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Runny nose caused by seasonal weather

Test Point 8. Global pressure belts, wind belt distribution, movement patterns and their impact on climate

Test Point Interpretation There are 7 pressure zones and 6 wind belts in the world, understand their The formation and distribution rules can be explained by three circles of circulation. There are two foundations for understanding the three-circle circulation. One is the thermal circulation of the atmosphere, and the other is the formation of wind and the change of wind direction. The direct cause of the formation of wind is the horizontal pressure gradient force, and the wind direction near the ground is the result of the simultaneous action of the pressure gradient force, friction force and geostrophic deflection force. It mainly focuses on the formation of air pressure belts and wind belts on the earth's surface. There are no requirements for the air pressure and wind direction at high altitudes in the three-circle circulation. The three-circle circulation is an ideal model assuming that the earth's surface is uniform. In fact, the distribution of pressure bands and wind bands near the surface is discontinuous and forms pressure centers. On the basis of the three-circle circulation, the actual conditions of sea level pressure and wind should also be understood to connect theory with practice.

The air pressure belt and wind belt also move periodically with the seasons throughout the year. The fundamental reason is the return movement of the direct sun point. The general model map shows the average distribution of pressure belts and wind belts around the world. Based on this situation, the pressure belts and wind belts generally move northward in summer and southward in winter (summer and winter here refer to the northern hemisphere).

Based on the distribution and movement of air pressure zones and wind zones, and superimposing factors such as the location of sea and land and underlying surfaces, the complex and diverse climates in the world are formed. This is the basic understanding that students need to form.

To explain specifically the impact of the distribution and movement of pressure zones and wind belts on climate, examples can be given rather than requiring a systematic description of the causes of climate types. Good examples of the influence of the distribution of pressure zones and wind zones on climate are tropical rainforest climate (controlled by the equatorial low pressure zone throughout the year) and temperate oceanic climate (controlled by the westerly belt throughout the year); the impact of movement patterns on climate, Good examples of Yueyang's weather are the savanna climate (the alternating control of the trade wind belt and the equatorial low pressure belt), the Mediterranean climate (the alternating control of the subtropical high pressure belt and the westerly belt), and the southwest monsoon (the southeast trade wind moves northward across the summer Deflected from the equator), etc.

Students should be able to read proficiently and draw schematic diagrams of the distribution and seasonal movement of global pressure zones and wind zones.

(1) Thermodynamic circulation

1. Concept: Atmospheric movement caused by uneven heat and cold is the simplest form of atmospheric movement

2. Formation: uneven cold and heat (the fundamental cause of atmospheric movement) → vertical movement of air → difference in air pressure on the same horizontal plane → horizontal movement of the atmosphere → thermodynamic circulation. (As shown in Figure 6-1)

Cooling

High, low, high

Low, high, low

Isobaric surface (line)

Heated

Figure 6-1

3. Issues that should be paid attention to when understanding thermodynamic circulation:

① Air pressure refers to the mass of the atmospheric column supported by unit area, so at the same place, air pressure decreases with increasing height;

②The commonly referred to as high air pressure and low air pressure refer to the high and low air pressure conditions at the same level. Comparing the level of air pressure should be done at the same horizontal height. In the vertical direction, the air pressure below is higher than above.

③The isobaric surface is a surface composed of points with equal air pressure values ??in space. The protruding place on the isobaric surface is the high-pressure area; the concave place on the isobaric surface is the low-pressure area. If the ground is heated uniformly, the isobaric surface is generally in a horizontal state. If the ground is heated unevenly, the isobaric surface will tend to be convex or concave.

④ To determine the level of air pressure, both the height factor and the unevenness of the isobaric surface must be considered.

The application of atmospheric motion in life:

①Sea and land wind, a form of atmospheric motion formed by the difference in thermal properties of sea and land. During the day, under the sun's rays, the land heats up quickly, the temperature is high, the air expands and rises, and the air pressure near the ground decreases (the pressure in the upper air increases), forming a "sea breeze" (see Figure 6-3 below); at night, the situation is just the opposite, and air movement forms "Land breeze" (see Figure 6-4 below),

②Valley wind: During the day, the air on the hillside is strongly heated, causing the warm air to rise along the hillside, forming a valley breeze (see Figure 6-5 below) ). At night, the air on the hillside cools rapidly and becomes denser, so it slides down the slope and flows into the valley, forming mountain wind (see Figure 6-6 below).

③Urban wind: Due to the concentrated and increasing urban population, developed industry, residents’ lives, industrial production and transportation consumption

A large amount of fuel releases a large amount of waste heat, causing the urban temperature to rise Higher than the suburbs, forming an "urban heat island". When the atmospheric circulation is slightly

weak, due to the existence of urban heat islands, the air rises in the city and sinks in the suburbs, forming a

small thermal circulation between the city and the suburbs. , called urban style. Studying urban wind is of great significance for urban environmental protection: enterprises with serious pollution should be located outside the sinking distance of urban wind, and green belts should be deployed within the sinking distance of urban wind.

