Conceitos essenciais
This work presents an autoregressive generative diffusion model (DiffObs) that can produce stable long-term forecasts of global daily precipitation, exhibiting realistic tropical wave patterns and variability, including the Madden-Julian Oscillation.
Resumo
The authors introduce an autoregressive diffusion model, DiffObs, trained solely on satellite-derived global precipitation data to generate realistic long-term forecasts of daily precipitation. Key findings:
- DiffObs produces stable multi-month rollouts that exhibit a qualitatively realistic superposition of convectively coupled wave modes in the tropics, including the Madden-Julian Oscillation (MJO) and Kelvin waves.
- Cross-spectral analysis confirms the successful generation of low-frequency variations associated with the MJO and convectively coupled moist Kelvin waves with approximately correct dispersion relationships.
- Despite some secondary issues and biases, the results demonstrate the potential for next-generation global diffusion models trained on increasingly sparse and differentiated observations to enable practical applications in subseasonal and climate prediction.
- The authors note that the precipitation data used is a level 3 product integrating multiple sources, including reanalysis data, and future work could explore even lower-level satellite products.
Estatísticas
"Precipitation is observed globally via microwave sensing satellites (e.g., TRMM, Kummerow et al. (1998) and GPM, Hou et al. (2014)), and prior low-order models have proven skillful at long-range forecasts (Chen et al., 2014)."
"We collect data from June 1, 2000 to Sept 30, 2021 and aggregate all half hour samples for each day into an estimate of total daily precipitation (in mm/d)."
"We spatially coarsen the grid from 0.1◦→0.4◦with cropping in the meridional direction between 56.2◦N and 61.8◦S (296 latitudes and 900 longitudes) to avoid masking missing values at the poles."
"Data are partitioned to the years of 2000–2016 (6,041) for training and 2017–2022 (1,729) for testing, with the total samples in parentheses."
Citações
"Nonetheless, it is stable for multi-month rollouts, which reveal a qualitatively realistic superposition of convectively coupled wave modes in the tropics."
"Cross-spectral analysis confirms successful generation of low frequency variations associated with the Madden–Julian oscillation, which regulates most subseasonal to seasonal predictability in the observed atmosphere, and convectively coupled moist Kelvin waves with approximately correct dispersion relationships."