Rainfall is measured by a precise instrument called Rain gauze. It determines the depth of precipitation that occurs over a unit area. Thus, it measures rainfall. One liter of rainfall per meter squared is equivalent to one millimeter of measured precipitation. A funneled aperture of 150-170 cm is found in standard rain gauges. They are designed as a simple passive collector. A graduated measuring glass is used for determining the amount of precipitation.

The glass tube of thermometer is filled with mercury. It is a reflective liquid. It is bright and opaque, so it’s easy to see movement of mercury inside the capillary tube and to read accurately. Mercury does not even wet the glass. So, if temperature is falling then you do not get inaccurate readings. It is also good conductor of heat. So, it responds quickly to change in temperature.

Temperature is measured based on the freezing and boiling points of water. In 1948 the Centigrade scale renamed it the "Celsius" temperature scale and most countries use the Celsius scale. Indian, and several other countries, use the Fahrenheit system of temperature measurement mainly because from the British time only Fahrenheit thermometers were available in India. It is only after the invasion of Chinese thermometers that we have flat ones that show both centigrade/ Fahrenheit scale.

Degree of the heat of our body is known as temperature. The instrument which is used to measure the temperature is known as a thermometer. Thermometers are of two types:

• Clinical thermometer and Laboratory thermometer. They have different markings, but they work in the same way.  In the thermometer, a glass tube is filled with mercury. Mercury is used to measure temperature because it changes from a solid to liquid very easily.

To measure the minimum and maximum temperature in a day, Six’s thermometer is used.  It consists of a U-shaped capillary tube having bulbs at both ends. Mercury is filled in the bend of the U-tube. One of the bulbs is completely filled with alcohol and the other bulb is partly filled with alcohol. Alcohol is the thermometric liquid in case of Six’s thermometer. Change in temperature is recorded due to expansion and contraction of alcohol.

The instrument which is used to measure the temperature is known as thermometer. Thermometers are of two types:

• Clinical thermometer and laboratory thermometer. Clinical thermometer is used for measuring the temperature of body and laboratory thermometer is used for measuring the temperature of atmosphere. They have different markings, but they work in same way.  In the thermometer, glass tube is filled with mercury. Mercury is used to measure temperature because it changes from a solid to liquid very easily.

Rain gauge can accurately measure the rainfall without any loss due to evaporation. It is an instrument used for determining the depth of precipitation that occurs over a unit area. Thus, it measures rainfall. One litre of rainfall per meter squared is equivalent to one millimeter of measured precipitation. A funneled aperture of 150-170 cm is found in standard rain gauges. They are designed as a simple passive collector. A graduated measuring glass is used for determining the amount of precipitation.

A climograph represents the average temperature and precipitation of each month. From this representation, the maximum and minimum temperatures as well as rainfall may be observed. 

The United Nations Convention in 1982 defined territorial water or territorial sea on the Law of the Sea as a belt of coastal water extending at most 12 nautical miles or 22.2 kms from the baseline of a coastal state.

West European type Regions include Western Europe from Northern Norway to the British Isles, North-West United States, and Southern Chile in South America and Tasmania Island of New Zealand in Australia. Westerly winds influence this region throughout the year. They experience high annual rainfall throughout the year. But maximum rainfall is experienced in winter. Winters are warmer. The summer temperature hardly exceeds 16 $^oC$.

• Based on the given data, January has maximum temperature of $26^0$.
  
• Hence, it is the hottest month.
  
• July has the minimum temperature of $11^0$. So, it is the coldest month.

Stevenson's Screen is used to shield meteorological instruments from precipitation and direct external radiations, such as heat. The screen is louvered to allow air to circulate around the instruments. Additionally, the screen is painted white to reflect the sun’s direct rays. This facilitates meteorological instruments such as thermometers and thermographs to measure temperatures in a standardized environment.

The Stevenson's Screen forms part of all-weather stations and was designed by Thomas Stevenson.

