|This is the variation of DLWIR with day of the year (as before but low prob results retained)|
|This is absolute humidity effect - not linear|
|Interesting (night is disabled - no cloud information) but DLWIR is greater in mornings and evenings. Why not midday?|
|Station Pressure - Possibly a problem with conversion between % hum and abs humidity causes this.|
|Linear effect with temperature as would be expected|
|Again a non linear relation with ULWIR|
Cloud values are measured using a visual light camera - hence no results will be returned for hours of darkness for this analysis.
PRECISION INFRARED RADIOMETER
The Precision Infrared Radiometer, Pyrgeometer, is intended for unidirectional operation in the measurement, separately, of incoming or outgoing terrestrial radiation as distinct from net long-wave flux. The PIR comprises a circular multi-junction wire-wound Eppley thermopile which has the ability to withstand severe mechanical vibration and shock. Its receiver is coated with Parson's black lacquer (non-wavelength selective absorption). Temperature compensation of detector response is incorporated. Radiation emitted by the detector in its corresponding orientation is automatically compensated, eliminating that portion of the signal. A battery voltage, precisely controlled by a thermistor which senses detector temperature continuously, is introduced into the principle electrical circuit.
Isolation of long-wave radiation from solar short-wave radiation in daytime is accomplished by using a silicone dome. The inner surface of this hemisphere has a vacuum-deposited interference filter with a transmission range of approximately 3.5 to 50 µm.
Sensitivity: approx. 4 µV/Wm-2.
Impedance: approx. 700 Ohms.
Temperature Dependence: ±1% over ambient temperature range -20 to +40°C.
Linearity: ±1% from 0 to 700 Wm-2.
Response time: 2 seconds (1/e signal).
Cosine: better than 5%.
Mechanical Vibration: tested up to 20 g's without damage.
Calibration: blackbody reference.
Size: 5.75 inch diameter, 3.5 inches high.
Weight: 7 pounds.
Orientation: Performance is not affected by orientation or tilt.
This looks as if it is measuring the heating effect (thermopile) of radiation hitting the dome of the sensor (transmission 3.5 to 50um. The thermopile of course generates a voltage dependant on the temperature difference between one side and the other The non-dome side is not exposed to external radiation so no effect there. However, the nondome side temperature must be measured and compensated.
The instrument also compensates for its own generated IR.
No assumption of BB radiation is assumed. It is the ACTUAL heating effect of IR radiation of narrow or wide bandwith hitting the sensor that is the cause.
If the radiative "temperature" is less than the receiver temperature then the thermopile still measures - see series of posts about thermal imaging - the camera microbolometers sitting at 20+C shows temperatures down to -40C
Dry bulb temperature / wet bulb / relative humidity
- Supply Voltage: 12 Vdc nominal (typically powered by datalogger)
- Current Drain: ≤4 mA (active)
- Sensor Diameter: 2.5 cm (1 in.)
- Sensor Length: 25.4 cm (10 in.)
- Cable Diameter: 0.8 cm (0.3 in.)
- Weight: 0.27 kg (0.6 lb)
- Sensor: Vaisala’s HUMICAP® H-chip
- Measurement Range:
0.8% to 100% RH, non-condensing
- Output Signal Range:
0.008 to 1 Vdc
- Accuracy at 20°C (against factory reference): ±1% RH
- Accuracy at 20°C (field-calibrated against references):
±2% (0% to 90% RH);
±3% (90% to 100% RH)
- Temperature Dependence: ±0.05% RH/°C
- Long-Term Stability: Typically, better than 1% RH per year
- Response Time: 15 s with membrane filter (at 20°C, 90% response)
- Settling Time: 500 ms
- Temperature Sensor: 1000 ohm Platinum Resistance Thermometer
- Measurement Range: -39.2° to +60°C
- Output Signal Range:
0.008 to 1.0 V
Cloud - total and opaque
TSI-880 AUTOMATIC TOTAL SKY IMAGER
The Total Sky Imager Model TSI-880 is an automatic, full-color sky imager
system that provides real-time processing and display of daytime sky conditions.
At many sites, the accurate determination of sky conditions is a highly
desirable yet rarely attainable goal. Traditionally, human observers reported
sky conditions, resulting in considerable discrepancies from subjective
observations. In practice, the use of human observers is not always feasible due
to budgetary constraints. The TSI-880 now replaces the need for these human
observers under all weather conditions.|
An onboard processor computes both fractional cloud cover and sunshine duration, storing the results and presenting data to users via an easy-to-use web browser interface. The self-contained design makes it well suited for mission-critical applications such as aviation and military meteorology monitoring. It captures images into standard JPEG files that are analyzed into fractional cloud cover; if networked via TCP/IP (10/100BaseT) or PPP (modem) it becomes a sky image server to remote any user via the web.