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Airborne Radiometers to Measure Electromagnetic Radiation in the Earth’s Atmosphere: Mature and Emerging Technologies
Published in John G. Webster, Halit Eren, Measurement, Instrumentation, and Sensors Handbook, 2017
Terrestrial radiation can be measured with an IR thermometer or a pyrgeometer, for example, Eppley precision IR radiometer (PIR) or Kipp & Zonen pyrgeometers. The measurement principle for the pyrgeometer is based on the exchange of energy between hotter and cooler objects (Foot, 1986; Philipona et al., 1995). Assuming that the instrument is one of the objects, the instrument absorbs or emits energy if it is cooler or warmer than the object that is being sensed. A pyrgeometer is used to measure, hemispherically, the exchange of terrestrial radiation between a horizontal blackened surface (the detector) and the target viewed (i.e., the sky or the ground). The PIR has the same circular multijunction thermopile detector as the pyranometer, which is used as a method of transducing the terrestrial radiation flux into an electric response. The inner silicon dome is coated with a vacuum-deposited interference filter. Radiation at wavelengths from 0.3 to 0.4 μm to approximately 50 μm is transmitted into the sensor. The amount of radiation in the visible spectrum 0.3–4.0 μm is not significant; absorption and reemission effects are small and are compensated for in the calibration.
Longwave radiation exchange at external surfaces
Published in Ian Beausoleil-Morrison, Fundamentals of Building Performance Simulation, 2020
It is possible to measure the downwelling longwave irradiance using a pyrgeometer, a device resembling a pyranometer that is used to measure solar irradiance. If Gsky↓ were directly measured in this way and made available in the weather file, then it could be directly used in Equation 11.4 to calculate qjw,e→sky.
Radiometer Calibrations
Published in Frank Vignola, Joseph Michalsky, Thomas Stoffel, Solar and Infrared Radiation Measurements, 2019
Frank Vignola, Joseph Michalsky, Thomas Stoffel
By 2004, PMOD/WRC had established the WISG of pyrgeometers to serve as an interim transfer standard group with respect to its reference scale (WMO 2006). The WISG consists of four pyrgeometers—two modified Eppley Model PIRs and two Kipp & Zonen Model CG4s)—that were calibrated relative to the ASR and have not been changed since (Gröbner and Wacker 2015). The estimated expanded measurement uncertainty for pyrgeometer calibrations based on the WISG is ±2.6 Wm−2 with a 95 percent level of confidence (Nyeki et al. 2017). The continued need for a more accurate reference measurement standard has prompted the independent development of two new absolute measurement systems. The Infrared Integrating Sphere (IRIS) radiometer (Gröbner 2012) and the Absolute Cavity Pyrgeometer (ACP) measurement system (Reda et al. 2012) are windowless to eliminate the measurement performance complications due to the optical and thermal complexities presented by the presence of an enclosure window (see Figures 13.6 and 13.7). The windowless design of these advanced research measurement systems does, however, limit their use to fair weather, nighttime conditions. The WISG instruments are designed for all-weather operations and provide continuous measurements for pyrgeometer calibrations. The four WISG pyrgeometers typically agree to within ±1 Wm−2. Results of two measurement intercomparisons of the WISG, IRIS, and ACP instruments under nighttime clear-sky conditions have demonstrated a need for revising the existing interim WISG (Gröbner et al. 2014). The IRIS and ACP measurements under nighttime clear-sky conditions agree within ±1.5 W m−2 (Gröbner and Thomann 2018). Comparisons of the WISG, IRIS, and ACP indicate the WISG is underestimating longwave irradiance during these same conditions by 2 to 6 W m−2, depending on the amount of integrated atmospheric water vapor (WV). During outdoor measurement conditions when WV exceeds 10 millimeters (mm), an average thermopile sensitivity (parameter C in Equation 13.3) correction of +6.5 percent is needed for the WISG pyrgeometers to better agree with the ACP and IRIS measurements (Gröbner et al. 2014; Gröbner and Thomann 2018). Until a more accurate measurement reference is developed for broadband IR radiation measurements under all weather conditions, pyrgeometers calibrated to the WISG will likely require a similar thermopile sensitivity increase determined from the adjusted WISG and archived calibration data for U, TB, and TD (Nyeki et al. 2017).
