GEWEX meeting GASS

1. A new case proposed to GASS : Four contrasted regimes in the Tropics over land F. Couvreux, F Guichard GEWEX meeting GASS

2. Motivations for this case of modelling • A new case proposed for an intercomparison exercise • Only a few cases over Tropical lands (only 1 for semi-arid conditions) • A variety of conditions : four different cases • Observations available to evaluate the cases 1D setup already available • A slightly different setup than usual GCSS intercomparison : 10 day-long simulation : allow for the biases to developless constrained setup,powerful identification of surface-atmosphere model biases Possible interaction with the ALMIP2 project

3. Scientific objectives • To evaluate the performance of the models over four contrasted regimes in Tropical lands  (focus on diurnal & synoptic time scales): - low heavily cloudy boundary layer (wet soil) - deep tropical convection (wet soil) with heavy precipitation - deep subtropical convection with less precipitation - semi-arid conditions (with high, less cloudy boundary layers over dry soil) • To analyze how the couplings among cloud, convection, boundary-layer and surface processes vary among those different regimes • To determine how biases change with in certain regimes

4. Methodology 1) Use observations to build a set of realistic 10-day cases (incorporating diurnal cycle and synoptic fluctuations...) 2) Simplify the set up in a way that preserve robust features of the model behaviour (e.g. as shown hereafter removing synoptic fluctuations does not modify the 10-day mean diurnally varying results)

5. Data available: (Gounou et al., BLM, 2012) • Radiosoundings (8 RS/ per day ) → good sampling of the diurnal cycle • Surface fluxes measurements (radiative & turbulent) • Cloud characteristics : ARM station (vertical profiles of clouds for two regimes), ceilometers, satellite products • Precipitation information (rain gauges, satellite products) • Aerosol content (AOD from AERONET) Before monsoon In the monsoon 10-day observations over 4 sites at 2 periods of the year: similitudes among the different periods = definitionidentification of 4 regimes

6. An example of data for the semi-arid regime

7. Cotonou SOP-1 Agadez SOP-2 Parakou SOP-1 (Gounou et al., BLM, 2012) The four contrasted regimes Avoir en tête des chiffres pour les précip des 4 régimes, en particulier Parakou SOP-2 et Niamey SOP-2, voire mettre les valeurs moyennes (mm / jour) Fig F. Guichard cloudy regime weak diurnal cycle (3K/ 0.5g/kg) stratocumulus with little rain Convective regime large diurnal cycle (6K/ 1.5g/kg) Convective systems Semi-arid regime Very large diurnal cycle (9K/ 6 g/kg) Shallow cumulus and aerosols Convective wet regime significant diurnal cycle (4K, 1g/kg) Very large precipitation large mesoscale Diurnal cycle of WHAT? Of BL thermo

8. 1D setup: Large-scale advections rv q Initial profiles Surface scheme (Couvreux et al., BLM, 2013) • Initialization & large-scale advection: from ECMWF AMMA special re-analysis (Agusti-Panareda et al, 2010) Initial conditions from ECMWF analyses __ ECMWF ana - - RS From stable to less & less stable from cloudy to semi-arid regimes, same content of moisture except the semi-arid regime

9. 1D setup: Large-scale advections rv q Initial profiles Surface scheme • Initialization & large-scale advection: from ECMWF AMMA special re-analysis (Agusti-Panareda et al, 2010) Large-scale forcings from ECMWF analyses (exemple of potential temperature tendency) Low-level advection for semi-arid regime, vertical advection for convective wet regime

10. 1D setup: Large-scale advections rv q Initial profiles Surface scheme • Initialization & large-scale advection: from ECMWF AMMA special re-analysis (Agusti-Panareda et al, 2010) 2) Surface initialization:soil properties & vegetation from ECOCLIMAP, surface properties (soil moisture & temperature) from AMMA land-surface model intercomparison project (Boone et al, 2009)

11. 1D setup: Large-scale advections rv q Initial profiles Surface scheme • Initialization & large-scale advection: from ECMWF AMMA special re-analysis (Agusti-Panareda et al, 2010) 2) Surface initialization:soil properties & vegetation from ECOCLIMAP, surface properties (soil moisture & temperature) from AMMA land-surface model intercomparison project (Boone et al, 2009) 3) Parameterizations activated: Surface scheme, radiation scheme, Turbulence scheme, shallow convection scheme, deep convection scheme

