第八届青年地学论坛

In the polar spring, reactive halogen species can generate by photochemical reactions of halogen ions and ozone in a catalytic cycle, which induces a sharp depletion of tropospheric ozone. BrO is the main reactive halogen species that depletes ozone in the Arctic boundary layer, but many scientific questions about its source and activation mechanism are still uncertain. We present continuous BrO slant column densities and vertical column densities derived by Multi-Axis Differential Optical Absorption Spectroscopy (MAXDOAS) deployed at Ny-Ålesund (78.92°N, 11.93°E) in March 2017. We focused on one Bromine Explosion Event (BEE) in mid-March, during which the vertical column densities of BrO surged from 4.26×10¹³ molecular cm⁻² to the peak at 1.23×10¹⁴ molecular cm⁻² on March 17, surface ozone depleted from a background level of 46.25 parts per billion by volume (ppbv) to 13.9 ppbv. This case study indicates that the BEE was strongly associated with blowing snow induced by the cyclone systems that approached Svalbard from March 14 to 18. By considering meteorological conditions, sea ice coverage, and airmass trajectory history, we demonstrate that sea salt aerosols (SSAs) from blowing snow on sea ice, rather than from open ocean, are attributed to the occurrence of this BEE. Model results from a parallelized-tropospheric offline model of chemistry and transport (p-TOMCAT) indicate that this BEE was mainly triggered by a blowing snow event associated with a low-pressure cyclone system. This study suggests that the concentration of blowing-snow-sourced SSAs surged to peak when the airmass pass across the sea-ice-covered area under high wind speed, which is a critical factor in the process of bromine explosion observed in Ny-Ålesund.

Arctic,Ozone,BrO,DOAS