gph 111 lab

LightningLabABCDJuly23.pdf

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Lab Title LIGHTNING IN THE PEAKS Analyzing processes responsible for the distribution of lightning strikes during Arizona's monsoon season in the San Francisco Peaks

Lightning strike over San Francisco Peaks Credit: Mike Elson USFS Coconino NF

What is this lab all about?

Lightning fascinates students in a physical geography class. Yet traditional pen-and- paper physical geography labs that deal with thunderstorm development and lighting fail to capture the wonder and many of the mysteries. For all we do understand about lightning, we still need to learn some the most basic aspects such as lightning’s distribution. Thus, this lab about the physical geography of lightning, focusing you analyzing processes that explain its geographic (spatial) distribution.

Lab Worth The points you accumulate for correct answers count towards your grade. Incorrect answers do not hurt your grade.

Computer program used in this lab

You will be given instructions in a canvas module page on how to download virtual world of Northern Arizona Lightning. In this program, you are a virtual character able to wander around the San Francisco Peaks near Flagstaff, Arizona, and observe the landscape (via Landsat satellite image), air temperature, precipitation, and lightning strikes.

SQ general studies criteria

Students analyze geographical data using the scientific method, keeping in mind scientific uncertainty. Students also use mathematics in analyzing physical geography processes and patterns.

Lab Sections

CANVAS MODULE QUIZZES Stage 0: Getting to know the lab & study site Stage A: Lightning and Monsoon Basics Stage B: Exploration Stage C: Investigation and Detailed Analysis Stage D: Synthesis Essay

PAGES Different PDF File 2 8 17 34

STAGE A: BASICS BACKGROUND Part A of this lab provides you with basic background information about lightning, and also the Arizona Monsoon that sets the table for lightning by providing the atmospheric conditions to develop thunderstorms in the Flagstaff, Arizona, area. You can obtain this background information to prepare you for the quiz questions about lightning basics in two different ways. There is an online lecture by Ryan Heintzman that you can watch on youtube: https://www.youtube.com/watch?v=BQ_ZSde8Rlo& THE SAME INFORMATION IN THE YOUTUBE IS PROVIDED BELOW IN WRITTEN FORM. When you are done with reading this material and/or watching the presentation, take the multiple- choice quiz administered by canvas. Thunderstorm Formation Fundamentally, thunderstorms are created by the conflation of two things: rising air and moisture. Both are necessary conditions to create a storm, and “uplift mechanisms” help to get the air rising. These include convectional uplift (rising warm air - think of a hot air balloon), frontal or boundaries (air boundaries overtaking each other or colliding - think a cold front), and orographic (mountain uplift - air being pushed up the mountain). As this lifted air rises, it cools. If the air cools enough, it will reach dew-point and begin to form clouds. This is when the first stage of a thunderstorm begins. The rising air pushes upward, creating billowing, puffy clouds. This is stage 1 of the thunderstorm’s life cycle: the towering cumulus stage. This stage is defined primarily by updrafts. Once the air begins to cool at the top of the atmosphere, it descends, creating a downdraft in which water and ice begin to fall back down to earth. This is called the mature stage, defined by both updrafts and downdrafts being essentially equal. In this stage is when the thunderstorm can produce tornadoes, hail, winds, and flooding, and generally the stage with the most frequent lighting. The final stage of a thunderstorm is the dissipating stage, where the downdraft becomes strong enough to cut off the updraft, leaving behind a cloud top in the upper atmosphere. In this stage, lightning can still occur, although it isn’t as frequent as the mature stage. You can watch these stages in motion in the video here: https://www.youtube.com/watch?v=Z8otb4UdI5U

Charge Separation & Static Discharge Thunderstorms have very turbulent environments. Strong updrafts and downdrafts occur with regularity and within proximity to each other. The updrafts transport small liquid water droplets from the lower regions of the storm to heights between 35,000 and 70,000 feet, miles above the freezing level. The water freezes and then falls back in the thunderstorm downdraft as ice and hail. The particles that ascend have their electrons sheared off by those falling back down. Because electrons carry a negative charge, the result is a storm cloud with a negatively charged based and a positively charged top. This negative base also has the impact of pushing electrons in the normally neutral ground away enough to create a positively charged ground underneath the thunderstorm. This charge separation in the thunderstorm and the ground creates an electric field. You can see this similar action occurring at a much smaller scale if you shuffle your feet across carpet while wearing socks. As you move across the ground, you shear off more and more electrons, causing you to be negatively charged, while the ground or your friend has a relatively more positive charge. When there is enough of an imbalance in charge and you stick your finger out to an object and get close enough, these charges attempt to equalize, creating a static shock which discharges the negative charge from you into the highly conductive metal doorknob. This process is also known as a static discharge, and on a much larger scale, this is seen as lightning in thunderstorms. However, because the atmosphere is a very good insulator, it takes a massive amount of this charge imbalance to create lightning. The lightning stabilizes these massive imbalances between charges within the cloud itself and between the cloud and ground. Lightning Components In negative cloud-to-ground lightning, like the one in the video, the mechanism for moving the negative charge to towards the ground is called a stepped leader. This moves in incredibly fast segments, drawing the negative charge towards the ground by ionizing segmented regions of more positively charged molecules in the air. Once close enough to the ground, a positive charged leader moves from the ground, typically from a structure or feature taller than the surrounding environment, like a tall building or tree (although it’s more complicated than that, and there can be many positive charged leaders). One of the leaders from the ground will then attach to the negative leader and form a channel that the current will flow through. The current, in what’s called a “return stroke” moves up the channel, while the electrons constantly flow down towards the ground. This return stroke is what our eyes perceive as the lightning flash and is the brightest component.

