In this article we will discuss about the meaning and classification of agro-meteorological observatory.
Meaning of Agro-Meteorological Observatory:
Agro-meteorological observatory is a place where all the necessary instruments are maintained to observe and record different weather elements/parameters at stipulated time interval. When the observations are recorded for a sufficiently long time and analysed statistically, reliable crop-weather relations can be obtained.
Hence, an agro-meteorological observatory is essential to record the weather phenomena for understanding crop-weather relationships leading to improvement in crop productivity.
To ensure that the observations are representative of the place and comparable with those made at other observatories, the observatory site selection should meet the following basic requirements:
1. The site should be representative of the surrounding area.
2. The observatory, as far as possible, should be at the centre of the farm.
3. The observatory should be free from water-logging during rainy season and easily accessible.
4. It should be away from irrigation channels and tall structures such as buildings, trees and mountains. If these structures occur, the site should be at a distance of 10 times the height of such obstacles.
5. The site should be levelled without any sloppy land.
6. The site should be selected once for all.
Ideal site for an observatory is a well exposed, bare, levelled plot of size 60 m (N-S) x 40 m (E-W) located more or less at the center of the farm. The observatory plot should be enclosed with barbed wire fence up to 1.2 m height, to avoid trespasses.
A gate at appropriate location in the barbed wire fence has to be provided. In general, agro-meteorological observatories are most commonly set up in all Agricultural Universities under the technical guidance of IMD, Pune.
Classification of Agro-Meteorological Observatory:
Climatological observatory is meant for studying the effect of climate. Synoptic observatory is maintained for the study of weather. Agro-meteorologocal observatory is maintained for agricultural research.
Agro-meteorological Observatory in India are classified as indicated below:
Depending on the availability of instruments and number of weather elements observed, agro-meteorological observatories are classified into 3 major (ABC) and 2 minor (DE) groups (classes). Class A, B and C observatories are provided with both eye reading and self-recording instruments. Observations in Class A observatories are at an interval of three hours in a day, from Class B thrice daily and from Class C once in a day.
1. A-Type Observatory:
The A-Type or Principal Agro-meteorological Observatory is located at Pune (Maharashtra).
Its main activities include:
1. Recording large number of meteorological parameters of interest to agriculture (routine work).
2. Experimental work at the principal meteorological observatory.
3. Coordinating All India Coordinated Crop-Weather Projects on different crops, weather service to farmers and issue of monthly crop outlooks.
4. Rendering technical assistance to state departments of agriculture.
5. Preparation of Agro-climatic Atlases of India and measurement of evaporation.
6. Publishing crop-weather data and crop-weather diagrams.
7. Collaborates with WMO in the field of agro-meteorology and allied disciplines.
Self-recording instruments record most of the data on continuous basis. These are supported and supplemented by spot observations at 0700 and 1400 hr local mean time (LMT) and by synoptic hours of 0830 and 1730 IST.
Calculation of Local Mean Time:
The surface of the earth is divided into 24 time zones, the way in which there are 24 hours in a day. The time established in each zone is ‘standard time’. The Indian Standard Time (IST) is the Local Mean Time (LMT) for the longitude of 82°50′ E, which passes through Allahabad. The LMT is based on the transit of the mean sun. To calculate LMT from IST, it is essential to know the longitude of the station.
The relation between IST and LMT is as follows:
LMT = IST — 4 (λs — λ)
where, λS= standard longitude (82°50′ E) passing over Allahabad
λ = longitude of the station for which local time is calculated.
2. B-Type Observatories:
The B-type observatories or Ordinary Agro-meteorological Observatories provide, on routine basis, meteorological and biological information.
The meteorological elements observed at these stations include:
a. Rainfall.
b. Air and soil temperature.
c. Humidity.
d. Soil moisture.
e. Wind.
f. Pan evaporation.
g. Sunshine.
h. Occurrence of weather phenomena (storms, frost, high wind etc.).
The observations are recorded at 0700 and 1400 hrs LMT. However, rainfall and evaporation observations are recorded at 0830 hrs IST and 1400 hrs LMT.
There are two types of observatories in this category:
1. Crop-weather observatories.
2. Non crop-weather observatories.
Crop-Weather Observatories:
These observatories record side-by-side meteorological data on growth and yield of one or more of the major crops (rice, sorghum, wheat, cotton, sugarcane) according to standard plan. The data are sent to Agromet Division, Pune, where these are compiled and weather relationships will be drawn.
Non Crop-Weather Observatories:
This class includes:
a. Agro-meteorological observatories located at soil conservation research and demonstration centres.
b. Agro-meteorological observatories located at agricultural schools, colleges and universities.
c. Agro-meteorological observatories located at agricultural research farms and allied centres for meeting their requirements.
The National Agricultural Research Project (NARP) divided the country into 129 agro-climatic zones, with a Regional Agricultural Research Station (RARS) for each agro-climatic zone. An ordinary agro-meterological observatory was established at each RARS. Data on rainfall, air temperature, duration of sunshine, humidity, soil temperature (5, 15, 30 cm), wind velocity and direction, evaporation and dew are being collected at these observatories.
Instruments Required for Ordinary Observatory:
Meteorological instruments/equipment for an ordinary observatory are given below:
Essential instruments:
1. Dry-bulb thermometer
2. Wet-bulb thermometer
3. Maximum thermometer
4. Minimum thermometer
5. Single Stevenson screen
6. Rain gauge (non-recording)
7. Soil thermometers (5, 10, 15 cm)
8. Wind vane
9. Anemometer
10. Class A open pan evaporimeter
11. Assmann psychrometer
12. Soil moisture equipment
Optional Instruments:
1. Sunshine recorder
2. Dew gauge
3. Self-recording rain gauge
4. Thermograph
5. Hair hygrograph
6. Double Stevenson screen
The instruments are installed in the observatory in a specified sequence according to height of the instruments and path of the sunrays. As for as possible, the taller instruments should be placed in the farther side and shorter ones in the nearer side of the gate. Lay out of B-Type agro-meteorological observatory is depicted in Fig. 2.1.
3. C-Type Observatories:
The C-type observatories or Auxiliary Agro-meteorological Observatories send qualitative data on phenology and pests and diseases. These observatories are, usually, agricultural farms. Functions of such observatories are of general type.
Major functions, among others, include:
1. Training of observers.
2. Advising agricultural departments on specifications of standard meteorological equipment testing and repairing such equipment etc.
3. Periodical inspection of observatories for advises, corrections etc.
4. Preparation and issue of technical circulars and standard forms for recording observations.
5. Instructions to observatories for proper collection and tabulation of data in standard forms.
The D-type or Pilot Balloon-cum-Micro Meteo Stations were started under desert locust meteorology scheme. They provide low-level winds to assist in the issue of anticipated wind for antilocust observations. The IMD handles E-Type or Evapotranspiration Stations for measuring evapotranspiration by using lysimeter.