13:45 〜 14:00
[MIS05-13] Modification of zonal and regional circulation over Northern Eurasia in a changing climate.
キーワード：atmospheric circulation, climate change, INM-CM6M , Northern Eurasia
The climate changes observed in the 21st century are reflected in a wide range of phenomena and processes. In recent decades, there has been an increase in the frequency of extreme weather events, with heatwaves, droughts, and heavy precipitation becoming more common. These changes have significantly impacted the functioning of various ecosystems. One potential driver behind the rise in adverse weather events could be the restructuring of large-scale atmospheric circulation. This restructuring is evident in shifts in the location and intensity of atmospheric pressure centers, as well as changes in regions of cyclonic activity. Research indicates that the rate of global temperature rise in the extratropical latitudes of the Northern Hemisphere far exceeds the global average, making these regions particularly vulnerable to such changes compared to tropical areas. In this study, we explore how the increase in global temperature may influence zonal and regional atmosphere circulation over Northern Eurasia during the 21st century.
The study uses the monthly mean ERA5 reanalysis data for the period 1950–2020, along with data from the INM-CM6M climate model for the historical experiment (1950–2014, 10 ensemble members) and the SSP2-4.5 and SSP5-8.5 scenarios (2015–2100, 3 ensemble members each). To analyze zonal and regional circulation, we used data on the zonal and meridional components of wind speed at the 200, 500, and 850 hPa pressure levels for the latitude band 40–85°N. For constructing vertical cross-sections of zonal wind circulation, we utilized data on the zonal component of wind speed across all available geopotential surfaces, ranging from 1000 to 100 hPa, within the same region. To characterize the zonal and regional circulation we used the large-scale circulation indices developed by Petrosyants and Gushchina (Petrosyants–Gushchina index) [1,2], that represent the velocity circulation along the latitude circles and the contours of atmosphere pressure centers.
To evaluate the INM-CM6M model's ability to reproduce atmospheric circulation, we compared the results obtained from the model and ERA5. It was demonstrated that the INM-CM6M model realistically captures the general structure of zonal wind circulation at 40–85°N. For most of the atmospheric pressure centers considered, the model accurately reproduces the annual cycle of circulation intensity in both depressions and anticyclones, though it tends to underestimate the absolute values of the circulation intensity.
By the end of the 21st century, the INM-CM6M model projects a weakening of global zonal circulation intensity while maintaining its overall structure. Notably, no significant difference between the SSP2-4.5 and SSP5-8.5 scenarios was detected. The model also predicts a reduction in circulation intensity for several atmospheric pressure centers, including subtropical anticyclones and some oceanic depressions. These changes in the spatial structure and intensity of global and regional circulation could have profound effects on the climatic regimes of vast territories and the frequency of extreme weather events.
This research was supported by the Russian Science Foundation (Grant No. 22-17-00073).
References:
1. Gushchina D. Yu., Petrosyants, M. A. and Sokolikhina, E. V. Integral characteristics of the global wind field. Part 2. The intensity of westerly and easterly circulation. Russian Meteorology and Hydrology, (5):1–10, 2002.
2. Petrosyants, M. A. and Gushchina,D. Yu. Velocity circulation in the centers of action of the atmosphere as a precipitation and temperature indicator. Part 1. Analysis of connections on seasonal scales. Russian Meteorology and Hydrology, (5):1–13, 2006.
The study uses the monthly mean ERA5 reanalysis data for the period 1950–2020, along with data from the INM-CM6M climate model for the historical experiment (1950–2014, 10 ensemble members) and the SSP2-4.5 and SSP5-8.5 scenarios (2015–2100, 3 ensemble members each). To analyze zonal and regional circulation, we used data on the zonal and meridional components of wind speed at the 200, 500, and 850 hPa pressure levels for the latitude band 40–85°N. For constructing vertical cross-sections of zonal wind circulation, we utilized data on the zonal component of wind speed across all available geopotential surfaces, ranging from 1000 to 100 hPa, within the same region. To characterize the zonal and regional circulation we used the large-scale circulation indices developed by Petrosyants and Gushchina (Petrosyants–Gushchina index) [1,2], that represent the velocity circulation along the latitude circles and the contours of atmosphere pressure centers.
To evaluate the INM-CM6M model's ability to reproduce atmospheric circulation, we compared the results obtained from the model and ERA5. It was demonstrated that the INM-CM6M model realistically captures the general structure of zonal wind circulation at 40–85°N. For most of the atmospheric pressure centers considered, the model accurately reproduces the annual cycle of circulation intensity in both depressions and anticyclones, though it tends to underestimate the absolute values of the circulation intensity.
By the end of the 21st century, the INM-CM6M model projects a weakening of global zonal circulation intensity while maintaining its overall structure. Notably, no significant difference between the SSP2-4.5 and SSP5-8.5 scenarios was detected. The model also predicts a reduction in circulation intensity for several atmospheric pressure centers, including subtropical anticyclones and some oceanic depressions. These changes in the spatial structure and intensity of global and regional circulation could have profound effects on the climatic regimes of vast territories and the frequency of extreme weather events.
This research was supported by the Russian Science Foundation (Grant No. 22-17-00073).
References:
1. Gushchina D. Yu., Petrosyants, M. A. and Sokolikhina, E. V. Integral characteristics of the global wind field. Part 2. The intensity of westerly and easterly circulation. Russian Meteorology and Hydrology, (5):1–10, 2002.
2. Petrosyants, M. A. and Gushchina,D. Yu. Velocity circulation in the centers of action of the atmosphere as a precipitation and temperature indicator. Part 1. Analysis of connections on seasonal scales. Russian Meteorology and Hydrology, (5):1–13, 2006.