NRES 408/808Instrumentation Demonstration --

Radiation Instrumentation

Mark Mesarch

229D Hardin Hall

472-5904 or mmesarch1@unl.edu

Office Hours

Homework Assignment 4 on Blackboard Questions:

Phone: 402.472.5904e-mail: mmesarch1@unl.edu

229D Hardin Hall

Purpose of Demonstration

Introduction to Instrumentation• NRES 469/869 Bio-Atmospheric Instrumentation

Examples ---- Not Exhaustive

More Than Just Numbers

Net Radiation Budget

Rn = RSW - RSW + RLW- RLW

WhereRn = Net RadiationRSW = Short wave Incoming

RSW = Short wave Outgoing

RLW = Long wave Incoming

RLW = Long wave Outgoing

Net Radiation BudgetCalculated Net Radiaion and Individual Components

Grass Mulch on 9/14/2005

-200

-100

0

100

200

300

400

500

600

700

800

900

0 4 8 12 16 20 24

Time ( Decimal Hour )

Rad

iant

Ene

rgy

Flux

( W

m-2

)

Rsw In Rsw Out Rlw In Rlw Out Rn Calculated

Net Radiation BudgetMeasured

Net Radiation Budget

WhereRn = Net RadiationRSW = Short wave Incoming

RSW = Short wave Outgoing

RLW = Long wave Incoming

RLW= Long wave Outgoing

Rn = RSW - RSW + RLW- RLW

Net Radiation Budget

At 13:30 on September 14RSW = 803.38 W m-2

RSW = 141.16 W m-2

RLW = 318.94 W m-2

RLW= 523.05 W m-2

Rn = 803.38 – 141.16 + 318.94 – 523.05

= 458.11 W m-2

Rn = RSW - RSW + RLW- RLW

Net Radiation Balance

Rn (Calculated) = 458.11 W m-2

Rn (Measured) = 423.85 W m-2

What Caused the Difference?

Design Your Own Instrument Setup

What will the instrument “see”? How is the instrument installed? How to maintain the instrument?

How Instruments “See”

Field of View (FOV)

• Demo

How Instruments See

How Instruments See

Hemispherical View

How Instruments See

How Instruments See

Specific Field of View

How Instruments See

24o Field of ViewHemispherical

How Instruments SeeHemispherical 30o FOV

Reifsnyder,W. 1967. Agr Meteorol 4: 255-265

How Instruments See

Hemispherical vs specific Field of View (FOV)

Spatial coverage

Demo

How Instruments See

How Instruments SeeSpatial Measurement Alternative

How Instruments See Calculating absorbed fraction of radiant flux

• Incoming (PARin)

• Reflected (PARR )

• Transmitted (ART )

• Soil Reflected (PARSR)

fAPAR = (PARin – PARR – PART + PARSR) / PARin

How Instruments See Appropriate wavelength coverage

How Instruments See

Individual measurements of incoming and outgoing long and shortwave radiation

KZ CN4 net radiometerKZ CNR1 net radiometer

How Instruments See

Incoming and outgoing all wave components

KZ CNR2 net radiometer(Discontinued)

How Instruments See

Single measurement of net radiation

KZ NR-Lite net radiometer

REBS Q*7.1 net radiometer

How Instruments See

Hemispherical vs Field of View (FOV) Spatial coverage

Appropriate wavelength coverage

Clear View :• Obstructions• Shadows• Mounting Frame• Single Plant vs Canopy

How is Instrument Installed? Mounting Frame

How is Instrument Installed? Mounting Frame Direction

How is Instrument Installed? Direction : North vs South

How is Instrument Installed? Direction : Nadir vs Off-Nadir

How is Instrument Installed? Mounting Frame Direction :

• North vs South• Nadir (straight down) vs Off-nadir (45° )

Height Above Canopy ????

How is Instrument Installed? Height Above Canopy:

• Static height

How Big is the Spot?

10 m

How is Instrument Installed? Mounting Frame Direction :

• North vs South• Nadir (straight down) vs Off-nadir (45° )

Height Above Canopy:• Constant height above canopy• Static height

Power Requirement

Row Crop vs Homogenous Canopy

Maintenance Requirements

Cleaning of Instruments

Maintenance Requirements

Cleaning of InstrumentsBird damage and droppings Rodent damage to wires

Maintenance & Repair

Rodent Damage

Maintenance Requirements Desiccant Checks

Maintenance Requirements

Cleaning of Instruments Desiccant Checks Leveling

Maintenance Requirements Level 2o off Level

Calibration

Factory and “in house” Calibrations

Frequency

Wavelength Characterization

Calibration

Factory and “in-house” Calibration

References

Eppley PSP pyranometers and Li-Cor Pyranometers

What Is A “Measurement”?

Output – millivolt and voltsSimple conversion to radiant flux by

multiplying output times calibration coefficient

Response time

Frequency of measurement - ?????

Instantaneous vs Average

Calibration

Factory and “in-house” Calibration

References

• Location of Instruments• Wavebands of Instruments• Calibration of Instruments• Level/Cleanliness• Rounding Errors

Net Radiation Balance

Rn (Calculated) = 458.11 W m-2 | Rn (Measured) = 423.85 W m-2

What Caused the Difference?

Questions?

What Instruments See How to Install Instruments How to Maintain the Instruments

Mark Mesarch

229D Hardin Hall 402.472.5904 or mmesarch1@unl.edu Assignment 4 on Blackboard (DUE: Sept 30)