Super-Droplet Method: a Particle-Based Cloud Microphysics Coupled with Nonhydrostatic Model
Abstract
Although clouds play a crucial role in atmospheric phenomena, the numerical modeling of cloud is not well established so far. Especially, it is still difficult to perform the accurate simulation of cloud microphysics, though several simulation methods, such as bulk parameterization method, spectral (bin) method, and the exact Monte Carlo method, have been proposed. We develop a novel simulation model of cloud microphysics, named Super-Droplet Method (SDM), which enables accurate calculation for the condensation/evaporation, the stochastic coalescence, and the motions of all the droplets with reasonable cost in computation. The methodology to calculate the coupling between the super-droplets and the non-hydrostatic cloud dynamics is also developed. We confirm that the result of our Monte Carlo scheme for the coalescence of super-droplets agrees very well with the exact solution of stochastic coalescence equation. The practicality of SDM is also demonstrated by the regional simulations of a shallow maritime cumulus. We have developed SDM only for warm rains with one soluble substance as the CCN, but it is not difficult to extend SDM to incorporate many properties of clouds, such as, several types of ice crystals, several types of soluble/insoluble CCN, their chemical reactions, electrification, and the breakup of droplets. Further, it is estimated that the computational cost will be very low compared to the cost of spectral (bin) method when the number of attributes of super-droplets, such as the radius of droplet and the masses of each type of CCN, is increased larger than 2 ~ 4. As a conclusion, though several extensions and validations are still necessary, we expect that SDM will lead us to a deep understanding of aerosol, clouds and precipitation interactions, and could be useful for weather forecast, the optimization of artificial rain, and the accurate prediction of global warming.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFM.A11D..07S
- Keywords:
-
- 0320 Cloud physics and chemistry;
- 3311 Clouds and aerosols;
- 3354 Precipitation (1854);
- 3355 Regional modeling