The principle of isobar and isotherm diagram in geography and the enumeration and general solution of various problems

1, equivalence or equidistant principle

In contour map, two adjacent contour lines are either equal or equidistant.

2. Low-high principle

The low value is convex to the high value, and the convex value becomes lower.

The high value is convex to the low value, and the convex value becomes high.

3. The principle of small sparse difference and large dense difference

The thinner the isoline, the smaller the difference per unit distance.

The denser the isoline, the greater the difference in unit distance.

Second, the type of isoline

Middle school geography mainly includes: contour line, isobath, isotherm (isobath, isobath), isobath (horizontal isobath, vertical isobath), isorainfall line, isobath line, isosalinity line, isobath line, isobath line, isobath line and so on.

Third, the application of principal isoline

1. Determine the steepness and smoothness of terrain types (mountains, valleys, contours, ridge lines, valley lines, steep cliffs) by interpreting contour lines, determine the direction of mountains, select the location of reservoir dams, select the direction of highway lines, draw topographic profiles and estimate the engineering earthwork.

2. Determine the types of marine landforms such as continental shelf, trench, basin, ridge and submarine volcano. By reading the isobath; Even judge the specific sea area where the topographic map is located; Determine the location conditions of the port.

3. Judging the names of pressure centers by reading atmospheric isobars, such as cyclones, anticyclones, high-pressure ridges, low-pressure troughs, contours, etc. Judge the weather characteristics, wind direction and wind force of different parts. The names of typical pressure centers can also be judged from the isobars on a global scale.

4. Judging the northern and southern hemispheres, seasons and weather, as well as the pressure centers on the mainland and ocean and the prevailing direction of monsoon in this season (East Asia and South Asia) by reading the atmospheric isotherm.

5. By reading the isohyet of the ocean, determine the nature of ocean current, the location of the northern and southern hemispheres of ocean current, the location of the east and west coasts of the mainland and the impact of ocean current on the environment.

6. Determine the windward slope and leeward slope of the mountain through the interpretation of the isohyet and combining with the specific terrain outline, such as the distance from the sea and the direction of the mountains.

7. Interpret the isoline of solar radiation, judge and answer the areas and reasons where the maximum and minimum values of solar radiation appear, the general distribution law and its influence on human beings.

8. Determine the intensity, focal location and epicentral distance of an earthquake at a certain point on the surface by interpreting the isoseismal line.

9. By interpreting the age isoline of seabed rocks, the positions of seamounts and trenches, as well as the positions and trends of submarine tension zones and collision zones are determined.

10. Analyze the population distribution law and its natural, historical, social and economic factors in a certain area by interpreting the population density isoline.

Fourth, the general method of interpretation.

1. Reading equivalent difference (the difference between every two adjacent rows is equal to or equal to 0); The law of change (this is the basis of doing the problem)

2. Look at the density-understand the influencing factors

3. Look at trends and patterns-understand the influencing factors

4. Pay attention to the bending of isoline-you can add auxiliary lines to make it abstract and intuitive.

(1) contour line

1, basic knowledge of contour lines

(1) same row height. ② The vertical interval is consistent or 0 in the whole picture. ③ Contours are closed curves, but they don't intersect each other, but they can overlap at the height of the cliff. ④ The density of contour lines reflects gentle slopes and steep slopes. Slope = vertical relative height/horizontal distance ⑤ The diagonal line indicates the descending direction. ⑥ Several special contours.

0 meter line represents sea level and coastline;

Below 200 meters above sea level, the contour lines are sparse and the terrain is wide and flat;

Below 500 meters above sea level, the relative height is less than 100 meters, the contour lines are sparse, and the curved part is gentle-hilly terrain;

Above 500 meters above sea level, the relative height is above 100 meters, the contour lines are dense, and the valley turns into V-shaped mountain terrain;

The altitude is high, the relative height is small, the contour lines at the edge are dense, and the top is obviously sparse-it is plateau terrain.

2. Determine the terrain type

(1), large terrain type

Plain: elevation

Plateau: altitude >; 500m, small internal terrain, sparse contour lines, steep edge terrain and dense contour lines.

Mountain: elevation > 500m, undulating terrain and dense contour lines.

Hills: 200-500 meters above sea level, with large fluctuation and dense contour lines.

Basin: the elevation is nonstandard, the middle is low, the periphery is high, the internal topography is not undulating, the contour lines are sparse, the edge topography is steep and the contour lines are dense.

(2), small terrain type

Peak: high in the middle and low around.

Valley (or depression): low in the middle and high around.

Valley: A place where the lower part protrudes from the higher part.

Ridge: a place where high places protrude to low places.

