Weather pattern associated with climate change during Canadian Arctic wildfires: A case study in July 2019

Abstract

Wildfire is one of the major novel disturbances to the Arctic forest ecosystem. Relevant Weather and climate regimes are the most important elements affecting fire activity. However, these factors could be considered under changing due to Arctic warming. This paper discusses understanding relevant atmospheric weather and climate conditions over western Canada in July 2019 with a significant burned area fraction over western Canada, Alaska, and Siberia. Here, we show that daytime area-averaged Methane mole fraction for the month of July during recent two decades obtained from Modern-Era Retrospective Analysis for Research and Applications (MERRA) database has significant growth trend over Siberia-Alaska and western Canada with the highest value for the west part of Canada in July 2019. Also, the Pearson correlation coefficient displays the strong negative relationship between north hemisphere sea ice extent and daytime areas averaged Methane mole fraction during the month of July for Siberia-Alaska and western Canada at −0.72 and −0.69 correspondingly. However, during the last two decades, the average Carbone monoxide (CO) column burden for these areas has been slightly decreased. This research demonstrates that the Arctic region has faced an albedo decrease with a maximum value of around 40% departure from mean values in some parts mostly over the northern Canadian Arctic and northern Alaska boundary for this time. Monthly weather and climate map analysis have revealed that Canadian July 2019 wildfires were linked to different factors including the rather lower humidity (with a maximum of 17.5% in North Territories) and higher surface air temperatures. Besides, the composite mean weather map analysis for the middle troposphere shows strong climate–fire links, with effects of the local blocking anti-cyclonic high-pressure systems dominated over the western Canadian Arctic, Alaska, Siberia (mostly over the south and central parts). Daily weather analysis for the peak day, July 24 reveals a tilted mid-tropospheric long-wave ridge formation accompanies by a very dry surface air (relative humidity ∼30-% 40) and warm tongue extended from the northwest of the United State to western Canada and Alaska. During the wildfire case of July 24, 2019, south-westerlies to south easterlies winds caused the fire to spread mostly over western and southwestern areas in the local afternoon time.