Probabilistic Downscaling of Remote Sensing Data with Applications for Multi-Scale Biogeochemical Flux Modeling

PLoS One. 2015 Jun 12;10(6):e0128935. doi: 10.1371/journal.pone.0128935. eCollection 2015.

Abstract

Upscaling ecological information to larger scales in space and downscaling remote sensing observations or model simulations to finer scales remain grand challenges in Earth system science. Downscaling often involves inferring subgrid information from coarse-scale data, and such ill-posed problems are classically addressed using regularization. Here, we apply two-dimensional Tikhonov Regularization (2DTR) to simulate subgrid surface patterns for ecological applications. Specifically, we test the ability of 2DTR to simulate the spatial statistics of high-resolution (4 m) remote sensing observations of the normalized difference vegetation index (NDVI) in a tundra landscape. We find that the 2DTR approach as applied here can capture the major mode of spatial variability of the high-resolution information, but not multiple modes of spatial variability, and that the Lagrange multiplier (γ) used to impose the condition of smoothness across space is related to the range of the experimental semivariogram. We used observed and 2DTR-simulated maps of NDVI to estimate landscape-level leaf area index (LAI) and gross primary productivity (GPP). NDVI maps simulated using a γ value that approximates the range of observed NDVI result in a landscape-level GPP estimate that differs by ca 2% from those created using observed NDVI. Following findings that GPP per unit LAI is lower near vegetation patch edges, we simulated vegetation patch edges using multiple approaches and found that simulated GPP declined by up to 12% as a result. 2DTR can generate random landscapes rapidly and can be applied to disaggregate ecological information and compare of spatial observations against simulated landscapes.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Ecosystem*
  • Models, Biological*

Grants and funding

The authors acknowledge funding from the National Science Foundation (Scaling ecosystem function: Novel Approaches from MaxEnt and Multiresolution’, DBI #1021095 and Collaborative Research: Building Forest Management into Earth System Modeling: Scaling from Stand to Continent, EF #1241881), the Marie Curie Incoming International Fellowship programme, Montana State University, and the Natural Environment Research Council, grant number ARSF 03/17 for the ASRF flight that carried the ATM sensor, as well as Brian Huntley for financial support of this mission. This work was supported by the USDA National Institute of Food and Agriculture, Hatch project 228396. Quaife is supported by the UK National Centre for Earth Observation.