Editing NEXRAD (section)

==Enhancements==

===Super resolution===
Deployed from March to August 2008 with all level II data,<ref>{{cite web|title=RPG SW BUILD 10.0 – INCLUDES REPORTING FOR SW 41 RDA|url=http://www.roc.noaa.gov/ssb/cm/csw_notes/Completion.aspx?ID=2689|website=Radar Operations Center|publisher=National Oceanic and Atmospheric Administration}}</ref> the Super Resolution upgrade permitted the capability of the radar to produce much higher resolution data. Under legacy resolution, the WSR-88D provides reflectivity data at {{convert|1|km|abbr=on}} by 1 degree to {{convert|460|km|abbr=on}} range, and velocity data at {{convert|0.25|km|mi|abbr=on}} by 1 degree to a range of {{convert|230|km|mi|abbr=on}}. Super Resolution provides reflectivity data with a sample size of {{convert|0.25|km|mi|abbr=on}} by 0.5 degree, and increase the range of Doppler velocity data to {{convert|300|km|mi|abbr=on}}. Initially, the increased resolution is only available in the lower scan elevations. Super resolution makes a compromise of slightly decreased [[noise reduction]] for a large gain in resolution.<ref>{{cite web|title=Build10FAQ<!-- Bot generated title -->|url=http://www.roc.noaa.gov/NWS_Level_2/BuildInfo/Build10FAQ.aspx|website=Radar Operations Center|publisher=National Oceanic and Atmospheric Administration|url-status=dead|archive-url=https://web.archive.org/web/20080704071034/http://www.roc.noaa.gov/NWS_Level_2/BuildInfo/Build10FAQ.aspx|archive-date=2008-07-04}}</ref>

The improvement in [[azimuthal]] resolution increases the range at which tornadic mesoscale rotations can be detected. This allows for faster lead time on warnings and extends the useful range of the radar. The increased resolution (in both azimuth and range) increases the detail of such rotations, giving a more accurate representation of the storm. Along with providing better detail of detected precipitation and other mesoscale features, Super Resolution also provides additional detail to aid in other severe storm analysis. Super Resolution extends the range of velocity data and provides it faster than before, also allowing for faster lead time on potential tornado detection and subsequent warnings.<ref>{{cite web|title=NEXRAD Product Improvement – Current Status of WSR-88D Open Radar Data Acquisition (ORDA) Program and Plans For The Future|url=http://ams.confex.com/ams/pdfpapers/85593.pdf|publisher=[[American Meteorological Society]]}}</ref>

===Dual polarization===
{{See also|Joint Polarization Experiment}}

{| align="right"
| [[File:Non-Polarimetric Radar.gif|thumb|Non-Polarimetric Radar]]
| [[File:Polarimetric Radar.gif|thumb|Polarimetric Radar]]
|}
WSR-88D sites across the nation have been upgraded to [[Weather radar#Polarization|polarimetric radar]], which adds a vertical [[Polarization (waves)|polarization]] to the traditional horizontally polarized radar waves, in order to more accurately discern what is reflecting the signal. This so-called [[dual polarization]] allows the radar to distinguish between rain, hail, and snow, something the horizontally polarized radars cannot accurately do. Early trials showed that rain, [[ice pellets]], snow, hail, birds, insects, and [[ground clutter]] all have different signatures with dual polarization, which could mark a significant improvement in forecasting [[winter storm]]s and severe thunderstorms.<ref>{{cite web|title=Polarimetric Radar Page<!-- Bot generated title -->|url=http://www.cimms.ou.edu/~schuur/radar.html|publisher=[[University of Oklahoma]]|access-date=2003-09-09|archive-date=2018-08-22|archive-url=https://web.archive.org/web/20180822213754/http://www.cimms.ou.edu/~schuur/radar.html|url-status=dead}}</ref> The deployment of the dual polarization capability (Build 12) to NEXRAD sites began in 2010 and was completed by the summer of 2013. The radar at [[Vance Air Force Base]] in [[Enid, Oklahoma]] was the first operational WSR-88D modified to utilize dual polarization technology. The modified radar went into operation on March 3, 2011.<ref>{{cite web|title=Technical Implementation Notice 10–22 Amended|url=http://www.roc.noaa.gov/WSR88D/PublicDocs/DualPol/DualPol_030711.pdf|website=Radar Operations Center|publisher=National Oceanic and Atmospheric Administration|date=March 7, 2011}}</ref>

