welcome
Hi! Welcome at my cloud research site. I am Jesse Dorrestijn: a Phd-student at the Centrum Wiskunde & Informatica (CWI) in Amsterdam in the Netherlands. I am in the research group Computational and stochastic dynamics of the cluster Modelling, Analysis and Computing (MAC1).
my research
After obtaining my Masters degree in mathematics at the Universiteit Utrecht I started my Phd at the Center of Mathematics and Computer Science (in Dutch: Centrum Wiskunde & Informatica (CWI)) at 1st June 2010 on stochastic parameterization of atmospheric convection.
I will try to explain the subject of my research for the interested laymen:
In weather and climate predicting computer models clouds are a major source of uncertainty. It is impossible to compute the behaviour of every single cloud
at Earth, even with the large computer power of supercomputers this would be a way too difficult task. Therefore, if we want to include the effect
of the clouds on the state of the atmosphere, we have to come up with some smart function representing this effect. Scientists and in particular physicists,
developed some functions called parameterizations. The parameterization uses known large-scale variables as wind velocities, humidity and
temperature as input and the output is the mean effect of the clouds!! A problem is that the existing parameterizations are not good enough
to adequately calculate this effect: they do fine if they have to calculate the main effect in a very large region, but if this region gets smaller the results
are poor. With increasing computer power the regions over which the main effect of the clouds is calculated will decrease and consequently the results will
become worse and worse.
My research focuses on atmospheric convective clouds, clouds that arise in a thermal or a collection of plumes that form above warm surface areas during a hot day. Convective clouds, or sheep clouds, are beautiful, with some imagination one can see all different forms in them. Did you ever see something in clouds? Beautiful to look at, but very difficult to describe in models and that is my task!
At the Center of Mathematics and Informatics (CWI) my supervisor Daan Crommelin invented a new mathematical method to mimic processes that are of a small-scale and behave very randomly. It uses Markov chains generated by a Markov process, which is a stochastic process. Therefore, the method is stochastic or random. The result of the method is different every time you apply it, because a virtual die, a small throwable object with multiple resting positions, used for generating random numbers, is thrown every time step.
Clouds are of a small scale compared to the whole Earth and they behave quite randomly, so now I try to apply Daan's Markov chain method to the problem of representing convective clouds in weather and climate models by means of a parameterization. The method is a mathematical method, not specifically designed to describe clouds with. To be sure that the parameterization is realistic I work together with Professor Pier Siebesma, an expert on clouds working at the Royal Netherlands Meteorological Institute (in Dutch: Koninklijk Nederlands Meteorologisch Instituut (KNMI)).
To construct my model based on Markov chains, I need realistic atmospheric data. Realistic atmospheric data I obtain from my supervisor, Harm Jonker, working at the Technical University in Delft, TU-Delft. The data is produced by a Large Eddy Simulation, a computer model that is able to compute and calculate clouds. To run the model we use a supercomputer. The output data I use to construct the model.
Finally, we work together with Frank Selten, an expert on weather and climate models. When my model is ready to use Frank knows how to implemented this in a real wheather or climate model!! But, at this moment my model is not finished yet.
This is me.
contact
Feel free to contact me!
e-mail: cwi.nl, preceded by J.Dorrestijn
More contact information.
Large-Eddy Simulation(LES) movie
In this movie we see a simulation of deep convective clouds. It has been made by Jerome Schalkwijk who is a member of the cloud & climate group of Harm Jonker in Delft. Enjoy: