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Korean Meteorological Society (한국기상학회)
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Effects of Uncertainty in Graupel Terminal Velocity on Cloud Simulation

싸락눈 종단 속도의 불확실성이 구름 모의에 미치는 영향

  • Lee, Hyunho (School of Earth and Environmental Sciences, Seoul National University) ;
  • Baik, Jong-Jin (School of Earth and Environmental Sciences, Seoul National University)
  • 이현호 (서울대학교 지구환경과학부) ;
  • 백종진 (서울대학교 지구환경과학부)
  • Received : 2016.05.24
  • Accepted : 2016.07.26
  • Published : 2016.09.30
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Abstract

In spite of considerable progress in the recent decades, there still remain large uncertainties in numerical cloud models. In this study, effects of uncertainty in terminal velocity of graupel on cloud simulation are investigated. For this, a two-dimensional bin microphysics cloud model is employed, and deep convective clouds are simulated under idealized environmental conditions. In the sensitivity experiments, the terminal velocity of graupel is changed to twice and half the velocity in the control experiment. In the experiment with fast graupel terminal velocity, a large amount of graupel mass is present in the lower layer. On the other hand, in the experiment with slow graupel terminal velocity, almost all graupel mass remains in the upper layer. The graupel size distribution exhibits that as graupel terminal velocity increases, in the lower layer, the number of graupel particles increases and the peak radius in the graupel mass size distribution decreases. In the experiment with fast graupel terminal velocity, the vertical velocity is decreased mainly due to a decrease in riming that leads to a decrease in latent heat release and an increase in evaporative cooling via evaporation, sublimation, and melting that leads to more stable atmosphere. This decrease in vertical velocity causes graupel particles to fall toward the ground easier. By the changes in graupel terminal velocity, the accumulated surface precipitation amount differs up to about two times. This study reveals that the terminal velocity of graupel should be estimated more accurately than it is now.

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References

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