How to write an English composition about city weather?

Weather is a collection of all phenomena in a specific atmosphere at a specific time. It also includes interaction with the hydrosphere. This term usually refers to the activities of these phenomena in a short period of time (hours or days), as opposed to the word climate, which refers to the average atmospheric conditions over a long period of time. When used without limitation, "weather" is understood as the weather of the earth.

The weather is usually caused by the temperature difference between different places. On a large scale, the temperature difference occurs because the area near the equator gets more energy per unit area from the sun than the area near the poles. On the local scale, because different surfaces (such as oceans, forests, ice sheets or man-made objects) have different physical characteristics, such as reflectivity, roughness or water content, temperature differences may occur.

The difference of surface temperature will in turn cause the difference of pressure. The hot surface heats the air above it, which expands and lowers the air pressure. The resulting horizontal pressure gradient accelerates the air from high pressure to low pressure, forming wind, and the rotation of the earth causes the airflow to bend through the Coriolis effect. The simple system formed in this way can show emergent behavior, thus producing more complex systems and other weather phenomena. Large-scale examples include Hadley circulation, while small-scale examples are coastal breezes.

The strong temperature difference between polar and tropical air produces a jet stream. Most weather systems in mid-latitude areas are caused by the instability of jet streams (see baroclinic). The weather system in tropical areas is caused by different processes, such as monsoon or organized thunderstorm system.

Because the axis of the earth is inclined with respect to its orbital plane, sunlight enters at different angles at different times of the year. In June, the northern hemisphere leans towards the sun, so at any given latitude in the northern hemisphere, the sun shines more directly on that place than in December (see the influence of the sun's angle on the climate). This effect causes the seasons. In thousands to hundreds of thousands of years, the change of the earth's orbital parameters will affect the quantity and distribution of solar energy received by the earth and affect the long-term climate (see Milankovic cycle).

On the earth, common weather phenomena include wind, clouds, rain, snow, fog and sandstorm. Less common events include natural disasters, such as tornadoes, hurricanes and ice storms. Almost all familiar weather phenomena occur in the troposphere (the lower part of the atmosphere). The weather does occur in the stratosphere and can affect the weather in the lower troposphere, but the exact mechanism is little known. [ 1]

The atmosphere is a chaotic system, so a small change in one part of the system will have a great impact on the whole system. This makes it difficult to accurately predict the weather a few days in advance, although forecasters are constantly trying to expand this restriction through scientific research on weather and meteorology. In theory, it is impossible to make useful daily forecasts for more than two weeks, which sets an upper limit for the potential of improving forecasting skills. [1] Chaos theory says that the smallest change of ground motion will increase with time. This idea is sometimes called the butterfly effect, because the movement caused by the butterfly flapping its wings will eventually lead to a significant change in the atmospheric state. Due to the sensitivity to small changes, it is never possible to make a perfect prediction, although there is still great potential for improvement.

The sun and the ocean can also affect the weather on land. If the sun heats the sea water for a period of time, the water will evaporate. Once evaporated into the air, water can spread to the nearby land, thus making it colder.