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WEATHER BLOG: New Proposal for Corpus Christi Weather Radar

The Corpus Christi Radar (KCRP) could start scanning lower in the atmosphere, helping forecasters protect you.

Radar is one of a meteorologist’s most important tools for forecasting and ensuring public safety. Radars provide critical real-time information and play a crucial role in fulfilling the National Weather Service’s (NWS) mission of protecting life and property.

It helps us see what’s going on in the atmosphere – both upper and lower. The lower we can see, the more weather data we can get. This is exactly what the Corpus Christi NWS offers: lowering the minimum scanning angle of the radar.

There are many different types of radar, but the one used in the national radar network used by the NWS is an S-band radar. S-band refers to the wavelength of the pulses emitted by the radar.

The Corpus Christi radar – known as KCRP – is one of 159 WSR-88D radars in the national network. The WSR-88Ds are named after the year they entered service and their ability to use Doppler shift measurements to determine wind speeds (Weather Surveillance Radar, 1988 Doppler model).

The national network is also called Next Generation Weather Radars (NEXRAD). They are designed to detect and track weather conditions at a distance of approximately 230 miles from the radar.

KCRP is located at Corpus Christi International Airport and was commissioned in September 1996. In April 2013 the radar was fitted with dual polarization capacities. This means that the radar can transmit both horizontal and vertical pulses, which helps determine the type of precipitation and improves precipitation estimates.

The NEXRAD network is used to collect meteorological data in support of weather forecasts and severe weather warnings. Radars use principles of physics such as the electromagnetic spectrum and Doppler shift to identify hydrometeors (eg, rain, hail, sleet) and other targets.

Each WSR-88D includes a 28-foot-diameter satellite dish mounted on a tower of variable height (depending on local topography) and houses electronic equipment such as a backup generator. The dish rotates 360° and is covered with a fiberglass radome to protect it from the elements.

The radar transmits a radio signal which reflects off the targets and returns to the radar. Larger objects reflect more energy back to the radar. The radar then measures the strength of the signal, its direction of return and the time between emission and return, which makes it possible to determine the characteristics of the target.

Each pulse lasts only about 0.00000157 seconds, with a “listening” period of 0.00099843 seconds in between. Over the course of an hour, the radar actually only transmits a little more 7 seconds. The remaining 59 minutes and 53 seconds are devoted to listening.

Doppler radar can also provide information about the movement of targets in addition to their position. The radar keeps track of phase (shape, position and shape) of the pulses it transmits and measures the change (change) of phase from the received echo. However, only the movement directly towards or away from the radar can be determined.

Radars can be tilted to scan multiple altitudes in the atmosphere. the scan angle is the number of degrees above or below the horizontal at the center of the main radar beam. Radars can scan the sky at angles up to +60.0° and down to -1.0°. However, in current operation, the maximum scan angle is +19.5° and the minimum scan angle is +0.5°. This is the same minimum scan angle used by most other National Network WSR-88Ds, but KCRP wants to change that.

Since the most interesting weather phenomena (like severe thunderstorms and tornadoes) occur within a few thousand feet of the surface, radar coverage of the lower parts of the atmosphere is of great value to forecasters.

However, the height above ground where the radar can collect data increases with distance from the radar due to the curvature of the earth and the upward tilt of the radar beam. The proposed action of decreased minimum scan angle to +0.3° would like develop the geographic area with radar coverage below 10,000 feet – a substantial advantage for forecasters and data users.

The area covered at 2,000 feet above site level would increase by 52%and the area covered at 10,000 feet above site level would increase by 22.9%. The floor (bottom) of radar coverage over Laredo would be reduced from 6,900 feet to 5,800 feet.

No construction or physical modification would be required – the only changes would be to the radar operating software. The proposed action would have no effect on electrical use or energy consumption.

Minimum scan angles less than +0.3° would not increase the coverage area and would result in increased ground clutter returns.

Effects of reducing the scan angle

Since the radar operates in a frequency band dedicated to government radiolocation services and the main beam would not impact the ground surface near the radar, reducing the scan angle would not cause radio interference with television, radio, cell phones, personal communication devices or active implantable medical devices.

RF exposure levels near the KCRP WSR-88D would increase slightly but would still comply with FCC and OSHA safety standards. Lowering the minimum scan angle “would not result in significant changes to the quality of the human environment,” according to the NWS environmental assessment. This would not be in addition to the environmental impacts of “past, present and reasonably foreseeable future actions to cause significant cumulative effects”.

The proposed action would like improve the quality of weather radar data made available to the NWS and other forecasters. This could indirectly benefit residents and businesses in the KCRP forecast area by “improving the accuracy of severe weather forecasts and warnings, which could lead to environmental benefits if weather-dependent economic activities become more efficient or more safe through improved weather services.”