Monsoonal Winds Flashcards
What is a Monsoon?
An annual cycle of dryness and wetness, with seasonally shifting winds produced by changing atmospheric pressure systems; affects India, Southeast Asia, Indonesia, northern Australia, and portions of Africa. From the Arabic word mausim, meaning “season.”
These seasonally shifting wind systems are monsoons (from the Arabic word mausim, meaning “season”) and involve an annual cycle of returning precipitation with the summer Sun.
What drives the monsoons of southern and eastern asia?
The unequal heating between the Asian landmass and the Indian Ocean drives the monsoons of southern and eastern Asia (Figure 6.15). This process is heavily influenced by the shifting migration of the ITCZ during the year, which brings moisture-laden air northward during the Northern Hemisphere summer.
What contributes to the large difference between summer and winter temperatures of the large Asian landmass?
A large difference is seen between summer and winter temperatures over the large Asian landmass. During the Northern Hemisphere winter, an intense high-pressure cell dominates this continental landmass. At the same time, the ITCZ is present over the central area of the Indian Ocean.
The pressure gradient from about November to March between land and water produces cold, dry winds from the Asian interior that flow over the Himalayas and southward across India. These winds desiccate, or dry out, the landscape, especially in combination with hot temperatures from March through May.
What happens with the ITCZ during the northern hemisphere summer and how dose that effect Asia?
During the Northern Hemisphere summer, the ITCZ shifts northward over southern Asia, and the Asian continental interior develops low pressure associated with high average temperatures (remember the summer warmth in Verkhoyansk, Siberia, from Chapter 5). Meanwhile, subtropical high pressure dominates over the Indian Ocean, causing warming of sea-surface temperatures (Figure 6.15b). Therefore, the pressure gradient is reversed from the winter pattern. As a result, hot subtropical air sweeps over the warm ocean toward India, producing extremely high evaporation rates.
What produces monsoonal rains in indea?
By the time this air reaches India, the air is laden with moisture and clouds, which produce the monsoonal rains from about June to September (Figure 6.15b). These rains are welcome relief from the dust, heat, and parched land of Asia’s springtime.
How are human factors affecting the Asian Monsoon?
New studies indicate that warmer temperatures caused by rising greenhouse gas concentrations have increased monsoon precipitation in the Northern Hemisphere over the past few decades. However, other research suggests that rising concentrations of aerosols—principally sulfur compounds and black carbon—cause an overall drop in monsoon precipitation. Air pollution reduces surface heating and therefore decreases the pressure differences at the heart of monsoonal flows.
