Have you ever seen a tree snap due to high winds or a lightning strike?
Back in March 2020, I saw a beautiful Bradford Pear tree starting to bloom with its pale yellow-white blossoms. I thought that this would be a very nice, isolated tree to take a NASA GLOBE Observer tree height observation.
Tree Height - March 15, 2020, 19.41m, Bradford Pear, Salisbury, Maryland USA
Let's fast forward to August 4, 2020. At this time, the Mid-Atlantic region of the United States was being greatly affected by the remnants of Hurricane Isaias. By this time, the hurricane was downgraded to Tropical Storm Isaias, but still contained heavy precipitation and very strong winds.
Precipitation map on August 4, 2020 of Tropical Storm Isaias. The orange and yellow represents the most precipitation. Salisbury, Maryland, located with the red star, is in the dark green region. This is a heavy rain area.
At approximately 1:30pm EDT, a neighbor texted me the following, "It's a sad day today, wind took down half of the Bradford Pear tree next to the pond." A sad day indeed! Bradford Pear trees are known to be weak-structured and not very resilient. Bradford Pears have a life expectancy of about 18 to 25 years, so they grow at a fast pace, with each branch and twig sprouting upwards. This causes many limbs to crowd around the trunk, or base, of the tree. The higher the branches grow, the weaker they become.
Let's fast forward again, but this time to February 3, 2021. Just after an evening snowfall on February 2, 2021, I wanted to do another tree height observation to see just how much the tree has changed over almost a year's time. Wait until you see the difference!
Tree Height - February 3, 2021, 19.41m, Bradford Pear, Salisbury, Maryland USA
Comparison of the Bradford Pear Tree Heights - March 15, 2020 and February 3, 2021, including a precipitation map of Tropical Storm Isaias and the photon height data from ICESat-2.
Look at the difference in the tree height between March 15, 2020 and February 3, 2021. The tree height went from 19.41m to 16.61m! Can you see the difference in the size and shape of the tree? Can you see why the tree height decreased by 2.8m following the August 4, 2020 Tropical Storm Isaias weather event? This really highlights the effects that wind can have on tree height, especially on a historically-weak tree species.
Now, let's take this a bit further. As you know, the NASA Ice, Cloud, and land Elevation Satellite-2 or ICESat-2 Mission also measures tree canopy height from space. You also know that ICESat-2 uses an onboard laser altimeter system called the Advanced Topographic Laser Altimeter System or ATLAS, to measure the heights of object on Earth, including sea ice, ice sheet, glaciers, sea level, landforms, and trees.
So, I decided to see if ICESat-2 happened to measure this tree, and to my delight, it did! What makes this super-exciting is that this is an isolated tree. What does this mean? The ICESat-2 laser photons that are fired from the satellite to Earth spread out when traveling the 300 miles from the satellite to the Earth. When the photon hits the Earth, it has an approximate 14m diameter footprint on the ground. If there happens to be multiple trees in that footprint, ICESat-2 takes an average tree height from all the trees within that footprint. The Bradford Pear tree happened to be an isolated tree, meaning that it was the only tree height captured, by ICESat-2 in the photon footprint. Exciting stuff!
Looking at the height of the Bradford Pear Tree from ICESat-2, and the NASA GLOBE Observer Trees Tool
On July 31, 2019, ICESat-2 measured the Bradford Pear at 19.13m, just a tiny bit smaller (only 0.28m difference) than I did using the NASA GLOBE Observer on March 15, 2020. This is a very close match of tree height data from the ground (NASA GLOBE Observer) and space (ICESat-2).
My hopes is that ICESat-2 will once again take a tree height measurement of the Bradford Pear. We can then see how close I am with my post-Tropical Storm Isaias wind damaged tree height observation of 16.61m. Until then, keep looking up at the trees.
