Long-term aerosol measurements of the Alphasense OPC-N3 in arctic regions: Sensor performance and corrections

With the decrease of electronic component prices, powerful yet low-cost optical particle counters (OPCs) gain in popularity and are frequently used in citizen science as well as classical science projects. The application of OPCs in large numbers can yield higher spatial resolution and, thus, offers great opportunities for studies of spatial distribution and development, e.g. of dust or air pollution. As a consequence, sensor performance and long-term accuracy must be evaluated in order maintain data quality.

During the HiLDA campaign, a measurement campaign focused on Arctic dust emission, we deployed seven measurement stations at Arctic locations (Jan Mayen, Northern and Southern Iceland, Southern Svalbard, North West Norway, South East Greenland, Faroe Islands). Each station was equipped with a compact weather station and four Alphasense OPC-N3 low-cost OPCs, among others. Data was collected for different periods of one to over three years between 2020 and 2025.

During the deployment under occasionally severe weather conditions, most of the sensors age significantly, which was to be expected at the time of deployment. Therefore, of the four instruments at each station, only one system was operated permanently, while a second one was switched on every week for a short time period to allow for a detection of this aging. The other two served as spare, which were used when the continuously running system was deemed to be degraded. The findings from a total of 28 low-cost OPCs are presented. We observed a combination of continuous aging due to soiling and sudden degradations, probably linked to single extreme events. We present a correction scheme for the continuous aging and point out quality markers for the degradation, as well as observed instrument variation. This information can be used to develop adapted measurement strategies and yield an overall increased data quality.