To measure the minimum and maximum temperature in a day, Six’s thermometer is used.  It consists of a U-shaped capillary tube having bulbs at both ends. Mercury is filled in the bend of the U-tube. One of the bulbs is completely filled with alcohol and the other bulb is partly filled with alcohol. Alcohol is the thermometric liquid in case of Six’s thermometer. Change in temperature is recorded due to expansion and contraction of alcohol.

Diurnal range of temperature is the difference between the maximum and minimum temperatures of the same days. Cloud cover, urban heat, land-use change, aerosols, water vapor, and greenhouse gases are caused due to changes in the diurnal range of temperature. As the distance from the sea increases diurnal range of temperature also increases. In dry tropical climates and on high mountain plateaus where solar radiation is maximum, diurnal range of temperature increases.

Stevenson screen is used for providing shelter for meteorological instruments, particularly wet and dry bulb thermometers. It is kept 1.25 meters above the ground by legs. It is done so to avoid strong temperature gradients at ground level. Stevenson screen has sides to encourage the free passage of air. For reflecting heat radiation, it is painted white. It was invented by the British engineer and meteorologist Sir Thomas Stevenson.

A device which is used to measure atmospheric pressure is known as Barometer. There are two types of barometers:- mercury and aneroid.

Atmospheric pressure is balanced by a column of mercury in case of a mercury barometer.

Aneroid barometer also called non-liquid barometer. Because of its smaller size and convenience, it is widely used in portable instruments and in aircraft altimeters.

Degree Celsius is the standard unit to measure temperature. It was developed by Swedish astronomer Andres Celsius in 1742. In degree Celsius, zero degrees represents the freezing point of water and 100 degrees represents water’s boiling point at the standard atmosphere. The standard atmosphere is the mean barometric pressure at the mean sea level.

Isohyets are imaginery lines joining places of equal rainfall. These lines are generally drawn on a weather map.

Celsius is the scale which measures temperature. It was developed by Swedish astronomer Andres Celsius in 1742. Freezing point of the water is the temperature at which water starts converting into ice. As per the Celsius scale, zero degrees is the freezing point of the water. The boiling point is the temperature at which water starts converting into vapors. As per Celsius scale, 100 degrees is the boiling point of the water.

The mean annual rainfall is calculated for data collected for a long period of time (30 - 35) years because rainfall is highly variable from day today. It adequately characterizes the rainfall regime in an area and its surroundings. World Meteorological Organization (WMO) recommends continuous 30-year records to calculate mean annual rainfall.

In modern thermometer, mercury is used as it is a reflective liquid. It is bright and opaque, so it’s easy to see movement of mercury inside the capillary tube and to read accurately. Even mercury does not wet the glass. So, if temperature is falling then you do not get inaccurate readings. It is also good conductor of heat. So, it reacts quickly to change in temperature.

• Thermogram is an instrument which is used for creating images based on heat radiation emitted from any object. It has many applications ranging from medical settings to weather stations. Hence A is the correct option.
• The thermometer measures the temperature of the human body.
• Isotherms are the lines joining various points on the map having the same temperature during a given period. Hence B and C are incorrect.

Mean daily temperature is the average temperature in each period of 24 hours. It is measured at 1.5 meters above ground level. Mean daily temperature can be determined by finding out the mean of maximum and minimum temperature of a day.

A Thermogram is a modern instrument that continuously measures and records the temperature and is used in weather stations. It provides information in form of a graph called thermograph.

Thermographs are a good alternative to the digital collection of data. The thermographs are equipped with mechanical or quartz clockwork. Easily it can be switched from weekly recording to daily or monthly recording. They will be delivered with writing pens and a recording paper.

A line on a map connecting places with the same temperature at a given time is known as isotherm. Isotherms are created from regularly scheduled, simultaneous temperature readings at different locations. It shows patterns of temperature on a weather map. It helps in visualizing and interpreting horizontal temperature distribution of an area. The elementary step in temperature data analysis is construction of isotherm maps.

