Climatology

79. What is the difference between weather and climate? Using mid-latitude cyclones as an illustration, give an example of each.
 * Weather is the instant state of the atmosphere at a place, while climate is the characteristic weather at a given place and time. (Dr. Wax, Lecture 1, my notes) So using a mid-latitude cyclone as an example, for weather you could say that the weather associated with a mid-latitude cyclone can be cool and humid, warm and humid, cold and dry or involve precipitation, depending on your position relative to the mid-latitude cyclone. (Atmosphere. Lutgens/Tarbuck. p. 245) And for climate, you could say that mid-latitude cyclones tend to form in winter over tropical desert regions that are poleward of the intertropical convergence zone or ITCZ. (Climatology. Hidore et al. p.277) **
 * JL **
 * MLC's form in the mid-latitudes (region between southern Florida and Alaska- essentially the area of the westerlies) in conjunction with the polar front. **
 * -PM **

80. Explain the climate sub-disciplines of Paleoclimatology and Synoptic Climatology. Give an example of each.
 * paleoclimatology – a branch of climatology that uses surrogate data to study climate prior to the period of direct measurement. Examples: sediments, ice cores, tree rings, rocks, corals, microfossils, shells **
 * synoptic climatology – a study of climatology that relates local and regional climates to atmospheric circulation patterns. Examples: heat waves, Alberta clippers, flash floods **
 * MLS **
 * Looks good - EM **

81. Understand the main climate controls and be able to explain how they modify climate. [Continentality, Latitude etc.] __ **Understand the main climate controls and be able to explain how they modify climate. [Continentality, Latitude etc.]** __
 * The temperature that occurs at any location is essentially a result of the net radiation available and the way that radiation is budgeted. The amount of net energy and the disposition of that energy at the surface vary depending upon a number of factors. These factors include latitude, surface properties, position with respect to warm or cool ocean currents, and elevation. __Latitude:__ If the earth were a homogenous body without the land-ocean distribution, its temperature would change evenly from the equator to the poles. The major factors that alter the zonal solar climate and hence the patterns of temperature over the globe are of two types. First are factors that are due primarily to geographic location on the earth’s surface. This basically determines the amount of energy received from the sun. In contrast to these location factors are temperature characteristics that result from the transport of energy by the mobile atmosphere and ocean. This dynamic effect can substantially change the temperature of a place. __Surface properties:__ The disposition of solar energy striking a surface largely depends on the type of surface. This refers to albedo. Surfaces with high albedo absorb less incident radiation, so there is less total energy available. Polar icecaps are maintained because they reflect as much as 80% of the solar radiation falling on them. Even if two surfaces have similar albedos, the incident energy does not always result in similar temperatures because the heat capacities of the surfaces may differ. The specific heat of water is five times greater than that of rock material and the land surface in general. The same amount of energy applied to a land surface and a water surface would result in the land becoming much hotter than the water. The difference increases due to the different heat conductivity of the earth materials and the water. Land masses heat much more rapidly than oceans in summer. Because this heat concentrates near the surface, it rapidly radiates to the atmosphere as winter approaches. Land masses tend to experience extreme temperatures, whereas water bodies are more equable and show less change. Net energy (that which is received but not radiated back to the atmosphere) is passed to the air as sensible heat or used to evaporate moisture from the surface and transferred as latent heat. Over the oceans evaporation is continuous whereas on land, it is contingent upon the amount of water available at the surface. The pattern of temperature follows sensible heat flow. Temperatures in moist environments will never experience the very high temperatures found in arid locations. Coastal locations will have smaller temperature ranges than inland locations. Inland cities, especially in the northern hemisphere, have the highest temperature ranges. This is defined by the meteorological term __continentality__ which is a measure of the continental influence on weather and climate. __Aspect and Topography:__ The combined influences of the steepness and direction a slope faces determine its aspect. A north facing slope may have snow while a south facing slope is bare. Slope aspect influences many natural phenomena. Topography plays an important role in the climates of some lowlands. On a continental scale, mountain ranges that run north-south have a very different effect from those that run east-west. The biggest imbalance of energy is between the tropics and the poles. **** Climatology – An Atmospheric Science; ** ** Pgs 45-55 PB **


 * Looks good! **
 * I would like to add the following from notes from Dr. Wax's lecture: **
 * 1. Individual elements of weather- combined effects of temp/humidity/wind on evap/cond/precip Ex-Lake Effect Snow **
 * 2. Global pressure and wind systems- prevailing wind direction, intensity, high or low pressure, circulation patterns **
 * 3. Air masses- source regions/path of movement **
 * 4. Storms- such as MLTC, tornadoes **
 * PM **

