Icicles and Watersheds Part 2: How much water flows off the top of two houses

Posted on 01/14/2008 by peggy

What about the total amount of water coming off the roof? Suppose it is raining, so insulation doesn’t make any difference. Again, about twice as much water would flow off a given spot along the eaves for our house. But the total amount of water flowing off one side of the house is determined by the total area of the roof upstream.

Consider the one-meter section of our house in Figure 2. Let’s estimate how much water would flow off a meter length on the east side for a rainfall of 1 centimeter per hour. The roof measures 10 meters from the top to the eaves.

In an hour, the volume of water falling on the roof would be 1 centimeter per hour or 0.01 meters per hour × 1 meter × 10 m, or 0.1 cubic meter of water per hour. Since water weighs 1 gram per cubic centimeter and there are 100 x 100 x 100 x 0.1 cubic centimeters in 0.1 cubic meter, about 100 kilograms of water fall on this one-meter section of the roof per hour. The same amount flows over a meter section of the eaves to the ground in about an hour (assuming the roof drains as fast as it rains!)

But we need to make a minor correction for the fact that the roof is not exactly horizontal (i.e., it’s covering less ground).

If the angle of the roof to the ground is 20 degrees, we need to multiply the 100 kilograms of water per hour per 1 meter by 0.94, making the total rainfall 94 kilograms.

If the roof measures 10 meters along the eaves and top of the roof (Figure 3), the total amount of water flowing off the roof on the east side is 10 times that amount, or 940 kilograms allowing for the angle of the roof.

What about the roof of the imaginary house in Figure 3, which measures 5 meters from the top of the roof to the eaves? Half as much water or 47 kilograms falls on a one-meter slide of this house (Figure 2) each hour, so half as much water will flow off the eaves per meter each hour compared to our house, which measures 10 meters from roof to eaves. We assume the roof’s angle to the ground is the same as our house.

The total amount of water flowing off the roof of the imaginary house each hour would then be:

47 kilograms per 1 meter along the eaves times 20 meters, or 940 kilograms flowing off the east side of the roof each hour. This is of course the same amount of water flowing off our house.

Did you notice that if you just know that the area and angle of the roof of the imaginary house are the same as the roof as our house, means that the total amount of rain falling on both houses is the same, and therefore the same amount of water flowing off the two roofs is the same?

We could call these roofs “roof watersheds” or “roofsheds” because they shed water – in the form of icicles in the first example, or in the form of liquid in the second.

figure3.gif

Figure 3. “Roofsheds” for our house and the imaginary house, viewed from above. Both roofs, having the same area (100 square meters) and angle to the ground (20 degrees), will shed the same amount of water on the east side, where the eaves are.

Posted in Backyard Science, Hydrology, Watersheds | 2 Comments

Surface Temperature Field Campaign – Summary

Posted on 01/10/2008 by peggy

Below you will find Dr. Kevin Czajkowski’s summary of the participation in his surface temperature field campaign. We at GLOBE join Kevin is his sincere thanks for your help!

8 January 2008

Thank you for your participation in the 2007 GLOBE Surface Temperature Field Campaign.

The surface temperature field campaign is completely over. I think that every student and teacher who was going to enter observations has done so. We had over 1100 total observations. That is wonderful. As you know, each complete observation represents 9 surface temperature observations, 9 snow depth, cloud cover and cloud type, condensation trail cover and type, surface wetness, and cover type for a total of 24 observations per complete surface temperature observation. That means that there were over 26,000 individual student observations for the campaign. That is impressive!

A total of 40 schools participated from the United States, Estonia, Thailand, Poland and from the following states in the United States Ohio, Pennsylvania, West Virginia, Michigan, Iowa, Alaska, Illinois, Kansas and Colorado. The school with the largest number of observations was Roswell Kent Middle School in Akron, Ohio with 75 observations. A close second was Kilingi-Nomme Gymnasium in Parnumaa, Estonia (72 observations), Gimnazium in Toszek, Toszek, Poland (69 observations), Waynesboro Senior High School, Waynesboro, Pennsylvania (69 observations), Dalton High School, Dalton, Ohio (67 observations) and Rockhill Elementary School, Alliance, Ohio with 61 observations. Even if your school only entered one observation, every observation is important and your contribution to the project is greatly appreciated.

tsschools2.jpg

Figure 1. Map of schools participating in the surface temperature field campaign.

