Similar to the AOS APS and SMPS/nano-SMPS, the Ultra-High Sensitivity Aerosol Spectrometer (UHSAS) is an AOS instrument that principally measures the number concentration of aerosol particles as a function of particle size - the so-called aerosol size distribution. Specifically, the UHSAS measures middle- to large-diameter aerosol particles in the diameter range of 60 to 1000 nanometers (nm) (0.06 to 1.0 micrometers).
The UHSAS uses a relatively high-powered near infrared laser to illuminate the aerosol sample volume and collects and measures the scattered radiation over a large solid angle. Physically, the amount of laser light scattered corresponds strongly with particle size.
As of now, please monitor the a1-level aosuhsas datastreams for all UHSAS DQA assignments. When submitting DQPRs for the UHSAS, please use the UHSAS instrument class under the AOS Group.
The UHSAS is a component instrument within the Aerosol Observing System (AOS). For a more complete overview the AOS system and its general backing measurement theory, please see the AOS DQ Wiki page.
Below is an example of a QC metrics table from a period of acceptable UHSAS instrument system operation. The one primary measurement is outlined in red; all other measurements are diagnostic in nature. That primary field is:
The primary UHSAS measurement is the 2D size distribution of aerosol particles. Here, 2D refers to (time, particle size bin). To visualize this 2D data, we create the following daily contour plot of particle counts within each size bin (increasing along the y-axis) through time (x-axis). Periods characterized by higher aerosol loadings will show up "bright" in these plots. To capture the wide variety of particle sizes and counts routinely measured throughout a given day, note that the y- and z-axes are on log scales.
Note: the seeming step change evident at a diameter of ~250 nm in the size distribution plot below is not actually indicative of an instrument problem and does not need to be noted in your DQAs, etc. Rather, the mentor reports that:
"That’s one of the so-called gain stage boundaries. There are essentially multiple detectors inside the UHSAS to cover the full diameter range and the stitching between them is not always good. It’s probably especially pronounced here with logarithmic scale."
From the 2D aerosol size distribution data, we calculate the total concentration of aerosol particles over all UHSAS particle size bins internally within the DQO. These particle concentration data are then plotted on a daily and weekly basis for direct comparison with particle concentrations measured by other collocated AOS instruments.
We also plot a number of diagnostic fields on a daily and weekly basis for routine "instrument health" monitoring. These include various flow rates, voltages, temperatures and pressures deemed critical to monitoring instrument performance.
The number concentration of aerosol particles is measured by a number of AOS instruments. Whenever possible, these collocated particle concentrations are plotted alongside one another in the following daily and weekly comparison plots. In doing so, we can identify if, for instance, one instrument's particle concentration deviates from the general trend from other instruments and flag the data are suspect accordingly. Note that these particle concentrations are plotted on a log y-axis to accommodate particle concentrations that often vary by orders of magnitude throughout the day.
Aside from the UHSAS, a number of other AOS instruments also measure aerosol particle number size distributions over different particle diameter ranges. Some of these particle diameter ranges overlap with one another. In order to assess how these number size distributions compare across instruments, we create a comparison plot of the daily-mean aerosol particle number size distributions from each collocated AOS instrument. Generally, size distributions from different instruments should overlap one another over aerosol particle diameters that they both scan over.
Note that the usual temporal x-axis has been replaced with aerosol particle diameter (log scale); the daily mean dN / dlogDp number concentration is on the y-axis. The different particle diameters scanned by each instrument should be more apparent in the different instrument traces in this plot (i.e., from very small-diameter nanoparticles with the nano-SMPS to large-diameter coarse mode particles with the APS).
No known behaviors that may not require mention in DQAs exist. Document some here.
No problems that may require mention in DQAs and possibly DQPRs have been documented. Document some here.