Evaluation of MODIS Dark Target AOD Product with 3 and 10 km Resolution in Amazonia

Abstract

The techniques and analyses employed by remote sensing provide key information about atmospheric particle properties at regional and global scales. However, limitations in optical spectral models used to represent the different types of aerosols in the atmosphere and their effects (direct and indirect) are still one of the major causes of sources of uncertainties and substantial impacts in climate prediction. There are no studies yet in South America, especially in the Amazon Basin, that have evaluated the advantages, disadvantages, inconsistencies, applicability, and suitability of the MODIS sensor (Moderate Resolution Imaging Spectroradiometer) destined for monitoring the ambient aerosol optical thickness over rivers and continents. In this study, the results of the DT (Dark Target) algorithm for products with 3 km and 10 km resolutions were systematically evaluated for six sites in the Amazon rainforest. The comparisons between the products were carried out with the AERONET (Aerosol Robotic Network) measurements, which were used as reference. Statistical parameters between AERONET vs. MODIS were also evaluated based on biomass burning records in the site regions. Here, the DT 10 km product showed satisfactory performance for the Amazon region, with observations between the expected error (EE) limits above 66%, in addition to R > 0.8 and RMSE < 0.3. However, the regional analysis for the two sites in the central and southern regions of the Amazon basin did not have the same performance, where the results showed an EE of 24 and 47%, respectively. The DT 3 km product did not perform well in any site, with an EE below 50%. Both products overestimated the AOD, but the 3 km product overestimated it approximately four times more due to its algorithm setup. Thus, we recommend the 10 km product for general analysis in Amazonia. Regional biomass burning records showed a direct relationship with the AERONET vs. MODIS DT with overestimation of both products. All variations between products and sites were justified based on the difficulty of retrieving surface reflectance and the model selected for local aerosols. Improvements in the optical spectral model currently implemented in the algorithms, with more realistic representations of the main types of the aerosol present in the Amazon Basin, may contribute to better performance among the evaluated products.

Lost in the haze: Persistent mega-fire smoke exposure jeopardizes tree carbohydrate reserves and yield

“…These findings present a novel, yet unrealized threat to agricultural and natural ecosystems related to the impairment of plants' intrinsic capacity to accumulate adequate reserves prior to dormancy, following exposure to severe smoke. The observed impact may extend beyond temperate climatic zones, as the levels of smoke detected in this study were similar to those observed in Amazonia 23 . It is crucial to acknowledge that the reported impacts were only discernible through comparisons of NSC stores over several years across a large geographical area, utilizing hundreds of measurements, underlining the importance and necessity of long-term, largescale observations for understanding such ecological effects.…”

Relationship between El Niño-Southern Oscillation and Atmospheric Aerosols in the Legal Amazon

“…Sites located in the Legal The time series of the AOD 550nm from the AERONET is depicted in Figure 4 for the sites in Alta Floresta, Ji Paraná, and Rio Branco. All sites exhibit a noticeable seasonality during the period spanning from 2006 to 2011, as expected, due to significant emissions resulting from fires that occur during the dry season [28,38]. Sites located in the Legal Amazon region manifest distinct variability characteristics throughout the year, highlighting both a wet season and a dry season.…”

Evaluation of Aerosol Optical Depth (Aod) Estimated by Copernicus Atmosphere Monitoring Service (Cams) in Brazil

“…During the dry season, there is a signi cant increase in average AOD in several regions of the southern Amazon (ROCHA; YAMASOE, 2013), especially in sites that are located in or close to the arc of deforestation, such as Alta Floresta and Ji-Paraná. This substantial increase is mainly attributed to regional emissions resulting from biomass burning, as well as the transport of aerosols from distant areas (Morais et al, 2022;Palácios et al, 2022). In addition, the central region of the Amazon is in uenced by the descending branch of the Hadley cell, which causes dry conditions, favoring the concentration of aerosols in the atmosphere (Rocha; Yamasoe, 2013).…”

“…In this study, priority was given to using level 2.0 data from the AERONET Network, which represents the highest level of quality (Holben et al, 1998). These data are subject to a rigorous quality assurance protocol, including corrections for local factors, guaranteeing their reliability (Palácios et al, 2022). AOD was analyzed for measurements taken at 500 nm.…”

“…AOD is a measure of the extent of solar radiation caused by the presence of aerosols suspended in the atmosphere (Li et al, 2021). Aerosols are microscopic particles, solid or liquid, which can be found naturally in the air or produced by human activities such as the burning of fossil fuels, industrial processes and forest res (Palácios et al, 2022).…”