Construction of a Compact Low-Cost Radiation Shield for Air-Temperature Sensors in Ecological Field Studies

Summary

With the advent of small, low-cost environmental sensors, it is now possible to deploy high-density networks of sensors to measure hyper localized temperature variation. Here, we provide a detailed methodology for constructing a compact version of a previously described custom-fabricated radiation shield for use with inexpensive thermochrons.

Abstract

Low cost temperature sensors are increasingly used by ecologists to assess climatic variation and change on ecologically relevant scales. Although cost-effective, if not deployed with proper solar radiation shielding, the observations recorded from these sensors will be biased and inaccurate. Manufactured radiation shields are effective at minimizing this bias, but are expensive compared to the cost of these sensors. Here, we provide a detailed methodology for constructing a compact version of a previously described custom fabricated radiation shield, which is more accurate than other published shielding methods that attempt to minimize shield size or construction costs. The method requires very little material: corrugated plastic sheets, aluminum foil duct tape, and cable ties. One 15 cm and two 10 cm squares of corrugated plastic are used for each shield. After cutting, scoring, taping and stapling of the sheets, the 10 cm squares form the bottom two layers of the solar radiation shield, while the 15 cm square forms the top layer. The three sheets are held together with cable ties. This compact solar radiation shield can be suspended, or placed against any flat surface. Care must be taken to ensure that the shield is completely parallel to the ground to prevent direct solar radiation from reaching the sensor, possibly causing increased warm biases in sun-exposed sites in the morning and afternoon relative to the original, larger design. Even so, differences in recorded temperatures between the smaller, compact shield design and the original design were small (mean daytime bias = 0.06 °C). Construction costs are less than half of the original shield design, and the new design results in a less conspicuous instrument that may be advantageous in many field ecology settings.

Introduction

In light of anthropogenic global warming, there has been a growing interest in recording air temperature in a variety of settings to understand and predict ecological responses to climate change^1,2,3. With the advent of small, low-cost environmental data recorders (also referred to as data loggers, thermochrons, or hygrochrons), it is now possible to deploy high-density networks of sensors to measure hyper localized temperature variation, increasing ecologists' ability to more directly observe the ambient environmental conditions experienced by organisms and ecosystems un....

Protocol

1. Construction of the Radiation Shield

1. Using a utility knife, cut the corrugated plastic sheets into squares (Figure 1A). One 15 cm square and two 10 cm squares will be needed for each shield.
2. Cuts for the top layer of the small radiation shield (Figure 1B; left image):
   1. On the 15 cm square, measure 4 cm from one edge and draw a line with a pencil. Use a straightedge as a guide to score along the line. (Herein, “scoring” means using a knife to make a cut that goes through only one layer of corrugated plastic sheet, rather than the entire sheet.) Henceforth this edge of the sq....

Results

Representative results using thermochrons outfitted with the new, smaller shield design, the original larger shield design, and the thermochrons with no radiation shield are shown in Figure 2 and Figure 3. These data were recorded at a fully exposed rural location near Raleigh, NC (35.728°N, 78.680°W), and were affixed to a well-calibrated permanent weather station outfitted with a VAISALA platinum resistance air.......

Discussion

The accuracy and repeatability of air temperature measurements depend on the use of an appropriate solar shield that protects the sensor from direct and reflected solar radiation. Here we describe the construction of such a shield that is more compact in size, less expensive, or faster to construct than similar, previously described devices⁶, without sacrificing accuracy. 94% of the recorded temperatures for the thermochrons outfitted with the smaller shield were within 1.0 °C of the best per.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Multipurpose Aluminum Foil Tape	Nashua	1087671	48 mm width
8" cable ties	DTOL	GEN86371	NA
Corrugated plastic sheet	Highway Traffic supply	hts18X24COROW	White sheet 18"L x 24"W, 5-pack
Standard utility knife	NA	NA	NA
Standard Scissors	NA	NA	NA
Heavy duty stapler	Swingline	552277715	NA