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Describe fog formation and dissipation process a Prepared Case study.

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Submitted By:

Sourav Dey

Reg. No : 21260402016

Subject : Geoinformatics in Climatology and Satellite Meterology

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Submited to :

Dr. Bikash Parida

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Department Of Geoinformatics

(School Of Natural Resource Management)

Central University of Jharkhand

Ranchi , Brambe- 835205

FOG :

DEFINITION :

• a mass of droplets of condensed water vapour suspended in the air, often greatly reducing visibility, corresponding to a cloud but at a lower level
• a cloud of vapour, Neclei or any substance in the atmosphere reducing visibility.

Notes :

• Fog shows up when water vapor, or water in its gaseous form, condenses. During condensation, molecules of water vapor combine to make tiny liquid water droplets that hang in the air. We can see fog because of these tiny water droplets.
• Fog happens when it’s very, very humid. There has to be a lot of water vapor in the air for fog to form.
• In order for fog to form, dust or some kind of air pollutants needs to be in the air. Water vapor condenses around these microscopic solid particles or called Nuclei . Sea fog, which shows up near bodies of salty water, is formed as water vapor condenses around bits of salt.

Types of Fog :

Fogs are also classified into 4 types on the basis of visibility :

R. Byers (1944) modified the classification of fogs as suggested by Willett and presented the modified form as follows :

• Formation : Fog forms by increasing moisture and/or cooling the air.

Moisture is increased by the following :

• Precipitation.

• Evaporation from wet surfaces.

• Moisture advection.

Cooling of the air results from the following:

• Radiational cooling.

• Advection over a cold surface.

• Upslope flow.

• Evaporation.

• Dissipation: Removing moisture and/or heating the air dissipates fog and stratus.

Moisture is decreased by the following:

• Turbulent transfer of moisture downward to the surface (e.g., to form dew or frost).

• Turbulent mixing of the fog layer with adjacent drier air.

• Advection of drier air.

• Condensation of the water vapor to clouds.

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Heating of the air results from the following:

• Turbulent transport of heat upward from air in contact with warm ground.

• Advection of warmer air.

• Transport of the air over a warmer land surface.

• Adiabatic warming of the air through subsidence or downslope motion.

• Turbulent mixing of the fog layer with adjacent warmer air aloft.

• Release of latent heat associated with the formation of clouds

INTRODUCTION

IGP is the region which is mostly effected by Morning time fog. Morning time when the temperature warms up the fastest. In general, comparing the 4am to 11am timeframe with the 11am to 4pm timeframe, more warming occurs in the 4am to 11am timeframe. This is because a shallow layer of cold air gathers at the surface of the earth on many nights. Longwave terrestrial radiation contributes to air cooling. This effect is most noticeable when the wind is fairly light, as there is less mixing with the upper air. When the sun hits the surface of the earth, a flat layer of cold air rapidly mixes with the warm, dry air above. There is also heating from the sun, which heats the surface of the earth and heats the air layer on the surface.

Aerosols are made up of particles with various chemical compositions, optical characteristics, shapes, and sizes, and they have a big impact on how the climate changes on the planet .

They affect the balance of the earth's radiation budget indirectly by acting as cloud condensation nuclei, which can significantly affect precipitation, in addition to directly reflecting solar radiation Additionally, rising anthropogenic aerosol emissions might contaminate the air and endanger human health.

Accurate information gathering on aerosols can aid in studies such as those looking at climate change, measuring aerosol environmental pollution, and estimating aerosol particle concentration.

There are different types of fog and they occurs in different situation of climate, And sometimes anthropogenic activities ( Air Pollution ) also help to condense . Formation of fog has some negative and positive consequences .

By using remotely sensed data with moderate resolution is used to perform the estimation of Fog formation of Delhi region of last Winter time (December-21, January-22).

CASE STUDY

STUDY AREA:�� The Indo-Gangetic Plains (IGP) is the place where we can see the mostly dense occurance of Fog .Capital of India ; Delhi mostly suffer from fog and adjusent states or regions like Haryana,Punjab,uttar Pradesh ; lies on IGP . In the map below showing the IGP in red and the Delhi using point . Ive Choosed Hariyana and Delhi . Geographic Coordinate of Delhi : Top of FormLatitude: 28°39′07″ N�Longitude: 77°13′53″ E�Elevation above sea level: 227 m = 744 ft�The latitude of Haryana, India is 29.065773, and �the longitude is 76.040497. �Haryana, India is located at India country in the States place category .�

Source : Sathiyamoorthy,V & Kishtawal,C.M . ” Radiative characteristics of fog over the Indo-Gangetic Plains during northern winter” ,Climate Dynamics,47, 19 December 2015 (Bruijnzeel et al. 2005).

