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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.


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.

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

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

Different PDF File


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:


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:


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

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:

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:

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?
Are you under a tall tree?
Lightning Safety:

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

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:


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:


• 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.

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



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

(START) 24.5



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…



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

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


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 …

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