I wanted to give you a little update on how things were going around my house. In late December, my frost tube showed that the ground was frozen to about 10 cm in depth. But, then, on New Year’s Eve, temperatures warmed up and melted the frost. I was actually with my family about two hours drive north in Michigan visiting family when it snowed 38 cm (15 inches) New Year’s Eve and New Year’s Day morning. I tried to drive my van out of the side road to a main road. Unfortunately, the snow was too deep and the van got stuck several times. I used a shovel to dig the van out and finally gave up and parked in a neighbor’s driveway. This was the first time in my life I had been stuck in the snow. Having grown up near Buffalo, NY where there is lots of snow in the winter, I prided myself on being a good winter driver. Of course, it wasn’t poor driving skills that got us stuck. It was the fact that the snow was so deep. We finally made it out and got to our house near Toledo, Ohio later that night.

That storm produced only rain in Toledo, Ohio. Then, 7 cm (3 inches) of snow fell on New Year’s Day at our house near Toledo. After that, temperatures dropped to –13º C (8º F) two nights in a row. Interestingly, due to the 7 cm of snow on the ground, the frost tube showed no ice below the ground surface. The snow had insulated the ground from the cold.

Then, there were extremely warm temperatures January 6-9, 2008 in Toledo, Ohio and much of the eastern United States. On Monday, Toledo reached a record high of 19º C (66º F). The old record temperature was 16º C (61º F) that was set in 1907. All of the snow and ice has melted around here. But, the weather forecast models show that temperatures are going to drop again below freezing.

Schools involved in the surface temperature field campaign to date:

Roswell Kent Middle School, Akron, Ohio, USA – 75 observations
Rockhill Elementary School, Alliance, Ohio, USA – 61 observations
Dalton High School, Dalton, Ohio, USA – 67 observations
Chartiers-Houston Jr./Sr. High School, Houston, Pennsylvania, USA – 12 observations
Cloverleaf High School, Lodi, Ohio, USA – 38 observations
The Morton Arboretum Youth Education Dept., Lisle, Illinois, USA – 16 observations
Mill Creek Middle School, Comstock Park, Michigan, USA – 14 observations
Kilingi-Nomme Gymnasium, Parnumaa, Estonia – 72 observations
Polaris Career Center, Middleburg Heights, Ohio, USA – 1 observation
National Presbyterian School, Washington, DC, USA – 9 observations
White Cloud Public, White Cloud, Michigan, USA – 44 observations
Blue Valley High School, Stilwell, Kansas, USA – 5 observations
Perkins Middle School, Akron, Ohio, USA – 19 observations
Steeple Run School, Naperville, Illinois, USA – 4 observations
Kittrell Elementary School, Waterloo, Iowa, USA – 4 observations
Tallinn Science Secondary School, Tallinn, Estonia – 68 observations
Oak Glan High School, New Cumberland, West Virginia, USA – 19 observations
Lorain Community College Early College High School, Elyria, Ohio, USA – 52 observations
Ingomar Middle School, Pittsburgh, Pennsylvania, USA – 13 observations
Moosewood Farm Home School, Fairbanks, Alaska, USA – 21 observations
Roxboro Middle School, Cleveland Heights, Ohio, USA – 16 observations
Bowling Green State University, Bowling Green, Ohio, USA – 50 observations
Walailak University, Nakhon Si Thammarat, Thailand – 4 observations
Massillon Middle School, Massillon, Ohio, USA – 10 observations
Ida Elementary School, Ida, Michigan, USA – 14 observations
Whitehall High School, Whitehall, Michigan, USA – 56 observations
Taaksi Basic School, EE2914, Viljandimaa, Estonia – 16 observations
Midview West Elementary School, Grafton, Ohio, USA – 12 observations
Birchwood School, Cleveland, Ohio, USA – 47 observations
Gimnazium in Toszek, Toszek, Poland – 69 observations
Gimnazjum No 7 Jana III Sobieskiego, Poland – 35 observations
Waynesboro Senior High School, Waynesboro, Pennsylvania, USA – 68 observations
Eastwood Middle School, Pemberville, Ohio, USA – 16 observations
Orange Elementary School, Waterloo, Iowa, USA – 8 observations
Estes Park High School, Estes Park, Colorado, USA – 4 observations
Hudsonville High School, Hudsonville, Michigan, USA – 37 observations
Highlands Elementary School, Naperville, Illinois, USA – 5 observations
University of Toledo, Toledo, Ohio, USA – 5 observations
Main Street School, Norwalk, Ohio, USA – 43 observations
Martin Luther King Jr/Sr High School, Cleveland, Ohio, USA – 17 observations

Dr. C

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Icicles and Watersheds: Part 1

Posted on 01/09/2008 by peggy

Why are the icicles so long on our house?

