An Exploration of Environmental Conditions Leading To Spatial Temperature Patterns at the Shale Hills Critical Zone Observatory

Open Access
Author:
Twiest, Burkely Lynn
Area of Honors:
Meteorology
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Kenneth James Davis, Thesis Supervisor
  • Johannes Verlinde, Honors Advisor
Keywords:
  • boundary layer meteorology
  • nocturnal drainage flow
  • instrument network
  • spatial temperature pattern
  • micrometeorology
Abstract:
A network of temperature sensors, sonic anemometers, and net radiometers was deployed to the Shale Hills Critical Zone Observatory, a .08 km2 forested valley in central Pennsylvania that is 49 m deep. These sensors collected data for a three-month time period spanning March-June 2013. Measurements were taken above-canopy (30 m above ground) and below-canopy (.914 m and 1.83 m above ground) to explore the occurrence of drainage flows and the establishment of a spatial temperature pattern on calm, clear nights. Analysis by a BestFirst classifying algorithm and a k-means clustering algorithm separated the nights of the study into two clusters: one with strong temperature differences throughout the valley and one without. These two clusters differed in the total amount of net radiation, above-canopy wind speed, presence or lack of below-canopy downvalley flow, and stability of the surrounding atmosphere. Nights with a stronger spatial pattern tended to have more negative average net radiation, calmer above-canopy wind speeds, and higher stability than the other cluster. Three-month composites of these variables across the nighttime period of 1930-0600 LST show differing evolution of net radiation, above-canopy wind speed, and total amount of cooling. The nature of the spatial temperature pattern in the two clusters was determined by assigning each sensor a rank and creating rank histograms. Both clusters showed evidence of a spatial temperature pattern. The more consistent spatial temperature pattern was found in the cluster with a weaker spatial temperature difference, perhaps indicating a strong link to radiative sheltering. The more variable spatial temperature pattern was found in the cluster with the stronger temperature difference. This variability suggests that mechanisms besides radiative sheltering were involved in developing the spatial temperature pattern throughout the valley on these nights. Downvalley flow is a likely contributor to the pattern.