FIELD TRIP TO NIMET ENUGU- AGIDI

                   

HISTORY:

In Nigeria, metrological services started in 1892when the first weather observatory was established by the British colonial government at the Race course, Lagos. Thereafter the Metrological Department operated under various ministries at different times until June 2003 when the Nigerian Metrological agency bill was passed and signed into law thereby creating NIMET as a parastatal under the Federal Ministry of Aviation.

   One of the functions of NIMET is to promote the services of metrological agency in agricultural, drought and desertification activities.

INTRODUCTION:

Metrology is the scientific study of atmospheric phenomena as related to weather. Metrology is based on physics and mathematics.

The word 'metrology' was coined from a book, 'Metrologica' which was written by Aristotle, the Greek scientist and philosopher around 340 BC.

Climatology is basically an empirical science that is firmly rooted in weather observation and measurement. Climatology is the scientific study of climate which is the synthesis of weather over a long period conventionally taken as 30 years. Climate therefore represents the characteristic conditions of the atmosphere over an area or location deduced from repeated weather observation and measurement over a period of time.

                                        

                                       

                                   WEATHER INSTRUMENT

First of all, we talk about the metrological enclosure. It should be a level ground. No tall instrument around the enclosure to avoid them casting shadows on the instruments.

Dimension: standard measurement =20m ×20m

FIG A: LAYOUT OF A WEATHER STATION

Weather observation and measurement can take place from various platforms on the earth's surface, in the atmosphere and in space.

various weather instruments are used to measure weather elements. Some are active sensors that are directly immersed within the atmosphere. Others are remote sensors which measure weather elements from a distance without direct physical contact with the parameters being measured. Weather instruments may also be categorised into two types depending on whether they are self recording (autographic) or non-self recording ( manual). The former instruments provide continuous measurement of weather elements over a defined period of time. The latter instruments have to be read by observers at chosen times of the day.

* AUTOMATIC WEATHER SYSTEM

Has the ability of giving all the records that is taken manually. It has a sensor that will send the reading to the office. from the computers, you can get all the readings automatically.

FIG. B:AWS ( Automatic Weather System)

The measurings that can be gotten from this include;

§  Temperature

§  Dry bulb reading

§  Wet bulb reading

§  Rainfall value

§  thunderstorm

§  Radiation

§  Wind speed and direction

* WIND VANE

Wind vane has a tail and a head, the head is a pointer that shows the direction the wind is blowing from. Win direction is observed with the aid of a windvane. The device consists of a horizontal arm pivoted on a steel spindle with a pointer at one end. 

* CUP-COUNTER ANEMOMETER

Wind speed is measured with the aid of cup anemometer which consists of three or four cups conical or hemispherical in shape, mounted symmetrically about a vertical axis. The cups rotate according to the prevailing wind speed. Measures wind speed in KM.

FIG. C: CUP-COUNTER ANEMOMETER

* RAINGUAGE

Rainfall is measured by the use of a rain gauge. The rain gauge collects rainfall over a funnel of a known area (limited by its rim). The amount of rain water collected is poured into a graduated measuring jar where it is indicated in units of depth such as millimetres. The rain gauge provides the total volume of rain that falls between two observation times. The rain gauge is conventionally read at 0900 hours and the amount of rain measured is credited to the preceeding 24 hour period.

  Several factors determine the amount of rain that a given rain gauge is able to catch. These include the siting and exposure of the rain gauge and wind speed. Wind produces turbulent eddies around and over the rain gauge. Rain gauge must therefore be carefully sited to avoid interference of nearby objects with the amount of rain caught. No tree,  building or any other object should be near the rain gauge to minimize the effect of a possible interference.                                                              

                       

FIG. D: MANUAL RAIN GAUGE

We were told about the tilting siphon autographic rain gauge that contains a collecting chamber fitted with a float. As the rain falls and the chamber fills up, the float rises and a pen attached to the traces a graph on a chart fixed to a cylindrical drum driven by clock work. When the chamber is filled up, it tilts over on its pivot and the content siphon out of the gauge. The float returns to its original level and the now rests at the base of the chart. One complete cycle measures 5mm of rainfall. On the autographic rain chart, the horizontal lines represent the amount of rainfall in millimetres while the vertical lines represent rainfall duration in hours and minutes.

FIG. E: AUTOMATIC  RAIN GUAGE

* SOIL THERMOMETER

Soil thermometers are used for measuring soil temperatures at various depths. These are usually mercurial thermometers with the bulbs embedded in paraffin wax. The thermometers are suspended in steel tubes and inserted into the soil at various depths. The depths at which soil temperatures are measured are 5cm, 10cm, 20cm, 50cm and 100cm. For shallower depths, mercurial thermometers with their stems bent at right angles for reading convenience are used. The 5cm thermometer measures temperature of the soil at 5cm depth, it is closer to the surface therefore it is the most sensitive because it captures almost what happens at the surface (temperature of the top soil)

FIG. F:SOIL THERMOMETER

*  CAMPBELL-STOKES SUNSHINE RECORDER

The duration of sunshine is measured with the aid of Campbell-Stokes sunshine recorder. It consists of a glass sphere which focuses the rays of the sun on a sensitised card graduated in hours and minutes and held in a metal half-bowl with which the sphere is concentric. The instrument is mounted in the open on a concrete pillar about 1.5m above the ground. Bright sunshine traces a burnt line along the sensitised card while cloudy periods are blank. The total duration of sunshine for the day is obtained by measuring the total length of the burnt traces on the card which is rendered in hours and minutes.

