Neural Stochastic Processes for Satellite Precipitation Refinement
Organizations: Neurogica Inc. · LTS, Inc. · ME-Lab Japan, Inc.
Abstract
Accurate precipitation estimation is critical for flood forecasting, water resource management, and disaster preparedness. Satellite products provide global hourly coverage but contain systematic biases; ground-based gauges are accurate at point locations but too sparse for direct gridded correction. Existing methods fuse these sources by interpolating gauge observations onto the satellite grid, but treat each time step independently and therefore discard temporal structure in precipitation fields. We propose Neural Stochastic Process (NSP), a model that pairs a Neural Process encoder conditioning on arbitrary sets of gauge observations with a latent Neural SDE on a 2D spatial representation. NSP is trained under a single variational objective with simulation-free cost. We also introduce QPEBench, a benchmark of 43{,}756 hourly samples over the Contiguous United States (2021--2025) with four aligned data sources and six evaluation metrics. On QPEBench, NSP outperforms 13 baselines across all six metrics and surpasses JAXA's operational gauge-calibrated product. An additional experiment on Kyushu, Japan confirms generalization to a different region with independent data sources.
Figures & tables
| Method | ||||||
|---|---|---|---|---|---|---|
| Quantile mapping Wood et al. (2004) | 4.073 0.184 | 2.012 0.063 | 0.885 0.027 | 0.173 0.006 | 0.288 0.014 | 0.479 0.010 |
| EMOS Gneiting et al. (2005) | 3.885 0.127 | 1.844 0.078 | 1.115 0.096 | 0.179 0.019 | 0.305 0.013 | 0.478 0.029 |
| XGBoost Chen and Guestrin (2016) | 3.741 0.129 | 1.827 0.077 | 1.062 0.088 | 0.179 0.020 | 0.284 0.016 | 0.487 0.008 |
| GWR Brunsdon et al. (1996) | 3.739 0.230 | 1.627 0.081 | 0.662 0.021 | 0.155 0.004 | 0.376 0.016 | 0.229 0.017 |
| Cokriging Cressie (1993) | 3.706 0.121 | 1.789 0.069 | 1.065 0.081 | 0.220 0.015 | 0.279 0.016 | 0.461 0.009 |
| GSMaP Kubota et al. (2020) | 3.638 0.126 | 1.826 0.076 | 1.017 0.086 | 0.179 0.020 | 0.288 0.014 | 0.483 0.014 |
| Method | |||
|---|---|---|---|
| GWR Brunsdon et al. (1996) | 1.788 | 0.655 | 0.389 |
| CNP Garnelo et al. (2018a) | 1.779 | 1.953 | 0.437 |
| EMOS Gneiting et al. (2005) | 1.738 | 1.082 | 0.169 |
| Cokriging Cressie (1993) | 1.715 | 1.077 | 0.139 |
| Linear regression | 1.688 | 0.768 | 0.356 |
| Kriging Cressie (1993) | 1.640 | 0.973 | 0.114 |
| Model | |||||||
|---|---|---|---|---|---|---|---|
| Architecture ablations | |||||||
| (1-i) | w/o Neural SDE | 2.888 0.039 | 1.487 0.053 | 0.338 0.066 | 0.062 0.018 | 0.479 0.020 | 0.509 0.022 |
| (1-ii) | Deterministic | 2.885 0.080 | 1.492 0.044 | 0.355 0.147 | 0.060 0.028 | 0.487 0.033 | 0.495 0.012 |
| (1-iii) | w/o Satellite residual | 3.141 0.089 | 1.613 0.038 | 0.252 0.024 | 0.041 0.005 | 0.475 0.018 | 0.153 0.047 |
| (1-iv) | Homoscedastic | 2.932 0.062 | 1.492 0.020 | 0.260 0.016 | 0.052 0.003 | 0.471 0.023 | 0.445 0.012 |
| (1-v) | Log-space MSE | 3.554 0.104 | 1.726 0.048 | 0.405 0.031 | 0.043 0.006 | 0.475 0.019 | 0.525 0.022 |
| (a) RMSE by intensity | |||||
| Intensity | GSMaP | GC | NSP | Rel. improv. | |
| (mm/h) | vs. GSMaP | vs. GC | |||
| 0 | 0.592 | 0.377 | 0.308 | 48.0% | 18.3% |
| 0–1 | 0.693 | 0.436 | 0.356 | 48.6% | 18.3% |
| 1–5 | 4.011 | 2.528 | 2.055 | 48.8% | 18.7% |
| 5–10 | 7.725 | 5.597 | 5.190 | 32.8% | 7.3% |
Appendix figures & tables25 assets
Supplementary material from the paper’s appendix.