Saddle: A lowland between two hills, with high sides and low sides, and symmetrical terrain-the terrain at the saddle is very gentle.

Cliff: where two or more contours overlap.

Canyon: a place with low middle and high sides and dense contour lines on both sides.

Dune: In arid and semi-arid areas, it is formed under the action of wind, and it is crescent-shaped on the contour map. According to the shape of sand dunes, steep slopes are leeward slopes and gentle slopes are windward slopes.

(3), determine the steep slope.

On the same contour map, the denser the contour lines, the steeper the slope; The thinner the contour, the slower the slope.

On different contour maps, the steepness of slope is related to the density (proportion) of contour lines, the size (proportion) of scale and the size (proportion) of vertical interval. Tangent of slope = vertical relative height/horizontal field distance

The type of slope visibility problem: it is solved by making topographic profile. If the topographic profile made by two known points is not blocked by mountains or ridges, the two places can see each other; Note that convex slopes (dense on contour lines) are invisible, while concave slopes (dense on contour lines) are visible; Pay attention to the requirements in the question, and the landscape in the analysis diagram is visible from bottom to top or down.

(4), calculate the height

The altitude is calculated according to the sea level of the Yellow Sea.

Calculation of Relative Height —— Calculating the Relative Height of Steep by Graphic Method

Conversion calculation of elevation difference and temperature difference Every time the altitude rises 1000m, the temperature drops by 6℃.

(5) Topographic profile.

A, find out all intersections of line segments and contour lines (pay attention to distinguish rivers from contour lines)

B, judging the height values of all intersections and the height ranges of two endpoints.

C, draw the corresponding contour lines in the topographic profile.

D. calculate the dimensions of the vertical ruler and the horizontal ruler.

E, mark all intersections and endpoints in the topographic profile (pay attention to the density relationship between points).

F, connect all points with smooth curves.

(6) Terrain type interpretation: Step 1, look at the annotation of contour lines. The terrain below 200 meters marked by straight contour lines may be plains, and the terrain above 500 meters marked by straight contour lines may be plateaus; The second step is to look at the shape of the contour line (including extension direction, bending direction and closure). If the contour line is straight, it may be plain terrain or plateau terrain. If the contour line is closed, it may be hills, mountains or basins (the topography with low inside and high outside is basins or depressions; Closed contour lines are marked with low outside and high inside, and the terrain marked between 200 and 500m is hilly, and the terrain marked above 500m is mountainous). The curve from contour line to high place is valley, and the curve from contour line to low place is ridge. The third step is to determine the size and type of slope by looking at the density of contour lines. To interpret the terrain type in the profile, we must look at the profile shape and the corresponding altitude, and the method can be carried out with reference to the above methods.

3. Application in practice

(1), combined with climate

High altitude and low position. The vertical decline rate is 0.60 C/100m. The basin is not easy to dissipate heat, and the temperature is high, which is easy to cause polluted air to stay. There is more precipitation on windward slope and less precipitation on leeward slope. Because of high plains, the terrain is flat and the wind speed is high, and because of the narrow tube effect, the wind speed in the mountain basin is low. The higher the altitude, the lower the air pressure. The pressure is proportional to the boiling point, and the peak pressure is low and the boiling point is low.

(2), combined with vegetation

Western vegetation is on sunny slopes; Shady plants grow on shady slopes. The distribution of the same vegetation on the sunny slope is higher than the altitude.

(3), combined with river hydrology

Rivers may develop in the valley (high upstream and low downstream); It is impossible to develop a river on a ridge, which is often a watershed. The mountainous terrain forms a radial water system; The basin topography forms a centripetal water system; Parallel mountains form parallel water systems. Rivers with dense contour lines have fast flow velocity and rich water energy; Rivers with sparse contour lines have slow flow speed and convenient water transportation; The size of the basin area (the connecting line of the ridge-the catchment area) determines the flow. Waterfalls are easy to form on steep cliffs in valleys.

(4), combined with geographical location

Selection of traffic routes: Using favorable terrain, we should not only consider the distance, but also consider the stability of the route (spacing, slope, etc.). ). Generally, we bypass between two contour lines and distribute along the contour lines (extension direction) to reduce the slope, and we can only cross one or two contour lines when necessary; When climbing a mountain, choose a gentle slope and pass through the saddle; Try to cross the river as little as possible and build fewer bridges to reduce the construction difficulty and investment; Avoid crossing alpine regions, permafrost regions, underground caves, cliffs, swamps, deserts and other areas.

Selection of diversion route: pay attention to let it divert water from high to low to realize self-flow, and the route should be as short as possible, so that the economic investment will be less.

Selection of pipeline: the line should be as short as possible to save investment; You can cross rivers and mountains, but the geological conditions must be stable.

