Define the main characteristics of air humidity. Air humidity

To quantitatively characterize air humidity, the following characteristics are used: water vapor pressure, absolute humidity, mass fraction of water vapor, relative humidity, humidity deficit, dew point and dew point deficit.

Water vapor pressure ( e) is the partial pressure of water vapor contained in the air in millimeters of mercury (mm Hg) or hectopascals (hPa). The maximum possible water vapor pressure at a given temperature is called saturation elasticity or maximum elasticity(E) . When the elasticity of water vapor corresponds to the elasticity of saturation, the air becomes saturated with water vapor and the process of condensation or sublimation begins with the formation of water droplets or ice crystals.

Humidity deficiency or lack of saturation(d) – this is the difference between the elasticity of saturation at a given temperature and the actual elasticity of water vapor

d=E-e

Absolute humidity ( a) is the mass of water vapor in grams contained in

1 m3 of air (g/m3). For a saturated space, absolute humidity is called

saturating water vapor or extreme humidity(A) .

Actual elasticity and absolute humidity are directly dependent on

temperature of the evaporating surface, and saturation elasticity and maximum humidity depend on the air temperature (Table 2.3).

Table 2.3. Dependence of saturation elasticity and maximum humidity on air temperature

The relationship between water vapor pressure and absolute humidity has the form:

(e- mmHg), (2.13)

A=0,8 e

(e- hPa), (2.14)

Air volumetric expansion coefficient;

t− air temperature in °C.

Mass fraction of water vapor ( s) - amount of water vapor in grams per

1 kilogram of humid air (g/kg). It is related to the water vapor pressure by the following relationship:

Where: R-air pressure.

s=622 e , (2.15)

Until recently, this characteristic was called specific humidity . If condensation of water vapor or additional evaporation does not occur, then the mass fraction of water vapor does not change with heating, cooling, compression and expansion of air.

Relative humidity ( f) is the ratio of the amount of water vapor actually contained in the air to the maximum possible at a given temperature, expressed as a percentage.

f=a 100% , (2.16)

f= 100% , (2.17)

Relative humidity characterizes the degree of saturation of air with water vapor at a given temperature. It is inversely related to air temperature.

Dew point(td) - this is the temperature to which it is necessary to cool the air so that the water vapor contained in it, at constant values ​​of pressure and mass fraction of water vapor (specific humidity), reaches a state of saturation. When the air temperature is equal to the dew point, the relative humidity is 100% ( t = td, f= 100%). The dew point is always lower than or equal to the air temperature. On weather maps, the dew point is plotted in degrees Celsius, to the nearest tenth, as follows:

Td Td Td 125

td= 12.5°C

td= -2.8 °C

Dew point deficit ( ∆td) is the difference between the air temperature and the dew point.

∆td = t- td(2.18)

The dew point deficit shows how many degrees the air must be cooled so that the water vapor contained in it reaches a saturation state. With sufficient accuracy we can assume that when ∆td£ 4°C the air is humid, and at ∆td> 4°C - dry.

One of the very important indicators in our atmosphere. It can be either absolute or relative. How is absolute humidity measured and what formula should be used for this? You can find out about this by reading our article.

Air humidity - what is it?

What is humidity? This is the amount of water contained in any physical body or environment. This indicator directly depends on the very nature of the medium or substance, as well as on the degree of porosity (if we're talking about about solids). In this article we will talk about a specific type of humidity - air humidity.

From a chemistry course, we all know very well that atmospheric air consists of nitrogen, oxygen, carbon dioxide and some other gases, which make up no more than 1% of the total mass. But in addition to these gases, the air also contains water vapor and other impurities.

Air humidity refers to the amount of water vapor that this moment(and in this place) is contained in the air mass. At the same time, meteorologists distinguish two of its values: absolute and relative humidity.

Air humidity is one of the most important characteristics of the Earth's atmosphere, which affects the nature of local weather. It is worth noting that the humidity level atmospheric air is not the same - both in a vertical section and in a horizontal (latitudinal) one. So, if in the polar latitudes relative indicators air humidity (in the lower layer of the atmosphere) is about 0.2-0.5%, then in tropical ones - up to 2.5%. Next, we will find out what absolute and relative air humidity is. We will also consider what difference exists between these two indicators.

