Month: June 2023

A relatively low level at Chapel Hill on Thursday in Phase 2 data (see explanation here).  Today’s third graph is from Canada, this time a boreal forest rather than an urban area. Just as in Tokyo’s data (see yesterday’s post), the months of June, July and August show the biggest drops in the early afternoon, again photosynthesis effects the presumed cause, with sufficient mass of vegetation to appreciably lower CO2 levels. Higuchi, K., D. Worthy, D. Chan, and A. Shashkov. ‘Regional Source/Sink Impact on the Diurnal, Seasonal and Inter-Annual Variations in Atmospheric CO ₂ at a Boreal Forest Site in Canada’. Tellus B: Chemical and Physical Meteorology 55, no. 2 (January 2003): 115–25. https://doi.org/10.3402/tellusb.v55i2.16752.

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

For reference, latest monthly average (Apr 2023) from CSIRO for Kennaook/Cape Grim in NW Tasmania was 415.4 ppm. (Note – these are provisional values, subject to revision folllowing sensor re-calibrations and other checks.)

Date	Petrie Terrace	Chapel Hill	Bellbird Park
16-Jun-2023	437 ppm	423 ppm	431 ppm
15-Jun-2023	432 ppm	413 ppm	426 ppm
14-Jun-2023	435 ppm	427 ppm	436 ppm
13-Jun-2023	441 ppm	438 ppm	440 ppm
12-Jun-2023	442 ppm	441 ppm	446ppm
11-Jun-2023	443 ppm	443 ppm	449 ppm
10-Jun-2023	446 ppm	434 ppm	442 ppm
9-Jun-2023	440 ppm	430 ppm	438 ppm

A relatively low level at Chapel Hill on Thursday in Phase 2 data (see explanation here).  Today’s third graph shows data for two sites from a multi-yearstudy of localities in and around Tokyo. Blue indicates values below average, red those above.  Note that the early afternoon values are particularly low in the summer months (the blue patches) – when photosynthesis is most pronounced.  As a sub-tropical city, we don’t expect Brisbane to show such clear-cut seasonal differences.  (Note the time of day effect is similar, though – but time is shown on the y-axis, not the x-axis. Imasu, Ryoichi, and Yuka Tanabe. ‘Diurnal and Seasonal Variations of Carbon Dioxide (CO2) Concentration in Urban, Suburban, and Rural Areas around Tokyo’. Atmosphere 9, no. 10 (October 2018): 367. https://doi.org/10.3390/atmos9100367.

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

For reference, latest monthly average (Apr 2023) from CSIRO for Kennaook/Cape Grim in NW Tasmania was 415.4 ppm. (Note – these are provisional values, subject to revision folllowing sensor re-calibrations and other checks.)

Date	Petrie Terrace	Chapel Hill	Bellbird Park
15-Jun-2023	432 ppm	413 ppm	426 ppm
14-Jun-2023	435 ppm	427 ppm	436 ppm
13-Jun-2023	441 ppm	438 ppm	440 ppm
12-Jun-2023	442 ppm	441 ppm	446ppm
11-Jun-2023	443 ppm	443 ppm	449 ppm
10-Jun-2023	446 ppm	434 ppm	442 ppm
9-Jun-2023	440 ppm	430 ppm	438 ppm

A big fall in levels during the course of Wednesday in Phase 2 data (see explanation here).  How do ground level CO2 concentrations differ across the day compared to well-mixed air at higher altitudes?  Today’s final graph shows concentrations (blue – lower, red – higher) across the day, with the y-axis running from ground level to 400 m, from a large study in Vancouver.  Notice that at higher altitudes there is less variation across the day (all shades of blue), while at ground level (comparable to our sensors) and up to about 100 m, a large red patch emerges after dark and remains until sunrise.  This is the diurnal cycle apparent in our Brisbane data – lowest concentrations in the mid-afternoon – highest concentrations just before dawn.  Crawford, B., A. Christen, and I. McKendry. ‘Diurnal Course of Carbon Dioxide Mixing Ratios in the Urban Boundary Layer in Response to Surface Emissions’. Journal of Applied Meteorology and Climatology 55, no. 3 (1 March 2016): 507–29. https://doi.org/10.1175/JAMC-D-15-0060.1.

