Absolute Humidity: Grams of water vapour per cubic meter.

Actual Vapour Pressure: Pressure exerted by water vapour contained in the air; unit millibar (mb) or mm of Hg.

Advection: The process of transfer (of an air-mass property) by virtue of motion.

Advection Fog: Fog formed by passage of relatively warm, moist and stable air over a cool surface.

Aerodynamic: Refers to forces of moving air acting upon the soil or crop surface.

Aerosol: In meteorology , an aggregate of minute particles(solid or liquid ) suspended in the atmosphere.

Agroclimatic Region: The grouping of different physical areas within the country into broadly homogeneous zones based on climatic and edaphic factor .

Agroecological Zone: A major area of land that is broadly homogeneous in climatic and edaphic factors , but not necessarily continuous , where a specific crop exhibits roughly the same biological expression.

Agro-ecosystem: It is composed of the total complex of the crop / animal in an area together with overall environment and as modified by management practices.

Agro-ecology: The study of the relation of agricultural crops & environment.

Agrometeorology: Meteorology relevant to problems of agriculture. It is concerned, in particular, with the surface layer of the atmosphere and with the condition in the top layer of the earth's surface which are associated with the variations of the meteorological element.

Air-mass: A body of the air in which horizontal gradient of temperature and humidity are relatively slight and which is separated from an adjacent body of air by a more or less sharply defined transition zone.

Albedo: It is the ratio of the amount of visible light reflected by a body to the amount incident on it.

Alpha Radiation: The radiation consist of alpha particle emitted by certain radioactive elements.

Altitude: Vertical distance of a level , a point or an object considered as a point measured from mean sea level.

Ambient Temperature: The temperature of surrounding atmospheric air.

Anomaly: The departure of an element from its long period average value for the place concerned.

Aneroid Barometer: An instrument used for measuring atmospheric pressure. It's main advantage over a mercury barometer is its portability.

Anticyclone: The atmospheric pressure distribution in which there is a high central pressure relative to the surroundings.

Atmospheric Pressure: The pressure exerted by the atmosphere as a consequences of the weight of the air lying directly above the unit area . At sea level atmospheric pressure is equal to 76 cm Hg column.

Available Moisture: It is the moisture range or limit available to plants which lies between field capacity and wilting point of a soil.

Backing :The changing of the wind in a counter-clockwise direction, in either hemisphere.

Baroclinic: A baroclinic atmosphere is one in which surfaces of pressure and density intersect at some level or levels.

Baroclinic instability: A type of dynamic instability , associated with a strongly baroclinic region of the atmosphere.

Barograph: A self recording barometer in which continuous trace of the atmospheric pressure is made on a barograph .

Barometer: An instrument used for measuring the atmospheric pressure.

Barotropic: A barotropic atmosphere is that hypothetical atmosphere in which surface of pressure and density coincide at all levels.

Barotropic wave: A wave-like disturbance in a barotropic atmosphere.

Boundary Layer: That layer of fluid adjacent to a physical boundary in which the fluid motion is much affected by the boundary and has a mean velocity less than the free-stream value.

Calm: Absence of appreciable wind: On the Beaufort Scale of wind force calm is accorded the figure 0 and has a wind speed equivalent or less than 1 knot.

Cat: Abbreviation of Clear Air Turbulence.

Catchment area: Defined for the administrative purposes as the area within the jurisdiction of a catchment board .

Charles's law: At constant pressure , the volume of a given mass of gas is directly proportional to the absolute temperature.

Circulation: The circulation round a closed curve is defined as the line integral round the curve of the velocity vector component along the curve i.e.

Cirrocumulus (Cc): Thin , white patch , sheet or layer of cloud with out shading, composed of very small elements in the form of grains ,ripples, etc merged or separate, and more or less regularly arranged; most of the elements have an apparent width of less than one degree.

Cirrostratus (Cs): Transparent , whitish cloud veil of fibrous(hair-like) or smooth appearance ,totally or partly covering the sky and generally producing halo phenomena.

Cirrous (Cc): Detached cloud in the form of white ,delicate filaments or white or mostly white patches or narrow bands . These clouds have a fibrous (hair-like) appearance, or a silky sheen, or both.

Climatology: The study of weather pattern over time and space . It concerns the integration of day to day weather over a period of time .

Cloud-burst: A popular term for a very sudden and very heavy shower, often accompanied by thunder and hail . It is associated with strong upward and downward current.

