1. Thanks to Martha Remos

2. QUIZ RESULTS – Overal Scores

3. QUIZ RESULTS – Individual Questions

4. ESCI 106 – Weather and Climate Lecture 3
Jennifer D. Small 

5. Weather Fact of the Day: September 1
2008: A flash flood engulfed 4 hikers as they were trekking along the banks of River Prieto-River Blanco NW of Naguabo, PR.
Two escaped the flood surge, but two were swept away to their deaths
~1.5 in of rain had fallen on parts of the El Yunque National Forest.

6. National Watches and Warnings

7. Temperature (from Chapter 2)
Temperature is a quantity that describes how warm or cold an object is.
It can also be described as:
a measure of the average kinetic energy of the atoms or molecules in a substance

8. Temperature (from Chapter 2)
Temperature video from online..

9. Air Temperature –why it’s important
It’s the first thing we usually think about when we talk about “weather”
Temperatures vary on different time scales
Seasonally, daily and even hourly
Temperatures vary all over the globe, by quite a bit.

10. Isotherms
We use Isotherms the distribution of temperature over a large area.
They are lines that connect points on a map that have the same temperature

11. Isotherms – Why do we care??
Isotherms make it easier to read and analyze weather maps
By looking at patterns of temperature (and pressure) you can determine weather conditions in the next few days.

12. Isotherm a Simplified Example

13. Let’s do an example together!

14. Air Temperature Example Daily mean temperature Maximum Temperature: 96
Average of 24 hourly readings
Adding maximum and minimum and dividing by two.
Example
Maximum Temperature: 96
Minimum Temperature: 42
Daily Mean Temperature: ( )/2 = 69

15. Air Temperature Daily Temperature Range Example
The difference between the maximum and minimum daily temperatures
Example
Maximum Temperature: 96
Minimum Temperature: 42
Daily Temperature Range: ( ) = 54

16. Air Temperature Monthly mean temperature Example
February Daily
Mean Temperatures
Feb 1: 32
Feb 15: 40
Feb 2: 31
Feb 16: 42
Feb 3: 33
Feb 17: 45
Feb 4: 32
Feb 18: 47
Feb 5: 35
Feb 19: 47
Feb 6: 37
Feb 20: 52
Feb 7: 39
Feb 21: 51
Feb 8: 42
Feb 22: 53
Feb 9: 40
Feb 23: 55
Feb 10: 39
Feb 24: 58
Feb 11: 37
Feb 25: 54
Feb 12: 40
Feb 26: 53
Feb 13: 41
Feb 27: 52
Feb 14: 39
Feb 28: 50
Air Temperature
Monthly mean temperature
Adding together the daily means for each day of a month and then dividing by the number of days in that month
Example
Sum of Daily Means: 1216
Number of Days: 28
Monthly Temperature Mean: (1216/28) = 43.4

17. Air Temperature Annual Mean Temperature Example
Adding together the monthly means and dividing by 12
Example
Annual Means
January: 49
February: 47
March: 52
April: 60
May: 69
June: 75
July: 80
August:: 83
September: 76
October: 65
November: 58
December 52
Sum of Monthly Means: 766
Number of Months: 12
Annual Mean Temperature: (776/12) = 63.8

18. Air Temperature Annual Temperature Range Example
The difference between the warmest and coldest monthly mean temperatures
Example
Warmest Monthly Mean Temperature: 95
Coldest Monthly Mean Temperature: 25
Annual Temperature Range: ( ) = 70

19. What controls air temperature?
Differential Heating of land and water
Ocean Currents
Altitude
Geographic Position
Cloud cover and albedo

20. Land and Ocean – Differential Heating
Different surfaces absorb, emit and reflect different amounts of energy.
This causes variations in air above each surface

21. Land and Ocean – Differential Heating
In general: Land HEATS more rapidly and to HIGHER temperatures than Water.
In general: Land COOLS more rapidly and to LOWER temperatures than Water.

22. Land and Ocean – Differential Heating
Variations over Land are GREATER than variations over the Ocean!!!
The land surface has more variety….
Trees
Streets
Buildings
Fields
Houses….

23. Ocean – Why is it more variable?
Surface temperature of water rises and falls slower than land
Water is highly mobile and mixes easily (think mixing red and blue dye… turns purple)
Daily changes are about 6 meters deep
Yearly ocean and deep lakes experience variations through a layer between m thick!

