Precise meteorological data on low hanging clouds over Kolkata airport — crucial for safe flight operations — will soon be available to pilots flying into and out of the city. The department of meteorology at Kolkata airport is in the process of installing a laser ceilometer to accurately measure the distance between the runway and the base of a cloud hanging over the airport.
Low cloud formation leads to reduced visibility in thunderstorms and heavy showers. Cumulonimbus clouds, also referred to as thunderstorm clouds, cause severe turbulence, low-level wind shear and hail. Any of these conditions can pose a threat to flight safety, particularly during the landing phase.
Till now, the Met department offered an estimation of low cloud height over Kolkata airport in pre-flight and inflight briefings. “The estimations are generally based on experience, though ceiling red balloons are also released and tracked using an instrument called theodolite. The balloons are filled with a gas whose rate of ascent is known. Its velocity is then multiplied by the time taken for it to disappear into the cloud to calculate the distance,” a Met department source said.
The weather ceilometer, on the other hand, will give the precise altitude of the low cloud, ruling out any human error during estimation. The instrument to be installed at the northern end of the primary runway will emit a laser pulse into the atmosphere. “Using LIDAR (light detection and ranging) technology, the instrument transmits fast, lowpower laser pulses into the atmosphere and detects backscattered returns from clouds and aerosols above the instrument. The altitude of the cloud is determined using the speed of light,” the weatherman explained.
The new instrument will be particularly helpful during monsoon and winter, when low cloud and fog reduces visibility and affects incoming flights. “The platform on which the ceilometer will be installed has been constructed. The electrical work is also over. A team will come from Pune to carry out the installation,” said the source. Kolkata is among six major airports in the country where laser ceilometers are being installed.
The Met department at Kolkata airport has several other instruments to gauge weather conditions, including transmissometer to calculate runway visual range (RVR), anemometer to measure wind speed, wind vane to determine the direction and hygroclip temperature and humidity intelligent sensors. A Doppler radar atop the new secretariat in Dalhousie Square tracks cloud motion over the airport and rest of the city.
Planes also have on-board weather radars that come in handy during flights.
Source: Times of India