Appendix
| Property | Value |
|---|---|
| Temporal coverage | January 2021 – December 2025 (5 years) |
| Total hourly steps | 43,824 (43,756 after quality filtering) |
| Grid resolution | ( 11 km) |
| Grid size | (153,400 pixels) |
| Spatial extent | – N, – W |
| Mean rainy fraction | 4.6% 2.0% of radar pixels per sample |
| Percentile | Value (mm/h) |
|---|---|
| P50 | 0.82 |
| P90 | 3.55 |
| P95 | 5.67 |
| P99 | 14.45 |
| Max | 192.20 |
| Channel | Transform |
|---|---|
| Satellite (GSMaP) | |
| Gauge observations | |
| Elevation (DEM) | |
| Context mask | Binary |
| Radar (target) | None (raw mm/h) |
| Hyperparameter | Value |
|---|---|
| Optimizer | AdamW ( , ) |
| Learning rate | (OneCycleLR) |
| Weight decay | |
| Epochs | 4 |
| Batch size | 4 per GPU ( effective) |
| Mixed precision | FP16 |
| Fold | Train | Validation | Test |
|---|---|---|---|
| 1 | 2021 | 2022 | 2023 |
| 2 | 2021–2022 | 2023 | 2024 |
| 3 | 2021–2023 | 2024 | 2025 |
| Method | |||||
|---|---|---|---|---|---|
| ViT | 2.979 | 2.010 | 1.993 | 1.275 | 0.483 |
| Quantile mapping | 1.876 | 1.073 | 1.377 | 0.623 | 0.216 |
| GWR | 1.788 | 0.812 | 0.655 | 0.252 | 0.389 |
| CNP | 1.779 | 1.559 | 1.953 | 1.815 | 0.437 |
| EMOS | 1.738 | 0.954 | 1.082 | 0.326 | 0.169 |
| Cokriging | 1.715 | 0.951 | 1.077 | 0.384 | 0.139 |
| Threshold (mm/h) | GSMaP GC | NSP | Note |
|---|---|---|---|
| 0.1 | 33 km (3 px) | 33 km (3 px) | Equal |
| 1.0 | 33 km (3 px) | 55 km (5 px) | GC better |
| 5.0 | 440 km (40 px) | 220 km (20 px) | NSP better |
| 10.0 | not reached | not reached | Both below 0.5 |
| Threshold | GC | NSP | Improv. | NSP bias | GC bias |
|---|---|---|---|---|---|
| (mm/h) | cRMSE | cRMSE | |||
| 0.1 | 3.66 | 3.54 | 3.3% | 0.52 | 0.34 |
| 1.0 | 5.41 | 4.87 | 10.0% | 0.92 | 0.41 |
| 5.0 | 9.72 | 9.24 | 4.9% | 3.54 | 2.00 |
| 10.0 | 13.38 | 11.88 | 11.2% | 4.20 | 2.49 |
| 25.0 | 21.32 | 14.70 | 31.1% | 0.23 | 3.40 |
| Category | Definition | MSE share |
|---|---|---|
| Hit bias (intensity) | pred and radar | 67.0% |
| Miss (position) | pred and radar | 14.4% |
| False alarm (position) | pred and radar | 18.6% |
| Intensity-related | 67.0% | |
| Position-related | 33.0% |
| GC accuracy | GC RMSE | NSP RMSE | NSP wins | ||
|---|---|---|---|---|---|
| RMSE (accurate) | 7,236 | 0.592 | 0.575 | 0.017 | 52.7% |
| RMSE 1–2 | 1,415 | 1.193 | 1.014 | 0.179 | 81.0% |
| RMSE 2–4 | 34 | 2.365 | 0.836 | 1.529 | 100.0% |