Selection of reservoir dam site: After the completion of the reservoir, the reservoir site, dam site and the need for resettlement should be considered. (1) Choose the outlet of a narrow river or basin or depression (that is, the "pocket-shaped" area, where the "small mouth" is conducive to dam building, and the "big bag" has a wide hinterland and a large reservoir capacity. Because the engineering quantity is small, the project cost is low); ② Choose places with good geological conditions, try to avoid faults and karst landforms to prevent reservoir earthquakes; (3) Consider the situation of land occupation and relocation, and minimize the inundation of fertile fields and villages and towns. (4) Attention should also be paid to the construction of reservoirs, with sufficient water.

Selection of village sites in mountainous areas: Generally, valley areas are selected, requiring flat and open terrain, close to water sources, convenient transportation and abundant sunshine. The choice of campsite is similar to this.

Urban layout and topography: the plain is suitable for centralized and compact; Mountain area is suitable for scattered and loose type.

Selection of agricultural types: according to the topographic types, landforms and slopes reflected in the contour topographic map, combined with climate and water resources conditions, a reasonable layout scheme of agriculture, forestry, animal husbandry and fishery is put forward according to local conditions; Such as the development of planting in plain areas, forestry and animal husbandry in mountainous and hilly areas. Slope > 25, not suitable for terraced fields, large investment and small income, easy to cause soil erosion, landslides and other natural disasters.

The determination of industrial location: it should be analyzed from many aspects. Factories and mines that pollute the environment should be selected in the lower reaches of rivers, below the perennial dominant wind direction, and in combination with geological and topographic conditions, in places with flat and open terrain, solid foundation and large contour spacing. If the electronic, semiconductor and photosensitive equipment factory needs to be built in a place with clean air and beautiful environment, it should be as close as possible to the origin of raw materials, fuel, water and other resources from the perspective of economic benefits.

Port construction should be considered in sheltered deep-water bay (dense isobath); Avoid rivers with high sediment concentration (sparse isobath-slow flow rate), so as not to cause river siltation. Airports are mostly located in open areas with appropriate slopes.

Weather stations should be built in places with moderate terrain gradient and open terrain. Sanatorium should be built in a place with gentle terrain, pleasant climate and fresh air. Yantian is located on the coastal beach of the plain.

(2) Isotherm

means of interpretation

1. Analysis trend (extension direction): parallel to latitude, that is, east-west trend-latitude factor or solar radiation; Parallel to the coastline-natural or land-sea distribution; Parallel to contours or mountains-topographic factors.

2. Analyze the bending situation: do the horizontal line method-compare the temperature of the bending point and the intersection point; Convex value method-convex height (convex high value area) is low (low value) and convex low (convex low value area) is high (high value).

3. Density analysis: sparse-small temperature difference-July temperature in China, tropical areas, oceans, steep slopes and fronts; Dense-large temperature difference-China 65438+ 10 temperature, temperate gentle slope, land and mountains.

4. Numerical feature analysis: small size, large size, middle walk; The closed curve is big or small; High-value areas-summer continent, winter ocean, warm current flow, low terrain (valleys, basins or depressions) and cities; Low-value areas-winter continent, summer ocean, cold current flow and high terrain (mountains and ridges).

College entrance examination ability requirements:

1, judging the position of the northern and southern hemispheres: the degree of the southern hemisphere isotherm decreases gradually from north to south or increases gradually from south to north. In the northern hemisphere, the isotherm increases gradually from north to south or decreases gradually from south to north.

2. Determine the location of land and ocean: In winter, the isotherm on land bends to low latitude (indicating that the winter temperature of land at the same latitude is lower than that of ocean), and the isotherm on ocean bends to high latitude (indicating that the winter temperature of ocean at the same latitude is higher than that of land). In summer, the isotherm on the land bends to high latitude (indicating that the temperature on the land is higher than that on the ocean with the same latitude), and the isotherm on the ocean bends to low latitude (indicating that the temperature on the ocean in summer is lower than that on the land with the same latitude).

3. Judging the month (65438+ 10 or July): When judging the month, we should pay attention to the difference between winter and summer in the northern and southern hemispheres.

65438+ 10 month: the isotherm on the land in the northern hemisphere bends to the south, and the isotherm on the ocean bends to the north; In the southern hemisphere, the isotherms on land bend to the south, while those on the ocean bend to the north.

July: The isotherms on the land in the northern hemisphere bend to the north, and those on the ocean bend to the south; In the southern hemisphere, the isotherms on land bend to the north, while those on the ocean bend to the south.

