March Sun Angle

Ever since the winter solstice, the sun has been climbing higher and higher into the sky day by day. As we approach the equinox (and therefore spring, unless you're a meteorologist, the spring started when March did), the sun is getting stronger faster every day. One can feel the sun beating down on their backs now, especially near noon when the sun peaks at about 40 degrees in elevation. The higher the sun, the more direct the sunlight hits the surface of the Earth and the more energy is transferred.

 

An easy way to look at the energy of sunlight is to look at snowmelt patterns. The other day I noticed that the shadow of the trees were protecting snow from being zapped by the sun, even tracing out its major branches. Mind you it was in the mid 20s outside at the time this photo was taken. The sun at this point can easily warm the soil surface by 10 degrees F. This kind of freeze thaw typically does not go very deep but in the case where concrete or other heat absorbing materials are involved it can get interesting.

A Red Oak on Tower Road shelters some snow with its shadow.

One of my plant science professors Dr. Rossi once talked about how freeze thaw cycles induced by sun shining on concrete killed the grass around them. Grass around pavement really has a hard time. Foot traffic, salt, and heat all damage them. But his research showed that the sun does the killing, not the salt like many believed. The funny thing is at one point a critical amount of concrete is reached an one can have a consistent heating effect even at night and then you can zone push plants. Although Ithaca is officially zones 5b/6a, there are some small places, usually sheltered by well heated, concrete buildings that can harbor zone 6b or even zone 7a plants. It's all or nothing I guess.