Cloud Cover: Visible aggregate of minute particles of liquid water or ice or both together in suspension in the atmosphere.

The following terminology are used in practice for reporting the cloud cover

Cloudiness: Degree of cloud cover usually mean of several observations per day; exposed in octal (in eight) of sky cover or intents of sky covered.

Cloud Seeding: Injecting the clouds with seeding agent like dry ice, silver iodide, sodium chloride from an aircraft or using a ground generator for producing artificial rain.

Cold fog: Cold fog occurs during winter in cool , moist, temperate latitude when extremely low temperatures (up to -30 0C) occur , resulting in ice fog of small particles.

Cold Wave: Criteria for describing departure from normal .

(i) When normal minimum temperature of the area is 10 0C or more

(ii) When normal minimum temperature of the area is less than 10 degree.

Condensation: The process of formation of liquid from its vapour.

Convective Rain: Rainfall which is caused by the vertical motion of an ascending mass of air which is warmer than its environment; the horizontal dimension of such an air mass is generally of the order of 15 kilometers or less and forms a typical cumulonimbus cloud.

Crop: Refers to a plant swan and harvested by man for economic purposes.

Crop calender: A list of the standard crops of a region in the form of a calendar giving the dates of sowing and various operations including harvesting to be done during the crop seasons in years of normal weather.

Crop Efficiency Zone: A geographical area characterized by high spread of a crop combined with high yields consistent with minimum variations from year to year.

Crop Environment: A crop environment may be regarded as having two components, the gross environment which takes into account all environmental factors affecting crop growth and the current environment which take into account the general soil and atmospheric conditions outside the crop, and also the changes of those general conditions caused by the plant.

Crop Evapo-transpiration: Rate of evapo-traspiration of a diseases free crop growing on a large field under optional soil conditions, including sufficient water and fertilizer and achieving full production potential of the crop under the given growing environment; includes water loss through transpiration by the vegetation, and evaporation from the soil surface and wet leaves, mm/day

Crop Modeling and Simulation: Crop modeling and simulation is a simplified representation of a more complex reality in crop modeling system. Simulation is the operation or manipulation of a model of system to estimate the consequence of selected strategies or combination of input variables.

Crop Season: The most favorable conditions to get better yield.

Crop Yield Index: A measure of comparison of the yields of all crops on a given form with the average yield of these crops in the locality. The relationship is expressed in percentage.

Croping Index: The number of crops grown per annum on a given area of land times 100.

Cumulative Run Off: The total volume of run of ever a specifies period of times.

Cyclonic Motion: If the motion of air is in the counter clockwise direction round the center in northern hemisphere is called cyclonic motion.

Dairy Husbandry: The core, breeding, feeding, and milking of dairy cattle and production and sale of milk .

Deepening: In synoptic meteorology , 'deepening' of a depression signifies a decrease of pressure at a center of the system with time.

Degree Day: It is measurement of the departure of the daily temperature above the minimum threshold temperature for a crop or plant.

Departure: The amount positive and negative, by which the value of a meteorological element departs from the normal , average or expected value of a place and time . It is also termed as anomaly.

Development: In synoptic meteorology , the intensification of circulation, cyclonic or anticyclonic.

Dew: Condensation of water vapour on a surface whose temperature is reduced by radiational cooling to below the dew-point of the air in contact with it.

Dew-point: The dew-point temperature ( Td ) of a moist air sample, commonly termed simply the dew-point , is that temperature to which the air must be cooled in order that it shall be saturated with respect to water at its existing pressure and humidity.

Drizzle: Rainfall in which water drops are very small ranging from 0.2 to 0.5 mm in diameter.

Drosometer: Instrument for measuring dew deposit. It is also termed as Oetalies dew gauge.

Drought: The moisture deficit which results when the amount of water vapour available in the soil is not sufficient to meet the demand of potential evapotranspiration.

Drought Year: Drought year is that year in which rainfall of particular place is short by more than twice the standard deviation.

dry air: In physical meteorology this term generally signifies air which is completely dry, i.e. which contains no water vapour.

dry land forming: The practices of crop production entirely with rain water received during the crop season or on conserved soil moisture in low rainfall ( less than 800 mm) area of arid and semiarid climate and crop may face mild to very sever moisture stress during their life cycle.

dry season: A period of a month or more, recurring every year, which is marked in a given region (generally tropical or sub-tropical) by the complete or almost complete absence of precipitation.

dry spell: A period of at east 15 consecutive days , during which not a single wetting rain has fallen .

