Roles of dynamic and thermodynamic effects in seasonal mean surface air temperature trends over Central Asia during 1979–2018

The present study investigated seasonal and spatial characteristics of the trends in surface air temperature (SAT) over Central Asia during 1979–2018 and the relative contributions of dynamic and thermodynamic effects using a dynamical adjustment methodology. Regional averaged total SAT shows the largest rising rate in spring and its trend is not obvious in winter. The thermodynamically effect induces a widespread warming trend in most of Central Asia in all the four seasons. The dynamically induced SAT trends exhibit obvious seasonal and regional differences. Both dynamic and thermodynamic effects play a crucial role in the total SAT increasing trend in spring, the thermodynamic effect is predominantly responsible for SAT warming and the dynamic effect has a secondary contribution in summer, the rising temperature in autumn is attributed to the thermodynamic effect and the dynamic effect has a negative but insignificant contribution, and the total SAT trend in winter is small due to opposite contributions of thermodynamic and dynamic effects. Further analysis revealed that the changes in the Scandinavia pattern (SCAND) during 1979–2018 are likely the cause of dynamically induced temperature trends in spring, autumn and winter. The dynamical component of summer SAT trends over eastern Central Asia is contributed by the interdecadal transition of the Atlantic multidecadal oscillation (AMO) and Pacific decadal oscillation (PDO). Those climate modes contribute to SAT variations via their effects on wind-induced temperature advection and surface heat fluxes.