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README.md
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AIFS is based on a graph neural network (GNN) encoder and decoder, and a sliding window transformer processor,
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and is trained on ECMWF’s ERA5 re-analysis and ECMWF’s operational numerical weather prediction (NWP) analyses.
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<div style="display: flex; justify-content: center;">
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<img src="aifs_diagram.png" alt="High-level AIFS diagram" style="width: 50%;"/>
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</div>
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<div style="display: flex;">
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<img src="encoder_graph.jpeg" alt="Encoder graph" style="width: 50%;"/>
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<img src="decoder_graph.jpeg" alt="Decoder graph" style="width: 50%;"/>
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AIFS is trained to produce 6-hour forecasts. It receives as input a representation of the atmospheric states
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at \\(t_{−6h}\\), \\(t_{0}\\), and then forecasts the state at time \\(t_{+6h}\\).
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The full list of input and output fields is shown below:
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| Field | Level type | Input/Output |
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of 260,000 steps. The LR is increased from 0 to \\(10^{-4}\\) during the first 1000 steps, then it is annealed to a minimum
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of \\(3 × 10^{-7}\\).
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- **Fine-tuning I**: The pre-training is then followed by rollout on ERA5 for the years 1979 to 2018, this time with a LR
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of \\(6 × 10^{-7}\\). As in [Lam et al. [2023]](
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rollout every 1000 training steps up to a maximum of 72 h (12 auto-regressive steps).
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- **Fine-tuning II**: Finally, to further improve forecast performance, we fine-tune the model on operational real-time IFS NWP
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analyses. This is done via another round of rollout training, this time using IFS operational analysis data
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<!-- This section describes the evaluation protocols and provides the results. -->
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#### Factors
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<!-- These are the things the evaluation is disaggregating by, e.g., subpopulations or domains. -->
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<!-- These are the evaluation metrics being used, ideally with a description of why. -->
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{{ testing_metrics | default("[More Information Needed]", true)}}
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### Results
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{{ results | default("[More Information Needed]", true)}}
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#### Summary
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{{ results_summary | default("", true) }}
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## Model Examination [optional]
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<!-- Relevant interpretability work for the model goes here -->
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## Technical Specifications
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AIFS is based on a graph neural network (GNN) encoder and decoder, and a sliding window transformer processor,
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and is trained on ECMWF’s ERA5 re-analysis and ECMWF’s operational numerical weather prediction (NWP) analyses.
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<div style="display: flex;">
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<img src="encoder_graph.jpeg" alt="Encoder graph" style="width: 50%;"/>
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<img src="decoder_graph.jpeg" alt="Decoder graph" style="width: 50%;"/>
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AIFS is trained to produce 6-hour forecasts. It receives as input a representation of the atmospheric states
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at \\(t_{−6h}\\), \\(t_{0}\\), and then forecasts the state at time \\(t_{+6h}\\).
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<div style="display: flex; justify-content: center;">
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<img src="aifs_diagram.png" alt="High-level AIFS diagram" style="width: 80%;"/>
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</div>
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The full list of input and output fields is shown below:
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| Field | Level type | Input/Output |
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of 260,000 steps. The LR is increased from 0 to \\(10^{-4}\\) during the first 1000 steps, then it is annealed to a minimum
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of \\(3 × 10^{-7}\\).
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- **Fine-tuning I**: The pre-training is then followed by rollout on ERA5 for the years 1979 to 2018, this time with a LR
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of \\(6 × 10^{-7}\\). As in [Lam et al. [2023]](doi: 10.21957/slk503fs2i) we increase the
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rollout every 1000 training steps up to a maximum of 72 h (12 auto-regressive steps).
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- **Fine-tuning II**: Finally, to further improve forecast performance, we fine-tune the model on operational real-time IFS NWP
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analyses. This is done via another round of rollout training, this time using IFS operational analysis data
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<!-- This section describes the evaluation protocols and provides the results. -->
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AIFS is evaluated against ECMWF IFS (Integrated Forecast System) for 2022. The results of such evaluation are summarized in
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the scorecard below that compares different forecast skill measures across a range of
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variables. For verification, each system is compared against the operational ECMWF analysis from which the forecasts
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are initialised. In addition, the forecasts are compared against radiosonde observations of geopotential, temperature
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and windspeed, and SYNOP observations of 2 m temperature, 10 m wind and 24 h total precipitation. The definition
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of the metrics, such as ACC (ccaf), RMSE (rmsef) and forecast activity (standard deviation of forecast anomaly,
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sdaf) can be found in e.g Ben Bouallegue et al. ` [2024].
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<div style="display: flex; justify-content: center;">
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<img src="aifs_v021_scorecard.png" alt="Scorecard comparing forecast scores of AIFS versus IFS (2022)" style="width: 80%;"/>
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</div>
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. Forecasts are initialised on 00 and 12
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UTC. Shown are relative score changes as function of lead time (day 1 to 10) for northern extra-tropics (n.hem),
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southern extra-tropics (s.hem), tropics and Europe. Blue colours mark score improvements and red colours score
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degradations. Purple colours indicate an increased in standard deviation of forecast anomaly, while green colours
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indicate a reduction. Framed rectangles indicate 95% significance level. Variables are geopotential (z), temperature
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(t), wind speed (ff), mean sea level pressure (msl), 2 m temperature (2t), 10 m wind speed (10ff) and 24 hr total
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precipitation (tp). Numbers behind variable abbreviations indicate variables on pressure levels (e.g., 500 hPa), and
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suffix indicates verification against IFS NWP analyses (an) or radiosonde and SYNOP observations (ob). Scores
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shown are anomaly correlation (ccaf), SEEPS (seeps, for precipitation), RMSE (rmsef) and standard deviation of
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forecast anomaly (sdaf, see text for more explanation).
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## Technical Specifications
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