Duststorm: An ensemble of particles dust or sand energetically lifted to great height by a strong and turbulent wind.

Eco Climate: Climate under crop canopy is called eco-climate.

Elevation: In Meteorology, term used to denote the height of the ground above mean sea level.

Enthalpy: A thermodynamic quantity which represents the 'total heat' content per unit mass of a substance; the units normally employed are joules per kilogram.

Equatorial Trough: The shallow trough of low pressure, generally situated on or near the equator, marking the convergence zone of air which moves equatorwards from the subtropical anticyclones of either hemisphere.

Evaporation: In meteorology , the change of liquid or ice to water vapour. The rate of evaporation is controlled by water and energy (mainly solar radiation) supplies and by the ability of the air to take up more water.

Evaporation Fog: Fog which is formed by evaporation of relatively warm water into cool air .

Evapotranspiration: The combined processes of evaporation from the earth's surface and transpiration from the vegetation.

Extinction Coefficient: The extinction coefficient is defined as the ratio between the light loss through the leaf to the light at the top of the leaf.

Fog: Obscurity in the surface layer of the atmosphere, which is caused by a suspension of water droplets, with or without smoke particles, and which is defined, by international agreement, as being associated with visibility less than 1 km.

Fog Precipitation: Fog precipitation, sometimes also termed 'fog drip', signifies the precipitation of liquid water from non-bearing cloud due to the interception of the cloud particles by trees and other vegetation.

Forecast: The term, first applied in meteorology by Admiral FitzRoy, which signifies a statement of anticipated (meteorological ) conditions for a specified place (or area , route, etc. ) and period of time.

Geopotential: The potential energy per unit mass of a body due to the earth's gravitational field referred to an arbitrary zero.

Gust: A rapid increase in the strength of the wind relative to the mean strength obtaining at the time. It is much short-lived than a squall and is also different in nature.

Growing Season: Period of the year during which the growth of vegetation proceeds.

Hail: Solid precipitation in the form of balls or pieces of ice (hailstones) with diameter ranging from 5 mm to 50 mm or even more.

Hail Storm: A storm, often too long and severe, consisting largely of hail or frozen rain drops ranging in diameter from 5 mm to 10 mm or more.

Harvest Index: Yield of the plant parts of economic interest (economic yield as percentage of total biological yield in terms of dry matter).

Heat Wave: Criteria for describing departure from normal

(i) When normal maximum temperature of the area /station is 40 0C or less

(ii) When normal maximum temperature is more than 40 0C degree C.

(iii) When maximum temperature remains 45 0C or more for two days or more the condition may be described as heat wave.

Humidity: The condition of atmosphere in respect of its water vapour content.

Hydrological cycle: The study of the incidence and properties of water on and within the ground, including that held in rivers and lakes. It comprises studies of rainfall, evaporation, run-off, ground water, soil moisture, the hydrological balance, snow and ice accumulation, and chemistry of natural water.

Insolation: The intensity at specific time or the amount in a specified period , of direct solar radiation incident on unit area of a horizontal surface on or above the earth's surface.

Inversion: An inversion (of temperature) is said to occur at a point, or through a layer, at which or through which temperature increases with increasing height.

Isallobar: A line of constant barometric tendency. Such lines are drawn on synoptic charts, mainly as an aid to forecasting the movement of features of the pressure distribution.

Isobar: A line of constant pressure.

Isohyet: A line drawn on a map connecting points with equal rainfall.

Isopleth: A line of equal value of given quantity.

Isotach: A line of equal wind speed .

Isotherm: A line of equal temperature.

katabatic Wind: Down slope gravitational flow of the colder, denser air beneath the warmer , lighter air results and comprises the katabatic wind. It is also known as the drainage wind or mountain wind.

Knot: A speed of one nautical mile per hour and approximately 0.5 m/s.

Latent Heat: The quantity of heat absorbed or emitted, without change of temperature, during a change of state of unit mass of a material; it has normally been expressed in the unit cal/gm.

Lapse Rate: The rate at which temperature decreases in a rising and expanding air parcel.

Leeward: Leeward of a point signifies the 'downwind' direction from the point.

Lightening: A visible electric discharge (lightening flash) associated with a thunderstorm.

Long-wave Radiation: In its usual meteorological usage , an alternative for terrestrial radiation.

Lysimeter: An instrument for measuring the rate of percolation of rain through a soil.

Mean Sea Level: Mean plain at which the tide oscillates the average height of the sea for all stages of the tide. At any particular place, it is derived by averaging the hourly tide heights over a 19 years period.

