Several Problems in Geography Education of Self-taught Examination (Meteorology and Climate)

Water vapor pressure (e) is the partial pressure of water vapor at atmospheric pressure, which is measured in hectopascals like atmospheric pressure. In the past, air pressure and water vapor pressure were often measured in millimeters of mercury, 1 hectopascal = 0.75008 millimeters of mercury. The partial pressure of water vapor in the air when it reaches saturation at a certain temperature is called saturated water vapor pressure (E). The saturated vapor pressure increases rapidly with the increase of air temperature.

2. Climate

Climate is the general state of the atmosphere in a certain region of the earth for many years, and it is the comprehensive expression of various weather processes in this period. Various statistics (mean, extreme, probability, etc. Meteorological elements (temperature, precipitation, wind, etc.). ) is the basic basis for expressing climate.

3. Air mass

In the horizontal direction, the physical properties of the atmosphere mainly refer to temperature, humidity and stability. Its horizontal scale reaches hundreds to thousands of kilometers, and its vertical scale is about several kilometers to more than ten kilometers. The formation of air mass must have a wide range of uniform underlying surface and suitable circulation conditions. The classification of air masses can be divided into polar air masses (polar continental air masses and polar marine air masses) according to their geographical location. Tropical air mass (also can be divided into tropical marine air mass and tropical continental air mass). In addition, there are mid-latitude air masses, mainly from polar or tropical metamorphic air masses. According to thermal classification, it can be divided into cold air mass and warm air mass.

4. Anti-cyclone

Anti-cyclone refers to the horizontal air vortex with the central air pressure higher than the surrounding air pressure, and it is also the high pressure in the air pressure system. Due to the high air pressure in the center, air flows around from the center. In this process, air is affected by horizontal pressure gradient force, geostrophic deflection force and friction force. The anticyclone in the northern hemisphere, the horizontal airflow in the lower layer diverges clockwise, and the anticyclone in the southern hemisphere diverges counterclockwise. The horizontal scale of anticyclone is greater than that of cyclone. For example, the Mongolian-Siberian high in winter occupies 1/4 of the Asian continent. The central pressure of anticyclone is generally around 1020 ~ 1030 hectopascals, and the highest is 1078 hectopascals. The wind speed in the anticyclone is small, the maximum wind speed on the ground is only 20 ~ 30m/s, and the wind power in the central area is weak.

5. Warm front

In the process of front movement, if warm air plays a leading role, it will push the front to move to one side of the cold air mass. This front is called a warm front. After the warm front crossed the border, the warm air mass occupied the position of the original cold air mass. Warm fronts are mostly active in northeast China and the middle and lower reaches of the Yangtze River, and are often accompanied by cold fronts. When the warm front crosses the border, it is warm and humid, the temperature rises, the pressure drops, and the weather turns cloudy and rainy. Not a cold front. The warm front moves slower than the cold front, which may cause continuous precipitation or fog.

6. Dry and clean air

The general name of chemical components in the lower atmosphere except water vapor and impurities (mainly solid impurities). Or defined as the general name of the gas part in the atmosphere except water vapor. Although water vapor is also a gas, it has the transformation of solid, liquid and gas at room temperature, and its physical properties are very different from other gases, so it is taken out separately.

Dry and clean air is the main part of the atmosphere, accounting for 99.97% of the volume of the lower atmosphere on average (the average water vapor is about 0.03, and impurities can be ignored). In terms of composition, nitrogen, oxygen, inert gas (mainly argon) and carbon dioxide are the main components.

7. gradient wind

In a free atmosphere, when the air moves in a curve, the horizontal movement of the air is called gradient wind when the horizontal pressure gradient force, geostrophic deflection force and inertial centrifugal force reach balance. Because there are two kinds of air pressure systems that do curvilinear motion: high-pressure anticyclone and low-pressure cyclone, in high-pressure and low-pressure systems, the equilibrium state of force is different, and the gradient wind is also different.

