Monsoon CPR Paper
by
The Professor
Introduction
The Indian monsoon is a weather phenomena that results in heavy rains during the summer months in most parts of India and many parts of SouthEast Asia.Causes of the Indian monsoon are explained as due to differences in temperature on land and adjacent ocean region caused by uneven heating from the sun. In the summer, the land temperature rises above that of the surrounding ocean. The rising air draws in moist air from the ocean. This results in high winds and storms with large amounts of rainfall. In the winter, the land cools to a lower temperature than the surrounding ocean. So, the winds flow from the land to the ocean, and because there is little moisture in the air, there is very little rainfall.
This paper will describe the effects of the Indian monsoon and show data that illustrates its causes and effects on the Indian sub-continent [:(Cmnt by william prothero: Not bad introduction to the monsoon. There is not much background information to underscore the importance of the monsoon to India. The discussion of temperature differences causing the shift in winds is good.):] .
Methods
The data for this paper will come from various web sites that display regional and global climate data. Some of the data will be "climatology" where the parameter is averaged over many years to suppress the effect of yearly variations and show major recurring effects. Data that is pertinent to this study is rainfall, temperature, wind speeds, and atmospheric pressur [:(Cmnt by william prothero: The is a minimal discussion of the data sources. I would have like to see more detail on where the Lamont data come from.):] e.Observations
{link: Mon_MapGd3.jpg}Figure 1 is a location map showing the study region. {link: Mon_YrlyPrecip.jpg}Figure 2 shows a plot of the monthly rainfall, averaged over the years 1961 to 1990, for point A indicated in figure 2. The data are accessible in references 1 and 2. {link: Mon_YrlyTemp.jpg}Figure 3 shows a plot of monthly averaged temperature at the same location as figure 3.{link: Mon_PrcpRgnFeb.jpg}Figure 4 and {link: Mon_PrcpRgnAug.jpg}figure 5 show the precipitation in February and in August. The darker green color of the figure indicates higher precipitation. In the winter it is below 50 mm/month and at its peak, the precipitation reaches 350 mm/month in some locations.
The next piece of data in the puzzle is the wind data. {link: Mon_WindRgnFeb.jpg}Figure 6 and {link: Mon_WindRgnAug.jpg}figure 7 show the wind vectors for the region for the months of February and August [:(Cmnt by william prothero: This is not a bad section. Where it is lacking is that the pressure data and a map of temperature for February and August would also have been nice. There is insufficient discussion of the important features shown in the data.):] .
Interpretations
The monsoon has high precipitation in the summer, caused by moist winds blowing from the sea, dropping their moisture on the monsoon region. In the winter, the wind direction changes and the rainfall is much less.{link: Mon_WntrMdl.jpg}Figure 8 shows a sketch of the situation in the winter. It shows the cool temperatures in the winter, which creates dense air that flows outward from the resulting high pressure region. This air has already lost its moisture and is dry, so the rainfall over India is low.
{link: Mon_SumMdl.jpg}Figure 9 shows a sketch of the situation in the summer. The heating on land causes the air to rise, creating a low pressure region that brings air in from the surrounding regions. This air has blown over the sea surface, so is moist, and as it flows over India, it drops its moisture as rain.
The model and actual data correspond quite well [:(Cmnt by william prothero: The conceptual sketch is good. There is not enough discussion about how the data and the conceptual sketch match up.):] .
So, we have a model that illustrates that the Indian Monsoon is caused by the shift in wind direction, which is caused by changes in land temperatures in winter and summer.
References
1. Lamont data seb site:
Figure 1. World map showing the region of focus for this study. {fig: Mon_MapGd3.jpg}
Figure 3. Average monthly precipitation for the years 1961-1990. {fig: Mon_YrlyPrecip.jpg}
Figure 4. Averaged monthly temperature for the years 1961-1990 for point A in figure 2. {fig: Mon_YrlyTemp.jpg}
Fiugre 5. August precipitation for the study region. {fig: Mon_PrcpRgnFeb.jpg}
Figure 6. August precipitation for the study region. {fig: Mon_PrcpRgnAug.jpg}
Figure 7. Wind vectors for the month of February, in the study region. {fig: Mon_WindRgnFeb.jpg}
Figure 8. Average winds for the month of August, in the study region. {fig: Mon_WindRgnAug.jpg}
Figure 11. Winter situation. Cool temperatures over the Tibetan Plateau and northern Asia create a high pressure region relative to the surrounding sea. Dry winds blow over the Indian subcontinent and the rainfall is low. {fig: Mon_WntrMdl.jpg}
Figure 12. Moist summer winds flow toward the low pressure region north of India, causing high rainfall. {fig: Mon_SumMdl.jpg}