Is Walker circulation normal?

The longitudinal (east-west) circulation across the equatorial Pacific is known as the Walker cell or Walker circulation. We will start by looking at the “neutral” phase (i.e., the normal middle phase) of this circulation.

Where is Walker circulation?

The Walker circulation, also known as the Walker cell, is a conceptual model of the air flow in the tropics in the lower atmosphere (troposphere). According to this model, parcels of air follow a closed circulation in the zonal and vertical directions.

What is Walker circulation?

The Walker Circulation refers to an east-west circulation of the atmosphere above the tropical Pacific, with air rising above warmer ocean regions (normally in the west), and descending over the cooler ocean areas (normally in the east). Its strength fluctuates with that of the Southern Oscillation.

What happens to the Walker circulation during a La Nina event?

During a La Niña event, the Walker Circulation intensifies with greater convection over the western Pacific and stronger trade winds.

What is Walker Circulation caused by?

This circulation, known as the Walker circulation, is caused by the sharp contrast in sea surface temperature across the tropical Pacific Ocean. The western tropical Pacific contains the warmest regions of the world’s ocean, known as the Western Pacific Warm Pool, where the sea surface temperature is above 28°C.

Why does air rise at 60 latitude?

At around 60 degrees N and 60 degrees S, they meet cold air, which has drifted from the poles. The warmer air from the tropics is lighter than the dense, cold polar air and so it rises as the two air masses meet.

What is Walker circulation caused by?

What is the Walker current?

The Walker circulation consists of trade winds blowing from east to west across the tropical Pacific Ocean (blue arrow), bringing moist surface air to the west. In the western tropical Pacific, the moist air rises, forming clouds. The rising air becomes drier as much of its moisture falls to the surface as rain.

Does air rise or sink at 90 degrees latitude?

90 degrees N & S Latitudes: air sinks over the poles and moves equatorward. Polar Easterlies (in N Hemisphere): air between pole and ~60 degrees N&S latitudes moves equatorward.

Why is there high pressure at 30 degrees from the equator?

The air that rises at the equator does not flow directly to the poles. Due to the rotation of the earth, there is a build up of air at about 30° north latitude. Some of the air sinks, causing a belt of high-pressure at this latitude.

Why does air sink at 30 degrees?

The air sink at 30 degree latitude as it is very cool enough at that time. Cooler air will have a higher density which will make the air to sink to the Earth surface create a high pressure area.

Is 30 Degrees North high or low pressure?

Between each of these circulation cells are bands of high and low pressure at the surface. The high-pressure band is located about 30° N/S latitude and at each pole. Low pressure bands are found at the equator and 50°-60° N/S.

How is the Walker circulation related to the ocean circulation?

In addition to the air circulations describe above, there are also ocean circulations associated with the Walker circulation (see figure 21.28b above). As warm near-surface ocean water is pushed from east to west, the deeper cooler water along the eastern Pacific coast rises to the surface to fill the gap.

What is the neutral phase of the Walker circulation?

The longitudinal (east-west) circulation across the equatorial Pacific is known as the Walker cell or Walker circulation. We will start by looking at the “neutral” phase (i.e., the normal middle phase) of this circulation. (Neutral means not El Niño and not La Niña.)

Where does air settle in the Walker circulation?

The ocean water warms the entire way. The end result is relatively warmer surface water in the west and cooler surface waters in the east. Above this large pool of warm water (known to Earth scientists as the Pacific Warm Pool), air rises; above the cooler water in the east, air dries and settles near the surface.

How does the Walker circulation affect South America?

Warm, moist air rises even more over the Maritime Continent and South America leading to above-average rainfall. In the eastern Pacific, where colder than average waters exist, an enhanced downward branch of the Walker Circulation helps to further reduce the region’s already small rainfall totals.