Topography and Microclimates
Hello, readers!
Last edition, we dipped our toes into the three astronomical cycles that drove the advance and retreat of massive, mile-thick continental ice sheets for millions of years. These cycles relate to Earth’s obliquity (tilt on its axis), eccentricity (how circular or ovular our orbit is), and axial precession (the top-like wobble in Earth’s revolutions). These cycles interact in ways that sometimes dampen (decrease) and sometimes amplify (increase) the total amount of sunlight reaching the northern hemisphere. Less sunlight = more ice.
We will talk more about ice ages in the future because they are one of Earth’s coolest (pun intended) natural events. Today, however, we will define key terms and discuss the power of the landscape in shaping microclimates.
WEATHER is the movement of heat and moisture around the planet in currents of air and water driven by pressure gradients that fluctuate day to day and hour by hour. CLIMATE is the overall temperature and precipitation regime of a location, averaged over time (decades or longer). Put another way, climate is your wardrobe, and weather is the outfit you wear for the day. We have high-resolution climate data for 150 years, and we have innumerable paleoclimate proxy records that offer data hundreds of millions of years old. Time series data are data collected over a period of time long enough to deduce statistical averages and overall trends.
We can clearly see a stark, rapid upward trend in both atmospheric CO2 and global temperature, and these movements are increasing exponentially. This is bad. Like, really, really bad. Like, extinction-level bad. Even though we should be entering an astronomically-driven cooling period, we see planet-wide decreases in ice coverage as every studied glacier in the world (except one in Greenland) is melting faster than it is regenerating (https://climate.nasa.gov/blog/2925/why-a-growing-greenland-glacier-doesnt-mean-good-news-for-global-warming/). This is altering ocean currents that have cycled uninterrupted for millions of years. We, as a human race, are not prepared for these changes. Our infrastructure is not prepared, and our supply chains are weak and fragile. We must adapt if we want to survive.
I have my fingers crossed that this winter brings cold, wet, La Niña conditions to our beautiful slice of NorCal. We desperately need snow. Have you ever wondered why snow falls on top of mountains instead of in the bottom of river valleys? It’s due to something called the “adiabatic lapse rate”, or the inverse relationship between temperature and altitude in the troposphere. The higher up in the troposphere you travel, the colder it gets! I said “inverse” relationship, because as one variable increases (altitude), the other variable decreases (temperature). The adiabatic lapse rate varies slightly with relative humidity, but generally speaking, for every 1,000 feet of altitude you gain, you lose about 3.6 degrees Fahrenheit (https://www.sciencedirect.com/topics/earth-and-planetary-sciences/adiabatic-lapse-rate). This is why it snows on mountain peaks first and, as the weather gets colder, the snowline creeps down the mountain flanks.
Mountains also have the unique capability of squeezing precipitation from clouds as they loft up and over the peaks. Have you noticed that the west side of the Cascades is lush, green rainforest, and the east side is high, dry desert? This influence of mountains on precipitation is called the “orographic effect”, aka the “rain shadow” (https://www.e-education.psu.edu/earth111/node/751). Imagine clouds as sponges, heavy with water. As these clouds collide with mountain ranges, they are forced up, higher into the troposphere, where it is colder. Cold air holds less moisture than warm air. Thus, in order to loft up and over the obstacle, the clouds precipitate, like a sponge being wrung out. In our unique topographical locale, we are on the wetter side of the Cascade Mountain range, an invaluable, life-giving gift in the form of lakes, streams, and rivers.
If you’ve been on the fence regarding rain catchment, this is the time to install it. It will serve you well in the future and provide a cushion in times of water scarcity.
Be well, dear readers.
