Research Earth Science Agenda
February 9, Thursday: A Day
nd
 2 block: NEW SEATING CHART – Find your seat (Promethean)
 Take out your agendas from Feb 3 & 7
o Any more weather station model practice activities? pass it forward
WARM-UPS:
Quick review of Rel Humidity and Dew Point temperature
http://www.regentsearth.com/Illustrated%20ESRT/Page%2012%20(DP%20&%20RH)/ESRT%20page%
2012%20index.htm
1. Differentiate between Relative AND Specific Humidity
a. Discuss conditions that result in HIGH relative humidity and LOW relative humidity
i. Explain WHY air holding 10 grams of water vapor at 80 degrees F has a LOWER
relative humidity than air holding 10 grams of water vapor at 50 degrees F.
2. Describe the significance of the dew point temperature
a. Why do meteorologists use dew point as a more accurate measure to predict
precipitation?
3. DESCRIBE how to use a sling psychrometer – BE SPECIFIC! Your description should enable a
student to accurately measure relative humidity and understand the purpose of EACH
thermometer.
OBJECTIVES: METEOROLOGY: Water in the atmosphere
1. Check the following:
https://www.youtube.com/watch?v=OiejHVHrdOo
https://www.youtube.com/watch?v=xNNSugTdpqo
https://www.youtube.com/watch?v=_GQXi92_T1U
2. LAB: Measuring Relative Humidity and Dew Point
a. CAREFULLY FOLLOW ALL INSTRUCTIONS AND BE SURE TO ACCURATELY RECORD ALL
TEMPERATURES!
b. AFTER YOU COLLECT ALL DATA, take out your Relative Humidity and Dew Point
temperature HW – we will go over these
HOMEWORK:
1. Review all notes on water in the atmosphere
a. BE SURE YOU ALSO KNOW THE FOLLOWING:
 The N. Hemisphere has more land than water
 The S. Hemisphere has more water than land
o How does this affect Global Temperatures?
 Air moves from HIGH to LOW pressure – creates breezes and winds
o Effect of Earth’s rotation?
o Coriolis Effect
 Global Winds form from global pressure belts (air moves from high to low pressure)
 Temperature and humidity (moisture) determine air density and air pressure
i. Elevation/altitude also affects air pressure
2. Complete the Relative Humidity and Dew Point Temperature Lab
3. BEGIN THE WATER IN THE ATMOSPHERE TEST REVIEW
4. QUIZ CORRECTIONS – SAME FORMAT – WRITE OUT THE COMPLETE QUESTION AND CORRECT
ANSWER for all missed responses. INCLUDE diagrams
Relative Humidity and Dew Point Temp Practice
Name:_______________________
BLOCK:_________
Dew Point Temp Worksheet Complete the chart below using the Rel. Humidity and Dew Point Temp.
Tables. Note the Wet Bulb Depression is the difference between the wet-bulb and dry-bulb thermometers
.
Air Temp
Wet Bulb Temp
Diff. betw. wet and
Dew Point Temperature
dry bulb
(C)
(C)
(C)
(C)
1
18
13
2
28
26
3
14
8
4
8
4
5
0
-3
6
-11
-12
7
15
10
8
14
10
Relative Humidity Worksheet
Complete the chart below using the Tables on page 704 of your Earth Science Reference Tables.
Air Temp
Wet Bulb Temp
Wet Bulb
Relative Humidity
Depression
(%)
(C)
(C)
(C)
1
24
16
2
28
18
3
20
17
4
4
-1
5
19
16
6
15
10
7
23
21
8
0
-3
For questions #1-10, refer to the graph below, which shows the hourly surface temperature, dew point,
and relative humidity for a twenty-four hour period during the month of May.
100
90
80
Relative Humidity (%)
70
Air Temp. (F)
60
50
Dew Point Temp. (F)
40
30
12:00
8:00
4:00
12:00
8:00
4:00
12:00
20
1. The lowest air temperature occurred at what time?
2.
3.
4.
5.
6.
7.
8.
9.
10.
The highest relative humidity reading occurred at what time?
The highest air temperature occurred at about what time?
The lowest relative humidity occurred at about what time?
According to the graph, what happens to the relative humidity as the air temperature increases?
At what time(s) did the air temperature equal the dew point?
What was the relative humidity (%) when the air temperature equaled the dew point?
Condensation (water coming out of the air) is most likely to occur at approximately what time?
At approximately what time was the rate of evaporation highest?
The greatest change in air temperature occurred during the period from:
A) midnight to 6AM
C) noon to 6PM
B) 6AM to noon
D) 6PM to midnight
1. __________
2. __________
3. __________
4. __________
5. __________
6. __________
7. __________
8. __________
9. __________
10. __________
Use the following tables for your calculations. You may also
use pg. 704 in your text book
Sling Psychrometer Lab Activity
Two instruments used to measure humidity are the Sling Psychrometer and Hair
Hygrometer. The Sling Psychrometer works on the principle that evaporation is a cooling
process (evaporation causes cooling). The sling Psychrometer has 2 thermometers – a wet bulb
and a dry bulb thermometer. The wet-bulb has a wet wick around the end. The dry-bulb is a
regular thermometer. You gently rotate (sling) the psychrometer in the air. The dry-bulb
thermometer is measuring the air temperature. The wet-bulb is measuring evaporation. As
water evaporates from the wick, the temperature of the thermometer decreases (evaporation
causes cooling). The drier the air (less moisture), the greater the decrease in temperature and
the greater the difference between the wet and dry bulb temperatures. For moist air, less
evaporation occurs and there is little change in the wet-bulb temperature and less of a
difference between wet and dry bulb temperatures. IF there is NO difference between the 2
temperatures, the air is saturated (air is holding all the moisture it is capable of holding at that
temperature). Therefore, there is no evaporation taking place.
