The Case for PAGASA's Doppler Radars

To get a better view of the storms approaching the country, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) is looking to several more doppler radars across the country —on top of the three operational ones it is currently using for weather forecasting.

PAGASA in Bato
In a phone interview with GMA News Online, PAGASA's engineering and technology services division OIC Engr. Edwin Mandreza said the deployment of the radars in Antique, Busuanga and Zamboanga are currently in the planning stages.

On the other hand, two radars in Virac, Catanduanes and Tagaytay City, Cavite, are currently under construction, and will be finished before the year ends, Mandreza said.

Meanwhile, the doppler radar in Mactan, Cebu, will begin construction after the Tagaytay radar becomes operational by the end of 2011, while the radar in Hinatuan, Surigao del Sur is still being calibrated, he added.

A new doppler radar in Tampakan, South Cotabato, on the other hand, is set to begin construction this year.

The existing ones that PAGASA is using are located in Baguio City, Baler in Aurora and in Subic.

He added that their automated weather stations in Aparri and in Guiuan, Eastern Samar, which were funded by the Japan International Coordinating Agency, will soon have doppler radars of their own, too.

Mandreza said that should the agency complete its plans to have a total of 13 doppler radars sprawled across the country, it will give the agency a better view of oncoming storms and in turn give more accurate weather predictions.

On average, these doppler radars have a maximum coverage of about 480 kilometers, enough to produce images of weather disturbances far out at sea.

Mandreza clarified, however, that some of these radars have "blind spots" due to certain obstructions, such as towering mountains in the provinces.

He cited the case of the radars in Baguio and Baler, which could not accurately measure weather conditions in Metro Manila due to the blockage caused by the Sierra Madre Mountain Range.

"Kaya nagtayo ng radar sa Subic, para mas kaunti ang obstruction at malapit-lapit sa Metro Manila," he said.

These obstructions, he said, are one of the primary considerations of PAGASA in determining where to place their radars.

When mountains, for example, are near the radar, the microwave signal that the radar emits will quickly bounce back even before the radar's receiver opens to register the returning signal, which produces a blind spot in the radar image.

On most occasions, he added, these radars are placed on coastal lines, since these are the areas that often come in contact with different weather disturbances.

Compared with weather satellites, Mandreza said doppler radars are more accurate and useful since they have the ability to also measure middle and lower clouds, while the former can only produce images of the top view of the clouds.

"When it comes to measuring the amount of rainfall, it's very accurate. Maganda ang estimation. Nakikita niya kasi ang mga middle and lower clouds, na nakaka-affect rin sa area," he said.

He added that the radars placed in different altitudes also help in accurately pinpointing the location of the storm, which would not be possible using satellite images.

"Pag ang bagyo ay mababa, sa Guiuan makikita 'yan. Kapag tumaas, sa Virac, tapos kapag tumaas pa ulit, sa Baguio," he explained.

Though they already have the plans outlined, Mandreza said that as a government agency, they are also struggling to fund the deployment of the doppler radars they are planning to place in the coming years.

A typical mid-range radar (like the ones PAGASA is currently using), according to Mandreza, costs around P60 to P70 million pesos, while the more high-end ones sell for about P80 to P100 million pesos.

Source: GMA News Online