Chennai, Oct 31:
Fog and Mist prevailed over Interior Tamil Nadu on Saturday morning considerably reducing the visibility and the Met office attributed it to saturation of near surface air.
In an update, it said meteorological observations recorded at Tiruchirappalli Airport during the early morning hours of today indicated the occurrence of fog and mist. Visibility decreased to 800 metres around 7:00 AM, with fog (FG) reported in the METAR observation.
At that time, the surface temperature and dew-point temperature were both 26 deg C, indicating saturation of the near-surface air. Very light to calm wind conditions were also observed.
Subsequently, with an increase in temperature following sunrise, visibility gradually improved to 1,500 metres by 8:30 AM, indicating the gradual dissipation of fog and mist, the Met office said.
Similar foggy or mist-like conditions have also been observed over parts of interior Tamil Nadu, particularly in areas located close to waterbodies, during the early morning hours.
The prolonged clear-sky conditions prevailing over most parts of Tamil Nadu, especially in North and North Interior Tamil Nadu, during the past few days have favoured enhanced nocturnal radiational cooling, resulting in a fall in minimum temperatures.
The movement of Very Severe Cyclonic Storm Arnab has influenced the prevailing wind pattern, resulting in the absence of significant moisture-bearing northeasterly winds over these regions and favouring relatively clear skies.
Further, the availability of moisture in the vicinity of waterbodies, along with calm or light wind conditions, has contributed to an increase in near-surface relative humidity. As the near-surface air temperature approaches the dew-point temperature, shallow fog or mist-like conditions develop, particularly during the early morning hours.
Such foggy or mist-like conditions are generally short-lived and are expected to dissipate after sunrise due to solar heating and the subsequent increase in surface temperatures.