Featured Research

from universities, journals, and other organizations

How Hurricanes Are Born Off The African Coast

Date:
September 18, 2006
Source:
NASA/Goddard Space Flight Center
Summary:
The NASA African Monsoon Multidisciplinary Analyses (NAMMA) mission is a field research investigation where scientists are investigating how hurricanes are born off the African coast. It has been taking place in the Cape Verde Islands, 350 miles off the coast of Senegal in west Africa, in August and through mid-September, 2006.

Flying Around a Tropical Disturbance: This is an image from Google Earth that shows the flight path (red line) of NASA's DC-8 aircraft around a tropical disturbance (in red and blue) near the Cape Verde Islands, off the African coast. This was the flight path for August 23, 2006.
Credit: NASA

The NASA African Monsoon Multidisciplinary Analyses (NAMMA) mission is a field research investigation where scientists are investigating how hurricanes are born off the African coast. It has been taking place in the Cape Verde Islands, 350 miles off the coast of Senegal in west Africa, in August and through mid-September, 2006.

Scientists are using airplanes, sensors, radar, computer modeling programs and NASA satellites to better understand hurricanes. Some of the NASA satellites include Aqua, the Tropical Rainfall Measuring Mission (TRMM), and the recently-launched Cloudsat/CALIPSO satellite. Edward Zipser of the University of Utah, Salt City, is the chief mission scientist. Following is an on-location report from Dr. Zipser during the NAMMA Hurricane field mission.

Mission Scientist Report: August 23rd, 2006 - 3rd Science Flight

On August 23, 2006, scientists on the NAMMA mission took an eight hour flight into a tropical disturbance. Edward Zipser noted "surprisingly strong winds at 700 millibars (approximately 10,000 feet high), considering how the system seemed to be struggling to survive in the midst of the Sahara Air Layer."

Spotting Dry Air in a Storm

The Saharan Air Layer (SAL) is a mass of very dry, dusty air which forms over the Sahara Desert during the late spring, summer, and early fall and usually moves out over the tropical Atlantic Ocean. The SAL usually extends between 5,000-20,000 feet in the atmosphere and is associated with large amounts of mineral dust, dry air and strong winds (~25-55 mph).

Zipser said, "We saw evidence of dry air, typically from 750-550 millibars (10,000 to 19,000 feet), on almost all quadrants, but of course we won’t know right away how much of this air actually entered the inner core of the storm."

Communicating Between the Ground and Air

During the previous two flights into the tropical system, the scientists used a communications system called "X-Chat" system. The main advantage was that mission scientist, Jeff Halverson, who was on the ground, watched movie loops of the tropical system and he was able to pass information to the DC-8 aircraft, while the flight scientist could rapidly relay information back.

The scientists on the DC-8 aircraft noted that the storm structure they were flying over featured was not symmetrical (not identical on both sides of a central line) below about 6-7 kilometers (around 4 miles) altitude. They also noted that the system's strongest winds were on the east and north side.

Another benefit to flying into a storm was that the scientists were able to better determine its exact location. The storm was found to be north of the forecast position. Zipser and his crew dropped about 24 dropsondes into the storm. A dropsonde is a sensor that measures temperature, pressure, moisture and winds throughout different locations of a storm.

Looking at Air Circulations Like a Layer Cake

When the scientists flew into the tropical cyclone, they noticed that there were two different air circulations happening, like layers of a cake. In the top layer, higher than the surface, (above 500-400 millibars or 20,000 feet), the center of the cyclone seemed to be well southeast of the cyclone that was on lower level (at the surface).

When the scientists flew over the “eye” or center of the tropical cyclone at a height of 35,000 feet, they we were continuously in thick cirrus clouds (wispy clouds made of ice crystals). Later, however, they were able to look at data from the PR-2 (an airborne radar) showing a sloping eyewall to 7 kilometers (4.3 miles).

Convection (rising air that condenses higher in the atmosphere to form clouds and storms) decreased during the flight with little or no significant turbulence and no large areas of organized rainfall from stratiform clouds (layered clouds).

Measuring the Winds Above and on the Surface

The dropsondes were not spaced closely enough to give a proper description of the wind circulation close to the center of the storm, so the plane carrying Zipser and his crew descended to 10,000 feet (700 millibars) where they mapped the winds on the north and east sides of the storm. Winds were about 40 to 50 nautical miles per hour (45-55 mph), and there were some winds in excess of 60 knots (70 mph). There were no strong winds on the south side of the storm. The scientists estimated the winds on the surface around 40-45 knots (45-51 mph).

Every flight into a storm gives scientists more information about how tropical cyclones work. The NAMMA mission ends in mid-September, 2006.


Story Source:

The above story is based on materials provided by NASA/Goddard Space Flight Center. Note: Materials may be edited for content and length.


Cite This Page:

NASA/Goddard Space Flight Center. "How Hurricanes Are Born Off The African Coast." ScienceDaily. ScienceDaily, 18 September 2006. <www.sciencedaily.com/releases/2006/09/060911120525.htm>.
NASA/Goddard Space Flight Center. (2006, September 18). How Hurricanes Are Born Off The African Coast. ScienceDaily. Retrieved July 25, 2014 from www.sciencedaily.com/releases/2006/09/060911120525.htm
NASA/Goddard Space Flight Center. "How Hurricanes Are Born Off The African Coast." ScienceDaily. www.sciencedaily.com/releases/2006/09/060911120525.htm (accessed July 25, 2014).

Share This




More Earth & Climate News

Friday, July 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Virginia Governor Tours Tornado Aftermath

Virginia Governor Tours Tornado Aftermath

AP (July 25, 2014) Virginia Gov. Terry McAuliffe toured the Cherrystone Family Camping and RV Resort on the Chesapeake Bay today, a day after it was hit by a tornado. The storm claimed two lives and injured dozens of others. (July 25) Video provided by AP
Powered by NewsLook.com
Europe's Highest Train Turns 80 in French Pyrenees

Europe's Highest Train Turns 80 in French Pyrenees

AFP (July 25, 2014) Europe's highest train, the little train of Artouste in the French Pyrenees, celebrates its 80th birthday. Duration: 01:05 Video provided by AFP
Powered by NewsLook.com
Goma Cheese Brings Whiff of New Hope to DRC

Goma Cheese Brings Whiff of New Hope to DRC

Reuters - Business Video Online (July 24, 2014) The eastern region of the Democratic Republic of Congo, mainly known for conflict and instability, is an unlikely place for the production of fine cheese. But a farm in the village of Masisi, in North Kivu is slowly transforming perceptions of the area. Known simply as Goma cheese, the Congolese version of Dutch gouda has gained popularity through out the region. Ciara Sutton reports. Video provided by Reuters
Powered by NewsLook.com
Bill Gates: Health, Agriculture Key to Africa's Development

Bill Gates: Health, Agriculture Key to Africa's Development

AFP (July 24, 2014) Health and agriculture development are key if African countries are to overcome poverty and grow, US software billionaire Bill Gates said Thursday, as he received an honourary degree in Ethiopia. Duration: 00:36 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins