Greater Toronto Area (GTA) ACES mobile surveys 2023

Authors: Sebastien Ars, Lawson Gillespie, Aggrey Sambay and Felix Vogel

Please use the dataset's DOI or contact sebastien.ars@ec.gc.ca if you want to use these datafiles for scientific purposes. 

	These datafiles contain observations collected with the Atmospheric Composition and Environmental Survey (ACES) platform during a series of mobile surveys in the Greater Toronto Area in 2023. Each file contains calibrated data from a LI-COR LI-7810 and from an Airmar 220-WX weather station. The LI-COR LI-7810 measures atmospheric CH4, CO2 and H2O mole fractions and the Airmar 220-WX measures weather conditions (air temperature, atmospheric pressure, wind conditions) and GPS coordinates. 
	
	Both instruments output data to a single logging computer every second and their data are associated with a computer timestamp when received. These timestamps are used to create the merged datasets included in this archive. A time correction was applied to the LI-COR LI-7810 measurements to account for the inlet delay. 

	These datasets are ASCII text files. Missing variables are represented by the string "nan" variables are separated by commas (","), and lines are separated by "\n". The first line in the datasets contain a header labelling the variables. 

Variables included in these dataset:
gps_time- Time of GPS embedded within the Airmar. This time is reported in the following format, YYYY-MM-DD hh:mm:ss.sss in UTC.
alt- Altitude of the Airmar in meters above sea level from the GPS.
amb- Ambient air temperature measured by the LI-COR in degrees Celsius.
ch4- Ambient air CH4 mole fraction in parts per million measured by the LI-COR.
ch4d- Ambient air CH4 dry air mole fraction in parts per million measured by the LI-COR. This measurement is based on the CH4 and H2O mole fractions, and cavity air temperature and pressure measured by the LI-COR.
co- Ambient air CO mole fraction in parts per million measured by the LI-COR.
co2- Ambient air CO2 mole fraction in parts per million measured by the LI-COR.
co2d- Ambient air CO2 dry air mole fraction in parts per million measured by the LI-COR. This measurement is based on the CO2 and H2O mole fractions, and cavity air temperature and pressure measured by the LI-COR.
cod- Ambient air CO dry air mole fraction in parts per million measured by the LI-COR. This measurement is based on the CO and H2O mole fractions, and cavity air temperature and pressure measured by the LI-COR.
cog- Course over ground in degrees from True North measured by the Airmar's GPS.
gasp- Gas pressure in the LI-COR cavity in kPa. This variable is intended for quality control of the LI-COR measurements and should be near 39.6 kPa.
h2o- Ambient air H2O mole fraction in parts per million measured by the LI-COR.
hdop- Horizontal dilution of position of the GPS fix taken by the Airmar. This is a measure of how satellite geometry affects the accuracy of the GPS fix taken by the Airmar.
heading- Direction in which the front of the observatory points in degrees from True North measured by the Airmar.
lat- Latitude of the observatory in decimal degrees based on GPS data. Positive values indicate degrees North of the Equator
lon- Longitude of the observatory in decimal degrees based on GPS data. Positive values indicate degrees East of the Prime Meridian.
pressure- Ambient air pressure measured by the Airmar in hPa.
rd1- Ringdown time of the laser used in the cavity ringdown spectrometer in the LI-COR to measure CH4, CO2 and H2O. This variable is intended for quality control of the LI-COR measurements and should be near 12.6 microseconds.
rd2- Ringdown time of the the second laser of the analyzer when applicable.
sog- Speed over ground in kilometres per hour measured by the Airmar's GPS.
t- Cavity temperature of the LI-COR in degrees Celsius. This variable is intended for quality control of the LI-COR measurements and should be near 55 degrees Celsius.
temp- Ambient air temperature measured by the Airmar in degrees Celsius.
wd_corr- Wind direction relative to ground in degrees from True North measured by the Airmar. This variable is based on the wind velocity relative to the Airmar and an internal vector correction by the instrument using its measured velocity relative to ground and heading. 
wd_uncorr- Wind direction relative to the front of the observatory measured by the Airmar.
ws_corr- Wind speed relative to the ground in meters per second measured by the Airmar. This variable is based on the wind velocity relative to the Airmar and an internal vector correction by the instrument using its measured velocity relative to ground and heading. 
ws_uncorr- Wind speed relative to the Airmar in knots measured by the Airmar.
