Summary SCI 210 Oceanography

Manhattan College SCI 210: Oceanography Chapter 5: The Atmosphere and Ocean Learning Objectives In this chapter, we examine radiational heating and cooling of the Earth-atmosphere system: 1. the interaction of incoming solar radiation with the atmosphere, ocean, and continents, 2. the flow of infrared radiation to space, and 3. the greenhouse effect. We also discuss heat transport by atmospheric and oceanic circulations 1. Understand atmospheric circulation as it relates to ocean circulation. INTRODUCTION: At middle latitudes, prevailing winds blow from west to east. Sea surface temperatures (SST) change relatively little through the course of a year. This stable SST regime dampens the summer-to-winter temperature contrast of air flowing over the ocean to downwind Western Europe. • In Western Europe, the air temperature contrast between summer and winter is less than it is over most of North America. Driving Question: What role does the ocean play in the long-term average state of the atmosphere? WEATHER AND CLIMATE We can think of weather as the state of the atmosphere at some place and time – described in terms of such variables as temperature, precipitation, cloud cover, and wind speed. Climate is popularly defined as weather at a particular place averaged over a specific interval of time. – By international convention, average values of weather elements such as temperature or precipitation are computed over a 30-year period beginning with the first year of a decade. Heating and Cooling Earth’s Surface 1. As Earth orbits the sun, its atmosphere and surface are absorbing energy radiated by the sun (mostly between 0.25 and 2.5 micrometers). 2. Absorption of solar radiation heats the Earth-atmosphere system. 3. At the same time the entire planet is emitting infrared radiation to space (mostly between 4 and 24 micrometers), which has a cooling effect on the Earth-atmosphere system. 4. Over the long term, radiational cooling of the planet essentially balances radiational heating of the planet so that Earth remains in radiative equilibrium with surrounding space. SOLAR RADIATION 1. Once every 24 hrs, Earth completes one rotation on its axis. 2. At any instant, half the planet is illuminated by solar radiation while the other half is in darkness. 3. The tilt of Earth’s spin axis (23 degrees 27 minutes) is responsible for the seasons. 4. the Northern Hemisphere tilts away from the sun in fall and winter, and toward the sun in spring and summer a. Annual periodic changes in the planet’s orientation to the sun result in changes in a.i. solar altitude (the angle of the sun above the horizon) and . length of daylight (elapsed time between sunrise and sunset) b. Solar altitude varies from 0º (at sunrise or sunset) to as much as 90º (sun directly overhead) c. At middle and high latitudes, the altitude of the noon sun is higher, daylight is longer, and solar radiation is more intense in summer than in winter. d. The intensity of solar radiation striking Earth’s surface per unit area varies with the solar altitude. e. With increasing solar altitude, more solar energy strikes a unit area of Earth’s surface in a unit of time f. Greater solar altitudes in the tropics translate into more intense radiation and higher temperatures at Earth’s surface. Consider this analogy: (A) A flashlight beam shines on a horizontal surface most intensely when the flashlight shines from directly overhead (analogous to a solar altitude of 90 degrees). (B) At an angle decreasing from 90 degrees, the flashlight beam spreads over an increasing area of the horizontal surface so that the light is less concentrated (less radiational energy received per unit area). Proximity to large bodies of water also affects the timing of the average warmest and coldest time of the year. 1. Outside of the tropics, the annual temperature cycles lags the annual solar radiation cycle. 2. In the interior United States, the air temperature cycle lags the solar radiation cycle by an average of 27 days. 3. But in coastal localities having a strong maritime influence (e.g., coastal