Thermometer is a device which is used to measure temperature. There are two reference points marked on a thermometer. One reference point represents freezing point of water. Freezing point of the water is the temperature at which water starts converting into ice. As per Celsius scale, zero degree is the freezing point of the water. Other reference point represents boiling point of water. Boiling point is the temperature at which water starts converting into vapours. As per Celsius scale, 100 degree is the boiling point of the water.

The mean annual range is an indicator of the variation among the monthly temperature in a year. It is calculated by taking the difference between the highest and lowest mean monthly temperature recorded in a year.

To measure the minimum and maximum temperature in a day, Six’s thermometer is used.  It consists of a U-shaped capillary tube having bulbs at both ends. Mercury is filled in the bend of the U-tube. One of the bulbs is completely filled with alcohol and the other bulb is partly filled with alcohol. Alcohol is the thermometric liquid in case of Six’s thermometer. Change in temperature is recorded due to expansion and contraction of alcohol.

Mean Annual Temperature: The average temperature for the entire year at any given location.

$\dfrac{\Sigma {(\text{Mean monthly temperature})}}{12}$

Rain gauge can accurately measure the rainfall without any loss due to evaporation. It is an instrument used for determining the depth of precipitation that occurs over a unit area. Thus, it measures rainfall. One liter of rainfall per meter squared is equivalent to one millimeter of measured precipitation. A funneled aperture of 150-170 cm is found in standard rain gauges. They are designed as a simple passive collector. A graduated measuring glass is used for determining the amount of precipitation. For the measurement of rainfall, the rain gauze should be placed 30 cm above the ground to prevent the splashing of rainwater.

A standard rain gauge has a funnel with a diameter of 20.3 cm while the measuring cylinder is of 12.5 cm in height. If rain intensity is beyond 12.5 cm, the classification for rainfall is “Very Heavy Rainfall”. Any rain water in excess of 12.5 cm overflows into an outer metal cylinder. This prevents loss of rain water which may otherwise occur through splashing out of the funnel or spilling. The height of 12.5 cm was determined as per the commonly recorded pattern of rainfall in 24 hours. 

It is asking about the instrument not the graph. The Instrument is Rain gauge.

A place, where weather conditions are constantly monitored and recorded, is called a weather station. All data related to weather and environment is recorded here. A weather station has sensors. Sensors include a thermometer to take temperature readings and a barometer to measure the pressure in the atmosphere. There are also sensors to measure rain, wind, humidity and more. Weather Station even has computers having internet connection so that data can be analyzed properly.

A barometer is a meteorological instrument which is used to measure atmospheric pressure. Atmospheric pressure is balanced by a column of mercury in case of a mercury barometer. Mercury is used because its height can be precisely measured. A barometer can also be used to measure altitude because atmospheric pressure changes with distance above or below sea level. There are two types of barometers:- mercury and aneroid. 

Agricultural meteorology is the branch of meteorology that deals with the relationship of weather and climate to crop and livestock production and soil management. Agricultural Meteorology involves the integration of climatological and meteorological data and techniques into agricultural problems, such as crop production, soil moisture, moisture stress, and migration of pests. A good background in basic math and sciences is required.

Peninsular India experience peak summers earlier when compare to north India due to the apparent northward movement of the sun, the global heat belt shifts northward. In March, the highest temperature is about 38° Celsius, recorded on the Deccan plateau. In April, temperatures in Gujarat and Madhya Pradesh are around 42° Celsius. In May, temperature of 45° Celsius is common in the north-western parts of the country.

A climograph is a graphical representation of monthly average temperature and precipitation at a location. From this representation, one may observe the variations in elements, such as humidity levels, which help to indicate the pattern of elements of weather and climate. 

Raindrops start to form in a roughly spherical structure due to the surface tension of water. This surface tension is the "skin" of a body of water that makes the molecules stick together. The cause is the weak hydrogen bonds that occur between water molecules.