April 29, 2012
Photographer: Rick Stankiewicz
Summary Author: Rick Stankiewicz; Jim Foster
The photo above shows some of the fireworks from an early season, late night thunder and lightning storm that roared through southern Ontario last month. I stayed up for several hours trying to capture some of the excitement on "film". The result was a single 21-second exposure of cloud-to-cloud and cloud-to-ground lightning that appears to be tormenting a white birch tree (Betula papyrifera) in my backyard. Though two of the bolts look like they were moving through the tree they were actually about 1 mi (1.6 km) away. A number of bolts struck very close by, within 1/8 mi (0.2 km), but they struck so violently that I missed them all.
Do some trees have an affinity to attract lightning? Poplars, oak and elms apparently have a better chance to be struck than some other species. Taller trees have the greatest likelihood of being hit since they provide a better electrical conducting path for lightning than smaller specimens do. However, even a short tree is in harm’s way if, like this forlorn birch, it's situated by itself and is the highest point in a locale. When a bolt descends toward the ground, positively charged streamers (conductive discharge) from objects on the ground stretch up toward the negative (usually) leader. It makes sense that streamers from the tallest trees make the initial connection to the leader. Evidently, it's only within 100 ft (30 m) or so of the surface that objects on the surface become actual targets. Photo taken on March 16, 2012.
Photo details: Make: Canon; Model: Canon EOS DIGITAL REBEL XTi; tripod mounted with a Sigma 10-20mm lens; Exposure Time: 21; Exposure Program: Manual; Aperture Value: 6.91; F Number: f/11; ISO Speed Ratings: 100; Metering Mode: Pattern; Flash: Flash did not fire, compulsory flash mode; Focal Length: 10; White Balance: Auto white balance; Software: Adobe Photoshop 7.0 cropped from a larger area of no strikes.