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

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

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?

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.

Take care,

Dr. C

13 December 2007

I’ll have to say that I haven’t posted a message on the blog lately partly because I was busy with finals at the University of Toledo and my trip to San Francisco for the American Geophysical Union meeting. But, I also have had bloggers block. I didn’t know what to write about. Well, now I have a lot of things that I want to write about. Some of it will have to wait until next week.

All of the snow has melted in Toledo, Ohio. The temperatures over the last couple of days have gotten above freezing. You are all probably aware of the ice storm that hit the center of the country. That system caused a little bit of snow yesterday in Toledo but the forecast of 5-10 cm (2-4 inches) of snow did not pan out. But, the system caused a good amount of snow in southern New York state, Pennsylvania and even 25 cm (10 inches) in Boston, Massachusetts. Among the schools that have entered data for the surface temperature field campaign, White Cloud School in White Cloud, Michigan has reported 27 cm (11 inches) of snow on the ground.

It looks like another major winter storm is going to move out of the mountains over the weekend, across the country, to the east coast of the U.S. (see Figure 1 below). The map shows the low pressure system will be over Tennessee Saturday evening and will be spreading snow from Oklahoma to Pennsylvania. It looks like the drought stricken parts of United States will be getting some much needed rain. This storm should be a good one with strong winds. The forecast for Toledo, Ohio is 10-15 cm (4-6 inches) of snow. Locations in the southern part of Ohio should get more snow as should the eastern United States. I bet all of the students will be wishing the storm had hit during the week….

It looks like the snow will stick around as well. After the storm goes by, much colder conditions are expected. The temperature should remain below freezing for several days at the minimum. I hope I can get out my cross country skis. Also, I’ll try to go sledding with my kids.

Figure 1. Forecast map for 0Z Sunday, 16 Dec. 2007 (which is Saturday night in North America).

Surface Temperature Satellite Data

Timothy Ault, a Research Scientist at the University of Toledo, helped me by plotting up the students’ surface temperature observations. He took the student observations from the GLOBE Web site and plotted them in a Geographic Information System (GIS) to map the values overlaid on MODIS data from the Aqua satellite image. In the image below, you will see how much of Michigan, central Pennsylvania, and western New York are covered with clouds. [I apologize to the schools from Alaska, Iowa, Illinois, Estonia and Poland that are not on this map. I wanted to show what could be done with the data so I picked an area that covered the most schools possible.] The MODIS image was acquired from the rapid response Web site.

As you can see from the student measurements, the surface temperatures in Michigan under the cloud cover are much cooler than the surface temperatures in northeast Ohio and southwest Pennsylvania. The areas without cloud cover tend to have much warmer temperatures. When I was at AGU, Dr. Dorothy Hall from NASA Goddard Space Flight Center mentioned that scientists do not know the surface temperature under clouds because the clouds block the signal that the satellite can observe. This is a good example of how student observations are adding to our scientific knowledge. The students can measure something that the satellites can’t.

The students’ observations of cloud cover are denoted by the numbers to the left or above the circle. These are the nominal cloud cover percentages associated with the categories of the GLOBE observations. Clear – 5%, Isolated – 17.5%, Scattered – 37.5%, Broken – 70% and Overcast – 95%. You might be able to see that the student cloud cover observations do not seem to match the MODIS cloud observations especially in northern Ohio and southwest Pennsylvania. Why do you think that is? If you notice, Tim did not put the time the satellite went over and the time of the student observations on the map. Would the time of observation of clouds be important? And could that be the reason that there are differences?

In the MODIS image, you can see the urban heat island effect. I have an arrow pointing out Columbus, Ohio which shows up clearly as warmer than the rural areas surrounding it. Dayton, Ohio and Pittsburgh, Pennsylvania also show up warmer as well.

Figure 2. Student observations of surface temperature mapped onto a surface temperature MODIS image for 27 November 2007. The surface temperature measured by the students is in the circles and color coded according to the legend on the left. The number above or to the left of the circle is the nominal cloud cover percentage.

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 last night. It is nice to see so many observations coming in. Not that this is a competition, but the students from some schools are putting a lot of effort into the field campaign. I’m very impressed. I put the number of observations next to the schools with more than 20 observations.

Take care,

Dr. C

11 December 2007

Today I am in San Francisco, California at the Annual American Geophysical Union (AGU) conference. I heard today that there are over 15,000 scientists here. I bet you did not know that scientists are always learning. As you can see in Figure 1, the areas that I flew over were snow covered for the most part, that is if there were no clouds which was very common.

Figure 1. My flight path over the United States from Detroit, Michigan to San Francisco, California.

I took a bunch of pictures as I was flying from Detroit, Michigan to San Francisco, California.

Figure 2. Picture I took from my airplane of a snow covered mountainous area.

The view was great. Isn’t it amazing the quality of pictures that can be taken from an airplane with a regular digital camera? I really enjoy having a window seat when I fly.

A conference like this one is a way for scientists to share information. There are two ways that we present our work to other scientists. One is through an oral presentation, i.e. giving a talk. This is similar to what your teacher might do presenting information to you in class. The other way is through poster presentations. See figure 3 below. In this picture, there are hundreds of posters being presented at the same time. Poster presentations are very similar to science fair projects that students do.

Figure 3. Poster session at the AGU meeting December 11, 2007.

Attending the AGU meeting is also a chance for me to see my scientist friends again.