The process is so fast and the return stroke so bright that we can’t perceive the preceding components with our own eyes. The return stroke can also happen multiple times. A feature called a dart leader will act as a secondary stepped leader. A dart leader will travel back down the channel made by the original stepped leader, drawing down negative charge from the cloud and then initiating another return stroke. This is why lightning sometimes appears to flicker. You can watch some slow-motion videos of lightning here: https://www.youtube.com/watch?v=nBYZpsbu9ds https://www.youtube.com/watch?t=538s&v=qQKhIK4pvYo Types of Lightning Typically, lightning that strikes the ground has a negative charge. It comes from the negatively charged particles inside the lower central part of the cloud and strikes the positively charged ground below. However, not all lightning originates from this central region. Some lightning can strike outside of the area which the thunderstorm is moving across, where the ground is negatively charged compared the strong upper positive charge in the top of the thunderstorm, and is called positive lightning. This happens around 5% of the time, but positive lightning is particularly dangerous due to the much stronger electric field needed to pass through the greater distance of air, sometimes many miles from the thunderstorm, as well as an increase duration of time the lightning bolt is in contact with the ground.

So far, we’ve mostly looked at videos and talked about cloud-to-ground lightning strikes. But there are other types of lightning, and some are absolutely bizarre. Around 75% of lightning are intra-cloud strikes, due to the strong electrical charges in the cloud. Other strikes include ground-to-cloud strikes, which start from the ground upward - these usually are initiated by large towers. Some lightning extends out into the air, called cloud-to-air, and lightning can branch between storms in cloud-to-cloud. Transient luminous (TLE) events are rare and not well understood currently but are associated with strong thunderstorms. These include things like red sprites, a jellyfish shaped object miles above the thunderstorm, and are thought to be initiated by strong positive cloud-to-ground lightning strikes. Blue jets look like cones shooting out from the top of thunderstorms. The last type of TLE are elves, which are glowing disks near the top of the atmosphere, well above thunderstorms, and can stretch hundreds of miles across. Take a look at this website to see a few graphics of these lightning types and check out the videos below:

Take a look at some of these interesting lightning events here: https://www.youtube.com/watch?v=15Rdfz1UPJk https://www.youtube.com/watch?v=D7mqs6fng7o Thunder & Lightning Safety Now, recall that lightning can reach temperatures over 50,000 degrees Fahrenheit. That’s five times hotter than the surface of the sun. So when lightning strikes, the air around the bolt heats rapidly and expands. This sudden expansion moves faster than the speed of sound, which creates a sonic boom. A good baseline to determine how far away lightning strikes is by taking the amount of time it takes from the strike to the sound of thunder and divide by five. Every five seconds equates to one mile away. However, sometimes the sound of thunder does not occur. This is commonly misappropriated as “heat lightning”, which is a myth. Lightning always produces thunder, but the viewer may be too far away or the sound gets distorted enough to limit its progression to your ears. On average, around 300 people are struck and killed annually in the US every year. A majority were outside enjoying outdoor activities when they were struck. While most people survive lightning strikes, they can be left with severe burns and nerve damage. Lightning is a particularly deadly aspect of severe weather, more so than other events like tornadoes and hail due to lightning being able to strike away from the thunderstorm. One such lightning strike spanned a distance of over 300 km (around 200 miles). This is the equivalent of lightning beginning from the clouds above the Statue of Liberty near New York and striking the Washington Monument in Washington D.C. Another comparison would be striking over Big Ben in London but hitting the Eiffel Tower in Paris. Although this lightning distance is rare, lightning can easily strike several miles from the location of the thunderstorm, a so called “bolt from the blue”.

So what should you do if you have lightning occurring close by? The smartest idea is to go inside a grounded structure. But what if that’s not an option? How about if you are in a car, or a forest, or in an airplane? A car and a plane work like Faraday cages, meaning that if you don’t touch the metal outside, the electricity will go around and continue on its path toward the Earth. Meanwhile, other objects, like tall trees often don’t fare as well. Take a look at these videos below to see what happens when lightning strikes various objects. Are you safe in your car? https://www.youtube.com/watch?v=ve6XGKZxYxA Are you under a tall tree? https://www.youtube.com/watch?v=2xAhtPlRhQQ Lightning Safety: https://www.youtube.com/watch?v=eNxDgd3D_bU So what do you do if you are out in the open, with no shelter or car protect you? You’ll want to stand away from large objects which have a better chance of being struck, and crouch low with only your toes in contact with the ground. Lightning can pass into the ground and spread out, coming into contact with you, so limited contact with the ground is ideal. Watch this video and read the article on lightning safety below. Monsoon A monsoon is a pronounced seasonal reversal in wind direction (N to S, E to W). The seasonal reversal of wind direction associated with large continents, especially Asia. In winter, the wind blows from land to sea; in summer, it blows from sea to land. Monsoons are commonly mistaken as a rainy season due to the Indian Sub-Continental monsoon and the heavy seasonal precipitation there. The North American Monsoon, while not a complete wind reversal, is a notable wind pattern that produces a dry spring with a relatively wet summer across the southwestern US and northwestern Mexico. In June, a high-pressure ridge in the upper atmosphere blocks moisture from moving into the Southwest. Winds aloft during this time are generally from the west. As the summer progresses, the high pressure moves north into New Mexico or around the Four Corners region. This causes a change in winds over the Southwest, bringing mid-level winds from the south and southeast. However, the moisture content through the atmosphere is still relatively low. There needs to be a mechanism near the surface to also draw in moisture for a significant change in water in the atmosphere. The dry conditions, combined with high solar angles produce extremely hot conditions over Arizona.

