Cloud structure

3D radiative transfer is the study of the influence of structure on radiative transfer. Here I present my work on cloud structure, divided up into 3 sub themes. For some background ideas see my essay on the description of the fractal and the non-fractal structure of clouds.

The structure of liquid water path (LWP) and liquid water content (LWC)

Time series of LWP are smoother that LWC measurements at scales smaller than the depth of the cloud. This has been measure with the high-resolution microwave radiometer MICCY and can be understood as LWP is an integrated property and small scale structures are averaged away. First results are presented in a poster for EGU2005.

A scale break in high-resolution liquid water path measurements
EGU, Vienna, Austria, 24 - 29 April 2005
Victor Venema, Verena Leyendecker, Clemens Simmer

A sufficient and simple description of cloud structure

We can describe a cloud measurement by its mean, variance and other moments, by its autocorrelation function or Fourier coefficients, or by its wavelet coefficients, structure functions or singular measures and probably in many more ways. Which description do we need? What is the simplest, but sufficient description that allows us to determine the optical properties of a cloud field? Our work with surrogate cloud made from stratocumulus fields, suggest that maybe an LWC height distribution and the linear spatial correlation might be enough. See the evaluation section in the article on surrogate cloud fields. In future we would like to extent this work.

Surrogate cloud fields generated with the Iterative Amplitude Adapted Fourier Transform algorithm
Submitted, 2004
Victor Venema, Steffen Meyer, Sebastián Gimeno García, Anke Kniffka, Clemens Simmer, Susanne Crewell, Ulrich Löhnert, Thomas Trautmann, and Andreas Macke

Scanning measurements of LWP with the microwave radiometer MICCY

During the BBC cloud measurement campaigns (article | web site | data base) we have made scanning measurements with the microwave radiometer MICCA and the cloud radar MIRACLE (from the GKSS). Analysis of the BBC results showed that the structure of LWP depends on the elevation angle. Thus, many measurements at one angle are needed to describe the structure, which we did in BBC2.

The 4D-Clouds project: Cloud structure measurements with a scanning microwave radiometer and a scanning cloud radar
Second European Conf. on Radar Meteorol. (ERAD), Delft, 18-22 November 2002
Victor Venema, Susanne Crewell, Clemens Simmer, Jens Meywerk, Markus Quante, and Oliver Sievers
Last update: May 2005.