气溶胶分布演变所引发的气候响应模态

Zonal mean and shift modes of historical climate response to evolving aerosol distribution

人类活动起源的气溶胶主要分布在北半球,其引发的区域气候响应特征及动力机理仍不清楚.针对这个问题设计的理想化数值试验的结果表明,气溶胶引起的气候变化分为两个阶段:1940~1980年,全球气溶胶增多,引发向北半球输运能量的纬向平均气候响应模态;1980~2020年,气溶胶强迫从西半球向东半球纬向迁移,海盆尺度的海洋-大气耦合过程变得重要,气候响应在太平洋和大西洋间呈现显著的差异.海洋动力过程会减弱纬向平均模态但加强纬向变化模态,特别是太平洋的响应在这两个阶段均呈现拉尼娜型的海温异常分布.本文揭示了气溶胶强迫引发的两个气候响应模态的差异,有利于对历史气候变化的认识和归因.

Anthropogenic aerosols are effective radiative forcing agents that perturb the Earth’s climate. Major emission sources shifted from the western to eastern hemisphere around the 1980 s. An ensemble of single-forcing simulations with an Earth System Model reveals two stages of aerosol-induced climate change in response to the global aerosol increase for 1940–1980 and the zonal shift of aerosol forcing for 1980–2020, respectively. Here, using idealized experiments with hierarchical models, we show that the aerosol increase and shift modes of aerosol-forced climate change are dynamically distinct, governed by the inter-hemispheric energy transport and basin-wide ocean–atmosphere interactions, respectively.The aerosol increase mode dominates in the motionless slab ocean model but is damped by ocean dynamics. Free of zonal-mean energy perturbation, characterized by an anomalous North Atlantic warming and North Pacific cooling, the zonal shift mode is amplified by interactive ocean dynamics through Bjerknes feedback. Both modes contribute to a La Ni?a-like pattern over the equatorial Pacific. We suggest that a global perspective that accommodates the evolving geographical distribution of aerosol emissions is vital for understanding the aerosol-forced historical climate change.