Variants for Warm and Cold Seasons

The melting layer height (ML) is one of the inputs for the set of MBFs and RSs. The main mode of the classification system is dedicated to the summer like situation with a positive value of ML. The organization of MBF and RS parameters follow this case of the main reference. See HydroClass: A Synthesis of Public Methods.

In cold season, any large scale melting layer is absent. The problem of classifying precipitation is better to be started from a different a priori expectation. The task is still nontrivial, as liquid forms of precipitation are not excluded (warm fronts, freezing rain). Significant convection can occur in cold season, too, producing heavy solid hydrometeors.

In order to describe these circumstances, a variant of the method has been constructed for the case ML less than 0, signalling precipitation in cold season. In such climatology, modified MBFs are computed for altitude, and the ML does not enter in MBF calculation in this case. Explicitly, liquid form of precipitation (rain) is allowed up to a fixed altitude of 5 km (3.1 mi) (MSL), wet snow is allowed to a characteristic altitude of winter storms, assumed constant of 2.5 km (1.6 mi), at present. Other types of precipitation are indifferent with respect to altitude.

Other MBFs are unchanged from their warm season settings. Subsequently, modified weights in rule strengths calculation are used.