Agrometrology

• Agricultural meteorology


  The branch of applied meteorology which deals with the response of crops and animals to the physical environment. It is the study of physical process of the atmosphere that produces weather in relation to agricultural production.
• Scope of Agricultural Meteorology

  • To study climatic resources of given area for effective production
  • To quantify favourable weather normal for effective farm operations
  • To develop crop/animal weather relationships for estimation of animal/crops productivity
  • To study weather- crop pest and disease relationships
  • To modify micro climatic for increasing agricultural productivity
  • To delineate agro-ecological zones for efficient use of resources and fast transfer of technology
  • To prepare crop weather diagrams and crop weather calendars for timely operations by farmers
  • To develop crop/animal growth simulation models for prediction of productivity in advance and also obtaining potential yield in different agro- ecological zones
  • To determine and monitor drought for effective drought management
  • To prepare value added weather based agro-advisory and its real time dissemination to farmers for reducing input cost and increasing productivity
• Weather


  The state of the atmosphere at a given time and place, with respect to variables such as temperature, moisture, wind velocity, and barometric pressure. It describes the atmospheric conditions at a specific place at a specific point in time.

  
• Climate


  Commonly defined as the weather averaged over a long period and for a large area. It describes the average conditions expected at a specific place at a given time.
• Differences between Climate and Weather


  • Definition
  • Components
  • Forecast
  • Determining factors
  • About
  • Time period
  • Study

  
• Weather variables/elements


  • Temperature
  • Humidity
  • Precipitation
  • Atmospheric pressure
  • Wind

  
• Earth's Atmosphere


  The atmosphere is a thick gaseous envelop which surrounds the earth from all sides and is attached to the earth's surface by gravitational force.
• Composition of Earth's Atmosphere

  • Gases
  • Water vapour
  • Particulate matter
• Troposphere


  • The lowest layer of the atmosphere, and makes up about 75-80% of Earth's atmosphere. All weather phenomena occurs in the troposphere.
  • Temperature decreases at the rate of 6.5 0C/ 1000 m as we go upward and is called Normal Lapse Rate.
  • The air gets thinner as we travel upward in the Troposphere because nearly all of the water vapour and dust particles of the atmosphere are in the Troposphere.
  • At the top of the Troposphere, there is a place called the Tropopause, which is boundary between Troposphere and Stratosphere.

  
• Stratosphere


  • The second-lowest layer of Earth's atmosphere. It lies above the troposphere and is separated from it by the tropopause.
  • This layer extends from the top of the troposphere at roughly 12 km above Earth's surface to the stratopause at an altitude of about 50 to 55 km.
  • The atmospheric pressure at the top of the stratosphere is roughly 1/1000 the pressure at sea level.
  • It contains the ozone layer, which is the part of Earth's atmosphere that contains relatively high concentrations of that gas.
  • The stratospheric temperature profile creates very stable atmospheric conditions, so the stratosphere lacks the weather-producing air turbulence that is so prevalent in the troposphere.
• Mesosphere


  • The third lowest layer in Earth's atmosphere, and this is where meteorites burn up, before they reach Earth.
  • As we go up in this layer, temperature decreases.
  • The mesosphere is the coldest place on Earth and has an average temperature around −85 °C.
• Thermosphere


  • One of the upper layers of the atmosphere. It also includes the exosphere, and ionosphere.
  • Aurora Borealis occurs in the Thermosphere, charged particles emit photons of light which forms the aurora.
  • Temperatures climb rapidly in the thermosphere, due to the absorption of solar radiation by the small amount of residual oxygen gas.

  
• Noctilucent clouds


  The highest clouds in the atmosphere, visible to the naked eye if sunlight reflects off them about an hour or two after sunset or before sunrise

  
• Noctilucent clouds


  • Most readily visible when the Sun is around 4 to 16 degrees below the horizon

  
• Sprites or ELVES


  A type of lightning that forms far above tropospheric thunderclouds
• The mesosphere is the layer where most meteors burn up upon atmospheric entrance
• The mesosphere is too high above Earth to be accessible to jet-powered aircraft and balloons, and too low to permit orbital spacecraft
• The mesosphere is mainly accessed by sounding rockets and rocket-powered aircraft
• Thermosphere


  One of the upper layers of the atmosphere, includes the exosphere and ionosphere
• Aurora Borealis occurs in the Thermosphere, charged particles emit photons of light which forms the aurora
• Thermosphere


  • Temperatures climb sharply in the lower portion
  • Extends from the mesopause at an altitude of about 80 km up to the thermopause at an altitude range of 500–1000 km
  • Height of the thermopause varies considerably due to changes in solar activity
• Exosphere


  The outermost layer of Earth's atmosphere, extends from the exobase at an altitude of about 700 km above sea level to about 10,000 km
• Exosphere


  • Mainly composed of extremely low densities of hydrogen, helium and several heavier molecules including nitrogen, oxygen and carbon dioxide closer to the exobase
  • Atoms and molecules are so far apart that they can travel hundreds of kilometres without colliding with one another
  • Particles constantly escape into space and follow ballistic trajectories
• The exosphere contains most of the satellites orbiting Earth
• Atmospheric pressure


  The pressure exerted by the weight of air in the atmosphere of Earth
• Atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point
• Low-pressure areas have less atmospheric mass above their location, whereas high-pressure areas have more atmospheric mass above their location
• As elevation increases, there is less overlying atmospheric mass, so that atmospheric pressure decreases with increasing elevation
• Mean sea level pressure (MSLP)


  The atmospheric pressure at sea level, the pressure normally given in weather reports
• Average sea-level pressure is 101.325 kPa (1013.25 hPa or mbar) or 29.92 inches (inHg) or 760 millimetres of mercury (mmHg)
• Wind


  Air in motion, moves due to spatial differences in the density of the atmosphere

  
• Factors affecting wind


  • Pressure gradient
  • Rotation of the Earth (Coriolis force)
  • Centripetal force
  • Friction
• Types of wind


  • Planetary winds
  • Trade winds
  • Westerlies
  • Periodic winds (Monsoons, Land and Sea Breezes, Mountain and Valley Breezes)
  • Local winds (hot, cold, convectional and slope)

  
• Cyclone


  A large scale air mass that rotates around a strong centre of low pressure, characterized by inward spiralling winds that rotate counter-clockwise in the Northern Hemisphere and clockwise in the southern hemisphere

  
• Structure of a cyclone

  • Centre (eye) is the area of lowest atmospheric pressure
  • Wind flow is counter-clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere

  
• Tropical cyclone


  Cyclone that forms due to latent heat driven by significant thunderstorm activity, and is warm core
• Formation of tropical cyclone

  1. Surface low can form due to topography or mesoscale convective systems

  2. Flow becomes cyclonic around the low

  3. Polar air moves equatorward on the west side, warm air moves poleward on the east side

  4. Cold front forms on the west side, warm front forms on the east side

  5. Cold front usually moves quicker and "catches up" with the warm front
• Solar radiation


  The flux of radiant energy from the sun

  
• Solar radiation is the prime source of energy on earth and life depends on it
• All matter at a temperature above the absolute zero emits energy from the surrounding space