TLDR;
Alright folks, this session is all about acing your agronomy game! We're diving deep into agrometeorology, covering everything from basic definitions to radiation, albedo, important instruments, and atmospheric layers. Key takeaways include understanding PAR, how to measure it, albedo concepts, and the different layers of the atmosphere along with their characteristics.
- Agrometeorology definitions and importance
- Radiation, albedo, and related instruments
- Key meteorological days and themes
- Atmospheric layers and their characteristics
Introduction [1:04]
The session is an agronomy crash course, focusing on agrometeorology. It aims to cover all important aspects, including previous year questions (PYQs) and new questions for exams like ICAR-PG. The lecture will be a one-shot deal, covering theory and questions.
Agrometeorology Basics [4:32]
Agrometeorology is a branch that deals with weather phenomena. Meteorology is a Greek word related to physics. Climate is a long-term statistical average of weather conditions, while weather is at any point of time. Macroclimate refers to the climate of a large geographic area, while microclimate refers to the climate from the top of the plant canopy to the rhizospheric zone.
Key Figures in Meteorology [7:35]
Climatology is the study of climate, derived from Greek words. Luke Howard is the father of meteorology in the world. A.K. Wali is the father of agrometeorology in the world, and Professor L.A. Ramdas is the father of agrometeorology in India. Köppen is associated with climatology.
Radiation and Albedo [9:23]
Incoming solar radiation has a shorter wavelength and higher frequency. Plants utilize the visible spectrum, which is about 42% of solar radiation, known as PAR (Photosynthetically Active Radiation). Diffuse radiation is better for plants, with about 65% PAR. PAR is measured using a quantum sensor. Albedo is the reflection of solar radiation without a change in quality, expressed as a fraction or percentage. Fresh snow has a high albedo (0.75 to 0.90), while a black body has an albedo of 0. Albedo is measured using an albedometer or reflectometer.
Albedo and Soil [14:08]
Tilled soil, which is darker, has lower albedo due to higher absorption, while untilled soil, which is lighter, has higher albedo due to more reflection. Ridging decreases albedo because radiation gets trapped in the furrows and doesn't reflect back as much as from a flat surface.
Instruments for Measuring Weather Parameters [17:47]
Pyreheliometer is used to measure direct solar radiation. Pyranometer measures both direct and diffuse radiation. Shading pyranometer measures only diffuse radiation. Hygrometer measures relative humidity. Barograph measures continuous atmospheric pressure.
Instruments and PAR [20:59]
Shortwave radiation includes both direct and diffuse components. Hygrometers are used for measuring relative humidity. Infrared thermometers are typically handheld devices. Direct solar radiation contains 42% PAR, while diffuse radiation contains 65% PAR. Anemometers measure wind speed, and wind vanes measure wind direction. The heights of instruments like sunshine recorders, anemometers, and wind vanes are important to remember, with a standard height of 3.08 meters.
Important Meteorological Days [23:38]
World Water Day is on March 22nd, followed by World Meteorological Day on March 23rd. World Forest Day is on March 21st. The theme for World Meteorological Day was "Closing the early warning gap together". International Literacy Day is on September 8th, and International Day for the Elimination of Racial Discrimination is on March 21st.
Atmospheric Layers [26:04]
The layers of the atmosphere, in order, are troposphere, stratosphere, mesosphere, thermosphere, and exosphere. The troposphere is the lowest layer where all weather phenomena occur. The mesosphere is the coldest layer. The thickness of the troposphere varies from 18 km at the equator to 8 km at the poles, with an average of 13 km. The stratosphere contains a layer that absorbs ultraviolet radiation.
Layer Properties and Boundaries [28:20]
The stratosphere extends up to 50 km, the mesosphere up to 80 km, and the ionosphere (part of the thermosphere) up to 640 km. The exosphere has no defined end. Airplanes typically fly above the troposphere. Tropopause, stratopause, and mesopause are the boundaries separating these layers. The troposphere experiences turbulence, while the stratosphere has a temperature around 0 degrees Celsius, with temperature increasing with altitude. In the troposphere, temperature decreases with altitude at the normal lapse rate.