FIG. G:CAMPBELL STOKES RECORDER

*  EVAPORIMETER

Evaporation is measured by the use of what are generally called evaporimeters.

Evaporation is the conversion of moisture into vapour form and its removal and transport upwards into the atmosphere. The process of water loss from a vegetated surface is referred to as evapotranspiration.

Piche evaporimeter is used to measure the rate of evaporation (in mililitres). it is a graduated measuring cylindrical tube enclosed at one end and containing water. A disk of filter paper is attached to the open end and the paper is kept continuously moist by a wick linking it to a small water container. The instrument is kept within the Stevenson's screen. The Piche evaporimeter is not very reliable and it has been criticised as measuring the drying power of the air rather than the amount of water lost by evaporation to the atmosphere. Hence, evaporation pans are more commonly used at weather stations. There are different types of evaporation pans depending on their size, shape and manner of exposure.

Class A pan which has been recommended for world-wide use by the WMO (World Metrological Organization), is a cylindrical pan with a diameter of 1206mm and 2.54mm deep. It is used to measure amount of evaporation. It is filled with water to within 51mm of the rim and mounted on a wooden platform so that the water surface within the pan is 305mm above the ground. It is painted aluminium white. The pan is filled with water to the appropriate level and left in the open away from any obstacles, in the weather station. After a period of time which is usually 24 hours, the level of water in the pan is checked. Unless some rain has fallen during the intervening period, the level of water in the pan would have fallen owing to evaporation. The pan is reset by filling it back with water to the original level. The amount of water added to reset the pan represents the evaporation that has occurred in the intervening period.

       FIG. H: CLASS A PAN

 *  MINIMUM AND MAXIMUM THERMOMETERS

 Air temperature is measured manually with the aid of maximum and minimum thermometers. They are housed in a Stevenson's screen, this is a wooden louvred cupboard with a hinged door mounted on a steel. It is painted white. The louvred sides allow adequate ventilation while the white paint prevents absorption of solar radiation by the shelter. The thermometers placed within the Stevenson screen thus give a close approximation to the true air temperature undisturbed by the effects of direct solar or terrestrial radiaton.

        

           FIG. I: STEVENSON SCREEN

 The maximum thermometer is a mercury-in- glass thermometer containing a small glass index which the mercury pushes along when air temperature rises but leaves behind when the temperature falls.

The minimum thermometer is an alcohol-in-glass thermometer in which when the temperature rises the alcohol expands and flows past the index and when the temperature falls the alcohol contracts and drags the index back because of its surface tension. The end of the index nearer the meniscus shows the minimum temperature and the instrument is reset by tilting. The maximum and minimum thermometers are used at weather stations to measure the highest and lowest temperatures within the day respectively.

FIG. J: MINIMUM AND MAXIMUM THERMOMETERS

*  WET AND DRY BULB THERMOMETER

 The relative humidity of the air is measured manually at a weather station with the aid of wet and dry  bulb thermometers. It is housed in the Stevenson screen. The dry bulb thermometer has its bulb covered with muslin perpetually wetted with pure water. This gives the wet bulb reading which in unsaturated air is less than the dry bulb temperature. This is because the latent heat required to evaporate water from the muslin is supplied by air in contact with the wet bulb.   

When relative humidity= 100% , amount of water going up is equal to that coming down.

FIG. K: WET AND DRY THERMOMETER

*  GRASS MINIMUM THERMOMETER

A type of minimum thermometer used to measure the lowest temperature above uniform short grasses. It is used to measure ground temperature.

* CLOUD

If the whole sky is covered by cloud, it is called overcast i.e we have 8 octas covering the sky.

Classification:

High clouds- Cirrus, cirro-stratos, cirro-cumulus

Medium clouds- Alto-cumulus, Nimbostratus, Alto-stratos

Low clouds- Cumulus, stratos, strato-cumulus, Cummulo nimbos

Alto-cumulus is in form of ridges.

Cumulus is in form of cotton wool, white in colour.

When alto-stratos is seen it means that rainfall is at hand.

Stratos moves fast.

*  VISIBILITY

Visibility means seeing and recognizing.

Ø Less than 6km means poor visibility

Ø 10km and above means very good visibility

Ø 6km-9km means fair visibility.

RELEVANCE OF THE VISIT TO NIMET TO CROP SCIENCE

Weather and climate have always been part of the physical environment in which the human society thrives. The weather and climate characteristics of any place on earth determine the types of crops that are grown for food. It is  said that of all the human activities, agriculture which provides food for people and contributes significantly to the economies of nations, is the most sensitive to weather. Normal weather conditions are associated with good crop yield and positive economic impact.

soil thermometer is of immerse importance to agriculture. Because there are some crops that are shallow rooted and others that are deep-rooted. It helps to know at what depth to plant the particular crop so as to have its maximum yield.