=== AVSET ===
When the NEXRAD system was initially implemented, the radar automatically scanned all scan angles in a Volume Coverage Pattern, even if the highest scan angles were free of precipitation. As a result, in many cases when severe weather was farther from the radar site, forecasters could not provide as timely severe weather warnings as possible. The Automated Volume Scan Evaluation and Termination (AVSET) algorithm<ref>{{Cite web|url=https://www.roc.noaa.gov/wsr88d/PublicDocs/NewTechnology/Automated_VCP_Evaluation_and_Termination_Update_2012.pdf|title=Automated Volume Scan Evaluation and Termination (AVSET)|website=National Weather Service|access-date=March 7, 2017}}</ref> helps solve this problem by immediately ending the volume scan when precipitation returns at higher scan angles drop below a set threshold (around 20 dBZ). This can often allow for more volume scans per hour, improving severe weather detection without the need for hardware upgrades<ref>{{cite web|url=http://thevane.gawker.com/this-one-little-programming-tweak-will-save-thousands-o-1592764166 |title=This One Little Programming Tweak Will Save Thousands of Lives |date=June 18, 2014 |website=The Vane |publisher=[[Gawker|Gawker Media, LLC]] |author=Dennis Mersereau |access-date=June 18, 2014 |url-status=dead |archive-url=https://web.archive.org/web/20140619184002/http://thevane.gawker.com/this-one-little-programming-tweak-will-save-thousands-o-1592764166 |archive-date=June 19, 2014 }}</ref><ref>{{Cite web|url=https://www.roc.noaa.gov/wsr88d/Images/NewTechnology/20111116_rah_avset_experience.pdf|title=Use of AVSET at RAH during the 16 November 2011 Tornado Event|website=National Weather Service|access-date=March 7, 2017}}</ref> AVSET was initially deployed in RPG build 12.3, in Fall of 2011.

===SAILS and MESO-SAILS===
{{Main|MESO-SAILS}}
One of the primary weaknesses of the WSR-88D radar system was the lack of frequency of base (0.5 degree) scans, especially during severe weather. Forecasters, and TV viewers at home, often had access to images that were four or five minutes old, and therefore had inaccurate information. TV viewers at home could be lulled into a false sense of security that a tornado was farther away from them than it really was, endangering residents in the storm's path. The Supplemental Adaptive Intra-Volume Low-Level Scan (SAILS) technique, deployed with Build 14 in the first half of 2014, allows operators the option to run an additional base scan during the middle of a typical volume scan.<ref>{{Cite web|url=https://www.roc.noaa.gov/wsr88d/PublicDocs/NewTechnology/Supplemental_Adaptive_Intra_Volume_Low_Level_Scan_Description_Document_Final.pdf|title=Supplemental Adaptive Intra-Volume Low-Level Scan (SAILS)|date=October 30, 2012|website=National Weather Service|access-date=March 7, 2017}}</ref> With one SAILS cut active on VCP 212, base scans occur about once every two and a half minutes, with more frequent updates if AVSET terminates the volume scan early.

Multiple Elevation Scan Option for Supplemental Adaptive Intra-Volume Low-Level Scan (MESO-SAILS) is an enhancement to SAILS, which allows the radar operator to run one, two or three additional base scans during the course of a volume scan, per the operators request.<ref name=":0" /> During June 2013, the Radar Operations Center first tested SAILSx2, which adds two additional low-level scans per volume. It was executed for approximately 4.5 hours and during the testing, an Electronics Technician observed the pedestal/antenna assembly's behavior. No excessive wear was noted. Two days later, SAILSx3 was executed, which added 3 additional low-level scans to a volume. During this 1.5 hour test of SAILSx3, a ROC Radar Hardware Engineer accompanied the ROC Electronics Technician to observe the antenna/pedestal assembly. Again, no excessive wear was noted.<ref>{{Cite web|url=https://www.roc.noaa.gov/wsr88d/PublicDocs/NewTechnology/MESO-SAILS_Description_Briefing_Jan_2014.pdf|title=Multiple Elevation Scan Option for SAILS (MESO-SAILS)|last=Chrisman|first=Joe|date=January 2014|website=National Weather Service|access-date=February 27, 2017}}</ref> MESO-SAILS was deployed with Build 16.1, in spring of 2016.

=== MRLE ===
'''Mid-Volume Rescan of Low-Level Elevations''' (colloquially known as '''MRLE''') is a dynamic scanning option for the [[WSR-88D]] derived from [[MESO-SAILS]],<ref>{{cite web|url=https://www.roc.noaa.gov/wsr88d/PublicDocs/NewTechnology/Supplemental_Adaptive_Intra_Volume_Low_Level_Scan_Description_Document_Final.pdf |title=Archived copy |access-date=2017-03-07 |url-status=dead |archive-url=https://web.archive.org/web/20170119232850/https://www.roc.noaa.gov/wsr88d/PublicDocs/NewTechnology/Supplemental_Adaptive_Intra_Volume_Low_Level_Scan_Description_Document_Final.pdf |archive-date=2017-01-19 }}</ref> a separate scanning option implemented in NEXRAD RPG 14.0, in the Spring of 2014.<ref>{{cite web|url=https://www.roc.noaa.gov/WSR88d/PublicDocs/NewTechnology/DQ_QLCS_MRLE_June_2016.pdf |title=Archived copy |access-date=2017-04-27 |url-status=dead |archive-url=https://web.archive.org/web/20170427030703/https://www.roc.noaa.gov/wsr88d/PublicDocs/NewTechnology/DQ_QLCS_MRLE_June_2016.pdf |archive-date=2017-04-27 }}</ref>

