SMU Atmospheric Observatory
![[SMU Atm. Obs. - SAO]](photos/SAO.jpg)
The SMU Atmospheric Observatory (SAO) is a newly established observatory designed for continuous monitoring of atmospheric trace gases, aerosols, meteorology, and cloud parameters. It comprises an urban Halifax site ~1 km from the coast and an 'Adjunct' site right at the coast in nearby Sandy Cove. Instrumentation at SAO includes:
- Open-Path Fourier Transform InfraRed (OP-FTIR) spectrometer, currently sampling a horizontal two-way path of ~450 m, and recording active IR beam absorption spectra (day and night) of multiple trace gases, including VOCs like formaldehyde, at high temporal (4 min. to average 960 interferograms) and medium spectral resolution (0.5 cm-1) with a sensitivity of ~1 ppb
- Mini Micro Pulse LiDAR (mMPL) deployed at Sandy Cove as part of the Canadian Lidar Network (a part of NASA's Lidar Network), currently probing the atmosphere up to an altitude of 20 km to provide vertical profile measurements of normalized relative backscatter (NRB) and volume depolarization ratio (VDR) to detect aerosols, clouds and their phase (solid vs. liquid)
- PurpleAir sensors at both SAO and Sandy Cove, providing surface aerosol concentration measurements of particulate matter with diameter, D, less than 2.5 micrometers (PM2.5)
- Davis Weather Station, providing meteorological measurements (p, T, RH, wind direction and speed, rain rate, total solar irradiance and UV index)
Reasons to monitor trace gases and aerosols in Halifax and at Sandy Cove:
- Halifax is the second largest Canadian coastal city with regular commercial and military ship presence in the port, which contributes criteria air contaminant emissions equivalent to placing a second automobile fleet on the roads [Wiacek et al., 2017, ACP]
- Shipping in Halifax is increasing, with the marine fleet changing to meet new regulations on fuel sulphur content and NOx emissions, as well as to meet industry decarbonization goals that may increase methane (CH4), methanol (CH3OH), ammonia (NH3) and nitrous oxide (N2O) emissions (all detectable by the OP-FTIR system, along with many other mid-IR active gases)
- SAO provides vital data on shipping-related trace gas and aerosol concentrations, including unique gas species such as ammonia and oxygenated VOCs related to surface ozone and particulate matter production
- Halifax is subject to long-range transported (LRT) air pollution from upstream emission sources. The new observatory serves as an observation site for the newly-funded Canadian mMPL Network (MPLCAN), whose science goals include better tracking transported particulate pollution from anthropogenic sources as well as forest fires and volcanoes.
- SAO is well positioned to provide continuous ground-based measurements suitable for satellite validation and long-term trend analysis