Assessment of vapour, clouds and rainfall spatial correlation over Europe, North America and Japan using ECMWF data

Summary form only given. At frequencies above 10 GHz, radio wave propagation is strongly affected by the atmosphere. In particular, the strongest contribution to electromagnetic attenuation is given by rain, but when system requirements are strict, second order effects are not negligible any more. In fact, the presence of water vapour, liquid water and oxygen in the atmosphere must be considered in designing high availability systems. At these frequencies the total tropospheric attenuation is very high and makes the adoption of static power margin not efficient for system performances. Site diversity and common on board resource systems are possible solutions. In particular the most promising are the ones based on the possibility of reconfiguring the antenna directivity pattern to distribute the EIRP to the areas experiencing rainfall. The knowledge of the characteristics of the spatial correlation of the main tropospheric impairments (rain, water vapour and clouds liquid water) can provide useful design parameters for the development of these systems. The data used for this study are ECMWF data of ERA15 that covers the years from 1979 till 1993 with an integration time of 6 hours and a spatial resolution of 1.5deg both in longitude and latitude. ERA40 database (45 years with 2.5deg of resolution) have been also considered. As for rain, the study has been made considering the three different types of precipitations: total, stratiform and convective. The objective of this study is the assessment of the spatial dimensions, orientations and geographical distribution of the rain spatial correlation areas over continental regions (e.g. Europe, North America, Japan) for high availability systems SatCom systems. In particular the influence of distance on the statistical dependence index, Z, and the climatological patterns of his spatial distribution in latitude and longitude are investigated. As for integrated water vapour content and integrated liquid water content, the c- orrelation study has been performed over Europe, North America and Japan. The statistical independence index Z has been used to study spatial correlation in each of the three regions. Finally graphical maps of spatial correlation of V and L have been generated