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1、Heat & Temperature Exchange Process,Isotherms and temperature gradients Processes that control temperatures,Learning objectives,Compare & contrast temperature and heat Given observed temperatures, analyze the temperature field using isotherms. Identify strong and weak temperature gradients using the
2、 temperature analysis. Describe the mechanisms that control temperature in the Earth-atmosphere system. Using temperature records from selected global sites, identify which temperature control mechanism (s) account for the observations. Describe the factors that control temperatures that are observe
3、d in Grand County,Temperature,Temperature one of the basic elements used for weather therm=temp) at 2, 5, or 10 deg intervals temperature analysis important for forecasting visually able to see patterns associated with fronts (surface and upper air) severe thunderstorms features tropical cyclone pat
4、ters can calculate temperature gradients T/ d (deg C/km),Analyzing temperature fields,Rules for drawing isotherms on weather charts Draw isotherms at 2, 5, or 10 deg intervals Label each isotherm Interpolate temperature values between observation points and draw isotherms accordingly Isotherms never
5、 cross each other Make isotherms smooth curved lines rather than a series of straight lines. Isothermal analyses are made for surface charts upper air charts,Temperature gradients,Temperature gradient = T/ distance (deg C/km) Strength of gradient can be determined from isothermal analysis Strong tem
6、perature gradient are found in areas where isotherms are close together Weak temperature gradient are found where isotherms are spaced far apart.,Temperature controls,What controls the temperatures we observe? Based on incoming solar radiation and the seasons, an even distribution of temperatures wo
7、uld be observed from the tropics to the polar regions We dont observe this pattern, why? Several factors contribute Can we observe differences in Grand County? Factors that control the temperature on Earth land-ocean heating ocean currents altitude geographical position cloud cover,Land-Ocean differ
8、ences,Land changes temperature faster compared to water Land heats more rapidly & to high temperatures Land cools more rapidly & to cooler temperatures Several physical properties & processes convective currents distribute heat in water bodies solar radiation reaches deeper into water than soils spe
9、cific heat of water greater than soil,Latitude changes of temperature,If we consider latitude alone, over the USA, temperature decreases about 1 deg C per degree of latitude. Example: Compare the mean average temperature for Kansas City and Winnipeg Average temperature for Winnipeg = 2 deg C Average
10、 temperature for Kansas City + 13.3 deg C Therefore, if we consider just latitude over a continent, we should expect about 1 deg/deg of lat,Water-Land Differences,Compare the mean annual temperatures between Vancouver, British Columbia and Winnipeg, Manitoba (see Fig. 3-4, p. 54 of Chap 3-text suppl
11、ement). Because of the differences in the ways land and water heat and cool Vancouver has a more moderate annual temperature change Vancouver has a lower maximum temperature in the summer Winnipegs mean Jan temperature is 20 deg C cooler than Vancouver Winnipegs July temperature is about 3 deg warme
12、r than Vancouver,Global Ocean Currents,There are several ocean currents around the world There are warm and cold currents (see Fig. 3.7 of the text supplement) Type of current affects the mean temps of locations near currents. warm currents moderate the temperatures North Atlantic Drift influences t
13、emperatures in Europe Compare New York with London Compare Northern Hemisphere with Southern Hemisphere (see Fig. 3.1 in text supplement),Ocean Currents,Ocean currents affect observed temperatures. Compare London & St.Johns Newfoundland (difference of 5 deg lat) Compare NY City & Berlin (12 deg lat
14、difference) North Atlantic Drift current causes these differences.,North Atlantic Drift,Ocean currents,Warm Mozambique current,Cold Benguela current,South Africa is another location where ocean currents affect land temperatures. Compare Durban (on east coast) with temperatures at Cape Town,Sea surfa
15、ce temperatures observed by Topex satellite.,Altitude,Commonly observed in mountainous regions Most noticeable when elevations exceed 10s of meters. Environmental lapse rate accounts for most of the temperature differences. 6.5 deg C/1000m Other factors include: reduced density (absorbs/reflects les
16、s radiation) results in greater daily temperature change,Geographic position,Position relative to windward to leeward location on continent makes a difference in observed temperatures. On windward side (west coast of USA or Europe) temperatures are modified due to ocean influence (smaller range of temperatures) In middle of continent, daily, monthly, yearly changes of temperature will be much greater On leeward side, even if located next to ocean, temperature differences will be les
