Determination of Region of Influence Obtained by Aircraft Vertical Profiles Using the Density of Trajectories from the HYSPLIT Model

Abstract

Aircraft atmospheric profiling is a valuable technique for determining greenhouse gas fluxes at regional scales (104–106 km2). Here, we describe a new, simple method for estimating the surface influence of air samples that uses backward trajectories based on the Lagrangian model Hybrid Single-Particle Lagrangian Integrated Trajectory Model (HYSPLIT). We determined “regions of influence” on a quarterly basis between 2010 and 2018 for four aircraft vertical profile sites: SAN and ALF in the eastern Amazon, and RBA and TAB or TEF in the western Amazon. We evaluated regions of influence in terms of their relative sensitivity to areas inside and outside the Amazon and their total area inside the Amazon. Regions of influence varied by quarter and less so by year. In the first and fourth quarters, the contribution of the region of influence inside the Amazon was 83–93% for all sites, while in the second and third quarters, it was 57–75%. The interquarter differences are more evident in the eastern than in the western Amazon. Our analysis indicates that atmospheric profiles from the western sites are sensitive to 42–52.2% of the Amazon. In contrast, eastern Amazon sites are sensitive to only 10.9–25.3%. These results may help to spatially resolve the response of greenhouse gas emissions to climate variability over Amazon.

Amazonia as a carbon source linked to deforestation and climate change

“…The eastern sites are sensitive to more deforested and degraded land, and are also influenced by the Cerrado and Caatinga biomes. The western sites are sensitive to more preserved areas and have a higher representativity of Amazonia 43 . TAB_TEF represents a pristine area with much fewer biomass burning events.…”

“…2c). We developed a method 43 that uses individual back-trajectories for each sample in each VP, calculated by the HYSPLIT trajectory model 42,45 at a resolution of 1 h using 1° × 1° GDAS meteorology. For each site, all the back-trajectories in a quarter ( January, February and March; April, May and June; July, August and September; October, November and December) or the whole year are binned, and the number of instances (at 1 h resolution) of back-trajectories between 300 to 3,500 m a.s.l.…”

“…1, limited to just the Amazon mask, and Extended Data Fig. 2c) were determined by averaging the nine annual regions of influence for each site, using the sum of the number of points (frequency) within each grid cell integrating all VPs in the year (24 VPs per site) and then averaging over all nine years 43 .…”

“…2a, b, limited to the Amazonia mask). There are seasonal differences in circulation patterns, where the first and fourth quarters receive contributions from the Northern Hemisphere when the Intertropical Convergence Zone lies below the Equator, and in the second and third quarters when air masses always have origins south of the Equator, producing important differences in the regions of influence throughout the year 43 .…”

Hospitalization Due to Fire-Induced Pollution in the Brazilian Legal Amazon from 2005 to 2018

“…The wind analysis follows the patterns presented by Gatti et al [72] and Cassol et al [73] for the Amazon region, including the dispersion of aerosols, in which there is a change in the predominant wind direction at the beginning of the fire season. This factor can spread smoke plumes to neighboring municipalities, states, and even other Amazonian countries, representing a transboundary issue exemplified by the study of Sheldon and Sankaran 2017 [7].…”