Absolute humidity: definition and formula

Translated from Latin, the word absolutus means “full”. Based on this, the essence of the concept of “absolute air humidity” becomes obvious. This is a value that shows how many grams of water vapor are actually contained in one cubic meter of a particular air mass. As a rule, this indicator is denoted by the Latin letter F.

G/m 3 is a unit of measurement in which absolute humidity is calculated. The formula for calculating it is as follows:

In this formula, the letter m denotes the mass of water vapor, and the letter V denotes the volume of a specific air mass.

The value of absolute humidity depends on several factors. First of all, these are air temperature and the nature of advection processes.

Relative humidity

Now let's look at what relative humidity is. It is a relative value that shows how much moisture the air contains in relation to the maximum possible amount of water vapor in that air mass at a particular temperature. Relative air humidity is measured as a percentage (%). And it is this percentage that we can often find out in weather forecasts and weather reports.

It is also worth mentioning such an important concept as dew point. This is the phenomenon of the maximum possible saturation of the air mass with water vapor (the relative humidity at this moment is 100%). In this case, excess moisture condenses and precipitation, fog or clouds form.

Methods for measuring air humidity

Women know that they can detect the increase in humidity in the atmosphere with the help of their voluminous hairstyle. However, there are other, more accurate methods and technical devices. These are a hygrometer and a psychrometer.

The first hygrometer was created back in the 17th century. One of the types of this device is precisely based on the properties of hair to change its length with changes in environmental humidity. However, today there are also electronic hygrometers. A psychrometer is a special device that contains a wet and dry thermometer. Based on the difference in their indicators, air humidity is determined at a specific point in time.

Air humidity as an important environmental indicator

It is believed that the optimal air humidity for the human body is 40-60%. Humidity indicators also greatly influence a person’s perception of air temperature. So, with low humidity it seems to us that the air is much colder than in reality (and vice versa). That is why in the tropical and equatorial latitudes of our planet, travelers experience the heat and heat so hard.

Today there are special humidifiers and dehumidifiers that help a person regulate air humidity in enclosed spaces.

Finally...

Thus, absolute air humidity is the most important indicator that gives us an idea of ​​the state and characteristics of air masses. In this case, you need to be able to distinguish this value from relative humidity. And if the latter shows the proportion of water vapor (in percent) that is present in the air, then absolute humidity is the actual amount of water vapor in grams in one cubic meter of air.

Air humidity is an important characteristic environment. But not everyone fully understands what is meant by the weather reports. and absolute humidity are related concepts. It is not possible to understand the essence of one without understanding the other.

Air and moisture

Air contains a mixture of substances that are in a gaseous state. Primarily it is nitrogen and oxygen. Their total composition (100%) contains approximately 75% and 23% by weight, respectively. About 1.3% is argon, less than 0.05% is carbon dioxide. The remainder (the missing amount is about 0.005% in total) is made up of xenon, hydrogen, krypton, helium, methane and neon.

There is also some amount of moisture in the air at all times. It enters the atmosphere after the evaporation of water molecules from the world's oceans and from moistened soil. In a confined space, its content may differ from the external environment and depends on the presence of additional sources of income and consumption.

To more accurately determine physical characteristics and quantitative indicators, two concepts are used: relative humidity and absolute humidity. In everyday life, excess is formed when drying clothes and during cooking. People and animals excrete it through breathing, plants as a result of gas exchange. In production, changes in the water vapor ratio can be associated with condensation due to temperature changes.

Absolute and features of the use of the term

How important is it to know the exact amount of water vapor in the atmosphere? Based on these parameters, weather forecasts, the possibility of precipitation and its volume, and the paths of movement of fronts are calculated. Based on this, the risks of cyclones and especially hurricanes, which can pose a serious danger to the region, are determined.

What is the difference between the two concepts? What they have in common is that both relative humidity and absolute humidity measure the amount of water vapor in the air. But the first indicator is determined by calculation. The second can be measured by physical methods with the result in g/m 3.

However, with changes in ambient temperature, these indicators change. It is known that the air can contain a maximum certain amount of water vapor - absolute humidity. But for +1°C and +10°C modes these values ​​will be different.