The thermometer gives various conditions at various depths which help to determine the temperature at which different crops can thrive.

Some crops need some kind of heat to thrive while some need cold conditions.

                      FIELD TRIP TO NIMET ENUGU- AGIDI

HISTORY:

In Nigeria, metrological services started in 1892when the first weather observatory was established by the British colonial government at the Race course, Lagos. Thereafter the Metrological Department operated under various ministries at different times until June 2003 when the Nigerian Metrological agency bill was passed and signed into law thereby creating NIMET as a parastatal under the Federal Ministry of Aviation.

   One of the functions of NIMET is to promote the services of metrological agency in agricultural, drought and desertification activities.

INTRODUCTION:

Metrology is the scientific study of atmospheric phenomena as related to weather. Metrology is based on physics and mathematics.

The word 'metrology' was coined from a book, 'Metrologica' which was written by Aristotle, the Greek scientist and philosopher around 340 BC.

Climatology is basically an empirical science that is firmly rooted in weather observation and measurement. Climatology is the scientific study of climate which is the synthesis of weather over a long period conventionally taken as 30 years. Climate therefore represents the characteristic conditions of the atmosphere over an area or location deduced from repeated weather observation and measurement over a period of time.

                                        

                                       

                                   WEATHER INSTRUMENT

First of all, we talk about the metrological enclosure. It should be a level ground. No tall instrument around the enclosure to avoid them casting shadows on the instruments.

Dimension: standard measurement =20m ×20m

FIG A: LAYOUT OF A WEATHER STATION

Weather observation and measurement can take place from various platforms on the earth's surface, in the atmosphere and in space.

various weather instruments are used to measure weather elements. Some are active sensors that are directly immersed within the atmosphere. Others are remote sensors which measure weather elements from a distance without direct physical contact with the parameters being measured. Weather instruments may also be categorised into two types depending on whether they are self recording (autographic) or non-self recording ( manual). The former instruments provide continuous measurement of weather elements over a defined period of time. The latter instruments have to be read by observers at chosen times of the day.

* AUTOMATIC WEATHER SYSTEM

Has the ability of giving all the records that is taken manually. It has a sensor that will send the reading to the office. from the computers, you can get all the readings automatically.

FIG. B:AWS ( Automatic Weather System)

The measurings that can be gotten from this include;

§  Temperature

§  Dry bulb reading

§  Wet bulb reading

§  Rainfall value

§  thunderstorm

§  Radiation

§  Wind speed and direction

* WIND VANE

Wind vane has a tail and a head, the head is a pointer that shows the direction the wind is blowing from. Win direction is observed with the aid of a windvane. The device consists of a horizontal arm pivoted on a steel spindle with a pointer at one end. 

* CUP-COUNTER ANEMOMETER

Wind speed is measured with the aid of cup anemometer which consists of three or four cups conical or hemispherical in shape, mounted symmetrically about a vertical axis. The cups rotate according to the prevailing wind speed. Measures wind speed in KM.

FIG. C: CUP-COUNTER ANEMOMETER

* RAINGUAGE

Rainfall is measured by the use of a rain gauge. The rain gauge collects rainfall over a funnel of a known area (limited by its rim). The amount of rain water collected is poured into a graduated measuring jar where it is indicated in units of depth such as millimetres. The rain gauge provides the total volume of rain that falls between two observation times. The rain gauge is conventionally read at 0900 hours and the amount of rain measured is credited to the preceeding 24 hour period.

  Several factors determine the amount of rain that a given rain gauge is able to catch. These include the siting and exposure of the rain gauge and wind speed. Wind produces turbulent eddies around and over the rain gauge. Rain gauge must therefore be carefully sited to avoid interference of nearby objects with the amount of rain caught. No tree,  building or any other object should be near the rain gauge to minimize the effect of a possible interference.                                                              

                       

FIG. D: MANUAL RAIN GAUGE

We were told about the tilting siphon autographic rain gauge that contains a collecting chamber fitted with a float. As the rain falls and the chamber fills up, the float rises and a pen attached to the traces a graph on a chart fixed to a cylindrical drum driven by clock work. When the chamber is filled up, it tilts over on its pivot and the content siphon out of the gauge. The float returns to its original level and the now rests at the base of the chart. One complete cycle measures 5mm of rainfall. On the autographic rain chart, the horizontal lines represent the amount of rainfall in millimetres while the vertical lines represent rainfall duration in hours and minutes.

