What are subtropical anticyclones?

Subtropical anticyclones are semi-permanent synoptic-scale weather systems that influence weather and climate over the subtropical regions around the world. They are concentrated around 25° N–45° N and 25° S–45° S in both hemispheres (Figure 1) and occupy about 40% of the Earth’s total surface area [1].

What cause subtropical anticyclones?

For Miyasaka and Nakamura (2010), the subtropical anticyclones, over the Southern Hemisphere in summer, are a response to local thermal forcing, i.e., there are sea cooling in the eastern sector of the oceanic basins and heating in the adjacent continental areas by sensible heat fluxes.

Why do anticyclones move northwards during winter in South Africa?

How do anticyclones affect SA’s weather in winter? – When it is winter in the Southern hemisphere, the sun is directly overhead in the Northern hemisphere, which causes the heat distribution and pressure belts to shift northwards. – dry air from the Kalahari anticyclone warms up as it subsides.

Where are subtropical anticyclones located?

Subtropical Anticyclones (SAs), also known as Subtropical Highs, are semi-permanent high-pressure systems that cover 40% of the Earth and are centered around 30° latitude in both the Northern Hemisphere (NH) and Southern Hemisphere (SH).

What are the characteristics of a subtropical anticyclone?

General Characteristics of High Pressure Cells  Descending air  Air from upper atmosphere  Adiabatic heating of air at dry adiabatic lapse rate of 1°c for every 100 metres.  Generally sunny, dry and stable conditions  Moves northwards in winter and southwards in summer The Three Anticyclones Key

How does Sverdrup vorticity affect the subtropical anticyclone?

Below the descent, Sverdrup vorticity balance implies equatorward flow that closes off the subtropical anticyclone to the west and induces cool upwelling in the ocean through Ekman transport. Feedbacks, involving, for example, sea surface temperatures, may further enhance the descent in these regions.

How is Rossby wave response to subtropical monsoon heating?

The Rossby wave response to the west of subtropical monsoon heating, interacting with the midlatitude westerlies, produces a region of adiabatic descent. It is demonstrated here that a local ‘‘diabatic enhancement’’ can lead to a strengthening of the descent.

How does the Great Plains jet help the monsoon?

A poleward-flowing low-level jet into a monsoon (such as the Great Plains jet) is required for Sverdrup vorticity balance. This jet effectively closes off the subtropical anti- cyclone to the east and also transports moisture into the monsoon region.