Melting Snow and Rising Rivers

This map of snow water equivalent shows the amount of water contained in the snowpack–essentially, the depth of water released if the entire snowpack was melted instantaneously.

snow water equivalent

The map comes from the National Operational Hydrologic Remote Sensing Center, which also provides information about snow depth and other snow-related variables.

Snow water equivalent provides useful information for water supply (and things like soil moisture for agriculture and other land uses) as well as for flood forecasting. It’s an important number to watch during the spring months, particularly along the Nebraska-Iowa and North Dakota/South Dakota-Minnesota borders.

In these areas, the snow is melting (at last!). But there’s been a lot of snow over much of the upper midwest this winter, and it’s melting quickly. That can mean lots of surface runoff, especially in areas of deep frost, which can cause localized flooding. Eventually, this runoff makes it into the rivers, where high water levels and potential ice jamming can lead to rivers spilling over banks and levees, resulting in property damage, and in some cases, potential loss of life.

The National Weather Service has a flood safety website to help you learn about the flood danger in your particular area and review safety tips. Understanding the danger as well as the actions you can take will help you be better prepared if or when flooding does occur.

Today’s Instructional Lesson: Seiches

A seiche is an oscillation associated with a standing wave that occurs in an enclosed or partially enclosed body of water, resulting from seismic activity or meteorological effects.

graphic of wind-driven seiche
Click to view this University of Wisconsin Sea Grant Institute animation of a wind-driven seiche. Seiches are not uncommon phenomena on the Great Lakes and adjacent bays and rivers.

Seiches have been observed on lakes, reservoirs, ponds, rivers, and even swimming pools. You can create your own seiche in your bathtub, just by rocking back and forth. At the right frequency, you can set up an oscillation–essentially a small-scale seiche–that allows the waves to grow until they overflow the bath.

A similar “sloshing”–in this case a seismic seiche–was observed on Saturday, February 27, on Lake Pontchartrain in Louisiana, caused by an earthquake 4,700 miles away off the coast of Maule, Chile. Lake Pontchartrain sits on the Mississippi Delta, which contains a deep layer of surface sediments. Seismic waves can resonate through this sediment more easily than through more firm surface types, making the Gulf region particularly sensitive to earthquake-induced seiches. The seiche affecting Lake Pontchartrain occurred 11 minutes after the 8.8 magnitude Chilean earthquake and resulted in water levels about 6 inches higher than the predicted tides.

Want the video version? Derek Kevra at WWLTV has a great explanation of the quake and resulting seiche here. And if you want to learn more about seiches in history, check out this page from the USGS Earthquake Hazards program.

Earth Science Resources – A Sampler

Spinning up new projects at work, which means learning about new topics, which means fun! Every night this week I’ve gotten to bring home a geology textbook, and let me tell you, I’m so enamored with science books. Especially ones with lots of cool pictures. And this one has many! The book is Physical Geology (11th ed.), by Plummer, Carlson, and McGeary. It seems to be intended for an introductory survey course at the college level, but motivated high school students could certainly glean a lot, and it’s got the photos and diagrams to draw in non-student science geeks also. Or maybe I shouldn’t generalize that way—but it at least drew in this non-student science geek.

Having been through lots and lots of science textbooks over the course of my academic career and in the time since, well, the books I tend to pick up the most often really are those introductory type texts. Maybe it has to do with the nature of working in education and exploring ways to teach a wide variety of topics, not necessarily at an expert level. Maybe it’s all those pretty pictures. At any rate, I thought I’d share a few of my favorite Earth science resources, and see if you wish to add any as well. Your recommendations are always welcome!

General Earth Science:
Dr. Art’s Guide to Planet Earth (Sussman). It says right on the cover that this book is for Earthling ages 12 to 120. That covers, well, lots of the population. Dr. Art takes the Earth system approach, looking at how the different components are interconnected. It’s effective. It’s basic information that a science literate public should understand. The font size is large and it’s divided into short topic sections so that even a non-science geek could get through it. I know it says 12 to 120, but maybe it should be bedtime reading for kids. Both you and they might take away a new understanding and appreciation of our planet.

