arXiv subjects

Amy Braverman

Publications and source records attributed to Amy Braverman.

9 recordsLinked to original sources

arXiv2025

Uncertainty calibration for latent-variable regression models

Uncertainty quantification is essential for scientific analysis, as it allows for the evaluation and interpretation of variability and reliability in complex systems and datasets. In their original form, multivariate statistical regression models (partial least-squares regression, PLS, principal component regression, PCR) along with their kernelized versions (kernel partial least-squares regression, K-PLS, kernel principal component regression, K-PCR), do not incorporate uncertainty quantification as part of their output. In this study, we propose a method inspired by conformal inference to estimate and calibrate the uncertainty of multivariate statistical models. The result of this method is a point prediction accompanied by prediction intervals that depend on the input data. We tested the proposed method on both traditional and kernelized versions of PLS and PCR. The method is demonstrated using synthetic data, as well as laboratory near-infrared (NIR) and airborne hyperspectral regression models for estimating functional plant traits. The model was able to successfully identify the uncertain regions in the simulated data and match the magnitude of the uncertainty. In real-case scenarios, the optimised model was not overconfident nor underconfident when estimating from test data: for example, for a 95% prediction interval, 95% of the true observations were inside the prediction interval.

stat.ME↗

arXiv2025

Machine Learning Workflows in Climate Modeling: Design Patterns and Insights from Case Studies

Machine learning has been increasingly applied in climate modeling on system emulation acceleration, data-driven parameter inference, forecasting, and knowledge discovery, addressing challenges such as physical consistency, multi-scale coupling, data sparsity, robust generalization, and integration with scientific workflows. This paper analyzes a series of case studies from applied machine learning research in climate modeling, with a focus on design choices and workflow structure. Rather than reviewing technical details, we aim to synthesize workflow design patterns across diverse projects in ML-enabled climate modeling: from surrogate modeling, ML parameterization, probabilistic programming, to simulation-based inference, and physics-informed transfer learning. We unpack how these workflows are grounded in physical knowledge, informed by simulation data, and designed to integrate observations. We aim to offer a framework for ensuring rigor in scientific machine learning through more transparent model development, critical evaluation, informed adaptation, and reproducibility, and to contribute to lowering the barrier for interdisciplinary collaboration at the interface of data science and climate modeling.

cs.LG↗

arXiv2025

Forecasting Extreme Temperatures in Siberia Using Supervised Learning and Conformal Prediction Regions

In this paper, we step back from a variety of competing heat wave definitions and forecast directly unusually high temperatures. Our testbed is the Russian Far East in the summers of 2022 and 2023. Remotely sensed data from NASA's Aqua spacecraft are organized into a within-subject design that can reduce nuisance variation in forecasted temperatures. Spatial grid cells are the study units. Each is exposed to precursors of a faux heat wave in 2022 and to precursors of a reported heat wave in 2023. The precursors are used to forecast temperatures two weeks in the future for each of 31 consecutive days. Algorithmic fitting procedures produce forecasts with promise and relatively small conformal prediction regions having a coverage probability of at least .75. Spatial and temporal dependence are manageable. At worst, there is weak dependence such that conformal prediction inference is only asymptotically valid.

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arXiv2025

A Bayesian hierarchical framework for fusion of remote sensing data: An example with solar-induced fluorescence

Solar-induced chlorophyll fluorescence (SIF) has emerged as an effective indicator of vegetation productivity and plant health. The global quantification of SIF and its associated uncertainties yields many important capabilities, including improving carbon flux estimation, improving the identification of carbon sources and sinks, monitoring a variety of ecosystems, and evaluating carbon sequestration efforts. Long-term, regional-to-global scale monitoring is now feasible with the availability of SIF estimates from multiple Earth-observing satellites. These efforts can be aided by a rigorous accounting of the sources of uncertainty present in satellite SIF data products. In this paper, we introduce a Bayesian Hierarchical Model (BHM) for the estimation of SIF and associated uncertainties from Orbiting Carbon Observatory-2 (OCO-2) satellite observations at one-degree resolution with global coverage. The hierarchical structure of our modeling framework allows for convenient model specification, quantification of various sources of variation, and the incorporation of seasonal SIF information through Fourier terms in the regression model. The modeling framework leverages the predictable seasonality of SIF in most temperate land areas. The resulting data product complements existing atmospheric carbon dioxide estimates at the same spatio-temporal resolution.

