28 June 2005Intoduction of Cycle 29r2. This version includes the following changes
- Assimilation of rain-affected SSM/I radiances
- Set of changes to AIRS assimilation
- Use of Meteosat-8 (MSG) winds
- Jb statistics from latest ensemble data assimilation
- Refinement of surface-pressure bias correction
- Humidity analysis changes affecting spin-up & stratosphere
- Use of SMHI Baltic sea-ice analysis
- Convection changes
- Revised Gaussian sampling for EPS perturbations.
The impact of the new cycle on the performance of the forecasting system has been tested over the period December 2004 to mid-June 2005, some 200 cases.
In the free atmosphere cy29r2 shows a modest but statistically significant positive impact in the northern hemisphere and over Europe, at Z500hPa. In the southern hemisphere and over the tropics the impact is rather neutral.
There is some evidence of improved rainfall forecasts over Europe, North America and South-east Asia.
EPS testing is based on 58 cases mainly in April. The results confirm the positive impact of the revised Gaussian sampling. Improvements in the probabilistic scores (BSS and ROC for NH and EU for three different Z500 anomaly events) appear to arise mostly from the revision of the initial condition perturbations.
The new model cycle will be used throughout the Centre's forecast suites, the T511 main run, the EPS and the BC Optional Project. The atmospheric model identification number in the GRIB headers changed from 125 to 126.
Model numbers for the Global wave model remained at 116. Also for the European waters wave model the model number remained at 216.
Technical changes in this upgrade consist of:
Switch on three hourly post-processing in EPS, including archiving.
- Generate and archive in MARS special 6-hourly extreme value parameters in EPS to complement new 3-hourly parameters:
- Maximum temperature at 2 metres, MX2T6, 121
- Minimum temperature at 2 metres, MN2T6, 122
- 10 metre wind gust, 10FG6, 123
(Note: When using extreme value parameters, like Maximum temperature at 2 metres, Minimum temperature at 2 metres or 10 metre wind gust, users are advised to use the appropriate 6-hourly parameters (MX2T6, 121 / MN2T6, 122 / 10FG6, 123) if they want to cover a six hour time period. The default parameters will follow the new time step and cover a three hour period.)
- Remove following parameters from analysis: Downward UV radiation at the surface (57), Photosynthetically active radiation at the surface (58) and Convective available potential energy (59).
- Stop running sensitivity suite.