Smoke Injection Heights from Forest and Grassland Fires in Southwest China Observed by CALIPSO

Smoke injection height (SIH) determines the distance and direction of smoke transport, thus impacting the atmospheric environment. In this study, we used Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations data coupled with Moderate Resolution Imaging Spectroradiometer (MODIS) data and the Hybrid Single-Particle Lagrangian Integrated Trajectory model to derive the SIH values during the peak forest and grassland fire seasons from 2012 to 2017 in Southwest China. The results suggest that the SIH values ranged from 2500 m to 2890 m. An analysis of the dependence of SIH on fire characteristics revealed no obvious correlation between SIH and fire radiative power (FRP) because other factors in addition to FRP have an important impact on SIH. Moreover, MODIS FRP data has a drawback in representing the energy released by real fires, also leading to this result. The topographic variables of forest and grassland fires in Southwest China are very different. Complex topography affects SIH by affecting fire intensity and interactions with wind. A comparison of the SIHs with boundary layer height reveals that 75% of the SIHs are above the boundary layer. Compared with other areas, a higher percentage of free troposphere injection occurs in Southwest China, indicating that smoke can cause air pollution over large ranges. Our work provides a better understanding of the transport and vertical distribution of smoke in Southwest China.

Automated summary

This study used various data sources and models to calculate the smoke injection height (SIH) during peak forest and grassland fire seasons in Southwest China. The results showed that SIH values ranged from 2500 m to 2890 m. The analysis revealed that there was no obvious correlation between SIH and fire radiative power (FRP), suggesting that factors other than FRP also play a significant role in determining SIH. The study also found that topography and wind can affect SIH by influencing fire intensity and interactions. Additionally, a higher percentage of SIHs were found to be above the boundary layer, indicating that smoke can cause air pollution over larger areas in Southwest China.