Meaning of Weather and Climate

Knowledge of agrometeorology is useful in several aspects of practical agriculture as indicated below:
1. It has practical utility in timing of agricultural operations so as to make the best use of favourable weather conditions and make adjustments for adverse weather.
2. The dangers of crop production due to pest and disease incidence, occurrence of prolonged drought, soil erosion, frost and weather hazards can be minimised.
3. Weather support also provides guidelines for long range or seasonal planning of crops and cultivars most suited to anticipated climatic conditions.
4. Agrometeorological information can be used in land use planning, risk analysis of climatic hazards, production and harvest forecasts and linking similar crop environments for crop adaptability and productivity.
Climatic parameters are determined, primarily, by geographic factors such as:
1. Latitude.
2. Altitude.
3. Distance from large water bodies.
4. Ocean currents.
5. Intensity of wind.
All the above climatic parameters influence the wind. Three geographic factors—altitude, latitude and longitude are important for crop production. These are embodied in Hopkin Bioclimatic Law. It states that crop production activities (planting to harvest) and specific morphological developments are delayed by 4 days for each 1° latitude, 5° longitude and 12 m (40 ft) of altitude as one move northward and upward, respectively.
Intensity, velocity and direction of wind vary with three geographic factors leading to variation in climate and weather.
Geographic surface features such as large bodies of water and mountain ranges modify the wind characteristics and hence the meteorological parameters. A mountain range in the path of prevailing wind creates moist conditions on the windward side and dry conditions on the leeward side. Air cools adiabatically to the dew point as it rises up the mountains.
The air that is forced upward by the mountain range loses its moisture and becomes a dry mass when it goes over the top. This is called the orographic effect (relief effect), which is different from the usual rainfall without mountains. Topography influences weather and microclimate through variation in temperature and wind.
Water is normally warmer than the surrounding land. When wind blows over a large body of water, it picks up moisture, thus creating a more moderate leeward condition. The leeward side of the body of water is subjected to less temperature fluctuations (relatively stable weather) compared to windward side. Windward side is suitable for drought tolerant crops and leeward side to relatively drought sensitive crops. North facing and south facing slopes may differ in climate and natural vegetation. These sites differ in crops that can be grown. World climate is not static but is subjected to changes caused by factors such as systematic changes in solar activity, sea level, atmospheric carbon dioxide and continental drift. Continental drift gradually changes the latitudinal position of the land masses and the sea level. Volcanic explosions discharge large amounts of dust and gases into the atmosphere. This may cause a decline in temperature (reverse of greenhouse effect). Accumulation of greenhouse gases is responsible for global warming (gradual increasing trend in global average temperature largely due to greenhouse effect). In spite of technological advances in modern crop production, crop production is still subject to the vagaries of the weather that are manifested in three main ways— moisture stress, temperature stress and natural disasters. Cold temperatures place physiological stresses on the body, the more healthy and fit you are, the more easily your body can cope with these stresses. Dressing properly is the key to being healthy in a cold climate. Avoiding undue stresses particularly if you are not seasonally acclimatized to the cold is also important, especially in the very old, the very young and those with an underlying health condition all of whom should have the home heated to at least 18C (64F).