(2) Horizontal movement of the atmosphere? Wind

1. It can be seen from the thermodynamic circulation that one of the direct consequences of uneven cold and heat is the creation of air pressure differences on the horizontal plane, which prompts the atmosphere to flow from places with high pressure to places with low pressure. It can be seen that the horizontal pressure gradient force is the direct cause of the formation of wind. It is necessary to understand the relationship between the three forces that affect the wind direction (see Table 6-1)

Force

Concept

Direction

The relationship between atmospheric movement and isobars

Friction force

Refers to the force generated between the contact surfaces that hinders the movement of the objects when two objects in contact with each other move relative to each other.

Opposite to the wind direction

Under the influence of friction, when the resultant force of local rotation deflection force and friction force balances with the pressure gradient force, the wind direction crosses the isobars obliquely , blowing from high pressure to low pressure

Georotation

Deflection

Force

The force produced by the rotation of the earth that deflects horizontally moving objects Force

Perpendicular to the wind direction

Without the influence of friction, when the local rotation deflection force increases to be equal to and opposite to the pressure gradient force, the wind direction is equal to the pressure gradient force. Lines are parallel

Pressure gradient

Force

The force that causes the atmosphere to flow from a high-pressure area to a low-pressure area is the driving force behind the horizontal movement of the atmosphere and is responsible for the formation of wind. Direct cause

Along the direction perpendicular to the isobaric surface, from high pressure to low pressure

The wind direction is perpendicular to the isobaric line and does not exist on the rotating earth

2． Characteristics of wind direction under different circumstances;

Wind

Ideal state

High-altitude wind

Near-surface wind

Function Force

Horizontal pressure gradient force

Horizontal pressure gradient force, geostrophic deflection force

Horizontal pressure gradient force, geostrophic deflection force, friction force

Wind direction

Vertical isobars, flowing from high-pressure areas to low-pressure areas

Parallel to isobars

There is an angle between the isobars , blowing from high pressure to low pressure

3. Interpretation of Isobar Diagram

(1) Isobar Diagram: The horizontal distribution of air pressure at the same altitude.

(2) Interpretation of isobars: first identify the basic form of the air pressure field, secondly determine the wind strength and direction, and finally analyze weather changes.

(3) Interpretation rules:

①The arrangement and value of isobars:

Low pressure center? Similar to the basin (center) in the contour map (is updraft)

High pressure center? Similar to the top of the mountain in the contour map (the center is downdraft)

High pressure ridge (line)? Similar to the contour map Ridge (ridge line)

Low-pressure trough (line)? Similar to the valley (trough line) in the contour map

②The density of the isobars: (determines the wind force Size)

Are the isobars dense? The pressure gradient force is strong? The wind force is strong

The isobars are sparse? The pressure gradient force is small? The wind force is small

③Waiting Determine the wind direction (any point) and weather situation on the isobar chart:

On the isobar chart, the wind direction at any location is drawn as follows:

The first step is to isobaric In the line diagram, draw the tangent line through the point as required and make a dotted line perpendicular to the tangent line. The arrow points from high pressure to low pressure, but does not necessarily point to the center of low pressure. It is used to indicate the direction of the pressure gradient force;

Figure 6-8

In the second step, after determining the southern and northern hemispheres, face the direction of the horizontal pressure gradient force and deflect it to the right or left at an angle of 30° to 45°, and draw a solid arrow. The wind direction at that point. Take the Northern Hemisphere as an example, as shown below: Weather conditions: including temperature, humidity, wind direction, air pressure and other indicators.

a. Wind blowing from high latitudes to low latitudes? Cold and dry

b. Wind blowing from low latitudes to high latitudes? Warm and moist

c. When low pressure passes through, the weather will be cloudy and rainy; under the control of high pressure, the weather will be sunny

(3) The formation of pressure belts and wind belts

1. Atmospheric circulation: (1) Concept: global regular atmospheric movement; function: promote the exchange of heat and water vapor between high and low latitudes, sea and land, and adjust the global water and heat distribution

- Directly control various places The formation of climate types.

2． Three-circle circulation: (1) Influencing factors: uneven heating at high and low latitudes, geostrophic deflection force

Figure 6-10

(2) Situation: low-latitude circulation (0°~ 30°), mid-latitude circulation (30°~60°), high-latitude circulation (60°~90°) (3) Surface performance: seven pressure zones, six wind zones, the equatorial low pressure is symmetrical about the north-south axis, high and Low pressures are distributed alternately, with wind belts in the middle

(4) Regional differences in world precipitation under the influence of pressure zones and wind belts:

Controlled pressure zones and wind belts

Atmospheric movement conditions

Amount and type of precipitation

Equatorial rainy belt

Equatorial low pressure belt

Mainly rising

Mainly convective rain

Subtropical rainless zone

Subtropical high pressure zone

Mainly subsidence

Less , except for the east coast of the mainland

Temperate rainy belt

Westerly belt and subpolar low pressure

Many frontal cyclone activities

Many frontal rains and cyclonic rain

Polar rainless zone

Polar high pressure zone

Mainly subsidence

Less