A Global Climatology of Wildfire Smoke Injection Height Derived from Space-based Multi-angle Imaging

Maria Val Martin, Ralph A. Kahn, and Mika G. Tosca

Remote Sensing; 10, 1609; doi:10.3390/rs10101609

Summary:

The Multi-angle Imaging SpectroRadiometer (MISR) aboard the NASA Earth Observing System’s Terra satellite offers several unique products relating to airborne particles. Among these is the hyper-stereo-derived heights and associated wind vectors for wildfire smoke, desert dust, and volcanic ash plumes. Results are obtained near-source, where features in the plume can be identified in the multi-angle imagery, and the elevations of particles can be mapped at 1.1 km horizontal resolution, and between 250 and 500 m vertical resolution. Mapping aerosol plume heights with reasonable confidence is a labour-intensive process. Using the MISR INteractive Explorer (MINX) software, a user must identify the location of the source and boundary of each plume within the digital imagery, and must specify the apparent wind direction. MINX then calculates and maps out both the zero-wind and the wind-corrected height of plume elements, and generates related plots and statistics.

This paper presents an analysis of over 23,000 globally distributed wildfire smoke plume injection heights from MISR, stratified by region, biome, and month or season. Both pixel-weighted and aerosol optical depth (AOD)-weighted results are included. The main limitation of the data presented is that the satellite is in a sun-synchronous orbit, crossing the equator at about 10:30 local time on the day side, so diurnal coverage is lacking. Despite this limitation, the results offer a unique observational resource for assessing first-principle plume-rise modeling, and can provide some constraints on smoke dispersion modeling for climate and air quality applications.

Injection height matters because aerosol that is injected higher into the atmosphere is likely to stay aloft longer, travel further, and have a broader environmental impact. As such, the work presented represents Phase 2 of the AeroCom modeling community’s Biomass Burning experiment, aimed at improving the initialization of wildfire smoke plumes in aerosol transport models used for air quality and climate prediction.

Overall, plumes occur preferentially during the northern mid-latitude burning season, and the vast majority inject smoke near-surface. However, the heavily forested regions of North and South America, and Africa produce the most frequent elevated plumes and the highest AOD values; some smoke is injected to altitudes well above 2 km in nearly all regions and biomes. The MISR plume heights have already been used to validate and/or constrain aerosol transport models in several studies (e.g., Vernon et al., 2018; Zhu et al., 2018), and with the publication of this paper, it is likely that the larger AeroCom group of modelers will take advantage of this new resource as well.