Science From Space

The lifestyles of hurricanes

A campaign to gather the most extensive set of hurricane measurements became a phenomenal success just halfway through its flight time. By the time the third Convection and Moisture Experiment (CAMEX-3) had finished, investigators had explored hurricanes Bonnie, Danielle, Earl, and Georges. Robbie Hood of NASA's Global Hydrology and Climate Center (GHCC) was the lead mission scientist. It involved hurricane researchers from the National Oceanic and Atmospheric Administration (NOAA) and the U.S. Air Force Reserve 53rd Weather Reconnaissance Squadron.

Right: Flight track of research aircraft is plotted atop an image of Hurricane Danielle.

Among the dozens of instruments were five from the GHCC - the Multi-center Airborne Coherent Atmospheric Wind Sensor (MACAWS), the Advanced Microwave Precipitation Radiometer (AMPR), the Lightning Instrument Package (LIP), and the Multispectral Atmospheric Mapping Sensor (MAMS) on NASA's ER-2 and DC-8 aircraft, and the Lightning Imaging Sensor on the Tropical Rainfall Measuring Mission spacecraft.

While hurricanes have been probed by aircraft since the 1940s and monitored by satellites since the 1960s, this was the first coordinated campaign to measure a hurricane's growth with aircraft at low, medium, and high altitudes. CAMEX-3 was designed to study the factors involved in how strong a hurricane grows, including the uptake of energy from moisture over the ocean, and the changes when the hurricane wades ashore. Mother Nature treated the hurricane researchers to a rare light show near the end of the most ambitious hurricane study campaign in the Atlantic Ocean. Rarely seen lightning fields, called purple jets, were detected near the eye of hurricane Georges by the ER-2 pilot as he flew more than 19.8 km (65,000 ft) above the island of Hispaniola.

1998 Science@NASA stories NASA gives Georges two last looks ER-2 makes an extra flight for CAMEX. Last of the CAMEX flights; includes complete flight log. Sept. 28, 1998. Quite a Windfall: Hurricane team completes the first half of unique science campaign. Story reviews CAMEX-3 science and activities. Includes "quicklook" science images and pictures of aircraft and spacecraft used. Aug. 31, 1998. NASA, NOAA team seeks secret of hurricane's power Convection and Moisture Experiment-3. Aug. 12, 1998. CAMEX-3 home page at the NASA Global Hydrology and Climate Center.

Islands in the air stream

As the first chills of autumn erased the memories of the summer's heat wave, three cities were starting to apply lessons from sweltering portraits painted by the Urban Heat Island Pilot Project (UHIPP). The basic concept behind UHIPP can be felt on a hot day when you drive from city canyons to wooded areas: it gets cooler. Plants, and trees in particular, evaporate large amounts of water from their leaves. Asphalt, concrete, and other manmade materials are very effective at absorbing light and reradiating it as infrared radiation that raises the temperature of the air.

Right: The cool American River flows past a hot rail yard in Sacramento.

UHIPP coordinated observations by ground teams with airborne and satellite sensors and cameras of Baton Rouge, La., (May 18); Sacramento, Calif., (June 29); and Salt Lake City, (July 13 and Aug. 15). Several U.S. cities participated through ground-based and satellite observations. Teaming with Marshall were the U.S. Environmental Protection Agency, the U.S. Department of Energy, and several city, municipal, and non-profit organizations.

Starting in November, NASA and the EPA worked with the pilot cities to apply lessons from UHIPP, including how to categorize land use, and select areas of maximum potential for reflective surfaces and urban reforestation. Salt Lake City is using the early results to help plan sites for the 2002 Winter Olympic Games and develop strategies to reduce ground-level ozone concentrations in the Salt Lake City valley. In Sacramento and Baton Rouge, city planners and tree planting organizations are using the study to focus their tree-planting programs.

1998 Science@NASA stories Cities getting ready for next heat wave. Results applied from Urban Heat Island Pilot Project. Nov. 20, 1998. Blue Skies Ahead: Hot Ways to Cool Down Our Cities in the Nov. 23, 1998, issue of Newsweek. Salt Lake City shows hot and cold spots. July 21, 1998. Baton Rouge shines with urban heat. May 19, 1998. Sacramento glows with urban heat. July 1, 1998.

FIRE and Ice

The Advanced Microwave Precipitation Radiometer (AMPR) supported the field phase of the First ISCCP Regional Experiment (FIRE) Arctic Cloud Experiment (ACE), May 18-June 6. AMPR was developed by NASA/Marshall and has been employed in a number of airborne atmospheric studies. Its deployment on 11 flights by the NASA ER-2 for FIRE-ACE provided an opportunity to explore new methods for deriving cloud properties from both satellite and airborne passive microwave measurements.

Right: AMPR shows clouds around Point Barrow, Alaska, in different microwave "colors.".

The absence (or presence) of Arctic clouds has dramatic effects on the surface albedo, absorption of solar radiation, energy input into the ocean, and amount of sea ice at high latitudes. Current climate model results are regarded with skepticism due to deficiencies in simulating the surface energy budget, the mass of the sea ice, and the formation, maintenance, and dissipation of Arctic clouds. FIRE-ACE is focusing on improving current climate model simulations of the Arctic climate, especially with respect to clouds and their effects on the surface energy budget.

1998 Science@NASA stories FIRE/ACE is covered in the June 19 issue of the GHCC Newsletter.

Lightning likes land

That lightning likes land more than water is one of the early discoveries from NASA's Lightning Imaging Sensor (LIS). It's not just that most lightning occurs over land. From December 1997 through January 1998, LIS saw that 90 percent of lightning was over land, a significant finding. The increased lightning activity over land is primarily due to convection being much stronger over land. This results in greater ice production and, consequently, more lightning. LIS also is providing a very good database to examine the characteristics of tropical cyclone lightning activity. LIS images of Hurricane Bonnie revealed unusual lightning activity in the eye wall. This may be associated with intensity changes. During an Oct. 18 TRMM overpass, hurricanes Lester and Madeline, then just off the west coast of Mexico, were both producing eye wall lightning.

Right: The colored spot shows lightning in a hurricane off Mexico's west coast.

During an ER-2 research flight of Hurricane Georges while it was passing over Hispaniola, the ER-2 pilot reported frequent lightning, apparently originating in the hurricane eyewall. These observations, in addition to the earlier LIS observations of lightning in Tropical Cyclone Susan and Super Typhoon Paka, raise other interesting questions such as whether the tropical cyclone lightning varies by ocean basin, time of day, stage of development, inner core vs. outer band, and intracloud vs cloud-to-ground activity. GHCC researchers also developed and tested an advanced electro-optic lightning detector technology. The sensor successfully detects lightning electric field changes over a large dynamic range. It was deployed and tested on four summer storms.

1998 Science@NASA stories Lightning likes land. NASA's lightning sensor confirms striking pattern in images taken from space. May 19, 1998. Lightning Detectors watch storms that spawned tornadoes. Lightning sensors in space and on the ground are showing the value of having a space-based network of sensors that could spot and track storms which are likely to spawn tornadoes. April 2, 1998. Lightning Imaging Sensor launched. NASA/Marshall sensor to illuminate link to weather, climate. Nov. 28, 1998.

Last updated Nov. 25, 1998