Trade Winds - Geography for Kids
North-east trade winds- are winds that dominate the Northern hemisphere. Are defined as any of a consistent system of prevailing winds that. On many oceanic tropical islands the trade winds blow from the east and as the air The vast majority of oceanic tropical islands do not have any available data to verify these In Puerto Rico, the wind blows between northeast and southeast at least 65 . A prehistoric revolution, The University of Arizona Press, Tucsonpp. News & Features Thanks to winds high in the atmosphere, NASA scientists say dust and Scientists have long recognized that high levels of ozone in the South Atlantic are caused by lightning in nearby continents and by burning the northeast trade winds meet the southeast trade winds near the.
Air temperature differences across the Earth's surface both land and water create winds, with warm air being lighter than cold air. Near the equator, the sun heats the sea surface, causing the warm air at the surface to rise and be replaced by the trade winds blowing from subtropical high pressure systems into equatorial low-pressure troughs.
The trade winds blow steadily for days and are among the most consistent on earth. When trade winds move over warm tropical waters, they pick up moisture and bring heavy rainfall to the windward-facing slopes of mountainous areas, contrasting with the downward motion of dry air that creates desert areas on land. Because the area of Earth between the Tropic of Cancer and Tropic of Capricornlying at approximately 23 degrees latitude on either side of the equator, receives more solar heat than the rest of the earth, the warm air creates clouds and rain with thunder-showers there almost every day.
The differences in pressure and temperature between the two sides of the Pacific are caused by the trade winds; air blowing from east to west pushes water, making the sea level higher in the western Pacific, and makes cold water rise toward the surface, making the eastern Pacific approximately 14 degrees F 7.
The warm surface temperature is associated with reversed air pressure patterns and decreasing strength of trade winds, so more water stays in the eastern Pacific off the coast of South America. With the rain pattern shift eastward, the western Pacific can become drier over India and much of southeast Asia. A similar pattern sets up in the Atlantic, resulting in extreme drought in the eastern United States and reduced tropical storm development in the Atlantic Ocean.
The cooler surface temperature is associated with a rain pattern shift westward.
The eastern areas thus become drier, with an increased probability of flooding from monsoons in both India and much of southeast Asia. Hurricanes Atlantic and cyclones Indian Ocean are tropical storms of low-pressure cells. Formation of hurricanes in the Atlantic comes from solar heating of water off the West African coast along the Intertropical Convergence Zone, with high cumulus cloud formation in the low-pressure area along the edge.
These systems are pushed westward by the trade winds, and the rotation is set in motion by the Coriolis Effect. All data from Hispaniola are from the Dominican Republic as no data are available for the Haitian side of the island.
Puerto Rico and Hawaii are part of the United States. The 6 islands in this study are not representative of the 45, tropical islands on Earth. All are in the northern hemisphere and all are in the western hemisphere.
All are near the Tropic of Cancer and none are in the deep tropics. None of the islands are in the Indian Ocean. The largest concentration of tropical islands on Earth is between Asia and Australia and none of the islands in this study are in this part of the world. These are the islands for which data are available on the Internet and if the hypotheses work on these islands it can guide the work of future researchers on other islands.
The islands of this study are well separated from continental landmasses. Future work will be needed to understand the relationship between distance and the effect of continents on the climate of tropical islands.
The large masses of ocean water around the islands of this study buffers the climate and reduces the annual air temperature cycle.
The location of the islands are in Figure 1. Materials and Methods The hypotheses were tested for every oceanic tropical island for which data could be found on the Internet. Typically for each station the metadata includes latitude, longitude, and elevation. For each hypothesis assayed, each island has between 15 and 68 data points. The data were plotted versus longitude and visually examined for outliers, which were excluded.
The Pearson correlation coefficient was calculated, the p-value used was 0. The hypotheses were assayed with climate stations that had at least 7 years of data and in many cases 30 or more years.
The first hypothesis, which states that the western ends of oceanic tropical islands have lower relative humidity than the eastern parts, was assayed only for the island of Hispaniola. The data were the monthly average relative humidity, which were averaged to produce the average relative humidity. The second hypothesis, stating that the diurnal air temperature cycle is larger in the western parts of the islands was assayed for all of the islands.
The monthly air temperature cycle is the average high temperature in a month less the average low temperature in the month.
NOAA's National Ocean Service Education: Currents: Trade Winds
In the tropics, the diurnal air temperature cycle is 65 percent of the monthly cycle [ 26 ], so the monthly average high and low temperature was used as a proxy for the diurnal cycle. A proxy was needed because data on the diurnal air temperature cycle are not readily available. Each station has a value for the monthly difference between high and low temperature and these were averaged to produce a single value for the station over the course of a year.
