Agricultural Meteorology Point Wise Notes For Competitive Exam

• Modification of weather, except to a limited extent, is difficult and uneconomical.

• We can get higher crop yields by adjusting cropping patterns and by following suitable agronomic practices to mitigate the adverse effects of weather.

• Weather is a state or condition of atmosphere at a given place and at a given time.

• Weather is daily variations or conditions of lower layers of atmosphere.

• Weather pertains to smaller area like village, city, or even a district and smaller duration of time i.e., part of a day or complete day.

• Weather is expressed by numerical values of meteorological parameters.

• Examples of weather are hot day, rainy day, cloudy weather, dry weather etc.

• Climate is generalized weather or summation of weather conditions over a given region during a comparatively longer period.

• Climate is weather conditions related to larger areas like zone, state, country, part of continent or whole of continent, longer duration of time like month, season or year.

• Climate is expressed by normals and averages e.g., cold season, tropical climate etc.

• Meteorology is the science that deals with laws and principles as they apply to atmospheric phenomenon.

• Meteorology is the science of atmosphere and its attendant activities.

• Meteorology also defined as a branch of physics that deals with physical process in the atmosphere that produce weather.

• Agricultural meteorology is a branch of applied meteorology which deals with response of crops to the physical environment.

• Agriculture meteorology is the study of physical process of the atmosphere that produces weather in relation to agricultural production, and also deals with agroclimatology, instrumentation and weather forecasting.

• Climatology is the science dealing with the factors which determine and control distribution of climate over the earth’s surface.

• Agroclimatology deals with relationship of climatic regimes and agricultural production. It also includes instrumentation and weather forecasting.

• Atmosphere extends up to a height of about 1600 km.

• 99 per cent of total atmospheric mass is within 40 km from the surface of earth.

• Volume of Nitrogen in atmosphere is 78%.

• Weight of Nitrogen in atmosphere is 75.5%.

• Volume of Oxygen in atmosphere is 21%.

• Weight of Oxygen in atmosphere is 23.1%.

• Volume of Argon in atmosphere is 0.93%.

• Weight of Argon in atmosphere is 1.28%.

• Volume of Carbon dioxide in atmosphere is 0.03%.

• Weight of Carbon dioxide in atmosphere is 0.045%.

• Volume of water vapour in lower layer of atmosphere is 0 to 4%.

• Based on vertical temperature differences atmosphere is divided into 4 layers i.e., troposphere, stratosphere, mesosphere and thermosphere.

• Troposphere is the lower layer of atmosphere.

• Troposphere extends up to a height of 8 to 18 km from earth surface depending on latitude.

• Troposphere is thicker at equator than poles.

• Troposphere contains 85% of atmospheric mass.

• Weather phenomenon like clouds, fog, dew, mist, rain etc. occur in troposphere.

• Temperature decreases with increase in altitude of troposphere.

• Temperature at the boundary of troposphere is -60 oC.

• Tropopause is a thin layer between troposphere and stratosphere.

• Temperature does not vary with height in tropopause.

• Stratosphere layer lies above tropopause.

• Stratosphere lies beyond 8 to 18 km extending up to 50km depending on latitude.

• Stratosphere is dustless, cloudless and warmest layer.

• Temperature increases with height in stratosphere.

• Stratosphere contains 15% of atmospheric mass.

• Stratosphere has low density of gases.

• Mass of air up to 40 km is more than 99% of total atmospheric mass.

• Stratosphere absorbs ultra violet radiation of the sun.

• Stratosphere air does not move above, because air at higher altitude is warmer than air below.

• Stratopause separates stratosphere and mesosphere.

• Mesosphere is the layer that lies above stratosphere.

• In mesosphere temperature decreases with increase in altitude up to 80km.

• Mesopause separates mesosphere from thermosphere.

• Thermosphere is the outer layer of atmosphere.

• Temperature increases with altitude in thermosphere.

• Ionosphere is the lower layer of thermosphere through which long distance radio communication is possible.

• Solar constant is defined as the energy falling in one minute on a surface area of one square centimeter at the outer boundary of atmosphere held normal to the sunlight at the mean distance of the earth from the sun.

• Value of solar constant is 1.94 cal /cm2/min.

• Direct solar radiation is the radiation received directly from sun by a surface normal to the incident radiation.

• Diffused radiation or sky radiation is the radiation scattered by suspended particles in the atmosphere.

• Quantity of diffused radiation depends on latitude, season and cloudiness.

• In high latitudes diffused radiation is important source of solar radiation and forms substantial part of solar radiation during winter months.

• Cloudiness increases ratio of diffused to direct radiation.

• Before sunrise and after sunset all the solar radiation received is diffused or sky radiation.

• In plant canopies diffused radiation penetrates effectively than direct radiation.

• Diffused radiation contains 65% photosynthetically active radiation (PAR).

• Direct radiation contains 42% photosynthetically active radiation (PAR).

• Global radiation is the total of direct and diffused solar radiation received on a horizontal surface from the sun directly and from the sky as scattered radiation.

• Albedo or reflected solar radiation is the solar radiation that is reflected without any change in its quality.

• Clouds are effective reflectors of solar radiation.

• Snow is a very effective reflector, particularly when it is fresh.

• Water surfaces and sea are poor reflectors.

• Rocks, sand, soil and vegetation reflect from 10 to 30 per cent of the incident solar radiation.

• Reflected solar radiation is important in remote sensing.

• Terrestrial radiation is the thermal radiation emitted by the earth.

• Earth absorbs solar radiation in short waves and emits back in the form of long waves.

• Terrestrial radiation heats the atmosphere.

• Net radiation is the radiation balance between global and reflected solar radiation.

• SI unit of solar radiation is watts/m2