USA NPN National Phenology Network

Taking the Pulse of Our Planet

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The USA-NPN takes a comprehensive and robust approach to data quality.

Image credit:
Ellen Denny

Data Quality

The NCO develops and delivers raw and value-added phenology data and data products to advance science, to inform decisions, and to communicate the value of phenology. These products include observational and gridded phenology data and derived products, which are processed to maximize the quality and value of the data.

We implement measures designed to maximize the quality of input data and to evaluate the data and data products we deliver to stakeholders and researchers, with a focus on plausibility, validity, and reliability. The data products that are currently available and those envisioned for development in the coming five years are described in our Data Product Catalog.

Observational data

Observational plant and animal data in the National Phenology Database are collected by a national pool of observers ranging from professional researchers to high school students to dedicated retirees, who participate in Nature’s Notebook. These participants collect data on a scale that would not otherwise be feasible. To ensure that the observational data in National Phenology Database are robust for use in scientific analyses and decision-making, we employ a range of quality assurance (QA) processes to improve species identification, phenophase status evaluation, and data entry. In turn, quality control (QC) processes evaluate and flag data according to standards of plausibility, validity, and reliability.  QA and QC processes and activities are described in Appendix 2 of the USA-NPN Observational Data Documentation. 

This dashboard summarizes real-time data quality metrics for our observational data, including information on how frequently geographic data is corrected, how many observation records are flagged with a conflict, how many status observations include intensity measures, and the temporal precision with which estimates of phenophase onset and end are captured.

Quality Control Measure 2009 to 2014 2015 2016 2017 2018 2019 2020 All Time
Elevation (%) 0.9 0.46 0.08 0.29 1.74 0.06 0.04 0.68
Coordinates -- 4/4 6/8 6/10 6/9 4/4 11/12 42/55
One-Observer Status Conflict (%) 0.02 0.03 0.04 0.03 0.07 0.08 0.03 0.05
Multi-observer Status Conflict (%) 0.97 1 3 3 1 1 0.54 1
Intensity Records (%) 79 79 82 81 82 83 84 82
No prior/following "No" (%) 33 24 21 22 25 20 29 25
No < 8 days (%) 44 53 56 55 51 55 46 51
No in 8 - 14 days (%) 12 13 14 13 13 13 13 13
No in 15 - 30 days (%) 6 6 6 6 6 6 6 6
No in > 30 days (%) 5 5 4 4 5 4 6 5

Observational data are accessible through the Phenology Observation Portal and via web services.

Gridded data products

The USA-NPN NCO offers a growing suite of historical and forecasted gridded data products including maps of Accumulated Growing Degree Days (AGDDs) and the Spring Indices. As with all gridded data products, the USA-NPN gridded products inherently contain uncertainty or error arising from multiple sources, including error propagated forward from underlying climate data and from models used in the calculations. We aim to identify and report measures of uncertainty to support the use of these data products in research and decision-making. The sources of uncertainty and the actions employed by the NCO to quantify this uncertainty are described in detail in the USA National Phenology Network Gridded Products Documentation.

To assess the level of uncertainty in the USA-NPN AGDD products we compare our calculations of Accumulated Growing Degree Days to those made using measurements from U.S. Climate Reference Network stations in the AGDD Uncertainty Assessment Dashboard. Validation of the Extended Spring Index model, and gridded implementations, have been published (see references here: Extended Spring Indices). To assess plausibility of the Spring Index products, we compare observed lilac and honeysuckle phenology to modeled output in the Spring Index Plausibility Dashboard. Additional explorations of uncertainty and error for these products are in development.

The gridded map products offered by the USA-NPN NCO are available for download as images and raster files through the Geospatial Request Builder and via OGC-compliant web services.