Weather Radar History, and the Impact Made by the WSR-88D

I've been trying to think of something interesting to write about. I decided to write a brief history of weather radar, and the impacts made by the WSR-88D Next Generation Radar (NEXRAD) system.

First, a brief explanation of how radar works, before we go into the history of Doppler Radar.

The term "RADAR" stands for RAdio Detection And Ranging. Doppler radar works by sending out radio waves, known as pulses. When these pulses hit an object, such as a raindrop, they bounce back to the radar, and calculations are made to determine storm position. (This is a basic description of how radar works. If you want to know more, here is a link to the NWS.)

There are several types of radar products offered by the WSR-88D (go here for more info, as this is only a basic explanation):

Reflectivity, which shows storm intensity based on the amount of energy reflected back to the radar.

Velocity, which shows the motion of the target object currently in the path of the radar beam.

There are also two precipitation products. One attempts to estimate the rainfall amount expected within one hour, and the other attempts to estimate the total amount of rainfall a given storm will produce.

Now, the history.

 The British were the first to develop devices that could locate thunderstorms, through the work of Sir Robert A. Watson-Watt, in 1935. From 1942 to 1944, work was done at the Massachusetts Institute of Technology's Radiation Laboratory that helped show that storms could be seen on certain types of radar systems, and at different wavelengths, up to distances of 150 miles. Work continued during WWII, and through research conducted at harbor defense radar systems in Panama, many basic features of storm structure were discovered.

After WWII, the Weather Bureau was able to acquire AN/APS-2F aircraft radar systems from the U.S. Navy. These were renamed Weather Surveillance Radars with designations ranging from 1, 1A, 3, 4, and  deployed slowly, with around five per year coming into operational use. The first WSR was deployed on March 12th, 1947 in Washington, D.C. A second WSR was deployed in Wichita, Kansas on June 1st. Eventually, radar systems were being made specifically for use by the Weather Bureau. These were known as AN/CPS-9 Storm Detection Radars. In the 1950s, more advancements in radar technology were made, and in 1953, hook echoes (a feature seen on radar that indicates a tornado) were first seen on a radar in Illinois.

Fast forward to 1990: A new WSR system is implemented in Norman, Oklahoma. This new Next Generation Radar (NEXRAD) system, the Weather Surveillance Radar 1988 Doppler, was the result of many years worth of advancements made in radar technology. These Next-Gen systems are currently deployed at every National Weather Service office nation-wide, as well as many military installations.

Currently, plans are being made for even more advancements. The National Severe Storms Laboratory (NSSL) is working on phased-array radar systems.  WSR-88D radar transmits one beam of energy, then has to wait for the pulse to return before going to the next elevation angle. When it has finished scanning every angle it starts the process over. By this time, six to seven minutes have passed, and in that time, the storm could be over, or have produced a tornado that was missed by radar.  Phased-array radar on the other hand, sends out multiple pulses one at a time, so the radar has no need to tilt to look at the different elevation angles. This results in scanning times of about 30 seconds, which is much, much faster than what the WSR-88D is capable of. Having the ability to do a complete scan in 30 seconds will enable forecasters to see storms better, and will help to increase warning times in severe situations. Unfortunately, phased-array radar will most likely only be installed in select areas.

In closing, radar has come a very long way from the early technology of the 1940s and '50s and is constantly improving. Just imagine what we'll be looking at in 20 years.