Systematic model forecast error in Rossby wave structure
Gray, S. L., Dunning, C. M., Methven, J., Masato, G. and Chagnon, J. M. (2014) Systematic model forecast error in Rossby wave structure. Geophysical Research Letters, 41 (8). pp. 2979-2987. ISSN 0094-8276
To link to this item DOI: 10.1002/2014GL059282
Diabatic processes can alter Rossby wave structure; consequently errors arising from model processes propagate downstream. However, the chaotic spread of forecasts from initial condition uncertainty renders it difficult to trace back from root mean square forecast errors to model errors. Here diagnostics unaffected by phase errors are used, enabling investigation of systematic errors in Rossby waves in winter-season forecasts from three operational centers. Tropopause sharpness adjacent to ridges decreases with forecast lead time. It depends strongly on model resolution, even though models are examined on a common grid. Rossby wave amplitude reduces with lead time up to about five days, consistent with under-representation of diabatic modification and transport of air from the lower troposphere into upper-tropospheric ridges, and with too weak humidity gradients across the tropopause. However, amplitude also decreases when resolution is decreased. Further work is necessary to isolate the contribution from errors in the representation of diabatic processes.