Contrails vs Chemtrails

Distinguishing Contrails from Chemtrails: Science and Myths

In the skies above, the presence of airplane trails has sparked discussions about their origin and implications. Two terms often mentioned in this context are “contrails” and “chemtrails.” These terms, however, carry distinct scientific meanings and have led to contrasting interpretations.

Contrails (Condensation Trails): Contrails are a natural phenomenon that occurs when aircraft engines emit exhaust containing water vapor and other byproducts. At high altitudes, where temperatures are significantly colder, this exhaust condenses into visible ice crystals or water droplets, forming a trail behind the plane. These trails are temporary and typically dissipate relatively quickly. Contrails are a normal consequence of aircraft operations and result from the interaction between engine emissions and atmospheric conditions.

Chemtrails (Chemical Trails): The term “chemtrails” refers to a speculative conspiracy theory that claims certain airplane trails are composed of chemical or biological agents deliberately released into the atmosphere for undisclosed purposes. Proponents of this theory often present photographs of persistent and spreading trails as evidence of intentional, harmful spraying. However, the scientific community widely dismisses the notion of chemtrails. Extensive research, including air quality analysis and aircraft emissions studies, has failed to provide credible evidence supporting the existence of chemtrails as described in the conspiracy theory.

What temperatures do commercial airlines operate within?

1. Lower Troposphere (0 – 10,000 feet): This is the layer of the atmosphere closest to the ground. Temperatures in this layer can vary widely based on weather conditions and location. At cruising altitudes within the lower troposphere, temperatures could be in the range of -30 to 10 degrees Celsius (-22 to 50 degrees Fahrenheit).
2. Mid-Troposphere (10,000 – 30,000 feet): As you go higher, temperatures tend to decrease with altitude. In the mid-troposphere, temperatures can be colder, ranging from around -40 to -10 degrees Celsius (-40 to 14 degrees Fahrenheit).
3. Upper Troposphere and Lower Stratosphere (30,000 – 50,000 feet): Commercial airliners often cruise in this altitude range. Temperatures at these altitudes can vary between -50 and -20 degrees Celsius (-58 to -4 degrees Fahrenheit). This is where contrail formation is common due to the cold temperatures and exhaust from jet engines.

Contrail visibility calculator

Generally contrails will form at above 25,000ft, when the relative humidity is also above 60%. You can use the sliders below to get a rough idea of when you are likely to see contrails. Combine that with your local weather at the given altitudes alongside plane tracking information to see if they all match.

Can contrails suddenly stop, as if being switched off? Let’s’s look at the reasons why.

Temperature gradients in the atmosphere can vary widely based on the specific atmospheric conditions, altitude, and geographic location. The rate at which temperature changes with altitude is known as the “lapse rate.” Lapse rates can be steep or shallow, and they can impact the behaviour of contrails during aircraft ascent or descent.

Contrails are sensitive to temperature and humidity conditions. If an aircraft passes through an area with a sudden change in temperature and humidity, it can affect contrail formation and persistence. Here are a few scenarios to consider:

1. Lapse Rate Changes: If an aircraft ascends or descends through a layer of air with a significant change in lapse rate, it can impact contrail formation. For example, if an aircraft enters an area with a steep lapse rate (temperature decreasing rapidly with altitude), contrails might form more easily due to the rapid cooling of exhaust gases. Conversely, if an aircraft enters an area with a less steep lapse rate, contrail formation might be less pronounced.
2. Sudden Temperature Changes: Sudden temperature changes can impact contrails. If an aircraft encounters a sudden drop in temperature, it can cause contrails to freeze more quickly, leading to more persistent contrails. On the other hand, if an aircraft moves from a colder to a warmer region, contrails might dissipate more rapidly.
3. Humidity Changes: Humidity levels also play a role. If an aircraft enters an area with lower humidity, contrails might dissipate quickly due to sublimation (conversion of ice crystals to water vapor). Conversely, if an aircraft enters an area with higher humidity, contrails might persist or even spread out, forming cirrus-like clouds.
4. Atmospheric Layers: The behavior of contrails can vary when crossing atmospheric layers with different characteristics. An aircraft passing through a temperature inversion (where temperature increases with altitude) might experience changes in contrail behavior.
5. Local Variations: Microscale atmospheric variations can also impact contrail behavior. These variations can result from factors like local wind patterns, terrain, and weather fronts.

Regarding the thickness of temperature gradients, it’s important to note that these gradients can vary widely. A lapse rate of around 2-3 degrees Celsius per 1,000 feet is considered normal, but it can vary based on atmospheric conditions. Steeper lapse rates can lead to more pronounced contrail formation.

These factors can give the impression that an aircraft suddenly “switched off” its contrails, even though the change is due to the complex interplay of atmospheric conditions. Contrail behaviour is a dynamic process influenced by a combination of temperature, humidity, lapse rates, and local variations. As aircraft move through different atmospheric regions, contrails can appear to change or disappear as a result of these atmospheric factors.

Clouds are forming from the contrails, is this still cloud seeding?

Contrails transforming into cirrus clouds and cloud seeding are two different atmospheric phenomena, though both deal with the formation and modification of clouds. Here’s a comparison:

Contrails to Cirrus Clouds

1. Mechanism: Contrails are formed when hot jet engine exhaust cools and condenses upon contact with cold upper atmospheric air. The water vapor in the exhaust forms tiny ice crystals. These contrails can either evaporate quickly or persist and spread out, depending on atmospheric conditions.
2. Result: If the surrounding atmosphere is humid enough, these ice crystals will attract more water vapor, causing the contrail to grow and spread. Over time, these persistent contrails can spread out to such an extent that they become indistinguishable from naturally occurring cirrus clouds.
3. Purpose: Contrails forming cirrus clouds is a non-intentional byproduct of high-altitude flight. These high-altitude, man-made cirrus clouds can have a slight warming effect on the Earth’s surface, as they trap outgoing longwave radiation.

Cloud Seeding

1. Mechanism: Cloud seeding is the intentional introduction of agents like silver iodide, potassium iodide, or crushed dry ice into clouds to stimulate the cloud particles and lead to precipitation. These agents serve as nuclei around which moisture can condense or freeze.
2. Result: The goal of cloud seeding is typically to enhance precipitation, reduce hail damage, or increase snowfall in mountainous regions to augment water supplies downstream. The efficacy of cloud seeding remains a topic of research and debate, though there’s some evidence to suggest it can be effective under specific conditions.
3. Purpose: Cloud seeding is done for specific purposes like augmenting water supplies in reservoirs, reducing drought impacts, or controlling forest fires.
4. Types of Clouds Affected: Cloud seeding is usually done on clouds that already have some potential for precipitation but need some help to release it. These are typically cumulus or cumulonimbus clouds (for rain) or stratus or orographic lift clouds in colder mountainous regions (for snow).

In summary, while both phenomena deal with clouds, contrails naturally transitioning to cirrus clouds is a passive process resulting from jet flights at high altitudes. In contrast, cloud seeding is an active attempt to modify cloud behaviour, usually to enhance precipitation.