1. ITU/WMO Seminar “Use of Radio Spectrum for Meteorology: Weather, Water and Climate Monitoring and Prediction” Session 6: Meteorological Radars Weather Radars
Presented By:
R.P Leck
Earth Resource Technologies Inc.
For : NOAA-National Weather Service
September 2009

2. Meteorological Radars Agenda
Weather Radars
Frequency Bands
System Overview
Operations
Data Utilization
Impact of Interference
Relevant ITU Documents
Looking Forward
Conclusions

3. Weather Radars Frequency Bands Weather Radar Frequency Bands
Frequency band (MHz)
Band Name
2 700-2 900
S-Band
5 250-5 725
(Mainly 5 600-5 650 MHz)
C-Band
9 300-9 500
X-Band
S band radars operate on a wavelength of 8-15 cm and a frequency of 2-4 GHz. Because of the wavelength and frequency, S band radars are not easily attenuated. This makes them useful for near and far range weather observation. The National Weather Service (NWS) uses S band radars on a wavelength of just over 10 cm. The drawback to this band of radar is that it requires a large antenna dish and a large motor to power it. It is not uncommon for a S band dish to exceed 25 feet in size.
C band radars operate on a wavelength of 4-8 cm and a frequency of 4-8 GHz. Because of the wavelength and frequency, the dish size does not need to be very large. This makes C band radars affordable for TV stations. The signal is more easily attenuated, so this type of radar is best used for short range weather observation. The frequency allows C band radars to create a smaller beam width using a smaller dish. C band radars also do not require as much power as an S band radar. The NWS transmits at 750,000 watts of power for their S band, where as a private TV stations typically transmit 270,000 watts of power with their C band radar. There are some C-bands with 1 MW of transmit power.
X band radars operate on a wavelength of cm and a frequency of 8-12 GHz. Because of the smaller wavelength, the X band radar is more sensitive and can detect smaller particles. These radars are used for studies on cloud development because they can detect the tiny water particles and also used to detect light precipitation such as snow. X band radars also attenuate very easily, so they are used for only very short range weather observation. Also, due to the small size of the radar, it can therefore be portable like the Doppler on Wheels. (DOW) Most major airplanes are equipped with an X band radar to pick up turbulence and other weather phenomenon. This band is also shared with some police speed radars and some space radars.

4. Weather Radars System Overview S-Band
Operate in the MHz Band
In the US, WSR-88Ds operate up to 3000 MHz
Typical peak transmitter power is ~750 kW
300 km Range
Best Severe Weather Performance
159 operational S-Band NEXRAD Radars form the backbone of the US Severe Weather Warning System
NEXRAD (Next-Generation Radar) is a network of 159 high-resolution Doppler weather radars operated by the National Weather Service, an agency of the National Oceanic and Atmospheric Administration (NOAA) within the United States Department of Commerce. Its technical name is WSR-88D, which stands for Weather Surveillance Radar, 1988, Doppler. The WSR-88D Doppler radar (NEXRAD) represents the backbone of the severe weather warning system in the United States for both the National Weather Service (NWS) and Department of Defense (DoD). There are a total of 159 NEXRAD sites in the U. S., including Alaska, Guam, Hawaii, and Puerto Rico. In the US some of the WSR-88D’s operate at 3000 MHz.
NEXRAD detects precipitation and atmospheric movement or wind. It returns data which when processed can be displayed in a mosaic map or individual site displays] which show patterns of precipitation and its movement. The radar system operates in two basic modes, selectable by the operator — a slow-scanning clear-air mode for analyzing air movements when there is little or no activity in the area, and a precipitation mode, with a faster scan for tracking active weather. NEXRAD has an increased emphasis on automation, including the use of algorithms and automated volume scans.

5. Weather Radars System Overview C-Band (Commercial)
Operates within the MHz Band (Primarily between MHz)
Typical transmitter power is ~270 kW
~200 km Range
C-Band System are widely deployed on a worldwide basis
Used by many TV Stations
C band radars operate with the MHZ Band. They are typically deployed with the MHZ range. Because of the wavelength and frequency, the dish size does not need to be very large. This makes C band radars affordable for TV stations. The signal is more easily attenuated, so this type of radar is best used for short range weather observation. The frequency allows C band radars to create a smaller beam width using a smaller dish.
C band radars do not typically require as much power as an S band radar. From an operational perspective, the actual transmitter power depends on range requirement. Most C Band system transmit at 270,000 watts of power but some transmit with as much as 1 MW. In comparison The NWS NEXRAD S Band radar transmits at 750,000 watts of power.

