Time-Varying Contribution of Internal Dynamics to Wintertime Land Temperature Trends Over the Northern Hemisphere

摘要

Understanding the contribution of internal dynamics to recently observed land temperature trends is a challenge. In particular, the time-varying contributions of internal dynamics to these changes are poorly understood. Here, we apply a "dynamical adjustment" method to quantitatively estimate the time-varying contribution of the internal dynamics to the wintertime land surface air temperature (SAT) trends over the Northern Hemisphere (NH) during 1961-2018. The observed wintertime land SAT trends over the NH are strongly influenced by internal dynamical processes, especially over the Eurasian continent. The internal dynamically induced SAT trends contribute more than 60%, 40%, and 70% of total warming during the first 30 years of 1961-1990 over the NH, North America, and Eurasian continent, respectively. These ratios decrease to about 20% with the extension of time period to 1961-2018. The time-varying contributions of internal dynamics analogs to the multidecadal fluctuations of the Arctic Oscillation.