13 Feb

Before I head over to the start of our annual HD(CP)2 meeting, where HD(CP)2 stands for high-definition clouds and precipitation for climate prediction, it seemed fitting to talk about the role of high-resolution simulation for EUREC4A.

One of the very cool things about EUREC4A will be the very high resolution simulations that will accompany it. We can imagine having simulations over an area of 500 x 500 km with a 100 m mesh. During NARVAL-2 we got a taste of what this can provide. Attached are three images that Matthias Brueck provided, where we look at how boundary layer convergence and clouds are alligned in boreal winter (A1) and summer (A2). Open the images and zoom in. The resolution is limited by the pixels on my computer rather than the simulations. For fun I also include another image where he zooms on different regions and shows the different types of cloud forms that we capture.

But what is fascinating, and what we know (but like to forget), is the very tight coupling between clouds and circulation. Clouds are beasts of circulation … something that Sandrine pointed out many many years ago when introducing the idea of organizing our way of looking at clouds by sorting them according to large-scale circulations regimes. When you think of figures like Matthias', and realize that all cloud parameterizations are thermodynamic, i.e., they take the circulation for granted and only measure its trace in terms of its effect on the large-scale thermodynamic fields, then you see that with the experimental techniques (measuring circulation) and simulation capacity we are developing for EUREC4A we are on frontier of a whole new era in climate science… how exciting, and what better way to start our annual HD(CP)2 meeting, which is the German national project that makes this possible.

I think that in some years people will look back at how we have approached clouds and climate in the past fifty years and scratch their head and wonder why we ever came up with such a preposterous idea … fortunately the high-resolution gives us the chance of a course correction.



Back to top