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activity : indicator-start-of-spring-process-2018
Data for this indicator were analyzed using methods described by Schwartz et al. (2013):
Schwartz, M.D., T.R. Ault, and J.L. Betancourt. 2013. Spring onset variations and trends in the continental United States: Past and regional assessment using temperature-based indices. Int. J. Climatol. 33:2917–2922.
* The bars on the graph show the number of days by which the start of spring differs from the average start of spring during the last century.
* These values are calculated from a numerical model that simulates the accumulation of heat needed to bring plants out of winter dormancy and into vegetative and reproductive growth.
* The model is based on (1) long-term observations of lilac and honeysuckle first-leaf and first-bloom, collected by citizen science volunteers at hundreds of sites across the contiguous United States, and (2) daily minimum and maximum temperatures measured at weather stations.
* The annual start of spring can be estimated for any location where daily minimum and maximum temperatures are recorded.
* Data were plotted as an anomaly time series bar graph (relative to the 1901-2000 average)
* Data were plotted in blue for positive values (later spring) and green for negative values (earlier spring)
* Labels were added to the y-axis to indicate later spring or earlier spring and the zero line was labeled as the "1901-2000 average"
Methodology Contact: Mark D. Schwartz (University of Wisconsin-Milwaukee)
How the source was modified: Leaf and bloom observations were derived from the USA National Phenology Network "Extended Spring Indices" dataset. These data were combined with GHCN-Daily temperature data from NOAA NCEI to estimate the annual start of spring across the contiguous United States.
The input object was time bounded starting from January 01, 1900 (00:00 AM)
The input object was time bounded ending at December 31, 2017 (00:00 AM)
The input object was bounded spatially:
This activity resulted in the following :
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