6. Weather Radars System Overview C-Band (Government)
FAA operates 45 Terminal Doppler Weather Radar (TDWR’s) systems at or near major airports in the US
Operates within the MHz Band
Typical transmitter power is ~270 kW
~90 km Range
Detects hazardous weather conditions such as windshear, microbursts and gust fronts, tornadic winds and heavy precipitation (inferring thunderstorms at an airport)
The Terminal Doppler Weather Radar (TDWR) is an advanced technology weather radar deployed near 45 of the larger airports in the U.S. The radars were developed and deployed by the Federal Aviation Administration (FAA) beginning in 1994, as a response to several disastrous jetliner crashes in the 1970s and 1980s caused by strong thunderstorm winds. The crashes occurred because of wind shear--a sudden change in wind speed and direction. Wind shear is common in thunderstorms, due to a downward rush of air called a microburst or downburst.
The TDWR was designed by the FAA to look for low altitude phenomena such as wind shifts over the runways, wind shear along the immediate approach and departure corridors, and downbursts. Therefore these radars are typically located close to major airports, and the scanning strategy is optimized to sample the atmosphere over its associated airport.
Terminal Doppler Weather Radar (TDWR) system detects hazardous weather conditions such as windshear, microbursts and gust fronts, tornadic winds, heavy precipitation (inferring thunderstorms at an airport).  This weather information is provided to air traffic controllers on displays at terminal facilities

7. Weather Radars System Overview X-Band
Operates within the MHz Band
Typical transmitter power is 100 W to 25 kW
~50 km Range
Element of Center for Collaborative Adaptive Sensing of the Atmosphere (CASA) network
Users of X-Band Weather Radars include:
TV stations
Military
Researchers
Small physical size
Low Cost compared to S or C Band Systems
X band radars operate on a wavelength of cm and a frequency of 8-12 GHz. Because of the smaller wavelength, the X band radar is more sensitive and can detect smaller particles. These radars are used for studies on cloud development because they can detect the tiny water particles and also used to detect light precipitation such as snow. X band radars also attenuate very easily, so they are used for only very short range weather observation. Also, due to the small size of the radar, it can therefore be portable like the Doppler on Wheels. (DOW) Most major airplanes are equipped with an X band radar to pick up turbulence and other weather phenomenon. This band is also shared with some police speed radars and some space radars.
NSSL is participating in an NSF-sponsored Engineering Research Center called the Center for Collaborative Adaptive Sensing of the Atmosphere (CASA) to explore sensing the lower atmosphere with a network of many short-wavelength (3cm) radars. These smaller and less expensive radars will be spaced much closer together than those in the current operational radar network to provide data in blind spots caused by terrain blockage and the curvature of the earth CASA will also employ a new observation methodology termed DCAS (Distributed Collaborative Adaptive Sensing), that will operate the network of radars collaboratively and adapt them to changing atmospheric conditions and the needs of various end users. DCAS benefits include: Significant reductions in tornado false-alarms, improved precipitation estimates for flood prediction, detection of humidity and temperature variables, an improved understanding of how winds carry chemical, radiological or biological hazards all of which will save lives and reduce property losses

