Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Coastal Cities Turn Up the Heat on Rainfall


The old song, asking rain to "go away" and "come again another day," may get even older for people who live in large coastal cities, according to new NASA-funded research.

According to the study, urban heat islands, created from pavement and buildings in big coastal cities like Houston, cause warm air to rise and interact with sea breezes to create heavier and more frequent rainfall in and downwind of the cities. Analysis of Houston-area rain-gauge data, both prior to and since urbanization, also suggests there have been observed increases in rainfall as more heat islands were created.

The Houston-area study used data from the world’s only space-based rain radar on NASA’s Tropical Rainfall Measuring Mission (TRMM) satellite, and dense clusters of rain gauges.

Authors, J. Marshall Shepherd of NASA’s Goddard Space Flight Center, Greenbelt, Md., and Steve Burian, a University of Arkansas, Fayetteville, Ark. researcher, believe the impact large coastal cities have on weather, and possibly climate, will become increasingly important as more people move into urban areas, with even greater concentrations in coastal zones. The paper is in the current American Meteorological Society and American Geophysical Union’s journal, Earth Interactions.

A recent United Nations report estimates 60 percent of Earth’s population will live in cities by 2025. Previous related studies have shown urban heat islands create heavier rainfall in and downwind of cities like Atlanta, St. Louis and Chicago. However, this is one of the first studies to provide evidence of such an effect around a U.S. coastal city. It is also the first to incorporate specific satellite-derived rainfall data for a coastal urban area.

Urban areas with high concentrations of buildings, roads and other artificial surfaces retain heat, which leads to warmer surrounding temperatures and creates heat islands. Rising warm air, promoted by the increased heat, may help produce clouds that result in more rainfall around cities. Buildings of different heights cause winds to converge, driving them upward, helping form clouds. The study shows the urban heat island/rain effect may be even more pronounced near coasts. In coastal cities like Houston, sea breezes also create rising air and clouds. The combination of urban converging winds and coastal sea breezes may enhance thunderstorm development.

"Recent publications have shown evidence of increased lightning activity over and downwind of Houston," Shepherd said. "Since lightning and rainfall are so closely related, we decided to use TRMM’s Precipitation Radar, and a network of rain gauges, to see if urban-induced abnormal rainfall existed," he said.

Using data from 1998 to 2002, the researchers found mean rainfall rates, during the warm season, were 44 percent greater downwind of Houston than upwind, even though the regions share the same climate. They also found rainfall rates were 29 percent greater over the city than upwind. Rainfall rates indicate how hard it rains and can be an indicator of enhanced thunderstorm activity.

To rule out any effects from the coastline curvature near Houston on thunderstorm development, the researchers divided the entire Texas coast into seven zones extending 100 kilometers (62 miles) inland and including four or five major inlets or bays. Analysis of rainfall data in these zones showed abnormal rainfall only occurred over and downwind of Houston, which suggested effects from the urban landscape were significant. At the coastlines, TRMM satellite data were important, because they allowed researchers to assess rainfall data in areas where there were no gauges and records, like over the ocean.

A companion paper by the researchers, presented in March at a Geological Society of America meeting in Kansas City, Mo., stated urban areas also affect the timing of rainfall. Compared to upwind areas, there were nearly two times as many occurrences of rainfall from noon to midnight in the urban area. This finding has significant implications for flood control in Houston, Burian said.

NASA’s Earth Science Enterprise, which supported this study, is dedicated to understanding the Earth as an integrated system and applying Earth System Science to improve prediction of climate, weather and natural hazards using the unique vantage point of space.

Krishna Ramanujan | GSFC
Further information:

More articles from Earth Sciences:

nachricht Gas hydrate research: Advanced knowledge and new technologies
23.03.2018 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ

nachricht New technologies and computing power to help strengthen population data
22.03.2018 | University of Southampton

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Space observation with radar to secure Germany's space infrastructure

Satellites in near-Earth orbit are at risk due to the steady increase in space debris. But their mission in the areas of telecommunications, navigation or weather forecasts is essential for society. Fraunhofer FHR therefore develops radar-based systems which allow the detection, tracking and cataloging of even the smallest particles of debris. Satellite operators who have access to our data are in a better position to plan evasive maneuvers and prevent destructive collisions. From April, 25-29 2018, Fraunhofer FHR and its partners will exhibit the complementary radar systems TIRA and GESTRA as well as the latest radar techniques for space observation across three stands at the ILA Berlin.

The "traffic situation" in space is very tense: the Earth is currently being orbited not only by countless satellites but also by a large volume of space...

Im Focus: Researchers Discover New Anti-Cancer Protein

An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.

The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...

Im Focus: Researchers at Fraunhofer monitor re-entry of Chinese space station Tiangong-1

In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.

Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...

Im Focus: Alliance „OLED Licht Forum“ – Key partner for OLED lighting solutions

Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.

They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...

Im Focus: Mars' oceans formed early, possibly aided by massive volcanic eruptions

Oceans formed before Tharsis and evolved together, shaping climate history of Mars

A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

New solar solutions for sustainable buildings and cities

23.03.2018 | Event News

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

Latest News

For graphite pellets, just add elbow grease

23.03.2018 | Materials Sciences

Unique communication strategy discovered in stem cell pathway controlling plant growth

23.03.2018 | Agricultural and Forestry Science

Sharpening the X-ray view of the nanocosm

23.03.2018 | Physics and Astronomy

Science & Research
Overview of more VideoLinks >>>