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Seizing the Teachable Moment from the BRF Real Time Data

This webpage is intended primarily for educators who are planning a class field trip to Black Rock Forest and wish to make use of the environmental sensor data during their visit.

Introduction for Newcomers to Black Rock Forest:

The Black Rock Forest (BRF) is a 3750 acre (1500ha) preserve dedicated to scientific research, education, and conservation, located on the west bank of the Hudson River, 50 miles (80km) north of New York City. BRF is home to numerous ponds, ridges, wetlands, and great biological diversity. A consortium of schools, colleges, and research institutions operates Black Rock Forest, using it extensively for research on topics ranging from tree-rings to glacial geology, and for student field trips for ages ranging from kindergarten through graduate school. The forest has been instrumented with environmental sensors, which continuously measure and record properties of the air, soil and water. A suite of student activities based on data from the sensors have been developed to help students extend their experience of the forest beyond the few hours of a typical field trip.

The Real Time Data:

"Real Time" data are observational data that are made available to users immediately after the actual event or condition being observed has occurred. At Black Rock Forest, our data are actually "near-real-time" data, because the data are only transmitted from the environmental sensors to Forest Headquarters once per hour. This data transmission rate was chosen to conserve power. The transmitters at the sensors are powered by batteries which are recharged from solar panels. Continuous transmission of data would take more power than could be supplied by this system.

BRF [near] real time data can be displayed on a computer at the Forest Headquarters. There it is used by Forest staff to monitor the functioning of the remote sensor stations, and by scientists to monitor changing conditions in the forest that may call for an action in an observation campaign or a modification to an experimental design.

The real time data are also available to educators and school groups visiting the Forest. These data are most pertinent to classes which are studying, or have studied, weather, the water cycle, and/or habitats. If you wish to have access to real-time data during your class field trip, please indicate this to the Forest staff in advance of your trip.

What can students learn by looking at real time data?

Probably the most important insight you can convey from the real time data is that environmental factors vary across both time and space. At some level students probably know this, but because they themselves experience only one time and one place at any given moment, and because their knowledge and awareness of reality may still be quite egocentric, they may not really KNOW it very deeply. Furthermore, they may not realize that it is possible to measure and record and methodically examine how the environment varies from place to place and time to time.

Understanding how air, water and soil vary across time and space is important for understanding both the causes and the consequences of environmental variability. Thinking about causes leads to questions like: why is it that air temperature goes up and down on a 24 hour cycle? why is it that one site consistently has lower relative humidity than the other? Thinking about consequences leads to questions like: which of these places would be a better habitat for a particular animal of interest to me?

Teaching with the BRF Real Time Data:

Because real-time data are different every day, you cannot prepare in advance by pre-analyzing the data as you could for an activity built around archived data. You can to turn this to your advantage by allowing your students watch you think aloud as you observe and describe the salient properties of the data display. Involve your students in generating hypotheses about what might cause the data to look the way they do. Emphasize that this data is brand new; "we are the first people ever to describe and interpret this exact data set."

Although you cannot prepare by interpreting the data in advance, you can think in advance about which data you would like your students to look at. Air, soil and solar radiation measurements are made at two sites: Open Lowland and Ridgetop. Streamflow is measured in Cascade Brook. It may help to refer to the map of sensor locations as you plan. The readily-available data types are:
 Here are some things you may wish to do with your students during your visit before viewing the real-time data:

As you and your students first begin to look at the data, here are some general questions that are pertinent to most of the BRF real time environmental data displays:

 

Examples:

Air Temperature at Open Lowland and Ridgetop:

Following are some examples of real-time data displays, with notes on the kinds of questions that teachers can ask and the kinds of observations and interpretations that students can make. These four examples are related around the theme of diurnal variation in air temperature.

 

Air Temperature and Solar Radiation:

  • What are the two curves? (Blue is the air temperature, and yellow is the amount of solar radiation. Both are at the same site, Ridgetop.)
  • What's going on in this flat part of the solar radiation curve? (The flat part of the curve represents zero in coming solar radiation, in other words it is dark out, in other words it is night time.)
  • When does the peak in solar radiation occur? (At noon, at the moment when the sun is highest in the sky. If you have previously taught about how sun angle influences solar energy received at the Earth's surface, you could now ask why does the angle of the sun matter?)
  • If we were to look at many days worth of data, do you think the peak of solar radiation would always be at noon? (Not necessarily; some days would be cloudy and noon and sunny in the morning or afternoon. In that case, the peak of solar energy could be at an uncloudy moment in the morning or afternoon, even though the sun wasn't highest in the sky at that moment.)
  • Where is sunrise on the graph? (at the point where the solar radiation curve stops being flat and starts rising steeply) Where is sunset?
  • When is the coldest time in each 24 hour day? (Just before the dawn.)
  • Why is the coldest time just before dawn? (All through the night the Earth loses heat into space, and the temperature drops continuously. When the sun rises, it begins to heat the rock and soil, the rock and soil re-radiate heat into the overlying air, and the temperature begins to rise.)
  • Why doesn't the air temperature plunge to zero when the solar energy input goes to zero? (The molecules of the air and soil and rock still contain heat energy in the form of vibrating molecules, even though no new energy is coming into the system at night. Also, the data shown are on the Celsius scale. Zero degrees Celsius is the point at which water freezes, an arbitrary convenient choice of where to set the zero of the temperature scale. Zero degrees Celsius does not mean zero heat energy in the same way that $0 in your bank balance means zero dollars in your account.)
  • When is the hottest time in each 24 hour day? (An hour or two after noon, an hour or two after the peak in solar radiation.)
  • Why is the hottest time of day after noon rather than exactly at noon? (Sunlight does not heat the air directly, at least not very much. Instead, soil and rock absorb the light from the sun and re-radiate it as heat energy, infrared waves. This re-radiated energy is what does the work of heating up the overlying air. This process of re-radiating takes time and extends over time, and introduces a lag between the peak in arrival of solar energy and the peak in air temperature.)

 

Air Temperature and Soil Temperature:

  • What are the two curves? (One is air temperature, the other is soil temperature. Both are at the Ridgetop site.)
  • What differences can you see between the air temperature pattern and the soil temperature pattern? (The air temperature changes drastically from day to night, by about 12 degrees Celsius. The soil temperature also changes on a 24 hour cycle, but only by about two degrees. The daily high and lows of temperature in the soil occur after the corresponding highs and lows in the air temperature.)
  • Can you suggest a hypothesis to explain the differences between the air temperature and soil temperature patterns? (During the day, the sun warms the top layer of the soil. Heat conducts from the top layer of soil into the soil beneath. Soil isn't a good heat conductor, so this process of heat conduction through soil is slow and inefficient. Also, it takes a lot of heat to warm up a given volume of soil, especially wet soil. Thus the soil at 10cm beneath the surface doesn't get very warm. At night, heat is lost from the soil into the cool air, and the soil temperature drops. But again, this process is slow, and so the soil doesn't cool down very much during the course of a single night. The top layer of soil insulates the deeper layers from the extremes of both heat and cold in the air above.)
  • Does this data suggest any reason why an animal might want to live in a hole in the ground. (A burrowing animal can escape from extreme heat during the day and from extreme cold during the night.)

 

Relative Humidity at Open Lowland and Ridgetop:

Created by Kim Kastens, Lamont-Doherty Earth Observatory (kastens@ldeo.columbia.edu).
May be freely used for educational purposes provided appropriate credit is given.

Last modified November 5, 2003

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