SWS - WMO
Contents
1. DOE SC ARM TR 062 Shortwave Spectroradiometer SWS Handbook May 2007 Peter Pilewskie John Pommier Work supported by the U S Department of Energy Office of Science Office of Biological and Environmental Research NYA NFB WN KF May 2007 DOE SC ARM TR 062 Contents Gia Stee OVEN oy ROE NC ee ee RRO ET eet A 1 OAC a eee a Ras eh eas ete A ee Bees 2 Deployment Locations and FSO yssen ae a N a a 2 Near Rea Time Data PO a tcc Soi a eect eee ete tein eset 2 Data Description and Ex amples css csniescscuivsce da vaiz bse ctevalates alesis a a venidaueueeheslda dentate dst 3 Dba Ou aC y rasta te aa teaches E eset ted Gia atant seas ia ed eae eens auc 5 IAS GRUNT aL D CAIN Sse eshte hee tia oe Nee aa teeta oct ie aS aad Uh ec acne tence te E E A 6 Figures SWS and Monitor in thes DarktOOnn 333 aise ieee ie etic aia cee ee teenie 1 Schematic for the Connection of the SWS ccccccscssceccececcccsccecececcscersscecsscecsscecencecensscencsceces 7 il May 2007 DOE SC ARM TR 062 1 General Overview The Shortwave Spectroradiometer SWS measures the absolute visible and near infrared spectral radiance units of watts per meter square per nanometer per steradian of the zenith directly above the instrument The SWS is a moderate resolution sensor comprised of two Zeiss spectrometers MMS 1 NIR enhanced and NIR PGS 2 2 for visible and near infrared detection in the wavelength range 350 21702. nm The sampling frequency is 1 Hz The spectral resolution is 8 nm for the MMS 1 NIR and 12 nm for the NIR PGS 2 2 The light collector is a narrow field of view 1 4 collimator at the front end of a high grade custom made fiber optic bundle The SWS does daily daytime measurements The SWS is located in a darkroom constructed by Southern Great Plains SGP site personnel within the optical trailer to permit calibrations to be conducted without the necessity of moving the instrument to a different location Calibrations are performed at regularly scheduled times using the ARM 12 integrating sphere The SWS measurements can be used to a Retrieve cloud optical depth particle size and cloud water path b Test the cloud optical depth retrieval for overcast and broken cloud fields c Validation comparison with SGP surface remote sensors and future cloud intensive operational period campaigns d Multivariate analysis to derive information content in hyper spectral data sets and to improve cloud retrieval algorithm development e Compare with radiative transfer models for testing and validating retrieval procedures Figure 1 SWS and monitor in the darkroom Insert shows the light collector located at the top of the chimney Sites Facilities Southern Great Plains http www arm gov sites sgp stm Central Facility http www arm gov sites sgp central stm May 2007 DOE SC ARM TR 062 2 Contacts 2 1 Mentor Scott Kit
3. em Configuration and Measurement Methods The SWS is located in a dark room specially constructed by SGP site personnel in the south east corner of the Optical Trailer at the SGP Central Facility Placing the SWS in the dark room obviates the need to move the SWS to perform calibrations The light collector is attached to a high quality fiber optic which is passed through the port at the top of the optical trailer to the SWS May 2007 DOE SC ARM TR 062 _ Dome i i ee N aa N Collimator Shutter Shutt angie ___ Air Line Connection Whatman Purge Air System Fiber Optic Monitor SWS Spectrometers Computer Network Connection Figure 2 Schematic for the Connection of the SWS 7 1 3 Specifications Wavelengths Measured 256 channels in the Si 300 1100 nm 256 channels for the InGaAs 900 2200 nm Instrument Field of View The field of view of the instrument is 1 4 Sampling Interval Measurements are made at the rate of one per second during the day The SWS does not collect data between the hours of 0200 1100 UTC Integration Time The integration times vary during the course of the year but range from 75 100 ms for the Si detector and range approximately 150 250 ms for the InGaAs detector 7 2 Theory of Operation Photons incident on the collimator at the fore optics of the light collector travel through the multi optical fiber to the SWS where the fiber is then bifurcated with t