24. Land – Why is this the case?
Heat does not penetrate deeply into soil or rock; it remains near the surface.
Rocks are not fluid… so no mixing
Daily temperature changes are seen only 10 cm down
Yearly temperature changes reach only 15 meters or less

25. Land and Ocean – Summer vs. Winter
During summer a thick layer of water is heated while only a thin layer of land is heated.
During winter the shallow layer of rock cools rapidly while the deeply heated water takes a longer time to cool.
as surface water cools it becomes heavier and sinks, replaced with warmer less dense water from below….
This means the surface temperture of water doesn’t appear to change much

26. Land and Ocean – opaque vs. transparent
Because land surfaces are opaque heat is absorbed only at the surface
Water is transparent and lets energy from the sun penetrate to a depth of several meters

27. Land and Ocean – Specific Heat
The specific heat (the amount of heat needed to raise the temperature of 1 gram of water by 1 degree Celsius) is greater (~3 times) for ocean than land.
The OCEANS require MORE heat to raise its temperature the same amount as an equal quantity (grams) of land.

28. Land and Ocean – Evaporation
Evaporation is greater from Oceans than from Land
There’s more water molecules 
Energy is required to evaporate water
When energy is used to evaporate water it is not available for heating.
WATER WARMS MORE SLOWLY THAN LAND!!

29. Class Question??
Which Hemisphere (north or south) has larger temperature variations?
Why??
The Northern Hemisphere has greater variations in temperature than the Southern Hemisphere
There is more ocean than in the Southern Hemisphere. There is little land to interrupt the oceanic and atmospheric circulation. Thus, the SH has smaller variations in temperature.

30. Ocean Currents
Ocean currents are caused by wind (interactions between the atmosphere and ocean).
Energy passes from the atmosphere to the ocean via friction.
The DRAG exerted be the wind causes it to move

31. Ocean Currents
The transfer of heat by winds and ocean currents equalizes latitudinal energy imbalances

32. Ocean Currents – Poleward Currents
Have a MODERATING effect !!
Warm water from the tropics travels up the coast via the Gulf Stream
It becomes the North Atlantic Drift and helps keep English and Irish weather mild.
GULF STREAM!

33. Ocean Currents – Cold Currents
Have a COOLING effect !!
Predominately influence the tropics during summer months
Happen in regions of costal upwelling
Associated with cool summers and fog
CALIFORNIA CURRENT

34. Altitude Atmospheric Lapse Rate: 6.5 C per km
Cooler temperatures at greater heights

35. Altitude
However, additional heating of the LAND (e.g. Mountain) causes the temperature to be WARMER than predicted by the lapse rate
Absorbtion and reradiation of solar energy by the ground surface keep places like Quito, Ecuador warmer than expected

36. Altitude
Again, atmospheric pressure and density decreases too so it absorbs and reflect less solar radiation.

37. Geographic Position
Windward: prevailing winds blow From the Ocean to the SHORE
Leeward: prevailing winds blow TOWARDS the Ocean
WIND DIRECTION
WIND DIRECTION
Lacks Ocean Influence, More like Land Temperatures
MORE VARIABLE TEMPERATURES
Moderated by the Ocean air, cool summers-mild winters
LESS VARIABLE TEMPERATURES

38. Cloud Cover and Albedo Clouds cool during the day Clouds warm at night
High ALBEDO
Lower Maximum
Clouds warm at night
Trap OUTGOING Longwave radiation
Higher Minimum

39. WORLD DISTRIBUTION OF TEMPERATURES
JANUARY
Decrease in Temperature from Equator to Poles
Warm colors to Cool colors
JULY

40. WORLD DISTRIBUTION OF TEMPERATURES
JANUARY
Latitudinal Shifting due to the seasonal migration of the Sun.
“HOT SPOTS”
Differential heating
Heating is largely a function of LATITUDE
JULY

41. WORLD DISTRIBUTION OF TEMPERATURES
The hottest and coldest places are over land.
Warm ocean currents moving to the Poles warm the air.
Equatorial bound currents Help cool the air.

42. WORLD DISTRIBUTION OF TEMPERATURES
-40
Equatorial temperatures do not fluctuate significantly (there are no seasons). 25
-10
Middle and higher latitudes have much stronger seasonal signals. 25

43. CYCLES of AIR TEMPERAUTRE
Daily Temperature Variations
Magnitude of Daily Temp Changes Depends on
Variations in Sun angle (location)
Windward vs. leeward (location)
Clouds or no clouds (weather)
Amount of water vapor (weather)
Annual Temperature Variations
Months with highest and lowest mean T do not correspond to periods of max and min radiation
Shows that solar radiation isn’t the only thing governing surface temperatures,

44. TEMPERATURE MEASUREMENT
Mechanical thermometers
Electronic thermometers
Instrument shelters

45. Mechanical Thermometers
Most substances EXPAND and CONTRACT as a function of temperature…
Most thermometers use this principle.
Liquid-in-gas thermometers
Most common in daily use
Maximum Thermometers
Minimum Thermometers

46. Mechanical Thermometers
Bimetal strip
Consists of two thin strips of metal that are bonded together and have different expansion properties causing it to bend and curl.