FIG. E: AUTOMATIC  RAIN GUAGE

* SOIL THERMOMETER

Soil thermometers are used for measuring soil temperatures at various depths. These are usually mercurial thermometers with the bulbs embedded in paraffin wax. The thermometers are suspended in steel tubes and inserted into the soil at various depths. The depths at which soil temperatures are measured are 5cm, 10cm, 20cm, 50cm and 100cm. For shallower depths, mercurial thermometers with their stems bent at right angles for reading convenience are used. The 5cm thermometer measures temperature of the soil at 5cm depth, it is closer to the surface therefore it is the most sensitive because it captures almost what happens at the surface (temperature of the top soil)

FIG. F:SOIL THERMOMETER

*  CAMPBELL-STOKES SUNSHINE RECORDER

The duration of sunshine is measured with the aid of Campbell-Stokes sunshine recorder. It consists of a glass sphere which focuses the rays of the sun on a sensitised card graduated in hours and minutes and held in a metal half-bowl with which the sphere is concentric. The instrument is mounted in the open on a concrete pillar about 1.5m above the ground. Bright sunshine traces a burnt line along the sensitised card while cloudy periods are blank. The total duration of sunshine for the day is obtained by measuring the total length of the burnt traces on the card which is rendered in hours and minutes.

FIG. G:CAMPBELL STOKES RECORDER

*  EVAPORIMETER

Evaporation is measured by the use of what are generally called evaporimeters.

Evaporation is the conversion of moisture into vapour form and its removal and transport upwards into the atmosphere. The process of water loss from a vegetated surface is referred to as evapotranspiration.

Piche evaporimeter is used to measure the rate of evaporation (in mililitres). it is a graduated measuring cylindrical tube enclosed at one end and containing water. A disk of filter paper is attached to the open end and the paper is kept continuously moist by a wick linking it to a small water container. The instrument is kept within the Stevenson's screen. The Piche evaporimeter is not very reliable and it has been criticised as measuring the drying power of the air rather than the amount of water lost by evaporation to the atmosphere. Hence, evaporation pans are more commonly used at weather stations. There are different types of evaporation pans depending on their size, shape and manner of exposure.

Class A pan which has been recommended for world-wide use by the WMO (World Metrological Organization), is a cylindrical pan with a diameter of 1206mm and 2.54mm deep. It is used to measure amount of evaporation. It is filled with water to within 51mm of the rim and mounted on a wooden platform so that the water surface within the pan is 305mm above the ground. It is painted aluminium white. The pan is filled with water to the appropriate level and left in the open away from any obstacles, in the weather station. After a period of time which is usually 24 hours, the level of water in the pan is checked. Unless some rain has fallen during the intervening period, the level of water in the pan would have fallen owing to evaporation. The pan is reset by filling it back with water to the original level. The amount of water added to reset the pan represents the evaporation that has occurred in the intervening period.

       FIG. H: CLASS A PAN

 *  MINIMUM AND MAXIMUM THERMOMETERS

 Air temperature is measured manually with the aid of maximum and minimum thermometers. They are housed in a Stevenson's screen, this is a wooden louvred cupboard with a hinged door mounted on a steel. It is painted white. The louvred sides allow adequate ventilation while the white paint prevents absorption of solar radiation by the shelter. The thermometers placed within the Stevenson screen thus give a close approximation to the true air temperature undisturbed by the effects of direct solar or terrestrial radiaton.

        

           FIG. I: STEVENSON SCREEN

 The maximum thermometer is a mercury-in- glass thermometer containing a small glass index which the mercury pushes along when air temperature rises but leaves behind when the temperature falls.

The minimum thermometer is an alcohol-in-glass thermometer in which when the temperature rises the alcohol expands and flows past the index and when the temperature falls the alcohol contracts and drags the index back because of its surface tension. The end of the index nearer the meniscus shows the minimum temperature and the instrument is reset by tilting. The maximum and minimum thermometers are used at weather stations to measure the highest and lowest temperatures within the day respectively.

FIG. J: MINIMUM AND MAXIMUM THERMOMETERS

*  WET AND DRY BULB THERMOMETER

 The relative humidity of the air is measured manually at a weather station with the aid of wet and dry  bulb thermometers. It is housed in the Stevenson screen. The dry bulb thermometer has its bulb covered with muslin perpetually wetted with pure water. This gives the wet bulb reading which in unsaturated air is less than the dry bulb temperature. This is because the latent heat required to evaporate water from the muslin is supplied by air in contact with the wet bulb.   

When relative humidity= 100% , amount of water going up is equal to that coming down.

FIG. K: WET AND DRY THERMOMETER

*  GRASS MINIMUM THERMOMETER

A type of minimum thermometer used to measure the lowest temperature above uniform short grasses. It is used to measure ground temperature.

* CLOUD

If the whole sky is covered by cloud, it is called overcast i.e we have 8 octas covering the sky.

Classification:

High clouds- Cirrus, cirro-stratos, cirro-cumulus

Medium clouds- Alto-cumulus, Nimbostratus, Alto-stratos

Low clouds- Cumulus, stratos, strato-cumulus, Cummulo nimbos

Alto-cumulus is in form of ridges.

Cumulus is in form of cotton wool, white in colour.

When alto-stratos is seen it means that rainfall is at hand.

Stratos moves fast.

*  VISIBILITY

Visibility means seeing and recognizing.

Ø Less than 6km means poor visibility

Ø 10km and above means very good visibility

Ø 6km-9km means fair visibility.