| Overall | 8,686 | 57.5% |
| Count | Proportion | |
| NSP better than GC | 4,994 | 57.5% |
| NSP worse than GC | 3,692 | 42.5% |
| Dominant error in 3,692 failure cases | ||
| Intensity error (hit bias) | 2,681 | 72.6% |
| False precipitation | 571 | 15.5% |
| Missed precipitation | 440 | 11.9% |
| Mode | Count | Proportion |
|---|---|---|
| Intensity error (hit bias) | 7,125 | 81.3% |
| False precipitation | 930 | 10.6% |
| Missed precipitation | 704 | 8.0% |
| Variant | ||||||
|---|---|---|---|---|---|---|
| Matched variance | 2.883 0.139 | 1.489 0.076 | 0.341 0.062 | 0.063 0.015 | 0.478 0.021 | 0.522 0.018 |
| Naive temporal penalty | 2.853 0.121 | 1.470 0.089 | 0.366 0.037 | 0.070 0.011 | 0.478 0.018 | 0.519 0.042 |
| Full transition KL | 2.818 0.062 | 1.444 0.026 | 0.393 0.047 | 0.076 0.013 | 0.478 0.021 | 0.527 0.022 |
| Event | Model | |||
|---|---|---|---|---|
| March 15, 2025 | NSP | 2.770 | 0.392 | 0.707 |
| March 15, 2025 | NSP w/o | 2.828 | 0.403 | 0.671 |
| March 15, 2025 | ConvCNP | 3.123 | 0.427 | 0.069 |
| October 30–31, 2025 | NSP | 1.892 | 0.191 | 0.539 |
| October 30–31, 2025 | NSP w/o | 2.295 | 0.323 | 0.472 |
| October 30–31, 2025 | ConvCNP | 2.166 | 0.249 | 0.035 |
| Event | Mode | Mean latency (ms) | ||
|---|---|---|---|---|
| March 15, 2025 | NSP (standard inference) | 2.776 | 0.713 | 2.60 |
| March 15, 2025 | NSP (pure SDE rollout) | 3.239 | 0.351 | 2.22 |
| March 15, 2025 | NSP (hybrid, ) | 3.102 | 0.497 | 2.92 |
| October 30–31, 2025 | NSP (standard inference) | 1.891 | 0.543 | 2.60 |
| October 30–31, 2025 | NSP (pure SDE rollout) | 2.043 | 0.313 | 2.21 |
| October 30–31, 2025 | NSP (hybrid, ) | 1.851 | 0.503 | 2.93 |
| Method | Category | Latency (ms) | Parameters |
|---|---|---|---|
| GSMaP GC | Operational product | 0.04 | — |
| Linear regression | Statistical | 1.05 | — |
| IDW | Interpolation | 1.88 | — |
| NSP | Deep learning | 2.64 | 4.19M |
| Method | ||||||
|---|---|---|---|---|---|---|
| DDPM | 7.482 2.534 | 6.441 2.365 | 8.178 2.814 | 7.605 2.555 | 0.361 0.161 | 0.060 0.039 |
| NSP (Ours) | 2.818 0.062 | 1.444 0.026 | 0.393 0.047 | 0.076 0.013 | 0.478 0.021 | 0.527 0.022 |
Neural Processes
Neural Processes learn distributions over functions from observed examples, enabling fast predictions with uncertainty for new inputs and tasks.
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