Subjective Mapping of Dust-Emission Sources by Using MODIS Imagery: Reproducibility Assessment

Accurate dust source characterizations are critical for effectively modeling dust storms and their associated hazards. Walker et al. (2009; W09 henceforth) developed an approach to manually map plume head point sources in a geographic information system (GIS) using Moderate Resolution Imaging Spectroradiometer (MODIS) imagery processed through a dust-enhancement algorithm. With this technique, a location is digitized and archived if an analyst observes an unobscured dust plume head in the imagery. Over the last decade, the W09 method has become a popular approach for identifying dust source activity on a regional scale and is often used as a first-order proxy for dust source observations in data sparse regions.

Because airborne dust must be sufficiently elevated for overland dust enhancement algorithms to work, W09 assume up to 10 km in digitized dust source location error to account for downwind advection and analyst interpretation. For this study we investigated the role of analyst subjectivity on the reproducibility of datasets compiled using the W09 method. Four analysts independently generated active dust source datasets for Southwest Asia following procedures adapted from the W09 approach and five years (2012 – 2016) of MODIS data from 15 May to 31 August. The resulting datasets were then used to quantify the overall mean maximum distance between each analyst’s data point for a given dust plume source. Results were considered reproducible when the mean maximum distance between each analyst markers for a given dust plume source did not exceed 10 km.

This presentation will discuss findings and offer recommendations for data interpretation when using the W09 method for regional scale dust source characterization.

Walker, A. L., M. Liu, S. D. Miller, K. A. Richardson, and D. L. Westphal. 2009. Development of a Dust Source Database for Mesoscale Forecasting in Southwest Asia. Journal of Geophysical Research 114 (D18): D18207. doi:10.1029/2008JD011541.