Melting Point: That temperature , characteristic of given substance at a given pressure, at which the change of state from solid to liquid occurs.

Meridional Flow: Airflow in the direction of the geographical meridian i.e. south north or north-south flow.

Microclimate: The physical state of the atmosphere close to a very small area of the earth's surface , often in relation to living matter such as crops or insects.

Minimum Temperature: The lowest temperature attained , usually in the thermometer screen or on the ground, during a period of time.

Mist: A state of atmospheric obscurity produced by suspended microscopic water droplets or wet hygroscopic particles. The term used for synoptic purpose when visibility is equal to or exceeds 1 km ; the corresponding relative humidity is greater than 95 percent.

Mixed Croping: Growing of two or more crops simultaneously on the same piece of land, without any definite row arrangement.

Moist Air: A term which usually signifies simply a mixture of dry air and water vapour. In synoptic meteorology and climatology the term is applied to air of high relative humidity.

Moisture Stress: The tension at which the water is held by the soil.

Monsoon: Derived from the Arabic word 'mausim' meaning 'season', the term originally referred to the winds of Arbian Sea which blow for about six month from the north-east and for six months from the south-west, but is now used also of other markedly seasonal winds.

Monsoon Strength : Specification for the description of strength of monsoon are given below :

a) over the ocean

b) over land area

C)

Multiple Croping: Growing two or more crops consecutively on the same field in the same year.

Net Photosynthesis: When photo synthesis is measured with correction for respiration.

Net Productivity: The arithmetic difference between calories produced in photosynthesis and calories lost in respiration.

Net Radiation: The net radiation is the difference between total upward and downwards flux, and is a measure of the energy available at the ground surface.

Nimbostratus (Ns): Gray cloud layer, often dark, the appearance of which is rendered diffuse by more or less continuously falling rain or snow, which in most cases reaches the ground.

Nor'wester: A violent , convective type of storm, often accompanied by a line-squall, which occurs in Bengal and Assam in the months of March to May. The storms are so named because of the their pronounced tendency to move from the north-west.

Numerical Weather Forecast: An objective forecast, in which the future state of the atmosphere is determined by the numerical solution of the basic theoretical equations involved. The calculations are so lengthy as to necessitate, in general, the use of the electronic computer.

Okta: Unit, equal to area of one eighth of the sky, used in specifying cloud amount.

Orographic cloud: Cloud which is formed by forced uplift of air over high ground. The reduction of pressure within the rising air mass produces adiabatic cooling and, if the air is sufficiently moist, codensation.

Orographic Rain: Rain which is caused, entirely or in major part, by the forced uplift of moist air over high ground. The formation of orographic cloud is followed, in the event of continued uplift of the air, by precipitation.

OverSeeding: In cloud seeding, the hypothetical artificial production of an excessive number of ice crystals.

ozone: The triatomic form (O3) of oxygen, of molecular weight 47.998, which is present in the atmosphere in very small amounts ranging from about 0.2 to 0.5 cm equivalent thickness at normal temperature and pressure.

Perfect Gas: A hypothetical gas which obeys the gas laws of Boyle and Charles perfectly. For practical purposes the gases which compose unsaturated air may be considered perfect gases.

Persistence: In meteorology, a term used of a synoptic feature or meteorological condition that is unusually long-lasting.

Persistence Forecast: A type of forecast, often used as a basis of comparison in the assessment of the success attained in forecasts made by conventional methods, in which the assumption is made that meteorological conditions during the forecast period will remain unchanged from those obtained at the beginning of the forecast period.

Precipitation: Total amount of precipitation ( rain , drizzle , snow , hail , fog, condensation , frost ) expressed in depth of water which would cover a horizontal plane if there is no runoff ,infiltration or evapo-transpiration .unit ; mm/day

Quasi-biennial Oscillation: A well-defined oscillation of the zonal wind component in the equatorial stratosphere, the 'period' being about 27 months. It is also termed 'stratospheric oscillation'. The range of the fluctuations, greatest at a level of about 25 km, decreases with distance from the equator. There is a phase lag from higher to lower levels. At a given level the phase does not appear to vary with longitude.

Radar: A system of detection and location of 'targets' which are capable of reflecting high-frequency radio waves (microwaves), generally in the wave length range from a fraction of a centimeter to some tens of centimeters.

Radiation Balance: The resultant flux of the solar and terrestrial radiation through a horizontal surface. It is considered positive in the flux downwards exceeds that upwards. It is also termed 'net radiation'.