8. Front

The front is a narrow transition zone formed by the intersection of cold and warm air currents. The front is formed by the contact of two air masses with different properties, and its horizontal range is equivalent to the horizontal scale of air masses, ranging from several hundred kilometers to several Qian Qian meters. The horizontal width is generally tens of kilometers near the ground, narrow only a few kilometers, wide only a few hundred kilometers, and can be widened to 200-400 kilometers or even wider at high altitude.

9.fog

If the air near the ground is cooled to a certain extent under the conditions of sufficient moisture, breeze and stable atmosphere, the moisture in the air will condense into tiny water droplets suspended in the air, which will reduce the visibility of the ground. This weather phenomenon is called fog. Fog is more common in spring from February to April. When the visibility in the atmosphere is lower than 1 km due to the condensation of suspended water vapor, meteorology calls this weather phenomenon fog. Conditions for fog formation: cooling, humidifying and increasing water vapor content. Fog types: 1, radiation fog 2, advection fog 3, mixed fog 4, evaporation fog 5 and smoke.

10, monsoon

Monsoon, due to the temperature difference between the mainland and the adjacent ocean, forms a wind system with wide prevalence and obvious seasonal changes in wind direction. The wind with this characteristic of atmospheric circulation is called monsoon. The concept of monsoon in the sense of modern meteorology was first put forward by Harley in the late17th century, that is, monsoon is formed by the difference between the sun's heating of the ocean and the land, which in turn leads to the difference of atmospheric pressure. In summer, the ocean has a large heat capacity, slow heating, cold sea surface and high air pressure, while the mainland has a small heat capacity, fast heating and low temperature, so the summer monsoon blows from the cold ocean surface to the warm continent. In winter, on the other hand, the winter wind blows from the cold continent to the warm ocean surface.

1 1, relative humidity

Relative humidity is the ratio of absolute humidity in air to saturated absolute humidity at the same temperature, and the number is percentage. (that is, the amount of water vapor contained in the air at a certain place accounts for the percentage of saturated water vapor at that temperature in a certain time). Relative humidity is expressed in RH. Relative humidity is defined as the percentage of the actual water vapor density (expressed by d 1) in air per unit volume to the saturated water vapor density (expressed by d2) at the same temperature, that is, RH (%) = d1/d2x100%; Another calculation method is: the percentage of actual air vapor pressure (expressed by p 1) and saturated vapor pressure (expressed by p2) at the same temperature, that is, RH(%)= p 1/ p2 x 100%.

12, dew point

That is, the frost point refers to the temperature when the air is cooled below 0℃ and the water vapor in the air (on the ice) reaches saturation under the same pressure.

13, cold wave

Cold wave is a kind of disastrous weather in winter, and people are used to calling it cold wave. The so-called cold wave is a weather process in which cold air from the north invades China on a large scale, resulting in a large-scale sharp cooling and northerly winds. Cold waves generally occur in late autumn, winter and early spring. According to the regulations of China's meteorological department, if the temperature drop caused by cold air intrusion reaches more than 10℃ and the lowest temperature is lower than 5℃ in one day, it is called a cold wave process. It can be seen that not every cold air heading south is called a cold wave.

14, saturated steam pressure

The pressure generated by water vapor contained in the air is called water vapor pressure. The pressure of water vapor in the air cannot increase indefinitely. At a certain temperature, if the water vapor pressure increases to a certain limit, the water vapor in the air will reach saturation. If this limit is exceeded, some water vapor will condense into liquid water. This limit is called the saturated vapor pressure at this temperature. According to theoretical calculation and experiment, it is proved that the saturated steam pressure is related to temperature and increases rapidly with the increase of temperature.

