Introduction and Scope of Agricultural Meteorology
Agricultural meteorology (Agrometeorology) is a branch of applied meteorology that investigates the responses of crops and livestock to weather and climatic conditions. Its primary objective is to optimize agricultural production by applying meteorological knowledge to agricultural planning and operations.
- Definition: The science investigating weather and climate interactions with agricultural systems.
- Scope: Crop selection, scheduling irrigation, disease and pest forecasting, fertilizer application timing, and disaster management.
- Significance in India: Indian agriculture remains heavily dependent on the monsoon; hence, agrometeorological advisories directly influence national food security and farm incomes.
Atmospheric Layers and Solar Radiation
The Earth's atmosphere is divided into distinct vertical layers based on temperature gradients: Troposphere, Stratosphere, Mesosphere, Thermosphere, and Exosphere. Weather phenomena occur almost exclusively in the troposphere.
- Troposphere: Lowest layer containing 75% of atmospheric mass and water vapor; temperature decreases with altitude (lapse rate ~ 6.5°C per km).
- Stratosphere: Contains the ozone layer which absorbs harmful ultraviolet (UV) radiation; temperature increases with altitude.
- Solar Radiation: The ultimate source of energy for crop photosynthesis; measured in terms of sunshine hours, photosynthetically active radiation (PAR, 400-700 nm), and net radiation balance.
Agro-Climatic Zones and Weather Forecasting
India has been classified into diverse agro-climatic zones by the Planning Commission and the Indian Council of Agricultural Research (ICAR) to facilitate regional agricultural planning.
- Planning Commission Classification: Divides India into 15 broad agro-climatic zones based on soil type, climate, rainfall, and water resources.
- NARS / ICAR Classification: Further refines zones into 127 agro-climatic sub-zones for localized research and extension.
- Weather Forecasting Types: Nowcasting (up to 24 hours), Short-range (1 to 3 days), Medium-range (3 to 10 days, crucial for farm operations), and Long-range (seasonal, e.g., monsoon outlook).
Microclimate Modification and Weather Hazards
Crops experience a microclimate within the plant canopy that differs significantly from macro-weather. Modifying this microclimate helps protect crops from adverse weather hazards.
- Windbreaks and Shelterbelts: Rows of trees or shrubs planted to reduce wind speed, mechanical damage, and excessive evapotranspiration.
- Mulching: Application of organic or synthetic materials to conserve soil moisture and moderate soil temperature.
- Weather Hazards: Frost, drought, hailstorms, heat waves, and cyclones managed through contingency planning and crop insurance (e.g., PMFBY).
Climate Change Adaptation and Mitigation in Agriculture
Climate change poses severe threats to global food security through rising temperatures, erratic precipitation, and increased frequency of extreme weather events.
- Adaptation Strategies: Adopting climate-resilient crop varieties (e.g., drought-tolerant, submergence-tolerant like Oryza sativa Swarna-Sub1), altering planting dates, and practicing conservation agriculture.
- Mitigation Strategies: Reducing greenhouse gas emissions (methane from paddy fields, nitrous oxide from nitrogenous fertilizers) through efficient nutrient management, direct seeded rice (DSR), and agroforestry.
| Forecast Type | Time Horizon | Primary Agricultural Application |
|---|---|---|
| Nowcasting | Up to 24 hours | Immediate pesticide spraying and irrigation scheduling |
| Short-Range | 1 to 3 days | Harvesting decisions and fertilizer application timing |
| Medium-Range | 3 to 10 days | Sowing operations, irrigation management, and pest outbreak warnings |
| Long-Range | Seasonal (1 to 3 months) | Macro-level crop planning, variety selection, and reservoir management |
Stands for Troposphere (The), Stratosphere (Strong), Mesosphere (Man), Thermosphere (Takes), and Exosphere (Exercise).
- Troposphere is the lowest atmospheric layer where all weather phenomena occur, with a normal lapse rate of 6.5°C per kilometer.
- Planning Commission of India classified the country into 15 agro-climatic zones.
- Photosynthetically Active Radiation (PAR) ranges between 400 to 700 nanometers wavelength.
- Medium-range weather forecast (3 to 10 days) is most useful for day-to-day farm operations like irrigation and plant protection.
- Evapotranspiration is measured using instruments like Pan Evaporimeter and Lysimeter.
- Instrument used to measure atmospheric pressure is the Barometer, and wind direction is measured by Wind Vane.
- Confusing short-range forecasts with medium-range forecasts; remember medium-range covers 3 to 10 days and is standard for agrometeorological advisories.
- Assuming weather and climate are identical; weather is instantaneous state of the atmosphere, whereas climate is the statistical synthesis of weather over 30 years or more.