The general purpose of the exercises that follow is to:
Study the interaction between the global circulation and the chemical lifetime of a tracer.
Tracers with a varying chemical lifetime will be released in a global model. The tracers are transported by the global circulation (simplified in the MOGUNTIA model). Meanwhile, the tracers are (chemically) depleted. In general, concentration gradients will occur due to:
Transport tries to mix the tracer until its mixing ratio is uniformly distributed. The mixing ratio is defined as the fraction of tracer molecules to total air molecules. Typically, the mixing time of the troposphere is several years.
The first exercise Practice MOGUNTIA is intended for practice. You will learn to release tracers and to analyse output. A brief introduction to the Moguntia input is provided.
The second experiment is intended to determine the mixing time between the Northern and Southern hemisphere. It is called Interhemispheric Transport. Several methods are used to determine this time scale in the model, and the role of convection is discussed. The lifetime of the tracer used will be varied, but will be generally longer than the interhemispheric transport time.
The third experiment, The Budget of CO, studies the varies sources and sinks of CO. CO lives about two months, but its sink is mainly located in the low altitude tropics. Several sources are switched on/off, and comparisons to surface CO measurements will reveal the contribution of the various sources to the observed concentrations.
In the fourth experiment, the reaction constant between OH and Methyl-Chloroform will be determined. The lifetime of methylchloroform is about 5 years, and its historical sources are quite well known. A long-term simulation (1979-1993) will be performed, and ground-based measurements will be used to constrain the reaction constant. Next, it will be investigated if the determined rate of removal is also suitable to describe the observed Methyl Chlorofrom decay between 1998 to 2009
In the last experiment, you will investigate the budget of Carbon Dioxide. First, the impact of fossil fuel emissions on the atmospheric CO2 concentrations will be studied. Again the simulations will be compared to observations. But not all fossil CO2 stays in the atmosphere. Therefore, the impact of the oceans and the biosphere will be tested. The main question stdudied is: What is the influence of the supplied sinks on the seasosal cycle and the growth rate?
For most of these exercises, precooked input files are available. Sometimes, however, modifications of these files is necessary.
Good luck!!