RELEVANCE OF THE VISIT TO NIMET TO CROP SCIENCE

Weather and climate have always been part of the physical environment in which the human society thrives. The weather and climate characteristics of any place on earth determine the types of crops that are grown for food. It is  said that of all the human activities, agriculture which provides food for people and contributes significantly to the economies of nations, is the most sensitive to weather. Normal weather conditions are associated with good crop yield and positive economic impact.

soil thermometer is of immerse importance to agriculture. Because there are some crops that are shallow rooted and others that are deep-rooted. It helps to know at what depth to plant the particular crop so as to have its maximum yield.

The thermometer gives various conditions at various depths which help to determine the temperature at which different crops can thrive.

Some crops need some kind of heat to thrive while some need cold conditions.

                      FIELD TRIP TO NIMET ENUGU- AGIDI

HISTORY:

In Nigeria, metrological services started in 1892when the first weather observatory was established by the British colonial government at the Race course, Lagos. Thereafter the Metrological Department operated under various ministries at different times until June 2003 when the Nigerian Metrological agency bill was passed and signed into law thereby creating NIMET as a parastatal under the Federal Ministry of Aviation.

   One of the functions of NIMET is to promote the services of metrological agency in agricultural, drought and desertification activities.

INTRODUCTION:

Metrology is the scientific study of atmospheric phenomena as related to weather. Metrology is based on physics and mathematics.

The word 'metrology' was coined from a book, 'Metrologica' which was written by Aristotle, the Greek scientist and philosopher around 340 BC.

Climatology is basically an empirical science that is firmly rooted in weather observation and measurement. Climatology is the scientific study of climate which is the synthesis of weather over a long period conventionally taken as 30 years. Climate therefore represents the characteristic conditions of the atmosphere over an area or location deduced from repeated weather observation and measurement over a period of time.

                                        

                                       

                                   WEATHER INSTRUMENT

First of all, we talk about the metrological enclosure. It should be a level ground. No tall instrument around the enclosure to avoid them casting shadows on the instruments.

Dimension: standard measurement =20m ×20m

FIG A: LAYOUT OF A WEATHER STATION

Weather observation and measurement can take place from various platforms on the earth's surface, in the atmosphere and in space.

various weather instruments are used to measure weather elements. Some are active sensors that are directly immersed within the atmosphere. Others are remote sensors which measure weather elements from a distance without direct physical contact with the parameters being measured. Weather instruments may also be categorised into two types depending on whether they are self recording (autographic) or non-self recording ( manual). The former instruments provide continuous measurement of weather elements over a defined period of time. The latter instruments have to be read by observers at chosen times of the day.

* AUTOMATIC WEATHER SYSTEM

Has the ability of giving all the records that is taken manually. It has a sensor that will send the reading to the office. from the computers, you can get all the readings automatically.

FIG. B:AWS ( Automatic Weather System)

The measurings that can be gotten from this include;

§  Temperature

§  Dry bulb reading

§  Wet bulb reading

§  Rainfall value

§  thunderstorm

§  Radiation

§  Wind speed and direction

* WIND VANE

Wind vane has a tail and a head, the head is a pointer that shows the direction the wind is blowing from. Win direction is observed with the aid of a windvane. The device consists of a horizontal arm pivoted on a steel spindle with a pointer at one end. 

* CUP-COUNTER ANEMOMETER

Wind speed is measured with the aid of cup anemometer which consists of three or four cups conical or hemispherical in shape, mounted symmetrically about a vertical axis. The cups rotate according to the prevailing wind speed. Measures wind speed in KM.

FIG. C: CUP-COUNTER ANEMOMETER

* RAINGUAGE

Rainfall is measured by the use of a rain gauge. The rain gauge collects rainfall over a funnel of a known area (limited by its rim). The amount of rain water collected is poured into a graduated measuring jar where it is indicated in units of depth such as millimetres. The rain gauge provides the total volume of rain that falls between two observation times. The rain gauge is conventionally read at 0900 hours and the amount of rain measured is credited to the preceeding 24 hour period.

  Several factors determine the amount of rain that a given rain gauge is able to catch. These include the siting and exposure of the rain gauge and wind speed. Wind produces turbulent eddies around and over the rain gauge. Rain gauge must therefore be carefully sited to avoid interference of nearby objects with the amount of rain caught. No tree,  building or any other object should be near the rain gauge to minimize the effect of a possible interference.                                                              

                       

FIG. D: MANUAL RAIN GAUGE

We were told about the tilting siphon autographic rain gauge that contains a collecting chamber fitted with a float. As the rain falls and the chamber fills up, the float rises and a pen attached to the traces a graph on a chart fixed to a cylindrical drum driven by clock work. When the chamber is filled up, it tilts over on its pivot and the content siphon out of the gauge. The float returns to its original level and the now rests at the base of the chart. One complete cycle measures 5mm of rainfall. On the autographic rain chart, the horizontal lines represent the amount of rainfall in millimetres while the vertical lines represent rainfall duration in hours and minutes.