15, frontal cyclone

The front appears in the trough with low pressure, and the front often coincides with the trough line with low pressure. This is because the horizontal airflow converges and rises in the low pressure trough, where the cold and warm airflow meet to form a front; In the ridge of high pressure, the horizontal airflow diverges, and the cold air mass airflow cannot meet and form a front. So only cyclones have fronts. When the cold air mass meets the warm air mass, it forms rain. Surface cyclones are generally related to the frontal surface, which we call frontal cyclones. It is a common weather system in the middle and high latitudes of northern China.

16, climate resources

Climatic conditions conducive to human economic activities are part of natural resources. Include solar radiation, heat, moisture, air, wind energy, etc. It is inexhaustible and irreplaceable. Mainly refers to agricultural climate resources and climate energy. Climate resources are different from other resources and cannot enter the market for trading. Among all kinds of natural resources, climate resources are the most prone to change, and the changes are also the most dramatic. Favorable climatic conditions are natural productivity and resources; Unfavorable climatic conditions destroy productivity and are a disaster. If used properly, climate resources are inexhaustible, but the distribution of time and space is uneven and irreplaceable. Therefore, we should proceed from reality and correctly evaluate the climate resources of a place in order to get reasonable development and utilization.

17, accumulated temperature

Refers to the cumulative sum of daily average temperature in a certain period of time. It is an index to study the relationship between temperature and the development speed of biological organism, and it shows the influence of temperature on the growth and development of biological organism from two aspects: intensity and action time. Generally expressed in℃, sometimes in degrees and days. 1735, Lemire first discovered that plants need a certain accumulated temperature to complete their life cycle, that is, plants need a certain amount of daily average temperature accumulation from sowing to maturity. 1837, the Frenchman J.B. Boussingault multiplied the daily average temperature by the days of development period to calculate the "total heat" required by various crops from sowing to maturity, which is called "degree-day". In 1950s, the Soviet Union was widely used in agricultural meteorological service, and then it was also widely used in agricultural meteorological work in China.

18, dryness (dryness index)

An index representing the dryness of the climate. Also known as the drying index, usually represented by the letter K, it is the ratio of possible evaporation to precipitation, reflecting the water revenue and expenditure at a certain place and time. Obviously, it is more accurate than just using precipitation or evaporation to reflect the dry and wet state of water in a place. Because of the different calculation methods of possible evaporation, there are many expressions of dryness. Some use the annual average temperature or the accumulated temperature of 0. 1 times higher than 10℃ to indicate possible evaporation, while others use the radiation difference to indicate possible evaporation. The reciprocal of dryness is called humidity or humidity index. The isoline with k value of 1.0 is used to distinguish the indicators of humid area and semi-humid area. K< 1 is the humid zone, and k= 1~ 1.25 is the semi-humid zone. This isoline is roughly equivalent to the Qinling-Huaihe line. The K values of Daxing 'anling, Xiaoxing 'anling, Changbai Mountain and Jiaodong Peninsula north of this line are also less than 1. The area of k< 1 indicates that the precipitation is greater than the possible evaporation, and the vegetation is forest; K= 1~ 1.25 is a semi-humid area, and the vegetation is forest grassland and meadow grassland. Some calcium is accumulated in the soil, and some areas are salinized, so drought occurs frequently.

19, urban heat island effect

On a clear and windless summer day, the ground temperature on the island is higher than that of the surrounding sea water, thus forming sea breeze circulation and cumulus convection on the island, which is the performance of the ocean heat island effect. In recent years, urban population is concentrated, industry is developed, traffic congestion and air pollution are serious, and buildings in cities are mostly stone and concrete, with high thermal conductivity and heat capacity. In addition, the building itself can block or weaken the wind, which can make the annual average temperature in the city 2℃ higher than that in the suburbs, or even more. In the spatial distribution of temperature, the city is like a warm island, thus forming the urban heat island effect. The heat island effect is a comprehensive phenomenon of microclimate change caused by people changing the urban surface, which is most obvious in winter and more obvious at night than during the day. This is one of the most obvious features of urban climate.