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On the Definition of Precipitation Efficiency

On the Definition of Precipitation Efficiency. Speaker: Liou Date:2007/03/08. Introduction. Generally speaking, the range of PE might be less 100% and greater 0%. LSPE cloud be negative and might be greater then 100%. CMPE might be greater then 100%. Model setting.

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On the Definition of Precipitation Efficiency

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  1. On the Definition of Precipitation Efficiency Speaker: Liou Date:2007/03/08

  2. Introduction • Generally speaking, the range of PE might be less 100% and greater 0%. • LSPE cloud be negative and might be greater then 100%. • CMPE might be greater then 100%.

  3. Model setting • The cloud-resolving model. • The horizontal boundary is periodic. • The horizontal domain is 768km and the grid resolution is 1.5km. • The vertical grid size is 200m to 1000m. • The time step is 12s. • Hourly 96km-mean simulation data.

  4. Cloud-microphysics precipitation efficiency (CMPE) (Sui et al. 2005)

  5. The CMPE1 does not include all source terms for eventual formation of surface precipitation. And get new CMPE2 is :

  6. CMPE1 vs. CMPE2 Using hourly 96-km average data during 21-day integration.

  7. CMPE2 vs. Ps CMPE1 vs. Ps For strong rainfall (PS>5mm h-1), 50%< CMPE1＆CMPE2<100% For weak rainfall (PS>5mm h-1), 0%< CMPE1<350% 0%< CMPE2<100%

  8. (Gao et al. 2005) = is the vapor convergence is the local vapor change = is the surface evaporation rate Large-scale precipitation efficiency (LSPE) (water vapor budget)

  9. LSPE1 vs. LSPE2 -500%< LSPE1<500% 0%< LSPE2<100%

  10. LSPE1 vs. Ps LSPE2 vs. Ps • LSPE2 tends increase with increasing Ps. • LSPE1 has a much wider range of variability then LSPE2. • The negative values of LSPE1 are often occurred in light rain. (Ps<5mm h-1).

  11. LSPE2(QCM=0) vs. LSPE2 • LSPE2(QCM=0) is larger then LSPE2 • LSPE2(QCM=0) cloud be larger 100% • The effect of QCM in the larger LSPE2 is more important.

  12. CMPE2 vs. LSPE2 hourly mean 48km average data 6 hourly mean 96km average data The hourly 96-km average data Daily mean 96km average data hourly mean 24km average data

  13. Conclusion • LSPE2 and CMPE2 range form 0 to 100%. • CMPE2 is only including microphysical process and LSPE2 is including both hydrometer species and water vapor. • When light rain occurs, the LSPE1 and CMPE1 are more likely then 100%.

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