Instruments Used in Agricultural Meteorology
- Thermometer – Measures air temperature.
- Maximum–Minimum Thermometer (Six’s Thermometer) – Measures daily max and min temperature.
- Soil thermometer – Measures soil temperature at different depths.
- Thermograph – Records continuous temperature variation.
- Hygrometer – Measures relative humidity.
- Psychrometer – Measures humidity using dry-bulb and wet-bulb thermometers.
- Hair hygrometer – Uses human or animal hair to measure humidity changes.
- Anemometer – Measures wind speed.
- Wind vane – Indicates wind direction.
- Cup anemometer – Invented by Robinson (1846).
- Rain gauge – Measures rainfall in mm.
- Class A Pan Evaporimeter – Measures evaporation (diameter 120.7 cm).
- Lysimeter – Measures evapotranspiration.
- Sunshine recorder (Campbell-Stokes) – Measures duration of bright sunshine.
- Pyranometer – Measures solar radiation (short-wave).
- Pyrheliometer – Measures direct solar radiation.
- Net radiometer – Measures net radiation balance.
- Barometer – Measures atmospheric pressure.
- Mercury barometer invented by – Torricelli (1643).
- Altimeter – Measures altitude based on air pressure.
- Stevenson screen – Protects thermometers from radiation and precipitation.
- Ceilometer – Measures height of cloud base.
- Nephelometer – Measures cloudiness (turbidity).
- Snow gauge – Measures snow precipitation.
- Weather radar – Detects and tracks rainfall and storm movement.
- Weather satellite – Provides cloud cover, temperature, and rainfall data.
- Automatic Weather Station (AWS) – Measures weather parameters digitally.
- Agrometeorological observatory – Set up at 1.25 m height for standard instruments.
- Standard height for measuring air temperature – 1.2–2 m above ground.
- Standard height for measuring wind speed – 2 m above ground (agro-met stations).
Important Numerical Values
- Solar constant – 1.94 cal cm⁻² min⁻¹ = 1367 W m⁻².
- Lapse rate – 6.5 °C per km altitude in troposphere.
- Adiabatic lapse rate (dry) – 9.8 °C per km.
- Albedo of Earth – 30 %.
- Evaporation from free water surface – 3–6 mm day⁻¹ (average).
- Relative humidity comfort range for crops – 60–70 %.
- Average atmospheric pressure at sea level – 1013.25 mb = 760 mm Hg.
- 1 millibar = 100 N m⁻².
- Pressure decreases with altitude at – 1 mb per 10 m approximately.
- 1 mm rainfall = 10,000 L ha⁻¹.
- 1 inch rainfall = 25.4 mm.
- Sunshine hours per day (tropical regions) – 8–10 hours average.
- Visible spectrum for plants (PAR) – 400–700 nm.
- Specific heat of water – 1 cal g⁻¹ °C⁻¹ (highest among common substances).
- Average Earth temperature – 15 °C.
- Water vapor condenses when RH = 100 %.
- Dew point occurs when actual vapor pressure = saturation vapor pressure.
- Dry adiabatic lapse rate – 9.8 °C per km; Moist adiabatic lapse rate – 6 °C per km.
- Duration for crop meteorological week (CMW) – 7 days (Monday–Sunday).
- Number of standard meteorological weeks in a year – 52 or sometimes 53.
Meteorological and Agrometeorological Institutions in India
- IMD (India Meteorological Department) – Established in 1875, HQ New Delhi.
- Founder Director of IMD – Henry Francis Blanford.
- Agrimet Division of IMD – Established 1932, Pune.
- National Centre for Medium Range Weather Forecasting (NCMRWF) – Noida, Uttar Pradesh.
- Indian Institute of Tropical Meteorology (IITM) – Pune.
- Space Applications Centre (SAC) – Ahmedabad.
- National Remote Sensing Centre (NRSC) – Hyderabad.
- Mausam – Official weather information portal of IMD.
- Agromet Advisory Service (AAS) – Provides weather-based advisories to farmers.
- Gramin Krishi Mausam Sewa (GKMS) – Launched 1988 by IMD & ICAR.
- All-India Agromet Advisory Bulletin – Released twice weekly by IMD.
- District Agromet Units (DAMUs) – Provide local forecasts through KVKs.
- INSAT (Indian National Satellite System) – Used for weather and crop monitoring.
- Kalpana-1 satellite – India’s first exclusive meteorological satellite.
- METSAT/INSAT-3A – Provides meteorological and oceanographic data.
- ISRO (Indian Space Research Organisation) – Supports remote sensing for agromet.
- Agro-climatic zonation of India – 15 zones (Planning Commission 1988).
- Agro-ecological regions of India – 20 regions (ICAR-NBSS&LUP).
- ICAR-CRIDA (Hyderabad) – Central Research Institute for Dryland Agriculture, nodal center for agromet research.
- ICAR-NIASM (Baramati) – National Institute of Abiotic Stress Management.
Weather Forecasting Facts
- Short-range forecast – Up to 2 days.
- Medium-range forecast – 3–10 days.
- Long-range forecast – More than 10 days.
- Now-cast – For the next 0–6 hours.
- Numerical Weather Prediction (NWP) – Forecast based on mathematical models.
- Statistical forecast – Based on historical weather data.
- Ensemble forecasting – Combines multiple model outputs for accuracy.
- IMD uses NWP models like – WRF, GFS, and MM5.
- Accuracy of medium-range forecast in India – About 70 %.
- Forecast dissemination – Through SMS, TV, radio, and Kisan Call Centre (KCC-1551).
Climate and Crop Relationship
- Climate is the deciding factor for crop distribution.
- Weather affects all growth stages of crops.
- Wheat requires cool and dry climate; Rice requires warm and humid.
- Sugarcane – Tropical climate with 1000–1500 mm rainfall.
- Cotton – Requires 20–30 °C and 50–100 cm rainfall.
- Groundnut – Requires 25–30 °C and moderate rainfall.
- Maize – Optimum temperature 25–35 °C.
- Frost damage occurs below 0 °C.
- High humidity favors fungal diseases.
- Drought and heat stress reduce yield drastically.
Miscellaneous Quick Facts
- Atmospheric window for remote sensing – 8–14 µm.
- ENSO full form – El Niño Southern Oscillation.
- Normal Lapse Rate – 6.5 °C per km.
- Dry adiabatic lapse rate – 9.8 °C per km.
- Moist adiabatic lapse rate – 6 °C per km.
- Standard pressure at sea level – 1013.25 mb.
- Relative humidity formula: RH = (actual vapor pressure / saturation vapor pressure) × 100.
- Base temperature for wheat – 5 °C; for maize – 10 °C; for rice – 10 °C.
- Radiation balance equation: RN = (S↓ − S↑) + (L↓ − L↑).
- 1 calorie = 4.184 joules.