8. Weather Radars Operations US NEXRAD Network
Started Service in June 1992
159 Network Sites selected to provide overlapping coverage
Super Resolution Upgrade Began in June 2008 increased Doppler Data Range to 300 km from 230 km
Provides Nationwide Reflectivity Mosaic
Generates multiples levels of data which include….
Level II data - meteorological base data quantities: reflectivity, mean radial velocity, and spectrum width.
41 meteorological analysis products known as Level III data are generated from the Level II Data.
The data are sent to the National Climatic Data Center (NCDC) for archiving and dissemination.
A detailed description of these products can be found at
NEXRAD data is also used in hydrology, ecology, and environmental studies.
NEXRAD
Nexrad (Next-Generation Radar) is a network of 159 high-resolution Doppler weather radars operated by the National Weather Service, an agency of the National Oceanic and Atmospheric Administration (NOAA) within the United States Department of Commerce. Its technical name is WSR-88D, which stands for Weather Surveillance Radar, 1988, Doppler. NEXRAD detects precipitation and atmospheric movement or wind. It returns data which when processed can be displayed in a mosaic map which shows patterns of precipitation and its movement.
Super resolution
In the process of implementation from March to June 2008, is the capability of the RDA to produce super resolution data. The WSR-88D provides reflectivity data at 1 km by 1 degree to 460 km range, and Doppler data at 0.25 km by 1 degree to a range of 230 km. Super Resolution will provides data with a sample size of 0.25 km by 0.5 degree, and increase the range of Doppler data to 300 km. Initially the increased resolution will only be available in the lower scan elevations. Super resolution makes a compromise of slightly decreased noise reduction for a large gain in resolution.[3]
To improve severe weather warning lead times, potential tornadic storms need to be identified as soon as possible. The improvement in beam width resolution increases the range at which small tornado parent circulation patterns (down to 4 km diameter) can be detected. Super-resolution also provides additional detail to aid in severe storm analysis. Extending the range of Doppler data and providing Doppler data earlier in the process of a volume scan provides velocity data more quickly than current scan techniques
Data
Level II data are the three meteorological base data quantities: reflectivity, mean radial velocity, and spectrum width. Data are collected and recorded in units of files which typically contain five, six, or ten minutes of base data depending on the volume coverage pattern. A data file consists of a 24 byte volume scan header record followed by numerous 2432 byte base data and message records.
There are a total of 41 Level-III products routinely available from NCDC. Most Level III products are available as digital images, color hard copy, gray scale hard copy or acetate overlay copies.
real-time product data: and real-time Level II data:

9. Weather Radars Operations 150 Weather Radars
European Network (OPERA – Operational Program for the Exchange of weather RAdar information)
150 Weather Radars
Supported Within the OPERA Network
Approximately 100 Doppler Radars
Dual-Polarization is becoming the operational standard.
The fundamental objective of OPERA is to provide a European platform wherein expertise on operationally-oriented weather radar issues is exchanged and holistic management procedures are optimized. With the establishment of its Data Hub, OPERA is now organized to support the application of radar data from the European Weather Radar Network. Another important objective of OPERA is to act to harmonize data and product exchange at the European level.
The OPERA programme (Operational Programme for the Exchange of weather Radar information, is the Weather Radar programme of EUMETNET, the Network of the European Meteorological Services (NMSs). The objective of OPERA is to harmonize and improve the operational exchange of weather radar information between national meteorological services. The third phase of the OPERA programme is a joint effort of 29 European countries, runs from 2007 till 2011, and is managed by KNMI. OPERA-3 is designed to firmly establish the Programme as the host of the European Weather Radar Network.

10. Weather Radars Operations Present and Future Frequency Band Needs
Band selection is a function of the trade offs between range reflectivity and cost which vary as a function of the physics of rain attenuation.
S-Band ( MHz) is well suited for detecting heavy rain at very long ranges. (Up to 300 km)
C-Band ( MHz) represents a good compromise between range and reflectivity and cost and can provided rain detection up to a range of 200 km
X-Band ( MHz) weather radars are…
More sensitive than S or C Band Radars Used for short range weather observations up to a range of 50 km

11. Weather Radars Operations Data Utilization – Base Products
Single Polarization
Weather Forecasting Products
Base Reflectivity – Rainfall Rate
Mean Radial Velocity - Wind information that related to wind motions within and relative to a storm Used for assessing rotation in a storm.
Spectrum Width – Detecting turbulence
Dual Polarization
Differential Reflectivity - Indicator of drop shape.
Correlation coefficient – Indicator of regions where the is a mixture of precipitations types.
Specific Differential Phase – Also a good indicator of rain rate
Using the base data products, the processor produces higher-level derived data products for the radar user. This document will not address the derived data products in detail as the products vary from radar to radar and the numbers of products are quite large. To ensure accuracy of the derived data products, the base data products need to be accurately maintained.

