The Barrens Microclimate

The Centre County Barrens is the coldest region in Pennsylvania once the sun sets. The Barrens is just four miles west of Penn State's main campus located in State College. Its average high temperatures for a given period are very similar to that of State College's, but the average low temperature is significantly lower. The nighttime temperature can be up to 30 degrees Fahrenheit lower. The temperature at the Barrens can fall over 9 degrees Fahrenheit per hour during or just after sunset. It is not unusual for the diurnal temperature change to be over 50 degrees Fahrenheit. These large temperature falls occur during nights that provide optimum cooling, on clear, calm nights. Also, in winter snow reflects the suns energy away from the surface. Since the Barrens is a colder place that State College, snow stays longer, causing less heating of the surface.

The large diurnal change is possible thanks to its topography and vegetation. The Barrens is located in a narrow valley between two mountain ridges. This causes cold air from the mountains to come down into the valley during and after sunsets. The large mountain slopes enables a large volume of cold air to flow into the Barrens. In the 1800's, the mining of iron ore, widespread fires, and indiscriminate use of the forest for charcoal deforested the area. Many areas in the Barrens were cut a second and third time to add to the problem. Now all that remains are a few pine and scrub oak trees. The sandy soil of the Barrens allows the ground to radiate heat more readily than other surfaces and allows water to be absorbed deep into the ground, keeping the surface layer dry.

The Barrens will keep receiving its very cold nighttime temperatures until vegetation is restored. However this is a very difficult thing to restore with the Barrens cold temperatures. The Barrens simply drop below freezing too often to restore vegetation quickly. Also, the soil in the area is very acidic, which declines plant growth. For now, the Barrens will remain a cold place during the night because of its topography and vegetation.

Table 1: Frequency Distribution of Temperatures at the Barrens and State College (1200Z to 1200Z from December 1977 to November 1978)
Maximum Temperature (°F) State College # of days (%) Barrens # of days (%)
less than or equal to 32 63 (17%) 69 (19%)
greater than or equal to 33 302 (83%) 296 (81%)
Minimum Temperature (°F) State College # of days (%) Barrens # of days (%)
less than or equal to 0 1 (0.3%) 31 (8%)
less than or equal to 32 135 (37%) 206 (56%)
greater than or equal to 33 230 (63%) 159 (44%)

This table shows that the day time temperatures throughout the year are almost exactly identical for both the Barrens and nearby downtown State College. However, as daytime heating begins to leave the atmosphere as the sun sets, cold air begins filtering down into the low lying area of the Barrens and temperatures plummet whereas in State College they fall more moderately. During this time period State College only fell below 0°F one night, while the Barrens mustered an entire months worth more. And while the majority of State College nights are usually above freezing (during the late spring, summer, and most of the fall months), the Barrens would often fall below 32°F on those nights.

This final table shows the lowest recorded temperature in the Barrens each month during the initial study by William S. Clarke in the 1940's and the most recent study in the late 1970's. The obvious observation is that minimum temperatures today are not quite as severe as they were during the second World War. However, they still are not comparable to what downtown State College experiences every night.

Table 2: Table of Extremes in Minimum Temperature of the Barrens Observed by Clarke and the Most Recent Study.
  Clarke's Observations (1941-1952) Most Recent Observations (1977-1978)
Month Lowest Temperature (°F) Lowest Temperature (°F)
January -40 -20
February -24 -26
March -27 -13
April -14 +5
May +2 +5
June 21 25
July 22 30
August 23 33
September 14 18
October +8 +11
November +1 +9
December -25 -21

Finally, click on some of the links below for schematic diagrams as well as charts which depict even better the drastic difference in night time temperatures between downtown State College and the microclimate of the Barrens, which are separated by a mere 4 miles.

Topographical Map of State College and Barrens

Cross Section of Nittany Valley Compared to the Barrens Valley

Average Monthly Maximum and Minumum Temperatures for State College and Barrens

Average Monthly Diurnal Temperature for State College and Barrens

Hourly Temperature Diagram of State College vs. Barrens on 3-4 February 1978

Number of Occurances of Rates of Temperature Fall in Barrens Over One Year

Average Snow Cover Amounts (in inches) for State College and Barrens