Today we went to Cabauw to fix some radar issues that we have. The weather forecast of today was good for lidar measurements too we started the Raman-lidar CAELI as well. As you can see as all the measurement quick-looks for the lidar systems (Polly and CAELI) we had some nice cirrus layer over Cabauw. So we expected also that our colleagues from Munich would have a good change to observe some HALOs within the cirrus clouds. But the conditions where that good, that we could also observe this HALOs over Cabauw.
Halos are optical reflections produced by hexagonal oriented ice crystals within ice clouds. This reflections produce a ring around the sun and also some bright dots next to the sun. Observations of such HALOs make it possible to get information about the ice crystal shape and their orientation. Lidar measurements could also give such information. Combining the measurements of the lidar systems and the HALO-camera in de Bilt will hopefully produce some nice results.