The DOW radar facility has served the NSF community as part of the LAOF program since 2008. Prior to then, the DOWs operated as a de facto NSF-community resource, participating in many scientific and educational field programs not led by the DOW PI. The DOWs have been among the most widely used facilities, participating in over 30 field campaigns since VORTEX1. DOWs have been requested for several planned future field programs [e.g., PECAN (2015), SNOWIE (2015/2016), Victoria (2016), RELAMPAGO (2016) and OLYMPEX-NSF (2015)]. DOWs have been the most frequently requested and allocated LAOF facility for education and outreach, have deployed at 18 universities, and participated in extensive nationwide outreach tours impacting over 100,000 students.
The DOW facility consists of three mobile radars (DOW6, DOW7 and the Rapid-Scan DOW [RSDOW]), support vehicles outfitted as mobile mesonets, a mobile office and maintenance / repair van and an array of quickly-deployable weather stations (Pods) that can be carried at low cost in the support vehicles / mesonets (see image, below.)
Many important meteorological phenomena (such as tornadoes, hurricanes, microbursts, dust devils, etc.) occur infrequently and/or very near the ground. These are difficult to measure with traditional stationary meteorological radars, due to temporal and/or spatial limitations. Additionally, many interesting physical processes occur at sub-kilometer scales, but the ranges between the phenomena of interest and the stationary radars are almost always quite large. This results in finescale (sub-kilometer) structures being unresolvable due to beam spreading between stationary radars and the targets. Near-ground (<300 m AGL) structures are often undetectable due to the masking of the transmitted beam by topography and obstructions, vertical beam spreading, and earth curvature. Finally, these phenomena frequently occur on timescales of seconds to minutes and thus are sampled poorly by typical surveillance radar scanning strategies. Thus, there was a need for finescale observations of these phenomena in order to better understand the mechanisms involved in their formation and maintenance.
Inter-comparison of dual-polarization products between the S-Band WSR-88D (top) and the X-Band DOW6 (bottom) radars during the 31 May 2013 El Reno tornadic supercell at ~2319 UTC. Even though observing geometry and wavelength are different, excellent agreement exists between the DOW and 88D, but much finer-scale detail is evident in the DOW6 data. Solid (stippled) black lines are ρhv (ZDR) signatures. (Wurman et al. 2013 El Reno)
Reliable, high-quality, accurate and carefully navigated DOW data have been at the core of analyses of winter storms, convective initiation, hydrology, severe wind/damage relationships, orographic precipitation, hurricane boundary layer structure, tornado genesis and structure and other analyses. The DOW radars made the first 3D maps of tornado winds and debris, the first maps of multiple vortex structure in tornadoes, the first maps of anticyclonic tornadoes; discovered hurricane boundary layer rolls, made the first observations of secondary rear flank downdrafts, mapped mesocyclone circulations in lake effect snowbands, observed how misocyclones along boundaries affected convective initiation, obtained the only comparisons of radar-measured winds, in-situ winds, and damage in tornadoes.
The DOW Facility provides the only:
• Three-radar, fast-scan, narrow-beam, multiple-Doppler network
• Narrow-beam, (0.8-0.9 degree) rapid-scan capability
• Dual-frequency dual-polarization capability for simultaneous LDR, ZDR, Phi-DP, Rho-HV
• Dual-frequency dual-polarization for 2x faster ZDR, Rho-HV, Phi-DP
• Truly mobile (while actually moving) multiple-Doppler capability
• Integrated Radar, Mobile Mesonet, Deployable Pod capability
• Bistatic-network-ready mobile radars.
DOW6 and DOW7 have the maximum transmit power of any mobile X-band weather radar, employing dual 250 kW transmitters, for maximum sensitivity at the greatest range. High gain antennas with 0.9-degree beam widths provide maximum practical sensitivity and minimum beam width. Quick scanning capability, now at 50 degrees/second with future improvements planned, allows for 7s 360-sweeps and 4-5 s sectors.
DOW6 and DOW7 employ a unique dual-frequency, dual-polarization design capable of executing two unique data collection modes: fast-45, and LDR+45. In fast-45 mode, both transmitters, separated by 150 MHz, transmit at 45-degree polarization and H and V are received separately. High quality dual-polarization data can be collected at much faster speed since the samples returned from each transmitted frequency are fully independent. Fast dual-polarization scanning permits the rapid evolution of mesoscale cloud/precipitation microphysical structures to be studied. In LDR+45 mode, one transmit frequency is transmitted at H polarization only, with the other frequency at 45 degrees, and H and V are received. LDR is measured at the one frequency, while the 45-degree products of ZDR, Rho-HV, and Phi-DP can be measured using the 2nd frequency. The LDR frequency also provides Z,V, etc. DOWs employ PENTEK signal processing cards and an NCAR-developed signal processing software suite, which is compatible with NCAR-managed LAOF radars (Dixon et al. 2013). The TITAN and Hawkeye suite are used to calculate moments (e.g. V, ZDR), and for archiving (redundant on internal RAID and external USB3 for easy transfer for quick look), display, and real-time remote transfer.
|Transmitters||2x 250 kW magnetron|
|Pulse length||0.15-1.0 us|
|Scan rate||50 deg/sec|
|Products||LDR, ZDR, Rho-HV, V, Z, SW, NCP, etc. (Combined or separate by frequency, Raw IQ for max post-proc flexibility|
|Beam Width||0.9 deg|
|Gate length||15-600 m|