12. Weather Radars Operations Impact of Interference
Corrupts Base Products
Limits or nullifies the Radars Ability to….
Detect wind speed and direction
Locate and track hurricanes, typhoons, tornados, gales
Provide reliable data to base severe storm or flash food warnings on.
Decrease Range
Base Reflectivity – Distorts Rainfall Rate Estimates
Types of Interference
Constant
Time Varying
Pulsed
We continue to see interference despite trying to identify sources and mitigation strategies

13. Weather Radars Operations Impact of Interference – Types of Interference (Constant)
Meteo-04-9
An example of impact of a constant interference on a radar precipitation mode can be seen in this figure. It is important to highlight that, although being a constant interference, the variation in impact is due to the rotation of the antenna [[more importantly side lobes and antenna pattern]], the maximum interference (in green on this picture) being produced in the azimuth of the interfering source. The narrow beam at 200 deg is likely a back lobe.

14. Weather Radars Operations Impact of Interference – Types of Interference (Constant Interference from an RLAN)
This figure shows the impact of interference from a Radio Local Area Network (RLAN )

15. Weather Radars Operations Impact of Interference – Types of Interference (Pulsed)
Interference free
Interference corrupted
Pulsed interference can have a significant impact on the reflectivity data that a meteorologist uses to forecast severe weather events. In some cases pulsed interference could result in a returned data that cannot reliably produce an image of targets in the atmosphere. An example of this can be seen in this figure.

16. Weather Radars Operations Impact of Interference – Types of Interference (Wind Farms) [[Wind farms not listed on Slide 11 as a type of interference]]
Thunderstorm characteristics could be masked or misinterpreted
False reflectivity and radial velocity signatures could reduce forecaster's situational awareness during hazardous/severe weather events
Data masking or contamination over the wind farm and down range from the wind farm may negatively impact warning effectiveness.
False precipitation estimates could negatively impact flash-flood warning effectiveness
Forecasters were able to ‘work around’ the impacts in this situation. Within ~18 km the impacts on data and operations begins to rapidly increase.
Wind Farm
These farms are located between 20 miles and 35 miles directly southeast of the Weather Surveillance Doppler Radar located at the National Weather Service office in Cheektowaga (KBUF) in northern Erie county.  The towers are on top of ridges at elevations that exceed 1600 feet above mean sea level. At this height, the rotating turbine blades of the wind farm impact the KBUF Doppler Radar beam. As you can see in the above image depicting most of western New York, the rotating wind turbines are having an affect on the radar beam. 
Wind turbine clutter or interference that shows up on the base reflectivity, velocity and spectrum width images produced by the Doppler radar can have several impacts including:
Thunderstorm or winter storm characteristics could be masked or misinterpreted, reducing warning effectiveness in the vicinity of, and downrange of the wind farm.
False signatures contaminating Doppler velocity data in the vicinity and downrange of the wind energy facility could reduce forecaster's situational awareness, particularly during hazardous/severe weather events. Data masking or contamination if thunderstorms develop over the wind farm may negatively impact warning effectiveness.
False precipitation estimates could negatively impact flash-flood warning effectiveness. However, at the ranges of wind clutter shown here, NWS forecasters are able to “work around” the signatures and not cause an impact on forecast and severe weather operations.

17. Weather Radars Operations Impact of Interference On Our Lives
Routine weather forecasts
Severe weather and flash flood warnings
Aviation and maritime safety
Personal travel safety
Safe, timely transport of personal and commercial goods
Agriculture – your source of food
Power management
Highway management
Water management

18. Weather Radars Operations Impact of Interference
At the end of the day, the bottom line is that interference dramatically reduces a Meteorologists ability to generate reliable forecasts…..

19. Weather Radars Operations Impact of Interference – Protection Criteria
Interference Protection Criteria: The highest interference level that does not degrade the system performance beyond performance requirements

20. Weather Radars Operations Impact of Interference – Interference To Noise I/N Protection Criteria
I/N is specified as a interference signal level relative to the radar noise floor
Interference is added to receiver noise to produce a higher noise + interference level
Higher noise + interference level masks and corrupts weak but vital returns
The current ITU-R protection criteria Level for Meteorological Radars is an I/N of -10 dB.

