Temperature | Atmospheric Pressure | Surface Wind Velocity and Direction | Atmospheric Humidity |
Precipitation | Clouds | Special Instruments | Weather Satellites |


SPECIAL INSTRUMENTS

A. Pilot Balloon/Theodolite

A Pilot Balloon is a meteorological balloon that is filled with gas lighter than air. When the pilot balloon is used in conjunction with a theodolite it is used to determine the speed and direction of winds at different levels of the atmosphere.

The theodolite is similar to an engineer's transit. It consists of a sighting telescope mounted so that it is free to rotate around a horizontal and a vertical axis and has graduated scales so that the angles of rotation maybe measured while tracking the pilot balloon.

The elevation angles and azimuths of the balloon are recorded from the theodolite and these data at the end of the flight which may last for more than an hour are plotted to a plotting board. The wind speed and direction at selected levels are calculated either by trigonometric methods or graphical methods.

Night observation is accomplished by attaching a lit paper lantern to the balloon.



B. Radiosonde

Radiosonde, an airborne instrument used for measuring pressure, temperature and relative humidity in the upper air is the radiosonde. he instrument is carried aloft by a meteorological balloon inflated with hydrogen. The radiosonde has a built-in high frequency transmitter that transmits data from the radiosonde meter and recorded on the ground by a specially designed radiosonde receiver.



C. Rawinsonde

A more sophisticated version of this instrument is the rawindsonde. The rawindsonde is an electronic device used for measuring wind velocity, pressure, temperature and humidity aloft. It is also attached to a balloon and as it rises through the atmosphere, it makes the required measurements.


D. Rawin

Another special instrument is the Rawin which is short for Radar and Wind. It is an electronic device that measures pressure, temperature and humidity.


E. Wind Finding Radar

Another instrument is the Wind Finding Radar. It determines the speed and direction of winds aloft by means of radar echoes. A radar target is attached to a balloon and it is this target that is tracked by ground radar. The bearing and time of interval of the echoes is evaluated by a receiver.


F. Weather Surveillance Radar

A Weather Surveillance Radar is of the long range type which detects and tracks typhoons and cloud masses at distance of 400 kilometers or less. This radar has a rotating antenna disk preferably mounted on top of a building free from any physical obstruction. Radio energy emitted by the transmitter and focused by the antenna shoots outward through the atmosphere in a narrow beam. The cloud mass, whether it is part of a typhoon or not, reflects a small fraction of the energy back to the antenna. This reflected energy is amplified and displayed visually on a radar scope. The distance or slant range of the target from the radar is determined through the elapsed time the signal is transmitted and then received as an echo. Its direction is determined by the direction at which the focused beam is pointing at the instant the echo is received. The radar is a useful tool in tracking and monitoring tropical cyclones.