4. estions There are no FAQ s at the present time 6 Data Quality 6 1 Data Quality Health and Status Data Quality for the SWS will be available from the following web site maintained by DQ Hands http dq arm gov 6 2 Data Reviews by Instrument Mentor The monthly review by the mentor is available from the ARM web site http dg arm gov May 2007 DOE SC ARM TR 062 6 3 Data Assessments by Site Scientist Data Quality Office Not applicable to this instrument 6 4 Value Added Procedures and Quality Measurement Experiments To be determined 7 Instrument Details 7 1 Detailed Description 7 1 1 List of Components e Narrow field of view 1 4 collimator at the front end of a high grade ultra low OH fiber optic cable e Spectrometer Zeiss MMS 1 NIR enhanced 300 1100 nm flat field 366 1 mm grating Hamamatsu Si 256 element linear diode array Operating temperature regulated to 27 C by heater Zeiss NIR PGS 2 2 900 2200 nm 300 1 mm flat grating Hamamatsu InGaAs 256 element linear diode array Operating temperature regulated to 10 C by thermoelectric cooler e Automated shutter for dark current measurement e A 933 MHz Pentium III based computer PC104 format for automated data acquisition and control e A USB interface between the computer and the spectrometers e Operating system is Linux Fedora e Internal data storage on 1 GB compact flash card remote data collection via Ethernet interface 7 1 2 Syst
5. he light passing through entrance slits to either the Si grating or the InGaAs grating There the wavelength components are separated then imaged onto their respective diode array The array is then read by an electronic interface which passes the data to the computer via a USB connection Dark signals are obtained each hour at the same integration time that was used to measure the intensity by closing the shutter located at the base of the light collector May 2007 DOE SC ARM TR 062 7 3 Calibration 7 3 1 Theory The SWS is calibrated annually at the NASA Ames Airborne Science and Application Laboratory using a 30 integrating sphere The 30 sphere has been calibrated according to NIST standards The calibration from the 30 sphere is transferred annually to the ARM Souther Great Plains on site 12 integrating sphere The ARM 12 sphere is used weekly at the SGP site to monitor for any changes or degradation in the SWS response If necessary the calibration obtained with the ARM 12 integrating sphere is applied to adjust the primamry SWS response function obtained annually at NASA Ames 7 3 2 Procedures SGP site personnel built a darkroom to both house the SWS instrument and the ARM 12 integrating sphere used for weekly on site calibrations This allows the SWS to be calibrated without having to move the instrument to another part of the site To perform a calibration the light collector is lowered through the port in the cei
6. l voltage 4V OV o PC 104 12VDC input voltage 3 nominal voltage 4V D 6 PS2 5VDC nominal voltage 5V May 2007 DOE SC ARM TR 062 PS2 12VDC input voltage 3 nominal voltage 4V 5 1 4 Data Quality Flags Not available for this instrument at this time 5 1 5 Dimension Variables All SWS data files contain Universal Time Coordinates UTC and the date 5 2 Annotated Examples This figure is of sample spectra collected on 1 May 2006 during the period 1500 1900 UTC 10 00 14 00 local time The spectra are not averaged they are the 1 Hz spectrum collected at the indicated times select Spectra 1 May 2006 PRET 45 0UTC 16 0 UTC 17 0 UTC 18 0 UTC 19 0 UTC Zenith Radiance Wm nm sr Wavelength nm May 2007 DOE SC ARM TR 062 Time series over select wavelengths 1 May 2006 0 5 x 382 nm d 505 nm 762 nm A 941 am L 1050 nm 4199 nm 0 3 1602 nm 1648 nm t 2102 nm 0 2 Radiance Wm nm sr 0 1 The above plot is a radiance time series at nine SWS wavelengths The times are from 1330 2200 UTC The small gaps on the hour 1400 1500 etc are periods when the shutter was closed to obtain the dark signal There was clear sky until around 1530 UTC when first scattered clouds then a thicker 1900 UTC cloud mass moved over head 5 3 User Notes and Known Problems This section is not applicable to this instrument 5 4 Frequently Asked Qu
