Agricultural Meteorology

Course: B.Sc. Agricultural

Subject :Principle of Agronomy and Agricultural Meteorology

Unit: 4

1

Climatology:-

It is defined as a scientific study of climate. Itdiscovers, describes & interprets the climate on the basis ofcauses processes that generate them orClimatology is the science which studies average conditionof weather or the state behaviour of the atmosphere over aplace or region for a long period of time.

Aristotle defined Meteorology as a study of loweratmosphere.- Meteorology is derived from the Greek word

- Meteor means Lower atmosphere - logus means science

Climate:

- Climate is defined as generalized or averagecondition of weather of a place or region.

Or- It is a composite or generalized of the variety of dayto day weather conditions.

Eg. Cold season

Weather:

- Weather can be defined as the physical condition or

state of the atmosphere at a particular time and place.

Eg. Cloudy day

Difference between weather and climate

Sr.

No. Weather Climate

1 Instantaneous physical state of

atmosphere at particular place.

Normal physical state or generated

condition of atmosphere or long term average

condition of a place.

2 Weather changes refer to specific

instant of time (day or week)

It is generalized over a longer span of time

and for a longer area.

3 It is expressed in terms of numerical

values of meteorological elements.

It is expressed in terms of time averages and

area averages of meteorological elements.

4 Weather is measured in observatory. So

the observatory must at a place for

which weather is to be described.

This is derived information on regional basis.

So scripts of observatories extending over a

region are necessary.

5 No statistical treatment is applied to the

meteorological elements. They are used

as observed and hence always changing.

Application of statistical method over a longer

period I done. It is more or less stable with

few random changes.

6 It provides meteorological

information.

It constitutes geographical information

in respect of weather.

7 Weather of two places having same

numerical value must be same.

Climate of the two places having the

same averages of weather can not be

same, because their distribution over

the years may be different.

8 Weather can be categorized as fair,

unfair, excellent etc.

Climate is classified as desert climate,

marine climate, tropical climate etc.

9 Weather decides the success or

failure of a crop in a particular

season.

Climate decides the type of crop suitable

for a region, while introducing new crops

climate is considered.

10 Adverse weather results into crop

failure or loss and warrants short

term contingent planning.

Climate is considered in long terms

agricultural planning.

Agricultural meteorology• J.W. Smith (1916) has defined Agricultural

Meteorology as “Meteorology in its relation toagriculture”

• It can be defined as the science investigatingMeteorology, climates and hydrologic condition,which are significant to agriculture.

• In short Agricultural Meteorology is the appliedbranch of meteorology, which deals with therelationship between climates, weather and lifeand growth of the cultivated plants and animals.

Importance and Scope of Meteorology in Agriculture

Weather and climate is a resource and consideredas basic input or resources in agriculturalplanning, every plant process related with growthdevelopment and yield of a crop is affected byweather.

Similarly every farm operation such as ploughingharrowing, land preparation, weeding, irrigation,manuring, spraying, dusting, harvesting,threshing, storage and transport of farm produceare affected by weather.

• 1. Characterization of agricultural climate:

For determining crop growing season, solarradiation, air temperature, precipitation, wind,humidity etc. are important climatic factors on whichthe growth, development and yield of a crop depend.

• 2. Crop planning for stability in production

To reduce risk of crop failure on climatic part, soas to get stabilized yields even under weatheradversity, suitable crops/cropping pattern/contingentcropping planning can be selected by consideringwater requirements of crop, effective, rainfall andavailable soil moisture.

• 3. Crop management:Management of crop involves various farmoperations such as, sowing fertilizer application, Plantprotection, irrigation scheduling, harvesting etc. canbe carried out on the basis of specially tailoredweather support. For this the use of operationalforecasts, available from agro met advisories, is madee.g.1) Weeding, harrowing, mulching etc are undertakenduring dry spells forecasted.2) Fertilizer application is advisable when rainfall isnot heavy wind speed is <30 km/hr and soil moistureis between 30 to 80%3) Spraying/dusting is undertaken when there is norainfall, soil moisture is 90% and wind speed is<25km/hr.

• 4. Crop Monitoring:

To check crop health and growth performance of a crop,suitable meteorological tools such as crop growthmodels. Water balance technique or remote sensingetc. Can be used.

