倒车雷达英文文献.docx

A R E VERS I NG TEM PER AT UR E- DI F FER E N CE M EA SUR EM E N T SY STEM FOR BO W E N R ATI O DET E RM I NATION J.H. M c CA U G H E Y Department of Geography, Queen’s Unirersity, Kingston, Ontario, Canada, K7L 3N6 (Received 10 October, 1980) Atatract. The design and performance of a reversing temperature difference measurement system are reportecl This system employs five-junction copper-constantan thermopilcs for the measurement of A and A Tp, while a linearized thermistor is used to measure Tp. Field performance has been checked against a precision lysimeter as well as against a second temperature difference measurement system in which diode are used for temperature measurement. In both cases, the agreement between the systems is satisfactory for the measurement of hourly values of the Bowen ratio. 1. Introduction The experimental determination of the Bowen ratio by the psychrometric method requires careful measurement of the gradients of temperature and humidity above a surface. Wherever these gradients become smal( for example over an aerodynamically rough surface such as forest, then very careful and stringent measurement techniques are required in order to achieve satisfactory results. A now commonly used method to determine the Bowen ratio is to measure directly the differences of dry-bulb temperature (AT) and wet-bulb temperature (ATp) over some height interval (Az), and to interchange the psychrometers on a regular basis. This approach was proposed by Tanner (1960), and has been operationalized by Sargeant and Tanner (1967), Black and McNaughton (1971), and Spittlehouse and Black (1980). The rationale of this method is that, if systematic error is present in the measurement and is either constant or slowly changing then interchanging the psychrometers between levels should eliminate or greatly reducu the amount of error in the measurement of the mean