Dust Event Assessment for the Atacama Desert using Surface Synoptic Observations: 1984 - 2021
Authors: Pinto Rovina , Fiedler Stephanie 
Published: June 2022

&lt;p&gt;&lt;span&gt;The Atacama Desert should be a region prone to wind erosion and dust events given the &lt;/span&gt;&lt;span&gt;barren landscape and lack of moisture but it rarely sees strong dust events. Despite this perception, &lt;/span&gt;&lt;span&gt;there is no literature quantifying the frequency of dust events in the Atacama and analysing the &lt;/span&gt;&lt;span&gt;underlying meteorological mechanisms responsible for dust storms in the region. To this end, we &lt;/span&gt;&lt;span&gt;analysed surface observations spanning 37 years (1984-2021) to compile wind climatology and &lt;/span&gt;&lt;span&gt;systematically assess the dust events in the Atacama Desert. We used the Met Office Integrated &lt;/span&gt;&lt;span&gt;Data Archive System (MIDAS) Land and Marine Surface Stations Data.&lt;/span&gt; &lt;span&gt;Based on the present &lt;/span&gt;&lt;span&gt;weather codes for nine Chilean stations present in the data, frequency of dust events was &lt;/span&gt;&lt;span&gt;computed. The Atacama Desert has a very low annual mean dust event frequency of 0.6% &lt;/span&gt;&lt;span&gt;despite its hyper-aridity. The station at Cha&amp;#241;&lt;/span&gt;&lt;span&gt;aral records the highest number of dust events, ac&lt;/span&gt;&lt;span&gt;counting for 68% of all recorded dust observations. There is no perceptible seasonal pattern but &lt;/span&gt;&lt;span&gt;there is a strong diurnal cycle in the dust activity in the Atacama as most dust events occur be&lt;/span&gt;&lt;span&gt;tween 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 &lt;/span&gt;&lt;span&gt;Vallenar&lt;/span&gt;&lt;span&gt;. The thresholds allow us to determine the lowest winds capable of emitting dust from &lt;/span&gt;&lt;span&gt;the surface and also the highest wind speeds required, and the differences between the thresholds is indicative &lt;/span&gt;&lt;span&gt;of the changes in soil conditions such as soil moisture or land use. For 5% of dust &lt;/span&gt;&lt;span&gt;event frequency, the lowest threshold &lt;/span&gt;&lt;span&gt;wind speed of 6-8 ms&lt;/span&gt;&lt;sup&gt;&lt;span&gt;-1&lt;/span&gt;&lt;/sup&gt;&lt;span&gt;is estimated at Cha&amp;#241;&lt;/span&gt;&lt;span&gt;aral and for &lt;/span&gt;&lt;span&gt;50% of dust event frequency, 10-12 ms&lt;/span&gt;&lt;sup&gt;&lt;span&gt;-1&lt;/span&gt;&lt;/sup&gt;&lt;span&gt;at Desierto de Atacama. Higher threshold wind speeds &lt;/span&gt;&lt;span&gt;are observed for &lt;/span&gt;&lt;span&gt;stations north of 26&lt;/span&gt;&lt;span&gt;&amp;#176;&lt;/span&gt;&lt;span&gt;S than the stations south of 26&amp;#176;&lt;/span&gt;&lt;span&gt;S. It implies that dust par&lt;/span&gt;&lt;span&gt;ticles can be mobilized by weaker near-surface wind speeds in the South than in the North of the &lt;/span&gt;&lt;span&gt;Atacama. Seasonal variations in the threshold wind speed are not strongly pronounced in stations &lt;/span&gt;&lt;span&gt;where sufficiently many observations are available. Ongoing work includes incorporating addi&lt;/span&gt;&lt;span&gt;tional datasets for filling in identified data gaps in MIDAS and for allowing a spatially broader &lt;/span&gt;&lt;span&gt;analysis of dust-emitting winds across the Atacama Desert.&lt;/span&gt;&lt;/p&gt;