• 5. Crop modelling and yield–climate relationship:

Suitable crop models, devised for the purpose canprovide information or predicate results about thegrowth and yield when the current and past weatherdata is used.

• 6. Research in crop –climate relationship:

Agro-meteorology can help to understand crop-climaterelationship so as to resolve complexities of plant processin relation to its micro climate.

• 7. Climate extremities:Climatic extremities such a frost floods,droughts, hail storms, high winds can beforecasted and crop can be protected.

• 8. Climate as a tool to diagnose soil moisturestress:Soil moisture can be exactly determined fromclimatic water balance method, Which is used todiagnose the soil moisture stress, drought andnecessary protective measures such asirrigation, mulching application ofantitranspirant, defoliation, thinning etc. can beundertaken.

• 9. Livestock production:

Livestock production is a part of agriculture. The set offavorable and unfavorable weather conditions forgrowth, development and production of livestock islivestock is studied in Agril. Meteorology. Thus tooptimize milk production and poultry production, theclimatic normal are worked out and on the suitablebreeds can be evolved or otherwise can provide thecongenial conditions for the existing breeds.

• 10. Soil formation:

Soil formation process depend on climatic factors liketemperature, precipitation, humidity, wind etc, thusclimate is a major factor in soil formation anddevelopment.

Means any advance information about theprobable weather in future, which is obtained byevaluating the present and past meteorologicalconditions of the atmosphere is called weatherforecast.

Weather forecasting

2

Forecasting of weather elements viz sunshine hours,occurrence of dew, relative humidity, rainfall,temperature, winds etc. Which are important inagriculture and for farming operations is known asagricultural forecast.

In weather forecasting the advance information ofweather elements like distribution of rain fall,warming for heavy rain fall, temperature changeimportant special hazardous weather like ifthunderstorm, hailstorm, show or frost, sky cover,winds, humidity, dew drought, evaporation rate etcis provided.

Agricultural weather forecast:

Weather forecasting on the basis of their validityperiods or time scale is classified as follows :

• 1. Now casting:

Nowcasting is issued for less then 12 hours. Its closelyrelated to local weather phenomena like thunderstorms, dust storms, cyclones, cold and heat waves.Nowcasting is also useful for outdoor function.

2. Short range forecast (SRF):

It is based on synoptic situation prevailing at the time offorecasting and is valid up to 3 days or 72 hrs. and areissued twice a day.

Classification weather forecasting:

3. Medium range forecast (MRF):

Forecasting of meteorological elementsover different agro climatic zones forperiods ranging from 3-10 days is known asmedium range forecast.

4. Long range forecast (LRF):

The forecast valid for more than 10 days(i.e. a month or a season is knows as longrange forecast.

Weather Forecasting symbols.

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Importance or Significance of Weather Forecast in agriculture

1. The forecast of the weather events helps for suitable planning offarm.

2. It helps in to undertake or withheld the sowing operation

3. It helps in following farm operation:

I) To irrigate the crop or not

II) When to apply fertilizer or not.

III) Whether to start complete harvesting or to withhold it.

4. It also helps in to take measures to fight frost.

5. It helps in transportation and storage of food grains.

6. Helps in management of cultural operations like plughingharrowing, hoeing etc.

7. It helps in measures to protect livestock.

• This is used to measure wind speed.

• It is one instrument used in a weather station

Anemometer

METEOROLOGICAL INSTRUMENT AND THEIR USE

4 5

Thermometer

• This is used tomeasure temperature.

• Temperature is thekinetic energy of theatoms.

• Measures in eitherFahrenheit or Celsius

6

Psychrometer

• This gives a dry bulb and a wet bulbtemperature that are then used to determinerelative humidity and dew point.

7

Barometer

• This measures air pressure.

• Atmospheric pressure is the pressure at any point in the Earth's atmosphere.

8 9

HYGROMETER

• A hygrometer is a weatherinstrument used to measurerelative humidity (how muchwater vapor is present in theair).

• It is measured as apercentage (%).

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A RAIN GAUGE

• A rain gauge is a weatherinstrument whichmeasures the amount ofrain which falls.

• Usually reported as inchesor centimeters.

