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June 2021 Estimating high-resolution Red Sea surface temperature hotspots, using a low-rank semiparametric spatial model
Arnab Hazra, Raphaël Huser
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Ann. Appl. Stat. 15(2): 572-596 (June 2021). DOI: 10.1214/20-AOAS1418

Abstract

In this work, we estimate extreme sea surface temperature (SST) hotspots, that is, high threshold exceedance regions, for the Red Sea, a vital region of high biodiversity. We analyze high-resolution satellite-derived SST data comprising daily measurements at 16,703 grid cells across the Red Sea over the period 1985–2015. We propose a semiparametric Bayesian spatial mixed-effects linear model with a flexible mean structure to capture spatially-varying trend and seasonality, while the residual spatial variability is modeled through a Dirichlet process mixture (DPM) of low-rank spatial Student’s t processes (LTPs). By specifying cluster-specific parameters for each LTP mixture component, the bulk of the SST residuals influence tail inference and hotspot estimation only moderately. Our proposed model has a nonstationary mean, covariance, and tail dependence, and posterior inference can be drawn efficiently through Gibbs sampling. In our application, we show that the proposed method outperforms some natural parametric and semiparametric alternatives. Moreover, we show how hotspots can be identified, and we estimate extreme SST hotspots for the whole Red Sea, projected until the year 2100, based on the Representative Concentration Pathways 4.5 and 8.5. The estimated 95% credible region, for joint high threshold exceedances include large areas covering major endangered coral reefs in the southern Red Sea.

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Arnab Hazra. Raphaël Huser. "Estimating high-resolution Red Sea surface temperature hotspots, using a low-rank semiparametric spatial model." Ann. Appl. Stat. 15 (2) 572 - 596, June 2021. https://doi.org/10.1214/20-AOAS1418

Information

Received: 1 February 2020; Revised: 1 October 2020; Published: June 2021
First available in Project Euclid: 12 July 2021

Digital Object Identifier: 10.1214/20-AOAS1418

Rights: Copyright © 2021 Institute of Mathematical Statistics

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Vol.15 • No. 2 • June 2021
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