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Cloud-resolving CNTL experiments using WRF model effectively reproduce the month-scale characteristics of precipitation occurring on Hainan Island in the autumns of 2010 and 2011. The influences of low-density graupel (LDG) and high-density graupel (HDG) on autumn precipitation were modeled using the WDM6 microphysical scheme.

The top three sources of rainwater in these simulations are: melting graupel, melting snow, and cloud water collected by rain water. The top three rainwater sinks are: rainwater collected by graupel, rainwater collected by snow, and evaporation. The conversion from rain water to graupel makes the largest contribution to precipitation.

Three categories of graupel has minor influences on the precipitation area and the time-varying tendency of regionally averaged precipitation, but it has a dramatic influence on precipitation intensity. LDG strengthened precipitation below 100 mm and weakened precipitation above 100 mm. HDG weakened precipitation below 100 mm and strengthened precipitation above 100 mm.

As low-density graupel collects more rainwater, the graupel content increases. As high-density graupel collects less rainwater, the graupel content decreases. Little low-density graupel is converted into rainwater during heavy precipitation, while if more, it is converted to rainwater during weak precipitation. Furthermore, as the density of graupel increases, more of it is converted into rainwater. The net conversion rates of the various hydrometeors into rain water are consistent with changes in the output precipitation.