Since 1988, I have been involved in numerical modeling of the physics and chemistry of the atmosphere. I have used mesoscale models to investigate human and natural (e.g. fire, volcanic eruptions, anthropogenic emissions, land-use changes) impacts on weather, air quality and climate. In close cooperation with hydrologists and geologists I coupled a hydrologic and meteorological model and developed an integrative hydrometeorological model. I worked with computer scientists on optimizing chemistry transport models for parallel computers. I led several projects to study ground water recharge, dry deposition of reactive atmospheric trace gases, water availability under changed climate conditions, the impact of land-use changes on evapotranspiration, cloud and precipitation formation, and impacts of various emission sources on air quality and weather. From 1999 to 2001 I was honored as a Heisenberg Fellow for Physical Hydrology, a prestigious award conferred by the DFG. My scientific career in America dates back to 1989, when I worked as a visiting graduate student at the ASRC of the State University of New York (SUNY) at Albany. In 2000, I worked at the National Center for Atmospheric Research (NCAR) at Boulder, Colorado. In 2001, I joined the University of Alaska Fairbanks (UAF). At UAF, I continue my research direction with special focus on air quality issues of the Arctic and continue my teaching activities. Since 1995, in Germany and the United States, I have taught cloud physics, satellite meteorology, physical hydrometeorology, paleoclimatology, parameterization of hydrometerological processes, numerical modeling and parameterization methods, mesoscale dynamics, and introduction to computational meteorology and introduction to atmospheric sciences. In 2011, I published a book entitled "Land-use and Land-cover Changes - Impact on Climate and Weather" that is available at http://www.springer.com/earth+sciences+and+geography/atmospheric+sciences/book/978-94-007-1526-4. I want to contribute to improving numerical models in order to simulate the water, energy and trace gas cycles appropriately. Doing so will allow policy makers to use model outcomes to assess future water resources, water and air quality and to make reasonable decisions to meet the challenges of the future.