11

Wind Vane

• A wind vane is also calleda weather vane

• It is one of the oldestweather tools

• It is a tool for measuringwind direction

• It spins on a rod andpoints in the directionfrom which the windcomes.

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• 1. Dew:

The deposition of water vapor in the form of tinydroplets on the colder bodies by condensation isknown as dew.

The clear sky, absence of wind. The object on whichdew forms must be good radiator and bad conductorare necessary conditions for formation of dew.

Weather phenomenon and their Representation

1413

2. Frost:

When the temperature of air falls below 0 °Cbefore the dew point is reached, the water vaporis directly converted into crystals of ice, and thisis called as frost. It is frequently called as a formof sublimation, Forts is injurious to vegetation.

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• 3. Fog:

Extremely small water droplets suspending in theatmosphere and reducing the horizontal visibilityis fog.

Classification of Fog:

A) Thick Fog : Restricts visibility up to 45 meters

B) Moderate Fog: Restricts visibility up to 450 meters

C) Thin Fog : Restricts visibility up to 900 meters.

1918

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• 4. Mist:Mist is less dense fog. The suspended water dropletsrestrict Visibility between 1000 to 2000 meters or 4 on thecoded scale (IMD) The obscurity is known as mist. Relativehumidity is at least 75% Mist disappears with rising sun.

• 5. Rime:It is formed when wet fog having super cooled dropletsimmediately freeze on striking objects like telegraph posthaving temperature below freezing point. White ice isformed on windward side.

• 6. Smog:The combined effect of smoke and fog droplets may reducevisibility and this phenomenon is called smog.

• 7. Haze:Some solid particles like dust, smoke from fire and industryrestrict visibility is haze.

Cyclone

• It is the atmospheric disturbance in which the airpressure decreases at a particular location (Lowpressure at centre) and there is a wind movementtowards centre.

• A system of close isobars with the lowest pressure atthe centre is called as cyclone.

• The pressure gradient force and carioles force causeair, flow in cycle to be spurning convergent system.

• In the northern hemisphere the direction of rotationof cyclone is antilock wise while in the southernhemisphere it is clockwise. Cyclones are also knownas Lows or press ions.

• The velocity of wind in cyclone is more than 34 knots.

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Anticyclone

• When there is a area of high pressure at centre,the flow of air starts from centre to outer side.A system of closed isobars with highest pressureat centre is known as anticyclone.

• The air flow has spiraling divergent system so thatit moves obliquely across isobars away formcentre. The direction of rotation of anticlones inthe northern hemisphere is clock wise while insouthern hemisphere it is antilock wise. Theseare known as “Hights.”

