Atmospheric Radiation Measurement Climate Research Facility US Department of Energy

radfluxanal > Radiative Flux AnalysisVAP Type(s) > Baseline • Guest

sgpradflux1longc1-c2_opplot1-20140509-0000001The Radiative Flux Analysis VAP estimates clear-sky shortwave (SW) and longwave (LW) surface fluxes. Clear-sky detection and fitting techniques (Long and Ackerman 2000; Long and Turner 2008) are used to identify clear-sky periods from broadband radiometers and empirically fit functions.

The SW clear-sky detection technique uses hemispheric, broadband total- and diffuse-shortwave irradiance measurements to identify clear-sky periods using the known characteristics of typical clear-sky irradiance time series. An empirical fitting technique is used to estimate clear-sky shortwave fluxes (Long and Ackerman 2000). The LW clear-sky flux estimation technique uses the SW identified daylight clear-sky data to refine the properties needed for 24-hour-a-day identification of LW clear-sky periods. Once these refined parameters and limits are determined, then additional clear-sky periods are identified and an empirical fitting technique is again used to continuously estimate clear-sky longwave fluxes.

The VAP also uses a technique (Long et al. 2006) to infer average fractional sky cover from SW measurements for solar elevation angles 10° or greater, with an accuracy of about 10% compared to a total sky imager (TSI). Fractional sky cover is also estimated from LW fluxes using a method similar to that described in Durr and Philipona (2004). Other retrieved parameters include cloud optical depth for overcast skies (Barnard et al. 2008), cloud transmissivity, and cloud radiating temperature.


  • Fixed
  • AMF1
  • AMF2
  • AMF3

Active Locations

Facility Name Start Date
Central Facility, Barrow AK 1998-05-28
Maple City, KS (Extended) 2011-09-04


Riihimaki L, X Li, Z Hou, and L Berg. 2021. "Improving prediction of surface solar irradiance variability by integrating observed cloud characteristics and machine learning." Solar Energy, 225, 10.1016/j.solener.2021.07.047.


Riihimaki L, C Flynn, and A McComiskey. 2020. ARM Shortwave Spectral Radiometry Strategy Review Report. Ed. by Robert Stafford, ARM user facility. DOE/SC-ARM-20-003.


Riihimaki LD, KL Gaustad, and CN Long. 2019. Radiative Flux Analysis (RADFLUXANAL) Value-Added Product: Retrieval of Clear-Sky Broadband Radiative Fluxes and Other Derived Values. Ed. by Robert Stafford, ARM user facility. DOE/SC-ARM-TR-228.


Zhang C, S Xie, S Klein, H Ma, S Tang, K Van Weverberg, C Morcrette, and J Petch. 2018. "CAUSES: Diagnosis of the Summertime Warm Bias in CMIP5 Climate Models at the ARM Southern Great Plains Site." Journal of Geophysical Research: Atmospheres, 123(6), doi:10.1002/2017JD027200.
Research Highlight

Van Weverberg K, C Morcrette, J Petch, S Klein, H Ma, C Zhang, S Xie, Q Tang, W Gustafson Jr, Y Qian, L Berg, Y Liu, M Huang, M Ahlgrimm, R Forbes, E Bazile, R Roehrig, J Cole, W Merryfield, W Lee, F Cheruy, L Mellul, Y Wang, K Johnson, and M Thieman. 2018. "CAUSES: Attribution of Surface Radiation Biases in NWP and Climate Models near the U.S. Southern Great Plains." Journal of Geophysical Research: Atmospheres, 123(7), 10.1002/2017JD027188.
Research Highlight

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Damao Zhang
Pacific Northwest National Laboratory

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