On a recent walk just a day or two after our first snow, my husband and I noticed that we had the longest icicles in the neighborhood. Some houses built the same time as our house had icicles, but they were shorter. One new house had almost no icicles.

But what was the most fun, was our own house. The picture below shows our “champion” icicles.

Sketch of icicles on the east side of our house

Figure 1. Sketch of icicles on the east side of our house. The windows to the right of the icicles are about 1 meter high. The part to the right is the front part of the house; the part to the left is the back part of the house.

Notice that the icicles only cover the middle third of the side of the house. To the right and to the left, there are no icicles. Were we to walk on the roof, we would probably find the snow melted in the middle third of the roof, but not on the sides.

Why? Our house was built in stages. The front two-thirds were built were built in 1950. There was little insulation in the roof. A few months before I made this sketch, we tore out the old ceiling in the room in the front of the house and found that the insulation from 1950 was in poor condition, just like the insulation in the middle of house. The new insulation was much better. The picture confirms that the new insulation was working. No icicles implies no water from melting snow. This means that little heat was escaping through the roof, so there was little or no snowmelt on the roof.

Similarly, the back part of the house was built in 1979. When that part of the house was built, we made sure we had good thick insulation in the roof. There are no icicles on the new part of the house. Again – the insulation must be working.

Using the data from our house, can we explain why our house had the longest icicles? I’m guessing that the new house in our neighborhood that had almost no icicles had good insulation – just like the newer parts of our house and the room we just insulated. We could that the snow on the roof of the new house was fairly deep – there was little melting.

What about the older houses with shorter icicles? Let’s imagine an older house with about the same insulation as the old parts of our house (Figure 2). If this is true, the snow would melt at about the same rate (I am assuming that the roof was exposed to the same amount of sunlight per unit area). Why then would the icicles be shorter on the other (imaginary) house?

If you believe my assumptions, the answer is that the area of the roof “draining” toward the eaves (where the icicles grow) was smaller. Say the distance from the top to the icicles on our imaginary house is 5 meters, and the distance on our house is 10 meters. As the melted snow moves down from the top of the roof to the eaves, twice as much water reaches a given length along the eaves for the 10-meter roof (ours) compared to the five-meter roof. It follows that the icicles on our house would contain twice as much water and be longer than on the other house. The icicles may be not twice as long, because the icicles we had might be wider as well as longer.

View of a slice of our house (top)

Figure 2. View of a one-meter slice of our house (top) and an imaginary neighborhood house (bottom). More water is available to flow over the eaves for our house. We are looking at the two houses from the north.

So the amount of water in the icicles is determined by the amount of snow upstream of (or straight up the roof from) the eaves.

Posted in Backyard Science, Hydrology, Watersheds | Leave a comment

Surface Temperature Field Campaign – Day 25

Posted on 12/21/2007 by peggy

21 December 2007

It is the last official day of the 2007 surface temperature field campaign. Although we will not know for several weeks the total number of schools that have participated and the total number of observations taken, it was a great success. It has been a lot of fun watching the observations come in and to post blogs a couple times a week. Of course, if you want to keep taking measurements into the new year, please do. I know of a couple schools that are going to do that.

Here is an update on the snow situation. In North America, the snow has been melting back a bit in the center and eastern parts of the United States (Figure 1). You will also notice that there is a little more snow coverage in Eastern Europe. That is a common occurrence in the winter for cold air to move back a forth from the Eastern to the Western Hemisphere. When the cold weather was affecting the United States, Eastern Europe was warm. Now, it has flipped a little.

Surface Temp Campaign image

Figure 1. Snow extent in the Northern Hemisphere from 20 December 2007.

In the Western Hemisphere, there has been a fundamental change in the atmospheric flow. When it was cold and there were several major snow storms in the United States, the flow was out of Canada which is a source of cold air in the winter (Figure 2). This type of flow is called meridional. The upper level flow is at around 5500 meters above sea level. It steers the weather systems. This week, the pattern has changed and the upper level flow is sending weather systems from the Pacific Ocean into the west coast of the United States. Then the systems track across the United States. This type of flow is called zonal. This is bringing in warmer and moister air and is one of the reasons that the temperatures across much of the central part of the United States have gone above freezing.