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arXiv2024

Algorithmic Forecasting of Extreme Heat Waves

This paper provides some foundations for valid forecasting of rare and extreme heat waves through a better understanding of the similarities and differences between several consecutive hot days under normal circumstances and rare, extreme heat waves. We analyze AIRS data from the American Pacific Northwest and AIRS data from the Phoenix, Arizona region. A genetic algorithm is used to help determine the most promising predictors. Classification accuracy with supervised learning is excellent for the Pacific Northwest and is replicated for Phoenix. Conformal prediction sets are considered as a way to represent forecasting uncertainty. Complications caused by endogenous sampling are discussed.

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arXiv2024

A Case Study on Quantifying Reliability under Extreme Risk Constraints in Space Missions

In this paper, we employ a Bayesian approach to uncertainty quantification of computer simulations used to assess the probability of rare events. As a case study, we assess the reliability of an Earth reentry capsule for sample return missions that must be able to withstand the reentry loads in order to land intact. Our study uses Gaussian Process modeling under a Bayesian regime to analyze the reentry vehicle's resilience against operational stress. This Bayesian framework allows for a detailed probabilistic evaluation of the system's reliability, indicating our ability to verify stringent safety goals of rare events with a 0.999999 of probability of success. The findings underscore the effectiveness of Bayesian methods for complex uncertainty quantification analyses of computer simulations, providing valuable insights for computational reliability analysis in a risk-averse setting.

stat.AP↗

arXiv2023

Evaluating the accuracy of Gaussian approximations in VSWIR imaging spectroscopy retrievals

The joint retrieval of surface reflectances and atmospheric parameters in VSWIR imaging spectroscopy is a computationally challenging high-dimensional problem. Using NASA's Surface Biology and Geology mission as the motivational context, the uncertainty associated with the retrievals is crucial for further application of the retrieved results for environmental applications. Although Markov chain Monte Carlo (MCMC) is a Bayesian method ideal for uncertainty quantification, the full-dimensional implementation of MCMC for the retrieval is computationally intractable. In this work, we developed a block Metropolis MCMC algorithm for the high-dimensional VSWIR surface reflectance retrieval that leverages the structure of the forward radiative transfer model to enable tractable fully Bayesian computation. We use the posterior distribution from this MCMC algorithm to assess the limitations of optimal estimation, the state-of-the-art Bayesian algorithm in operational retrievals which is more computationally efficient but uses a Gaussian approximation to characterize the posterior. Analyzing the differences in the posterior computed by each method, the MCMC algorithm was shown to give more physically sensible results and reveals the non-Gaussian structure of the posterior, specifically in the atmospheric aerosol optical depth parameter and the low-wavelength surface reflectances.

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arXiv2022

Statistical Downscaling of Model Projections with Multivariate Basis Graphical Lasso

We describe an improved statistical downscaling method for Earth science applications using multivariate Basis Graphical Lasso (BGL). We demonstrate our method using a case study of sea surface temperature (SST) projections from CMIP6 Earth system models, which has direct applications for studies of multi-decadal projections of coral reef bleaching. We find that the BGL downscaling method is computationally tractable for large data sets, and that mean squared predictive error is roughly 8% lower than the current state-of-the-art interpolation-based statistical downscaling method. Finally, unlike most ofthe currently available methods, BGL downscaling produces uncertainty estimates. Our novel method can be applied to any model output variable for which corresponding higher-resolution observational data is available.

stat.ME↗

arXiv2018

Spatial Statistical Downscaling for Constructing High-Resolution Nature Runs in Global Observing System Simulation Experiments

Observing system simulation experiments (OSSEs) have been widely used as a rigorous and cost-effective way to guide development of new observing systems, and to evaluate the performance of new data assimilation algorithms. Nature runs (NRs), which are outputs from deterministic models, play an essential role in building OSSE systems for global atmospheric processes because they are used both to create synthetic observations at high spatial resolution, and to represent the "true" atmosphere against which the forecasts are verified. However, most NRs are generated at resolutions coarser than actual observations. Here, we propose a principled statistical downscaling framework to construct high-resolution NRs via conditional simulation from coarse-resolution numerical model output. We use nonstationary spatial covariance function models that have basis function representations. This approach not only explicitly addresses the change-of-support problem, but also allows fast computation with large volumes of numerical model output. We also propose a data-driven algorithm to select the required basis functions adaptively, in order to increase the flexibility of our nonstationary covariance function models. In this article we demonstrate these techniques by downscaling a coarse-resolution physical NR at a native resolution of $1^{\circ} \text{ latitude} \times 1.25^{\circ} \text{ longitude}$ of global surface $\text{CO}_2$ concentrations to 655,362 equal-area hexagons.

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