With space-based observations, remote sensing technology provides a wealth of information for understanding geophysical processes with unprecedented spatial and temporal coverage. Quantitative inference for the global carbon cycle has been bolstered by greenhouse gas observing satellites. NASA’s Orbiting Carbon Observatory-2 (OCO-2) collects tens of thousands of observations of reflected sunlight daily. These observed spectra, or radiances, are used to infer the atmospheric carbon dioxide (CO2) at fine spatial and temporal resolution with substantial coverage across the globe. Estimates of atmospheric CO2 are computed from the observed radiances using an inverse method known as a retrieval algorithm. The resulting estimates of geophysical quantities of interest are called retrievals. A key task in remote sensing science is to perform probabilistic assessment of remote sensing retrievals. However, different from many other disciplines, it is infeasible to perform physical experiments to study the quality of remote sensing retrievals thoroughly because a representative ground truth of atmospheric variables is usually lacking. Part of my research has focused on developing UQ methodologies to facilitate probabilistic assessment of remote sensing retrievals.

Spatial Mapping for OCO-2 Data

Ma, P. and Bhadra, A. (2020) "Beyond Matérn: On A Class of Interpretable Confluent Hypergeometric Covariance Functions." Journal of the American Statistical Association, Theory and Methods. In Revision.

Surrogate Modeling in Observing System Uncertainty Experiments in the OCO-2/3 Missions

Ma, P., Mondal, A., Konomi, B. A., Hobbs, J., Song, J. J., and Kang, E. L. (2020) "Computer Model Emulation with High-Dimensional Functional Output in Large-Scale Observing System Uncertainty Experiments." Technometrics. Accepted.

Spatial Downscaling in Observing System Simulation Experiments

Ma, P., Kang, E. L., Braverman, A., and Nguyen, H. (2019) "Spatial Statistical Downscaling for Constructing High-Resolution Nature Runs in Global Observing System Simulation Experiments." Technometrics, 61(3), 322-340.

Hurricane-driven storm surge is one of the most deadly and costly natural disasters, making precise quantification of the surge hazard of great importance. Current coastal flood hazard studies are often performed through a synthesis of computer modeling, statistical modeling, and extreme-event probability computation, where computer modeling is used to predict the storm surge hazard initialized by hurricanes, statistical modeling is used to determine the distribution of hurricane characteristics, and extreme-event probability is used to assess the flood hazard. These studies support development and application of flood insurance rates, building codes, land use planning/development, infrastructure design and construction, and related goals by providing hazard levels at a range of frequencies. However, current coastal flood hazard studies have suffered from several limitations including tremendous amount of computing resources, inappropriate uncertainty quantification, and lack of optimal statistical modeling. To address these issues, part of my research has focused on developing computationally efficient and rigorous UQ methodologies to facilitate coastal flood hazard studies.

Multifidelity Computer Model Emulation for Storm Surges

Ma, P., Karagiannis, G., Konomi, B. A., Asher, T. G., Toro, G. R., and Cox, A. T. (2020) "Multifidelity Computer Model Emulation with High-Dimensional Output: An Application to Storm Surge." Journal of the Royal Statistical Society: Series C. In Revision.

Objective Bayes for Multifidelity Computer Models

Ma, P. (2020) "Objective Bayesian Analysis of a Cokriging Model for Hierarchical Multifidelity Codes." SIAM/ASA Journal on Uncertainty Quantification, 8(4), 1358-1382.