Dust Event Assessment for the Atacama Desert using Surface Synoptic Observations: 1984 - 2021

The Atacama Desert should be a region prone to wind erosion and dust events given the barren landscape and lack of moisture but it rarely sees strong dust events. Despite this perception, there is no literature quantifying the frequency of dust events in the Atacama and analysing the underlying meteorological mechanisms responsible for dust storms in the region. To this end, we analysed surface observations spanning 37 years (1984-2021) to compile wind climatology and systematically assess the dust events in the Atacama Desert. We used the Met Office Integrated Data Archive System (MIDAS) Land and Marine Surface Stations Data. Based on the present weather codes for nine Chilean stations present in the data, frequency of dust events was computed. The Atacama Desert has a very low annual mean dust event frequency of 0.6% despite its hyper-aridity. The station at Chañaral records the highest number of dust events, accounting for 68% of all recorded dust observations. There is no perceptible seasonal pattern but there is a strong diurnal cycle in the dust activity in the Atacama as most dust events occur between 1500 and 1800 local time. Threshold wind speeds, defined as the minimum wind speed required for 5, 25 and 50% of dust event frequency, are estimated for all stations except at Vallenar. The thresholds allow us to determine the lowest winds capable of emitting dust from the surface and also the highest wind speeds required, and the differences between the thresholds is indicative of the changes in soil conditions such as soil moisture or land use. For 5% of dust event frequency, the lowest threshold wind speed of 6-8 ms^-1is estimated at Chañaral and for 50% of dust event frequency, 10-12 ms^-1at Desierto de Atacama. Higher threshold wind speeds are observed for stations north of 26°S than the stations south of 26°S. It implies that dust particles can be mobilized by weaker near-surface wind speeds in the South than in the North of the Atacama. Seasonal variations in the threshold wind speed are not strongly pronounced in stations where sufficiently many observations are available. Ongoing work includes incorporating additional datasets for filling in identified data gaps in MIDAS and for allowing a spatially broader analysis of dust-emitting winds across the Atacama Desert.