Tag: elements of weather and climate :rainfall and air pressure

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.