The role of aerosols in low and upper atmospheric layers condensation

Abstract

Airborne particles of anthropogenic and/or natural origin have certain direct and indirect effects in the atmosphere. Radiative transfer is the category of processes related to aerosols and clouds (direct effects). Indirect effects are always associated with condensates at various atmospheric layers. Condensation within the tropospheric layers is mainly related to aerosol physical and chemical properties, thermodynamical and dynamical processes. As it was found in various studies, there is a strong relationship between aerosols and extreme weather events such as deep convection and extreme rainfall. Low-level condensation is associated with low-cloud formation and fog. In this presentation we will discuss the condensation processes within the lower and upper troposphere and how they are affected by the various types of aerosols. New model development related to nucleation processes and condensation at different levels is discussed. The model used for development and application is the fully-coupled atmospheric modeling system RAMS/ICLAMS. Model simulations have been performed for selected cases related to (i) extreme precipitation events and (ii) low-level condensation and fog formation in the Euro-Mediterranean and Arabian Peninsula. The sensitivity tests showed that the explicit activation of aerosols as CCN and IN causes changes in the precipitation distribution as well as in its spatiotemporal patterns. Fog formation near the coastline and low-cloud formation mechanisms are controlled by the thermal cooling and moisture evaporation by the surface. The accurate simulation of the microphysical processes involved in formation and dissipation of fog depends on several variables.