Credit: NCEP and NOAA

This hot air lowers the pressure over the southwestern US creating a thermal low at the surface. This thermal low, along with the high pressure aloft then begins to draw air from the south, bringing warm, moist air from the Gulf of California and even the Gulf of Mexico toward Arizona. The increase in moisture, combined with the hot conditions leads to an increase in precipitation (usually thunderstorms and haboobs) over the southwestern US and northwestern Mexico around July and continues into late September. We now have the two ingredients for a thunderstorm: moisture and an uplift mechanism in the form of surface convection. The thunderstorms which develop during the monsoon season are known for spectacular light shows. Compared to storms further east, the amount of moisture is still relatively low (despite the added moisture from Mexico). This causes storm clouds to have their bases higher in the atmosphere and also results in less precipitation. Because of this, the lightning produced by these storms is more prodigious and photogenic. In 2014, over a million cloud to ground lightning strikes were reported in Arizona. You can watch a video of the incredible visual show that the monsoon season puts on each year: https://www.youtube.com/watch?t&v=TC75USRhdho

STAGE B: Task B1 (2 questions like this) Fast Travel Observations

Your task in the first two questions of this stage will be to explore the geovisualization at several different locations and observe the relationship between topography, lightning, temperature, and precipitation. These questions are meant to start the process of exploring the spatial distribution of lightning and understand the mechanisms that lead to thunderstorm development. You will be asked to visit several different locations. Make a note and write down observations for the location and the surrounding landscape for the following concepts:

You will be given several detailed response options. The goal is not to confuse you but for you to make detailed observations. You can find an example of what responses you’ll need to make for a proper observation of the geovisualization concepts below. QUESTION: Travel to Sugarloaf Mountain (36.3628oN , -111.6142oW). Make observations of the location and surrounding landscape for the following categories:

Figure: Imagery from the top of Sugarloaf Mountain; top right image is satellite image; lower left is air temperature; lower right is precipitation

This is the way that the question will look in canvas with choices for each category:

ANSWER: • Topography: Sugarloaf Mountain is an elevated rhyolite dome located to the east of the San

Francisco Peaks at 2815 meters in elevation. • Land Cover: There doesn’t seem to be a substantial amount of vegetation on the eastern side of

the mountain either, leading to more exposure of the surface to the sun, causing it to be warmer than nearby locations that have thicker, green vegetation.

• Temperature: The air temperature at 10am is 20.7oC and the surface temperature is 36.7oC. Due to the time of this imagery being taken at 10am, the eastern side gets much more direct sunlight, and is 13oC warmer than the western side of this location.

• Precipitation: The precipitation is also lower here than the peaks to the west, which are at higher elevation. It receives 128mm of rain in August.

• Lightning: Lightning distribution is sparse directly around the location but a cluster is located to the south on the flanks of the San Francisco Peaks.

Task B2 (1 question like this): Lightning Transect

Your task for this section is to make a transect up around the San Francisco Peaks and observe the lightning strike distribution using the helicopter feature (or you can just run across the ground if you wish). A traditional way of gathering data in physical geography is to make observations along a line between two places, called a transect. That is what you will do in the game, observing the density of cloud-to-ground lightning strikes. The Transect (line between two places) question that you will see in canvas will be different! Most likely, you’ll be sent to travel up and over the San Francisco Peaks. But we wanted you to see the sort of question and also the sort of answer we are looking for …. QUESTION: Travel to Doney Park (35.2730 N, -111.50868 W). Then either take the helicopter fast-travel, or run to Sunset Crater (35.36371 N, -11.50295 W). Observe the lightning strikes across this transect.

CORRECT ANSWER: Lightning is lightly interspersed along the lava field towards Sunset Crater, with a large area of lightning strikes located to the south of Sunset Crater.

Task B3

Geovisualization/Imagery Comparison (1 question like this) In this section, you’ll be asked to visit a coordinate in the geovisualization, and then identify a picture taken of the actual observation based on your view. Actually, you will be matching 4 locations to 4 different pictures (A,B, C D). QUESTION: Fast travel to 35.3889 N , -111.7994 W and look northwest from that location. Identify which image best matches your view from the location. This location is looking at Mt. Kendrick, located to the west of the San Francisco Peaks. You should hopefully be able to see a resemblance between the view in the geovisualization, and the image. Your question in Canvas will be based around matching the images together.

Task B4 (1 question)

Wind Roses and Storm Movement

Wind roses represent wind flow at a location. The way you read a wind rose is that the “feathers” point in the direction where the wind is COMING FROM. We care about this in physical geography because the air moving into where we are is going to have different properties, leading to different weather. An example of this can be clearly seen with the North American Monsoon, where winds aloft shift from west/southwest to south/southeast, bringing moisture laden air from the Gulf of California and even the Gulf of Mexico into the Southwest US. These prevailing winds can shift daily though, and don’t necessarily equate to any seasonal change. Steering winds in the upper troposphere (zone of weather) will help move clouds that appear in the atmosphere, and can cause orographic uplift if the moving air runs into a mountainside. QUESTION: Pair the following video with the wind rose signifying the prevailing winds that are leading to the cloud movement. The video presented below is looking north. https://www.nps.gov/media/video/view.htm?id=77A56FC6-155D-451F- 670B425B68F88CC7

If we are looking north in the video of cloud movement, the arrow signifies that the clouds are moving to our right, meaning east. When looking at the Option B, the correct wind rose, it shows that 35% of the winds are coming from the west, at moderate speeds, and the air is calm 9.5% of the time. Option B is the wind rose we want to pick, since our clouds are moving east, that means that they are getting influenced by a wind blowing from the west, and the wind rose shows that westerly pattern. Meanwhile, with Option A, we would expect clouds to be moving directly away from our vantage point in the video, as the wind would be at our back, moving the clouds towards the north (southerly winds).

