Predictability of 2-m temperature Thomas Haiden, Zied Ben Bouallegue, Martin Leutbecher, Martin Janousek European Centre for Medium-Range Weather Forecasts Reference period is 1981-2010 (March 2017 anomalies)
2-m temperature error growth: DJF 2016-17 RMSE against SYNOP NH Extratropics, 12 UTC
2-m temperature error growth: DJF 2016-17 RMSE against SYNOP against analysis NH Extratropics, 12 UTC
2-m temperature error growth: DJF 2016-17 MSE against SYNOP against analysis (2.8 K)2 NH Extratropics, 12 UTC
2-m temperature error growth: DJF 2016-17 MSE against SYNOP against analysis T850 NH Extratropics, 12 UTC
2-m temperature error growth: DJF 2016-17 MSE against SYNOP against analysis diurnal mean T850 NH Extratropics, 12 UTC
Regional variations RMSE
Regional variations RMSE Stations excluded where ∆z>150m
Regional variations SDEV
Europe SDEV
Estimating representativeness mismatch Error averaged over 1-deg boxes SDEV
Estimating representativeness mismatch Error of up-scaled forecast and obs SDEV
Estimating representativeness mismatch SDEV difference Ranging from 0.5 to 2.0 K Average value ~1 K (consistent with other studies) Short-range forecast error ~2 K
T2m forecast skill evolution (ENS) Horizontal resolution upgrades CRPS P(CRPS > 5 K) All errors Percentage of large errors CRPS decreased by ~10% Frequency of large errors decreased by ~20%
Upscaling to ~400 km (4 deg) Day 5 SDEV 12 UTC Small difference → larger scale issue Problem: strong surface inversions over snow
Large difference → smaller scale issue Upscaling to ~400 km (4 deg) Day 5 SDEV 12 UTC Large difference → smaller scale issue Problem: low stratus boundaries and persistence
TIGGE: forecasts from different centres Day 5 SDEV 12 UTC ECMWF JMA NCEP UKMO
Predictability of period means 3-day mean 5-day mean instantaneous NH Extratropics, 12 UTC, RMSE skill
Probabilistic T2m skill: weeks 2 to 4 Based on temperature anomalies (terciles) Week 2 Week 3 Week 4 Vitart (2014)
Forecast skill horizon and large-scale predictability Temporal averaging → T120 Spatial averaging ↓ T30 Buizza and Leutbecher (2015) T7 Skill beyond week 4 in predicting weekly averages of large-scale 850 hPa temperature anomalies
T2m forecast skill - summary Day 1-4 Day 5-10 Day 11-15 Week 3 and 4 Useful for 5-day or weekly means Marginal for weekly means Forecast skill: High Useful Mainly representativeness Predictability and representativeness Mainly atmospheric predictability Earth-system predictability Limited by: Improve: Model resolution Stable boundary-layer vertical mixing Low cloudiness (especially inversion-capped stratus) Soil moisture Representation of surface characteristics