7. les and Expected Uncertainty Absolute spectral radiance of the zenith above the instrument in units of Wm nm tsr 5 1 1 1 Definition of Uncertainty Prior to deployment at the SGP the SWS was calibrated for absolute spectral power at the Airborne Science and Technology Laboratory at NASA Ames Research Center using the 30 integrating sphere which has been calibrated according to NIST standards and a LabSphere 12 integrating sphere The 12 sphere is used at the SGP site to calibrate the SWS The absolute accuracy of the spectral radiance for the SWS relies upon the accuracy of the transfer standard from the 30 sphere to the 12 sphere The 30 sphere has an error over the spectral range 300 2200 nm of between 1 2 5 1 2 Secondary Underlying Variables This section is not applicable to this instrument 5 1 3 Diagnostic Variables These are variables that monitor the health of the SWS The first three are concerned with the temperature of the two spectrometers and the box in which they are encased while the latter variables monitor voltages and indicate if a critical component is failing Quantity Measured Si spectrometer Normal temperature 1s 27 C E l InGaAs spectrometer temperature Normal temperature is 10 C a Inside box temperature This temperature reflects the ambient PE temperature which should be around 22 C eso PC 104 SVDC nominal value 5V aa ia PC 104 12VDC input voltage 3 nomina
8. ling and placed in a holder opposite the 12 integrating sphere The holder is aligned with the central axis of the exit port on the 12 sphere to insure the light collector is situated in the identical location each time it is calibrated A dark signal is taken before each calibration Following the calibration the light collector is then returned through the port to the top of the Optical Trailer 7 3 3 History No history is available at this time 7 4 Operation and Maintenance 7 4 1 User Manual A user manual has been prepared and provided to the SGP site personnel An electronic version is available upon request from the mentor in either PDF or Postscript format 7 4 2 Routine and Corrective Maintenance Documentation Instrument preventative maintenance reports are can be accessed at the SGP http www ops sgp arm gov 7 4 3 Software Documentation Software documentation is found in the User Manual see 7 4 1 above 7 4 4 Additional Documentation None available for this instrument May 2007 DOE SC ARM TR 062 7 5 Glossary See the ARM Glossary http www arm gov about glossary stm 7 6 Acronyms See the ARM Acronyms and Abbreviations http www arm gov about acronyms stm
9. telman University of Colorado Department of Atmospheric and Oceanic Sciences Folsom Stadium Gate 7 Room 255 UCB 311 Boulder CO 80309 0311 303 492 4248 E mail alan kittelman colorado edu Patrick McBride Department of Atmospheric and Oceanic Sciences Duane Physics Rm D 335 UCB 311 University of Colorado Boulder CO 80309 0311 303 492 8653 E mail mcbridep colorado edu 2 2 Instrument Developer Warren Gore NASA Ames Research Center MS 245 4 Moffett Field CA 94035 650 604 5533 3 Deployment Locations and History Serial Property Date Date Number Number Location Installed Removed Status SGPC Aprl 2006 Data collected is available from the Atmospheric Radiation Measurement ARM Program s archive http www archive arm gov 4 Near Real Time Data Plots Will be available at the ARM web site Data plots and other data products http www arm gov data data_plots stm May 2007 DOE SC ARM TR 062 5 Data Description and Examples 5 1 Data File Contents The SWS data files are stored in both raw and calibrated files at the ARM archive File names follow the ARM naming convention for the raw data files as follows sgpswscf 00 yyyymmdd hhmmss dat Where yyyy year i e 2006 mm month dd day hh hour mm minutes and ss seconds The raw data files will be calibrated units of Wm nm sr and converted into netcdf format by ARM at the time of ingest 5 1 1 Primary Variab
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