FIG. E: AUTOMATIC  RAIN GUAGE

* SOIL THERMOMETER

Soil thermometers are used for measuring soil temperatures at various depths. These are usually mercurial thermometers with the bulbs embedded in paraffin wax. The thermometers are suspended in steel tubes and inserted into the soil at various depths. The depths at which soil temperatures are measured are 5cm, 10cm, 20cm, 50cm and 100cm. For shallower depths, mercurial thermometers with their stems bent at right angles for reading convenience are used. The 5cm thermometer measures temperature of the soil at 5cm depth, it is closer to the surface therefore it is the most sensitive because it captures almost what happens at the surface (temperature of the top soil)

FIG. F:SOIL THERMOMETER

*  CAMPBELL-STOKES SUNSHINE RECORDER

The duration of sunshine is measured with the aid of Campbell-Stokes sunshine recorder. It consists of a glass sphere which focuses the rays of the sun on a sensitised card graduated in hours and minutes and held in a metal half-bowl with which the sphere is concentric. The instrument is mounted in the open on a concrete pillar about 1.5m above the ground. Bright sunshine traces a burnt line along the sensitised card while cloudy periods are blank. The total duration of sunshine for the day is obtained by measuring the total length of the burnt traces on the card which is rendered in hours and minutes.

FIG. G:CAMPBELL STOKES RECORDER

*  EVAPORIMETER

Evaporation is measured by the use of what are generally called evaporimeters.

Evaporation is the conversion of moisture into vapour form and its removal and transport upwards into the atmosphere. The process of water loss from a vegetated surface is referred to as evapotranspiration.

Piche evaporimeter is used to measure the rate of evaporation (in mililitres). it is a graduated measuring cylindrical tube enclosed at one end and containing water. A disk of filter paper is attached to the open end and the paper is kept continuously moist by a wick linking it to a small water container. The instrument is kept within the Stevenson's screen. The Piche evaporimeter is not very reliable and it has been criticised as measuring the drying power of the air rather than the amount of water lost by evaporation to the atmosphere. Hence, evaporation pans are more commonly used at weather stations. There are different types of evaporation pans depending on their size, shape and manner of exposure.

Class A pan which has been recommended for world-wide use by the WMO (World Metrological Organization), is a cylindrical pan with a diameter of 1206mm and 2.54mm deep. It is used to measure amount of evaporation. It is filled with water to within 51mm of the rim and mounted on a wooden platform so that the water surface within the pan is 305mm above the ground. It is painted aluminium white. The pan is filled with water to the appropriate level and left in the open away from any obstacles, in the weather station. After a period of time which is usually 24 hours, the level of water in the pan is checked. Unless some rain has fallen during the intervening period, the level of water in the pan would have fallen owing to evaporation. The pan is reset by filling it back with water to the original level. The amount of water added to reset the pan represents the evaporation that has occurred in the intervening period.

       FIG. H: CLASS A PAN

 *  MINIMUM AND MAXIMUM THERMOMETERS

 Air temperature is measured manually with the aid of maximum and minimum thermometers. They are housed in a Stevenson's screen, this is a wooden louvred cupboard with a hinged door mounted on a steel. It is painted white. The louvred sides allow adequate ventilation while the white paint prevents absorption of solar radiation by the shelter. The thermometers placed within the Stevenson screen thus give a close approximation to the true air temperature undisturbed by the effects of direct solar or terrestrial radiaton.

        

           FIG. I: STEVENSON SCREEN

 The maximum thermometer is a mercury-in- glass thermometer containing a small glass index which the mercury pushes along when air temperature rises but leaves behind when the temperature falls.

The minimum thermometer is an alcohol-in-glass thermometer in which when the temperature rises the alcohol expands and flows past the index and when the temperature falls the alcohol contracts and drags the index back because of its surface tension. The end of the index nearer the meniscus shows the minimum temperature and the instrument is reset by tilting. The maximum and minimum thermometers are used at weather stations to measure the highest and lowest temperatures within the day respectively.

FIG. J: MINIMUM AND MAXIMUM THERMOMETERS

*  WET AND DRY BULB THERMOMETER

 The relative humidity of the air is measured manually at a weather station with the aid of wet and dry  bulb thermometers. It is housed in the Stevenson screen. The dry bulb thermometer has its bulb covered with muslin perpetually wetted with pure water. This gives the wet bulb reading which in unsaturated air is less than the dry bulb temperature. This is because the latent heat required to evaporate water from the muslin is supplied by air in contact with the wet bulb.   

When relative humidity= 100% , amount of water going up is equal to that coming down.

FIG. K: WET AND DRY THERMOMETER

*  GRASS MINIMUM THERMOMETER

A type of minimum thermometer used to measure the lowest temperature above uniform short grasses. It is used to measure ground temperature.

* CLOUD

If the whole sky is covered by cloud, it is called overcast i.e we have 8 octas covering the sky.

Classification:

High clouds- Cirrus, cirro-stratos, cirro-cumulus

Medium clouds- Alto-cumulus, Nimbostratus, Alto-stratos

Low clouds- Cumulus, stratos, strato-cumulus, Cummulo nimbos

Alto-cumulus is in form of ridges.

