A thesis submitted April 2017 for the degree of Doctor of Philosophy and defended juni, 2017.
The PhD School of Science, Climate and Computational Geophysics, Faculty of Science, Niels Bohr Institute, University of Copenhagen
Prof. Eigil Kaas, University of Copenhagen
Prof. Alexander Baklanov, DMI/WMO
Integrated modelling of physical, chemical and biological weather
Integrated modeling of physical, chemical and biological weather has been widely considered during the recent decades. Physical, chemical and biological weather is defined as short-term variations of meteorological parameters, and chemical and biological aerosol concentrations, respectively. Integrated modeling implies interactions of meteorological parameters and chemical/biological aerosol concentrations. The emitted aerosol particles are subject to atmospheric transport, dispersion and deposition. Aerosols in turn impact meteorology through so-called feedback mechanisms affecting radiation as well as cloud and precipitation formation. The present study is focused on interactions between physical and biological weather with emphasis on birch pollen modelling as well as on physical and chemical weather with focus on black carbon (BC) aerosol modelling.
For this study the Enviro-HIRLAM model has been used. This is an online-coupled meteorology-chemistry model where chemical constituents and different types of aerosols are an integrated part of the dynamical model, i.e., these constituents are transported in the same way as, e.g., water vapor and cloud water, and, at the same time, the aerosols can interactively impact radiation and cloud micro-physics. The birch pollen modelling study has been performed for modelling domains covering Europe and western Russia. Verification of the simulated birch pollen concentrations against in-situ observations showed a good agreement with the best score at two Danish sites: Copenhagen and Viborg. It was verified that the birch pollen emissions and concentrations, as expected, depends strongly on the air temperature, relative humidity, wind speed and precipitation. The results reveal a need for high quality of meteorology forecasts in order to perform operational birch pollen forecasts.
The BC modelling study was performed for a modelling domain covering most of the Northern Hemisphere with focus on the EU and Arctic regions. Verification of BC concentrations against observations showed a good agreement for the EU air quality measurement sites. However, the Arctic region turned to be much more challenging for simulating BC concentrations. The aerosol feedbacks to the physical atmosphere were also studied, and the model simulations indicated that the aerosol feedbacks induced the following changes: reduction of the net downward short-wave surface radiative fluxes, reduction of near surface air temperature, increase of total cloud cover and cloud water and a corresponding decrease in precipitation amount.