xsapr: X-Band Scanning ARM Precipitation Radar

The X-band scanning ARM precipitation radar (X-SAPR) is an X-band dual-polarization Doppler weather radar. The X-SAPR operates in a simultaneous transmit and receive (STAR) mode, meaning that the transmit signal is split so that power is transmitted on both horizontal and vertical polarizations at the same time. The X-SAPR transmitter is a 200 kW (peak power) magnetron. The receiver is based upon the Vaisala RVP-900 and runs Vaisala’s IRIS software.

In addition to the first three Doppler moments (reflectivity, radial velocity, and spectra width), the X-SAPR also provides differential reflectivity, correlation coefficient, and specific differential phases. The dual-polarization variables enable estimates of rainfall rates and identification of precipitation types. At the Southern Great Plains site, three X-SAPRs surround the Central Facility, allowing the use of multi-Doppler velocity retrievals to estimate wind fields.



  • Fixed
  • AMF1
  • AMF2
  • AMF3

Related Publications


Wen G, M Oue, A Protat, J Verlinde, and H Xiao. 2016. "Ice particle type identification for shallow Arctic mixed-phase clouds using X-band polarimetric radar." Atmospheric Research, 182, 10.1016/j.atmosres.2016.07.015.

Kalesse H, G DeBoer, A Solomon, M Oue, M Ahlgrimm, D Zhang, M Shupe, E Luke, and A Protat. 2016. "Understanding Rapid Changes in Phase Partitioning between Cloud Liquid and Ice in Stratiform Mixed-Phase Clouds: An Arctic Case Study." Monthly Weather Review, 144(12), 10.1175/mwr-d-16-0155.1. ONLINE.

Helmus JJ and SM Collis. 2016. "The Python ARM Radar Toolkit (Py-ART), a Library for Working with Weather Radar Data in the Python Programming Language." Journal of Open Research Software, 4(1), 10.5334/jors.119.

van Lier-Walqui M, AM Fridlind, AS Ackerman, S Collis, J Helmus, DR MacGorman, K North, P Kollias, and DJ Posselt. 2016. "On polarimetric radar signatures of deep convection for model evaluation: Columns of specific differential phase observed during MC3E." Monthly Weather Review, 144(2), 10.1175/mwr-d-15-0100.1. ONLINE.

Wang Y, B Geerts, and Y Chen. 2016. "Vertical structure of boundary layer convection during cold-air outbreaks at Barrow, Alaska." Journal of Geophysical Research: Atmospheres, 121(1), 10.1002/2015jd023506.


Mechem DB, SE Giangrande, CS Wittman, P Borque, T Toto, and P Kollias. 2015. "Insights from modeling and observational evaluation of a precipitating continental cumulus event observed during the Midlatitude Continental Convective Clouds Experiment field campaign." Journal of Geophysical Research: Atmospheres, 120(5), 10.1002/2014jd022255.


Giangrande SE, S Collis, A Theisen, and A Tokay. 2014. "Precipitation Estimation from the ARM Distributed Radar Network during the MC3E Campaign." Journal of Applied Meteorology and Climatology, 53(9), 10.1175/jamc-d-13-0321.1.


Giangrande SE, R McGraw, and L Lei. 2013. "An Application of Linear Programming to Polarimetric Radar Differential Phase Processing." Journal of Atmospheric and Oceanic Technology, 30(8), 10.1175/jtech-d-12-00147.1.

Mather JH and JW Voyles. 2013. "The Arm Climate Research Facility: A Review of Structure and Capabilities." Bulletin of the American Meteorological Society, 94(3), 10.1175/bams-d-11-00218.1.

Fridlind A, D Wu, T Matsui, W Tao, A Ackerman, K North, and S Collis. 2013. Combined Analysis of Observed and Simulated Convective and Stratiform Rain Structures, Convective Dynamics, and Microwave Radiances on May 20th During MC3E. Presented at 4th Atmospheric System Research (ASR) Science Team Meeting. Potomac, MD.

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