Task B5 (1 question)

Surface Temperature, Structures, and Lightning Strikes Visit the ski resort, Snowbowl (35.33037 N , -111.70459W), situated on the west side of the San Francisco Peaks. There are three main ski lifts on the mountainside. Below is a view of one of the ski lifts. Notice the area cleared of pine, fir, and aspen trees. This is the area of the subject of our question.

QUESTION: What is the most reasonable explanation for the warmer temperatures in the game at this spot 35.3306 -111.7058? and is it reasonable to interpret the linear lightning cluster you see as somehow connected to the chairlift’s location? First, fast travel in the game to Snowbowl and turn on the temperature layer. Look around. Second, turn on the LANDSAT layer and look the surface cover, you should be able to see an area cleared of trees. You should see something similar to the adjacent image when looking at surface temperature: You’ll be given the following possible answers for this question:

The cleared ski run is actually cooler than the surrounding forest, and this is because the sun evaporates water from the ground that then dries out. The lightning strikes in the area do not appear to have a linear alignment and seem much more randomly scattered.

The cleared ski run allows more solar radiation to reach the surface, heat up the surface, which then heats up the air above it. Also, the lightning strikes do appear to have a linear alignment that does seem to match up with the location of the chairlift, and so there could be a connection to the chair lift pillars standing in the middle of the cleared ski runs.

The cleared ski run is warmer than the surrounding forest and this is likely because more sunlight hits the surface and the warmer surface then warms up the atmosphere. The lightning strikes in the area do not appear to have a linear alignment and seem much more randomly scattered. Thus there does not appear to be an association with any linear chairlift.

Task B6 (1 question)

Lapse Rates To get you acquainted with ideas of convection, we’ll start by looking at atmospheric lapse rates. As the heated air rises off the surface, it cools according to temperature lapse rates. These lapse rates are simply the rate that temperature changes with height in the atmosphere. You may have worked with these lapse rates in the previous labs this semester, but below you can find a description of the lapse rates used in this lab. Dry Adiabatic Lapse Rate – imagine filling a giant balloon filled with air at the surface, and then you drag the balloon up into the atmosphere. The balloon will expand because of lower air pressure, and the molecules inside the balloon will be further apart. This results in cooling at a lapse rate of about 10 ˚C per 1000 meters when the air is “dry” (no clouds). Moist (wet) Adiabatic Lapse Rate – imagine that your rising giant balloon cooled enough to reach the dew point (the temperature when the water vapor in the atmosphere condenses and starts to form cloud droplets). When condensation occurs, heat is released (latent heat of about 580 calories per gram of water). This latent heat release slightly offsets the dry adiabatic cooling from expansion, and so the temperature change is a bit less. Just how much less depends on how much water is condensing. Environmental Lapse Rate – imagine climbing a ladder up into the atmosphere (or floating with a rising balloon). The air temperature of the thermometer you are carrying is the environmental lapse rate. This changes every day and throughout the day. Usually, temperatures go down as you go up into the atmosphere with an average of about 6.5 ˚C per 1000 meters (a kilometer), but vary depending on the time of year. This question looks specifically at the lifted condensation level (LCL). This is the height that the air parcel is cooled dry adiabatically to dew point. This height in the atmosphere is the lowest possible height with the present conditions that clouds could form. You calculate this height by taking your starting temperature and lifting it up into the atmosphere. When the parcel rises, it will cool adiabatically as it expands. First, at the dry adiabatic lapse rate if it is warmer than dew point, and then change to the wet adiabatic lapse rate at the LCL, as condensation begins and clouds form. QUESTION: Fast travel to Flagstaff (35.1983 N , -111.6513 W) . With a dew point of 9.5oC, what is the height of the lifted condensation level and air temperature 3000m above the surface if the air there is lifted adiabatically?

In this example, the air parcel starts above dew point, so you use the dry adiabatic lapse rate of 10oC per 1000m or 5oC per 500m. By cooling at this rate, the air parcel reaches dew point (9.5oC) at 3565 meters. This is the lifted condensation level. Now, since the parcel has reached dew point, the air parcel will cool at the wet adiabatic lapse rate, as clouds (condensation) is occurring. When this condensation occurs, some extra heat is transferred into the air temperature from this phase change from gas to a liquid. Above this height, the parcel is forming clouds, and cooling at 3oC/500m. ANSWER: the LCL occurs at 3565 meters and the air temperature is 0.5oC 3000m above Flagstaff

HEIGHT (500m)

Parcel

5065m 3.5 – 3 = 0.5oC

4565m 6.5 – 3 = 3.5oC

4065m 9.5-3 = 6.5oC

3565m 14.5 -5 =9.5oC LCL

3065m 19.5-5 = 14.5oC

2565m 24.5 – 5- 19.5oC

2065m (START) 24.5

THIS IS THE WAY THAT THE QUESTION FOR TASK A6 WILL LOOK IN CANVAS (with key information blanked out, because the information will vary from question to question in the pool of questions). NOTICE THE scale of the differences in the potential answers…

STAGE C: DETAILED INVESTIGATION

At this point, the developers of the lab assume that students completing Stages A and B have a basic grasp of:

- North American Monsoon - atmospheric stability - thunderstorm formation - making observations in the geovisualization for temperature, precipitation, topography, and

lightning distribution.

