sws: Shortwave Spectroradiometer

The shortwave spectroradiometer (SWS) measures the absolute visible and near-infrared spectral radiance (units of watts per square meter per nanometer per steradian) of the zenith directly above the instrument.

The SWS is a moderate-resolution sensor comprised of two Zeiss spectroradiometers (MMS 1 NIR enhanced and NIR-PGS 2.2) for visible and near-infrared detection in the wavelength range 350-2170 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 has 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. At the Southern Great Plains site, the SWS is located in a darkroom within the optical trailer to permit calibrations to be conducted without moving the instrument. Calibrations are performed on schedule using the ARM 12″ integrating sphere.

SWS measurements can be used to:

1. Retrieve cloud optical depth, particle size, and water path.
2. Test the cloud optical depth retrieval for overcast and broken cloud fields.
3. Validate/compare with SGP surface remote sensors and future cloud IOP campaigns.
4. Perform multivariate analysis to derive information content in hyper-spectral data sets and improve cloud retrieval algorithm development.
5. Compare with radiative transfer models for testing and validating retrieval procedures.



  • Fixed
  • AMF1
  • AMF2
  • AMF3

Active Instrument Locations

Facility Name Instrument Start Date
Central Facility, Lamont, OK 1989-12-31
Graciosa Island, Azores, Portugal 2006-04-30


Goss HB, KS Dorsey, CB Ireland, MR Wasem, RA Stafford, and R Jundt. 2020. 2019 Atmospheric Radiation Measurement (ARM) Annual Report. Ed. by Kathryn Dorsey, ARM user facility. DOE/SC-ARM-19-032.


Yang W, A Marshak, and G Wen. 2019. "Cloud edge properties measured by the ARM shortwave spectrometer over ocean and land." Journal of Geophysical Research: Atmospheres, 124(15), doi: 10.1029/2019JD030622.
Research Highlight


Wilson A, R Scott, M Cadeddu, V Ghate, and D Lubin. 2018. "Cloud Optical Properties over West Antarctica from Shortwave Spectroradiometer Measurements during AWARE." Journal of Geophysical Research: Atmospheres, 123(17), 10.1029/2018JD028347.


Fang M, BA Albrecht, VP Ghate, and P Kollias. 2013. "Turbulence in continental stratocumulus, Part II: Eddy dissipation rates and large-eddy coherent structures." Boundary-Layer Meteorology, 150(3), 10.1007/s10546-013-9872-4.

McBride P, A Marshak, Y Knyazkhin, J Chiu, and W Wiscombe. 2013. What Can Be Learned from ARM Shortwave Hyperspectral Observations? Presented at 4th Atmospheric System Research (ASR) Science Team Meeting. Potomac, MD.


Chiu JC, A Marshak, Y Knyazikhin, W Wiscombe, T Varnai, and H Wang. 2011. 3D Effects on Spectrally Invariant Behavior Near Cloud Edges: Implications for Retrieving Aerosol and Cloud Properties in These Challenging Regions. Presented at 2nd Atmospheric System Research (ASR) Science Team Meeting. San Antonio, TX.


Chiu JC, A Marshak, Y Knyazikhin, and WJ Wiscombe. 2010. "Spectrally-invariant behavior of zenith radiance around cloud edges simulated by radiative transfer." Atmospheric Chemistry and Physics, 10(22), 10.5194/acp-10-11295-2010.

Chiu JC, CH Huang, A Marshak, I Slutsker, DM Giles, BN Holben, Y Knyazikhin, and WJ Wiscombe. 2010. "Cloud optical depth retrievals from the Aerosol Robotic Network (AERONET) cloud mode observations." Journal of Geophysical Research – Atmospheres, 115(D14), D14202, 10.1029/2009jd013121.

Voyles JW. 2010. ARM Climate Research Facility Instrumentation Status and Information. DOE ARM Climate Research Facility. DOE/SC-ARM-10-006.4.

Flynn C, J Barnard, P Disterhoft, D Hopkins, P Kiedron, A Mendoza, J Michalsky, D Nelson, R Norheim, and J Schmelzer. 2010. New Shortwave Array Spectrometers for the ARM Climate Research Facility. Presented at Atmospheric System Research (ASR) Science Team Meeting.

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