21. ITU Definitions Weather Radars
International Telecommunications Union (ITU) – U.N. organization responsible for international regulation of radio spectrum use
International Radio Regulations – Treaty text maintained and enforced by the ITU that provides the regulations and table of frequency allocations for international radio spectrum use
Radio Service - A type of radio operation, such as meteorological satellites, broadcasting, mobile-satellite
Allocation – The authority for a radio service to use a particular frequency band
License (or Assignment) – Authority for a particular radio station to use a specific frequency under the defined technical conditions and consistent with a frequency allocation

22. ITU Definitions Applied To Meteorological Radars Meteorological Aids Service (MetAids) – 400MHz and 1680 MHz Bands Radiosondes
In the ITU, Meteorological Radars fall under the Radiodetermination Service
ITU Working Party 5B (WP 5B) is responsible for Meteorological Radars.
Three allocations exist in the Radio Regulations specifically for meteorological radars
MHz- ground based radars
MHz- ground based radars
MHz- ground based and airborne radars

23. Weather Radars Relevant ITU Documents Allocations
In the band MHz, ground based radars used for meteorological purposes are authorized to operate on a basis of equality with stations of the aeronautical radionavigation service [[3000?]]
Between 5600 and 5650 MHz, ground based radars used for meteorological purposes are authorized to operate on a basis of equality with stations of the maritime radionavigation service
The use of the band MHz by the aeronautical radionavigation service is limited to airborne weather radars and ground-based radars. … In the band MHz, ground-based radars used for meteorological purposes have priority over other radiolocation services

24. Weather Radars Relevant ITU Documents Recommendation ITU-R M.1464-1
Content: Characteristics of meteorological radars and protection criteria for sharing studies
Use: Used for performing analysis between systems operating in the radiodetermination service operating in the frequency band MHz

25. Weather Radars Relevant ITU Documents Recommendation ITU-R M.1849
Content: Technical and operational aspects of ground-based meteorological radars
Use: That the technical and operational aspects of meteorological radars as described in document be considered when conducting sharing studies and that the protection criteria for meteorological radars should be based upon Annex 1, in particular § 8.5, for assessing compatibility with interfering signal types from other services and applications.

26. Weather Radars Relevant ITU Documents Report TU-R M.2136
Content: Interference protection criteria analysis and testing results in the MHz and MHz Bands
Use: Reference document

27. Weather Radars Relevant ITU Documents Report TU-R M.2136
Content: Interference protection criteria analysis and testing results in the MHz and MHz Bands
Use: Reference document

28. Weather Radars Relevant ITU Documents Handbook R-HDB-45-2008-MSW-E
Content: Use of Radio Spectrum for Meteorology: Weather, Water and Climate Monitoring and Prediction
Use:
“The Handbook provides comprehensive technical and operational information on current observation applications and systems and on the use of radio frequencies by meteorological systems, including meteorological satellites, radiosondes, weather radars, wind profiler radars and spaceborne remote sensing. It is intended for the meteorological (i.e. weather, water and climate) and radiocommunication communities, including governmental institutions, industry as well as the general public.”

29. Looking Forward Future System Trends Weather Radar s
Dual Polarization
Phased array antennas
Allow other volume scan strategies
Can periodically return to an area of concern in atmosphere during a volume scan
Increased automation
Mode selection
Severe weather signature detection
The deployment of X-band gap filler radars where short range (mitigating cone of silence) or high resolution performance is needed.
Polarimetric radar
The next major upgrade is polarimetric radar, which adds vertical polarization to the current horizontal 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 have shown 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 storms and severe thunderstorms. The deployment of the dual polarization capability (Build 12) and the contractor-installed hardware and software modifications to NEXRAD sites will begin in 2010 and last until 2012.
Phased array
Beyond dual-polarization, the advent of phased array radar will probably be the next major improvement in severe weather detection. Its ability to rapidly scan large areas would give an enormous advantage to radar meteorologists. Any large-scale installation by the NWS is unlikely to until sometime after Such a system would more likely be installed separate from the existing WSR-88D network, perhaps only in areas like the Great Plains where tornadoes are more common.

