
IPC 15 full program
Session 4
Precipitation variability across scales – transforming observations to applications.
Conveners: Christian Kummerow (Colorado State University), Efi Foufoula-Georgiou (UC Irvine).
June 16, 2026
A Community Baseline and Benchmark for Machine-Learning Satellite Precipitation Retrievals Authors: Simon Pfreundschuh (Colorado State University); Malarvizhi Arulraj (University of Maryland); Yashraj Upase (Indian Institute of Technology Hyderabad); Veljko Petković (University of Maryland); Jackson Tan (University of Maryland); Lisa Milani (University of Maryland) Corresponding author email: simon.pfreundschuh@colostate.edu Abstract: Recent machine-learning (ML) approaches for satellite precipitation retrieval show promising performance and are increasingly considered for operational use. However, differences in training data, validation strategies, and sensor characteristics make it difficult to compare published methods or to distinguish genuine methodological advances from dataset-dependent accuracy variations. To address this limitation, the International Precipitation Working Group (IPWG) has developed a standardized benchmark for precipitation detection and estimation from satellite observations. The dataset combines multi-sensor satellite measurements, ancillary information, and gauge-corrected ground-radar reference data, and provides a consistent evaluation protocol across diverse climate regimes. Building on this framework, we introduce a publicly available baseline retrieval and systematically assess key design choices in neural-network-based precipitation retrievals. Across architectures, training strategies, and model complexities, we find that incorporating spatial context provides the largest performance gains, whereas specific architectural refinements yield comparatively small improvements. The resulting baseline achieves robust performance across sensor types for both precipitation detection and quantitative estimation. By providing both a uniform benchmark and an open baseline model, this work enables reproducible comparison of ML retrievals and clarifies which methodological developments lead to meaningful improvements. The framework establishes a reference point for future algorithm development and supports more transparent evaluation of machine-learning precipitation retrievals. Within this benchmark, performance gains are dominated by the use of additional observational context rather than architectural complexity, suggesting that future improvements will primarily arise from better exploitation of available information rather than further model refinement.
An Artificial Neural Network QPE Scale Correction Model for the WSR-88D Weather Radar Network Authors: Edwin Lee Dunnavan (Cooperative Institute for Severe and High-Impact Weather Research and Operations); Marcus Johnson (Cooperative Institute for Severe and High-Impact Weather Research and Operations); John Krause (Cooperative Institute for Severe and High-Impact Weather Research and Operations); Alexander Ryzhkov (Cooperative Institute for Severe and High-Impact Weather Research and Operations); Pengfei Zhang (Cooperative Institute for Severe and High-Impact Weather Research and Operations) Corresponding author email: dunnavel@ou.edu Abstract: This study combines the latest polarimetric radar rain-rate relations with an artificial neural network (ANN) model to implement scale-correction and enhance WSR-88D radar surface rain rate estimations. These recent advancements in rain rate (R) estimation utilize additional radar variables, such as specific attenuation (R(A)) and specific differential phase (R(Kdp)), which can significantly improve rainfall estimates compared to traditional reflectivity-based estimates (R(Z)). However, all of these methods remain susceptible to pragmatic beam-specific issues, such as terrain-induced beam blockage, and scale-dependent issues, such as beam height increase with range. To address these scale- and beam-dependent issues, the ANN model was trained on more than 800 hours of WSR-88D CONUS data across 72 unique sites, utilizing over 40,000 surface rain gauge measurements of 1-hour accumulations. The ANN model incorporates all available polarimetric radar products, including those from multiple available VCP tilts, as well as gridded thermodynamic variables such as temperature and relative humidity, which the Radar Product Generator (RPG) derives hourly from the Rapid Refresh (RAP) numerical weather prediction model. Following training, the ANN model reduces the 1-hour accumulation root mean square error of the test dataset from 4.5 mm to 3.6 mm. Future work will focus on incorporating this model as a product within the RPG.
