Heat Temperature Exchange Process

1. Heat & Temperature Exchange Process Isotherms and temperature gradients Processes that control temperatures

2. Learning objectives Compare & contrast temperature and heat Given observed temperatures, analyze the temperature field using isotherms. Identify strong and weak temperature gradients using the 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 observed in Grand County

3. Temperature Temperature one of the basic elements used for weather & climate varies, sometimes considerably, seasonally, daily, & by the hour An example observed in Grand County? How are temperatures analyzed on weather charts? Use a technique called, isoplething (same+value) Draw isotherms (iso=equal; 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 patters can calculate temperature gradients ?T/ ?d (deg C/km)

4. 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 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

5. Temperature gradients Temperature gradient = ?T/ ? distance (deg C/km) Strength of gradient can be determined from isothermal analysis Strong temperature gradient are found in areas where isotherms are close together Weak temperature gradient are found where isotherms are spaced far apart.

6. Temperature controls What controls the temperatures we observe? Based on incoming solar radiation and the seasons, an even distribution of temperatures would be observed from the tropics to the polar regions We don�t 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

7. Land-Ocean differences 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 specific heat of water greater than soil

8. 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 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

9. 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 supplement). 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 Winnipeg�s mean Jan temperature is 20 deg C cooler than Vancouver Winnipeg�s July temperature is about 3 deg warmer than Vancouver

10. 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 temperatures in Europe Compare New York with London Compare Northern Hemisphere with Southern Hemisphere (see Fig. 3.1 in text supplement)

11. Ocean Currents