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Long distance radio systems at 11 GHz are considered with respect to rain outage. Conventional tandem systems and simple route diversity systems are analyzed and compared on the basis of rain attenuation statistics obtained from radar observations. The comparisons appear to be very favorable to diversity systems in terms of the number of repeaters. Unfortunately, the available descriptions of joint probabilities of attenuation for pairs of radio paths allow only conservative analysis of very simple diversity systems, so that effective designs are not yet possible. Therefore, the need for further investigations on intense precipitation patterns still exists.

The concept of virtual temperature is reviewed and extended into the definition of the dynamic virtual temperature, which is the temperature that a parcel of dry air should have in order to experience the same acceleration as a parcel of cloud air. It is obtained from the equations of motion and depends on the water content in the three thermodynamic states: vapor, liquid, and solid. The scale analysis of the equation of the dynamic virtual temperature shows that the terms due to the acceleration and phase transitions of the particles are negligible with respect to the terms depending on gravity. Therefore, even though conceptually more adequate, the approximate mathematical expression of the dynamic virtual temperature is practically identical to the conventional definition of virtual temperature accounting for water loading.

Abstract. The Canadian Regional Climate Model with oxidant chemistry (CRCM)has

Abstract. The equations of the radar covariances and cross covariances for linear vertical and horizontal polarization, slant linear +45 ø and -45 ø polarization, and left-hand and righthand circular polarization are presented for a model medium containing spheroidal particles. This model takes into account the distribution of canting angles but assumes the uniformity of the distribution function along the propagation path. Assuming the particles to be locally equioriented, equations for the intrinsic differential reflectivity and the mean canting angle are derived. Furthermore, for particles having the same orientations throughout the region of precipitation, the total differential phase shift is obtained. Reflectivity and depolarization ratios are also considered. A comparison of the three polarization schemes from a theoretical point of view is made and illustrated with data from the DLR C band Doppler and polarimetric weather radar. Since the DLR radar did not record the magnitude of the covariances and cross covariances, the comparison is only partially complete. The data confirm the theoretical prediction that depolarization is stronger in circular and slant linear polarization than in linear horizontal/vertical polarization.