Radiation Fog: A common type of fog which forms overland on nights characterized by light wind, clear sky, and moist air in the lower levels of the atmosphere.

Radiosonde: A small radio transmitter by means of which observations, usually of pressure, temperature and humidity, may be obtained from the upper atmosphere.

Rainfall: The total liquid product of precipitation or condensation from the atmosphere as received and measured in a rain gauge in past 24 hours at 03 UTC.

Classification of rainfall is as follows:

Rainfall Distribution: Spatial distribution of rainfall is highly variable. The following criteria are used in forecasting practices .

Rainfed Farming: Growing of field crops entirely with rainwater received during the crop season ( rainfall usually < 800 mm under humid and sub humid climate and the crops may face little or no moisture stress during their life cycle.

Ridge: A ridge (of high pressure), also termed a wedge, is and extension of an anticyclone of high-pressure area shown on a weather chart, corresponding with a ridge running out from the side of a mountain. It is the converse of a trough of low pressure and is generally associated with fine anticyclonic-type weather.

Sand Storm: An ensemble of particles of dust or sand energetically lifted to great heights by a strong and turbulent wind.

Saturate Soil: A saturated soil, is one in which all the soil pores, including those which in a healthy soil contain air, filled with water.

Saturated Vapour Pressure: The vapour pressure of a parcel of saturated air at a given temperature.

Savanna: The term applied to a type of tropical climate, with a wet and a dry season, in which the most common form of vegetation is the tall tropical grass 'savanna'.

Seasonal Consumptive Use: The total amount of water consumed in evaporation and respiration by a crop during the entire growing season expressed in depth or volume of water per hectare.

Seasonal Drought: A kind of drought which occurs during distinct annual period of dry weather.

Short Wave Radiation: Radiation with wavelengths less than 4 microns.

Shower: In weather reports, solid or liquid precipitation from a convection cloud is designated a shower and is distinguished in such reports from the precipitation, intermittent or continuous, from layer clouds. Showers are often characterized by short duration and rapid fluctuations of intensity. Hail invariably implies a shower, while drizzle very seldom does.

Soil Moisture: The moisture content of soils is generally as the percentage ratio of the mass of water to that of dry soil, but may be expressed also in terms of inches of water per given depth of soil.

Soil Moisture Deficit: The amount of rainfall or irrigation required to restore soil to its field capacity.

Soil Moisture Stress: It is the sum of soil moisture tension and the osmotic pressure of the soil solution.

Soil Moisture Tension: It is the force with which the water is held by soil against gravity. It is generally expressed in mm of mercury.

Specific Heat: The specific heat of a substance is the heat required to raise the temperature of unit mass of it by one degree; it has normally been expressed in the unit 'calories/gram degree kelvin'.

Specific Humidity: The ratio of the mass of water vapour in a volume of moist air to the total mass of the volume of moist air.

Squall: A strong wind that rises suddenly, generally lasts for some minutes, and dies comparatively suddenly away. It is distinguished from a gust by its longer duration.

Stratus (St): One of the cloud genera, Generally grey cloud layer with a fairly uniform base, which may give drizzle ice prisms or snow grains. When the sun is visible through the cloud, its outline is clearly discernible. Stratus does not produce halo phenomena except, possibly, at very low temperatures.

Streamline: A curve which is parallel to the instantaneous direction of the wind vector at all points along it. Isobars are streamlines only in strict geostrophic flow.

Sub Humid: A climate or region where the moisture content is below the under humid conditions but normally still adequate for the production of many crops without irrigation.

Sun Zine Hours: The number of hours of bright sun shine per day , also some times defined as the duration of traces of burns made on a chart by Campbell-Stokes recorder .

Sunshine Recorder: An instrument for recording the duration of bright sunshine. Such instruments depend either on the heating action of the sun or on the chemical action produced by the sun's rays.

Synoptic Chart: A chart or map on which is represented the distribution of selected meteorological elements over a large area at a specified instant of time. 'Surface synoptic chart' is an alternative for weather map.

Synoptic Meteorology: That branch of meteorology which is concerned with a description of current weather as represented on geographical charts and applied especially to the prediction of its future development.

Synoptic Station: A station at which meteorological observations are made at the 'major synoptic hours' 00, 06, 12, 18 GMT and normally also at the 'minor synoptic hours' 03, 09, 15, 21 GMT, the observed elements being plotted symbolically on the weather map.

