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 worlds only space-based rain radar on NASAs Tropical Rainfall Measuring Mission (TRMM) satellite, and dense clusters of rain gauges.
Authors, J. Marshall Shepherd of NASAs 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 Unions journal, Earth Interactions.
A recent United Nations report estimates 60 percent of Earths 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 TRMMs 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.
NASAs 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
GPM sees deadly tornadic storms moving through US Southeast
01.12.2016 | NASA/Goddard Space Flight Center
Cyclic change within magma reservoirs significantly affects the explosivity of volcanic eruptions
30.11.2016 | Johannes Gutenberg-Universität Mainz
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
02.12.2016 | Medical Engineering
02.12.2016 | Agricultural and Forestry Science
02.12.2016 | Physics and Astronomy