This stage will dive further into these concepts, providing context and more detailed ways that physical geographers analyze thunderstorms, focusing on the San Francisco Peaks. Like many places in North America, thunderstorm are not forming every day. There are temporal variations both seasonally and daily in these mountains. There are reasons why thunderstorms form in certain locations during certain times of year. Your goal in this stage is to investigate the origin of thunderstorms and evaluate how stability and topography fosters their formation. What you learn for northern Arizona applies to many other places in North America. While lightning and thunderstorm can be a complex subject to teach, we’re going to compress these ideas down into three major sections. Some of these concepts may be foreign to you, but just read through the example questions, and video tutorials to get more context if you find yourself confused:

Photo: Cumulus clouds building during a summer day over the San Francisco Peaks Source: Deborah Lee Soltesz USFS Coconino NF

Task C1 (1 question) Lightning Transect

You did this sort of thing in Stage B. This transect will be different than the example in Stage B and you will also have you look at the temperature layer instead of LANDSAT. For a reminder, Look at B2. The question will look like this:

1. Fast travel to …. and you will then be given coordinates on where to jump. 2. Use the helicopter fast travel mode to go from your current location to …. 3. Change the geovisualization layer to display air temperature. 4. While you are traveling, look at the lightning strike distribution as you look down from the

helicopter. THE QUESTION WILL BE: What lightning strike pattern do you observe while moving up and over the San Francisco Peaks in this transect? Hint: you will be asked in this question about the greatest clusters of lightning and where they are occurring.

Task C2 (1 question) Lightning Observations

The primary goal of this section of Stage C is to have you observe the variability in lightning strike location, both in terms of the topography that you find clusters, as well as the different surface temperatures. This question will ask you to match different latitude and longitude coordinates with a description of the lightning found there. Later in this lab, you will try to figure out why the different locations might have lightning present. The question will look like this: Match the lightning cluster coordinates with a description for the surrounding topography and lightning strike distribution. Make sure you're looking at the LANDSAT layer in the geovisualization. You will have to match four locations in the game to brief descriptions like “tight clusters”, “small clusters”, “broad clusters” and “wide section of distributed lightning strikes.Two examples are supplied below, so you can get the idea that its just a matching qualitative judgment. HINT: You can make things easier on yourself by taking screenshots of the four locations in the game so you can take your time in making the comparisons … and also use the screenshots to ask questions.

Go to 35.3258. and -111.6777, The avatar is standing on top of Agazziz Peak. The description would be something like this: No cluster of lightning located on this peak, although some isolated strikes are seen nearby.

Go to 35.3834. -111.6739 The avatar is standing on the slope of the main Francisco Peaks. The description would be something like this: The avatar is standing on a forested slope with an abundance of lightning strikes very nearby.

Task C3 (1 question) Precipitation Analysis

To set the stage for the rest of the lab, you will connect some of the ideas learned in the lecture from Stage B to understand why lightning strikes are shown for August, and not in May or June. It has to do with the change of moisture in the atmosphere, brought by the North American Monsoon. To prove this change, you will calculate the percentage of annual precipitation that falls in the months pre- monsoon (May/June) and during monsoon (July/August). You will use the precipitation table below and the following equation: Pre-Monsoon Monthly Percentage ={ [May and June Sum] / Total Annual Precipitation} * 100 Step 1: Add up the precipitation in May and June Step 2: Add up the precipitation for ALL Months Step 3: Divide Step 1 by Step 2 (it will be a fraction) Step 4: Multiply by 100 to make the answer be a percentage Monsoon Monthly Percentage ={ [July and August Sum] / Total Annual Precipitation} * 100 Repeat Steps 1-4 above, but for July and August

This is what the question will look like in Canvas:

WARNING: The level of detail needed for the rest of the questions in this

section may appear daunting at first.

Learning the science of how thunderstorms work to produce lightning patterns involves many steps and it also involves a fair amount of basic math. Some students do not want to delve into this detail, and other students are afraid of anything to do with math – even at the basic level, and that’s okay. There is no grade penalty for not doing questions in a lab or an assignment - this course is based on accrual grading.

We are hoping you try though. It is rewarding to answer these questions and gain a better understanding of the atmosphere and storms. If you find yourself stuck, be sure to read through the text, watch some of the video tutorial presentations, and ask questions!

Task C4 (1 question, 2 parts) Convection and Stability

INTRODUCTION TO TASK C4: As you’ll see in Tasks C4-C7, thunderstorms around the San Francisco Peaks often form over raised topography. However, this isn’t always the case. Up here on the Mogollon Rim, if conditions are right, thunderstorms can pop off from any location, even flat ground, and the sky is can be covered in a blanket of clouds, rain, and lightning.

