Effects of deep convection on upper tropospheric air composition using a multiscale weather forecast model with on-line chemistry

Representing the tightly coupled dynamics, chemistry, clouds and radiation in the upper troposphere and lower stratosphere region is an important part of climate and weather modelling. As well as forecasting, weather models with atmospheric chemistry can provide a platform for studying the representation of individual processes and their impact on the atmosphere. One of the largest sources of uncertainty in weather prediction and climate models is the prediction of deep convection. Deep convection can modify the chemical composition of the upper troposphere and lower stratosphere through transport, emissions, chemistry and microphysics.;The focus of this thesis is on the rapid transport of chemical species from the boundary layer into the upper troposphere and on the emission of nitrogen oxide due to lightning in deep convective storms. Transport of trace gases due to deep convective up and downdrafts has been added for this study as well as a parameterisation for the emission of nitrogen oxide due to lightning associated with deep convection. A explanation of these processes is given as well as a description of the model used for the study. The flash rates generated by the lightning parameterisation is evaluated using data from space-borne instruments. The impact of transport and emissions relating to deep convection on the chemical composition of the atmosphere is examined by comparing model results with and without the processes included. Comparisons of trace gases such as nitrogen oxides, nitric acid, ozone and carbon monoxide are made with data from satellite and aircraft measurement campaigns.;In this study, processes relating to deep convection are examined to better quantify their impact on the chemical composition of the upper troposphere and lower stratosphere. The GEM-AQ (Global Environmental Multiscale model with Air Quality chemistry) model is used to perform this analysis. The model foundation is the operational weather forecast model (Global Environmental Multiscale or GEM model) from Environment Canada. Calculations relating to chemistry have been included on-line in the meteorological model. Trace gases are transported by the winds in the model and chemical and photolysis reactions are included to simulate the chemical composition of the atmosphere. Anthropogenic emission sources are included as well as biogenic emissions.