Abstract
Abstract. To improve dust storm identification over the western United States, historical dust events measured by air quality and satellite observations are analyzed based on their characteristics in data sets of regular meteorology, satellite-based aerosol optical depth (AOD), and air quality measurements. Based on the prevailing weather conditions associated with dust emission, dust storm events are classified into the following four typical types: (1) The key feature of cold front-induced dust storms is their rapid process with strong dust emissions. (2) Events caused by meso- to small-scale weather systems have the highest levels of emissions. (3) Dust storms caused by tropical disturbances show a stronger air concentration of dust and last longer than those in (1) and (2). (4) Dust storms triggered by cyclogenesis last the longest. In this paper, sample events of each type are selected and examined to explore characteristics observed from in situ and remote-sensing measurements. These characteristics include the lasting period, surface wind speeds, areas affected, average loading on ground-based optical and/or air quality measurements, peak loading on ground-based optical and/or air quality measurements, and loading on satellite-based aerosol optical depth. Based on these analyses, we compare the characteristics of the same dust events captured in different data sets in order to define the dust identification criteria. The analyses show that the variability in mass concentrations captured by in situ measurements is consistent with the variability in AOD from stationary and satellite observations. Our analyses also find that different data sets are capable of identifying certain common characteristics, while each data set also provides specific information about a dust storm event. For example, the meteorological data are good at identifying the lasting period and area impacted by a dust event; the ground-based air quality and optical measurements can capture the peak strength well; aerosol optical depth (AOD) from satellite data sets allows us to better identify dust-storm-affected areas and the spatial extent of dust. The current study also indicates that the combination of in situ and satellite observations is a better method to fill gaps in dust storm recordings.
Highlights
The western United States is an important source of global mineral dust emissions (Woodward, 2001; Tanaka and Chiba, 2006)
With reference to the US Environmental Protection Agency (EPA) National Ambient Air Quality Standards (NAAQS), the daily averaged concentration of PM10 is above the suggested limit in the case of the dust storms (D2) caused by meso- to small-scale weather systems
In order to improve dust storm identification over the western United States, a collection of dust storm events measured by air quality and satellite observations is analyzed based on characteristics in meteorological data, satellite aerosol optical depth (AOD) retrievals, and air quality data sets
Summary
The western United States is an important source of global mineral dust emissions (Woodward, 2001; Tanaka and Chiba, 2006). Dust storms have seriously affected the western US and beyond in recent decades. Detailed reports on historical events trace back to the 1930s (Schubert et al, 2004). Main observing networks over the western US have included or collected airborne dust in their records or samples. Near-surface dust has been quantitatively sampled and tested for total aerosol mass concentrations by the Interagency Monitoring of Protected Visual Environments (IMPROVE) network and the US Environmental Protection Agency (EPA) Air Quality System (AQS). The optical properties of dust weather events are recorded in aerosol optical depth (AOD) measurements by the Aerosol Robotic Network (AERONET) (Holben et al, 1998).
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