DECADAL COOLING OF EAST ASIA - THE ROLE OF AEROSOLS AND OZONE PRODUCED BY GALACTIC COSMIC RAYS

This paper illustrates the regional response of the surface temperature, as derived by the RegCM-4.6.0 model, to the tropospheric aerosols loading and an increased ozone density just above the tropopause (due to the galactic cosmic rays ozone production there). The individual forcing of each factor initiates a surface cooling being much stronger in the winter season. This result contradicts to some previous GCM modelling experiments suggesting a positive impact of the near tropopause ozone in Earth's radiation budget. To understand the RegCM model's response to the imposed O-3 forcing, we have analysed the upper troposphere-lower stratospheric H2O vapour behaviour at the highest four model's levels. The well pronounced drying of the upper troposphere-lower stratosphere (in the enhanced ozone experiment) motivates us to attribute the obtained surface cooling to the reduced water vapour and consequently decreased greenhouse warming. As a mechanism for such a coupled near tropopause O-3-H2O vapour impact on the surface temperature we propose the modulation of the tropopause temperature by the adjacent ozone density, and consequent adjustment of the upper tropospheric static stability (increased in the case of a warmer and decreased in the case of a cooler tropopause). The latter modulates the amount of water vapour near the tropopause decreasing or increasing its greenhouse effect.