The dependence of the quantitative content of water vapor in the air on temperature is displayed in the relative humidity indicator. It is calculated using the formula. The result is expressed as a percentage (an objective indicator of the maximum possible value).

Influence of environmental conditions

How will the absolute and relative air humidity change with an increase in temperature, for example, from +15°C to +25°C? As it increases, the water vapor pressure increases. This means that more water molecules will fit in a unit volume (1 cubic meter). Consequently, absolute humidity also increases. The relative value will decrease. This is because the actual water vapor content remained the same, but the maximum possible value increased. According to the formula (dividing one by the other and multiplying the result by 100%), the result will be a decrease in the indicator.

How will absolute and relative humidity change as the temperature decreases? What happens when you decrease from +15°C to +5°C? The absolute humidity will decrease. Accordingly, in 1 cubic meter. The maximum amount of air mixture of water vapor that can fit is smaller. Calculation using the formula will show an increase in the final indicator - the percentage of relative humidity will increase.

Meaning for humans

If there is an excess amount of water vapor, you feel stuffy; if there is too little, you feel dry skin and thirst. Obviously, the humidity of damp air is higher. If there is an excess, the excess water is not retained in a gaseous state and turns into a liquid or solid medium. In the atmosphere it rushes down, this is manifested by precipitation (fog, frost). Indoors, a layer of condensation forms on interior items, and there is dew on the surface of the grass in the morning.

An increase in temperature is easier to tolerate in a dry room. However, the same regime, but at a relative humidity above 90%, causes rapid overheating of the body. The body fights this phenomenon in the same way - heat is released through sweat. But in dry air it quickly evaporates (dries out) from the surface of the body. In a humid environment this practically does not happen. The most suitable (comfortable) mode for a person is 40-60%.

Why is this necessary? In bulk materials in wet weather, the dry matter content per unit volume decreases. This difference is not so significant, but with large volumes it can “result” into a really detectable amount.

Products (grain, flour, cement) have an acceptable humidity threshold at which they can be stored without loss of quality or technological properties. Therefore, monitoring indicators and maintaining them at an optimal level is mandatory for storage facilities. By reducing humidity in the air, it is achieved in reducing it in products.

Devices

In practice, actual humidity is measured by hygrometers. Previously, there were two approaches. One is based on changes in the elongability of hair (human or animal). The other is based on the difference in thermometer readings in a dry and humid environment (psychrometric).

In a hair hygrometer, the pointer of the mechanism is connected to a hair stretched on a frame. It changes its physical properties depending on the humidity of the surrounding air. The needle deviates from the reference value. Its movements are tracked on a scale.

Relative humidity and absolute air humidity are known to depend on ambient temperature. This feature is used in a psychrometer. When determining, the readings of two adjacent thermometers are taken. The flask of one (dry) is under normal conditions. In the other (wet) it is shrouded in a wick, which is connected to a reservoir of water.

In such conditions, the thermometer measures the environment taking into account the evaporating moisture. And this indicator depends on the amount of water vapor in the air. The difference in readings is determined. The relative humidity value is determined using special tables.

IN Lately Sensors that use changes in the electrical characteristics of certain materials are more widely used. To confirm the results and verify the instruments, there are reference settings.

Water vapor pressure - partial (partial) pressure of water vapor in air

Absolute air humidity - the amount of water vapor in grams per 1 m 3

Specific humidity –

Relative humidity (R) is the ratio of water elasticity. Steam at the same temperature in %.

Condensation is the process of transition from gas to liquid

Sublimation - from gaseous to solid (bypassing the liquid state)

Sublimation and condensation conditions:

The presence of water vapor in the atmosphere at saturation levels

Presence of crystallization centers

The structure of the atmosphere. List the layers that make it up, indicating their heights.

Layer name	Layers	By height	Notes
Troposphere		up to 8(18) km (mid latitudes) up to 10(12) km (in polar latitudes) up to 16(18) km (in tropical latitudes)
Bottom (friction layer)	1-2 km	Low clouds and fogs
Average	up to 6 km (above the lower one)	Mid-level clouds
Upper	From 6 to 10(11)	Form upper level clouds and the tops of powerful cumulonimbus
Tropopause		1-2 km (between troposph and stratosph)
Stratosphere		up to 80-85 km
lower (isothermal)	Up to 30-35 km	t is constant and like in the tropopause
middle (warm layer)	From 30(35)-55(60) km	t increases with altitude reaching 50-70° (absorption of ultraviolet solar radiation by ozone)
Top (mixing layer)	55(60) – 80(85) km	t decreases with altitude -50(-70°)
Ionosphere		80(85)-1000km	0.5 of the total mass of the atmosphere
Scattering Sphere		Above the ionosphere	Molecules can overcome gravity
Mesosphere		Up to 80 km
Thermosphere		80-800 km
Exosphere		Up to 3000

Define an atmospheric front and give their classification.