I learned some interesting things about remote sensing of snow today. Scientists at NASA Marshall Space Flight Center are using a satellite sensor called AMSR-E (Advanced Microwave Scanning Radiometer EOS). It is a sensor that uses microwave wavelengths to estimate the amount of water, called snow water equivalent, in the snow at specific locations. Interestingly, one scientist said that the ability to accurately retrieve snow water equivalent from AMSR-E is dependent on the surface temperature. This may be a type of project that could use student observations from the surface temperature field campaign.

Thirty schools and counting have participated thus far in the surface temperature field campaign. Thank you for all of your hard work.

Take care,

Dr. C

6 December 2007

So far there have been 291 observations recorded from 27 schools in the surface temperature field campaign. I have had undergraduate students participating, but we haven’t entered our observations yet. So, there will be at least one more school’s data showing up on the GLOBE Web site.

You can see below a list of the schools that have participated and entered data thus far. I would like to highlight some schools that have been doing an exemplary job:

• The Lorain County Community Early College High School in Elyria, Ohio has entered the most observations so far with 37. Nice job Rose O’Toole-Hamman and students!
• In a close second are:
  • Birchwood School in Cleveland, Ohio with 32 (thanks Linda Brown and students); and
  • Dalton High School in Dalton, Ohio (thanks Jerry Wilmer and students!) with 30.

Data collection accounts for about 80% of time spent on my research project. Without data, there is no way to do the research. Often I am faced with having to revise my research projects because of lack of data. It seems like you never have the right locations or right times to do a thorough study.

Most of the schools are now reporting snow with their surface temperature observations. As you can see in the maps below, there is a lot more snow on the 8 December 2007 image than on the 5 December 2007 image. This was due to a series of Alberta Clippers.

Figure 1. Snow cover for the lower 48 United States for Wednesday, 5 Dec. 2007 (top) and Thursday, 8 Dec. 2007 (bottom). Source: National Operational Hydrologic Remote Sensing Center.

Note the increase in snow cover in Michigan, Ohio, West Virginia, Virginia, Maryland and New Jersey. This was due to the Alberta Clipper that tracked from Alberta down into the United States and out into the Atlantic Ocean not too far from Washington, DC.

There are some really good examples of places where there is snow on the grass but not on the parking lot. For instance, Whitehall High School in Whitehall, Michigan reported a surface temperature of 0° C on a grassy area with 14 cm of snow. Interestingly, they reported 0° C for a bare parking lot. I am very interested to find out if this is a common occurrence to not see an effect due to the snow.

This year we have much more snow than during the field campaign last year. In fact, it was so warm last year during the surface temperature field campaign that the broccoli in my garden was still growing. I pick my last broccoli on January 1, 2007 last winter. This winter the broccoli was dead several weeks ago because of the cold. So you may be asking, “Why was it so warm in the Great Lakes region last December and so cold this December?” My understanding is that last December there was an El Nino in the Pacific Ocean that lead to warm conditions in the Great Lakes region. This December there is a La Nina in the Pacific Ocean that is leading to the cold conditions in the Great Lakes. I won’t go into the details of this. That can be the subject of another blog entry.

The number of schools participating has stayed nearly the same over the last couple of days. There are many more schools involved, but they have not been entering their observations yet on the GLOBE Web site.

I think I’ll get my cross country skis out.

Dr. C

5 December 2007

The surface temperature field campaign continues to go well. Yesterday, 38 observations were posted by students. I believe this number will increase as students and teachers get their observations into the GLOBE Web site.

Almost all of the observations are below the freezing mark today. The coldest surface temperature observations came from the Moosewood Farm Home School (teacher Deb Bennett) in Fairbanks, Alaska. The lowest value of surface temperature they measured so far was –25.9° C (-14.9° F).

The weather in the United States has remained wintry and significant snowfall has occurred in the Great Lakes region to the east coast. I measured around 5 cm of snow when it stopped snowing here in Toledo, Ohio today. I know that other places measured a lot more snow. Greg Lopatka from The Morton Arboretum Youth Education Department in Lisle, Illinois measured 15 cm (6 inches) of snow. The snow was caused by an Alberta Clipper. An Alberta Clipper is a type of low pressure system (storm) that moves from Alberta, Canada down across the Great Lakes. Storms in North America typically form to the east of the Rocky Mountains in either Colorado or Alberta, along the Gulf of Mexico or along the east coast of the United States. I am not familiar will storm tracks in Europe and Asia so I will check it out.

You can see in the map below that parts of the upper Great Lakes have over 50 cm of snow on the ground. The snow depth in the Great Lakes and northeast US is high for this time of year. Are we going to have a cold winter in this part of the world? We shall see.

Figure 1. Snow depth in the United States December 5, 2007. Source: National Operational Hydrologic Remote Sensing Center.

With all of the snow on the ground, the clear skies and calm winds due to high pressure, air temperatures in the Great Lakes area will get very cold tonight. We should see record low temperatures. The temperature is already –13° C (9° F) at my house this evening and the dew point is around –17° C (0° F). The dew point is the temperature at which condensation occurs. If the temperature reaches the dew point and condensation occurs, fog will form and latent energy will be released. This will keep the temperature from going down any further. So, we can expect that the low air temperature tonight at my house in Temperance, Michigan will be around –17° C (0° F). The record low for this area is –18° C (-2° F) from 1976 which was a very cold winter. The low temperatures in Minnesota tonight are going to be extremely cold. At the time I am writing this, it is –28° C (-20° F) in central Minnesota. Temperatures may get down to –34° C (30° F). The surface of the snow will be even colder. Why does the new snow cause the air temperature to get so cold? How will the surface temperature compare to the air temperature?

Students from more schools have entered data onto the GLOBE website for the surface temperature field campaign:

Bundle up.

Dr. C