Interpretation of long-term surface radiative flux and its climate feedback over Arctic

Abstract

Recently, extreme weather such as cold wave and drought has occurred in mid-latitude. Arctic climate change is a key parameter to determine the cause of the weather. It is necessary to understand exactly how the Arctic climate is changing. One of the important factors in Arctic climate change is the 'Arctic amplitude', which is linked to various climate feedback. This thesis analyzes the surface radiative flux and analyzes the arctic climate feedback based on the analysis results to investigate Arctic climate change. The study is divided into three processes. The first is the process of evaluating the net radiation data of the Arctic. Although a variety of net radiation are provided, it is not clear which products are suitable for use in the Arctic and what characteristics they have. Reanalysis data and satellite data were verified using ground observations, and data suitable for the Arctic were selected through intercomparison of each data. The second process was conducted using the selected data, ERA5 and EBAF. The pattern of changes in net radiation was analyzed based on the characteristics of polar net radiation by data and long-term data over 15 years. The reanalyzed data, ERA5, and satellite-based data, EABF, reversed the annual change in polar net radiation. Why this phenomenon occurs was analyzed through PCA and relative error analysis. The trend of the polar net radiation was controlled by the longwave downward radiation, and an error of about 85.04 ~ 138.65% compared to the existing data occurred. Finally, the net radiation was analyzed by dividing the period according to the characteristics of the Arctic. Arctic climate change and feedback mechanisms begin with Arctic warming. In order to analyze the climate change in the Arctic, the surface air temperature was analyzed. In winter, a temperature increase of 10 times or more was observed compared to summer. The extreme month was selected based on the characteristics of the temperature, and this period is similar to the polar white/polar night period. The relationship with temperature and regional influence were analyzed by separating the period, and Kara and Barents Sea has a high influence on the net radiation time series. In addition, EABF in summer and ERA5 in winter showed high correlation with temperature and with climate variables. Based on a results, the surface radiative diagram was completed using EBAF in white night and ERA5 in polar night. Based on the completed diagram, it is linked with climate variables such as cloud fraction and sea ice extent. By synthesizing the three processes, the annual change within the climate feedback was described as a climate feedback chain. In the case of temperature, there was a change in 2.39~2.73 % regardless of the minimum/minimum period, and the net radiation of a similar amount was a change in 2.20 ~ 2.27%. However, it cannot be said that the exact amount has been converted from net radiation to temperature. Net radiation absorbed by the surface is transferred to the atmosphere in the form of sensible and latent heat. In the future, it will be necessary to analyze whether radiative flux is converted to cooling or warming using turbulent flux.