January 12, 2000
These findings by researchers at Florida State University, Tallahassee, FL, were presented today at the annual American Meteorological Society's (AMS) meeting in Long Beach, CA, and will be featured in an upcoming edition of the Journal of Climate.
In addition, researchers found that using the rainfall data collected from defense meteorological satellites and TRMM can be used to increase the forecast accuracy even further. Their method examines the behavior of a number of different forecast models and selects those properties from each model that lead to the true rainfall as observed by the TRMM satellite. These model properties are then used to predict the rainfall for three days into the future, with remarkable success.
"Including rainfall into the multi-forecast model, or 'superensemble' model, is a unique approach," said Prof. T.N. Krishnamurti, the paper's lead author and a TRMM scientist at Florida State University. "Overall we're most interested in improving the rainfall three-day forecast accuracy. Our research has shown that the accuracy of global and regional forecasts using the superensemble is higher with TRMM research data."
These forecast results are based on five experiments each conducted Aug. 1 to Aug. 5, 1998. The forecast accuracy was higher over all tropical regions. Scientists attribute this success to a combination of improved analyses available from the superensemble approach as well as the availability of accurate rainfall estimates over the tropics from the TRMM satellite.
For years, scientists have attempted to improve the short- term forecasts in the tropics, but only minor improvements were made. Now, with the research data from the NASA spacecraft, scientists will more accurately forecast rainfall in the region. This is particularly important when it comes to hurricane tracks and rainfall accumulations. Experimental forecasts made by this new technique during the 1999 hurricane season, for example, correctly forecast the track of major hurricanes such as Dennis and Floyd.
Scientists have a keen interest in how potential changes in the global climate might affect the associated rainfall patterns as they in turn affect human activities. "Making such improvements in even the short-term forecasts is important because it demonstrates that we are learning more about the behavior of rainfall within these models," said Chris Kummerow, the spacecraft project scientist at Goddard Space Flight Center, Greenbelt, MD. "Understanding rainfall patterns generated by our global climate models is an extremely difficult problem. Having additional information available from these weather forecast models has the obvious benefit of better short term forecasts, and may help shed additional light upon the climate models."
TRMM is NASA's first mission dedicated to observing and understanding tropical rainfall and how it affects the global climate. The TRMM spacecraft fills an enormous void in the ability to calculate worldwide precipitation because ground-based radars that measure precipitation cover so little of the planet. Ground-based radars cover only 2 percent of the area covered by TRMM, said Kummerow.
TRMM has produced continuous data since December 1997. Tropical rainfall, which falls between 35 degrees north latitude and 35 degrees south latitude, comprises more than two-thirds of the rainfall on Earth. Previous estimates of tropical precipitation were usually made on the basis of weather models and occasional inclusion of very sparse surface rain gauges and/or relatively few measurements from satellite sensors. The TRMM satellite allows these measurements to be made in a focused manner.
TRMM, a NASA-Japanese mission, is part of NASA's Earth Science Enterprise, a long-term research program designed to study the Earth's land, oceans, air, ice and life as a total system.
Information and images from the TRMM mission are available on the Internet at http://trmm.gsfc.nasa.gov
Information on the AMS is available at
NASA Headquarters, Washington, DC
Goddard Space Flight Center, Greenbelt, MD
American Geophysical Union, Washington, DC
Oct. 5, 1999
The study shows that the "warm rain" processes that often create rain in tropical clouds are practically shut off when the clouds are polluted with heavy smoke from forest fires. In these clouds, scientists found, the cloud tops must grow considerably above the freezing level (16,000 feet) in order for them to start producing rain by an alternative mechanism.
"We've seen evidence of decreased precipitation in clouds contaminated by smoke, but it wasn't until now that we had direct evidence showing that smoke actually suppresses precipitation completely from certain clouds," said Dr. Daniel Rosenfeld, the paper's author and a TRMM scientist at the Institute of Earth Sciences, Hebrew University of Jerusalem.
Scientists have a keen interest in how changes in global precipitation affect human activities, such as crop production, and the global rainfall weather pattern. More precise information about rainfall and its variability is crucial to understanding the global climate and predicting climate change.