Cumulus is in form of cotton wool, white in colour.

When alto-stratos is seen it means that rainfall is at hand.

Stratos moves fast.

*  VISIBILITY

Visibility means seeing and recognizing.

Ø Less than 6km means poor visibility

Ø 10km and above means very good visibility

Ø 6km-9km means fair visibility.

RELEVANCE OF THE VISIT TO NIMET TO CROP SCIENCE

Weather and climate have always been part of the physical environment in which the human society thrives. The weather and climate characteristics of any place on earth determine the types of crops that are grown for food. It is  said that of all the human activities, agriculture which provides food for people and contributes significantly to the economies of nations, is the most sensitive to weather. Normal weather conditions are associated with good crop yield and positive economic impact.

soil thermometer is of immerse importance to agriculture. Because there are some crops that are shallow rooted and others that are deep-rooted. It helps to know at what depth to plant the particular crop so as to have its maximum yield.

The thermometer gives various conditions at various depths which help to determine the temperature at which different crops can thrive.

Some crops need some kind of heat to thrive while some need cold conditions.

GENE MUTATION

                     

A gene mutation is a permanent alteration  in the DNA sequence that makes up a gene such that the sequence differs from what is found in most people . mutations range in size they can affect anywhere from a single DNA building block (base pair) to a large  segment of a chromosome that includes  multiple genes.

Mutations are changes in the genetic sequence and they are a main cause of diversity among organism. These changes occur at many different levels and they can have widely differing consequences. In biological systems that are capable of reproduction . For mutations to affect an organisms decendants they must;

·       occur in cells that produce the next generation

they affect the hereditary material.Ultimately the interplay between inherited mutations and environmental pressures generates diversity among species.

 Although various forms of molecular changes occur the word mutation typically refers to a change that affects the nucleic acids.in cellular organisms the nucleic acids aer the building blocks of DNA and in viruses theybare the buildinb blocks of either the DNAorRNA.one way to think of DNA and RNA is that they are substances that carry long term memory of the information required for an organisms reproduction.

If mutation occur in non germline cells,then  this changes

Can be categorized as somatic mutation. The word somatic comes from the greek word SOMA which means “body”,and somatic mutation only affects the present organism body.from an evolutionary perspective somatic mutation are uninteresting,unless they occur systematically and change fundamental property of an individual such as capacity for survival for example,cancer is potent somatic mutatiom that will affect an organism survival.as a direct focus evolutionary theory

 Is mostly interested in DNA chsnges in the cells that produce the next generation.

Genes are the working subunits of DNA,and each gene contains a particular set of instruction usually coding for a particular function.each gene has a special job to do the DNA in genes spells out specific instructions for making proteins in the cells.proteins are the building blocks for everything in the body.

Gene mutation being the subject of study is the changing of the structure of gene rssulting in various form.which may be transmitted to the subsequent generation,caused by alterations of single base unit in DNA or deletion ,insertion of rearrangement of larger sections of genes or chrosomes.

 It can also be said to be a permanent alteration in the DNA sequence that makes up a gene,in such a way that the sequence varies from that which is found in most people.

Mutation ranges in size i.e they can affect anywhere from a single DNA building block i.e a base pair to a large segment to a chromosome that includes multiple genes.mutation is a natural process that changes a DNA series which is more common than one can think.as a cell copies its DNA before dividing a “typo” occurs every 100,000 or so nucleotide that is about 120,000 typos each time our cell divide.

Most commonly a single base is substituted for another.sometimes a base is deleted or a base is added.fortunately a cell is able to repair most of this changes when a DNA changes that will become an egg or a sperm is unpaired in a cell, it is passed down to offspring.thanks should be accorded to mutation because we have some new variationsthat were not present in our parent.

People commonly use the term “mutant” and “mutation” to describe something undesirable or broken.but mutation is not always a negative occurance,it’s positive side is that it paves way for new variation which is not present in our parent.Most DNA falls i

n the large area of the genome that sits between the genes and usually they have no effect.whenever a variation occurs within genes,there is often a consequence,but even then mutation only rarely causes death or diseases.More often,murtation give rise to variation that are good or bad.

ADVANTAGES OF MUTATION

·        it generates a new variation that can give an individual survival advantage.

·        It brings about uniqueness in an individual eg.human hair colour ,height,shape,behaviour and susceptibility to disease.

·        Because of mutation which brings about variation,the population change over time is helped.

when a DNA changes that will become an egg or a sperm is unpaired in a cell, it is passed down to offspring.thanks should be accorded to mutation because we have some new variationsthat were not present in our parent.

People commonly use the term “mutant” and “mutation” to describe something undesirable or broken.but mutation is not always a negative occurance,it’s positive side is that it paves way for new variation which is not present in our parent.Most DNA falls i

n the large area of the genome that sits between the genes and usually they have no effect.whenever a variation occurs within genes,there is often a consequence,but even then mutation only rarely causes death or diseases.More often,murtation give rise to variation that are good or bad.

ADVANTAGES OF MUTATION

Mutation have been responsible for antibiotics and resisitance in bacteria, sickle cell resistance to malaria and immunity to HIV among others.

