Rain drop 5. In general radiative effects of water clouds are subject to Mie computation, subject to a known spatial distribution and size distribution of the droplets. Problems arise primarily from unknown absorption by soot and mineral particles, which under some conditions can be important. Not only is cirrus a cloud with complex structure but the size spectrum, habits and skeletal structure of cirrus crystals changes from time to time and place to place.
Some generalities exist, but prediction of radiative budgets pose a problem.
A possible solution is to measure the properties in the laboratory and determine the sensitivity to input ice distribution, assessed by a mesoscale model input on the scale of some hundreds of kilometers. A major challenge is to produce in the laboratory uniform particle size and shape. Analytical formulation of particle spectra are often figments of the modelling imagination. Observational and hence trajectory prediction are required to make sense of the detailed structure of the cirrus in terms of particle nucleation and growth. Significant advances in this area would seem within our grasp.