Net downwelling infrared radiation (IR) was measured using Kipp & Zonen CG4 pyrgeometer
located at NREL's Solar Radiation Research Laboratory's weather station to characterize the cloud cover at night.
The stations' weather instruments include a rain gage, anemometer, humidity sensor, pyrgeometer
(which measures broadband-IR flux), thermometer, and pyranometer (which measures radiation several micrometers in the IR).
Figure 14 illustrates pyrgeometer
and pyranometer measurements (Figs.
Variable Device/manufacturer Measurement height [m] Atmospheric C[O.sub.2] Licor 7500A open path infrared 2.65 and [H.sub.2]O gas analyser, LI-COR Biosciences, USA Wind speed in 3- CSAT3 ultrasonic anemometer, 2.65 dimensional field (w, Campbell Scientific, USA v, and w) and air temperature Incoming and outgoing CNR4 net radiometer (pair of 2.00 shortwave and longwave pyranometer and pyrgeometer
), radiations Kipp & Zonen, Netherlands Soil moisture content CS616, water content 0.03 reflectometer, Campbell Scientific, USA Soil heat flux HFP01SC, self-calibrating heat 0.08 flux plate, Hukseflux, Netherlands Soil temperature TCAV averaging soil 0.03 thermocouple probe, Campbell Scientific, USA Table 2: General parameters used for the SOLVEG simulations.
Instrument and model Measurement Pyrgeometer
, PIR Incoming longwave radiation Infrared radiometer Radiative surface canyon wall temperature (right facing), SI-131 Infrared radiometer Radiative surface canyon wall temperature (left facing), SI-131 Fine wire Air temperature thermistor, ST-200 Pyranometer, TSP-400 Incoming shortwave radiation GPS, I6X-HVS X, Y, Z coordinates Thermistor and Air temperature and relative humidity hygrometer, HC2S3 Thermocouple, Air temperature Type T (24 AWG) Infrared radiometer Radiative surface road temperature (road facing), Sl-IHI Data logger, CR3000 DAS Instrument and model Company Height (cm) Pyrgeometer
, PIR The Eppley Laboratory Inc.
Kipp & Zonen, 2001: CG4 pyrgeometer
: Instruction manual.
Approximately 20 buoys worldwide measure the full surface energy budget, with the primary limitation being the availability of a pyrgeometer
(longwave radiation sensor), as it is difficult to calibrate and maintain (Yu et al.
Figure 2 shows the annual cycle of the mean downwelling thermal radiation measured by a pyrgeometer
and overhead cloud fraction measured using a total sky imager.
Radiation A Solys2 sun tracker with two CP2I pyranometers (shaded and nonshaded) mea- suring visible radiation (0.285-2.80 pm), a CGR4 shaded pyrgeometer
measuring thermal radiation (4.50-42.0 pm), and a CHPI pyrheliometer measuring direct irradiance (0.20-4.00 pm).
Forcing data were incident short and long wave solar radiation (measured with Kipp & Zonen, Inc., pyranometers and pyrgeometers
facing up and down at a height of 9 m from the ground), air temperature and relative humidity (measured with Vaisala, Inc., model HMP 45C-L probe at the same height as the radiation sensors), horizontal wind velocity (measured with R.
Silicon-domed Eppley PIR pyrgeometers
, installed at 2 m above a grassy surface, were used as receivers of longwave radiation.
The net radiometer, which consists of two pyranometers and two pyrgeometers
, measures net radiant fluxes for both the solar (0.3-2.8 [micro]m) and the far infrared (5-50 [micro]m) spectrums separately.