Lesson 18: How the Wind Affects Drone Pilots 

Welcome Back! 

Today, we’ll dive deep into the world of wind, and how the wind can affect our drone missions.

Did you know that buildings, structures, and landscape features can affect wind direction and speed close to the ground?

We have to make sure to remember how wind can affect our drone operations. But first, how does the wind actually work??

Wind is caused by differences in air pressure and temperature. Cold air sinks and hot air rises, which creates the air flow, which we know as wind.

Ever wonder why you experience bumpy turbulence in an airplane? It’s scary! But science helps us explain that mystery.

The reason for turbulence is something called “convective currents.” It applies to big planes as much as small drones.

You know how it’s hotter when you walk on asphalt than when you walk on grass?

That’s because asphalt absorbs more heat. The warm air rises and heats the air above it.

Grass absorbs less heat, so the air is cooler above it, and so it doesn’t rise as much.

Well, the entire earth works this way! It’s filled with all sorts of different environments.

Different environments, like land, water, and cities, heat up at different rates, which causes the air to move up or down, causing turbulence as the temperature and air pressure changes.

And that’s what a convection current is! Let’s explain it some more.

Convective Currents are areas where uneven heating of the air causes air to move up or down and create bumpy, turbulent flights. Warm air rises up (updrafts), and cool air sinks down (downdrafts).

Today’s 🔑 Word!

Convective Currents 

Like we mentioned, different surfaces give off different amounts of heat.

Plowed ground, rocks, sand, and barren land radiate lots of heat – what I’m standing on!

Water, trees, grassy areas, and other plants tend to absorb heat.

If you’ve ever been to a beach, you might’ve experienced this! On a hot day, the sand is way warmer than the water.

Well, that’s good to know! But now, let’s explain why this information is useful for a pro drone pilot to know.

If you’re flying over different types of surfaces, you might experience updrafts while flying over pavement, rocks, or sand, and downdrafts when flying over trees or water.

Remember that updrafts are when warm air rises up, and downdrafts are when cool air sinks down.

And this means that flying over different surfaces that radiate heat differently will make you fly in a wavy line instead of a straight line.

And this means that flying over different surfaces that radiate heat differently will make you fly in a wavy line instead of a straight line.

Convection Currents are important for drone pros to know about because they can make your flight bumpy and make it harder to control.

Here’s another type of wind we need to be careful of when we fly near water – sea breezes and land breezes.

… But what are they?

What are Sea Breezes and Land Breezes? They’re local winds caused by the difference in temperature between land and sea.

During the day, the land will heat up faster than the water, so the air all over the land becomes warmer and less dense (bumpy!).

The warm air rises, and then is replaced by the cooler, denser air flowing in from over the water sinks down. They take turns!

A sea breeze occurs during the day when the land heats up faster than the sea, causing the warm air over the land to rise. Cooler air from the sea then moves in to replace the rising warm air, creating a breeze that blows from the sea towards the land.

Today’s 🔑 Word! 

Longitude Sea Breezes vs. Land Breezes

Sea breezes can create stronger winds blowing towards the land during the day, which might impact how your drone lands. 

At night, the opposite happens!

The land cools faster than the water, so the warmer air over the water rises, and the cooler, denser air from the land replaces it.

A land breeze occurs at night when the land cools down faster than the sea, causing the warmer air over the sea to rise. Cooler air from the land then moves in to replace the rising warm air, creating a breeze that blows from the land towards the sea.

Land breezes can cause winds to blow out to sea at night, affecting takeoffs from coastal areas. 

Pilots need to know about sea and land breezes because these local winds will affect how well your drone can takeoff, fly, and land.

If you know which direction the wind might be blowing in, you can understand the weather better and make smart choices for your flight.

And knowing about land versus sea breeze can help with effective flight planning and become a certified Drone Pro!

Wind also plays another critical role in drone missions, and the layout of the land can tell you where and how fast the wind is.

Wind behaves differently in cities than near mountains. Different obstacles can change the wind’s speed and where it comes from.