The Hair Hygrometer works on the principle that hair expands when wet and shrinks
when dry. The needle goes up with higher humidity (more water vapor in the air) and goes
down with lower humidity (drier air).
Sling Psychrometer LAB Activity
1. Write a Purpose and Hypothesis for this lab.
2. WRITE a BRIEF BACKGROUND (explaining all the concepts used in the lab)
3. You will be CALCULATING the relative humidity AND dew point temperature from your
data
4. YOU MUST show all calculations!!
Procedures:
1. Lightly wet the wick on the thermometer of your sling psychrometer.
2. Using your data table, record the initial temperatures of BOTH thermometers starting
with the wet-bulb temperature.
3. Gently sling your psychrometer for approx. ONE minute.
a. Check the wet bulb temperature FIRST, followed by the dry-bulb temperature. If
the temperature has changed, be sure to make a note of this.
4. Continue slinging your psychrometer and checking the temperatures (approx. 30 sec
intervals) UNTIL the wet-bulb temperature stops decreasing.
a. NOTE: If the wet-bulb temperature begins to INCREAS (rise), you went “too far”.
All the water had evaporated so the thermometer is simply recording the air
temperature.
5. SUBTRACT the final wet and dry bulb temperatures.
6. Use the Relative Humidity Chart (dry bulb temperature and the difference between the
wet and dry-bulb temperatures) and record the relative humidity as a %.
NAME:
DATE:
Class Period:
INSTRUCTION SHEET & FORMAL LAB REPORT:
Finding Dew Point & Relative Humidity
INSTRUCTIONS:
1. You will be using a sling psychrometer
2. It is not necessary that the temperatures on both thermometers of the
psychrometer be identical. BUT, this may introduce a small error in your findings.
3. Procedures for using the Sling Psychrometer:
 Be sure the wet bulb thermometer is WET
 Record the initial temperatures in your “Field Data Tables”
 Gently twirl the psychrometer for approx. 1 minute
 Record BOTH temperatures BEGINNING with the WET-BULB
 Gently twirl the psychrometer for an additional 30 – 45 secs (approx.)
 Record the temperatures (always record WET-BULB 1st)
 Twirl the psychrometer for approx. 20 seconds
 Record both temperatures
 Twirl for approx. 10 seconds
 Record
 Continue twirling for 10 second intervals until the wet-bulb temperature
stops falling:
 IF the wet-bulb temperature increases, you twirled the
instrument for too long a time.
 Use the last wet-bulb temperature. that showed a decrease
4. Record these on your data sheet found in the lab.
5. Determine the Dew Point Temperature & Relative Humidity using the reference
tables on pg.704 of your text book or the tables on your agenda
6. Record on your lab data sheet. SHOW calculations or make note of how you found
the final relative humidity and dew point temperature
ANALYSIS:
1. Why SHOULD you run the experiment SEVERAL TIMES and average the results?
2. Why was the wet-bulb temperature always less than the dry bulb temperature?
a. Could the wet- & dry- bulb temperatures be the same? EXPLAIN:
b. Could the wet-bulb be higher than the dry-bulb temperature? EXPLAIN:
3. Explain the relationship between difference in the wet- & dry-bulb temperatures and % of
moisture in the air
4. What units are used for dew point temperature? For Relative Humidity?
5. The sling psychrometer works on the principle that …
6. Explain WHY warm air can hold more water vapor than cooler air.
Field DATA TABLES
Initial
Temperature
1st
Check
2nd
Check
3rd
Check
Final
Temperature
Wet-Bulb
Temperature
Dry-Bulb
Temperature
Difference
(dry – wet)
Relative Humidity
Dew Point Temperature
CALCULATIONS/EXPLANATION of final dew point temperature and relative humidity
STUDY GUIDE FOR METEOROLOGY CUMULATIVE TEST
Meteorology Vocabulary:
Anemometer
Sling psychrometer/Hair hygrometer
Weather vane
Barometer
Thermometer
Isobars (steep and gentle pressure gradients)
High and low pressure areas on a map
Isotherms
Relative Humidity
Specific humidity
Dew point
Greenhouse Effect
Fossil fuels and effect on Earth’s atmosphere
Insolation and effect of angle of sun on Earth’s surface
Heating of Land vs. Water
Land & Sea Breeze Diagram
Graph interpretations – heating of land vs. water
Air Pressure & Winds
Movement from high to low pressure
High and Low pressure areas
Direction of Winds
Weak vs. gentle pressure-gradients
Sinking vs. rising air – temperature & density dependent and effect on air pressure
Areas on Earth where pressure is always low (why) and high (why)
Earth’s rotation and effect on winds – GLOBAL WINDS AND PRESSURE BELTS (know the
diagram)!
Coriolis effect
Direction of deflection (turning) in Northern and Southern hemispheres
Relative Humidity & Dew point temperatures
How to calculate AND INTERPRET
Air Masses, Clouds, and Fronts
Definition of air mass
Types of air masses – locations
Associated temperature and humidity
Types of Fronts
Symbols
Direction of movement
Associated weather and clouds (STORMS)
Hurricanes and Tornadoes
Conditions for formation
Location of formation