Group seminar on 7. June, 14:15 CET
How predictable are the equatorial Kelvin waves in ECMWF deterministic system?
Paolo Andreozzi
Kelvin waves (KWs) are eastward-propagating wave patterns associated with significant variability at planetary scales of the tropical atmosphere. They are continuously forced by convective activity and are known to be essential ingredients of tropical circulation such as the El-Niño southern oscillation (ENSO), the quasi-biennial oscillation (QBO) and the Madden-Julian oscillation (MJO). Convection constitutes a challenge for numerical weather prediction models, also making the initial state typically less accurate in the tropics than in the middle latitudes, ultimately leading to a shorter prediction skill in the tropics compared to midlatitudes. During this seminar, I will present an ongoing master thesis research investigating properties of forecast errors associated with the Kelvin waves. The study uses the ECMWF deterministic forecasts covering the last three years; within this setting, 00 UTC analyses are used for the validation of 10-day long forecasts. The spectral expansion coefficients for the Kelvin waves are obtained from the operational MODES analysis of the ECMWF deterministic. Forecast error analysis in spectral space enables separation of forecast errors in terms of their phases and amplitudes. Preliminary results indicate a saturation of errors between forecast day 3 and 5 and a significant systematic error (bias) over the Maritime Continent and the Eastern Pacific. The forecasts systematically show weaker Kelvin waves than the analyses.