Cirrus clouds monitoring using a V-band radar for HAPS: a feasibility analysis

According to a report of the Intergovernmental Panel on Climate Change (IPCC, 2007) one of the largest uncertainties in predicting climate change is the coupling between clouds and the Earth’s climate system. Cirrus clouds (or ice crystal clouds) are one of the specific type of clouds that are the main responsible of such uncertainty in predicting climate change. At any time in the midlatitudes, cirrus can cover about 30% of the Earth’s surface, and in the Tropics this coverage can increase to about 60–70%. With such a spatial and temporal coverage it is not hardly surprising that cirrus is an important component of the Earth–atmosphere radiation balance and hydrological cycle. Our knowledge on radar meteorology and on 77 GHz automotive radars, used also for rain monitoring, will allow us to electromagnetically characterize the cirrus and develop a preliminary study to use a 75 GHz radar (IEEE V-band) for clouds monitoring. The idea of the work is to formulate the scattering mechanism occurring at 75 GHz in the cirrus (potentially using and extend already existent ice-crystal model) in order to accomplish the following feasibility analysis of a small radar operating at such frequency. This radar could be carried on-board on a HAPS, in order to extend the HAPS and satellite Earth observation activities and available technologies. Therefore, the presented activity is divided into 2 sections: 1) The cirrus scattering model at 75 GHz. The scientific literature present different scattering models for lower frequency bands, with respect to IEEE V-band, and for the 94 GHz Cloud Sat vertical cloud-profiling radar. The study will fill the gap and present the advantages of using this frequency band, potentially also in cooperations with the others. 2) The feasibility analysis of a radar operating at such frequency for cirrus clouds monitoring.