In his paper, Rosenfeld highlights one specific area: Kalimantan, Indonesia. During the satellite's overpass on March 1, 1998, the southeastern portion of the island was engulfed in smoke, while the northwestern portion was relatively smoke free. The spacecraft's radar detected precipitation in smoke-free clouds, but almost none in the smoke-plagued clouds, showing the impact of smoke from fires on precipitation over the rainforest.
"It's important to note that this is not a unique case," said Rosenfeld. "We observed and documented several other cases that showed similar behavior. In some instances even less severe smoke concentration was found to have comparable impacts on clouds."
This research further validates earlier studies on urban air pollution showing that pollution in Manila, the Philippines, has an effect similar to forest fires, according to Rosenfeld.
"Findings such as these are making the first inroads into the difficult problem of understanding humanity's impacts on global precipitation," said Dr. Christian Kummerow, TRMM project scientist at NASA's Goddard Space Flight Center, Greenbelt, MD.
Raindrops in the atmosphere grow by two means. In the first, called the "warm rain" process, a few cloud drops get large enough to start falling. As they fall, they pick up other cloud drops until they become big enough to fall to Earth as raindrops.
The second process requires ice particles and water colder than 32 degrees Fahrenheit. Ice particles surrounded by this "supercooled" water may grow extremely rapidly as water freezes onto the ice core. As these large ice particles fall, they eventually melt and become raindrops.
Scientists have known for some time that smoke from burning vegetation suppresses rainfall, but did not know to what extent until now. Thanks to TRMM observations, scientists are able to see both precipitation and cloud droplets over large areas, including clouds in and out of smoke plumes.
TRMM has produced continuous data since December 1997. Tropical rainfall, which falls between 35 degrees north latitude and 35 degrees south latitude, comprises more than two-thirds of the rainfall on Earth.
TRMM is a U.S.-Japanese mission and part of NASA's Earth Science Enterprise, a long-term research program designed to study the Earth's land, oceans, air, ice and life as a total system. Information and images from the TRMM mission are available on the Internet at URL:
NASA Headquarters, Washington, DC
Goddard Space Flight Center, Greenbelt, MD
November 24, 1998
TRMM is a joint U.S.-Japanese mission that was launched on Nov. 27, 1997, from the National Space Development Agency at Japan's Tanegashima Space Center. The TRMM satellite has produced continuous data since Dec. 8, 1997. Tropical rainfall -- that which falls within 35 degrees north and 35 degrees south of the equator -- comprises more than two-thirds of the rainfall on Earth. Changes in wind patterns generated by these tropical systems spread across the globe to impact weather patterns everywhere.
Launched to provide a validation for poorly known rainfall datasets generated by global climate models, TRMM has demonstrated its utility by reducing uncertainties in global rainfall measurements by a factor of two -- from approximately 50 percent to 25 percent. While pleased with the results to date, "there is clearly an aspect of tropical rainfall which does not fit our conceptual models," said Dr. Christian Kummerow, TRMM project scientist at NASA's Goddard Space Flight Center, Greenbelt, MD.
"At the moment, all fingers are pointing at the possibility that raindrops are significantly smaller than we used to believe. Looking 'under the hood,' of clouds with radars and radiometers has given us a unique perspective on the rain and ice processes. As soon as we make sense of all these new and sometimes contradictory observations, a whole new improved way of viewing and modeling rainfall processes should emerge. These particle sizes have the potential effect of regulating the amount of water vapor and ice being pumped into the upper atmosphere, which plays a key role in global climate change studies," added Kummerow.
"The cloud types and area coverage generated by the rainfall process can directly alter the heat balance of the atmosphere," said Arthur Hou, deputy TRMM project scientist at Goddard. "The combined view of this process from all the TRMM sensors is offering an unprecedented insight here." Observations of cloud droplets near the cloud tops of thunderstorms have also yielded surprises. "The darker appearance of raining clouds and the unexpected suppression of rain in polluted atmospheres might be explained by the presence or absence of large raindrops near the cloud top," said Danny Rosenfeld, an Israeli scientist who is a member of the TRMM science team.
Scientists long have theorized that convection, or heat transfer, is different over land than over the ocean. TRMM's sensors provided direct observational evidence that faster and stronger convective updrafts over land are contributing to the formation of "taller" continental storms with more lightning. This is in contrast to the almost complete absence of lightning over the world's tropical oceans.
