LES Intercomparison Case of Precipitating Shallow Cumulus Margreet van Zanten, Bjorn Stevens, Pier Siebesma, Louise Nuijens A.S. Ackerman, H. Jiang, D. Mechem, D.C. Lewellen, S. Wang, B. Shipway, F. Couvreux, M. Khairoutdinov, A. Noda, P. Bogenschutz, J. Slawinska, A. Cheng, F. Burnet.
LES Intercomparison Case of Precipitating Shallow CumulusMargreet van Zanten, Bjorn Stevens, Pier Siebesma, Louise NuijensA.S. Ackerman, H. Jiang, D. Mechem, D.C. Lewellen, S. Wang, B. Shipway, F. Couvreux, M. Khairoutdinov, A. Noda, P. Bogenschutz, J. Slawinska, A. Cheng, F. Burnet
The RICO LES Intercomparison Case focuses on precipitating shallow cumulus convection and is based on observations taken during a three-week period in a relatively undisturbed trade-wind regime in the Caribbean.
Fourteen participants provided output for 24-hour simulations with and without microphysics:
The character and amount of precipitation differs substantially among the simulations
First version of the paper has been written and distributed among participants (Margreet van Zanten)
Work is in progress to put the paper into its final shape, that is:
In final form: 2 - 4 weeks?
If dynamics would constrain precipitation, a positive relationship between in-cloud liquid water (for simulations without microphysics) and precipitation (for simulations with microphysics) may be expected
In the data as well as in LES rain seems to scale with echo fraction, which suggests that to a first approximation once a cloud begins to rain the micro-physical details do not matter
(3) Comparison with RICO data
What threshold defines cloud?
When looking at intermittency of precipitation, one needs to keep in mind that the precipitation fraction or 'chances of finding rain somewhere in a domain', are very scale-dependent
Mass flux decreasing less sharply with height : importance entrainment and properties of air entrained (Pier)