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analysis of surface meteorological data at the Gourma sites focus on

analysis of surface meteorological data at the Gourma sites focus on radiative fluxes & thermodynamics at diurnal & interannual time scales. F. Guichard, L. Kergoat, F. Timouk, F. Baup, F. Lavenu & E. Mougin. data & products. automatic weather station of Agoufou , 2002  now

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analysis of surface meteorological data at the Gourma sites focus on

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  1. analysis of surface meteorological data at the Gourma sites focus on radiative fluxes & thermodynamics at diurnal & interannual time scales F. Guichard, L. Kergoat, F. Timouk, F. Baup, F. Lavenu & E. Mougin data & products automatic weather station of Agoufou, 2002  now wind speed, T, RH, radiative fluxes etc, 15-min sampling no pressure nor wind direction, some holes mostly outside the monsoon season aeronet sunphotometer of Agoufou, 2003  now aerosol optical depths, precipitable water, daytime & cloud free conditions automatic weather station of Bamba 2004  now with wind direction ECMWF-IFS « Agoufou grid-point » time and time-height series, horizontal resolution ~ 40 km, 60 vertical levels initially, check of data consistency characterisation of the site valuable Northern Sahel ground truth/modelling purpose (diagnostics) objectives

  2. 22 Aug Agoufou Jul 2002 275 mm qv (g.kg-1) 0 2003 430 mm 2004 185 mm 380 mm 2005 cumulative precipitation water vapour mixing ratio (qv) 2m AGL rainfall per event day of year

  3. Agoufou surface radiative budget Jul Aug 3-day running mean 2002 net radiation seasonal variations of net radiation Rnet = LW - LW + SW - SW interannual variability with stronger increase of Rnet for wet years (2003,2005) compared to dry years (2002,2004) partly explained by a stronger decrease of upward longwave flux for wet years ... but not the whole story 2003 2004 2005 rainfall per event day of year

  4. surface radiative budget, suite Agoufou Jul Aug 3-day running mean 2002 albedo seasonal variations of ALBEDO = SW / SW again interannual variability with stronger increase of Rnet for wet years (2003,2005) compared to dry years (2002,2004) differences also before the monsoon season rainfall per event 2003 2004 2005 more on albedo to come with Olivier & Laurent day of year

  5. 2002 2003 2004 2005 interannual variations of surface radiative fluxes LW -LWSW  -SW Rnet LWnet SWnet 400 200 D(Rnet ) ~ 20-35 W.m-2 for Rnet values~ 120 W.m-2 dominated by D(IR) less IR flux from a surface that is cooler during wet years weaker albedo in [2003 & 2005]/[2002 &2004] more that compensates SW decrease of [2003 & 2005]/[2002 &2004] decrease of SW consistent with a more cloudy atmosphere during wet years (W.m-2) 0 -200 Agoufou August average -400 20 10 (W.m-2) 0 -10 -20 dLW -dLW dSW -dSWdRnet dLWnet dSWnet (deviation from the 4-year mean)

  6. 2004 data 2004 ECMWF model 2005 ECMWF model 2005 data (deviation from given cstes) dLW -dLW dSW -dSWdRnet dLWnet dSWnet 20 10 0 -10 -20 -30 -40 model ~ok for 2004, not for 2005 because does too much the same for both years

  7. associated thermodynamics August Agoufou 2005 Bamba 2004 Agoufou 2004 afternoon (13-16h LT) all points saturation 2m-vater vapour mixing ratio (g/kg) 2m-temperature (K) 2m-temperature (K) 2m-temperature (K) significant afternoon decrease of water vapour mixing ratio for dry years would be broadly consistent with higher sensible heat fluxes 2004/2005 & simple convective boundary layer dynamics

  8. diurnal cycle of qe (equivalent potential temperature ~ moist enthalpy, with T& q) links with diurnal cycle of convection over land & convective indexes used for modelling, although nature of link not necessarily simple magnitude of convective destabilisation from low levels, intensity of convection precipitation at Bamba fct(hour of day) Agoufou 2005 Bamba 2004 Agoufou 2004 July August qe (K) no increase of q e during daytime for dry years (flat cycle) because of large daytime drying (may further enhances evaporation of precip)

  9. Jul-Aug 5-day running mean Bamba 2004 Agoufou 2004 Agoufou 2003 qe=350K qe=350K qe=350K 2m-temperature (°C) 2m-water vapour mixing ratio (g/kg) also larger time scale variability & nature of thetae (wetter versus drier)

  10. Agoufou July-August 2005, daily values data ECMWF model qe=347K qe=347K qv- 2m-temperature (°C) qv- 2m-water vapour mixing ratio (g/kg) T+ T- worse for low qe regimes, possible links with –missing- processes?

  11. summary, perspectives useful dataset, clear signals in meteorological data to my knowledge, not so numerous such datasets over the area synthetic diagnostics for analysing & evaluating atmospheric models too (e.g. same vein as Betts) – some caution required ECMWF: seasonal variations rather good, reasonable T & water vapour, but –for Eric- precipitation very wrong; likely other distinct stories for climate models. manage to write down a description/characterisation of the site(s) as provided by these data JJAS 2005 daily values LWnet (W.m-2) data LWnet (W.m-2) ECMWF model Plcl (mb)

  12. Bamba 2004 63 mm Agoufou 2004 185 mm albedo=0.4 albedo=0.4 albedo Bamba 2004 Agoufou 2004

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