One unexpected phenomenon observed by TRMM was the massive tall chimney clouds in Hurricane Bonnie. While monitoring the progress of one of this year's most dramatic hurricanes, NASA researchers obtained compelling images of Hurricane Bonnie showing a (cumulonimbus) storm cloud, towering like a sky scraper, 59,000 feet into the sky from the storm's eyewall. This new view of "hot towers" in hurricanes could help forecasters predict hurricane intensity earlier, and identify those storms that will proceed to a stronger category.
Last July, TRMM shed new light on the phenomenon known as La Niņa. TRMM research team members successfully retrieved sea- surface temperature data from the TRMM Microwave Imager (TMI) instrument aboard the spacecraft. This temperature data, obtained by the TMI, gives scientists the ability to obtain observations even in cloudy conditions. The coincidence of having both an El Niņo and a La Niņa event is giving scientists a rare opportunity to study the evolution of these events and the transition from one to another.
La Niņa is essentially the opposite of the El Niņo phenomenon and is characterized by unusually cold ocean temperatures in the eastern equatorial Pacific. An El Niņo occurs when ocean temperatures are warmer than normal. La Niņa and El Niņo often are spoken of together and termed the El Niņo/Southern Oscillations, or "ENSO." La Niņa sometimes is referred to as the cold phase of the ENSO. An unexpected benefit from TRMM has been the almost immediate impact the data have had in improving the understanding of atmospheric water and energy cycle in assimilated global data sets. While still early, scientists are very encouraged that this improvement will lead directly to enhanced research efforts as well as better weather forecasts.
TRMM is part of NASA's Earth Science Enterprise, a long-term research program designed to study the Earth's land, oceans, air, ice and life as a total system. Images from the TRMM mission are available on the Internet.
NASA Headquarters, Washington, DC
Goddard Space Flight Center, Greenbelt, MD
May 19, 1998
"We're extremely excited about these new images and the quality and quantity of the data we're receiving. In several instances, the data resolution is much better than we had anticipated," said Dr. Christian Kummerow, TRMM Project Scientist, at NASA's Goddard Space Flight Center, Greenbelt, MD. "Previously, it was not possible to gather radar precipitation data over the oceans and TRMM has changed all that."
TRMM is NASA's first mission dedicated to observing and understanding tropical rainfall, which comprises more than two- thirds of all rainfall, and how it affects the global climate.
Global rainfall is the primary distributor of heat through atmospheric circulation. The recent El Niņo serves as a perfect example of the atmospheric circulation changes that can result from a displacement of the normal precipitation patterns in the central Pacific. More precise information about this rainfall and its variability is crucial to understanding and predicting global climate and climate change.
The Precipitation Radar aboard TRMM is the first rain radar ever launched into space. It measures precipitation distribution over both land and sea areas. Some of the most dramatic Precipitation Radar data was received on March 9 over Melbourne, FL, during the passage of a line of very severe thunderstorms. In comparing the TRMM radar data of the storm with that taken by ground-based radars, the three dimensional TRMM radar showed better vertical resolution of the storm structure. The vertical structure is critical for determining a storm's overall intensity as well as determining the height at which the heat release associated with precipitation is occurring.
Another image released today shows TRMM's radar-derived view of a severe thunderstorm over Houston, TX. The TRMM radar demonstrated significantly better capability to define ambiguities, or occasional "false readings," associated with ground-based radars.
The TRMM spacecraft fills an enormous void in the ability to calculate world-wide precipitation because so little of the planet is covered by ground-based radars. Presently, only two percent of the area covered by TRMM is covered by ground-based radars.
"Since rainfall represents energy conversion, hurricane researchers are eager to use the rainfall data as input to hurricane forecast models," notes Jerry Jarrell, director, National Hurricane Center.
Also aboard TRMM is the Microwave Imager, providing exceptional resolution of storm systems. TRMM's Microwave Imager has better spatial resolution and a new lower frequency channel than previous instruments, according to Kummerow.