12. 1D setup: Large-scale advections rv q Initial profiles Surface scheme • Initialization & large-scale advection: from ECMWF AMMA special re-analysis (Agusti-Panareda et al, 2010) 2) Surface initialization:soil properties & vegetation from ECOCLIMAP, surface properties (soil moisture & temperature) from AMMA land-surface model intercomparison project (Boone et al, 2009) 3) Parameterizations activated: Surface scheme, radiation scheme, Turbulence scheme, shallow convection scheme, deep convection scheme 4) Simulation length: 10 day-simulation reinitialized every day or not

13. (Couvreux et al., BLM, 2013) 1D-simulations (Meso-NH) over the four regimes - - - radiosoundings ____ simulation semi-arid: too large diurnal cycle & too high boundary layer Convective: too correlated rv/ diurnal cycle and too high boundary layer Convective wet: too moist, too large  diurnal cycle and too high boundary layer Cloudy: too little rv fluctuations & too large  fluctuations; closer to saturation Different biases for the different regimes: too moist for the moist regimes, too dry for the dry regimes

14. (Couvreux et al., BLM, 2013) 1D-simulations (Meso-NH) over the four regimes Evaluation of surface budget: clear colors = observations; dark colors simulations - mean daily value synoptic variability of daily value Diurnal cycle of radiative & turbulent fluxes regimes Time evolution of cloud cover profiles observations simulations

15. Summary of the biases of Meso-NH simulation

16. Towards a simplified set-up

17. Toward a simplified set-up - - - 10 1-day run ___ 10-day run ___ 10-day constant LS advection * * * radiosoundings 10 1-day simulations re-initialised every morning for the 4 regimes • 10-day runs -> enlarge the biases already visible in 1-day runs quite informative of model biases • same conclusions with composite large-scale forcings / synoptically varying large-scale forcings • constant (no diurnally varying) large-scale forcings induce some modifications of the diurnal cycle Selected set-up : 10 day runs with composite, diurnally-varying only, large-scale forcings

18. Conclusion Set-up available for observationnaly-based1D-runs (4 different regimes for 10-day simulations with composite large-scale forcings) Observations available for evaluation: composite of the diurnal cycles A land-oriented simple but rich set-up to evaluate the coupling among parameterizations (surface, boundary layer, cloud, convection and radiation) At least, for Méso-NH, the biases involve 1) the representation of clouds (too many for the cloudy regimes, too little few for the convective and semi-arid regimes) and 2) the coupling with the surface Calendar: to propose the case for Jan 2016 Ici et ailleurs: le mot 'composite', je ne suis pas sure que les gens comprennent, c'est un cycle diurne moyen en fait 'Itemisé' pour insister

19. References Gounou A, Guichard F, Couvreux F, 2012: Observations of diurnal cycles over a West-African meridional transect: pre-monsoon and full-monsoon seasons. Boundary-Layer Meteorol 144:329–357 Couvreux F, F Guichard, A Gounou, D Bouniol, P Peyrillé, M Kohler, 2014: Modelling of the thermodynamical diurnal cycle in the lower atmosphere: a joint evaluation of four contrasted regimes in the Tropics. Boun-Lay Meteor, 150:185-214 Guichard F, Kergoat L, Mougin E, Timouk F, Baup F, Hiernaux P, Lavenu, 2009: Surface thermodynamics and radiative budget in the Sahelian Gourma: seasonal and diurnal cycles. J Hydrol 375:161–17

20. The convective regime

21. Satellite data Semi-arid regime • little rain & convective clouds • more rain & convective clouds • heavy rain & convective clouds • little precipitation & very few convective clouds Convective regime Convective wet regime Cloudy regime

22. Semi-arid regime Ceilometer data ____ occurrence from 0-3km ------ occurrence from 3-6km Convective regime Convective wet regime Low cloud bases very numerous in the convective wet regime

23. Budget of  and rv in the simulations

24. Results of simulation for Meso-NH