30. Looking Forward Future ITU Activities Weather Radar s
Updates to ITU-R Document ITU-R M.1464
New ITU-R Report on Determining Maximum Interference Levels for Dual-Polarization Radars Operating in the MHz Band

31. Conclusions Weather Radars
Meteorological radars operate differently and produce different products than other radar types
The differences need to be considered when conducting sharing studies
Limitations of physics dictate frequency band use
Meteorological radars with higher sensitivity – lead to greater interference sensitivity

32. Conclusions Weather Radars
Meteorological Radars are the backbone of day to day local, regional, national and global weather forecasting
Utilize segments of the Spectrum that are well suited to their operation
Provide data for local severe storm, aviation and marine forecasting
Save lives and injuries due to tornadoes – Simmons, K. M. and D. Sutter, 2005: WSR-88D Radar, Tornado Warnings and Tornado Casualties
Sensitive systems that must be protected from interference

33. References Weather Radars
Crum, T. D. and R. L. Alberty, 1993: The WSR-88D and the WSR-88D Operational Support Facility. Bull. Amer. Meteor. Soc., 74,
Doviak, R.J. and Zrnic, D.S. Doppler Radar and Weather Observations. Dover Publications Inc, Mineola, NY
Simmons, K. M. and D. Sutter, 2005: WSR-88D Radar, Tornado Warnings and Tornado Casualties. Weather Forecasting, 20,
Burgess, D. W., T. Crum, and R. J. Vogt, 2008: Impacts of wind farms on WSR-88D Operations. Preprints, 24th Int. Conf. on Interactive Information Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, New Orleans, LA, Amer. Meteor. Soc., Paper 6B.3.
Doppler Radar Meteorological Observations: Federal Meteorological Handbook No. 11, Parts A – D (contains general specifications and information on the NEXRAD radar) available at: 
Isom, B. M. R. Palmer, G. Secrest, R. Rhoton, D. Saxion, J. Reed, T. Crum and R. Vogt, 2008: Wind Turbine Clutter Characterization and Mitigation on Federal Weather Radars (NEXRAD). Poster, American Wind Energy Association WINDPOWER 2008, Houston, TX.
Isom, B. M., R. Palmer, G. Secrest, R. Rhoton, D. Saxion, J. Reed, T. Crum and R. Vogt, 2008: Detailed Observations of Wind Turbine Clutter With Scanning Weather Radars

34. References Weather Radars
Palmer, R., S. Torres, R. Zhang, 2008: Characterization, Detection, and Mitigating Wind Turbine Clutter on the WSR-88D Network. Briefing to the NEXRAD Technical Advisory Committee Meeting, Sept 2008, available at:  V
Vogt, R. J., J. R. Reed, T. Crum, J. T. Snow, R. Palmer, B. Isom, and D. W. Burgess, 2007: Impacts of Wind Farms on WSR-88D Operations and Policy Considerations. Preprints, 23rd Int. Conf. on Interactive Information Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, San Antonio, TX, Amer. Meteor. Soc., Paper 5B.7.
Vogt, R. J., T. Crum, J. Reed, J. Sandifer, R. Palmer, B. Isom, J. Snow, D. Burgess and M. Paese, 2008: Weather Radars and Wind Farms – Working Together for Mutual Benefit. Poster, American Wind Energy Association WINDPOWER 2008, Houston, TX.
Vogt, R. J., T. Crum, J. Reed, J. Sandifer, et.al.: A Way Forward Wind-Farm Weather Radar Coexistence, American Wind Energy Association Project Siting Workshop, February , 2009, Seattle, WA
Trisant, Philippe : Radio Frequency Threats on Meteorological Radars Operations, Proceedings of ERAD 2006, Fourth European Conference on Radar in Meteorology and Hydrology, September 18-22, 2006, Barcelona, Spain
ITU/WMO Handbook, Use of Radio Spectrum for Meteorology: Weather, Water and Climate Monitoring and Prediction, 2008 Edition

35. References Weather Radars
ITU/WMO Handbook, Use of Radio Spectrum for Meteorology: Weather, Water and Climate Monitoring and Prediction, 2008 Edition
Report ITU-R M.2136, Theoretical Analysis and Testing Results Pertaining to the Determination of Relevant Interference Protection Criteria of Ground-Based Meteorological radars, ITU 2008
Report ITU-R M.2112, Compatibility/Sharing if Airport Surveillance and Meteorological Radar wit IMT Systems within the MHz Band, ITU 2007
Recommendation ITU-R M , Characteristics of Radiolocation Radars, and Characteristics and Protection Criteria for Sharing Studies for Aeronautical Radionavigation and Meteorological Radars in the Radiodetermination Service Operating in the Frequency Band MHz, ITU 2003
Recommendation ITU-R M.1849, Technical and Operation Aspects of Ground Based Meteorological Radars, ITU 2009