Weather is nothing but the state of the atmosphere in a specific place and time, in a somewhat broader sense they are meteorological conditions prevailing in a given area within a certain time or a given moment. Please do not confuse the weather with the climate, because climate is the general weather phenomena in a given area in a long-term period, eg 30 years or more. The weather is about short-term phenomena.
What causes the weather?
Weather couse such elements as: atmospheric pressure, wind direction and speed, cloudy skies, air temperature, precipitation, air humidity and visibility.
Atmospheric pressure is the pressure that atmospheric air exerts on the Earth’s surface and on all the bodies in it. Based on the average size of atmospheric pressure on the Earth level, the atmospheric pressure unit is introduced.
1 atmosphere = 1013.25 hPa (hectopascal)
Atmospheric pressure depends on the level of air movement and related processes (wind, cloud formation and others). Atmospheric pressure measurements are made with various types of barometers. Barometers can show pressure in hPa (hectopascal) or in mmHG.
Wind direction and speed
Wind is the horizontal air movement caused by the pressure difference and through differences in the shape of the Earth’s surface. The term wind is used in meteorology almost exclusively to determine the horizontal component of the wind. However, there is a vertical component of the wind and then it is so called. The wind blows from areas of higher pressure to areas of lower pressure.
The direction of the wind is the direction from which the wind blows, i.e. the wind blowing from the west is the western wind. Wind speed or its strength is given:
- km / h
- m / s
- nodes [w] – eng. Knots [kn]
- 1 node = 1 Mm / h = 1852 m / h
The Beaufort scale is used to determine the wind strength.
Cloud is a visible collection of very small droplets of water or ice crystals, or droplets of water and ice crystals simultaneously, suspended in a relaxed atmosphere. This collection may also contain water droplets or ice crystals of larger dimensions and particles of this kind that exist in factory fumes, fumes and dust. The appearance of the cloud depends essentially on the nature, dimensions, amount and spatial distribution of its molecules. It also depends on the intensity and color of the light falling on the cloud and the position of the observer and light source relative to the cloud.
Taking into account the height of occurrence, the clouds are divided into:
Low-level, 0 – 2 km,
Mid-level, 2 – 7 km,
High-level, 5 – 13 km.
Air temperature – is one of the basic meteorological elements, defining the thermal state of the atmosphere. Air temperature is given in Celsius (⁰C) and in Anglo-Saxon countries in Fahrenheit (°F).
The method of converting Fahrenheit degrees to Celsius:
[°F] = [°C] × 9⁄5 + 32
How to convert Celsius to Fahrenheit degrees:
[°C] = ([°F] − 32) × 5⁄9
The air temperature is measured at a height of 2 m above the ground with a thermometer, shielded from direct solar radiation in the meteorological cage.
Atmospheric precipitation – this is all liquid or solid condensation products falling from clouds to the Earth’s surface. Precipitation is divided into vertical and horizontal precipitation, also known as atmospheric sediments. Vertical precipitation includes rain, drizzle, snow, snow krupą and hail. Horizontal precipitation (atmospheric sediments) includes: sham, hoarfrost, frost. Because of the duration, it distinguishes:
Continuous rainfall – they last continuously for at least the hour preceding the date of observation. Continuous rainfall occurs from clouds: stratocumulus, altostratus, nimbostratus
Precipitation precipitates – characterized by a sudden appearance and sudden disappearance, they last for a short time, and in the periods between their occurrence a completely cloudless sky appears. Precipitation falls from clouds: cumulus and cumulonimbus.
precipitation at intervals – when the sky remains completely or almost completely overcast even when the rain is not raining. Rainfall occurs with clouds: stratocumulus and altostratus.
Humidity of the air – is the content of water vapor in the air.
The most popular ways to determine moisture are:
Absolute humidity – mass of water vapor expressed in grams contained in 1 m³ of air, rarely used in meteorology.
Relative humidity – percentage ratio of the partial pressure of water vapor contained in the air to the vapor pressure of water saturated at the same temperature. Relative humidity is expressed as a percentage (%).
Hygrometers are used to measure the humidity of the air.
Meteorological visibility – is the maximum distance from which the observer distinguishes the black object seen at an angle of 20 °, in the daytime, against the sky, near the horizon line.
A special scale of visibility is used to determine the degree of visibility.
Weather measuring instruments
The registration of weather elements is carried out by meteorological stations using the following weather measuring instruments:
- anemometer – a device used to measure wind speed and strength
- rain gauge – a device used to measure the amount of atmospheric precipitation
- thermometer – a device used to measure the air temperature
- barometer – a device used to measure atmospheric pressure
- hygrograph – a device used to measure air humidity
- heliograph – a device used to record the duration of insolation