TERRA Validation:Saudi Arabian Solar Radiation FluxGround Measurements

• Network Instrumentation
• Additional Instrumentation
• Calibration Instrumentation
• Calibration History of Annex II and BSRN Instrumentation
• Images of the Instrument Platform and Surroundings

The following table lists network instrumentation common to all sites:

TABLE 1. INSTRUMENTATION COMMON TO ALL NETWORK SITES.

PARAMETER	UNITS	SENSOR	MANF.	MODEL	UNCERTAINTY	COMMENTS
Ambient Temperature	Deg C	1000 Ohm Plat. Resistance Thermometer	Vaisala	50 Y	+/- 0.5 Deg C	Combined Temp. and RH sensor
Relative Humidity	% RH	Capacitive	Vaisala	50Y	+/- 2.5%	0%-100% range
Global horizontal solar Irradiance	W/m2	Type -T Thermopile	Eppley Laboratory	PSP	+/- 3.0% @ 1 kW/m2	Using single calibration factor
Direct Beam Solar Irradiance	W/m2	Type -T Thermopile	Eppley Laboratory	NIP	+/- 2.0% @ 1 kW/m2	5.7° field of view
Diffuse Horizontal Solar Irradiance	W/m2	Type -T Thermopile	Eppley Laboratory	PSP	+/- 3.0% @ 1 kW/m2	Under tracking shading disk subtending 5.7°
Solar Tracker: Direct Beam	n/a	Synchronous motor drive	Eppley Laboratory	ST-1	+/- 3.0° per day	manual alignment daily
Solar Tracker: Shade Disk	n/a	Synchronous motor drive	Eppley Laboratory	RSD-2	+/- 3.0° per day	manual alignment daily
Data Logger	volts	Analog to digital sample and hold	Campbell Scientific, Inc.	CR-10	0.2% Full Scale	Full scale: 25 mV Resolution 3.33 mV Time +/- 4 ms noise<0.8 uV RMS

All but Solar Village instrumentation is mounted on 0.5 m tall instrumentation platform at station ground level. At sandy soil sites, platform mounted on concrete pads. Solar Village Installation on 0.5 m tall instrumentation platform at 10 m above ground on building rooftop. Site layout to be incorporated into metadata.

Sample rate: 10 seconds (0.1 Hz)
Data rate: 5 minute (0.0033 Hz)
Clock accuracy +/- 2.0 Sec/ Day (set nightly with respect to national time standards)

Network Instrumentation Calibration History

The Solar Village station is instrumented with addition sensors designed to operate in conformance with WMO/WCRP BSRN specifications. BSRN instrumentation deployed at the Solar Village is described in table 2.

TABLE 2: SOLAR VILLAGE BSRN RADIOMETRIC INSTRUMENTATION

PARAMETER	UNITS	SENSOR	MANF.	MODEL	UNCERTAINTY	COMMENTS
Direct Beam Absolute Cavity Pyrheliometer	W/m2	Wire wound Type T Cu-Ct Thermopile solid silver inverted cone cavity	Eppley Laboratory	AHF Auto- matic Hickey- Frieden	+/- 0.45%	@ 1kW/m2 Corning 7940 fused silica window correction factor additional 0.8% uncertainty. Tracking by BRUSAG tracker
Downwelling longwave (sky irradiance) under Shading Disk	W/m2	Pyrgeometer Type T Thermopiles	Eppley Laboratory	PIR	+/- 10 W/m2	Silicon dome with thin film interference filter passing longwave (wavelength >8 micron ) infrared Shade disk mounted on BRUSAG tracker
Upwelling Longwave (ground emission)	W/m2	Pyrgeometer Type T Thermopiles	Eppley Laboratory	PIR	+/- 10 W/m2	As above, mounted at 100 ft (33 m) level at 3 ft (1 m) from 1 ft (0.3 m) diameter tower; body shaded from direct sun, downward looking
Upwelling shortwave radiation	W/m2	Type T Thermopiles	Eppley Laboratory	PSP	+/- 3.0% @ 1 kW/m2	100 ft (33 m) level at 3 ft (1 m) from 1 ft (0.3 m) diameter tower; body shaded from direct sun, downward looking
Solar Tracker: Cavity radiometer Direct Beam and downwelling longwave shade disk	n/a	Stepping motor drive	BRUSAG	INTRA	+/- 0.2° per day	autonomous, self correcting based on quad Silicon solar sensor input on clear days
Aerosol Optical Depth	n/a	filtered silicon cell sunphoto- meter(*)	CIMEL Electronique	CE-318	+/- 0.01 OD	Wavelengths at 340, 380,440,500,670,870, 1020 nm. Autonomous collection at 0.5 air mass intervals. Real time collection via METEOSAT at NASA Langley
Total Column Water Vapor	cm	as above	as above	as above	+/- 10%	Range 0.1-5 cm ( 1 mm to 50 mm)
Cloud Properties (height, layers)	km	Nd:YF diode laser source & EGG SPCM- AQ-121 avalanche diode detector	Science and Engineering Services, Inc.	MPL(**)	+/- 0.3 km	523 nm Wavelength, 18 bins up to 60 km 300 m resolution. Layer and boundary information from backscatter analysis

BSRN radiometric fluxes recorded at 2 second (0.5 Hz) sample interval with 1 minute (0.0167 Hz) averages reported.

BSRN Instrumentation Calibration History

BSRN and typical station instrument platform.	Panorama around base of 30 meter tower for upwelling radiation measurements.	Panorama around BSRN shortwave radiation site.