Agrometeorology

Agrometeorology a specialised branch of meteorology, the science dealing with the atmosphere and its phenomena, including weather and climate. Agrometeorology is concerned with interactions between meteorological and hydrological factors on the one hand, and agriculture in the widest sense, including horticulture, animal husbandry, and forestry, on the other. Its objective is to discover and define such effects, and thus to apply knowledge of the atmosphere for practical agricultural use. In addition to the climate, and its local variations, agrometeorology is also concerned with artificial modifications in environment such as windbreaks, irrigation, glass-houses, land use, etc.

Agrometeorology deals extensively with weather and climate. Generally speaking, weather refers to the instantaneous state of the atmosphere, particularly with respect to radiation, temperature, air pressure, wind, humidity, cloudiness, precipitation, evaporation, dew, and visibility. Climate, on the other hand, refers to the statistical collective of weather elements over a given place during a long period of time, usually in the order of several decades. Climate includes not only the averages or mean values of weather elements but also their variabilities about the mean. So, weather varies from day to day, and climate varies from place to place. Climate determines what crops we can grow, and weather determines the yields we get. There are several types of agricultural management decisions which involve weather chain interactions from day to day decisions to long-term planning.

Agrometeorological workon Bangladesh is very limited. However, recently the Bangladesh Meteorological Department (BMD) established 12 agrometeorological stations over the country where agrometeorological data are collected. BMD also performs 3 types of weather forecasts for agriculture viz, (i) short range forecast (up to 48 hours), (ii) medium range forecast (up to 10 days), and (iii) long range forecast (>10 days). Each has a role to play in farm operations and planning of agricultural activities. In 1976, the bangladesh rice research institute (BRRI), Gazipur and the International Rice Research Institute (IRRI), Philippines, jointly published the 'Agroclimatic Survey of Bangladesh'; to describe the characteristic features of the climatic regimes of the country. Later on, UNDP/FAO in collaboration with bangladesh agricultural research council (BARC), Dhaka, in 1988 published Land Resources Appraisal of Bangladesh, where agroclimatic zones of Bangladesh are defined and delineated.

Available climatic data for 30 principal stations of the Bangladesh Meteorological Department and for 177 rainfall stations of the bangladesh water development board were compiled, reviewed and analyzed for the land resources appraisal. The superimposition of the moisture and thermal zones create a total of 92 agroclimatic zones. Each agroclimatic zone has a unique combination of characteristics. Superimposed over the agroecological regions and subregions, these zones create a total of 535 agroecological units in the country. The agroclimatic zones have also been superimposed over the soil associations and they provide the framework for the agroclimatic ratings of crop suitability. Land Resources Appraisal of Bangladesh are now being updated with recent data on various aspects of agriculture (including climatic data) under the AEZ/GIS project at BARC. [Md. Serajul Islam]