Monday, 9 July 2018
Regency A/B/C (Hyatt Regency Vancouver)
This study coupled the Weather Research and Forecasting (WRF) WDM6 Microphysics Scheme with the GRAPES_Meso. One precipitation process occurred on 3-5 June 2015 in Beijing and its surrounding area was respectively simulated by the WDM6, WSM6 and NCEP 5-Class scheme. Based on the findings of the three schemes in this study, both the distribution and magnitude of the precipitation simulation results using the WDM6 scheme were more consistent with the observation. Thus, the WDM6 scheme could be used as an alternative microphysics scheme in the GRAPES_Meso model for simulation studies in China region. Compared with the WDM6 scheme, the cloud liquid water content simulated by the WSM6 scheme was found to be greater, which provided more water vapor for graupel growth, leading to an increase in precipitation in the cold-rain processes. On the other hand, the WDM6 scheme incorporated the double-moment microphysics into the warm-rain processes and was able to forecast the number concentration of the cloud condensation nuclei (CCN), cloud droplet and raindrop. The sensitivity tests using the WDM6 scheme showed that an increasing in CCN number concentration led to CCN activation ratio and cloud droplet number concentration (Nc) increasing and cloud droplet effective diameter decreasing. The formation of more small-scale cloud droplets resulted in a decrease in raindrop number concentration (Nr), inhibiting the warm-rain processes, thus gradually decreasing the amount of precipitation. For areas main with cold-rain processes, the overall amount of precipitation increased but indicated a gradual decrease when the CCN number concentration reached a certain degree. Hence, the effect of CCN number concentration on precipitation in space exhibits significant differences for one precipitation event.
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