The hypotheses were also assayed for north-south differences.
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If the trade winds are converging on the equator then it would be logical that the low latitude part of the island would be dryer and have a larger diurnal air temperature cycle. Results The results are in Table 1. The graph of average relative humidity versus longitude for Hispaniola is shown in Figure 2. There are 15 data points. The 13 data points from stations below m above sea level showed a clear trend from 83 to 63 percent relative humidity. The two stations higher than m above sea level were more humid and were excluded as outliers.
The Pearson correlation coefficient was Hypothesis number two predicts that the western parts of oceanic tropical islands will have a larger diurnal air temperature cycle and this was tested with monthly air temperature data. The average monthly air temperature cycles for Hispaniola and Puerto Rico are shown in Figure 3, while Figure 4 has the same data for the four Hawaiian Islands. All six islands had a larger diurnal temperature cycle in the western parts of the islands but the correlations were not significant in the Big Island of Hawaii and Maui.
The hypotheses of this study were assayed 7 times on 6 oceanic tropical islands in two groups in two oceans. The hypotheses were as predicted 5 of the 7 times. The binomial distribution was used to calculate the p-value for this to occur by random chance and the result is 6 times in a million trials.
The testing of the north-south hypotheses produced no significant results. Discussion The correlations in this study are based on the consistency of the easterly trade winds.
In parts of south Asia and the island-rich region between Asia and Australia, the climate is dominated by the monsoon pattern which can include abrupt changes in wind direction and precipitation [ 27 ].
Understanding how the Asia monsoon affects the climatology of tropical islands is crucial in the extension of this study to other areas such as Indonesia and the Philippines; however none of the islands in this study are affected by the monsoon pattern. In Maui the hypothesis on the correlation between longitude and the monthly air temperature cycle has 20 data points, a Pearson correlation coefficient of 0.
It was classified as insignificant but it is right on the edge and with one more station the correlation would be significant. The Big Island of Hawaii is a different story.
With 37 data points, the Pearson correlation coefficient is 0. To be significant a Pearson correlation coefficient of 0. The largest and most populated island used in this study is Hispaniola, which has an area of 76, km2, a maximum elevation of m above sea level, and a population of over 20 million people, split almost evenly between the Dominican Republic and Haiti. The population density of Hispaniola is people per square kilometer. Kauai is the smallest and least populated island in this study.
Kauai has an area of km2, a maximum elevation of m above sea level, a population of 67, and a population density of 47 people per square kilometer. Oahu is the lowest and most densely populated island in the study.
Oahu has an area of km2, an elevation of m, a population of , and a population density of people per square kilometer. The Big Island of Hawaii is the highest in elevation and has the lowest population density. The Big Island of Hawaii has an area of 10, km2, an elevation of m, and a population ofwith a population density of 18 people per square kilometer.
The wind blows from the east, and as the air mass moves over land from east to west it loses moisture to rain and becomes drier. The pattern is simplistic but it produced two hypotheses which could be tested with data that are publically available on the Internet. The hypotheses were successful in predicting observations on widely separated oceanic tropical islands.
The variables used in this study are affected by multiple factors like elevation, proximity to the coast, the shape of mountains, and anthropogenic factors like urban heat islandsthe consistency of the easterly trade winds adds longitude to the list.
A simple correlation with limited data requirements produced useful results even though the distance between Puerto Rico and Hawaii is more than 9, km. Oceanic tropical islands are tiny specks of land spread out over vast distances of ocean. On thousands of these islands, the easterly trade winds shape the environment in predictable ways.
This study is the first part of a larger effort to identify these underlying physical processes that can help improve the management of water and other natural resources on these islands. The easterly trade winds affects not only the humidity and diurnal air temperature cycle but probably also the temperatures of sea surface, rivers, and groundwater. These abiotic conditions shape the environment for plants, animals, bacteria and fungi.
Puerto Rico is a good place to start because its political relationship with the United States has made it one of the most data-rich places on Earth. The goal is science that can improve the management of water and other natural resources in Puerto Rico while at the same time providing insights that can help in the environmental management of thousands of islands where data are sparse.
Puerto Rico is and island but the viewpoint should not be insular but rather one that is inclusive of the tens of thousands oceanic tropical islands with similar climates and environmental problems. Conclusion The consistency of the easterly trade winds on oceanic tropical islands leads to two predictions which can be assayed with data that are publically available on the Internet. The hypotheses that were verified on two islands in the Caribbean and four in the Pacific are that on the western end of the island the relative humidity is lower and the diurnal air temperature cycle is larger.Trade winds
These patterns probably exist on thousands of islands for which there are no readily available data. With more data it should be possible to observe these patterns much more widely.