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

For reference, latest monthly average (Apr 2023) from CSIRO for Kennaook/Cape Grim in NW Tasmania was 415.4 ppm. (Note – these are provisional values, subject to revision folllowing sensor re-calibrations and other checks.)

Date	Petrie Terrace	Chapel Hill	Bellbird Park
14-Jun-2023	435 ppm	427 ppm	436 ppm
13-Jun-2023	441 ppm	438 ppm	440 ppm
12-Jun-2023	442 ppm	441 ppm	446ppm
11-Jun-2023	443 ppm	443 ppm	449 ppm
10-Jun-2023	446 ppm	434 ppm	442 ppm
9-Jun-2023	440 ppm	430 ppm	438 ppm

Five days into Phase 2 data (see explanation here) and the tendency for the city edge site (Bellbird Park) to have high  nighttime values continues.  (A temporary glitch in the code for averaging across days means resorting to Excel for the second graph, hence the different format.) Why does the CBD site have a smaller range (max for day – min for day) than the other sites?  Over the last five days, this range averages 39 ppm in the CBD, 48 ppm in the middle suburb, and 80 ppm on the city edge.  One possibility is that there are smaller effects of photosynthesis (CO2 absorbing in daylight) and respiration (CO2 emitting in darkness) in the CBD.  The third graph shows a similar smaller range for an urban site (downtown Baltimore) over five years than for a suburban or rural site.  George, K., L. H. Ziska, J. A. Bunce, and B. Quebedeaux. ‘Elevated Atmospheric CO2 Concentration and Temperature across an Urban–Rural Transect’. Atmospheric Environment 41, no. 35 (1 November 2007): 7654–65. https://doi.org/10.1016/j.atmosenv.2007.08.018. This explanation can be tested as we add more monitors to the network.

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

For reference, latest monthly average (Apr 2023) from CSIRO for Kennaook/Cape Grim in NW Tasmania was 415.4 ppm. (Note – these are provisional values, subject to revision folllowing sensor re-calibrations and other checks.)

Date	Petrie Terrace	Chapel Hill	Bellbird Park
13-Jun-2023	441 ppm	438 ppm	440 ppm
12-Jun-2023	442 ppm	441 ppm	446ppm
11-Jun-2023	443 ppm	443 ppm	449 ppm
10-Jun-2023	446 ppm	434 ppm	442 ppm
9-Jun-2023	440 ppm	430 ppm	438 ppm

Early days for Phase 2 data (see explanation here) so not too much should be read into patterns just yet.  Nonetheless, the second graph, averaging the last four days, suggests an apparent difference between daytime and nighttime values at the three sites. The city centre site shows higher carbon dioxide concentrations in daylight hours, and the city edge site has higher values in darkness.  Since comparisons between sites can now be made with much more confidence than was true for Phase 1 data, this reversal will be interesting to track and understand. The addition of more monitoring sites will be crucial to this understanding, to help differentiate between effects that are highly localised and unique, from those that represent the various parts of the urban area robustly.  A feature of the data that has not changed between Phase 1 and Phase 2 is that the overall values are clearly higher than well-mixed air measured for Australia – which averaged 415.4 ppm in April at Kennaook/Cape Grim.  This makes Brisbane’s CO2 levels in the last four days some 26 ppm above that background level.

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

For reference, latest monthly average (Apr 2023) from CSIRO for Kennaook/Cape Grim in NW Tasmania was 415.4 ppm. (Note – these are provisional values, subject to revision folllowing sensor re-calibrations and other checks.)

Date	Petrie Terrace	Chapel Hill	Bellbird Park
12-Jun-2023	442 ppm	441 ppm	446ppm
11-Jun-2023	443 ppm	443 ppm	449 ppm
10-Jun-2023	446 ppm	434 ppm	442 ppm
9-Jun-2023	440 ppm	430 ppm	438 ppm