Satellite-based view of the aerosol spatial and temporal variability in the Córdoba region (Argentina) using over ten years of high-resolution data

DELLA CECA, L; GARCIA FERREYRA, M.F.; CARRERAS, H; CHUDNOVSKY, ALEXANDRA; LYASPUTIN, A; BARNABA, F

ISPRS JOURNAL OF PHOTOGRAMMETRY AND REMOTE SENSING

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2018

0924-2716

Space-based observations offer a uniqueopportunity to investigate the atmosphere and its changes over decadal timescales, particularly in regions lacking in situ and/or ground basedobservations. In this study, we investigate temporal and spatial variability of atmospheric particulatematter (aerosol) over the urban area of Córdoba (central Argentina) using overten years (2003-2015) of high-resolution (1 km) satellite-based retrievals ofaerosol optical depth (AOD). This fine resolution is achieved exploiting thecapabilities of a recently developed inversion algorithm (Multiangleimplementation of atmospheric correction, MAIAC) applied to the MODIS sensordatasets of the NASA-Terra and Aqua platforms. Results of this investigationshow a clear seasonality of AOD over the investigated area. This is found to beshaped by an intricate superposition of aerosol sources, acting over differentspatial scales and affecting the region with different yearly cycles. During late winter andspring (August-October), local as well as near- and long-range transported biomass burning (BB)aerosols enhance the Córdoba aerosol load, and AOD levels reach their maximum values(> 0.35 at 0.47µm). The fine AOD spatial resolution allowed to disclose that, in thisperiod, AOD maxima are found in the rural/agricultural area around the city,reaching up to the city boundaries pinpointing that fires of local andnear-range origin play a major role in the AOD enhancement. A reverse spatialAOD gradient is found from December to March, the urban area showing AODs 40 to80% higher than in the city surroundings. In fact, during summer, the columnaraerosol load over the Córdoba region is dominated by local (urban andindustrial) sources, likely coupled to secondary processes driven by enhancedradiation and mixing effects within a deeper planetary boundary layer (PBL).  With the support of modelled AOD data fromthe Modern-Era Retrospective Analysis for Research and Application (MERRA), wefurther investigated into the chemical nature of AOD. The results suggest that mineraldust is also an important aerosol component in Córdoba, with maximum impactfrom November to February. The use of a long-term dataset finally allowed apreliminary assessment of AOD trends over the Córdoba region. For those monthsin which local sources and secondary processes were found to dominate the AOD(December to March), we found a positive AOD trend in the Córdoba outskirts,mainly in the areas with maximum urbanization/population growth over the investigateddecade. Conversely, a negative AOD trend (up to -0.1 per decade) is observed allover the rural area of Córdoba during the BB season, this being attributed to adecrease of fires both at the local and the continental scale