Earth Science (Spaulding and Namowitz). This one is a high school textbook, but has a surprising amount of gems and nuggets of information on a full range of topics. I find it very entertaining and sometimes even enlightening reading, but we have already established that I am geek.

Turn Left at Orion (Consolmago and Davis, 3rd ed). No, it’s not a textbook. But having taught night-sky programs for a lot of years, this one is a book I’d definitely replace if my dog ate it. [Actually, he did eat the binding, but the talented folks at Kinkos were able to remedy that for me.] I like it because it has the essential observing information (what to see, and where/how to find it) but also adds some science bits so if you’re trying to explain to someone what that cluster represents, or the ages of the stars in it, it’s all in that one place. Handy. Essential.

Physical Geology (Plummer, Carlson, McGeary). Yes, already said, love the photos. And the really clear explanations with real-life scenarios. Maybe it’s because geology—like other Earth sciences—is just…relevant. Earth, it’s where we live. All that part and why I bother trying to teach, write, etc. about it. This book gave me a sense that the authors really shared that philosophy. Did I mention the awesome photos?

Essentials of Meteorology (Ahrens). Alright, this one is actually on the bookshelf at work, so I can’t look up specific details right now, but it’s the introductory resource I point people to when asked. It’s another undergraduate introductory survey course text and explains the essentials (as its name indicates) without the math. And that can be refreshing for people who want to try to understand the concepts but don’t need all the equations for fluids and heat exchange etc. etc.

The Stories Clouds Tell (LeMone). I’ve already linked to a couple of Dr. LeMone’s backyard science articles on this blog, but this book actually dates back to a talk she gave in the late 1980s. It was first published by the American Meteorological Society and recently updated and re-released and it is beautiful. Like watching clouds? Want to know what they mean in terms of weather? This book has that information, plus very clear descriptions and diagrams of how clouds form, plus some amazing photos. If there’s ever to be a multimedia tutorial produced from this book, I want to be the one to do it, yes indeed.

Web resources:
Of course this category should be filled in, but I fear that would be an endless task. Check out the Digital Library for Earth System Education (DLESE) and the National Science Digital Library (NSDL). You can search for resources by topic and grade level. A visit to the Windows to the Universe site could show you some cool stuff, and will again provide information customizable to a specific grade level. There are oodles more: Google can help you get there, and I’ll post resources here now and again as I come across them.

In the meantime, happy reading and exploring!

Sunrise, Sunset, and Moving Swiftly Through the Days

A new month in a new year and it’s gone by far too quickly. I thought I’d close out the lengthening days of January by sharing some interesting sources of information. The pick for today is the NOAA Sunrise/Sunset Calculator, developed by some talented former colleagues. It is a resource used by people in all walks of life—from scientists and sky watchers to film makers and event planners—and a great way to explore what’s going on in terms of the number of hours of daylight received in a day.

According to the calculator, at 40 degrees latitude in the approximate middle of the mountain time zone, the apparent sunrise on January 31 is 7:09 a.m. and apparent sunset is 5:19 p.m. What’s “apparent” sunrise, you ask? Let’s use this graphic from the solar calculator Help Guide (really guys, great work putting this resource together!) to illustrate:

schematic showing reflection of visible light by atmosphere
Gases in Earth\’s atmosphere refract visible light from the Sun.

Earth’s atmosphere refracts (or bends) incoming light from the Sun. Because of that refraction, we see the sun “rise” shortly before it actually crosses the horizon. Likewise, we see the setting sun for a short time after the sun has actually “sunk” below the horizon at the end of a day. (If this part sounds like desperation from a person eager for any at all additional daylight, well, consider that mid-latitude winters sometimes just seem…long.) Apparent sunrise and sunset times are different than actual sunrise and sunset times, adding just that little bit of additional time to the number of hours of daylight in a day.

The nice thing about the end of January sunrise and sunset times is how they differ from the dark, dark days of December. Did we talk about the solstice on December 21? On that day, the apparent sunrise was at 7:18 a.m. but the sun was gone a full 40 minutes earlier, at 4:39 p.m. For those of us desperate enough to grab those few minutes based on apparent sunrise and sunset, 40 minutes seems quite a cause for celebration, or at least acknowledgment. Go ahead, play with sunrise and sunset times for your location, and check out what happens at the summer solstice too.