Source: Brady Smith Coconino USFS

However, keep in mind that very often the first storms to form are typically over the raised topography. Later in the day, conditions can come together to lead to storms at any location. With that knowledge, we’re going to use this section to dive more into atmospheric stability and lapse rates over flat locations as a start. Convection is the transfer of heat upwards (hot air rises). These are the most basic summer thunderstorms, as surface heating and enough moisture near the surface can lead to primed conditions for clouds and eventually, thunderstorms to form. You’ve likely noticed from Task C1 that some lightning strikes were not around raised topography, and likely had to form through either surface convection, or storm movement. In this example, we’re going to assume that the steering winds are slow, and the storm was formed and dissipated over the same spot.

Task C4 Question Part 1 The first part of this lab will have you analyze the lifted condensation level and the adiabatic temperature if an air parcel if lifted from the surface up into the atmosphere. Please reference Stage A6 if you need to refresh your knowledge of this. You will use the calculated adiabatic temperatures from that stage to determine atmospheric stability in the next section of this stage. You can find the calculated temperatures in the adjacent table.

This is what you will do in canvas, just like in Stage A, Task A6

Task C4 Question Part 2

The second part of this question looks at atmospheric stability. Depending on the air temperature that the air parcel finds itself rising into, the air parcel will either continue to rise, stagnate, or sink back towards the surface. For this lab, we will primarily just be focusing on stable or unstable environments. If an air parcel is warmer than the surround environmental air temperature, it is described as unstable. Think of this like a hot air balloon on a cool morning. Warm air is less dense and more buoyant than cold air, so the air parcel (or hot air balloon) rises quickly up into the air. This allows the air parcel to continue to cool until it reaches dew point and form clouds. If an air parcel is cooler than the surrounding environmental air temperature, it is described as stable. The air is denser, and less buoyant than the surrounding air, and it will tend to sink back towards the surface. This type of environment leads to sunny skies, as the air parcels cannot continue to rise and reach dew point to form clouds.

Sometimes, you can get a mixed form of stable and an unstable atmosphere. This occurs when an air parcel that is lifted up into the atmosphere is cooler, or stable, in the lower part of the environment, but if the air parcel lifts above a certain height, it can reach air surrounding it that is cooler, leading to instability. This type of example is called conditionally unstable. If the surface warmed up through the day, or if the air was lifted to a height by a mountain or frontal boundary, it could conceivably reach the height which would lead instability and cloud formation/precipitation. The clouds that form as a result of atmospheric stability are directly linked with the amount of moisture found in the atmosphere. The air is more likely to be stable if the dew point is lower, leading to less heat through condensation in the air parcel. This stable atmosphere is more likely in the pre-monsoon months of May and June, while unstable and conditionally unstable conditions occur when more moisture is

present in the atmosphere. That is because both the dew point, as well as the environmental lapse rate change as summer progresses. You can see an example of the stability conditions below for a location in the geovisualization. You’ll have your own environmental lapse rate and location to consider when making your own calculations. But you will have to make the same selection. You will have to pick whether A, B or C is the environmental lapse rate condition that will be the most favorable for thunderstorm formation. QUESTION: Fast travel to Flagstaff at (35.1983 N , -111.6513 W). With a dew point of 9.5oC, what is in which environment would the air parcel become unstable and lead to thunderstorms?

HEIGHT (500m) Parcel Environment A Environment B Environment C

5065m 0.5oC 1oC -11.5oC -5.5oC

4565m 3.5oC 5oC -5.5oC 0oC

4065m 6.5oC 9oC 0.5oC 5.5oC

3565m 9.5oC LCL 13oC 6.5oC 10oC

3065m 14.5oC 17oC 12.5oC 15.5oC

2565m 19.5oC 21oC 18.5oC 20oC

2065m (START)

24.5oC - - -

Condition - STABLE UNSTABLE CONDITIONALLY UNSTABLE

In Environment A, the parcel is always cooler than the surrounding air, so it is likely to sink and be stable. Environment B has air constantly cooler than the parcel, so the air will rise, becoming unstable, and reaching the lifting condensation level (LCL) at 3565 meters when it reaches dew point. Environment C has stable air up until 4065 meters, but if the parcel could get lifted up a mountainside, or if it warmed more through the day to become warmer than the air around it, it may be able to reach a favorable, unstable environment, and form clouds and precipitation. ANSWER: The parcel is warmer than the environment AT ALL HEIGHTS, thus unstable, in Environment B.

Task C5 (1 question, 4 parts) Upslope Winds and Temperature Gradients

Typically, during the summer, general surface winds are much weaker. However, in mountainous topography, mountains can create their own winds. Surface heating along the mountain slopes creates a pressure gradient between air lower down and air near the top, because air near the mountainside is much warmer than the air aloft at the same height. As air flows from higher to lower pressure, this pressure imbalance leads to air flowing up the sides of the mountain, which is why they are called upslope winds. These upslope winds can be thought of as columns of air moving up the mountain slopes and rising away in towering, warm columns of air. You will use temperature instead of pressure. For example, look at the adjacent image. Air at the base of the mountain is the same temperature as air just off the mountainside. The air not near the mountainside cools faster than the air influenced by the sun-warmed slopes. This temperature difference leads to the air near the mountainside to be more buoyant (hot air rises, and to move up the sides of the mountain, continuing to rise above the peak if conditions are favorable, forming clouds, rain, and lightning. These graphics are a bit different and may connect better with you:

(Top) During the morning, the sun heats east- and south-facing slopes of mountains. Focus your attention on the sample air column. Note, near the bottom of the air column, how the constant pressure surface dips toward the mountain slope, indicating low pressure. Meanwhile, higher up in the air column, higher pressure helps to move air away from the mountain. (Bottom) In time, a thermally direct mesoscale circulation develops. Credit: David Babb You will be able to see this incredibly well in the surface/air temperature layer of the geovisualization. The example below is a different location example than what you will see in canvas.