4. Judging cold and warm currents: the direction of ocean currents is consistent with the protruding direction of isotherms. The cold current center is lower than other areas at the same latitude, so the isotherm bends to the lower latitude. The warm current center has higher water temperature than other areas at the same latitude, so the isotherm bends to the high latitude.

5. Judging topographic relief: the place where the isotherm on the land protrudes to the low latitude indicates that the terrain is rising; Isotherms protrude to high latitudes, indicating that the terrain has decreased. On the closed isotherm diagram, the closer to the center, the smaller the mountain isotherm value; The larger the basin isotherm value.

6. Judging the temperature difference: In general, regardless of time and space, the isotherms are dense and the temperature difference is large; Conversely, the temperature difference is small. From the characteristics of temperature distribution in the world and China, we can know that: ① The isotherm is dense in winter and thin in summer. Because the temperature difference in winter is greater than that in summer. ② Isotherms in temperate zone are dense, while those in tropical zone are sparse. Because the temperature difference in temperate regions is greater than that in tropical regions with high temperature all the year round. ③ The land isotherm is dense and the ocean isotherm is thin. Because of the complex land surface and large ocean heat capacity, the temperature difference of land is greater than that of sea surface. ④ The isotherms of steep slopes in mountainous areas are dense, while those of gentle slopes in mountainous areas are sparse. ⑤ The front isotherm is dense.

Analyze the influencing factors of temperature

The main influencing factors of temperature are: (1), latitude (2), land and sea (3), topography (4), ocean current, etc.

-If the isotherm is roughly parallel to the latitude and shows an east-west trend, the dominant factor is the latitude factor.

-If the isotherm bends near the coast, it is generally parallel to the coastline and shows a north-south trend, and the dominant factor is the land-sea factor.

-On land, the isotherm bends, which is usually the result of topographic factors.

The temperature in the valley is higher than that on both sides: the isotherm is convex from high temperature to low temperature. Such as Weihe River Basin, Fenhe River Basin and Yarlung Zangbo River Basin.

The temperature in the mountains is lower than that on both sides: the isotherm is convex from low temperature to high temperature. For example, Daxinganling, Changbai Mountain, Taihang Mountain and Wuyishan.

Due to the foehn effect, the temperature of the leeward slope of the mountain range rises: the isotherm protrudes from high temperature to low temperature.

Mountain topography (hills, mounds): the isotherm is closed, low in the middle and high around.

Basin (valley, depression) topography: the isotherm is closed, high in the middle and low around.

-In the ocean, the isotherm bends, which is usually the result of ocean current factors.

The air temperature where the cold current flows is lower than that on both sides: the isotherm is convex from low temperature to high temperature.

The temperature where the warm current flows is higher than that on both sides: the isotherm is convex from high temperature to low temperature. (The direction of ocean current always coincides with the convex direction of isotherm)

(4) Horizontal isobar

1, judging the air pressure system

High pressure center: the pressure center is high and the surrounding area is low.

Low pressure center: low pressure center, high around.

High pressure ridge: high pressure protrudes to low pressure.

Low pressure trough: low pressure protrudes to high pressure.

Saddle area: high air pressure on both sides and low air pressure on both sides, symmetrically distributed.

2, judge the weather phenomenon

Downflow with fine weather prevails near the center of high-pressure system.

It is rainy and rainy near the center of updraft prevailing near the center of low-pressure system.

It is sunny near the ridge of high pressure.

There is rain near the trough of low pressure.

Step 3 judge the wind direction

Wind direction: first create the horizontal pressure gradient force and then recreate the wind direction.

Explanation of wind direction: Wind direction refers to the direction of the wind.

(1), the wind direction in the sky-parallel to the isobar.

(2) Wind direction near the ground-oblique isobar.

(3) We should focus on the wind direction of typhoon (cyclone system) (not only static, but also dynamic).

The typhoon blows northeast wind in the north, southwest wind in the south, southeast wind in the east and northwest wind in the west.

Typhoon blows east wind in the northeast, south wind in the southeast, west wind in the southwest and north wind in the northwest.

(4) Wind direction of subtropical high (anticyclone system)

4. judge the wind.

(1). On the same isobar diagram, the denser the isobar, the greater the wind force; The rarer the isobars, the less the wind.

(2) On different isobars, the magnitude of wind force is related to the density (proportion), scale (proportion) and distance (proportion) of isobars. -Use the calculation method (the same as judging the steepness of the slope)

Step 5 judge the season and month

The Asia-Europe continent or North America continent has a strong high pressure of 65438+ 10 month, with north winter and south summer.

The depression in Eurasia or North America is strong, which is July, summer in the north and winter in the south.

(18) population density isoline

By reading the isoline of population density, this paper analyzes the population distribution law and its natural, historical, social and economic factors in a certain area.