 Hello, I've driven about nine hours north from State College into the northern part of the Adirondack Park in upstate New York. And I'm here to visit my sister, who I've just skied with out on the middle Saranac Lake. In the background you can see one of our favorite mountains, Ampersand Mountain. Spody stumbling around in front of us. But I thought that while I'm here, I would take advantage of the wintery weather that they're experiencing here that we're not having in central Pennsylvania to talk to you a little bit about climate and also about the hydrologic cycle and some of the ways in which the forests interact with the critical zone during the winter season. The difference between weather and climate is an elusive concept for some people. Now I'm going to try to describe it to you. Recall that just moments ago the sky was clear and the sun was out to the east but now we're in the middle of a nice snowfall. This is an example of the weather. Weather to me describes the physical conditions in the atmosphere and those conditions can change rapidly on timescales of hours to days from region to region and also through time. On the other hand, it describes prevailing weather trends in a region typically considered over years to decades. So while the weather is different today between the Adirondacks and central Pennsylvania both regions are characterized as having a humid temperate climate. One of the things that's unique about the Adirondacks compared to central Pennsylvania is the mountains and the topography and the elevation. So this geographic component is important to understanding climate so mountainous regions further from the coastlines typically have colder, longer winters than areas closer to the coast at lower elevations like central Pennsylvania. In mid to high latitude regions that experience a truly cold winter season critical zone processes slow down and in some cases cease to function. For example, in the frozen Adirondacks the water that in other seasons would percolate into the subsurface's groundwater and flow through the rivers and lakes of the region is temporarily stored as ice and snow at the surface until temperatures warm, thaw occurs and critical zone processes begin anew. We'll reconsider seasonality in later lessons when we discuss the hydrologic cycle and biotic functioning of the critical zone.