Humidity Lab
Humidity is the general term that refers to the amount of water vapor in the air.
There are many ways to measure humidity, including relative humidity and dew point temperature. The dew point temperature is the temperature to which a given parcel of air must cool for condensation to begin, and is the temperature at which the air becomes saturated. Saturation occurs when the rates of evaporation and condensation are equal, at a given air temperature. The concept of saturation can be demonstrated by the use of circles that represent the atmosphere. If the 70 degree Fahrenheit circle (in figure below) were cooled, it would reach saturation at 32 degrees Fahrenheit: the dew point temperature of the circle is 32 degrees F. The dew point temperature is a way of quantifying the actual amount of water vapor in the atmosphere. Air with higher dew point temperatures contains more water vapor than air with lower dew point temperatures. The dew point temperature will always be less than or equal to the air temperature, and tends to change very little on a diurnal basis.
Relative humidity refers to the ratio of the actual amount of water vapor in the air to the total amount of water vapor in the air at saturation at a given temperature. As a ratio, relative humidity is expressed as a percentage. Relative humidity is dependent on air temperature because the ability of the atmosphere to evaporate moisture changes as air temperature changes; warmer air can readily evaporate more moisture than cooler air. When comparing locations that contain the same amount of water vapor, the warmer location will have a lower relative humidity than the cooler location (figure below).
The capacity of the atmosphere to hold water vapor changes with air temperature.
Print and complete the graphs (Figures 1, 2, and 3) using the Sky Harbor International Airport data in Table 2. Plot air temperature in Figure 1. Plot dew point temperatures in Figure 2. Plot relative humidity in Figure 3. The data already plotted on each graph represent measurements made at Encanto Park
Golf Course during the same observation period.
Table 2: Sky Harbor International Airport observations for March 19, 1999.
Figure 1: Air temperature on March 19, 1999.
Figure 2: Dew Point Temperature on March 19, 1999.
Figure 3: Relative Humidity on March 19, 1999.
Answer the following questions using your graphs.
1. Which location (the airport or golf course) reaches a higher maximum air temperature?
2. What accounts for the different cooling rates during the night between the two sites?
3. Which location has the highest relative humidity during the observation period?
4. Based on your answer for question 3, why is this location’s relative humidity so much higher than the other location’s relative humidity (at the same time)?
Question too long: Please see the attached document.
Relative humidity is measured with various instruments.docxDownload Relative humidity is measured with various instruments.docx
Relative humidity is measured with various instruments. One instrument used to measure relative humidity is a sling psychrometer . This instrument has two thermometers mounted side-by-side on a metal holder. One is called the dry-bulb thermometer— it simply records the ambient (surrounding) air temperature. The other thermometer is called the wet-bulb thermometer— it is set lower in the holder and has a cloth wick over the bulb that is moistened with distilled water. The psychrometer is then spun by its handle. In a weather-shelter installation the wet-bulb thermometer can have a long cloth wick that extends to a bowl of distilled water. Instead of spinning the psychrometer a small fan is used to move air across the dampened wick. The rate at which water evaporates from the wick depends on the relative saturation of the surrounding air. If the air is dry, water evaporates quickly, absorbing the latent heat of evaporation from the wet-bulb thermometer, causing the temperature to drop, in other words the wet-bulb thermometer shows a depression in temperature. In an area of high humidity, less water evaporates from the wick. After spinning or ventilating the psychrometer for a minute or two, the temperature on each bulb is noted and compared on a relative humidity psychrometric chart (Table 3), to determine relative humidity.
Table 3 presents a psychrometric table that expresses dry- and wet-bulb temperature relationships in terms of relative humidity— the percent of water vapor actually in the air as compared to the maximum capacity that the air could hold at a given temperature. Table 4 presents a psychrometric table that expresses dry- and wet-bulb temperature relationships in terms of dew-point temperatures— that temperature at which the actual vapor pressure and the saturation vapor pressure are equal.
When using a psychrometric table, you use the wet- and dry-bulb thermometer readings as follows:
T = Temperature of the dry bulb (air temperature)
Tw = Temperature of the wet bulb
Therefore, T – Tw = Wet-bulb depression
Table 3: Psychrometric chart of relative humidity (in percent)
Table 4: Psychrometric chart of dew-point temperature (in degree Celsius)
Using the psychrometric charts in Table 3 and 4 determine the relationships asked for in Table 5 and put the answers next to the corresponding letter below:
(T)
Dry-bulb temperature (°C)
(Tw)
Wet-bulb temperature (°C)
(T-Tw) Wet-bulb depression (°C)
(RH)
Relative humidity (%)
(Tdp) Dew-point temperature (°C)
-10°
-12°
2°
39%
-21°
5°
1°
a.
b.
c.
17.5°
d.
e.
86%
f.
25°
10°
g.
h.
i.
30°
j.
k.
l.
23°
37.5°
33°
m.
n.
32°
a.__________ Celsius
b.__________ %
c.__________ Celsius
d.__________ Celsius
e.__________ Celsius
f.__________ Celsius
g.__________ Celsius
h.__________ %
i.___________ Celsius
j.__________ Celsius
k.__________ Celsius
l.__________ %
m.__________ Celsius
n.__________ % *Adapted from Introductory Physical Geography Laboratory Manual produced by Arizona State University and Encounter Geosystems by Thomsen and Christopherson.
