages – Phase 2 (See explanation of differences between Phase 1 and Phase 2 data)

For reference, latest monthly average (July 2023) from CSIRO for Kennaook/Cape Grim in NW Tasmania was 416.6 ppm. (Note – these are provisional values, subject to revision folllowing sensor re-calibrations and other checks.)

Thursday saw the CBD concentrations unusually flat – started and ended low but showing much smaller daytime drop than at the other sites.  Please see here for details about the calibration improvements made since Phase 2.  Today’s second chart shows what happens if you fly a Senseair K30 sensor, as used in this project, through a coal-fired power plant plume (lower left plot in red). See the study by clicking on the image.

Daily Averages – Phase 3

Daily Averages – Phase 2 (See explanation of differences between Phase 1 and Phase 2 data)

For reference, latest monthly average (July 2023) from CSIRO for Kennaook/Cape Grim in NW Tasmania was 416.6 ppm. (Note – these are provisional values, subject to revision folllowing sensor re-calibrations and other checks.)

Average CO2 concentrations were quite similar for the three sites on Wednesday at around 435 ppm.  In the evening, levels at our CBD site (Petrie Terrace) fell slightly towards midnight while Chapel Hill’s values rose.  We will again publish 21-day average profiles once we have sufficient Phase 3 data.  Please see here for details about the calibration improvements made since Phase 2.   At a very different scale, clicking on today’s second figure takes you to an excellent animation of global CO2 over a 16 day period from NASA’s OCO-2 observatory.

Daily Averages – Phase 3

Daily Averages – Phase 2 (See explanation of differences between Phase 1 and Phase 2 data)

For reference, latest monthly average (July 2023) from CSIRO for Kennaook/Cape Grim in NW Tasmania was 416.6 ppm. (Note – these are provisional values, subject to revision folllowing sensor re-calibrations and other checks.)

We have taken the last few weeks to make additional improvements to the calibration and analysis of our sensor data.  This includes a more highly controlled process for a span calibration using an acccurate reference gas at 400 ppm, re-setting each sensor to that level, and then taking measurements of CO2 at incremental concentrations up to 520 ppm.  Separately, we assess the response of each sensor to changes in relative humidity, temperature and air pressure with a constant CO2 concentration so these can be accurately compensated for. Finally, data are now normalised to 20 degrees C and 101.325 hPa  (Normal Temperature and Pressure – NTP), and 50% RH (close to Brisbane’s annual average).  This step improves the comparability of data from sensors in different locations.  Calibration coefficients have been obtained for each individual sensor as they all have slightly different characteristics. 

The data-graphing uses updated analysis code which applies the various coefficients and uses a low pass Butterworth filter to remove the occasional spike artifact.  We’re no longer using the 30 minute averaging which tended to smooth data (but also remove detail) previously.  To distinguish from previously reported data we are labelling this “Phase 3”.  Despite these changes, the overall levels appear to be quite similar to those using the earlier calibrations in previous phases..

Daily Averages – Phase 3

Daily Averages – Phase 2 (See explanation of differences between Phase 1 and Phase 2 data)

For reference, latest monthly average (July 2023) from CSIRO for Kennaook/Cape Grim in NW Tasmania was 416.6 ppm. (Note – these are provisional values, subject to revision folllowing sensor re-calibrations and other checks.)