82. Explain why we have seasons on Earth. In which latitudinal zone do we find an energy deficit? 83. Why? Where do we find an energy surplus and why? Theoretically, how would climate change if earth’s tilt were increased to 24 degrees? How would earth’s climate be different if earth were not tilted at all?
 * The earth revolves around the sun in an orbit that takes 365 ¼ days. The earth is tipped on its axis 23.5 degrees. This means that the earth presents different faces to the sun in its complete revolution. At the equinoxes, approximately March 21 and September 21, the earth’s equator faces directly perpendicular to the sun’s rays. This means that nights and days are each 12 hours long all over the earth. At the summer solstice, approximately June 21, in the northern hemisphere the sun’s rays strike perpendicular at the 23.5 degree north latitude line. This means that at that time, more area of the northern hemisphere receives sunlight for longer days, warmer weather, and it is summer time. The north pole region receives sunlight 24 hours a day. At this time, in the southern hemisphere, the sun is at a minimum, it is winter time, with colder temperatures, and the south pole receives 24 hours of dark nights. **
 * This pattern is reversed on the December 21 solstice, when the sun strikes perpendicularly to the 23 ½ degree south latitude line. This means that the seasons at this time of year are reversed, with it being summer in the southern hemisphere and winter in the northern hemisphere. At this time the earth is also in its closest location to the sun as the revolution is slightly elliptical in shape. **
 * The differential heating of the tropical regions of the earth creates a heat energy imbalance that air and water circulation patterns work to rebalance, moving heat toward the poles from the equator. The heat balance is a surplus, gaining more radiation than what is lost, in the areas between approximately 40 degrees north latitude to 40 degrees south latitude. Areas poleward from that line in each hemisphere are at a deficit, radiating more heat that they receive, **
 * (Balance info Atmosphere, pg 58) **
 * LK **
 * Looks good! GD **
 * The heat balance is a surplus, gaining more radiation than what is lost, in the areas between approximately 40 degrees north latitude to 40 degrees south latitude. Areas poleward from that line in each hemisphere are at a deficit, radiating more heat that they receive. **
 * If the earth were tipped at 24 degrees, sunshine would strike on the solstices at the 24 degree latitude in either the north (June) or south (December). This would mean that more of each hemisphere would be warmed in the summer or cooled in its winter, leading to more extreme weather as the earth’s temperatures were balanced. If there were no tip on the axis (zero degrees) all days and nights would be equal year round, and weather would be more closely approximate to our spring and fall as it occurs now about the dates of the equinoxes. **
 * (Balance info Atmosphere, pg 58) **
 * LK **
 * Looks good! GD **