METHODOLOGY :

This methodology involves downloading data from different sources (slide 08) and extracting data with R programming software to make it compatible with GIS platforms... Additionally, to investigate temporal variability, graphs are projected onto a GIS platform to extract fog across the Haryana and Delhi .

Temperature and Humidity data are converted into Daily mean using for loop and visualized the graph and ploted hourly data of 16^th December which day we got the highest dense fog occurance. I,ve used the data of 4AM to 11AM (India Standard Time (IST) or local time) with one hour interval (in this time mostly fog form). And prep[ared layout. Each analysis are performed in the R programming software.

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DATA USED :

• MODIS 500 meter Aerosol Optical Depth

(Optical_Depth_055) data is used for mapping visibility .

• ERA5 hourly data with 0.25° x 0.25° resolution 10meter

u-component of neutral wind and 10m v-component of

neutral wind data to visualize wind speed and wind

direction map.

• Temperature (in Degree Kelvin) at 2 meter height data collected from GIOVANNI . ( Kelvin to Celcius by subtracting 273.15 )
• Relative Humidity ( NASA/POWER CERES/MERRA2 Native Resolution Daily Data) with ½ x ½ degree spatia resolution .

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Methodology Contd….

• Presence of Nuclei , good amount of moisture ,near to dew temperature and stable wind condition gave a favourable environment to form (dense) fog.

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• By observing the data of recent winter season (December2021-January2022) we can see Relative humidity is nearly constant. AOD graph showing the atmospheric nuclei presence or highly presence between December 14 to December 16^th .
• The Relative humidity which representing that the moisture content in the atmosphere of my study region create a favourable condition to form fog. By observing the data of recent winter season we can see Relative humidity is nearly constant or less fluctuating and atmosphere is consist of good amount of moisture .
• In the graph lowest Temperature occurred between 14^th to 18^th December.

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• From these graph of last winter December(2021) to January(2022) we can see the favourable condition to dense fog occurrence is possible between 14^th to 16^th December. B y supposing the dense fog occurrence I’ve choose 16^th December to study the occurrences of FOG .

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RESULTS :

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say the Dew point

Temperature

Result Contd….

AOD

AOD showing presence of nuclei in the atmosphere (Hariyana and Delhi region) : :

Using MERRA2 data showing the presence of moisture content in the atmosphere (Haryana and Delhi region) : :

Temporal variability of Temperature at 2 meter height (in Kelvin) :

Wind speed & Direction Hourly variability : :

CONCLUSION :

Here we ve discussed how climatic factors help is forming fog or mist . Without using FOG and Visibility data we also can analyse fog this indirect method . Every year during the peak winter season (December-January the Indo-Gangetic Plains (IGP) experience severe fog extending over a stretch of 1500 km . Increasing air pollution combined with sufficient moisture available due to the passage of frequent north-westerlies favor fog formation in this region. Favourable condition of some climatic variable ( air moisture, wind speed , Temperature etc) and topography helps fog to take place. Delhi the capital of India layes in that region ;and the adjusent teritory Haryana suffer for the occurance of dense fog. by analyse individual fog inducing factors like

• AOD , aerosol emissions might contaminate the air and endanger human health.

Accurate information gathering on aerosols can aid in studies such as those looking at climate change, measuring aerosol environmental pollution, and estimating aerosol particle concentration.

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• Relative Humidity ,
• Wind Speed ,
• Temperature .

If we find the individual variables of fog are present in the study space we can make an idea of fog formation and we also can probably estimate the visibility or quantitative information of the fog .

REFERENCES :

• Banerjee, S., & Padmakumari, B. (2020). Spatiotemporal variability and evolution of day and night winter fog over the Indo Gangetic Basin using INSAT-3D and comparison with surface visibility and aerosol optical depth. Science of the Total Environment, 745, 140962. https://doi.org/10.1016/j.scitotenv.2020.140962 
• Gultepe, I., Pearson, G., Milbrandt, J. A., Hansen, B., Platnick, S., Taylor, P., Gordon, M., Oakley, J. P., & Cober, S. G. (2009). The Fog Remote Sensing and Modeling Field Project. Bulletin of the American Meteorological Society, 90(3), 341–360. https://doi.org/10.1175/2008bams2354.1 
• Jin, S., Ma, Y., Zhang, M., Gong, W., Dubovik, O., Liu, B., Shi, Y., & Yang, C. (2019). Retrieval of 500 m Aerosol Optical Depths from MODIS Measurements over Urban Surfaces under Heavy Aerosol Loading Conditions in Winter. Remote Sensing, 11(19), 2218. https://doi.org/10.3390/rs11192218
• Dupont, J. C., Haeffelin, M., Protat, A., Bouniol, D., Boyouk, N., & Morille, Y. (2012). Stratus–Fog Formation and Dissipation: A 6-Day Case Study. Boundary-Layer Meteorology, 143(1), 207–225. https://doi.org/10.1007/s10546-012-9699-4

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