An interesting preliminary finding from the Lightning Imaging Sensor (LIS), another instrument on the TRMM satellite, is that its data indicate little lightning over the oceans and 90 percent of lightning occurring over land. Researchers believe that the greater lightning activity over land is primarily due to a larger convection -- or heat -- effect associated with land. This results in greater ice production and, consequently, more lightning. "The beauty of TRMM is that with the Precipitation Radar and the microwave imager, we can test this hypothesis time and again," said LIS Principal Investigator Hugh Christian, at the Global Hydrology and Climate Center at the Marshall Space Flight Center, Huntsville, AL. "TRMM will enable us to gain fundamental insights into the properties of these convective storms and thus better estimate the effects on global weather patterns."
The Clouds and the Earth's Radiant Energy System (CERES) instrument aboard the spacecraft measures how much sunlight the planet's atmosphere, surface and clouds reflect and how much energy it radiates to space from its store of heat energy. "CERES achieved new levels of calibration that we've never reached before in looking at the Earth," said Dr. Bruce Barkstrom, a scientist at NASA Langley Research Center, Hampton, VA, which manages CERES. "Those new levels will help us reduce the uncertainty of how the Earth uses the energy from the Sun to drive the climate system."
By studying rainfall regionally and globally, and the difference in ocean and land-based storms, TRMM is providing scientists the most detailed information to date on the processes of these powerful storms, leading to new insights on how they affect global climate patterns. TRMM's complement of state-of-the- art instruments will provide extremely accurate measurements of the distribution and variability of tropical rain and lightning, and the balance of solar radiation absorbed and reflected by Earth's atmosphere.
Langley Research Center, Hampton, VA
November 26, 1997
New Satellite to be Launched Nov. 27
"The temperature of the Earth is controlled by the global balance between the amount of sunlight absorbed by the Earth, a heat gain, and the amount of energy radiated back to space at thermal infrared wavelengths, a heat loss. Clouds are the largest factor changing this flow of radiation into and out of the Earth," said Dr. Bruce Wielicki, head of the CERES project.
Thin, high clouds can trap heat emitted by the Earth producing warming. Low, thick clouds can reflect the Sun's energy back into space causing cooling. Scientists need to know how different types of clouds trap or reflect energy, and how much and how often they do it, in order to understand what effects clouds may have on our planet's climate.
"Uncertainties about the way clouds change the energy available to heat and cool the Earth is the largest uncertainty in predicting the magnitude of future climate change caused by increasing greenhouse gases," Wielicki said.
"Clouds change greatly from the equator to polar regions, from day to night, and from land to ocean. Fortunately, satellites allow scientists to observe the complete range of cloud types on the Earth, as well as to measure their behavior and role in the climate system," Wielicki said. "A good example of this type of measurement is to observe the changes in clouds and energy flows which occur during El Nino. The fortuitous timing of the [CERES] launch will allow measurements to be taken both during and after the current major El Nino event."
"[CERES] also will improve the accuracy of solar insolation data used for determining the sites of solar power plants, solar cookers in refuge camps, solar refrigerators, etc. This will happen roughly three to four years after launch," Wielicki said.
CERES, part of NASA's Mission to Planet Earth program, is scheduled for launch Nov. 27 at 3:40 p.m. EST aboard the Tropical Rainfall Measuring Mission (TRMM) observatory.
NASA Goddard Space Flight Center
November 18, 1997
Over the next couple days engineers will continue to test and analyze the observatory and the ground support system. The onboard clock serves as "master" clock, synchronizing other onboard clocks. The unit has a backup which can take over its functions, if necessarily.
TRMM is the first Earth science observatory dedicated to studying the properties of tropical and subtropical rainfall. This joint NASA/Japanese Space Program mission will obtain and study multi-year science data sets of tropical and subtropical rainfall measurements to understand how interactions between the sea, air and land masses produce changes in global rainfall and climate. Another important science goal of TRMM is to study how El Niño-related rainfall anomalies correlate with other oceanic and atmospheric processes.
Tropical rainfall comprises more than two-thirds of global rainfall. More precise information about this rainfall and its variability is crucial to understanding and predicting global climate change.
More information on TRMM is available via the Internet.
The TRMM project is part of NASA's Mission to Planet Earth enterprise, a long-term, coordinated research effort to study the total Earth system and the effects of natural and human-induced changes on the global environment. TRMM is managed by Goddard for NASA's Office of Mission to Planet Earth, Washington, D.C.
Marshall Space Flight Center, Huntsville, AL
November 5, 1997
The lightning sensor will help to pave the way for a future space-based lightning mapper that could deliver day and night lightning information to a forecaster's workstation within 30 seconds of occurrence -- providing an invaluable tool for storm "nowcasting" and giving people more advance warning of severe storms.
