Assessment of winter Fog conditions at CCSI Airport, Lucknow, India (2018-2025)

This study considers horizontal visibility a hazard parameter due to airport operational activities during December, January, and February (2018-2025). The fog conditions were the maximum in 2023 and the minimum in 2019. It iss found that dense fog conditions formed during the early hours, and 9.4% and 8.8% of the fog events prevailed at 0200 UTC and 0100UTC, respectively. However, fog disappeared due to solar insolation till 1200UTC again during the later part of the day, from 1800UTC to 2300UTC. Fog engulfed the Airport during dense/very dense fog conditions; the aviation sector was affected including delay, cancellation, diversion etc. due to a sudden drop in the visibility. The month of January (with 54.3% of fog events during the study period) was highly susceptible to low cloud cover development, which subsequently reduced the horizontal visibility even up to zero meters and caused the imposition of the Low Visibility Procedure (LVP), in which non-essential activities would be suspended on the airfield. Almost every year, shallow fog conditions had the highest duration, with a maximum from 2020 to 2023, when the maximum total fog duration was reported. The dense & very dense Fog conditions had relatively the lowest and stable duration from 2018 to 2025, except the year 2019, which had recorded the lowest number of dense and very dense fog conditions instances, but had the potential to disrupt the aviation services. The bootstrapped slope estimates were computed to examine the horizontal visibility threshold, such as below 50m, 500m, 800m, and 1000m, which is crucial and efficient for airport operations. The Mean slope was found to be maximum for 1000m threshold, +66.55 (days/year) but having low confidence, strong for 800m (+50.69 days/year), slight increase for below 50m threshold (+4.80 days/year), for 200m threshold (+17.79 days/year) and moderate increase for 500m horizontal visibility (+32.87 days/year) but not statistically significant. In the present study, analysis showed that the dense/very dense fog is formed when the relative humidity exceeded 82 %; dew point depression was less than 2°C and wind speed was in the range of 0-3 knots.