Ground Truthing MODIS NDVI Measurements in Remote Areas of Alaska


Russell Wong

Global climate warming is amplified near the poles (Cohen et al., 2014) and at higher elevations (Pepin et al., 2015). Using remote sensing in America’s Arctic mountains, the Brooks Range, researchers have observed changes in vegetation types, growing seasons, and plant phenology over recent decades (Dial et al, 2016; Jia et al., 2003; Potter & Alexander, 2020). Most recently, Potter and Alexander (2020) documented changes to the “greenness” of the landscape using MODerate Resolution Imaging Spectroradiometers (MODIS) satellite data. “Greenness” is defined using NDVI = (IR – Red)/(Red + IR) where IR is reflectance in near-infrared bands and Red is reflectance in the visibly red region of the electromagnetic spectrum. Statewide trends in increasing greenness (“greening” and deceasing greenness, called “browning”) raise concerns about the impacts of changing ecosystems on wildlife, subsistence living, and Alaska’s wilderness quality. It is also not clear exactly what these greening and browning trends represent on the ground, because satellite sensors orbit 700 miles above the Earth and record reflectance with 250m pixels.

As part of Roman Dial’s lab at Alaska Pacific University, I am actively collaborating with Dr. Chris Potter of NASA Ames, who is lead author on the Potter and Alexander (2020) paper about greening and browning trends across Alaska during the last 20 years. We are interested in these remotely-sensed trends that are observed in remote areas indirectly affected by humans’ activities, atmospheric carbon, and climate changes. To ground-truth remote Alaska we have developed a style of lightweight travel for collecting data over hundreds of miles in Alaska’s wilderness at relatively low cost. This summer, our team collected vegetative data on the ground to assist in interpreting what the “greening” and “browning” trends actually represent. We collected geo-located vegetation data across over 100 km in the Chugach Mountains and 500 km in the Brooks Range this summer, at nearly 4,000 locations.

My role in the Dial lab is two-fold: first, I clean, curate and process much of the data that we collect. Second and for my senior project, I am writing a document that describes the methods we use to travel, leverage logistics in a cost-effective way, and collect the data. Prof. Dial has encouraged me to write my senior project titled “Ground-truthing MODIS NDVI Trends in Alaskan Wilderness” as a manuscript to submit to the peer-reviewed journal, Methods in Ecology and Evolution ( Here I am applying for funding to pay for the work I do as a data manager in Dial’s lab and the time I will spend writing this paper.


Name: Russell Wong, Undergraduate Student

Institution: Alaska Pacific University

Major: Outdoor Studies

Mentor: Roman Dial,

Award: Apprenticeship

Funding Period: 2020 to 2021