Temperature Inversion: An increase of air temperature with height so that warmer air overlies colder air.

Temperate Zone: Either of two latitudinal zones on the earth's surface which lies between 23 027" and 66 0 27 " north and south.

Tensiometer: A device of measuring the negative pressure (or tension ) of water in soil consisting a porous permeable ceramic cup connecting through a tube to a manometer or vacuum gauge .
terrestrial radiation: The long wave radiation emitted by the earth and atmosphere in the approximate temperature range 200-300 K. The radiation is confined within the wavelengths of about 3 and 100 mm and has maximum intensity at about 10mm.

Thermal Capacity: The thermal capacity, also called heat capacity, of a body is the product of its mass and its specific heat.

Thermograph: Apparatus used to give a continuous record as a geographical chart of temperature with time.

Thermo-hygrograph: Instrument resulting from the combination of hygrograph and thermograph. It furnishes on the same chart simultaneously a continuous recording of atmospheric temperature and humidity.

Thermo Isopleths: Lines of equal soil temperatures.

Thermoperiodicity: Effect of temperature difference between light and dark periods upon plant.

Thickness: The geopotential height difference at a given place between specified pressure levels. Thickness values relating to selected standard pressure levels are obtained from radiosonde observations and are plotted on geographical thickness charts. Contours are drawn at an appropriate thickness interval, joining places of equal thickness and are termed 'thickness lines'. Analysis of such charts is termed as 'thickness analysis' and has an important role in synoptic meteorology.

Thunder Storm: One or more sudden electrical discharges, manifested by a flash of light (lighting) and a sharp or rumbling sound( thunder).

Topo Climatology: Study of local climate as affected by slope and other surface characteristics.

Trade Winds: The trade winds (or 'tropical easterlies') are the winds which diverge from the subtropical high-pressure belts, centered at 300-400 N and S, towards the equator, from north-east in the northern hemisphere and south-east in the southern hemisphere.

Trough: A trough (of low pressure) is a pressure feature of the synoptic chart; it is characterized by a system of isobars which are concave towards a depression and have maximum curvature along the axis of the trough, or trough line. The trough is said to be deep or shallow, according as the maximum curvature of the isobars along the trough line is more or small, respectively, the former corresponds to the V shape referred to in the obsolete term 'v-shaped' depression.

Transpiration: The process of water vapour release to the atmosphere from the aerial organs of the plant.

Transpiration Ratio: The quantity of water transpired to produce a unit amount of dry matter.

Umkehr Effect: An effect which is used to infer the vertical distribution of Ozone from surface measurement .

Upland: Cultivable land situated on high ground or the land which has perfect natural drainage .

Upslope Fog: Fog which is formed on the windward slopes of high ground by the forced uplift of stable , moist air till saturation is reached by adiabatic expansion.

Verification of Forecasts: The process of obtaining a measure of the success of forecasts by relating predicted weather to actual weather. While simple comparison may serve to reveal certain features, for example a systematic bias towards optimism or pessimism, the verification process generally consists of deriving an index by one or other of a variety of methods which depend on the nature of the forecast.

Visibility: Visibility is defined as the greatest distance at which an object of specified characteristics can be seen and identified with the unaided eye in any particular circumstances, or, in the case of night observations, could be seen and identified if the general illumination were raised to the normal daylight level.

Warm Front: A front whose movement is such that the warmer air mass is replacing colder air mass.

Water Balance: It's hydrological balance between rainfall plus irrigation to that of changes in soil moisture, evaporation, percolation and runoff.

Water Harvesting: Conservation of rain water under non irrigated condition, by collecting runoff of precipitation in order to supplement soil moisture in an adjacent area.

Water Holding Capacity: The weight of the water held by a given quantity of absolutely dry soil when saturated.

Water Shed: It's the area above a given point on a stream that contributes water to the flow at that point. Catchment basin or drainage basin are synonymous with it.

Weather: The state of the atmosphere with respect to wind, temperature, cloudiness relative humidity, pressure etc. at a given time

Wet Bulb Depression: Difference between simultaneous reading of wet and dry bulb thermometers .

Wet Season: A period during which the precipitation in excess of water requirement and water accumulated in the soil and in reservoirs.

Wind: The horizontal movement of the air related to the surface of the earth. In meteorology, the specified wind direction is that, relative to true geographic North, from which the winds blow.

Wind direction :

Wind Blast: Injury to leaves and twigs by strong winds.

Wind Vane: Device used to indicate the directions from which the wind is blowing.

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