QUESTION C5.1 EXAMPLE: Make sure the displayed layer in the geovisualization is set to temperature. Observe the air temperature in east Flagstaff (35.2321° N, -111.5731° W). Travel to the nearby top of Mt. Elden (35.24099 N , -111.59754W). Record the air temperature at the top of the peak there. For the sake of this example, we will round our heights to the nearest 100m. Flagstaff elevation: 2200m Flagstaff temperature: 23C Mt Elden elevation: 2800m Mt Elden temperature: 21C

QUESTION C5.2 EXAMPLE: Then travel due east and record the air temperature in 200m increments down the slope of the mountainside. Compare the air temperature you found along the mountainside to the environmental temperature above Flagstaff, found in the adjacent table. In this question, the environmental lapse rate is 6.5 C/km, or .65C/100m. Try to get to the nearest 200m increment as you can in the geovisualization.

300m down the slopes of Mt. Elden, due south. Notice the warm temperatures from the surface heating.

QUESTION C5.3 EXAMPLE: Compare your observed temperatures with the environmental temperatures. Choose the best answer in Canvas that represents what would be happening with the temperature pattern found between the temperature at the surface and the temperature aloft. ANSWER: Observed Air Temperature at Peak (2800m): 21C Environmental Air Temperature at Peak elevation (2800m): 19.1C Temperature Difference: +1.9C

HEIGHT (200m)

ENVIRONMENTAL TEMPERATURE

OBSERVED TEMPERATURE

2800 19.1 21

2600 20.4 22.4

2400 21.7 22.5

2200 23 23

Observed Air Temperature on Slope (2600m): 22.4C Environmental Air Temperature at Slope elevation (2600m): 20.4C Temperature Difference: +1.0C Your goal for this section will be to relate your understanding of atmospheric stability to the air near the surface of the mountainside, to the air aloft. The difference in temperature leads to a pressure gradient which you should be able to explain what occurs in Canvas. QUESTION C5.4 EXAMPLE: The temperature gradient you observed at the surface also exists aloft, creating another layer of uplift above Fremont Peak. The air at roughly 5000m Flagstaff is the same temperature, no matter the surface below it. That means that fairly strong temperature gradients exist above the warmed, raised peaks. Calculate the temperature gradient (in degrees C/km) between the two locations, Flagstaff, and Mt Elden, if the air aloft at 5000 meters is -5C. Temperature Gradient = (Temperature difference to 5k) / (Elevation difference between Location to 5k) Flagstaff to 5k Temperature Gradient = 23C – (-5C) / (5000m – 2200m) Flagstaff to 5k Temperature Gradient = 28C / 2.8km Flagstaff to 5k Temperature Gradient = 10 C/km Mt. Elden to 5k Temperature Gradient = 21C – (-5C) / 2.2km = 11.9 C/km ANSWER C5.4 EXAMPLE: The temperature gradient above Mt. Elden is also stronger than above Flagstaff, leading to another lifting mechanism caused by the upslope transport of warm air.

Task C6 (1 question, 3 parts) Thunderstorm Movement

Imagine you are walking around a hillside south of Flagstaff on a humid summer morning. You look to the south, towards Lake Mary and Anderson Mesa. The winds blow gently from the south and you observe a small cumulus cloud bubbling up, roughly 500m above the mesa. Conditions are perfect for a thunderstorm.

Cumulus clouds starting to form above Anderson Mesa near Lake Mary Credit Brady Smith Coconino USFS

While on many days, these storms tower up from the raised topography of the San Francisco Peaks because of low surface winds leading to upslope winds forming, this isn’t always the case. You should have noticed in the first section of this lab that some areas of lightning aren’t associated with any raised topography. They’re sitting in a middle of a plain, or around a low hill. How does that happen? Some days in northern Arizona, there are strong surface winds that cause orographic lift, while on other days, winds are mild near the surface but stronger aloft. These winds aloft are the primary source of direction for storms once they appear. If they don’t occur, these storms go through their lifecycle directly over where they form, which you may have seen already in the geovisualization. Other times, they move the storm clouds away from the raised topography and out into the open flats around the peaks. In this stage of the lab, you’ll identify lifted condensation levels and storm speed to figure out how long it will take for a thunderstorm forming over the raised topography around the San Francisco Peaks to reach your locations.

Part C6.1 EXAMPLE QUESTION C6.1: What would the dew point have to be for clouds to form 800m above Anderson Mesa (35.1174 N, -111.5840W), if a strong southern breeze was blowing from Lake Mary (35.1069 N, -111.5825 W) For this question, we want the lifted condensation level (LCL) to be at the 800m above Anderson Mesa (2185m). That would be 2985 meters, which is compared to Lake Mary (2065m) is 920 meters above. The temperature at Lake Mary is 24.0C.

Remember that the dry adiabatic lapse rate is 10C/km (or 1C/100m). Because the elevation difference is 920 meters, we know that the air would have cooled 9.2C upon being lifted up Anderson Mesa and into the atmosphere. For condensation (clouds) to occur at 800m above Anderson Mesa, the dew point needs to be equal to the air temperature at this height. So…. Dew Point = Starting temperature – (Elevation Change * Lapse Rate) Dew Point = 24.0C – (.92km * 10C/km) Dew Point = 24.0C – (9.2C) Dew Point = 14.8 C for clouds to form 800m above Anderson Mesa (58F dew point is about as humid as it gets for this region) ANSWER: If we begin with a southern at Lake Mary and a temperature of 24 C, the dew point would have to be 14.8C (58F) for clouds to begin forming 800 meters above Anderson Mesa.

