AtmosRegime-Qwen3.5-9B-RL

Qwen3.5-9B trained with reinforcement learning with verifiable rewards on atmospheric and environmental calculations, from the paper Language models misapply atmospheric formulas until trained on a few worked examples. In the paper, this training lets Qwen3.5-9B match DeepSeek V4 Flash on benchmark regime problems, both without thinking.

Code and data: https://github.com/acodercat/AtmosRegime. The other models from the paper are in the AtmosRegime collection.

Training

  • Base model: Qwen3.5-9B, thinking off.
  • Method: DAPO in verl. The reward is 1 when the program the model writes runs and returns the certified answer, otherwise 0.
  • Data: problems generated from the templates of training fold 1 (29 of the 70 mechanisms, split by cluster), each in its inside, outside and given versions.
  • Settings: learning rate 1e-6, 128 problems ร— 8 samples per step, up to 120 steps; seed 42.

Use

The model was trained on one prompt format and should be given the same one. It answers with a Python program that defines solve(). Run it with thinking disabled.

Load the model as you would its base model, Qwen/Qwen3.5-9B, and build the messages with atmoscoder_rl.prompts.chat(problem) from the code repository (a fixed system prompt and a user template that asks for solve()). Execution and grading of the returned program are in atmoscoder_rl/evaluation/.

Limitations

  • This checkpoint is one fold and one seed. Numbers in the paper average both folds and two seeds, so this model alone will not reproduce them exactly.
  • Reinforcement learning alone rarely taught the model a formula its base model almost never produced. Where training did not repair a mechanism, the model may still return the standard formula's value.
  • It was trained and tested on problems from the study's templates and benchmark. It is not a general-purpose assistant for atmospheric science.

Citation

@unpublished{ran2026regime,
  title  = {Language models misapply atmospheric formulas until trained on a few worked examples},
  author = {Ran, Maohao and Zhang, Yanting and Ma, Chendong and Song, Jun},
  year   = {2026},
  note   = {Manuscript under review}
}

Licence

Apache 2.0, as for the base model Qwen3.5-9B.

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