The Lightning Imaging Sensor was developed by the Global Hydrology and Climate Center at NASA's Marshall Space Flight Center in Huntsville, Ala., with contributions from Lockheed Martin in Palo Alto, Calif., and Kaiser Electro-Optics Inc., in Carlsbad, Calif.
The small, sophisticated instrument will provide information on cloud characteristics, seasonal and yearly variability of thunderstorms, precipitation, the Earth's water cycle, storm dynamics, and the release of latent heat.
This lightning detector is three times more sensitive than its predecessor, the Optical Transient Detector -- a lightning detector launched in April 1995. "Lessons learned from the currently orbiting detector have provided valuable input for the development and future use of the new detector," said Dr. Hugh Christian, the project's principal investigator and Marshall Center scientist.
"The Lightning Imaging Sensor will study both day and night cloud-to- ground, cloud-to-cloud and intra-cloud lightning as well as its distribution around the globe," said Christian.
The lightning detector is a compact combination of optical and electronic elements that includes a unique form of an electronic eye known as a staring imager, capable of locating and detecting lightning within individual storms. The imager's field of view from its low-Earth orbit allows the sensor to observe a point on the Earth or a cloud for 80 seconds. "This allows sufficient time to estimate the flashing rate, and may often be sufficient to indicate whether a storm is growing or decaying," said Christian.
The staring imager is comprised of an expanded optics lens system which provides a wide field of view, and a narrow-band filter which minimizes background light. A device within the imager -- behaving similarly to the retina of the human eye -- creates an image of the lightning and the background scene. After the image is created, a real-time event processor extracts the signal, determining when a lightning flash occurs.
This event processor allows the detection of lightning even in the presence of bright sunlit clouds. Weak lightning signals that occur during the day are hard to detect because of the strong background illumination.
"It is designed to detect 90 percent of all lightning strikes. It records the time of a lightning event, its radiant energy -- how bright the lightning flash is -- and an estimate of the lightning's location," said Christian.
As part of the Tropical Rainfall Measuring Mission, the Lightning Imaging Sensor will contribute to NASA's Mission to Planet Earth program, aimed at gaining a better understanding of how the Earth functions as a system, and how this system is being influenced by the rapid growth of the human population.
The mission is the first Earth science satellite dedicated to studying the properties of tropical and subtropical rainfall. Tropical rainfall -- all rain that falls within the zone 35 degrees above and 35 degrees below the equator -- comprises more than two-thirds of global rainfall. More precise information about this rainfall and its variability is crucial to understanding and predicting global climate change.
The joint NASA and Japanese Space Agency mission is scheduled to be launched on an H-II rocket from the Tanegashima Space Center in Tanegashima, Japan on Nov. 18, at 3:40 p.m. EST (Nov. 19, 5:40 a.m., JST).
NASA Headquarters, Washington, DC
Goddard Space Flight Center, Greenbelt, MD
National Space Development Agency of Japan
September 29, 1997
The launch was originally scheduled for Oct. 31, 1997 (Nov. 1, 1997, in Japan), from the Tanegashima Space Center in Tanegashima, Japan.
The launch delay was caused by a problem with TRMM's companion payload on the H-II Rocket, the Japanese Engineering Test Satellite-VII (ETS-VII). ETS-VII is a Japanese robotics experiment consisting of two satellites (Target and Chaser) that periodically separate and re-dock. During recent systems tests at the launch site, anomalies were observed in the attitude control electronics of the Target satellite, and in a transponder of the Chaser satellite. These items were removed from the satellites and returned to the manufacturer for rework. The launch was postponed to allow time for the repairs.
The first Earth science satellite dedicated to studying the properties of tropical and subtropical rainfall, TRMM carries microwave and visible/infrared sensors, and the first spaceborne rain radar. Tropical rainfall comprises more than two-thirds of global rainfall. More precise information about this rainfall and its variability is crucial to understanding and predicting global climate change.
