Datasets affected

• HRES
• ENS
• BC

Resolution

HRES/ENS/Ocean (Horizontal)

Meteorological content

• Correction of short-wave radiation interaction with clouds.
• The NESDIS satellite snow cover product was found not to be assimilated in the snow analysis and it has been re-activated.
• The snow density update in the presence of fresh snow has been corrected. In general this reduces the snow density resulting also in the reduction of the increments of snow water equivalent.
• The MODIS-based monthly albedo was corrected to be updated daily as intended. An error in the handling of invariant fields was preventing the correct updating, with the albedo being kept constant in subsequent analysis cycles.

Meteorological impact

• The above fixes are expected to improve the snow evolution especially around the snow-line and to provide a consistent seasonally-varying albedo climatology in snow-free conditions.
• Systematic improvement of temperature at 850 hPa.  The overall impact on weather parameters is small. However, the frequency of occurrence of intense rainfall events has increased resulting in better agreement with observations.
• Better representation of tropical storms, fronts, land/sea transitions which translates into better wave forecasts.
• Improved tropical cyclone track and intensity forecasts in the higher-resolution system.
• Probability scores  are consistently improved for 500 hPa height anomalies and 850 hPa temperature anomalies.
• ENS spread is in general unchanged. The ENS ensemble-mean errors are consistently lower, resulting in some overestimation of spread in terms of 500 hPa height and a better tuned spread in terms of 850 hPa temperature.

Technical content

• Deterministic forecast and analysis horizontal resolution is increased from T799 to T1279, i.e. from 25 km to 16 km.
• ENS resolutions are increased from T399/T255 to T639/T319 for Leg A/B respectively. That is to say, the first 10 days of the ENS (Leg A) will run at T639 (32 km) and the extension beyond day 10 (Leg B) will run at T319 (63 km).
• The Global wave model resolution is increased from 0.36 to 0.25 degrees in the deterministic model, and from 1.0 to 0.5 degrees for the ENS.

Resources

ECMWF Newsletter: See Newsletter 122