Airborne observations of turbulence and its influence on new particle formation in the atmospheric boundary layer

Abstract

This thesis is a work in the field of atmospheric physics. It will illustrated by means of airborne measurements, how turbulence influences the formation of newly formed parti- cles and how turbulence structures are modified by surface heterogeneity in the atmospheric boundary layer. The atmospheric boundary layer is the lowest part of the earth’s atmo- sphere, which is in direct contact with the earth surface. In this layer turbulent fluctuations of moisture and temperature play an important role in aerosol research. A layer with en- hanced temperature and humidity fluctuations lead to increased new particle formation. In a case study the boundary layer dynamics and its accompanied new particle formation event were investigated over a fairly homogeneous surface which yielded ideal conditions for the understanding of turbulent processes and its influence on new particle formation. However, natural landscapes rarely provide horizontal homogeneous conditions and have to be con- sidered to be heterogeneous. The surface heterogeneity causes a more complex behaviour on the atmospheric boundary layer’s flow as this is the case of homogeneous terrain. There- fore a second part of this thesis deals with the effects of surface heterogeneity (with several different surface types) on the ABL and its turbulence. Thus, one major aspect is, how the heterogeneous surface modify the kinematic expression of the turbulence (e.g vertical wind) and fluctuations of scalar quantities such as the temperature T and humidity q. In addition, these studies show that only second-order moments are adequate to describe the influence of surfaces heterogeneity. The second order moments use the quadratic