The following figure shows the percentage of spring and summer precipitation in the eastern part of China to the annual precipitation. Please answer the picture (detailed process).

Isoprecipitation line generally refers to the line connecting all points with the same precipitation at the same time on the map. A map composed of isorainfall lines is an isorainfall line map. Generally speaking, it refers to the lines connecting all points with the same precipitation at the same time on the map, and the map composed of isoprecipitation lines is the isoprecipitation line chart. Can be divided into daily precipitation line, monthly precipitation line and annual precipitation line. On the annual precipitation map of China, we can clearly see three obvious isoprecipitation lines, which represent the special geographical significance of China.

Daily precipitation line: it is a line drawn by collecting the precipitation of different research units in a certain area on a daily basis. Because this precipitation line changes too much, it has no good research value. Rarely used.

Monthly precipitation line: it is a line formed by collecting and describing precipitation in units of months. Generally speaking, the average value of the same month for many years is taken as the research data. Because the trend of this linear response is relatively stable, many places begin to use it to interpret the seasonal precipitation law of a place.

Annual precipitation line: it is a map measured and drawn in units of years. The annual precipitation line has different applications. If we study the general law in a macro sense, these lines are formed according to the average value of annual precipitation for many years. If we study the interannual variation of precipitation in a place, we need to know the precipitation situation in a specific year, so as to compare the bending direction and degree with the annual average precipitation line layout and analyze its interannual differences. For example, the annual average precipitation map of the world is drawn with annual precipitation lines.

On the map of annual precipitation in China, you can clearly see three obvious isoprecipitation lines, which represent the special geographical significance of China:

1 800 mm annual precipitation line

Along the Qinling-Huaihe line, turn west to the southeast edge of the Qinghai-Tibet Plateau. The annual precipitation in the east and south of the line is generally above 800mm, which is a humid area, and the annual precipitation in the west and north of the line is generally below 800mm, which is a semi-humid area. Its geographical significance is:

In the traditional sense, the dividing line between North and South

The dividing line between dry land in the north and paddy field in the south

Rice-wheat planting boundary

The dividing line between humid area and semi-humid area

The dividing line between subtropical monsoon climate and temperate monsoon climate

Boundary between tropical and subtropical evergreen broad-leaved forest and temperate deciduous broad-leaved forest

The dividing line between frozen and unfrozen rivers [2] and so on.

2 400 mm annual precipitation line

Roughly along the Daxinganling-Zhangjiakou-Lanzhou-Lhasa line, and finally to the eastern Himalayas, the annual precipitation to the east of this line is generally above 400mm, which belongs to semi-humid areas, and the annual precipitation to the west of this line is generally below 400mm, which belongs to semi-arid areas. Its geographical significance is:

The dividing line between monsoon region and non-monsoon region 2

The boundary between the eastern monsoon region and the arid and semi-arid region in northwest China.

The dividing line between semi-humid and semi-arid areas

The dividing line between agricultural area and animal husbandry area

The dividing line between forest and grassland

The dividing line between the northern region and the northwest region

The dividing line between temperate continental climate and temperate monsoon climate [3]

3 200mm annual precipitation line

From the west of Inner Mongolia Autonomous Region through the west of Hexi Corridor and the northern Tibetan Plateau, this line is the dividing line between arid and semi-arid areas. It is also the dividing line between desert areas and non-desert areas in China.

Isoprecipitation line-significance

1 can judge the difference of regional precipitation distribution.

Its significance lies in that the concentration of isorainfall lines shows that the regional distribution of precipitation is very different. On the contrary, sparse isohyets indicate that the regional distribution of precipitation is small.

Can judge the influence of land and sea.

The isoprecipitation line is roughly parallel to the coastline and decreases from the coast to the inland, indicating that the precipitation is obviously affected by land and sea factors.

3 can judge the terrain effect

Isoprecipitation line is roughly parallel to the trend of mountains, indicating that precipitation is greatly influenced by topography (mountains). The precipitation on the windward slope in mountainous areas is large; There is almost no precipitation on the leeward slope of the mountain range.

4 can judge the inland terrain

Isoprecipitation line is a closed curve with little precipitation. Combined with geographical location, it shows that the terrain plays a role, or lives in an inland position.

5 can judge the influence of ocean currents.

Its basis is that the coastal areas where warm current flows increase precipitation, and the coastal areas where cold current flows decrease precipitation.

6 can judge the influence of atmospheric circulation

Three-circle circulation: controlled by equatorial low pressure zone and sub-polar low pressure zone, with more precipitation;

Subtropical high pressure area and polar high pressure area control, less precipitation;

The west coast of the mainland is controlled by the westerly belt, with a lot of precipitation. If it is lifted by the terrain, there will be more precipitation.

The east coast of the mainland is controlled by the trade wind belt. If there is topographic uplift, there will be more precipitation.

Monsoon circulation: summer monsoon control, more precipitation; Wind control in winter, less precipitation; If winter winds cross the vast ocean and the terrain rises, there may be more precipitation.

7 can judge the influence of the city

If the city has a "rain island" effect, the more the isohyet goes to the city center, the greater the value.

Causes of urban "rain island" effect: prevailing updraft: condensation nucleus; Tall buildings block the weather system.