1. 2 Read the blog (journal entry) in FIGURE 1.2 based on South African berg winds and answer the following questions.
FIGURE 1.2: SOUTH AFRICAN BERG WINDS
BERG WINDS IN KWAZULU-NATAL
Blog one:
Since Sunday we have experienced berg wind conditions here in KwaZulu-Natal. These winds are caused by a high-pressure system lying over the interior of South Africa and this forces the air over the escarpment and down the leeward side of the Drakensberg. Temperatures can rise to as high as thirty degrees Celsius in a few hours. These winds can have a speed varying from 10 km per hour to over 100 km per hour and it can be very destructive.
Blog two:
On Sunday the wind was very strong, and the temperatures here in our district rose from the mid-teens last week to the high twenties yesterday and today. This time of the year is also known as the fire season in KZN. These hot, dry winds are very conducive to fires. A fire driven by a 100 km an hour berg wind is unstoppable. No farmer dare leaves his farm during this time, as a fire could wipe out a lifetime of work.
Questions:
1. 2. 1 According to the blog, on which side of the mountain do berg winds descend?
2. 2. 2 Name the high-pressure system referred to in the blog.
3. 2. 3 Berg winds are associated with the presence of a coastal low pressure.
(a) What is a coastal low pressure?
(b) What role does a coastal low pressure play in the formation of berg winds?
(c) Why are berg winds associated with high temperatures?
Answer (2)
1.2.1 According to the blog, on which side of the mountain do berg winds descend?
Berg winds descend on the leeward side of the Drakensberg Mountains. The leeward side of a mountain is the side that is sheltered from the prevailing wind direction, where descending air often warms and dries as it moves.
1.2.2 Name the high-pressure system referred to in the blog.
The high-pressure system referred to in the blog is typically known as the "continental high-pressure" or "inland high-pressure system." In the context of South Africa, this high pressure develops over the interior of the country.
1.2.3 Berg winds are associated with the presence of a coastal low pressure.
(a) What is a coastal low pressure?
A coastal low pressure is a low-pressure system that forms along the coast. It is typically associated with unsettled weather and can lead to the flow of air from areas of high pressure over the interior towards the low-pressure area along the coast.
(b) What role does a coastal low pressure play in the formation of berg winds?
The coastal low pressure plays a crucial role in the formation of berg winds by creating a pressure gradient between the high-pressure system over the interior and the low-pressure system along the coast. This gradient forces warm, dry air to flow from the high-pressure areas, descend over the mountains, and then warm further as it descends the leeward slopes toward the low-pressure zone.
(c) Why are berg winds associated with high temperatures?
Berg winds are associated with high temperatures because as the air descends down the leeward side of the mountains, it undergoes adiabatic heating. This means that as air descends, it becomes compressed and warms due to the increase in atmospheric pressure. As a result, temperatures can rise rapidly, contributing to the hot and dry conditions often experienced during berg wind events.
Berg winds descend on the leeward side of the Drakensberg Mountains, driven by a continental high-pressure system. Coastal low pressures create a pressure gradient that enhances these winds, resulting in high temperatures due to adiabatic heating as the air descends. The process leads to hot, dry conditions conducive to fire outbreaks in the region.
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