Seasonal Prediction Skill of Northern Extratropical Surface Temperature Driven by the Stratosphere

This study explores the role of the stratosphere as a source of seasonal predictability

of surface climate over Northern Hemisphere extra-tropics both in

the observations and climate model predictions. A suite of numerical experiments,

including climate simulations and retrospective forecasts, are set up to

isolate the role of the stratosphere in seasonal predictive skill of extra-tropical

near surface land temperature. We show that most of the lead-0 month spring

predictive skill of land temperature over extra-tropics, particularly over northern

Eurasia, stems from stratospheric initialization. We further reveal that this

predictive skill of extra-tropical land temperature arises from skillful prediction

of the Arctic Oscillation (AO). The dynamical connection between the

stratosphere and troposphere is also demonstrated by the significant correlation

between the stratospheric polar vortex and sea level pressure anomalies,

as well as the migration of the stratospheric zonal wind anomalies to the lower

troposphere.