Date of Award

5-31-2017

Document Type

Campus Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Environmental Sciences/Environmental, Earth & Ocean Sciences

First Advisor

Crystal B. Schaaf

Second Advisor

Karen Ricciardi

Third Advisor

Richard B. Primack

Abstract

Vegetation phenology is a sensitive indicator of climate change and serves as a first order control on ecosystem productivity and bio-physical properties. Global, long term, continuous, remotely sensed imagery is needed for phenological monitoring, the detection of disturbance and land cover change, and for ecological and climate modeling efforts. With the limited life span of a single satellite system, a continuous product must be derived from similarly designed sensors in order to maintain long-term data archives. This research project focuses first on the development and evaluation of the Bidirectional Reflectance Distribution Function (BRDF), Albedo, and Nadir BRDF adjusted Reflectance (NBAR) products from the Visible Infrared Imaging Radiometer Suite (VIIRS) on board the Suomi-National Polar-orbiting Partnership (NPP) satellite (2012 to present) and assesses their suitability to continue the products begun with the MODerate resolution Imaging Spectroradiometer (MODIS) observations from the Terra and Aqua satellites (2000 to present). Preliminary comparisons between MODIS and VIIRS albedo quantities indicate a maximum absolute bias of 0.0130 for NBAR and 0.0027 for shortwave broadband wholly diffuse white-sky albedo. Secondly, with the VIIRS daily BRDF, Albedo, and NBAR products established, this project then focuses on the use of both the MODIS and VIIRS NBAR products (gridded 500m spatial resolution), and Landsat 7 and 8 data (30m spatial resolution) to monitor the phenology of two distinct ecosystems: one, the water-limited Mediterranean-type oak/grass savannas and open grasslands of California, and the other, the topographically complex mixed forests of Acadia National Park in coastal Maine. The phenology transition dates detected with the finer resolution imagers agree well with phenology trends obtained from the near-surface, webcam-based PhenoCam network and from manual field surveys. The phenological dates are consistent across the different spatial resolutions in the relatively homogeneous open grasslands. In contrast, the phenological dates in the heterogeneous oak/grass savannas display more variations across scales (due to the different phenological cycles exhibited by the overstory trees and the understory grasses), as do the phenological dates in the topographically varying mixed forests of Acadia National Park (due to the compositional differences in species related to elevational zones).

Comments

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