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CLINT - Climate Intelligence

Infilling missing data

Gridded observational climate datasets such as HadCRUT5 often contain many missing values. To tackle this problem, it is common to fill in the gaps by using the state-of-the-art kriging interpolation or the principal component analysis-based infilling. Unfortunately, these techniques are limited by the statistical information contained in the original dataset and might not be able to efficiently reconstruct large regions of missing values and complex climatic patterns. Artificial Intelligence and more specifically deep-learning based technologies give the possibility to go beyond these techniques by learning the underlying physical patterns in the data.

The method presented here is a deep-learning inpainting technique based on a U-Net architecture. It is making use of partial convolutional layers and a loss function designed to produce semantically meaningful predictions. Models are trained using climate data from reanalysis and/or historical simulations and can be used to reconstruct missing information in observational datasets with minimal computational resources.

CRAI (Climate Reconstruction AI)

CRAI is a state-of-the-art deep learning based inpainting technology to infill missing values in climate datasets.

The method

The infilling algorithm is trained with complete climate datasets and masks defining realistic regions of missing observational data.

As shown in the figure, the neural network has a U-net architecture and makes use of partial convolutional layers instead of standard convolution layers. A partial convolutional layer is a combination of two successive operations:

  • a partial convolution: $x'=\left{\begin{array}{ll}\boldsymbol{W}^T\left(\boldsymbol{X}\odot\boldsymbol{M}\right) \frac{\text{sum}(\boldsymbol{1})}{\text{sum}(\boldsymbol{M})} +b, & \text{if sum}(\boldsymbol{M})>0 \ 0, &\text{otherwise}\end{array}\right.$

  • a mask update: $m'=\left{\begin{array}{ll}1, & \text{if sum}(\boldsymbol{M})>0 \ 0, &\text{otherwise}\end{array}\right.$

where $\boldsymbol{W}$ are the convolution filter weights, $\boldsymbol{X}$ the feature values, $\boldsymbol{M}$ the binary mask values and $b$ the bias.

Compared to other inpainting methods 1, the partial convolution technique offers several advantages:

  • it operates robustly on irregular holes
  • it can infill large holes
  • it produces semantically meaningful predictions

Installation

CRAI is written in Python and based on the PyTorch framework and the NVIDIA CUDA® Deep Neural Network library (cuDNN). It is licensed under the terms of the BSD 3-Clause.

Step 1: clone the branch of the repository:

git clone -b clint --single-branch https://github.com/FREVA-CLINT/climatereconstructionAI.git

Step 2: create en environment with all the required dependencies using Anaconda

conda env create -f environment.yml

Step3: activate the environment

conda activate crai

Step4: install the Python package using pip

pip install .

Usage

The software can be used to:

  • train a model (training)
  • infill climate datasets using a trained model (evaluation)

It can be used as:

  • a command line interface (CLI):
    • training:
    crai-train
    • evaluation:
    crai-evaluate
  • a Python library:
    • training:
    from climatereconstructionai import train
    train()
    • evaluation:
    from climatereconstructionai import evaluate
    evaluate()

For more details about the execution and the input arguments, please have a look to the documentation and demo examples hosted in the repository

Footnotes

  1. Liu, G. et al., Computer Vision—ECCV 2018 Lecture Notes in Computer Science 11215, 19-35 (2018)