Understanding Atmospheric Moisture and Heat Index in Hawai'i

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Arizona State University, Tempe *

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112

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Geography

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Apr 3, 2024

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2/16/24, 10:25 PM Hawai'i Physical Geography: Atmospheric Moisture and the Heat Index : GPH 112: Intro to Phys Geography Lab (2024 Spring) https://asu.instructure.com/courses/178332/quizzes/1339467 1/6 Hawai'i Physical Geography: Atmospheric Moisture and the Heat Index Due Feb 16 at 11:59pm Points 4 Questions 2 Time Limit None Instructions Humidity is the general term that refers to the amount of water vapor in the air. There are many ways to measure atmospheric moisture, 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 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 o vapor in the air at saturation at a given temperature. As a ratio, relative humidity is expressed as a perce Relative humidity is dependent on air temperature because the ability of the atmosphere to evaporate m changes as air temperature changes; warmer air can readily evaporate more moisture than cooler air. W comparing locations that contain the same amount of water vapor, the warmer location will have a lowe relative humidity than the cooler location. The first question will have you calculate and identify the differences between dew point and relative hu across the Big Island. The second question in this quiz is to emphasize that the Big Island's amazing diversity of dew points h implications for the temperature that you will feel using what is called a heat index. Down low in the tra

2/16/24, 10:25 PM Hawai'i Physical Geography: Atmospheric Moisture and the Heat Index : GPH 112: Intro to Phys Geography Lab (2024 Spring) https://asu.instructure.com/courses/178332/quizzes/1339467 2/6 winds, the air will seem hotter than the thermometer measures. Up low above the trade wind inversion, dew points make the air feel cooler than the thermometer measures. If you want to look at the chart at higher magnification -- simply drag it to your desk top and zoom in. To it, look at the temperature along the y-axis (this will be given to you) and the dew point on the x-axis (tha get from the geovisualization). Find the value in the middle of the chart tells you the heat index - what it "feel like". EXAMPLE QUESTION: Travel to 19.4201 , -155.2884, where at 10 am on May 15, the temperature was 84˚F. Write down the dew that you see in the geovisualization. Then, travel to 19.7595 , -155.4561 where at 2pm on May 15, the temperature was 84˚F. Write down the dew point that you see in the geovisualization. What’s the heat in these two spots? ANSWER: The dew point for the first location was 55 degrees, which means the heat index is 83 degrees. The dew for the second location is 28 degrees, which means the heat index is 81 degrees.

2/16/24, 10:25 PM Hawai'i Physical Geography: Atmospheric Moisture and the Heat Index : GPH 112: Intro to Phys Geography Lab (2024 Spring) https://asu.instructure.com/courses/178332/quizzes/1339467 3/6 Attempt History Attempt Time Score LATEST Attempt 1 3,269 minutes 4 out of 4 Score for this quiz: 4 out of 4 Submitted Feb 16 at 10:25pm This attempt took 3,269 minutes. 2 / 2 pts Question 1 Answer 1: Answer 2: For the following question, use the relative humidity calculator here. You will be given the temperature at several different locations but will need to find the dew point at those locations in the geovisualization. Complete the sentences with the correct values. Location 1: Fast travel to the shoreline north of Hilo (19.7622, -155.0908). The dew point at this location is [ Select ] F. If the air temperature at this location is 74 F, the relative humidity is [ Select ] %. Location 2: Fast travel to Hapuna Beach (19.9919, -155.8249). The dew point at this location is [ Select ] F. If the air temperature at this location is 78 F, the relative humidity is [ Select ] %. Location 2: Fast travel to Ka'u Forest Reserve (19.3457, -155.4797). The dew point at this location is 50 F. If the air temperature at this location is 55 F, the relative humidity is 83 %. From these values, dew point is better for telling the actual amount of water vapor in the air. o o o o o o 66 orrect! orrect! 76 orrect! orrect!

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2/16/24, 10:25 PM Hawai'i Physical Geography: Atmospheric Moisture and the Heat Index : GPH 112: Intro to Phys Geography Lab (2024 Spring) https://asu.instructure.com/courses/178332/quizzes/1339467 4/6 Answer 3: Answer 4: Answer 5: Answer 6: Answer 7: 66 orrect! orrect! 62 orrect! orrect! 50 orrect! orrect! 83 orrect! orrect! dew point orrect! orrect! 2 / 2 pts Question 2 This question involves you using FAST TRAVEL to jump to two locations. At these spots, you just write down the dew point value you see where the avatar is standing. The air temperature is given to you below in the question. So all you do is to use the chart below. You look at the temperature (that is given) and the dew point (that you get from the geovisualization). The middle of the chart tells you the heat index -- what you would feel. You will see that the dew point can make the air temperature feel warmer or cooler than it really is. If you want to look at the chart at higher magnification -- simply drag it to your desk top and zoom in.

2/16/24, 10:25 PM Hawai'i Physical Geography: Atmospheric Moisture and the Heat Index : GPH 112: Intro to Phys Geography Lab (2024 Spring) https://asu.instructure.com/courses/178332/quizzes/1339467 5/6 What’s the heat index for these two spots? Instructions: Go to 20.0916 -155.8467 (Ocean View Ranch) where at noon am on May 15, the temperature was 99˚ F. Write down the dewpoint that you see in the geovisualization. Then, go to 19.8703 -155.4698 ( Parker Ranch) where at 3pm on May 15, the temperature was 99˚ F. Write down the dewpoint that you see in the geovisualization. The Heat Index North of Ocean View Ranch was 95, and even though the temperature was the same, the Parker Ranch at the indicated coordinates had a heat index of only 88. The Heat Index at Ocean View Ranch was 102, and even though the temperature was the same, the Parker Ranch at the indicated coordinates had a heat index of only 92. orrect! orrect! The Heat Index at Ocean View Ranch was 96, and even though the temperature was the same, the Parker Ranchat the indicated coordinates had a heat index of only 90.

2/16/24, 10:25 PM Hawai'i Physical Geography: Atmospheric Moisture and the Heat Index : GPH 112: Intro to Phys Geography Lab (2024 Spring) https://asu.instructure.com/courses/178332/quizzes/1339467 6/6 The idea of a heat index has become commonplace in TV weather reporting only in the last few decades, but it is a very old idea. Weather observers commented on the impact of more water vapor on how hot it feels millennia ago. The idea of calculating an index is attributed to Osborn Fort Hevener (a new Jersy weaher buff) in the early 1900s. The current way of calculating a heat index was published in the Bulletin of the American Meteorological society in the late 1970s. Then, Robert Steadman’s research turned it into an operational metric by the National Weather Service. Quiz Score: 4 out of 4

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