84. Explain the many factors that lead to the formation of deserts on earth. //**DESERTIFICATION**// **The alteration of the land to desertlike character by human activity is illustrated by the occurence of population of people and livestock exceeding the capacity of the precipitation to support them. A dry cycle begins, grazing and cultivation increases and vegetation and soils decrease.** 85. Explain the differences in climate between a continental and a maritime location. Use Seattle,WA and Fargo, ND in your answer. [Assume similar latitude and altitude] 86. Understand Earth's General Circulation features and how they influence climate around the world. How do these features shift seasonally?
 * The four main causes that contribute to the formation of deserts are:**
 * //HIGH PRESSURE REGIONS//****The Earth is not heated equally by the sun. At the Equator, which receives the most sun's heat, hot air rises creating a zone of low pressure. The air spreads towards the tropics, cools down and descends. Much of the moisture is lost now as rain. As these dry winds sink, they create areas of high pressure where most of the deserts are found - at the Tropics of Cancer and Capricorn. An example of a desert formed by this is the Sahara//.//****//DRY AIR CURRENTS//****Most rain-carrying currents come from the sea, picking up moisture along the way. The air gets drier and drier inland, therefore creating deserts at places where little rain fall (arid land). These deserts are called continental deserts because of their location inland. They have the most fluctuating temperatures in the world (example: in Gobi, temperatures are between 45ºC in summers and -40ºC in winters). //RAIN SHADOW// Some places are sheltered from rain-bearing winds by mountain ranges. The wind rises from the sea to the mountains, cooling and raining on the windward side of the mountain. As it reaches the leeward side of the mountain, the wind is dry, therefore there is little rain. Deserts are formed in the rain shadow of mountains. An example of a desert formed by Rain Shadow is Death Valley, USA.****//COLD OCEAN CURRENTS//****Water is constantly circulating around the oceans as sea currents, which is either warm or cold. Water from Polar Regions sweeps towards the equator along the western coasts of continents. These cold currents cool the air, forcing it to rain over the sea, causing deserts to form at the coast. When warm air currents meet cold seas, moisture reaches the coast by fog. The rainfall does not penetrate inland and formed deserts.** **//[]//**
 * Climatology. Hidore et all. pg. 279 PB**
 * [] [] PB**
 * Seattle, WA ( 47°36′35″N122°19′59″W) (Elevation 0-520ft- 158m) climate is temperate marine – mild wet winters and warm dry summers. It falls within the cool, dry-summer subtropical zone (Csb) with cool summer Mediterranean characteristics. Temperatures are moderated by Puget Sound, the Pacific Ocean, and Lake Washington. Pacific storms are blocked by the Olympic Mountains and the Cascade Range shields the Arctic air. Fargo, ND (46°52′17″N96°48′31″W / 46.87139°N 96.80861°W / 46.87139; -96.80861) (Elevation 904ft -274m) is located in the Great Plains away from both mountains and oceans. It has a humid continental climate (Dfb) with long, cold, windy, snowy winters and short highly variable spring and fall seasons. Summers are warm with frequent thunderstorms.**
 * General circulation moves energy from regions with a net surplus (between 35S and 35N) to regions with a net deficit (poleward of 35S and 35N). The atmosphere transfers 60% of the energy and the oceans transfer the remaining 40%. (Climatology. Hidore et al. p. 91) **
 * Atmospheric energy transfer is represented by the three-cell model. This model has three cells of atmospheric circulation: the tropical cell (0-30 degrees latitude; location of the Northeast and Southeast trade winds, in the Northern and Southern hemispheres, respectably), the mid-latitude cell (30-60 degrees latitude; location of the Westerly winds) and the Polar cell (60-90 degrees latitude; location of the Polar easterlies). At the borders of the cells are pressure belts: the Equatorial low belt (0 degrees latitude), Subtropical High belts (30 degrees latitude), Subpolar low belts (60 degrees latitude) and the Polar highs (90 degrees latitude). (The Atmosphere. Lutgens & Tarbuck. p. 198-199) **
 * At latitudes where the low pressure belts are located, rising air and precipitation will be prevalent. Where the high pressure belts are located, sinking air and clear weather will predominate. (The Atmosphere. Lutgens/Tarbuck. p. 200) **
 * The pressure belts and associated winds will shift north and south during the year due to the changing temperature distributions throughout the seasons. Since the general circulation will determine the general energy (temperature) and moisture for a given area, this migratory pattern will introduce the chance for changing climatic conditions at some locations. Other factors, such as altitude and whether a location is maritime or continental must also be considered. (Climatology. Hidore et al. p. 98) **
 * JL **

87. What is a monsoon? Be sure to explain how the South Asian monsoon works. Looks good - EM 88. What are the Cfa climates? Where on Earth are they generally found?
 * A monsoon is a seasonal pressure shift that gives distinct dry (winter) and wet (summer) seasons at a given location. In winter, cool, dry winds blow off the land towards the sea. In summer, warm, moist air blows from the sea towards the land. **
 * The south Asian monsoon is driven by seasonal shifts in the Intertropical Convergence Zone or ITCZ. In winter, the ITCZ is located south of the continent over the sea and cool, dry air blows southward from the Tibetan plateau towards the sea. In summer, the ITCZ is located in the Himalayan region and warm, moist air blows towards the continent from the sea. (Climate. Hidore et al. p. 98. The Atmosphere. Lutgens & Tarbuck. p. 202) **
 * JL **
 * The Cfa climates are humid, subtropical climates located on the Eastern sides of continents in the 25-40 degree latitude range. Examples include the southeastern U.S., eastern China and Eastern Australia. (The Atmosphere. Lutgens & Tarbuck. p. 436) **
 * JL **
 * Looks good -PM **

89. Explain what General Circulation feature is most responsible for their formation (Cfa climates)– and how. T ** he tropical summers in Cfa regions are due to the dominating influence of maritime air masses. In summer, the western portion of oceanic subtropical anticyclones moves inland over the relatively warmer continents. This causes increasing atmospheric instability and precipitation. (The Atmosphere. Lutgens & Tarbuck. p. 436) **
 * JL **
 * Looks good -PM **