47. Mechanical Thermometers
Thermograph
Uses a bimetal strip
Continuously measures temperature as the strip bends and flexes.
Pen records temperature on special paper.
Not as accurate as liquid-in-glass

48. Electric Thermometers
Thermistors are present in electric thermometers
Thermal resistor
As temperature increase so does the resistance, reducing the current
As temperature decreases, the resistance decreases allowing current to increase

49. Instrument Shelters Where you take temperature matters
Instrument Shelters are:
White – for high albedo (reduce solar heating)
Ventilated – so it doesn’t get hot like your car
1 meter high – reduce longwave heating

50. Temperature Scales
Fahrenheit
Celsius
Kelvin

51. Fahrenheit
Fahrenheit is the temperature scale proposed in 1724 by, and named after, the Dutch-German-Polish physicist Daniel Gabriel Fahrenheit
Based on “Fixed Points” – coldest temperature he could measure and assumed human body temp.
That’s why Freezing is at 32 and Boiling is a 212.

52. Celsius
Invented by Swede Anders Celsius 28 years after Fahrenheit (1742)
Decimal Scale
0 degrees = Freezing
100 degrees = Melting

53. Kelvin Also called the “Absolute Scale”
The Kelvin scale is named after the Belfast-born engineer and physicist William Thomson, 1st Baron Kelvin (1824–1907), who wrote of the need for an "absolute thermometric scale".
Same Spacing as Celsius – 100 divisions between boiling and melting
0 K = the temperature at which all molecular motion is presumed to cease

54. Converting between temperature scales
To go from Celsius to Fahrenheit
°F = (1.8 X °C) + 32
To go from Fahrenheit to Celsius
°C = (°F – 32) / 1.8

55. Converting between temperature scales
To go from Kelvin to Celsius
° C = K
To go from Celsius to Kelvin
K = ° C

56. Converting between temperature scales
To go from Kelvin to Fahrenheit
°F = (K ) * 9/5 + 32
To go from Fahrenheit to Kelvin
K = (°F - 32) * 5/

57. APPLICATIONS of TEMP DATA
Heating Degree-Days
When you turn the heat on
Cooling Degree-Days
When you turn the AC on
Growing Degree-Days
When plants can grow
Temperature and Comfort
How temperature ACTUALLY feels

58. HEATING SEASON is defined as July 1st through June 30
Heating Degree-Days
Developed by Engineers in the early 20th century
A way to evaluate energy demand
Don’t need the “heat” if it is 65F or warmer outside
Any degree BELOW 65 counts as a heating degree-day
e.g. if it’s 50F out….
That’s = 15 heating degree-days
Total it up for the whole year or season
HEATING SEASON is defined as July 1st through June 30

59. COOLING SEASON is defined as January 1st through December 31st
Cooling Degree-Days
Developed by Engineers in the early 20th century
A way to evaluate energy demand for cooling a building
If its above 65 you need the AC on….
Any degree ABOVE 65 counts as a Cooling degree-day
e.g. if it’s 85F out….
That’s = 20 cooling degree-days
Total it up for the whole year or season
COOLING SEASON is defined as January 1st through December 31st

60. Growing Degree-Days (GDDs)
Used by farmers to determine the approximate date to harvest their crops.
SUPER HANDY here in CA
Specific for each CROP
The number of GDDs for a crop on any day is the difference between the daily mean temperature and the base temperature of the crop

61. Growing Degree-Days (GDDs)
Example:
Sweet Corn Base Temperature = 50 F
Peas Base Temperature = 40 F
If Mean Daily Temperature = 75 F
Sweet Corn GDDs = = 25
Peas GDDs = = 35
Thus, if 2000 GDDs are needed to mature a crop, you just keep track of when you reach 2000 GDDs and then harvest!

62. Growing Degree-Days (GDDs)

63. Temperature and Comfort
How we perceive temperature matters to us humans. It is affected by:
Relative humidity
Wind
Sunshine
Heat Index
When it’s humid, evaporation doesn’t work as well and we “Feel” hotter
Windchill
Wind makes it “Feel” colder than it actually is

64. Temperature and Comfort