A rigid fast-response thermometer for atmospheric research

Abstract

Abstract. A fast-response temperature sensor for measuring atmospheric temperature was constructed and is described. The sensor was based on the thermocouple principle, connected to a thermocouple conditioner (AD595): the cold junction was compensated via an electrical reference and the signal amplified. This reference compensation was built into the sensor itself.The time constant of the thermocouple was decreased by rolling out a circular wire. The advantage of this technique was that the original mechanical strength was retained. The disadvantage was that the excess temperature could increase due to a higher interception of global irradiation. It appeared that by reducing the time constant by a factor of five, the radiation error could be increased by a factor of two, depending on the orientation of the sensor head and the angle of attack of the incoming direct radiation beam.The mean temperatures measured by the sensor were compared with those measured by an accurately calibrated Pt 100 resistance thermometer. The agreement between both sensors for outdoor measurements gave a standard error of estimate of 0.20 K.The fast outdoor temperature excursions around the running mean, measured by the sensor, were compared with those measured by a fast-response sonic thermometer. The agreement of the temperature variances between both sensors was better than 2% (standard error of estimate 0.05 K) and was dependent on measuring height and mean windspeed. The 3 dB point of the instrument was about 2 Hz.

The dependence of canopy layer turbulence on within-canopy thermal stratification

“…Within the crop, mean wind speed and temperature profiles were measured with hot-sphere anemometers (Stigter et al, 1977 ) and fine-wire thermocoupies (Van Asselt et al, 1991 ), respectively, at heights above the ground of 0.1,0.2, 0.3, 0.4, 0.7, 1.0 and 1.4 m. Moreover, a one-dimensional sonic anemometer (Kaijo Denki type PAT-110 ) oriented to measure the vertical component of the wind, an additional fast-response thermometer and Lyman-a humidity sensor were installed at a height of 0.7 m.…”

Horizontal and vertical distribution of air temperature in a vegetation [maize] canopy.

“…Within the canopy, at 0.25 D between two rows (where, D is row distance), the mean temperature profile was estimated with fast-response thermometers (Van Asselt et al, 1991) at heights above the ground: 0.0, 0.1, 0.2, 0.3, 0.5, 0.7, 1.0 and 1.4 m. The thermometers were based on the thermocouple principle. The accuracy for measuring the mean temperature was better than 0.05 °C and their first-order time constant was about 0.08 s. To gain insight into the horizontal variability of the wind speed, at two levels, 0.3 and 0.7 m, measurements were made at 0.25 D, 0.50 D, 0.75 D and 1.00 D.…”

Horizontal and vertical distribution of wind speed in a vegetation canopy.

“…The mean temperature and moisture profiles were measured at two levels at heights of 2.0 and 4.0 m with home-made aspirated psychrometers. At a height of 4.5 m, a 3-D sonic anemometer of Kaijo Denki (DAT-310) with an additional fast-response thermometer (van Asselt et al, 1991) and Lyman-a sensor were installed. These in struments provide data about the above-crop thermal stratifcation of the at mosphere.…”