90. Be sure to understand the Water Balance terms. Be sure you understand what it means when PPE.
 * PE = Potential evapotranspiration **
 * P = Precipitation **
 * P – PE = The difference between precipitation and potential evapotranspiration. It provides the amount of moisture available after evapotranspiration requirements have been satisfied. The excess above the difference will either go to soil water or occur as runoff. **
 * ST = The amount of moisture stored in the soil (4 inches is the base value) **
 * ΔST = The change in storage since the previous month **
 * AE = Actual evaporation **
 * D = Deficit **
 * S = Surplus **


 * As long as P>PE then the ST amount remains 4 **
 * When P>PE then AE = PE **
 * PE>P When the amount of precipitation is less than the potential evapotranspiration then plants draw on the available soil moisture and the soil storage falls below capacity. The water in storage (ST) will make up the deficit. This will result in a change in storage (ΔST). A deficit period will exist as long as (P+ST) PE then the 4 in of water must be returned to ST before any surplus can occur. **


 * When P PE There is a surplus of water, ST will be replenished or runoff will occur **

91. Explain the significance of ‘Wonder Rice’. How/why was this crop developed? How is climate maximized by this plant?
 * page 77 (Climatology 3rd Edition) GD **
 * Looks good -PM **
 * Wonder rice is a strain of rice developed via genetic engineering to get maximal utilization of radiant energy. Because light rays do not penetrate well into stands of plants, wonder rice was bred to have vertical upper leaves and horizontal lower leaves. This allows for maximal photosynthesis by this plant strain using the available radiant energy. (Dr. Wax. Climatology lecture 10. My notes.) **
 * JL **
 * Looks good -PM **

92. Explain how climate affects architecture: how would homes be built [with climate in mind] in the tropics, deserts, mid-latitudes etc. Also include the effects of landscaping, building site etc. Hidore, et.al.Climatology pgs 327-330 PB In the **hot wet tropics**, houses should provide maximum ventilation and shade, while walls should be open or supplied with movable shades. Roofs must be water proof. In **tropical deserts** mud and straw are the basic materials because the high heat capacity of adobe helps maintain an even temperature in the building. The thick walls with minimum window space and the homes built close together maximize existing shade. **Savannah areas** have homes that are conical or dome shaped to promote drainage during wet spells. They are constructed of grass, mud, and branches as well as animal skins. Cement block types are replacing these traditional dwellings. The wet and dry zones are challenged in constructing dual purpose dwellings. In the **Mediterranean zone** for example there are conditions from arid regions and cool wet regions. Most older dwellings have an open courtyard that are shaded during the day and function as radiators at night. There are further modifications of fountains and pools within the courtyard. Substantial homes use heat in the winter. Cold, **polar regions** use an igloo, which represents a building well adapted to hostile conditions. It is hemispherical, minimizing area exposure and is streamlined to combat high winds. It is constructed of dry snow blocks that are piled one on the other in an inward spiral. In summer, the moderate temperatures and long days need turf, earth, and driftwood constructed dwellings which are used to construct sod roofed structures. **Mid latitude continental climates** with severe winters and warm moist summers have portable dwellings such as the yurt tent of Asia and the Native American tepee. 93. What is Hyperthermia? Describe the causes and symptoms. What can a person do to prevent Hyperthermia?
 * //What is Hyperthermia? Describe the causes and symptoms.// Hyperthermia occurs when the body produces or absorbs more heat than it can eliminate. When a highly elevated body temperature is achieved, it can become a medical emergency which if unattended, can lead to disability or death. Prolonged exposure to excessive heat or heat and humidity can lead to heat stroke with is a symptom of hyperthermia. Dehydration associated with heat stroke can cause nausea, vomiting, headaches, and low blood pressure, leading to fainting or dizziness. Heat stroke is due to environmental exposure to heat which results in an abnormally high body temperature. Severe cases have recorded body temperatures in excess of 104ºF. Hot, dry skin is a typical sign of hyperthermia in which the skin may become red and hot when blood vessels dilate in an attempt to release body heat, sometimes leading to swollen lips. An inability to cool the body through the process of perspiration causes the skin to feel dry. **


