John Bluck									July 16, 2002
NASA Ames Research Center, Moffett Field, Calif.			
Phone: 650/604-5026 or 604-9000
E-mail: jbluck@mail.arc.nasa.gov

RELEASE 02-80AR
STUDY OF CLOUD ICE CRYSTALS MAY IMPROVE CLIMATE CHANGE 
FORECASTS

Studies of cirrus clouds by some 450 scientists may lead to improved forecasts of future 
climate change.

This month in southern Florida, scientists will investigate high tropical cirrus clouds 
composed of tiny ice crystals. The scientists hope to determine how the clouds form, 
how they limit the amount of sunlight reaching the surface of the Earth and how they 
trap heat rising from the surface and lower atmosphere. This key information will help 
improve computer programs that forecast global climate change.

"Our objective is to find out how ice clouds affect global warming," said Eric Jensen, 
project mission scientist at NASA Ames Research Center in California's Silicon Valley. 
"The combination of measurements and computer modeling studies will improve our 
understanding of how cirrus (clouds) may change in response to climate change," he 
said. "For example, as the surface heats up and thunderstorms become more intense, will 
larger, thicker cirrus clouds be formed?"

Scientists from NASA, other government agencies, academia and industry will 
investigate cirrus clouds in Florida with the objective of reducing uncertainties in 
forecasts of the Earth's future climate. High, tropical cirrus clouds are composed of tiny 
ice crystals that float at altitudes from 20,000 feet (6,096 meters) to 60,000 feet (18,288 
meters). Scientists will take measurements from a variety of aircraft and ground 
instruments for four to six weeks beginning this month. They plan to analyze and report 
their data by the spring of 2003. The effort is called the Cirrus Regional Study of 
Tropical Anvils and Cirrus Layers - Florida Area Cirrus Experiment 
(CRYSTAL-FACE).

"Clouds are the largest source of uncertainty in computerized global climate models," 
Jensen said. "We want to measure the ice crystal sizes, cloud optical depths and the 
heating or cooling of the Earth's surface caused by tropical cirrus clouds, particularly 
those generated by intense storms." Optical depth is a measure of the visual or optical 
thickness of a cloud.

Recent observations from NASA's Terra satellite, with improved sensitivity to detect 
cirrus cloud systems, suggest that cirrus are present more than expected both temporally 
and spatially across the planet. Cirrus may act to warm or cool the planet and the 
tendency toward warming or cooling depends on the extent, duration, thickness and 
location of the clouds.

A major scientific goal is to use cloud measurements from aircraft to calibrate remote 
cloud measurements from satellites so characteristics of clouds can be observed more 
accurately from the higher altitudes of orbiting spacecraft. Better-calibrated satellite 
observations of clouds will result in improved large-scale measurements of clouds 
because as satellites orbit Earth, they can observe huge areas of the globe at once. These 
satellite cloud measurements will enable scientists to make more accurate regional and 
global cirrus cloud computer models that should reduce the uncertainty of climate 
change predictions, Jensen said.

"We anticipate flights will be mostly over southern Florida, and occasionally we will 
sample clouds over the ocean," Jensen said.

Many of the scientists and aircraft involved in CRYSTAL-FACE will be based at Key 
West Naval Air Facility, Fla., during the experiment. Six aircraft types will carry 
instruments to measure cirrus clouds. The high-flying ER-2 (similar to a U-2), based at 
NASA Dryden Flight Research Center, Edwards, Calif., will conduct remote sensing of 
cirrus clouds and environmental conditions, as will the Proteus aircraft, built by Scaled 
Composites, Mojave, Calif. Scientists will compare the ER-2 instrument readings with 
similar satellite measurements.

The WB-57 aircraft based at NASA Johnson Space Center, Houston, will be making in 
situ measurements of cirrus clouds and environmental conditions. A Citation aircraft 
from the University of North Dakota will make in situ measurements in the lower parts 
of cirrus 'anvils.' An anvil is an extensive ice cloud that forms at the tops of deep 
thunderstorm clouds.

A P-3 aircraft, based at the Naval Air Station, Patuxent River, Md., and provided by the 
Naval Research Laboratory, will use airborne radar to measure cloud structure and 
intensity. A Twin Otter airplane from the Center for Interdisciplinary Remotely Piloted 
Aircraft Studies, which is part of the Naval Postgraduate School and is based at the Navy 
Airport near Fort Ord, Calif., will make in situ measurements of aerosols and take other 
readings. Ground-based instruments in the study include radar and other instruments. 
Satellites included in the study will be GOES, Terra, Tropical Rainfall Measuring 
Mission and Aqua.

In addition to Jensen, other scientists from NASA Ames will take part in the 
CRYSTAL-FACE project. They include Andrew Ackerman and Katja Drdla, Jensen's 
co-investigators who are working on cirrus cloud computer modeling. Peter Pilewskie of 
Ames and his colleagues will use instruments on the ER-2 and Twin Otter aircraft to 
measure trapping of heat and reflection of sunlight by clouds. Max Loewenstein's 
experiment includes measurements of carbon monoxide and methane. Paul Bui and 
others from Ames are responsible for measurements from the WB-57 and ER-2 aircraft 
of temperature, pressure and winds. Henry Selkirk and Leonhard Pfister are studying 
development and movement of cirrus clouds. Selkirk also will be the lead forecaster for 
the mission.

Participants include researchers from various NASA centers including Ames; Goddard 
Space Flight Center, Greenbelt, Md.; Langley Research Center, Hampton, Va.; and the 
Jet Propulsion Laboratory, Pasadena, Calif. Participating government organizations 
include the Department of Defense Office of Naval Research, the National Science 
Foundation, the National Oceanic and Atmospheric Administration, the Department of 
Energy and The National Polar-orbiting Operational Environmental Satellite System.

A complete list of participants is on the project Website at:

http://cloud1.arc.nasa.gov/crystalface/

Project manager Michael Craig of the Ames Earth Science Project Office is in charge of 
the field campaign for NASA. CRYSTAL-FACE will be the largest mission ever run by 
the Earth Sciences Project Office.

This research is part of NASA's Earth Science Enterprise, a long-term research effort 
that utilizes the unique vantage point of space to view our home planet to better 
understand and protect life here, while exploring for life in the universe. 
CRYSTAL-FACE will support data validation of NASA satellite investigations, including 
EOS Terra and Aqua satellite missions and the Tropical Rainfall Measurement Mission.

A fact sheet about the mission is on the World Wide Web at:

http://amesnews.arc.nasa.gov/factsheets/FS-02-03AR.html

Publication-size images are available on the Internet at:

http://amesnews.arc.nasa.gov/releases/2002/02images/cirrusclouds/clouds.html

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