NEWS!
Reminder: Access to the operational PREd will be closed at 9 UTC on 10 May. Any changes to the operational requirements can be implemented after 10 UTC on 12 May
Recording of the webinar on Cycle 47r2 performance, products and technical aspects is now available
- Updated information on recommended software versions
- Graphical products based on 47r2 test data will become available on 6 April
Final webinar, focusing on latest model verification, new products, handling of ENS model level increase in dissemination and technical aspects, has been scheduled for
16 April 2021 at 8:00 (UTC). Join the webinar
Recording of the webinar on ENS model level handling in dissemination is now available
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Implementation timeline
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Meteorological content
In this model cycle single precision for ENS (forecast up to d+46 and hindcast) and HRES (forecast) will be introduced. The idea to use single precision in the IFS emerged from a research project at the University of Oxford and was tested in the OpenIFS model, a portable version of the IFS for research and educational use at institutes and universities. Followed by further research carried out at Météo-France and ECMWF it was shown that it is possible to significantly reduce the arithmetic precision of many of the calculations performed in numerical weather prediction models without compromising the quality of weather forecasts. ‘Single precision’ forecasts have the advantage of being computationally less expensive than traditional ‘double precision’ forecasts. Such efficiency savings will greatly facilitate the introduction of higher-resolution ensemble forecasts and other model improvements in line with ECMWF’s Strategy to 2025. The article 'Progress in using single precision in the IFS' provides additional information.
Moreover, the ENS vertical levels will be increased to 137 to bring it in line with HRES.
Meteorological impact
Evaluation of 47r2
The two changes at 47r2 were a reduction to single precision in our HRES and ENS forecasts and (with the computational savings made) an increase from 91 to 137 levels in the ENS forecast. Our deterministic and ensemble analyses, including background forecasts, remain at double precision, and so are unaffected.title | CURRENT EVALUATION >> |
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Score cards
The change to single precision is neutral in terms of HRES skill (less than a 0.3% change is typical for the troposphere, and the frequency of statistically significant differences is in line with what one might expect by chance), but there are benefits of the increased levels in the ENS.
The ensemble score card is overwhelmingly positive and statistically significant (occasional negative changes are small in magnitude.)
Scorecards presenting the new cycle performance are regularly updated: Tropical Cyclones inENS vertical profile product at 20°S 90°W (VT = 20210123 at 12UTC)
The extra levels mean that sharper inversions can be resolved. For example, the ensemble vertical profile product now uses 34 model levels below 700hPa instead of the previous 22. The 47r2 test profile, which uses the new mapping of model levels, shows little obvious change although the thermal inversion is indeed a little sharper at 47r2. Users will need to ensure that they extract the correct model levels when creating their own forecast products. Over the testing period, the root-mean-square-error of the ensemble-mean T850 is reduced in the subtropics.
ENS vertical profile tephigram product for forecasts started on 20210121 at 0UTC and at lead time 60h, for temperature (red) and moisture (dewpoint, green). Shaded bands denote the minimum, 25th and 75th percentiles and maximum for temperature and dewpoint distributions at each level. The median value is shown by a thin solid line. A thick solid line represents HRES and a thick dashed line represents the Control.
Zonal-mean Temperature bias in Control forecast (day 10)
The extra levels also allow the ENS to better resolve gravity waves in the vertical, and this helps reduce the cold bias in the upper troposphere / lower stratosphere, e.g. by about 33% at day10. This improvement persists into the extended range.
Zonal means of mean temperature errors at a lead time of 10 days in the ensemble control forecast. More saturated colours indicate statistical significance at the 5% level using a t test accounting for temporal correlation. Evaluated over all forecasts started 20191125-20200228 and 20200510-20201107.
Madden Julian Oscillation (assessment of bivariate index)
In the extended range we also see the amplitude of the Madden-Julian Oscillation (MJO) being better sustained (amplitude loss by day 15 is now ~15% rather than previously ~20%), increased MJO spread and improved scores. Changes come mostly from improvements in tropical zonal winds at 200hPa.Score differences (47r2 minus 47r1) for the Wheeler and Hendon (2004) bivariate Real time Multivariate Madden Julian Oscillation (RMM) index based on reforecasts initialised at the start of each month for the period 1989-2016. The differences shown are for ( i ) the fair version of the Continuous Rank probability Skill Score (FCRPSS), (ii) the bivariate anomaly correlation (CORR), (iii) the bivariate root mean square error (RMSE), (iv) the bivariate spread of the ensemble with
New parameters
The table contains the list of parameters expected to be available with the model implementation. They will be available as part of the test data.
Param
ID
Short
Name
Name
Unit
Component
& type
GRIB edition
Level
type
MARS
Added to Catalogue
ecCharts
Dissemination
1
sfc
aluvpi
UV visible albedo for direct radiation, isotropic component
(0-1)
ENS CF
1
sfc
aluvpv
UV visible albedo for direct radiation, volumetric component
(0-1)
ENS CF
1
sfc
aluvpg
UV visible albedo for direct radiation, geometric component
(0-1)
ENS CF
1
sfc
alnipi
Near IR albedo for direct radiation, isotropic component
(0-1)
ENS CF
1
sfc
alnipv
Near IR albedo for direct radiation, volumetric component
(0-1)
ENS CF
1
sfc
alnipg
Near IR albedo for direct radiation, geometric component
(0-1)
ENS CF
1
sfc
sdfor
Standard deviation of filtered subgrid orography
m
ENS CF1
1
sfc
sdor
Standard deviation of orography
m
ENS CF1
1
sfc
isor
Anisotropy of sub-gridscale orography
-
ENS CF1
1
sfc
anor
Angle of sub-gridscale orography
radians
ENS CF1
1
sfc
slor
Slope of sub-gridscale orography
-
ENS CF1
1
sfc
lsrh
Logarithm of surface roughness length for heat
-
1 Available at step 0 only.
Changes to existing BUFR parameters
HRES/ENS
Technical information is available at Update to Tropical Cyclone tracks.
Increase of ENS vertical resolution to 137 model levels
With this cycle upgrade the number of vertical model levels in ensemble forecasts (ENS) increases from 91 to 137, bringing it to the same vertical resolution as HRES. The L137 model level definitions and the correspondence between the L91 and L137 model levels are available online. Please note that the L137 model level data cannot be converted back to GRIB edition 1 without the loss of information.
Users getting ENS data on model levels are advised to check their data requests and processing. Getting all model levels, 137 instead of 91, will increase the amount of data by a factor of 1.5. This will affect resources like disc space, array sizes, processing and transfer times. Users should adapt any limits and requirements, e.g. wallclock time, memory, accordingly.
Users who are currently retrieving all 91 model levels from MARS wishing to retrieve the same number of equivalent levels from Cycle 47r2 could specify
...levtype=ml,
levelist=1/2/4/6/7/9/10/12/14/15/17/19/20/22/ all users of ENS model level data are urged to test their applications using the available test data as described below.
Options 2 and 3
Option 2 or 3 time-critical applications can be tested with theIFS Cycle 47r2 test data retrieved from MARS or received in Dissemination.ResourcesMultimedia | ||||||
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