Climate, Weather, and Geography

A long winter night with clear sky and still air is ideal situation for inversion. The heat of the day is radiated off during the night, and by early morning hours, the earth is cooler than the air above. Over polar areas, the temperature inversion is normal throughout the year.

Tundra: No true summer

In the northern hemisphere the land surface area is much larger than in the southern hemisphere. Hence, the effects of land mass and the ocean currents are well pronounced. In January, the isotherms deviate to the north over the ocean and to the south over the continent.

Convectional rainfall occurs when the energy of the sun (or insulation) heats the earth’s surface and causes water to evaporate, finally changing to water vapour. This warm, moist air then rises, and as it rises it cools. The air reaches a point called the condensation level where it has cooled to such an extent that the water vapour condenses and turns back to a liquid form. This process of condensation high in the atmosphere leads to the development of clouds. As the clouds continue to grow the weight of the water droplets can eventually lead to precipitation. Deserts experience convectional type of rainfall. In deserts, the diurnal range of the temperature is very high. They receive high insolation during the day time in absence of cloud cover, and reflect back this heat during night.

Statement 1 is correct: Mean monthly values of various variables like temperature, rainfall and other weather elements give an idea about the climate of a place. Statement 2 is incorrect: Such mean values of these variables are obtained from records relating to a period of around 35 years. Statement 3 is correct: Climatic maps are one of the best methods to represent average climatic conditions for a month, season or year as a whole.

Horse Latitudes or Subtropical High are subtropical latitudes between 30 and 35 degrees both north and south. This region, under a ridge of high pressure called the subtropical high, is an area which receives little precipitation and has variable winds mixed with calm. The horse latitudes are associated with the subtropical anticyclone and the large-scale descent of air from high-altitude currents moving toward the poles.

Cumulus clouds look like cotton wool and have a flat base. They exist in patches and can be seen scattered here and there.

Precipitation refers to water falling from clouds in liquid or solid form. Rainfall and snowfall are both classic forms of precipitation. Fog, however, is a cloud at ground level consisting of suspended water droplets - it forms by condensation near the Earth's surface rather than falling from clouds.

Sleet is a type of precipitation that forms when it falls through a layer of freezing air.

Both wind and earth are not stationary, i.e., they keep on moving. The change in the direction of wind is basically due to the rotation of the earth.

Winds are the air currents which are generated due to the uneven heating of the earth’s surface. The uneven heating of the earth that causes the movement of air is called atmospheric convection.

Air is always colder in the polar region than latitudes. Movement of hot air from latitudes to the polar region or cold air from the polar region to latitudes can take place, but the movement of hot air from the polar region to the equator is not possible.

During the formation of a cyclone, many events take place. There occurs the formation of a low pressure system at the centre with winds at a very high speed revolving around it. This central region of low pressure is known as the eye of the cyclone.

The swift movement of falling water droplets along with rising air creates lightning and sound, which is known as thunderstorm.

The centre of a cyclone is a calm area called the eye of the storm. Its diameter is about 10-30 km. This region is free of clouds and has light winds. The speed of wind in this region is 150 – 250 km/h.