Estimation and Analysis of Short-Duration, Warm Season Rainfall Extremes in the Eastern US Based on Polarimetric Radar Authors: Jim Smith (Princeton Univeristy); Witold F. Krajewski (University of Iowa); Russ Schumacher (Colorado State University) Corresponding author email: jsmith@princeton.edu Abstract: Some of the largest sub-daily rainfall measurements in the world have been made in the Appalachian region of the Eastern US. We examine the upper tail of short-duration, small-area rainfall through analyses of polarimetric radar observations from the most extreme storms during the polarimetric era of the US NEXRAD system (2012 – present). For time scales ranging from 10 minutes to 6 hours the largest rainfall estimates from polarimetric radar in the Appalachian region are almost a factor of 2 smaller than the largest measurements from bucket surveys (principally before 1950). We examine storm-scale and mesoscale processes that control short-duration, small-area rainfall extremes and contribute to errors in polarimetric rainfall estimates. Storms producing peak short-duration rainfall are invariably on the extreme high end of the convective intensity spectrum, a feature that is central to both the space-time distribution of extreme rainfall and error characteristics of polarimetric radar estimates of rainfall. We also examine the role of complex terrain in controlling rainfall extremes in the Appalachian region and in dictating errors in polarimetric estimates of rainfall. Results are motivated by the challenges of developing the next generation of weather radars in the US, hydrologic forecasting of extreme floods and implementing methods for Probable Maximum Precipitation (PMP) estimation and precipitation frequency analysis.
Beta–Lognormal Canonical Cascades and Breakdown Coefficients for Temporal Disaggregation: Application to High Resolution Rainfall over Sardinia Authors: Stergios Emmanouil (Department of Civil, Environmental & Construction Engineering, University of Central Florida); Anastasios Perdios (Department of Civil Engineering, University of Patras); Alin A. Carsteanu (Escuela Superior de Física y Matemáticas Instituto Politécnico Nacional); Roberto Deidda (Dipartimento di Ingegneria Civile, Ambientale e Architettura Universitá degli Studi di Cagliari); Andreas Langousis (Department of Civil Engineering, University of Patras) Corresponding author email: stergios.emmanouil@ucf.edu Abstract: Multiplicative cascade models are widely used for the temporal disaggregation of rainfall due to their ability to reproduce multifractal scaling, a property that has been found to accurately describe the dependence of rainfall statistics on the observation scale. Recent work has shown that while canonical (i.e. expectation conservative) and microcanonical (i.e. strictly conservative) multiplicative cascade formulations are not generally interchangeable, their parameters are interlinked. In this study, we apply both formulations to model rainfall as a beta-lognormal multifractal process fitted to empirical data. The fitted models (i.e. canonical and microcanonical cascade alternatives) are used to temporally disaggregate rainfall over Sardinia (Italy), and their performance in reproducing the statistical scaling of rainfall is evaluated using high resolution raingauge measurements from the island’s dense network. The analysis highlights the sensitivity of disaggregation outcomes to model setup, while underscoring the importance of appropriate cascade formulation and model selection in rainfall disaggregation applications.
Beyond Stationarity: Uncertainty in Estimating Probable Maximum Precipitation under Climate Change Authors: Hoyoung Cha (Korea University); Wooyoung Na (Dong-A University); Jongjin Baik (Korea University); Changhyun Jun (Korea University) Corresponding author email: ckghdud2@korea.ac.kr Abstract: On a global scale, unexpected extreme rainfall events are becoming more frequent due to climate change, raising questions about the validity of conventional Probable Maximum Precipitation (PMP) estimates. This study investigates the uncertainty and non-stationarity of PMP in the Republic of Korea under future climate scenarios. Using rainfall projections from 95 Automated Synoptic Observing System (ASOS) stations (2021–2100), PMP is estimated with the Hershfield method, applying both frequency factors derived from the Annual Maximum Series (AMS) (case 1) and a fixed frequency factor of 15 (case 2). Return periods are assessed using Gumbel distributions with parameters estimated by probability weighted moments. Temporal trends are examined across six overlapping 30-year windows under SSP1–2.6, SSP2–4.8, SSP3–7.0, and SSP5–8.5 scenarios. Results indicate that most stations show either a steady increase in PMP or a decreasing trend toward 2100, regardless of scenario. PMP ranges from 89–954 mm (case 1) and 234–1,710 mm (case 2), while hydrometeorological methods (856–1,655 mm) are generally higher. Return periods span from 5 years to over 37 million years, reflecting large uncertainties driven by differing frequency factors. These findings underscore the limitations of conventional PMP estimation and highlight the need for more robust approaches that account for uncertainty and non-stationarity in hydrological design and climate risk management.
Session summary
Back to full program.