This shift in weather patterns is evident in the surface temperature observations that were recorded. On 17 December 2007, Rockhill Elementary School in Alliance, Ohio recorded a surface temperature 3.0° C where there was no snow in the parking lot to –5.4° C on their grassy field where there was 78 mm of snow. On 20 December 2007, the students at Rockhill Elementary School measured 4.5° C on the parking lot and 0.4° C on the snow covered field with 80 mm of snow. As you can see, the temperature of the snow pack warmed up to right around freezing.

It is the last official day of the 2007 surface temperature field campaign. Although we will not know for several weeks the total number of schools that have participated and the total number of observations taken, it was a great success. It has been a lot of fun watching the observations come in and to post blogs a couple times a week. Of course, if you want to keep taking measurements into the new year, please do. I know of a couple schools that are going to do that.

Here is an update on the snow situation. In North America, the snow has been melting back a bit in the center and eastern parts of the United States (Figure 1). You will also notice that there is a little more snow coverage in Eastern Europe. That is a common occurrence in the winter for cold air to move back a forth from the Eastern to the Western Hemisphere. When the cold weather was affecting the United States, Eastern Europe was warm. Now, it has flipped a little.

Surface Temp Campaign image

Figure 2. Upper level flow on 15 December 2007 (top) and 21 December 2007 (bottom).

In general, all of the measurements in the United States showed a warming from 17 December to 20 December. The warmest temperature for this past week was 12.4° C and was measured 20 December 2007 at Waynesboro High School in Waynesboro, Pennsylvania on their dry parking lot while the coldest temperature was measured at Eastwood Middle School, Pemberville, Ohio of –11.0° C where there was 83 mm of snow. If the students at Moosewood Farm Home School in Fairbanks, Alaska had reported this week, they would have reported the coldest temperature by far. The air temperature hovered between –35° C and –40° C. But, they did not report any temperatures. It was probably too cold for the students to go outside.

Below is a pair of figures that was recently published about the Arctic ice cover on the NASA Earth Observatory website along with an article (Figure 3). The 1978-2002 median value is shown as the yellow line (Median is the middle value of a bunch of numbers. For example, if you are one of five children, of ages 1, 3, 7, 11, and 13, the median age of the children in your family is 7 years). You can see that the ice melted in the Arctic Ocean to record low levels in September this year and recovered quite a bit by November. But, the ice extent is still far below the 1978-2002 median level.

Surface Temp Campaign image

Figure 3. Ice extent compared to the 1979-2002 median extent for November (top) and September (bottom) 2007. Maps of ice extent from NASA Earth Observatory.

Schools involved in the surface temperature field campaign to date:

Roswell Kent Middle School, Akron, Ohio, USA
Rockhill Elementary School, Alliance, Ohio, USA
Dalton High School, Dalton, Ohio, USA
Chartiers-Houston Jr./Sr. High School, Houston, Pennsylvania, USA
Cloverleaf High School, Lodi, Ohio, USA
The Morton Arboretum Youth Education Dept., Lisle, Illinois, USA
Mill Creek Middle School, Comstock Park, Michigan, USA
Kilingi-Nomme Gymnasium, Parnumaa, Estonia
Polaris Career Center, Middleburg Heights, Ohio, USA
National Presbyterian School, Washington, DC, USA
White Cloud Public, White Cloud, Michigan, USA
Blue Valley High School, Stilwell, Kansas, USA
Perkins Middle School, Akron, Ohio, USA
Steeple Run School, Naperville, Illinois, USA
Kittrell Elementary School, Waterloo, Iowa, USA
Lorain Community College Early College High School, Elyria, Ohio, USA
Ingomar Middle School, Pittsburgh, Pennsylvania, USA
Moosewood Farm Home School, Fairbanks, Alaska, USA
Roxboro Middle School, Cleveland Heights, Ohio, USA
Bowling Green State University, Bowling Green, Ohio, USA
Walailak University, Nakhon Si Thammarat, Thailand
Massillon Middle School, Massillon, Ohio, USA
Ida Elementary School, Ida, Michigan, USA
Whitehall High School, Whitehall, Michigan, USA
Taaksi Basic School, EE2914, Viljandimaa, Estonia
Birchwood School, Cleveland, Ohio, USA
Gimnazium in Toszek, Toszek, Poland
Waynesboro Senior High School, Waynesboro, Pennsylvania, USA
Eastwood Middle School, Pemberville, Ohio, USA
Orange Elementary School, Waterloo, Iowa, USA
Estes Park High School, Estes Park, Colorado, USA
Hudsonville High School, Hudsonville, Michigan, USA
University of Toledo, Toledo, Ohio, USA
Main Street School, Norwalk, Ohio, USA