Atmospheric front is a transition zone between air masses, characterized by sharp changes in the values ​​of metrological elements in the horizon. direction.

Classification:

Warm front - moving towards a retreating cold air mass (like a wedge of cold air, warm air rises to 6-7 km).

Cold front – moving towards a retreating warm air mass. Types:

1st type invasion of cold air along the entire surface of the upward movement of warm air

Type 2 – warm air is unstable and contains reserves of moisture. Cold air displaces warm air (ascending vertical movements appear in the warm air mass, which leads to the formation of nomadic nimbus clouds, the upper boundary reaches the tropopause)

Baric topography maps. Characteristic.

Maps of baric topography - based on aerological observations are made for areas (AT850 height 1.5 km above the ground) (AT700 height 3 km), (AT500 - 5 km) (AT300 - 9 km)

List pressure systems. Give them a brief description.

Cyclone (H) is a baric system in the form of closed isobars, with low pressure in the center. The area of ​​convergence of surface winds blows at an angle of 30-40° to the center of the cyclone, counterclockwise.

A trough is an elongated strip of low pressure between 2 anticyclones, which has an axis near which the isobars have maximum curvature

Axis – line of min pressure, line of convergence of surface winds

Anticyclone (B) is a baric system in the form of closed isobars with high pressure in the center, the area of ​​divergence is near the surface. winds. The wind is clockwise, deviates from the isobar towards low pressure by 30°

A ridge is an elongated strip of low pressure between two cyclones, with a pronounced axis in the axis near which the isobars have max curvature. The ridge axis is the max pressure line, the divergence line of surface winds

Baric saddles are an intermediate baric si-ma, between 2 cyclones and 2 anticyclones. The weather is determined by the light of the air mass where it was formed. Winds are weak and unstable. In winter there are radial fogs and wavy clouds on land. In the summer - a powerful bunch. and cumulonimbus clouds with rain and thunder.

Define a thunderstorm and provide a diagram of a thundercloud.

Thunderstorm is the process of condensation of water vapor in the atmosphere, accompanying. Lightning and thunder.

Frontal thunderstorms - when two air masses interact (warm and cold), stretch in a long chain and cover large areas.

Define the order of battle. List what it should provide.

The order of battle is the relative arrangement of aircraft units and subunits in the air to jointly carry out a combat mission.

BP provides:

Successfully overcoming air defense

Full use of the combat capabilities of units and subunits

The best conditions for searching and reaching targets

The best conditions for observing air space

Freedom of maneuver and piloting

Convenience and continuity of control

Aircraft safety from mid-air collision

Safety from being hit by your own ammunition

Definition of BP collection. List the steps. The essence of BP.

Gathering is a maneuver of single (groups) of aircraft in order to build a given BP at a designated time at a designated altitude in an approved area

BP stages:

Takeoff and climb to altitude of BP formation

Exit to the starting point for starting maneuvering

Maneuvering to occupy a given BP

The essence of BP = BP provides

Describe the method of gaining altitude at safe distances.

It is used when taking off as a pair (link) and can be used in cases where the take-off interval is less than the safe time distance for breaking through clouds at safe distances

Describe the method of gaining altitude at safe altitude differences (along different glide paths).

The RBZ monitors the accuracy of maintaining a given direction and the maintenance of safe altitude differences by the crews using the ONI, the PRV operator and the reports of the pilots

General information

Humidity depends on the nature of the substance, and in solids, in addition, on the degree of grinding or porosity. The content of chemically bound, so-called constitutional water, for example, hydroxides, which are released only during chemical decomposition, as well as crystalline hydrate water is not included in the concept of humidity.