Like, tall buildings usually block and redirect wind, creating areas of turbulence and sudden changes in wind speed. Near skyscrapers, wind can swirl around them!

Hills and valleys also impact wind patterns. Hills make wind go faster, as the wind speeds up and over them. Wind can get squeezed into valleys, which makes it move faster through them.

Knowing how wind interacts with the environment can help you avoid turbulent areas, and help us plan way more stable, safe, and controlled flights.

So, if it’s too windy,

So, if it’s too windy, you might want to think about rescheduling your flight.

… What if I fly my drone near the mountains?

If you’re flying a drone in the mountains, you’ll want to be aware of the way the wind flows along the mountains’ surface.

The wind will flow smoothly up one side of the mountain, but be turbulent on the other side. This is called a katabatic wind!

This wind will push your drone toward the mountain, and then push it down! You can blame gravity for that.

Katabatic Wind? Maybe worth rethinking…

What other dangers should I watch out for? 

Drone pilots need to watch out for a dangerous type of wind called “wind shear.”

Wind shear is a sudden, intense change in wind speed or direction over a small area. It can occur at all altitudes and in all directions.

It usually means the wind suddenly changes direction by 180 degrees (it starts blowing in the exact opposite way). The speed can change by 50 knots (that’s 57 MPH!) or more (a very big change in speed).

And wind shear at low altitude can be super dangerous–it can push your drone sideways really hard!

And wind shear at low altitude can be super dangerous–it can push your drone sideways really hard!

Wind shear is a sudden change in wind speed and/or direction over a short distance in the atmosphere. 

This change can occur either horizontally or vertically and can affect both low and high altitudes.

Wind shear sounds intense! But, how do we know when it might happen to make sure we avoid it?

Wind shear happens with thunderstorms, cold fronts, warm fronts, and strong winds high up in the sky (over 25 knots, or 29 MPH).

Wind shear can be so dangerous that many airports actually have systems that warn pilots about when it’s happening!

These warning systems are called low-level wind shear alert systems or LLWAS for short.

Wow, there are so many stressful types of wind! Ready for the next one?

Microbursts are sudden and powerful downward air currents.

These rapid wind shifts can lead drone pilots to lose control of their drones and even crash them!

Microbursts occur in a space of less than one mile horizontally and within 1,000 ft vertically for about 15 minutes.

They can create extreme downdrafts of up to 6,000 ft per minute.

They can make the wind change direction dangerously–45 degrees or more–within seconds.

That’s almost like an upside-down tornado!

It can be difficult to detect microbursts because they happen in such small areas.

Stay informed about weather conditions like thunderstorms to minimize your risks of encountering microbursts.

A microburst is a small, intense burst of wind that comes down from a thunderstorm and spreads out quickly when it hits the ground. It can cause sudden and strong wind changes in a small area, which can be very dangerous for planes and drones. 

All right, one more wind-related topic. 

You know how the higher up you go in the air, the colder it gets?

Like, how there are mountain peaks that have snow on them year-round?

There’s a weather condition where the opposite happens, and it gets warmer as you get higher.

This is called low-level temperature inversion.

In these conditions, the air is often stable and smooth, but there is poor visibility due to fog, haze, or low clouds. 

A low-level temperature inversion is when a layer of warmer air sits above cooler air near the ground. This is unusual because normally, air gets cooler as you go higher. This can make the air feel stable, but it can also trap pollution and create fog or smog close to the ground.

Think of a big city–it’s hazy around the city, but the sky above it is clear.

If it’s windy, these conditions can also be a recipe for wind shear!

Drone pilots should be aware of low-level temperature inversion because the differences in air temperature and pressure can affect the stability of your drone.

Things to Remember 

The Wind:

Understanding different types of wind like convective currents, sea and land breezes, and microbursts helps drone pilots plan their flights.

Buildings and mountains can change how the wind flows. This can make the wind gusty and change direction suddenly.

Microbursts are sudden, powerful winds that can push our drones down really fast. They happen in a small area and can be hard to see coming. 

Low-level temperature inversion can cause hazy conditions. 

Great work! I see you’re all a few steps closer to becoming a certified drone pilot.