Characteristics Of Cyclones Entering Into The Arctic And Their Effects During The Rapid Period

In the past few decades,the significant climate changes in the Arctic have been observed,and its environmental factors(temperature,sea ice)have undergone dramatic changes.As a globally sensitive region,understanding the causes of changes in the region has implications for the study of global climate change.Polar cyclones,especially the Arctic cyclones generated in the south of the Arctic region and migrating northward into the polar region,are often accompanied by high winds,precipitation,and warming events during the progress of their development and migration,playing a role in transmitting substance and heat to the polar region from the mid-low latitudes in a long time sequence.Previous researches on the physical mechanisms,spatial and temporal distributions and trends of the Arctic cyclones have been studied.However,there is still room for research on their impact on atmospheric meridional transport and Arctic sea ice.Firstly,based on the automatic identification and tracking methods of cyclones by Zhang et al.and Tao et al.and the average sea level pressure data product of the European Centre for Medium-Range Weather Forecasting(ECMWF),the cyclones generated in the 30-70°N region were calculated,and the portion of the cyclones spanned by 70°N was retained,the characteristics of the number,intensity,life cycle,migration distance and velocity of this type of cyclones and their trajectories in space are analyzed in detail.To further analyze the effect of these cyclones on the northward heat and water vapour flux in the atmosphere,the value of vertical integration of northward heat and vapor flux on the 70°N latitude was extracted,and its statistics over time and distribution in space were collected.At the same time,combining the trend of the Arctic sea ice extent over time in the same period,the effects of various characteristic elements of this cyclones on the northward heat and water vapor flux,and Arctic sea ice extent were discussed.Finally,in order to understand the impact of the cyclone during its development over its transit area,the process of a summer cyclone activity was analyzed in detail.The main conclusions are as follows:(1)From March 1979 to February 2015,the total number of these cyclones shows a decreasing trend.After 1996,the intensity,average life cycle and northward movement of cyclones all increased.The life cycle of cyclones is mainly concentrated within 72 hours,the strong cyclones occurred mostly in the winter.The cyclones generated over seas and in areas south of 60°N have longer life cycles and longer northward distances;the cyclone trajectories are most densely distributed in the 90°W-0° interval.An important position across the 70°N North Pole is located in the 60-30°W,the Greenland area.(2)The vertically integrated of mean northerward heat and water vapor flux at 70°N is positive throughout the year.The maximum value of the former appears in January,the minimum value appears in June,the latter maximum value appears in August,and the minimum value appears in January;in the interannual variation,the annual total and the spring,summer,autumn northward heat flux at 70°N all showed a trend of increasing over time,the annual total and summer,autumn passed the text of significance,the winter showed a decreasing trend with time,but did not pass the test of significance,and the annual total amount and the four seasons of northward water vapor flux didn't change significantly.In terms of spatial distribution,the vertically integrated of mean northward heat and water vapor flux at 70°N during the 36 years is quite different in summer from other seasons.(3)The characteristics of the cyclones have a certain degree of influence on the vertically integrated of northward heat flux and the Arctic sea ice extent on the interannual variation.Among them,there is a positive correlation with the former and a negative correlation with the latter,and correlation of it with the northward vertically integrated water vapor flux is weak.However,during a specific cyclone weather,the effect of the cyclone transit on the vertical integration of northward heat and water vapor fluxes in the affected area is obvious,and it will also cause an increase of the temperature of the local layers during the impact period.This study initially established a link between cyclonic activity entering into 70°N and atmospheric meridional transport and sea ice,providing a new perspective for the Arctic change from a weather process.However,only one method was used to automatically identify and track the cyclones,and there was no comparison method.Secondly,when discussing the changes,the spatial trends were not deeply involved,and the analysis of the linkage with the Arctic sea ice was not comprehensive.Afterwards,research can be improved from these aspects or continue to work in depth.