A regional-model « climatology » of vertical mass and water-vapour transport for the Hibiscus-Troccinox-Troccibras campaign 2004 F. Gheusi, J.-P. Cammas, J.-P. Chaboureau, J. Duron, C. Mari, P. Mascart and J.-P. Pinty Laboratoire d’Aérologie Toulouse (France)
Meso-NH forecast support during the campaign (1) Resolution = 30 km Domain 3000 km x 3000 km « Radar » rectangle Mass budget (arbitrarily) restricted to this area
Meso-NH forecast support during the campaign (2) • Daily time-period considered for • vertical air-displacement • integration of mass budgets 06 UTC 24 UTC Set of 30 simulations from 05 Feb to 05 Mar Makes possible some statistics !
Some climatological features(30-day averaged fields) P + wind @ z = 3000 m Temp. °C (colorscale) -2 PVU tropopause (dashed) Zonal wind (dotted) vertical cross-section SACZ Wind-strength @ z = 1500 m
Mean daily vertical motion (06-24 UTC) S-N cross-section: Dz = z – z0 (km) z0 (m) @ z = 6000 m SACZ
Mass budget computation: a post-processing method Model run: transport of a passive tracer initialized with the altitude, then … • Upward mass flux • through z0 • between t0 and t: • Air-parcels that • were initially below z0 • are finally above z0 z z0 Mass flux between t0 and t = Mass of the colored volume x Surface = air-parcels with common initial altitudez0
Mass budget computation: what was performed For each day (simulation Day 1) 21000 m 18000 m = flux 06-24 UTC (up / down) 15000 m Net flux = up - down 12000 m 9000 m Mass flux = dry air or water-vapour 6000 m 3000 m Computation for 30 days: few seconds on a Linux PC !
Qualitative comparison against rain satellite-retrievals (TRMM, 125x125 km²) 28 February good ! 06 February heavy-rain over Bauru, good forecast ! 14 February active front, forecasted too late… 3-4 March not so bad diurnal convection period, not good… Mixed results, better with sub-grid cloud fraction ? To be tested…
Dry-air mass budget Criterion: Max( flux(9000m) + flux (12000m) )
Dry-air mass budget Criterion: Min( flux(9000m) + flux (12000m) )
Water-vapor flux:qualitative comparison against rain satellite retrievals (TRMM, 125x125 km²) Better correlation with the « observed » precipitation
Conclusions Numerical aspects • 30 MesoNH runs in forecast mode: statistical approach over the period 05 Feb – 05 Mar 2004. • Flux computation based on • On-line passive transport of initial-coordinate tracers • Low-cost and highly adaptable post-processing (PC) Vertical motion « model climatology » • Subsidence in the lower troposphere, S of the SACZ • Largest ascent just below the tropopause, N of the SACZ • Slight but significant subsidence above the tropopause • convergence in the TTL, no export in the stratosphere Vertical mass budget • Downward flux in the lower stratosphere • Upward flux maximum at 9000m (6000m for WV) • Mass and humidity convergence in the TTL
Future work • Work with better simulation sets • Compare findings and observations • Investigate the diurnal evolution of the vertical transport