PhenoCam: A Continental Observatory in Support of Monitoring, Modeling, and Forecasting Phenological Responses to Climate Change
Phenological events, such as budburst and leaf abscission, regulate many ecosystem processes and significantly influence biosphere-atmosphere exchanges and feedbacks in the climate system. Phenology is also a sensitive indicator of biological responses to climate change, particularly warming trends and altered precipitation regimes. However, phenological theory is incomplete and phenology sub-models implemented in state-of-the-art land surface schemes are overly simplistic, resulting in biased predictions. To address these needs the PhenoCam project is developing continental-scale data sets designed to quantify and characterize spatiotemporal variation in vegetation phenology. To do this, the datasets we are developing link near-surface remote sensing images collected from webcams at sub-daily time scales with lower spatial and temporal resolution imagery collected by satellite remote sensing. The observatory currently consists of 53 core sites where webcams have been installed using uniform protocols, supplemented by approximately 70 affiliated sites provided by contributors with high quality webcams with fields of view that include substantial vegetation. Core sites are frequently co-located with FLUXNET towers, supporting modeling studies that link flux measurements to phenological observations. Raw data and derived products designed to maximize information related to vegetation phenology at each site (e.g., vegetation indices) are archived in a publicly available database. Tools are also provided for users to process imagery and extract phenology time series based on their own needs and interests. The observatory is growing rapidly, and as new sites are added to the network they are included in the archive. In the future, PhenoCams will also be installed at NEON core site towers. Finally, we have ongoing efforts to calibrate and organize an image archive captured from 21,000 publicly available outdoor webcams. This paper discusses two main elements of the PhenoCam project. First, we describe the design, implementation, and data sets being generated and provided to the user community through the PhenoCam network. As part of this discussion we describe the techniques and algorithms used to produce derived products such as time series of vegetation indices extracted from webcam imagery. Second, we present results from recent studies that have used PhenoCam data to explore relationships between webcam image time series and complementary measurements of ecosystem properties and processes derived from in-situ measurements, satellite remote sensing, and eddy covariance towers. We conclude with a brief discussion of future plans and activities.
Fall Meeting, American Geophysical Union (AGU)
American Geophysical Union Publications
Friedl, M., Richardson, A., Pless, R., Frolking, S., Milliman, T., Klosterman, S., Toomey, M. and Gray, J. (2012), PhenoCam: A Continental Observatory in Support of Monitoring, Modeling, and Forecasting Phenological Responses to Climate Change, Abstract GC54A-06 presented at 2012 Fall Meeting, AGU, San Francisco, Calif., 3-7 Dec.