Data accompanying J. Moore and A. D. Jacobson (2015) Seasonally varying contributions to urban CO2 in the Chicago, IL, USA region: Insights from a high-resolution CO2 concentration and δ13C record. Elementa: Science of the Anthropocene

Details about the sampling location and the calibration methods are available in the paper referenced above. In brief, a Picarro G1101-i wavelength scanned-cavity ring down spectrometer was installed on the roof of Scott Hall on the Northwestern University campus in Evanston, IL (N 42 deg 03 min 06.36 sec, W 87 deg 40 min 39.16 sec). The instrument was operated nearly continuously from August 2011 through February 2012.  The air intake for the instrument was located on the rooftop of Scott Hall, ~18 m above street level. The G1101-i was calibrated using two NOAA gas standards with certified CO2 concentrations tied to the WMO scale and δ13C values determined by INSTAAR at the University of Colorado. Check standards were analyzed once or twice daily throughout the sampling period.

COLUMN definitions and units

number: row number

date: date and time file (UTC)

date_local: date and time (Central Daylight Time [UTC -5] or Central Standard Time [UTC -6])

avg_time_60m_DOY: midpoint of sampling interval in DOY (day of year)

CO2_ppm: Hourly averages for atmospheric CO2 concentrations in parts per million (ppm). The hourly averages are calculated from measurements made every 7-8 seconds (450-515 measurements per hour).

delta13C_per_mil: Hourly averages for d13C values for atmospheric CO2 (per mil). d13C values are relative to VPDB. The hourly averages are calculated from measurements made every 7-8 seconds (450-515 measurements per hour).

Tot_CO2_invert_1e4_60m_ppm: 1/CO2_ppm * 10,000

Tot_CO2_60m_err_ppm: 1 sigma standard deviation values for CO2_ppm

delta13C_60m_err_per_mil: 1 sigma standard deviation values for delta13C_per_mil

Tot_CO2_invert_1e4_60m_err_ppm: 1 sigma standard deviation values for Tot_CO2_invert_1e4_60m_ppm

avg.solenoid.valve.state: Hourly average for instrument solenoid state. When the solenoid state is equal to one, ambient air was sampled for the entire hour. When the solenoid state is greater than one, check standard gases were sampled for part of the hour. The data and analysis reported in the paper excluded all hours when check standard gases were sampled during some portion of the hour.

wind_direction: Hourly average wind direction in degrees (360 = north, 0 = calm) as used in the paper. When available, wind direction data were from the Illinois Environmental Protection Agency (IL EPA) station located approximately 1.1 km from the Scott Hall sampling site. For the periods when IL EPA data were not available, wind direction data were from the US National Weather Service (NWS) station at O'Hare International airport. From the paper, "Wind speed and direction data from O’Hare were used to fill the following intervals when the IL EPA site did not collect data: August 1, 2011 until August 9, 2011 at 14:00, and November 4 until December 8 (with the exception of November 28, 15:00 to November 29, 23:59)." Also from the paper, "Wind speed and wind direction data from the NWS were reported in bins of 0.4-0.6 m/s and 10 degrees, respectively. The IL EPA wind direction data were partitioned into the same bins as the NWS data." 

wind_direction_quad: Hourly average wind direction by compass quadrant. The data from the US National Weather Service station at O'Hare International airport includes "calm" conditions or "variable" conditions. NWS “calm” conditions are when wind speeds are less than 1.57 meters per second (3 knots or 3.5 miles per hour). NWS “variable” conditions are when wind direction changes by more than 60 degrees and wind speeds are less than 3.09 meters per second).

wind_speed_m_s: Hourly average wind speed in m/s as used in paper. When available, wind speed data were from the IL EPA station. If IL EPA data were not available, then the data were from the NWS station at O'Hare International airport (see “wind_direction” notes, also column "wind_source"). As described in the paper, wind speed data from the NWS were reported in bins of approximately 0.4-0.6 meters per second. The NWS reports wind speeds of less than 1.57 meters per second (3 knots or 3.5 miles per hour) as 0 (zero).

wind_source: Designates whether the wind direction and speed data for a particular interval are from the Illinois Environmental Protection Agency (IL_EPA) or the US National Weather Service (NWS).

temp_C: Hourly average temperature in degrees Celsius measured at the US National Weather Service station at O'Hare International airport.

dew_pt_C: Hourly average dewpoint in degrees Celsius measured at the US National Weather Service station at O'Hare International airport.

pressure_mb: Hourly average pressure in millibars measured at the US National Weather Service station at O'Hare International airport.

precip_mm: Hourly average precipitation in millimeters measured at the US National Weather Service station at O'Hare International airport. Field contains "NA" for hours with no recorded precipitation. 

conditions: Hourly average conditions (automated qualitative description) measured at the US National Weather Service station at O'Hare International airport.

wd_NWS_deg10: Hourly average wind direction in degrees (360 = north, 0 = calm) from the US National Weather Service (NWS) station at O'Hare International airport. Wind direction data from the NWS were reported in bins of 10°.

ws_NWS_m_s: Hourly average wind speed in meters per second (360 = north, 0 = calm) from the US National Weather Service (NWS) station at O'Hare International airport . 

wd_NWS_quad: Hourly average wind direction by compass quadrant from the US National Weather Service (NWS) station at O'Hare International airport. The NWS defines “calm” conditions as periods when wind speeds are less than 1.57 meters per second (3 knots or 3.5 miles per hour). The NWS defines “variable” conditions as periods when wind direction changes by more than 60 degrees and wind speed is less than 3.09 meters per second).