One of the science goals of TRMM is to study how El Niņo- related rainfall anomalies correlate with other oceanic and atmospheric processes. "Unfortunately, this delay will limit significantly our ability to study the approach of the peak of the current El Niņo condition in the Pacific Ocean," said Dr. Joanne Simpson, NASA project scientist for the Tropical Rainfall Measuring Mission at Goddard Space Flight Center, Greenbelt, MD. "It also will reduce the mission's role in the start of a multifaceted research program in the South China Sea. But, we understand the needs of our important international partner in the TRMM launch, and we will make every effort to get science data flowing as soon as possible."
TRMM still will be able to achieve its primary science objectives. "Despite this delay, we are very excited about the impending launch and look forward to years of climate research with the rainfall and other measurements to be provided by this unique observatory," said Dr. Ramesh Kakar, Program Scientist for TRMM at NASA Headquarters in Washington, DC.
The TRMM launch window opens at 5:40 a.m. JST on Nov. 19, with an approximate two-hour launch window daily until Dec. 10, 1997.
The TRMM project is part of NASA's Mission to Planet Earth enterprise, a long-term, coordinated research effort to study the total Earth system and the effects of natural and human-induced changes on the global environment. TRMM is managed by Goddard for NASA's Office of Mission to Planet Earth, Washington, DC.
NASA Headquarters, Washington, DC
Goddard Space Flight Center, Greenbelt, MD
National Space Development Agency of Japan, Tokyo
June 25, 1997
The first Earth science satellite dedicated to studying the properties of tropical and subtropical rainfall, the Tropical Rainfall Measuring Mission (TRMM) carries microwave and visible/infrared sensors, and the first spaceborne rain radar. Tropical rainfall comprises more than two-thirds of global rainfall and is the primary distributor of heat through the circulation of the atmosphere. More precise information about this rainfall and its variability is crucial to understanding and predicting global climate change.
"We're very excited about this major opportunity for cooperation with Japan, which is NASA's largest international partner in Earth science," said William Townsend, Acting Associate Administrator for NASA's Mission to Planet Earth enterprise, Washington, DC. "The Tropical Rainfall Measuring Mission has great potential to improve scientific understanding of climate processes related to the heat released by tropical rainfall. In turn, this knowledge improves the global atmospheric circulation computer models that are used to make weather and climate forecasts."
NASDA will provide the Precipitation Radar for TRMM and an H-II rocket to launch the observatory on a three-year mission from the Tanegashima Space Center in Japan.
"We are very happy to provide the Precipitation Radar for TRMM and launch this first space mission to measure a driving force of the global atmosphere, tropical rainfall. We hope this U.S.-Japan joint mission provides important data for predicting global climate change and weather anomalies," said Dr. Kazuyoshi Yoshimura, Executive Director of NASDA in Tokyo. "We will launch TRMM in November, and hereafter we can launch a rocket in each fall season. This is a good opportunity to expand the cooperation between the U.S. and Japan, and we expect a further cooperation in various fields, such as Earth observation satellites, Earth science, and global change research."
NASA's Goddard Space Flight Center in Greenbelt, MD, fabricated the observatory's structure and support systems, integrated and tested the spacecraft and is providing two science instruments. Two other instruments are being provided by NASAÕs Langley Research Center, Hampton, VA, and its Marshall Space Flight Center, Huntsville, AL.
Goddard also will operate TRMM via NASA's Tracking and Data Relay Satellite System. NASA and NASDA will share responsibility for science data processing and distribution to the global change research community.
Current knowledge of rainfall is limited, especially over the oceans. By flying in a low-altitude orbit of 217 miles (350 kilometers), TRMM's complement of state-of-the-art instruments will provide extremely accurate measurements of the distribution and variability of tropical rain and lightning, and the balance of solar radiation absorbed and reflected by Earth's atmosphere.
Extensive prelaunch testing of TRMM was completed recently and the observatory currently is undergoing final preparations for its shipment to the Japanese launch site in late August.
The TRMM launch window opens at 5:40 a.m. JST on Nov. 1, and with an approximate two-hour launch window daily for a 40- day period. TRMM's companion payload on the H-II rocket will be Engineering Test Satellite-7, a Japanese robotics experiment.
The TRMM project is part of NASA's Mission to Planet Earth enterprise, a long-term, coordinated research effort to study the total Earth system and the effects of natural and human- induced changes on the global environment. TRMM is managed by Goddard for NASA's Office of Mission to Planet Earth, Washington, DC.