Part 2
Weather Maps Lab
Introduction
The National Weather Service manages hundreds of weather stations across the country that observes meteorological variables like air temperature, dew point temperature, and wind direction. These observations are plotted as station models on surface weather maps. Meteorologists use these maps to analyze and forecast the weather by identifying areas of high and low atmospheric pressure, weather fronts, and significant weather events.
Station Models
Station models provide a means of presenting a lot of information in a fairly concise manner. The most common meteorological variables plotted on a station model are atmospheric pressure, air temperature, dew point temperature, wind speed and direction, cloud cover, and present weather. Many other variables can be entered, such as cloud types and cloud heights. On a weather map, station models are centered on the latitude and longitude of the city where the observations were recorded.
The key to understanding a station model is in understanding the shorthand used to draw the model. According to the charts, in the station model example (figure below), the temperature is 76 degree Fahrenheit, the dew point temperature is 55 degree Fahrenheit, and the wind direction is northeast (the wind flag points in the direction the wind is coming from) at about 20 knots. The atmospheric pressure is 1013.8 mb, and has increased and then decreased, and is now lower by 0.3 mb than three hours ago. The cloud cover is completely overcast, and it is raining.
*Cloud cover is typically given in eighths (labels for above would be clear, 1/8 through 8/8, and obscured).
Atmospheric pressure readings are coded to save space. The leading 10 or 9 is dropped from the observation, and the last 3 digits (which implies a decimal place) are used on the station model. The units are millibars (mb).
Atmospheric Pressure Decoding Guidelines:
If the first digit on the model is ≤5, then add a 10
Example: 075 would be decoded as 1007.5 mb
If the first digit on the model is >5, then add a 9
Example: 613 would be decoded as 961.3 mb
Pressure change over the past 3 hours is given on the station model on the right side next to the pressure tendency number. The following chart decodes the line segments:
Decode the following station models:
1. What is the temperature at location D? ___________ Fahrenheit
2. What is the dew point temperature at location H? ____________ Fahrenheit
3. What is the decoded atmospheric pressure for location A? _________ mb
4. What is the decoded atmospheric pressure for location B? _________ mb
5. What is the cloud cover (in eighths) for location F? _________
6. What type of weather (precipitation) is occurring at E? ________________
7. How has the pressure changed over the last three hours at C? _____________
8. How has the pressure changed over the last three hours at B? _____________
9. What is the wind direction (where the wind is coming from) for location D? ____________
10. What is the wind direction (where the wind is coming from) for location H? ____________
Weather Fronts
A weather front is simply a boundary between different air masses where usually the most obvious difference between the meeting air masses is temperature. Four classes of fronts exist depending upon the movement of the air mass. The front symbols (shown below) show the direction that the front is advancing. In the United States, cP and mT air masses are the most influential air masses on weather and climate. Cold fronts are the boundaries between cP and mT air masses, where the cP air mass is advancing. Warm fronts are the boundaries between mT and cP air masses, where the mT air mass is advancing. An occluded front occurs when the cold front (cP air mass) catches up to the warm front (mT air mass), and forces the mT air mass off the ground. A stationary front is a boundary between a cP and mT air mass, where neither air mass is advancing.
Frontal boundaries consist of leaning air and are lifting mechanisms in the atmosphere (figure below). Cold fronts tend to trigger abrupt lifting in the atmosphere, causing clouds and intense, brief periods of precipitation along the front line. Warm fronts overrun the cooler air mass along a gentler slope, with cloudiness and showery, light precipitation well ahead of the front line.
The vertical profile between the two different air masses demonstrates the lifting in the atmosphere from frontal boundaries.
Remember that station models describe several elements of surface weather and climate. In the following exercises, the station models indicate surface temperatures, wind direction and wind speed. Typically, the air mass with higher wind speeds and winds moving perpendicular to a front are advancing.
Analyze the weather station image above for frontal boundaries. Between which locations would there be a cold front?
Between locations C and H Between locations B and C Between locations A and D Between locations G and I
Question 121 pts
Analyze the weather station image above for frontal boundaries. Which location is within the mT air mass?
Question 131 pts
Analyze the weather station image above for frontal boundaries. What is the wind direction in the warm air mass?
Question 141 pts
Analyze the weather station image above for frontal boundaries. In what direction is the cold front advancing?
Category: Geographic Information
Solve questions related to weather forecasting in the document provided.
Describe weather forecast models that utilize diverse data sources. Analyze MOS, and interpret UTC. All questions are in the document.
Hillsborough County School Board would like to establish a new traffic safety initiative to improve teen
driver safety in the county. You are assigned to analyze teen traffic crash data (2015‐2019) and present your findings with maps. Your presentation (ppt) should include as a minimum the following components:
Explain your data and process to develop maps.
Map(s) to show the frequency of teen crashes by high school boundaries (district) in Hillsborough County
Map(s) to show the annual change in teen crashes at the school district level between 2015 and 2019 in Hillsborough County
Map(s) to show the proportion of the low-income population (census tract level) by high school boundaries and discuss the relationship between income and the frequency of teen crashes
Select one school and develop maps to show teen crashes around the school (Draw a boundary of the selected school and buffer). Investigate crash frequencies based on the distance from the school. Distance as measured by a straight line. (Less than a quarter of a mile, half a mile, a mile…)
Discuss your findings
Final submission will be a ppt (No more than 20 slides including title page)
Add speaker notes to each slide (what you’re going to say to present)