Fog predictions could become more accurate with a new method developed by the Indian Institute of Technology (IIT) Delhi in association with the Centre of Excellence in Climatology.
In the trial stages, the method has been found to predict the occurrence of fog with an accuracy of 95 per cent-the forecasts precise within a time window of 30-90 minutes.
Fog is a common phenomenon in Delhi during winter, thanks to the passage of the western disturbance across northwestern India along with a significant amount of moisture.
The new method uses a high-resolution Weather Research and Forecasting (WRF) model, through which the likeliness of foggy and non-foggy days is identified.
Delhi has significant frequencies of low winds, especially at night. Due to some other local factors, scientists say, fog prediction is a complex process and requires adequate representation of the local perturbations in weather prediction techniques.
The model, brought out by IIT Delhi Professor Manju Mohan and Swagata Payra of the Centre of Excellence in Climatology, is pivoted on an approach known as Multi-rule Based Diagnostic (MRD) which characterises the local atmospheric conditions.
"Fog prediction has long been a challenge for operational forecast. This is mainly due to lack of appropriate fog physics in current operational models. The method has been used for prediction after successful validation for surface temperature, relative humidity, and wind speed over the region of interest," Mohan and Payra said describing their study.
"After analysis of numerous simulations over the study area, criteria for the above meteorological parameters are used to determine the onset of fog. The MRD approach helps predict fog for the next three days. There is a 95 per cent success rate for predictions; in more than half, i.e. 56 per cent, of onset time predictions, we achieved an accuracy of 30 minutes, while 84 per cent of the times, there was an accuracy of 90 minutes," they added.
Dense fog is known to disrupt life in the Capital and NCR every winter, causing several accidents and throwing flight schedules in disarray. Visibility is lowest during the peak winter months of December and January.
An analysis of visibility data over the years clearly shows that fog is a recent phenomenon, and its density directly proportional to the Capital's rapid urbanisation. Between 1950 and 1955, fog frequency was recorded at 6.4 per cent, which rose to 58 per cent in the 1996-2001 period. Between 2002 and 2011, fog frequency increased to 71.69 per cent, hitting 79.43 per cent between 2002 and 2011.
(indiatoday)