C6.2 For lightning to form in a cloud, it needs to reach a certain height in the atmosphere, where interactions within the cloud begin to create static charge buildup, resulting in lightning. For this example, we will use a height of 10kilometers, or 10,000 meters, for this interaction to occur, and the storm to reach mature stage. We also need the updraft speed, essentially how fast the storm is growing upwards. For this example, we will use 300m/min. EXAMPLE QUESTION C6.2: How long will it take for a 10km-tall thunderstorm to form above Anderson Mesa if the updraft winds are 300m/minute, and the LCL is 800m above the mesa? From the top of Anderson Mesa, we will have to rise our tiny cumulus cloud up to 10 kilometers. Since Anderson Mesa is 2,185 meters high, and the base of the cloud is 800 meters above, the cloud base is 2985m, and would need to climb 7015 meters to reach a height corresponding to thunderstorm maturity and lightning. We know how fast the air rises in the updraft above the mountain, which is 360m/min. So we need to figure out long it will take air rising at 300m/min to reach 7015 meters above our lifted condensation level (rising 10,000 meters elevation). This is the calculation: ANSWER: 7015m / 300m/min = roughly 23.4 minutes

C6.3 EXAMPLE QUESTION C6.3: How fast is the wind steering the storm from Anderson Mesa to our location of clustered lightning strikes? It takes roughly 23.4 minutes for our cumulus cloud to form and create a towering thunderstorm capable of lightning with the current atmospheric conditions. So we now have our time for lightning formation, we just need to figure out how fast the steering wind is that is propelling the thunderstorm towards our location. We have our distance from Mt. Elden to our lightning hotspot, and that’s 8.5km. To find how our speed in kilometers per hour, we will have to convert our original time into hours. ANSWER: Hours = 23.4 minutes / 60 minutes = .39 hours Wind speed = Distance / Time Wind speed = 14km / .39 hours = 35km/hour or 21 miles per hour

Task C7 (3 questions from a pool of similar questions)

Connecting what you learned to lightning You have learned about convective uplift, atmospheric stability, orographic and upslopes winds, as well as prevailing winds and storm movement. The final section for Stage C will give you an opportunity to earn more points applying your understanding, by giving you lightning location coordinates. You’ll be asked to observe the LANDSAT and temperature layer, the lightning strikes, as well as a wind rose (see Stage A4 for a refresher). Then, you will be asked to identify the predominant cause for lightning striking at that location. The question will be the same for all of Task C7:

EXAMPLE QUESTION: Given your observations, and the prevailing winds, identify the predominant mechanism that lead to the lightning cluster at this location.

YOU WILL BE GIVEN A WIND ROSE FOR YOUR QUESTIONS … and this is the example wind rose for those location. Thus, this is the interpretation: Looking around the landscape for this location, we can see that while there are some hills around the landscape, they likely aren’t large enough to create significant upslope winds. Looking at the wind rose, we can see that the winds are variable, in different directions, and through most of the day (73%), calm.

We conclude that the thunderstorm that formed these lightning strikes was likely convective, forming over this location simply because of surface heading. The same thing that happens on a stove when the water starts to boil happened here. Because the winds were so weak and variable, didn’t go anywhere, a thunderstorm grew, matured, and dissipated above this point with these conditions. ANSWER: Surface convection thunderstorm, weak and variable steering winds

STAGE D. SYNTHESIS An important part of climate science is looking at multiple pieces of information. In your case study in Stage C you explored temperature, dewpoint, instability of an air parcel, and wind direction (both at the surface and the way storms move). One example alone is not enough to make proper judgments on understanding the cause of lightning clusters. Each aspect must be taken with caution and related to each other. Look for patterns and relationships. While this case study has been simplified (climatologists use a lot of statistics and statistical tests) and there are many other factors one could (and would) look at, be sure to keep in mind to use all the information at your disposal. This essay tasks you with explaining your thinking about some of the basic concepts explored in this lab. Please follow the instructions below in what to include in your paragraphs. Make them beefy. In other words, do not just write one or two general sentences in each paragraph. Try to include evidence and reasoning. More detailed answers earn the most points. Paragraph 1: Briefly explain your understanding of changes throughout the year in temperature, moisture, and precipitation in the Flagstaff – San Francisco Peaks area. Focus on the difference between the Monsoon season (July-August-September) and the rest of the year Paragraph 2. Briefly explain your understanding of atmospheric stability and how thunderstorms develop (their different stages) and at which stage would you expect the most lightning. Paragraph 3. Briefly explain how mountains impact weather, particularly with respect to cloud and storm formation. What major concepts lead to mountain thunderstorms? Paragraph 4. This is where you get your chance to explain the distribution of lightning that you see in the geovisualization. Feel free to refer to specific locations (e.g. Fast Traveling locations) as examples of your thinking. We understand that this is all new to you. We understand that you are not a climatologist, but just in a 100-level class. We will take that into account.

REMINDER: WHAT FOLLOWS ARE SCEENSHOTS FROM CANVAS ARE QUESTIONS WITH PULL-DOWN MENUS FOR TASKS C4, C5, C6, AND C7.