Winter Fog Experiment (WIFEX 2016-17)
Fog
is a visible mass consisting of cloud water droplets suspended in the air or
near the Earth’s surface. The presence of heavy and extended period fog in the
northern regions of India is one of the major weather hazards, impacting
aviation, road transportation, economy and public life in the world’s most
densely populated region. Maximum fog occurrence over the Northwest India is about 48 days
(visibility < 1000m) per year, and occurs mostly during the
December-February time period. All India annual morning poor visibility days (PVD <4 km) has
increased from 6.7 to 27.3 % days. Recent studies on fog in India during the
past 10-15 years have prompted significant socio-economic concern due to
increase in frequency, persistence and intensity of fog occurrence over the
northern parts of the country. Land use changes and increasing pollution in the region are
responsible for growing Fog occurrence.
The objectives of the Winter Fog Experiment (WIFEX) are to develop
better now-casting (next 6 hours) and forecasting of winter fog on various time
and spatial scales, and help reduce its adverse impact on aviation,
transportation and economy, and loss of human life due to accidents. We need a
reliable forecasting system for Fog occurrence. The physical and chemical
characteristics of fog, meteorological factors responsible for its genesis,
sustenance, intensity and dissipation are poorly understood. Similarly,
meteorological conditions like humidity, wind and synoptic conditions are also
not well studied. Improved understanding on above aspects is required to
develop reliable forecasting models and observational techniques for accurate
prediction of Fog events.
In an effort to gain insight into these questions, the Ministry of
Earth Sciences (MoES), Government of India has taken up a multi-institutional
initiative to conduct an intensive ground-based measurement campaign at the
Indira Gandhi International Airport (IGIA), Delhi, to understand different physical
and chemical features of Fog and factors responsible for its genesis, intensity
and duration. WIFEX was conducted in a pilot mode at IGIA during last winter,
and will be continued during December 2016 till February 2017. The main
scientific objective of this project is to study the characteristics and
variability of fog events and associated dynamics, thermodynamics and fog
microphysics, with the aim to achieve better understanding of fog life cycle
and ultimately improve capability in fog prediction.
Extensive sets of comprehensive ground-based instrumentation,
including remote sensing platforms, are deployed at the Indira Gandhi
International Airport (IGIA), New Delhi. Major in-situ sensors are deployed to
measure surface micro meteorological conditions, radiation balance, turbulence,
thermo-dynamical structure of the surface layer, fog droplet and aerosol
microphysics, aerosol optical properties, real time sky images, and aerosol and
fog water chemistry to describe the complete environmental conditions in which
fog develops. These
measurements will form the basis for understanding the some of the key
questions on fog formation and dispersion. With these measurements, modeling
efforts also will be made with the ultimate aim to improve the prediction
skill. These observations from intense campaign will be further used to
validate model forecasts and to improve model capability. It is proposed to
introduce this model for operational forecasts of Fog for the winter season of
2017-18.
In
addition to Indian Institute of Tropical Meteorology (IITM), Pune, India
Meteorology Department (IMD), National Center for Medium Range Weather Forecast
(NCMRWF), Airport Authority of India, GMR, Indira Gandhi International Airport
and Indian Institute of Science Education and Research (IISER) Mohali are also
participating in this observational campaign.
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