Units of measurement and features of the definition of the concept of “humidity”

• Humidity is usually characterized by the amount of water in a substance, expressed as a percentage (%) of the original mass of the wet substance ( mass humidity) or its volume ( volumetric humidity).

• Humidity can also be characterized by moisture content, or absolute humidity- the amount of water per unit mass of the dry part of the material. This determination of moisture content is widely used to assess the quality of wood.

This value cannot always be accurately measured, since in some cases it is impossible to remove all non-condensed water and weigh the object before and after this operation.

• Relative humidity describes the moisture content compared to maximum number moisture that can be contained in a substance in a state of thermodynamic equilibrium. Relative humidity is usually measured as a percentage of maximum.

Determination methods

Karl Fischer titrator

Establishing the moisture content of many foods, materials, etc. is important. Only at a certain humidity are many bodies (grain, cement, etc.) suitable for the purpose for which they are intended. The life activity of animals and plant organisms is possible only in certain ranges of humidity and relative air humidity. Humidity can make a significant difference in the weight of an item. A kilogram of sugar or grain with a moisture content of 5% and 10% will contain different quantities dry sugar or grain.

Humidity measurement is determined by drying the moisture and Karl Fischer titration of the moisture. These methods are primary. In addition to them, many others have been developed, which are calibrated based on the results of moisture measurements using primary methods and standard humidity samples.

Air humidity

Air humidity is a value characterizing the content of water vapor in the Earth's atmosphere - one of the most significant characteristics of weather and climate.

Relative humidity is usually expressed as a percentage.

Relative humidity is very high in the equatorial zone (the annual average is up to 85% or more), as well as in the polar latitudes and in winter inside the mid-latitude continents. In summer, high relative humidity is characteristic of monsoon regions. Low relative humidity values ​​are observed in subtropical and tropical deserts and in winter in monsoon regions (up to 50% and below).

Humidity decreases quickly with altitude. At an altitude of 1.5-2 km, vapor pressure is on average half that of the earth's surface. The troposphere accounts for 99% of the atmospheric water vapor. On average, there is about 28.5 kg of water vapor in the air above each square meter of the earth's surface.

Gas Humidity Measurement Values

The following quantities are used to indicate the moisture content in the air:

absolute air humidity is the mass of water vapor contained in a unit volume of air, that is, the density of water vapor contained in the air, [g/m³]; in the atmosphere ranges from 0.1-1.0 g/m³ (in winter over the continents) to 30 g/m³ or more (in the equatorial zone);

maximum air humidity (saturation limit) is the amount of water vapor that can be contained in the air at a certain temperature in thermodynamic equilibrium (the maximum value of air humidity at a given temperature), [g/m³]. As air temperature rises, its maximum humidity increases;

vapor pressure, vapor pressure the partial pressure exerted by water vapor contained in the air (water vapor pressure as a fraction of atmospheric pressure). Unit of measurement - Pa.

• humidity deficit is the difference between the maximum possible and actual water vapor pressure [Pa] (under given conditions: temperature and air pressure), that is, between the saturation elasticity and the actual vapor elasticity; relative air humidity is the ratio of vapor pressure to saturated vapor pressure, that is, absolute air humidity to maximum [% relative humidity];
• dew point temperature at which the gas is saturated with water vapor °C. The relative humidity of the gas is 100%. With a further influx of water vapor or when air (gas) is cooled, condensation appears. Thus, although dew does not fall at a temperature of −10 or −50 °C, frost, hoarfrost, ice or snow does fall, a dew point of −10 or −50 °C exists and corresponds to 2.361 and 0.063 g of water per 1 m³ of air or other gas under pressure one atmosphere; specific humidity is the mass of water vapor in grams per kilogram of humidified air [g/kg], that is, the ratio of the masses of water vapor and humidified air;

wet bulb temperature is the temperature at which a gas is saturated with water vapor at a constant enthalpy of air. The relative humidity of the gas is 100%, the moisture content increases, and the enthalpy is equal to the initial one.

ratio of mixture components (water vapor content) mass of water vapor in grams per kilogram of dry air [g/kg], that is, the ratio of the masses of water vapor and dry air.
Notes	Literature
Usoltsev V. A.	Rain Drizzle Hail Snow Groats Dew Frost Hoarfrost Ice
Forecast and Clouds Humidity (absolute And