Dr. C

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Surface Temperature Field Campaign – Day 21

Posted on 12/18/2007 by peggy

17 December 2007

The storm that moved through the center of the United States lived up to its billing. There was heavy snow, strong winds, heavy rain, tornadoes, freezing rain and sleet. In Toledo, Ohio we had about 5 cm of snow and then freezing rain and sleet on top of that. One of my friends could not get into his car because the ice froze over the car. I broke two ice scrapers trying to get the ice off of my car. After the ice, I think we had about 20 cm (8 inches) of snow at my house but then the wind blew the snow into drifts so it was hard to tell how deep the snow is. I was driving home from the store last night when I saw a car slide off the road into the deep snow in the ditch. I carry a shovel with me in my car in the winter so I was able to help him. A couple of young men, maybe seniors in high school, stopped and helped me push the car out. It felt good to help someone.

Figure 1 shows the snow and ice cover extent in the Northern Hemisphere. Compare that to the mean December snow water equivalent in Figure 2. The snow water equivalent is the depth of water that the snow will melt down to. For the storm over the weekend, the ratio of snow to water was probably on the order of 10:1 or 8:1. That means that for every 10 cm of snow it will melt to 1 cm of water. So, for the 20 cm of snow that we received in Toledo, Ohio there should be about 2 cm of water when the snow melts. Although the snow water equivalent and the snow extent are two different observations, the area of snow water equivalent can be used as an indication of snow extent. When you compare Figure 1 with Figure 2, how does the extent of snow cover today compare to the snow extent as indicated by the mean December snow water equivalent map in Figure 2?

Current Northern Hemisphere Snow Extent

Surface Temp Campaign image

Figure 1. Current (17 Dec. 2007) snow extent in the Northern Hemisphere.

Surface Temp Campaign image

Figure 2. Mean snow water equivalent (SWE) for December. Source: National Snow and Ice Data Center.

How are the maps of snow extent created? One of the sources of data is from satellite imagery. Figure 3 is a satellite image from a geostationary satellite called GOES. Snow covers most of the image including the states of Iowa, Illinois, Wisconsin, Missouri and Indiana. How can you tell where the snow is in this image? Do you see clouds in this image as well?

Surface Temp Campaign image

Figure 3. GOES (Geostationary) satellite image from 17 December 2007, 18:15 Universal Time.

As of this morning, we are up to 556 observations from 32 schools. I was able to add the observations from the University of Toledo.

Roswell Kent Middle School, Akron, Ohio, USA
Rockhill Elementary School, Alliance, Ohio, USA
Dalton High School, Dalton, Ohio, USA
Chartiers-Houston Jr./Sr. High School, Houston, Pennsylvania, USA
Cloverleaf High School, Lodi, Ohio, USA
The Morton Arboretum Youth Education Dept., Lisle, Illinois, USA
Mill Creek Middle School, Comstock Park, Michigan, USA
Kilingi-Nomme Gymnasium, Parnumaa, Estonia
Polaris Career Center, Middleburg Heights, Ohio, USA
National Presbyterian School, Washington, DC, USA
White Cloud Public, White Cloud, Michigan, USA
Blue Valley High School, Stilwell, Kansas, USA
Perkins Middle School, Akron, Ohio, USA
Steeple Run School, Naperville, Illinois, USA
Kittrell Elementary School, Waterloo, Iowa, USA
Lorain Community College Early College High School, Elyria, Ohio, USA
Ingomar Middle School, Pittsburgh, Pennsylvania, USA
Moosewood Farm Home School, Fairbanks, Alaska, USA
Roxboro Middle School, Cleveland Heights, Ohio, USA
Bowling Green State University, Bowling Green, Ohio, USA
Ida Elementary School, Ida, Michigan, USA
Whitehall High School, Whitehall, Michigan, USA
Taaksi Basic School, EE2914, Viljandimaa, Estonia
Birchwood School, Cleveland, Ohio, USA
Gimnazium in Toszek, Toszek, Poland
Waynesboro Senior High School, Waynesboro, Pennsylvania, USA
Eastwood Middle School, Pemberville, Ohio, USA
Orange Elementary School, Waterloo, Iowa, USA
Estes Park High School, Estes Park, Colorado, USA
Hudsonville High School, Hudsonville, Michigan, USA
University of Toledo, Toledo, Ohio, USA
Main Street School, Norwalk, Ohio, USA

Take care,

Dr. C

Posted in Atmosphere, Climate, Field Campaigns, GLOBE Protocols | 2 Comments