African dust particles over the western Caribbean – Part I: Impact on air quality over the Yucatán Peninsula

Abstract

Abstract. On a global scale, African dust is known to be one of the major sources of mineral dust particles, as these particles can be efficiently transported to different parts of the planet. Several studies have suggested that the Yucatán Peninsula could be influenced by such particles, especially in July, associated with the strengthening of the Caribbean low-level jet. Although these particles have the potential to significantly impact the local air quality, as shown elsewhere (especially with respect to particulate matter, PM), the arrival and impact of African dust in Mexican territory has not been quantitatively reported to date. Two short-term field campaigns were conducted to confirm the arrival of African dust on the Yucatán Peninsula in July 2017 and July 2018 at the Mérida atmospheric observatory (20.98∘ N, 89.64∘ W). Aerosol particles were monitored at ground level using different online and off-line sensors. Several PM2.5 and PM10 peaks were observed during both sampling periods, with a relative increase in the PM levels ranging between 200 % and 500 % with respect to the normal background conditions. Given that these peaks were found to be highly correlated with supermicron particles and chemical elements typically found in mineral dust particles, such as Al, Fe, Si, and K, they are linked with African dust. This conclusion is supported by combining back trajectories with vertical profiles from radiosondes, reanalysis, and satellite images to show that the origin of the air masses arriving at Mérida was the Saharan Air Layer (SAL). The good agreement found between the measured PM10 concentrations and the estimated dust mixing ratio content from MERRA-2 (Version 2 of the Modern-Era Retrospective analysis for Research and Applications) corroborates the conclusion that the degradation of the local (and likely regional) air quality in Mérida is a result of the arrival of African dust.

Measurement report: Ice nucleating abilities of biomass burning, African dust, and sea spray aerosol particles over the Yucatán Peninsula

“…Overall, important differences in elemental composition are evident in the aerosol particles collected in January, April, and July in the Yucatán Peninsula, corroborating the presence of MA, BB, and AD particles as suggested by previous studies (e.g., Yokelson et al, 2009;Kishcha et al, 2014;Ríos and Raga, 2018;Ladino et al, 2019;Raga et al, 2021;Trujano-Jiménez et al, 2021;Ramírez-Romero et al, 2021). Figure 6 shows the average aerosol size distributions sampled under the influence of the different air masses: MA (cyan), BB (red), and AD (yellow).…”

“…Although 2018 was a more active AD season than 2017, as characterized by higher PM 2.5 and PM 10 concentrations (Ramírez-Romero et al, 2021), the INP concentrations measured in 2018 in the Yucatán Peninsula were lower than values reported elsewhere. For example, Ardon-Dryer and Levin (2014) found that the INP concentrations in the eastern Mediterranean ranged between 0.16 and 234 L −1 at temperatures between −11.8 and −28.9 • C, and larger values (up to 10 3 L −1 ) at temperatures from −18 to −29 • C were reported by Reicher et al (2019). Price et al (2018) found that in Cape Verde, the INP concentrations were an order of magnitude higher (0.1 and 10 2 L −1 at temperatures from about −10 to −25 • C) than those measured in Sisal and Mérida.…”

“…5, the AD particles were enriched in Al, Fe, and Si, which are present in different minerals and clays (Querol et al, 2019). Although 2018 was a more active AD season than 2017, as characterized by higher PM 2.5 and PM 10 concentrations (Ramírez-Romero et al, 2021), the INP concentrations measured in 2018 in the Yucatán Peninsula were lower than values reported elsewhere. For example, Ardon-Dryer and Levin (2014) found that the INP concentrations in the eastern Mediterranean ranged between 0.16 and 234 L −1 at temperatures between −11.8 and −28.9 • C, and larger values (up to 10 3 L −1 ) at temperatures from −18 to −29 • C were reported by Reicher et al (2019).…”

“…The presence of BB particles and the intrusions of AD into the Yucatán Peninsula have been previously documented (e.g., Yokelson et al, 2009;Kishcha et al, 2014;Ríos and Raga, 2018;Raga et al, 2021;Trujano-Jiménez et al, 2021;Ramírez-Romero et al, 2021). Ríos and Raga (2018) reported that within the BB season, the maximum fire density is observed in April.…”

“…Ríos and Raga (2018) reported that within the BB season, the maximum fire density is observed in April. Likewise, Kishcha et al (2014), Raga et al (2021), and Ramírez-Romero et al (2021) indicate that July is the period with the highest likelihood for the AD influx to the western Caribbean within the MSD. Therefore, April and July were chosen as the sampling periods to capture the presence of BB and AD particles in Mérida, respectively.…”