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WP5.3 Assessment of Forecast Quality ENSEMBLES RT4/RT5 Kick Off Meeting, Paris, Feb 2005. Richard Graham. Met Office seasonal/multi-annual/decadal runs. Model. GloSea (HadCM3) later HadGEM. DePreSys (HadCM3). Current oper. range. Seasonal (6months). decadal. Hindcasts
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WP5.3 Assessment of Forecast Quality ENSEMBLES RT4/RT5 Kick Off Meeting, Paris, Feb 2005 Richard Graham
Met Office seasonal/multi-annual/decadal runs Model GloSea (HadCM3) later HadGEM DePreSys (HadCM3) Current oper. range Seasonal (6months) decadal Hindcasts period: 1991 - 2001 GloSea: ->7m: 1st/15th May/Nov 1st June/Dec ->14m: 1st May/June/Nov/Dec -> 10y: 1st May 1964, 1994 DePreSys: -> 10y: 1st May/Nov (all years) assimilation method Conventional (OI type) calibrated anomalies 9-ensemble experiments 1991-2001 pert. ODA pert. phys. pert. phys. lagged avge lagged avge
RT5.3 Analysis • Main aim (18m): compare benefits of systems/methods • Diagnostics/tools, seasonal-range • Key variables: temperature, precipitation • Investigate bias and predictability (as DEMETER, WMO SVS) • Adapt score comparison suite from CGCM/AGCM study • Focus: • To what range is seasonal (3-month-mean) predictability feasible? • Comparative skill for ‘extremes’ (outer quintile, decile) (overlap RT4 • Stability with varying starts (1st and 15th of month) • Compare skill against persistence (as well as climatology) • Statistical significance • Link to European Flood and Drought IP • Multi-annual • Adapt and apply assessment methods used for seasonal range • How quickly does model converge with climatology? • Look at skill for ‘slow’ variables: upper ocean heat content, THC, ENSO
Example: model comparison GloSea Vs HadAM3 ROC for outer quintile precip 1-month lead, JJA
Upper tercile Vs Upper quintile ROC score Skill for upper quintile, MAM T2m precip Skill for upper tercile, MAM T2m precip
Met Office GloSea CGCM 15-member hindcasts to 6 month range start each month 1987 - 2001 SST in Niño regions (tropical Pacific) monthly climatology <forecast> - <obs> Plot for multi-annual runs –upper ocean heat content intrinsic envelope? CGCM forecast drift (SST)
Parameter Perturbations • Large Scale Cloud • Ice fall speed • Critical relative humidity for formation • Cloud droplet to rain: conversion rate and threshold • Cloud fraction calculation • Boundary layer • Turbulent mixing coefficients: stability-dependence, neutral mixing length • Roughness length over sea: Charnock constant, free convective value • Convection • Entrainment rate • Intensity of mass flux • Shape of cloud (anvils) • Cloud water seen by radiation • Dynamics • Diffusion: order and e-folding time • Gravity wave drag: surface and trapped lee wave constants • Gravity wave drag start level • Radiation • Ice particle size/shape • Sulphur cycle • Water vapour continuum absorption • Land surface processes • Root depths • Forest roughness lengths • Surface-canopy coupling • CO2 dependence of stomatal conductance • Sea ice • Albedo dependence on temperature • Ocean-ice heat transfer