Delta Electronics SS1-UM-1.05 user manual Modelling the canopy transmission

Page 58

Diffuse light transmission (cosine corrected sensor)

 

 

Transmission

1

 

 

 

 

 

 

 

fraction

 

 

 

 

 

 

Leaf Angle Distribution

0.1

 

 

vertical

 

 

 

τ

diff( 0 , L )

 

 

 

 

 

vertical

 

 

 

 

 

 

spherical

τ

diff( 1 , L )

 

 

 

 

 

 

horizontal

τ diff( 1000 , L )

 

 

 

spherical

 

 

 

 

 

 

 

 

 

 

0.01

 

 

 

 

 

 

 

 

 

 

horizontal

 

 

 

 

 

0.001

2

4

6

8

10

 

 

 

0

 

 

 

 

 

L

Leaf Area Index

 

Modelling the canopy transmission

Accounting for incomplete absorption of PAR by the canopy elements, and scattering of light within the canopy is complicated. It is no longer sufficient to consider only the vertical component of PAR (i.e. as measured by a cosine-corrected sensor) because scattering effectively transfers power between the horizontal and vertical components, so the canopy changes the spatial distribution of power in the PAR flux as it is transmitted down through the canopy and reflected back up.

A multi-stream computer model was set up to calculate these effects as follows.

Assumptions

•The canopy is an infinite, uniform, horizontal slab, with leaf elements randomly distributed in proportion to the surface area of an ellipsoid, as described by Campbell.

•The incident light consists of a component from a point source at a given zenith angle (the Direct Beam); and a Diffuse component of equal intensity from every point in the sky (Uniform Overcast Sky).

•The canopy either has sufficiently high LAI that light reflected back from the ground below is negligible, or the reflectance of the ground is similar to that of the canopy.

•Of the light intercepted by the leaf element, a fraction a (absorption) is totally absorbed. The remainder is re-emitted uniformly in all directions.

58 • LAI theory

Document code: SS1-UM-1.05

Page 57 Page 59
Image 58
Page 57 Page 59
Contents SunScan SS1-UM-1.05Trademarks CopyrightAcknowledgements CE conformityContents LAI theory Menus and Screens More Psion and file handling notesMeasurement options Technical Reference sectionAppendices IndexSunScan Canopy Analysis System How to use the manualsIntroduction Organisation of this manualBeam Fraction sensor Field accessoriesSunScan probe Data Collection TerminalPreliminary checks Getting StartedWorkabout and SunScan probe Checking the Workabout hardware SunData s/w Diskette Installing the SunData s/w in your PCInstalling the s/w What the s/w doesSetting up your PCs COM port Running SunDataSunScan probe to PC Communication checksWorkabout to PC Running SunData in Windows About this tutorial SunScan TutorialWorking with the Workabout What to do if you get lost Starting SunData in the WorkaboutUsing a PC instead of the Workabout Starting the PC softwareThis page is intentionally blank Setting up a measurement session Working through the menu optionsFile Saving Hot KeysUsing the Emulator mode Taking readingsConnecting the SunScan probe Without a Beam Fraction SensorConnecting the Beam Fraction Sensor Measuring Leaf Area Index without a Beam Fraction Sensor Reviewing your data file AveragesFrom the Workabout Transferring the data file to your PCTo the PC Initiating the file transfer from the Workabout Meanwhile, on the PC RS232 communication problems Conclusion of the TutorialSunData Screens on the Workabout Menus and Screens SettingsFile Contd UtilsQuit Workabout User Guide More Psion and file handling notesNavigating Psion directories and screens Navigating the Psion directories and screensPsion subdirectory usage in file select dialogs Deleting unwanted Workabout files Re-installing the SunData application iconFlashcards reformatting SunData Configuration files Configuration and data file handlingData memory management Restoring a configuration Default .cfgCreating a configuration file Data files.PRN file Displaying data files on your PC.CSV file Data file layouts and data groups Page Experiment design Measurement optionsAbove-canopy reference requirements Canopy type and BFS practicalities Canopy Sampling volumeCanopy type and LAI estimates Preferred light and weather conditions Planning for the sun’s positionSetting Eladp Advice on Absorption and Eladp valuesAbsorption Relationship between Mean Leaf Angle and Eladp Estimating Eladp in the fieldSunScan System Measurement modes Workabout setupLAI, PAR and All displays Autolog function Probe GO button Measurement procedures in the fieldProbe handling in the field Levelling the probeUse of the tripod Using the tripodBFS handling in the field WorkaboutLevelling the BFS Finding North, and setting the shade ringExtension cables, and the location of the BFS Checking the probe/BFS matching PAR calibrationsFactory light calibration Recalibrate optionEffect of the shade ring on the BFS Routine maintenance and cleaningRestoring the factory calibration Comparing the calibration with other PAR sensorsEnvironmental and moisture protection SunScan probe and Beam Fraction SensorLAI theory Ingredients of the LAI computation methodMajor assumptions Derivation of Wood’s SunScan canopy analysis equationsTheory versus reality Campbells Ellipsoidal LAD equations Beers law for canopy absorptionTransmission of Diffuse Light Transmission fraction τ Is given by I/I0 Modelling the canopy transmission Diffuse light transmission cosine corrected sensorDetail Diffuse light cosine response sensor Functions used to model canopy transmissionAccuracy of LAI calculations Diffuse light hemispherical response sensorModelling incomplete PAR absorption and scattering Exp 0.1 . x . atan 0.9 Atan L Q SpherCalculating zenith angles Scientific referencesSummary Jones, Hamlyn G Plants and Microclimate second edition. CUP Checking the batteries Maintenance and repairTechnical Reference section SunScan probe batteriesChecking the desiccant Checking the PAR calibration Re-setting the factory calibrationFactory calibration method Psion Workabout TroubleshootingProblems running the SunData application While running SunDataInsufficient power to write data reported Technical Support Beam Fraction Sensor type BF1 SpecificationsSunScan Probe Type SS1 Data Collection Terminal type DCT1 Psion WorkaboutSpares Kit type SPS1 Carrying Case type SCC1Telescopic Tripod type BFT1 Logging CablesPAR Performance Spectral responseCosine responses of probe and BFS SunScan system cosine responseAppendices Logging the probe as a Linear Quantum SensorLogging the Beam Fraction sensor Workabout SunData s/w Upgrading the SunScan systemSunData PC s/w Revision HistoryPsiWin File transfer between Workabout and PCChoice of different programs Workabout Remote LinkExample using Slink Slink and RcomDrives on the PC are referred to as REMA, Remc REM = remote Example using Rcom Documentation of Rcom and SlinkSending a file to a Communication program Using the Workabout Comms applicationAlternative file transfer mechanisms Sending a file to a serial printerGlossary Page Index AccuracyIndex Field use 39, 46, 48, 50, 51, 58

SS1-UM-1.05 specifications

Delta Electronics has long been recognized for its innovative solutions in power and thermal management technologies. One of its notable products is the SS1-UM-1.05, a compact and efficient power supply module designed to meet the needs of a variety of applications, from industrial automation to telecommunications.

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Overall, the Delta SS1-UM-1.05 power supply module is an exemplary solution for those seeking a reliable, efficient, and compact power source. Its advanced features and technologies make it an indispensable component in modern electronic systems.
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