 * //What can a person do to prevent Hyperthermia?// As hyperthermia is induced by significant physical exertion on a very hot day, one should avoid physical exertion on a very hot day when the heat indices (the apparent temperature index) are in an unsafe range due to significant heat and humidity combinations. Limiting physical activity when the heat indices are in the unsafe range, maintaining adequate hydration, eliminating caffeine and alcoholic beverages, and avoiding the sun during peak sunshine periods are the best methods for reducing risk of hyperthermia. Try to stay in an air conditioned environment which reduces the effects of heat and humidity. The very young and the elderly are most likely to succumb to heat stroke. Climatology – An Atmospheric Science; pgs 321-323 PB **

94. What is a flood recurrence interval? What is the definition of a 100-yr flood? How do climatologists and hydrologists determine this? Can you have two 100-yr floods within a decade? Explain.

USGS: Water Science for Schools: []

The meaning of 100-yr flood means that a flood of that magnitude has a 1 in 100 chance of occurring in any year.


 * What is a recurrence interval?**

Even though you may never have heard of "recurrence interval", it may be familiar to you. When a major flood occurs, you might have heard that the stream stage reached the "100-year flood level". This means that a flood of that magnitude has a 1 in 100 chance of occuring in any year.

Statistical techniques, through a process called frequency analysis, are used to estimate the probability of the occurrence of a given event. The recurrence interval is based on the probability that the given event will be equalled or exceeded in any given year. For example, there may be a 1 in 50 chance that 6.60 inches of rain will fall in a county in a 24-hour period during any given year. Thus, the rainfall total of 6.60 inches in a consecutive 24-hour period is said to have a 50-year recurrence interval. Likewise, using a frequency analysis (Interagency Advisory Committee on Water Data, 1982) there may be a 1 in 100 chance that a streamflow of 15,000 cubic feet per second (ft3/s) will occur during any year in a particular stream. Thus, the peak flow of 15,000 ft3/s is said to have a 100-year recurrence interval.

Ten or more years of data are required to perform a frequency analysis for the determination of recurrence intervals. More confidence can be placed in the results of a frequency analysis based on, for example, 30 years of record than on an analysis based on 10 years of record.

Recurrence intervals for the annual peak streamflow at a given location change if there are significant changes in the flow patterns at that location, possibly caused by an impoundment or diversion of flow. The effects of development (conversion of land from forested or agricultural uses to commercial, residential, or industrial uses) on peak flows is generally much greater for low-recurrence interval floods than for high-recurrence interval floods, such as 25-, 50-, or 100-year floods. During these larger floods, the soil is saturated and does not have the capacity to absorb additional rainfall. Under these conditions, essentially all of the rain that falls, whether on paved surfaces or on saturated soil, runs off and becomes streamflow.

Modified from Robinson, Hazell, and Young, 1998

No. Several factors can independently influence the cause-and-effect relation between rainfall and streamflow. When rainfall data are collected at a point within a stream basin, it is highly unlikely that this same amount of rainfall occurred uniformly throughout the entire basin, especially during Atlanta's summer thunderstorm season, for example. Some parts of the basin may even remain dry, supplying no additional runoff to the streamflow and lessening the impact of the storm. Consequently, only part of the basin may experience a 100-year rainfall event. Existing conditions prior to the storm can influence the amount of stormwater runoff into the stream system. Dry soil allows greater infiltration of rainfall and reduces the amount of runoff entering the stream. Conversely, soil that is already wet from previous rains has a lower capacity for infiltration, allowing more runoff to enter the stream. Another factor to consider is the relation between the duration of the storm and the size of the stream basin in which the storm occurs. For example, a 100-year storm of 30-minutes duration in a 1-square-mile (mi2) basin will have a more significant effect on streamflow than the same storm in a 50-mi2 basin. Generally, streams with larger drainage areas require storms of longer duration for a significant increase in streamflow to occur. These and other factors determine whether or not a 100-year storm will produce a 100-year flood.
 * Does a 100-year storm always cause a 100-year flood?**