A rare gene mutation known as Laron Syndrome(unusual shortness of height )are protected against cancer and diabetes .

It brings about variation eg .hair colour, baldness ,freckless and beauty spots .

SOCIO- CULTURAL AND ECONOMIC PROBLEMS ASSOCIATED WITH ZOONOTIC PARASITE INFECTION

SOCIO- CULTURAL AND ECONOMIC PROBLEMS ASSOCIATED WITH             ZOONOTIC PARASITE INFECTION

A zoontic disease is a  disease that can be passed between animals and humans. Zoonotic diseases can be caused by viruses, bacteria, parasite, and fungi. These diseases are very common. Scientists estimaes that moer than six out of every ten infectious diseases in humans are spread from animals. Many people interact with animals in their daily lives. We raise animals for food and keep them in our homes as pets. We might come into close contact at a country fair or petting zoo or encounter wildlife when we clear wooded land for new constructions.

The socio- cultural and economic problems associated with zoonotic parasite infections are related under the following sub topics;

Man’s lust for domestic pet and type of occupation

The risk of exposure to zoonotic agents is inherent in the practice of veterinary medicine, while comprising only a small percentage of those with reported  occupational injuries or disease. Veterinary practitioners should remain diligent to protect their own health and that of their staffs. A number of parasites are recognised causes of zoonotic diseases.

 Toxoplasma gondii is a coccidian parasite that is typically associated with cats and with potentially severe congential disease on humans. The vast majority of T. Gondii in cats are subclinical. Clinical diseases is more common in stressed, concurrently ill, or immunocompromised cats and can be manifested as fever, dyspnea, coughing, lymphadenopathy, myalgia, vomiting, diarrhea, icterus, splenomegaly, neurologic abnormalities, retinochoroiditis, or granulomatous panuveitis. (August, et al 1987). Shedding of T. Gongii oocyts appears to be rare in cats. Studies have reported that < 1% of domstic cats shed T.gondii at any point in time. (Hill, et al  2000). It has beeen reported that cat ownerships appears to be a higher risk for veterinarian to seroconvert than is working with cats in practices. (Fox FG, et al  1974).

The main concern regarding T. Gondii is its potential for zoonotic transmission to pregnant women and the development of congential disease. Congential toxoplasma can occur when naive (seronegative) women acquires a primary infection during the 1st and 2nd trimesters of pregnancy, which can result in spontanous abortion, premature birth, encephalitis, or other neutrological abnormalities. To decrease the likelihood of congential toxoplasmosis, the Amercian college of Obstetricians and Gynecologists recommends preconceptional serolodic testing. (Cunningham, et al  1997). Risk of female veterinary personnel is through oral contact with cat feces. Pregnant women should not handle cat feces and litters.

Deeply rooted cultural practises and traditions

Cultural drivers and health- seeking behaviours that impact on the transmission of pig-association zoonoses in lao people’s Democratic Republic

The lao people’s Democratic Republic (PDR) lies in southeast Asia’s Mekong Region, sharing its borders with China, Thailand, Vietnam, Cambodia and Myanmar. Agriculture is vitally important to leeser- developed economies in the region; the majority of Loa PDR’s setimately 6.9 million people live in rural areas, with agricultural sector employing 82% of labour force in 2003. Like many countriesin the region, livestock production, particularly pig rearng, is an important  ancillary income source in Lao PDR, with smallhorders farmers utilizisng traditional free-range pig production system. Pig production , however, poses a health risk to those relying on this commodities for income , with a number of pig-associated zoonotic disease can impart the exportability of livestock and associated products. Dispite this, little relevant information is available on the sociocultual divers of pig-associated zoonoses in Lao PDR, or indeed, in the wider Southeast Asia region.

The sociocultural knowledge on eight pig-associated zoonoses endemic to Southeast Asia, grouped according to their clinical manifestation im humans to highlight the propensity for underreporting: brucellosis, Q fever (Coxiella burnetii), trichinellosis, hepatitis E virus, leptospirosis, Japanese encephalitis, Streptococcus suis and Taenia solium taeniasis-cysticercosis.

Migration

Once zoonotic disease has emerged, its spread in the human population  is likely to be facilitated by population  movements.Migration, also called long-term population resettlement, is likely to spread disease that have a long period of latency or duration of  infectiousness, whereas short term morbidity for period of days or weeks, typical of “travel” pattern, may rapidly spread diseases with short resolution periods. Population displacements as a result of conflict or natural disaster are likely to create conditions of crowding and poor sanitation that are highly conducive to the spread of infectious diaeases. Human movement has siginficant implications for human and animal health. Not only are travelers ( tourists, bussinespeople, and other workers) at risk of contracting  communicable disease when visiting tropical countries, but they also can act as vectors for delivering infectious diseases to a different region or potentially round the world as in the case of SARS.

Immigrants may come from nations where infectious diseases such as tuberculosis and malaria are endemic and refugees may come from situations where crowding and malnutrition creates ideal conditions for the spread of diseases such as cholera, shigellosis, malaria and measles.(CDC, 1998).