Implementation date: 25.06.2013
IFS cycle 38r2 increases the vertical resolution of the model throughout the troposphere and stratosphere. It enables a better representation of physical processes, clouds, inversions and vertically propagating gravity waves, for example. The forecast impact in terms of objective verification scores against observations and analyses are summarised in the score card.
Tropospheric upper-air scores are overall slightly positive in northern hemisphere and mainly neutral for Europe and southern hemisphere. Tropics is mixed with some negative results compared to observations but neutral against analyses.
In the extra-tropics the main negative impacts are for the upper-tropospheric relative humidity (300hPa). The main positive impacts are for geopotential in the lower stratosphere, and to a lesser extent also in the troposphere.
For precipitation and temperature the overall conclusion is a slight improvement in the extra-tropics and a slight degradation in the tropics. The scores for 10m wind show neutral to slightly positive impact both in extra-tropics and tropics. There is an overall slight reduction of wind speed, most notable in Europe at 12 UTC.
No significant differences have been found between the synoptic performance of the pre-operational e-suite and the operational forecast.
Tropical cyclone tracks and intensity have been compared for all Tropical Cyclones available in the research and pre-operational e-suites. There is a slight improvement for the position errors from D+3 onwards, although this is not statistically significant. The impact is neutral for the tropical cyclone intensity.
The ensemble forecasting e-suite has run daily from 10 January onwards (00 UTC forecasts only). In general the e-suite is neutral for the ENS in terms of the spread and ensemble-mean skill for the extra-tropics. In the tropics, spread is also little changed; EM error is improved for 850 hPa temperature, and slightly worse for 850 hPa wind speed.
In terms of probabilistic scores, the CRPS is neutral for 500 hPa height, 850 hPa temperature and wind speed over Europe and the northern extra-tropics. Over the southern extra-tropics e-suite scores are better for 500 hPa height, but worse for days 1-3 for temperature at 850 hPa. In the tropics the e-suite shows a significant improvement throughout the forecast range for 850 hPa temperature, and a small but statistically significant degradation for 850 hPa wind speed, consistent with the changes in the EM error.
New model level definitions are available for L137.
See correspondence between the L91 and L137 model levels is available here.
The L137 model level data cannot be converted back to GRIB edition 1 due to limitations in the GRIB vertical coordinate table. See Cycle 37r2 Detail for further information about GRIB edition.
Users should be aware that converting the L137 model level data to GRIB edition 1 with grib_api works without error. However, the resulting GRIB edition 1 header contains incomplete
information about the vertical coordinate parameters (the grib_api key NV and the pv array) and, for grid point fields, the list of the number of points in each latitude (the PL array) is corrupted.
The increase in the number of vertical levels from 91 to 137 in the high-resolution forecast model is reflected in changes to the GRIB headers, specifically the GRIB 2 Section 4 "Product definition section":
| Section | Octets | grib_api key | Old Value | New value |
|---|---|---|---|---|
| 4 | 6-7 | NV | 184 | 276 |
| 4 | 35-nn | pv | L91 | L137 |
The GRIB model identifiers (generating process identification number) for the new cycle will be:
These are found in:
or with the grib_api key generatingProcessIdentifier.
None.
e-suite experiment number: 0062