USA-NPN’s Visualization Tool: Phenology maps Part 1 – Accumulated Growing Degree Days


SPEAKER: The timing of leaf
out, migration, flowering, and other seasonal
activities in many species is closely tied to
local weather conditions and broad climatic patterns. The USA National
Phenology Network is now offering two suites
of maps that shed light on plant and animal phenology
based on local weather conditions. To view the phenology maps in
the USA-NPN’s visualization tool, select the gridded
layers menu on the left hand side of the screen. This will open an
interface that will allow you to add maps of
accumulated growing degree days and the spring indices. Let’s start by looking at the
accumulated temperature maps. Heat accumulation in
the spring is commonly used to predict the timing
of phenological transitions in plants and animals. This accumulation is
typically reported in growing degree days. We can use accumulated
temperature to see how the
season is unfolding, whether this season is different
from normal, when pesticides should be sprayed, when to
watch for certain species, when to harvest fruit, and more. Let’s first load a map of
temperature accumulation for the current day. There are two base
temperatures available, 32 or 50 degrees Fahrenheit. The base temperature
is the temperature below which a particular
species will remain dormant. Which of these base
temperatures you choose will depend on your
species of interest. In general, a 32
degree base is often used by the scientific
community while a 50 degree base can be used for
crops and insect pests. Let’s first select
the 50 degree base. If we zoom in on
the map, we’ll see that the map is made up
of pixels or squares that are 2 and 1/2 kilometers wide. Each pixel has its own value for
growing degree days represented by the scale on the
bottom of the page. If you click on a– [AUDIO OUT] For example, Western
tent caterpillar larvae are active when
accumulated growing degree days are between 100 and
500 using a 50 degree base. In order to know what
time is best for managers to set out traps and spread
insecticides to control these species, we
can use the maps to know when certain
locations in the US fall within this range of
accumulated growing degree days. The colors on the map that
represent the range where we might expect to
see tent caterpillars are a medium blue
to a medium green. So places on the map
in that range of colors would be areas that managers
could search for caterpillars. Areas that are
already yellow likely no longer have
active caterpillars. And areas that are light
blue to white likely do not yet have
active caterpillars. You can also see how the
temperature accumulation for a particular day of the year
compares to a long term average for that day of the year. To do this, we’ll look at
the daily anomaly, which compares the accumulated heat
for the current day of the year to the accumulated heat for the
same day of the year averaged over 1981 to 2010. This time we’ll use a 32
degree base temperature. On June 12th, 2016,
much of the US had accumulated more
growing degree days than is normal for
this day of the year. We know this because
the colors on the map correspond to the colors on
the right end of the scale where more growing degree
days were accumulated by this day than
normally happens by this day of the year. Keep in mind that
this difference in the current year
compared to average can change throughout the year. For example, on January
1, there was no difference for that day between
the current year and the long term
average as temperature had not yet accumulated. However, on March 1st, we
see that the difference has changed with much
of the West Coast and central United
States showing more accumulated temperature. And just because you’re ahead
of schedule on the spring does not mean that you will be
ahead of schedule in the fall as the accumulation can slow
down relative to the 30 year average. The other category available
for temperature accumulations is the 30 year
average, which shows the accumulated temperature
for each day of the year averaged over 1981
to 2010 for that day. In the next video, we’ll
look at the second type of phenology map you can explore
in the visualization tool, the spring indices. We invite you to
explore these maps to answer your own questions. For more information, visit
the phenology maps page. For help, contact
support at usanpn.org.