Polar aerosol rivers: detection, characteristics and potential applications

Abstract

Aerosols play a key role in polar climate, and are affected by long-range transport from the mid-latitudes, both in the Arctic and Antarctic. This work investigates poleward extreme transport events of aerosols, referred to as aerosol rivers (AeR), leveraging the concept of atmospheric rivers (AR) which signal extreme transport of moisture. Using reanalysis data, we build a detection catalog of polar AeRs for black carbon, dust, sea salt and organic carbon aerosols, for the period 1980–2022. First, we describe the detection algorithm, discuss its sensitivity, and evaluate its validity. Then, we present several extreme transport case studies, in the Arctic and in the Antarctic, illustrating the complementarity between ARs and AeRs. Despite similarities in transport pathways during co-occurring AR/AeR events, vertical profiles differ depending on the species, and large-scale transport patterns show that moisture and aerosols do not necessarily originate from the same areas. The complementarity between AR and AeR is also evidenced by their long-term characteristics in terms of spatial distribution, seasonality and trends. AeR detection, as a complement to AR, can have several important applications for better understanding polar climate and its connections to the mid-latitudes.

Polar Aerosol Atmospheric Rivers: Detection, Characteristics, and Potential Applications

“…This code leverages the contour detection offered by the Matplotlib library (Hunter, 2007), and the image analysis tools from the OpenCV library (Bradski, 2000) which provides an efficient way of masking 2-dimensional data. The corresponding detection catalogs for AR and p-AAR, based on MERRA-2 vertically integrated fluxes at 1° × 1° spatial resolution (see Section 2.2) and covering the period 1980-2022, along with the processing and detection codes, are available at https://doi.org/10.5281/zenodo.8082768 (Lapere, 2023).…”

“…Regional and seasonal large-scale pollution transport, such as Arctic haze, is not detected as p-AAR due to the use of an extreme (P97), seasonal (monthly) and local (point by point) threshold, which filters out regularly occurring aerosol transport pathways. p-AARs are extreme transport events that are generated by strong blocking activity, similar to polar ARs (Wille et al, 2019), and they therefore have elongated, filament-like structures (see the detection catalog available at https://doi.org/10.5281/zenodo.8082768 (Lapere, 2023) and Figures in Section 3.2). Due to their shape and their similarity to polar ARs, we refer to these events as aerosol atmospheric rivers.…”

“…The detection catalogs for AR and p-AAR, based on MERRA-2 vertically integrated fluxes at 1° × 1° spatial resolution and covering the period 1980-2022, along with the processing and detection codes, are available at https://doi.org/10.5281/zenodo.8082768 (Lapere, 2023). via project CRiceS (Climate Relevant interactions and feedbacks: the key role of sea ice and Snow in the polar and global climate system).…”

Atmospheric River Rapids and Their Role in the Extreme Rainfall Event of April 2023 in the Middle East

“…When they move over a dust source region, such as the Saharan and Arabian Deserts, the associated wind flow can trigger dust lifting and create hazardous conditions (Dezfuli, 2020; Dezfuli et al., 2021; Francis et al., 2023; Nelli et al., 2021a; Voss et al., 2021). Besides water vapor and dust, ARs can transport other aerosols such as black and organic carbon and sea salt (Chakraborty et al., 2021, 2022; Lapere et al., 2024). They account for up to 50% of the wintertime precipitation in mid‐latitude regions (Lavers & Villarini, 2015), and are projected to be stronger and more persistent in a warming climate (Espinoza et al., 2018; Massoud et al., 2020; Nellikkattil et al., 2023; Payne et al., 2020; Shields & Kiehl, 2016; Tian et al., 2023; Wang et al., 2023).…”