# Presentation: 374754

## The GLOBE Contrail Protocol:  A Student-Scientist Partnership

- Dr. Lin Chambers
- NASA Langley Research Center
- Hampton,VA

## Science Objectives

- Obtain contrail and other cloud information from the largest possible network of ground observers
- Use to:
- Validate satellite retrieval algorithms
- Improve contrail prediction methods

## Education Objectives

- Involve students in accessible observational science
- Lead students into larger atmospheric science issues

## Outline

- What are contrails?
- Why is NASA involved?
- Why and how are students important to this study?

## Outline

***What are contrails?***
- Why is NASA involved?
- Why and how are students important to this study?

## What are Contrails?

- Contrails are **CLOUDS** that form in the wake of aircraft.
- Contrail is a shortened name for condensation trails.
- Also known as vapor trails, jet trails, “chemtrails”

**Notes:**
Contrails are clouds that are made up of ice crystals, or rarely, water droplets.

## Contrails have been around for a long time!

- They were first described in the scientific literature in 1919.
- During WWII, contrails sometimes littered the skies during aerial combat.

**Notes:**
Although we tend to associate contrails with jet aircraft, propeller-driven aircraft can sometimes make contrails.
During the Battle of Britain in WWII, dogfights between British Spitfires and German Bf109s occasionally produced contrails.

## What is a Mixing Cloud?

- The cloud that forms
- on your breath during
- a cold day is a mixing
- cloud

**Notes:**
When air temperature is 20 deg F, your breath can hold over 16 times as much water vapor as an equal volume of the cold air!

The remarkable thing about mixing clouds is that neither the cold air nor the warm air have to be saturated to make a cloud.  Thus contrails can occur in otherwise clear skies.  Some people mistakenly think that the aircraft must be “spraying” something into the atmosphere since the relative humidity isn’t 100 percent.

## Do Contrails Affect Cloud Cover?

## Outline

- What are contrails?
***Why is NASA involved?***
- Why and how are students important to this study?

## Global Cloud CoverAugust 26, 1993

## Slide 12

## Slide 13

## Derived Product

**Derived Product**
**Requires Cloud Detection and Cloud Property Retrieval**

## Why Do We Study Contrails?

- When the upper
- atmosphere is
- moist enough,
- the contrails
- continue to grow.
- Under these
- conditions, the
- contrails become
*persistent.*

## We currently estimate that contrails add an additional 0.5 to 5 % warming to the greenhouse gas effect.

- Persistent contrails occasionally cover large areas.
- Like cirrus clouds, contrails likely contribute to global warming.

## Air traffic and persistent contrail coverage will continue to increase.

## By 2050, warming due to contrails may be 2.5

- to 25 % of the current greenhouse gas warming.

**Notes:**
Notice the large uncertainty in our current estimates.  Twenty five percent is something to be concerned about.
2.5 percent is probably not important.

## Outline

- What are contrails?
- Why is NASA involved?
***Why and how are students important to this study?***

## Why can students help?

- Our estimates of the climatic effects of persistent contrails are still uncertain.
- We still have trouble estimating contrail coverage.

**Why can students help?**

**Notes:**
We also have problems getting global estimates of contrail thickness and particle size.

## Most contrails are still smaller than the resolution of most satellites.  

- Most contrails are still smaller than the resolution of most satellites.

**Why can students help?**

**Notes:**
Contrails usually don’t last more than a few hours.  We must use geo-synchronous satellites to study them more properly, but these satellites lack the necessary resolution for us to identify all contrails.

## Data Sheet

## Initial GLOBE Contrail Data Analysis

- Dr. Dave Duda, Hampton University

**Method **
- Compare GLOBE obs to:
-  RUC (Rapid Update Cycle; Benjamin et al.)
-  ARPS (Advanced Regional Prediction System; Xue et al.)
-  Initial comparison for April 2004
-  1500 GLOBE observations of contrails

## Website & Activities

- http://asd-www.larc.nasa.gov/GLOBE/

## Some other things you may see...

## Inverse contrails (distrails)

- Aircraft sometimes make holes in clouds!

## Contrail Cousins

- Cloud “zippers” on Father’s Day, 2004