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

Abstract

Abstract. Most precipitation from deep clouds over the continents and in the intertropical convergence zone is strongly influenced by the presence of ice crystals whose formation requires the presence of ice nucleating particles (INPs). Although there are a large number of INP sources, the ice nucleating abilities of aerosol particles originating from oceans, deserts, and wildfires are poorly described at tropical latitudes. To fill this gap in knowledge, the National Autonomous University of Mexico micro-orifice uniform deposit impactor droplet freezing technique (UNAM-MOUDI-DFT) was constructed to measure the ice nucleating activity of aerosol samples that were collected in Sisal and Mérida, Yucatán (Mexico) under the influence of cold fronts, biomass burning (BB), and African dust (AD) intrusions during five short-term field campaigns between January 2017 and July 2018. The three different aerosol types were distinguished by their physicochemical properties. Marine aerosol (MA), BB, and AD air masses were found to contain INPs; the highest concentrations were in AD (from 0.071 to 36.07 L−1 at temperatures between −18 and −27 ∘C), followed by MA (from 0.068 to 18.90 L−1 at temperatures between −15 and −28 ∘C) and BB (from 0.063 to 10.21 L−1 at temperatures between −20 and −27 ∘C). However, MA had the highest surface active site densities (ns) between −15 and −30 ∘C. Additionally, supermicron particles contributed more than 72 % of the total INP concentration independent of aerosol type.

Mexican agricultural soil dust as a source of ice nucleating particles

“…Tegen and Fung (1995) and Tegen et al (2004) also proposed that the PSD of the aerosol particles can vary according to soil type. The size of the aerosol particles is well known to influence their behavior as INPs (Diehl and Wurzler, 2004;DeMott et al, 2010;Mason et al, 2015b;Córdoba et al, 2021). This fact is evidenced in the different PSD distributions observed for each sample in Fig.…”

“…The ice nucleating abilities of the agricultural dust particles collected in the field and generated in the laboratory were analyzed through the immersion freezing mode using the UNAM-MOUDI-DFT (Córdoba et al, 2021). The equipment consisted of (a) a cold stage, (b) a humid/dry air system, (c) a Zeiss Axio Scope A1 optical microscope (Axiolab Zeiss) with a recording system, and (d) a data acquisition system (Córdoba et al, 2021).…”

Characterization of aerosol particles during a high pollution episode over Mexico City

“…Subsequently, the glass coverslips were placed in stages 5 and 6 (cut sizes of 1.0 and 0.56 µm, respectively) of an 8-stage Micro Orifice Uniform Deposit Impactor (MOUDI, Model 100R, MSP Corp.) 36 . The glass plates were fixed onto the MOUDI stages by substrate holders, as reported by Córdoba et al (2021) 37 . The MOUDI inlet flow was calibrated before sampling to 30 L/min using a Gilibrator air flow calibrator (Sensidyne, Inc., Clearwater, Florida, USA).…”

Characterization of aerosol particles during a high pollution episode over Mexico City

“…Subsequently, the glass coverslips were placed in stages 5 and 6 (cut sizes of 1.0 and 0.56 µm, respectively) of an 8-stage Micro Ori ce Uniform Deposit Impactor (MOUDI, Model 100R, MSP Corp.) 56 . The glass plates were xed onto the MOUDI stages by substrate holders, as reported by Córdoba et al (2021) 57 . The MOUDI inlet ow was calibrated before sampling to 30 L/min using a Gilibrator air ow calibrator (Sensidyne, Inc., Clearwater, Florida, USA).…”