As of 1 August 2017, the KCCI-TV SchoolNet Project was discontinued. This website will eventually go away as well. Thanks for your usage over the years since 2002! Questions? akrherz@iastate.edu

Select Lesson:

4. One Minute Data Traces

Objectives:

The goal of this lession is to explore the one minute data tracing application on the SchoolNet8.com website. This application provides the ability to explore current and historical data at a very fine resolution in time.

Variations in the weather take place on different 'time scales', or time periods over which the variations take place. Variations over long periods of time are called climate, while variations that occur in time periods shorter than 24 hours are typically described as weather. The 1 minute data plotter allows us to look closely at patterns that occur during the daily weather cycle.

SchoolNet8.com Online Resources:

The SchoolNet8.com one minute data trace application is one of the few sites on the internet that you can view graphs of weather observations at one minute resolution. These graphs can be found here:

Plots are available for all sites for any date in the archive that we have for the site. Some of the SchoolNet8.com sites have data dating back to 10 Feb 2002. Once you select a site and a date of your choice, you are presented three plots. Here is an example of the them.


This plot contains traces of air temperature (red line), dew point (blue line), and solar radiation (black line). The values for the temperature and dew point lines are defined along the left side y-axis, while the solar radiation values are defined along the right side y-axis. Having multiple y-axes are needed since the units and magnitudes of the temperature and radiation values are not the same. The time of day is expressed along the x-axis with a tick mark for the top of each hour. The blank space on the graph after 10 PM indicates missing data. Missing data occurs when the site no longer reports live information to the internet.


The second plot details the wind speed (red line) and direction (blue dots) along with the peak wind gust (black line) for the date. The values for wind direction are expressed on the left side y-axis. The values are in degrees from north, which means that 90 degrees is an east wind, 180 degrees is a south wind, and 270 degrees is a west wind. The values for wind speed and wind gust are on the right side y-axis and the values are in units of miles per hour. The black line, which represents the peak wind gust for the date, will only increase during the day. Due to the nature of how the wind gusts are reported by the SchoolNet8 sites, this is the best we can do.


The third plot details the atmospheric pressure and rainfall information for the date. Pressure is given in units of millibars and plotted on the left side y-axis. Rainfall information is shown on the right side y-axis and values are expressed in inches. The rainfall trace is a filled line plot, which makes for a nice illustration of accumulating rainfall.

Questions:

  1. From your SchoolNet site homepage, click on the 'Plot Data Timeseries' link found under the 'Site Resources' heading. You will be shown plots valid for today from your site. Take a look at the temperature trace (red line in the first plot). What can you say about how temperatures have changed for today?
  2. How does the dew point (blue line in the first plot) trace compare with the temperature trace? Does the dew point change as much as the temperature during the day?
  3. In the Solar Radiation lesson, we discussed how solar radiation can effect temperature. Do you see any impact of radiation on temperature for today?
  4. Look at the wind data trace. Which direction occured the most often during today? If your answer is a northerly direction, have temperatures cooled considerably?
  5. Take a look at the pressure trace. A good rule of thumb for Iowa is that every 4 millibars of pressure change can support 10 MPH winds. For example, if they pressure changed by 16 millibars for today, one would expect winds of roughly 40 MPH for parts of the day. Can you see signs of this rule of thumb on today's chart?
  6. The storms on the morning of July 10th 2002 were extremely strong. Check out the 1 minute trace for Glidden on this day. From the charts, can you determine when the strongest storm hit the area? From the three charts, describe what happened during this storm.

Possible Answers

  1. In general, you should note an increase in temperature during the day and cooling at night. Sometimes fronts and precipitation can alter this normal cycle. If there are alterations in this normal cycle, can you explain what caused them?
  2. Dew point must always be lower than or equal to the temperature. Dew Point is the value when the air is 100% saturated, which means that the air can not hold any more water vapor. In general, the dew point does not vary much throughout the day. While the temperature increases, the actual moisture content remains mostly the same. If you notice changes, it is probably because of evaporation, moisture advection, or perhaps a faulty sensor.
  3. The effect of solar radiation on temperature will vary from season to season and be modified by other conditions. In general, an increase in radiation should lead to an increase in temperature. If this did not happen, can you guess as to why?
  4. You can determine the main wind direction by looking at which direction has the majority of the blue dots. This will vary day to day with the passing weather systems.
  5. The pressure trace should give you an indication on how windy it was during the day. Large changes in pressure imply stronger winds. Winds are generated from horizontal differences in pressure, so if there is a large pressure change during the day, one would expect a strong winds as well.
  6. The July 10th 2002 storm was an amazing storm. The Glidden SchoolNet8 site got absolutely slammed by a dangerous storm right at 7 AM in the morning. Each plot indicates a different effect of what happened from this storm. The temperature plot shows the sudden decrease in temperature associated with the rain cooled air being dropped by the thunderstorm. The wind plot shows the rapid and intense winds that occured at this time. While not shown on this plot, a peak gust of 96 MPH was measured at the site! The most impressive plot is the last one. Notice the 8 milibar increase in pressure with 2 inches of rain that rapidly fell from this storm. Meteorologists refer to this storm as a downburst. Downbursts are caused by a thunderstorm that rapidly decays and slams a small pocket of very cold air to the ground which then spreads out causing straight line wind damage.

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