CYCLONE

ANTICYCLONE

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Reference/Sources1.https://lh6.ggpht.com/b-97dT1VvAlea4KdDDX-VB-QsynbAbUwRnTNJUXb-KU78GbGc5TyGK6BOAubLm3H2z3b=s872. https://lh4.ggpht.com/MZwvjCK8ok2pczGmO3S-cl-U_SuH9WgaBq2D8QtiRSq6SIwEmcT-qrgnaKyHxiyFLvRBSaw=s1273. https://lh4.ggpht.com/BY4oRftnUigwHxJ9obR5wmEJtNqYAOkHoiJz5tz4Z3r302mfTeXIGEqh3S88mNp2VGNADA=s624. https://lh5.ggpht.com/f7twB1cZptVcTW252SWEzW8dW-lZcs8VvGit2zsBKHhB8pOQhPEEUZ_4mhZRj0Gvuov2Mg=s855. https://lh6.ggpht.com/77m8kjIBvLKQz4KG1Ga-42u_6QQtpcOuuGKtrV4QDqadpj10SQmqUFDVurOBOc4g9eLpPGQ=s856. https://lh6.ggpht.com/EE3VKFdf_FC6uVB0SCr3C045enSPe1fEpLHODdViiBgRf4NHKaC_kWSEFmQBqhaUe0gYOw=s857. https://lh3.ggpht.com/dRZdqMsqY8B6alrsMPYrXkxqPvvz5PrL_vItUG2Hw0DBkQEe3-8L4K_VgUV8Rg5oadcO=s1048. https://lh3.ggpht.com/qa_WiC1FuUytZTxada3PL-iJVAGCZgAY2a7-mJNewPYedcJNY-uFc413ouGfKe1gGH1ZGQ=s869. https://lh4.ggpht.com/yts-OgFRKSE5ME4vycuPSw1S_cl6IvTPmqV7ryjBuUBknjjQv7Jtbz_mBKz5qXIrK5cNaA=s8510. https://lh5.ggpht.com/7BaZFeFAr86KocD54liZ8l3Atk6I6bjfFzkOImDjj8x8AeNO_GrApIr_JY6LdHDA8fbIsA=s9111. https://lh6.ggpht.com/yrMJsb59reYsYB-RQtRbjQDAHJlGry4ghOBkBY7fGekSBDJel5fLTM6_umTIIznI82GlXg=s8512. https://lh5.ggpht.com/QAQWQRfWGiuV0KHh7a8veXpvMkF5I7i1YBf0iGV23YGXBQRMvDFOqDBGtH3v4wRib66sEw=s11513. https://lh6.ggpht.com/US5v_tzUW2YTuZPGpR8C1LM0OVDKgKNsmIrR4uqKIUhySJt3RlFVWWjVfGwCw3X7TNOLlw=s14214. https://lh4.ggpht.com/EhKeh382L0F71LIyjxHlxuL4cQ5w-kjPeh52ddbVsHgncolg5rjwvj6px3_pkUD103pbpPY=s14915. https://lh6.ggpht.com/LXrZ8Kwqo_OMzDKHeczzZfkpc7M9I22y8ODYsmG7JOyviA7L9YV1vQhRERpO2tSW0QBAxeM=s11116. https://lh6.ggpht.com/OrB31sUP0VjxU_fLiEnKTKzzUc8wdJd_HuzVLkhP7DX_tZyUrdHHexaCOfJb4xCTD-OjLw=s12617. https://lh4.ggpht.com/kBSW0_dgAIUcPYQXo_IjJdlEwZ-5x2VDHOWpL3KH0xD8xrj87suBDxZTdOkWe8G07eOIqNA=s12618. https://lh5.ggpht.com/V4WcOIkKJdVrKBe1u6p_V72ars-iW17wjjSaQLxuuU1bq4AMYbHwx8wQ9ggfzCz6C2xz=s11119. https://lh4.ggpht.com/F0SYJQZFsiNEl8dDBcwjihyqwKvNzlu0Ha3bs1Ue0aFVkHLE3uvDZZMrAdYSJrnjw7Vb=s12620. https://lh4.ggpht.com/c94Xypu-LW0ce-1R4Uj_FV-KrhSTsaYfCucbibc9xl97fgm1vv8cW22nzMxfxEplYjLrcLI=s10721. https://lh4.ggpht.com/Pv46DpMRzr6gqDffEEOBsfq4a-WiWt1vWqICkn-w8Sg6z_81KFaZjPdTXoAt8jkjrQ8-WQ=s9422. https://lh4.ggpht.com/p6fJXfvyl-2Gj20o_JZYdFFaVv4ksU2YD3NVPqkpUTy2VSvSCoJNYiVII9pHMCVCSVSo_F0=s9723. https://lh4.ggpht.com/3Q0ehg0I-kOCGTOUm-hSYbqpkL32mS4JTWnb7tTXbmfk8Nn7JUw9xP8RcLTgvptYZMBlaQ=s13424. https://lh4.ggpht.com/nAvKNfnmqwKTP__xH94yud_ysm20qH_KGL6et2KmufnsxnpY7KmxnTsGln89Ii9_JnAygQ=s17025. https://lh4.ggpht.com/0cbzw26O1lD8707-MQrSvcYDwXlfa2x7P8GtX7o2jy8k3VcW2x8UcREkCLJUg20xjK-2Dg=s17026. https://lh4.ggpht.com/6tXYzEJ9qaTK95KDKD-dtG0yzMTqVP43PV-WaXQn7qY0taMFWXQrI8d2S2KVufMzQr1vGkI=s102

Text book and web resources

- www. agriinfo.in

- ecourses.iasri.res.in

- Principles of Agronomy by T. YellamandaReddy and G.H. Sankara Reddy

- Agrometeorology by SR Reddy and DS Reddy

Thank You