Modified from Robinson, Hazell, and Young, 1998 Yes, although if "100-year floods" started occuring each year, then the more frequent occurences of the floods would change the statistical probability that the floods would occur, and thus, the "100-year floods" could become "50-year floods"! This question points out the importance of proper terminology. The term "100-year flood" is used in an attempt to simplify the definition of a flood that statistically has a 1-percent chance of occurring in any given year. Likewise, the term "100-year storm" is used to define a rainfall event that statistically has this same 1-percent chance of occurring. In other words, over the course of 1 million years, these events would be expected to occur 10,000 times. These events, as well as any recurring events, are assumed to be statistically independent of each other. Therefore, each year begins with the same 1-percent chance that a 100-year event will occur.
 * Can two "100-year floods" occur within several years or even within the same year?**
 * Recurrence intervals and probabilities of occurences ||
 * **Recurrence interval, in years** ||  **Probability of occurrence in any given year**  ||  **Percent chance of occurrence in any given year**  ||
 * 100 || 1 in 100 || 1 ||
 * 50 || 1 in 50 || 2 ||
 * 25 || 1 in 25 || 4 ||
 * 10 || 1 in 10 || 10 ||
 * 5 || 1 in 5 || 20 ||
 * 2 || 1 in 2 || 50 ||
 * Information gotten from the following website:** USGS: Water Science for Schools: []

(Climatology 3rd Quarter Homework Week 7.)
 * AB**

95. Name and briefly describe the Milankovitch cycles. Be able to explain how each of these affects climate over Geologic Time.
 * Milankovitch Cycles **


 * 1) ** Variations in the shape of Earth’s orbit around the sun **


 * The shape of Earth’s orbit changes during a cycle that takes between 90,000 and 100,000 years. It changes from a longer ellipse to a more circular shape. When the orbit is the most elliptical, the amount of radiation received at perihelion (when Earth is closest to sun) would be anywhere from 20 – 30% greater than at aphelion (when the Earth is farthest from the sun). **


 * Right now our orbit is more circular and there is a difference of only 3% between aphelion (July 4) and perihelion (Jan 3). This difference means about 6% more solar energy in January than in July. When Earth is in a more elliptical orbit the 3-5 times increase in solar energy will make for a substantially different climate. **


 * 1) ** Changes in the angle that Earths axis makes with the plane of Earth’s orbit **


 * During a cycle that lasts about 41,000 years the tilt of the Earth’s axis varies between 22 – 24.5 degrees. With a smaller angle of tilt, the smaller the temperature difference between winter and summer. Likewise, the greater the tilt the greater the temperature difference between winter and summer. **


 * 1) ** Precession of the Equinox - the wobbling of Earth’s axis, like a spinning top that is winding down **


 * The period of precession is 26,000 years. Through each 26,000 year cycle the direction in the sky to which the axis points goes around a big circle. So in around 13,000 years the seasons will be opposite. Winter will start around June 21 and with aphelion being around July 4 we will be farther from the sun and tilting away from the sun in the Northern Hemisphere so winters will be colder. The flip side of this is that on January 3 when it is perihelion we will be closer to the sun and it will be summer so our summers will be hotter. **

96. Explain the term ‘proxy data’. Be able to give 2 examples of proxies. Be able to describe each of these in detail.
 * page 409 The Atmosphere 10th Edition **
 * GD **
 * Looks good! KMS **
 * Proxy data is data obtained through indirect observation. Examplesinclude: **
 * ice cores: determination of past temperatures based on oxygen isotope content, atmospheric carbon dixoide levels as well based on trapped air **
 * tree rings: study of drought periods, wet/dry cycles based on thickness of tree rings **
 * varves: deposition of sediments in lakes based on wet/dry seasonal cycles **
 * JA **

97. What is La Nina? What are the oceanic and atmospheric changes we observe during an La Nina event (compared to 'normal' conditions)?

La Nina is a strengthening of the normal circulation over the southern Pacific Ocean.

Sudden cooling of the equatorial water is called La Nina, Spanish for “the girl.” La Nina exaggerates the normal conditions. During La Nina, the trade winds are stronger, the water off western South America is colder, and water in the western Pacific near the equator is warmer than normal. In the western Pacific, surface pressures are lower, and heavy rainfall occurs.

The strengthening of the Walker circulation causes the coastal deserts of Peru and Chile to become even drier – although that might not seem possible. On the western edge of the circulation, Southeast Asia gets even more summer precipitation than usual, causing massive floods in places such as Bangladesh.

Normally, the trade winds and strong equatorial currents flow toward the west. At the same time, the strong Peruvian current causes upwelling of cold water along the west coast of South America. During average years, high pressure over the eastern Pacific causes surface winds and warm equatorial waters to flow westward. The result is a pileup of warm water in the western Pacific, which promotes the lowering of pressure. **(//The Atmosphere// page 211 – 212)** The last passage was taken from //The Atmosphere.//


 * (Hidore, Oliver, Snow and Snow)**


 * AB **