During [[quasi-linear convective system]]s (QLCS), colloquially known as squall lines, the detection of [[mesovortices]], which generate at 4,000 to 8,000 feet above ground level,<ref>{{cite web|url=http://www.spc.noaa.gov/misc/AbtDerechos/papers/Atkins2_2009.pdf|title=Bow Echo Mesovortices. Part II: Their Genesis|last1=Atkins|first1= N. T.|last2= Laurent|first2= M. St|date=May 2009|website=Monthly Weather Review|access-date=February 18, 2017}}</ref> is not always possible with SAILS cuts, as the base 0.5 degree scan travels below the formation of mesovortices at closer distances to the radar. '''MRLE''' consecutively scans either the two, three or four lowest scan angles during the middle of a typical volume scan, allowing more frequent surveillance of mesovortex formation during QLCS events.<ref>{{Cite web|url=https://www.roc.noaa.gov/wsr88d/PublicDocs/NewTechnology/MRLE_General_Description_Doc_May_2016_V01.pdf|title=General Description Document Mid-Volume Rescan of Low-Level Elevations (MRLE)|date=May 12, 2016|website=National Weather Service|access-date=March 7, 2017}}</ref> MRLE will be deployed on a non-operational basis in RPG 18.0 in spring of 2018, with possible operational deployment with RPG 19.0, if proven useful or of importance.

Deployment was anticipated by the [[Radar Operations Center]] to commence in October 2017, along with the RPG 18.0 build, on a non-operational basis. The scanning option will only be available for use with Volume Coverage Patterns 21, 12, 212, and additionally 215.<ref>{{cite web|url=https://www.roc.noaa.gov/WSR88d/NewRadarTechnology/NewTechDefault.aspx |title=New Radar Technology |website=Roc.noaa.gov |access-date=2017-04-27}}</ref> If proven to be significant in terms of warning dissemination, MRLE will deploy operationally nationwide with RPG 18.0, planned for 2018.

====Concept====
[[File:QLCS.png|thumb|Spin-up tornado associated with a [[quasi-linear convective system|QLCS]] as seen from a nearby [[Doppler weather radar]], which often goes unseen.]]
The concept of MRLE derives from the need of more frequent low-level scans during [[quasi-linear convective system]]s (QLCSs). During QLCSs, it is not uncommon for brief and otherwise un-noticeable [[mesovortices]] to spawn at points along the line.<ref>{{cite web|url=http://www.spc.noaa.gov/misc/AbtDerechos/papers/Atkins2_2009.pdf |title=mwr2650 1514..1532 |website=Spc.noaa.gov |access-date=2017-04-27}}</ref> Due to untimely radar data and time being taken to complete the entire volume, these vortices often spawn without warning or prior notice. With MRLE, the operator has the choice between 2 and 4 low-level scans. Unlike [[MESO-SAILS]], which scans at one angle and can only do up to 3 low-level scans per volume, MRLE scans at 4 possible angles, and can cut into a volume up to 4 times, depending on the operators choice. The angles are as follows, alongside their respective scan frequencies:

*MRLEx2 = 0.5° and 0.9° elevations
*MRLEx3 = 0.5°, 0.9° and 1.3° elevations
*MRLEx4 = 0.5°, 0.9°, 1.3° and 1.8° elevations<ref>{{cite web|url=https://www.roc.noaa.gov/WSR88d/PublicDocs/NewTechnology/MRLE_General_Description_Doc_May_2016_V01.pdf |title=Archived copy |access-date=2017-03-07 |url-status=dead |archive-url=https://web.archive.org/web/20170125213140/https://www.roc.noaa.gov/wsr88d/PublicDocs/NewTechnology/MRLE_General_Description_Doc_May_2016_V01.pdf |archive-date=2017-01-25 }}</ref>
The operator can not use MESO-SAILS alongside MRLE simultaneously. If one is selected while the other is active, the NEXRAD algorithms will automatically set the other "off".

=== Service Life Extension Program ===
Started on March 13, 2013, the Service Life Extension Program (SLEP), is an extensive effort to keep and maintain the current NEXRAD network in working order for as long as possible. These improvements include signal processor upgrades, pedestal upgrades, transmitter upgrades, and shelter upgrades. The program is anticipated to be finished by 2022, which coincides with the beginnings of a nationwide implementation of multi-function phased array radars (see below).<ref>{{cite web|url=https://www.roc.noaa.gov/WSR88D/SLEP/SLEP.aspx|title=Service Life Extension Program (SLEP)|website=www.roc.noaa.gov|access-date=13 April 2018}}</ref>