Different Roles of Dynamic and Thermodynamic Effects in Enhanced Semiarid Warming

Enhanced warming in semi-arid regions has received much attention since it was first proposed, but the primary driver of this phenomenon remains unknown. This study applied dynamical adjustment to the temperature and partitioned the warming into two separate components: a thermodynamically forced component and a dynamically induced component. The results show that the mean amount of thermodynamic warming in the Northern Hemisphere (NH) in the study period 1902-2011 was 1.36 °C/109years and that the amount of dynamic warming was 0.14 °C/109years. In the mid-latitude zones of Asia, Europe, and North America, the thermodynamic warming was 1.60, 1.19, and 1.32 °C/109years, respectively, and the corresponding dynamic warming was 0.26, 0.14, and 0.09 °C/109years. Obviously higher thermodynamic temperatures were observed in semi-arid regions, suggesting that the enhanced semi-arid warming (ESAW) is the result of local thermodynamic effects. Thus, different local thermodynamic effects are responsible for the warming discrepancies in the semi-arid regions of Asia, Europe and North America. Moreover, the considerable bias of CMIP5 ensemble mean temperature trend appeared in semi-arid regions rather than other regions indicate that the simulation of semi-arid regions is particularly complex and difficult.