Phoenix Dust Storm (PHX-DUST) Scale: A Cooperatively Developed Dust Storm Scale for Phoenix, Arizona

Abstract Using extensive localized meteorological and air quality data for central Arizona from 2010 to 2023, we create a post-event dust storm scale for use by the primary stakeholders in central Arizona for the Phoenix Metropolitan Area called the PHX-DUST Scale. To ensure usability across a wide spectrum of users, a core concept was to ‘keep it simple.’ The PHX-DUST Scale is based on (a) maximum dust concentration for PM10 across the network in μg m-3 which determines category, e.g., ‘Category Five (the highest observed category), ‘Category Four, etc., (b) the number of network monitors achieving dust concentrations above a threshold of 500 μg m −3 (categorized as ‘widespread’ or ‘isolated’, as measures of spatial extent), (c) a duration parameter (which determines ‘long-duration’ or ‘short-duration’), and (d) a measure of wind speed over the affected area (maximum wind gust recorded over the network, which may not be the maximum wind of the storm). Using this index for the 189 dust storms impacting the Phoenix Metropolitan Area for the period 2010-2023, the most severe dust storm occurred on 5 July 2011 and is classified as a ‘Category 5 Widespread Long-Duration High-Gust’ event. This initial attempt at defining the PHX-DUST Scale holds valuable applications for research, education, and applied analyses. It demonstrates that a consortium of interested groups can effectively work to create products benefiting the weather community and general public. The PHX-DUST Scale can also serve as a foundational framework for application in other regions where dust storms pose a threat to the well-being of populations, infrastructure, and ecosystems.