Evaluation of the relationships and uncertainties of airborne and ground-based sea ice surface temperature measurements against remotely sensed temperature records
Published in International Journal of Digital Earth, 2022
Pei Fan, Xi Zhao, Meng Qu, Zhongnan Yan, Ying Chen, Zeyu Liang, Xiaoping Pang
Given its association with surface energy budget, IST can be derived from longwave radiation (LWR) by inverting the Stefan–Boltzmann Law. In this study, the surface broadband longwave radiation collected during the Norwegian young sea ICE Campaign (N-ICE 2015) (Hudson, Cohen, and Walden 2016) and the previously mentioned AWS during CHINARE-2014 were used to derive LWR IST. Both campaigns used Kipp and Zonen pyrgeometer to measure surface up and downward longwave radiation flux. The spectral range of the pyrgeometer is 4.5–42 microns, wider than that of the infrared radiometer. The N-ICE 2015 radiation station functioned from January 21, 2015 to June 19, 2015, and reported data every minute, while CHINARE-2014 provided hourly radiation information together with IR IST. More details on the device and deployment information can refer to Walden et al. (2017) and Pan (2015). In this work, 137 points of N-ICE 2015 and 692 points of CHINARE-2014 LWR IST measurements were matched with referential IST.
Blue skies and red sunsets: Reliability of performance parameters of various p-n junction photovoltaic module technologies
Published in Cogent Engineering, 2019
Edson L. Meyer, Ochuko K. Overen
The SGD sun tracker comprises of a CHP 1 pyrheliometer, CGR4 pyrgeometer and two sets of CMP10 pyranometers. The SGD sun tracker was designed to offset the diurnal and seasonal movement of the earth (Mousazadeh et al., 2009). Hence, the payload was constantly pointed toward the sun. This was achieved by a sun sensor installed in the system. The sun sensor identifies the area in the sky with maximum solar intensity and directs the payload to that region. Besides the sun sensors, the tracker uses the coordinate and local time obtain by the integrated GPS antenna to track the daily movement of the sun. In this regard, the pyrheliometer used to measure direct normal irradiance was mounted on the payload. Thus, the pyrheliometer was also constantly pointed towards the sun. Whereas, the Pyrgeometer and two pyranometers located on the platform of the sun tracker, move about their axis. The pyrgeometer measures downward longwave radiation; in other words, the re-emitted (infrared) radiation of the atmosphere. While the pyranometer located at the extreme right end of the platform, measures diffused solar irradiance. As such, the shading assembly shields the pyrgeometer from direct short-wave solar radiation, which heats the pyrgeometer window. At the same time, it prevents direct solar radiation from the pyranometer. Combine direct, and diffuse irradiance on a horizontal plane was measured by the pyranometer located at the centre.
Towards a better understanding of the evaporative cooling of rivers: case study for the Little Southwest Miramichi River (New Brunswick, Canada)
Published in Canadian Water Resources Journal / Revue canadienne des ressources hydriques, 2023
Valerie Ouellet, Daniel Caissie
Little Southwest Miramichi River (LSWM) microclimate conditions were collected during the period between June 12, 2012 (day 164) and September 6, 2012 (day 250), and results of hourly data are shown in Figure 2. Figure 2a shows the incoming shortwave radiation (measured from the pyranometer) and incoming longwave radiation (measured from the pyrgeometer). Hourly data showed the diel cycles in both shortwave and longwave radiation. Peak values of incoming solar radiation generally reached 900 W m−2 early in the season (days 164–172) and declined towards the end of the study period (e.g. < 800 W m−2 days 223–250). The mean value for incoming solar (shortwave) radiation for the period was 205 W m−2, with higher daily means at the beginning (∼ 300 W m−2) and lower daily means towards the end of the period (∼ 150 W m−2). Incoming longwave radiation generally ranged between 295 W m−2 and 430 W m−2, with a mean value of 370 W m−2 for the study period. Notably, measured incoming longwave radiation followed the air temperature diel cycle and was also influenced by cloud cover. For instance, higher daily mean values were observed on cloudy days (e.g. days 174–180; days 223–226), while greater diel variability was observed during clear/sunny days. Figure 2b shows the study period’s air and water temperature times series. Air temperature ranged from 5 °C to 31 °C, with an overall mean air temperature of 18.7 °C. Morning temperatures were low, especially at the beginning and toward the end of the study period (e.g. minimum temperatures of 5 °C on days 169 and 246; Figure 2b). High air temperatures of 29–31 °C were observed on several days (e.g. days 172, 194, 197, 213, 218, and 239–240) with corresponding high water temperatures. The diel pattern of water temperatures was similar to that of air temperatures but with reduced diel variability (Figure 2b). Water temperature ranged between 14.3 °C and 27.9 °C, with an overall mean water temperature of 20.6 °C. The mean summer water temperature in the Little Southwest Miramichi River was higher than the mean air temperature (by 1.9 °C; 20.6 °C vs. 18.7 °C). Figure 2c shows the daily river discharge as well as hourly precipitation data. Discharge was under baseflow condition (i.e. without precipitation; discharge < 20 m3 s−1) for most of the summer; however, it responded to precipitation events. For instance, the discharge increased from 10 m3 s−1 (day 173) to 107 m3 s−1 (day 180) following 146 mm of rain, which fell over 8 days between June 22 and June 30 (days 174–182).