Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Are cities changing local and global climates?


Satellite Images of Houston Metro Area

These images show the Houston metropolitan area, where buildings, roads and other built surfaces create urban heat islands that can affect local rain patterns. The images were taken by ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer), an imaging instrument that is flying on Terra, a satellite launched in December 1999 as part of NASA’s Earth Observing System (EOS). Credit: NASA/J

Higher Rainfall Rates Downwind of Texas Cities

This image shows areas where urban heat islands influenced higher rainfall rates (in blue) downwind of major cities connected by Interstate 35, known as the I-35 corridor in Texas. The winds that carried clouds and rainfall downwind (in this case, south and east of urban areas) occurred roughly 3.0 kilometers (1.9 miles) above the surface. Rainfall was measured by the precipitation radar instrument on NASA’s Tropical Rainfall Measuring Mission (TRMM) satellite. The higher rainfall rates depicted here were derived from measurements of mean monthly rainfall during the warm seasons (May through September) from 1998 through 2000. Credit: Jim Williams, Scientific Visualization Studio, NASA/Goddard Space Flight Center

New evidence from satellites, models, and ground observations reveal urban areas, with all their asphalt, buildings, and aerosols, are impacting local and possibly global climate processes. This is according to some of the world’s top scientists convening in a special session at the Fall Meeting of the American Geophysical Union in San Francisco.

To study urban impact on local rainfall, Dr. J. Marshall Shepherd of NASA’s Goddard Space Flight Center, Greenbelt, Md., and Steve Burian of the University of Utah, Salt Lake City, used the world’s first space-based rain radar, aboard the Tropical Rainfall Measuring Mission (TRMM) satellite, and dense rain gauge networks on land to determine there are higher rainfall rates during the summer months downwind of large cities like Houston and Atlanta. Burian and Shepherd offer new evidence that rainfall patterns and daily precipitation trends have changed in regions downwind of Houston from a period of pre-urban growth, 1940 to 1958, to a post-urban growth period, 1984 to 1999.

Cities tend to be one to 10 degrees Fahrenheit (0.56 to 5.6 degrees Celsius) warmer than surrounding suburbs and rural areas. Warming from urban heat islands, the varied heights of urban structures that alter winds, and interactions with sea breezes are believed to be the primary causes for the findings in a coastal city like Houston.

In related work, Dr. Daniel Rosenfeld, an atmospheric scientist at Hebrew University, Jerusalem, reveals the increased amount of aerosols, tiny air particles, added by human activity to those naturally occurring also alter local rainfall rates around cities. Rosenfeld suggests the particles provide many surfaces upon which water can collect, preventing droplets from condensing into larger drops and slowing conversion of cloud water into precipitation. In summer, rain and thunder increases downwind of big cities, as rising air from urban heat islands combines with ’delayed’ rainfall resulting from the presence of aerosols, creating bigger clouds and heavier rain.

To help scientists like Shepherd and Rosenfeld improve understanding of links between city landscapes and climate processes like rainfall, NASA’s suite of Earth observing satellites provides information about the land cover/land use properties that initiate the urban effects. The satellites also track the aerosols, clouds, water vapor, and temperature that describe atmospheric conditions in urban environments. Their measurements allow scientists to make end-to-end studies of urban impacts on the climate system practically anywhere on Earth.

"The space-borne instruments on Terra, Aqua, TRMM, and Landsat provide a wealth of new observations of aerosol particles near and downwind of cities, the cloud optical properties, and surface reflectance characteristics that can help us understand the effects that urban environments have on our atmosphere and precipitation patterns," said Dr. Michael King, NASA Earth Observing System Senior Project Scientist. "Aura, to be launched in 2004, will add even more data," he said.

With growing evidence of the effects of urbanization on climate, climate modelers, like Georgia Institute of Technology’s Dr. Robert Dickinson, hope to account for the cumulative effects of urban areas on regional and global climate models. For example, since asphalt has such a large effect on local heat transfer, water run-off, and how winds behave, characterizing asphalt cover is probably the biggest urban effect to be factored into global models.

NASA’s Earth Science Enterprise 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.

Shepherd, King, Rosenfeld, and Dickinson will present their findings during a press conference on Thursday, December 11, 2003, at 3 p.m., PST in Room 2012, Moscone West, at the 2003 Fall Meeting of the American Geophysical Union in San Francisco.

They also will convene a special session, organized by Shepherd and Dr. Menglin Jin of the University of Maryland, detailing these results on Human-Induced Climate Variations Linked to Urbanization: From Observations to Modeling, sessions U51A and U51C, starting on Friday morning, December 12, at 2:00 p.m. PST at MCC 3001-3003. B-roll of video is available on this topic, by calling Wade Sisler of NASA-TV at 301/286-6256.

Krishna Ramanujan | GSFC
Further information:

More articles from Ecology, The Environment and Conservation:

nachricht Dispersal of Fish Eggs by Water Birds – Just a Myth?
19.02.2018 | Universität Basel

nachricht Removing fossil fuel subsidies will not reduce CO2 emissions as much as hoped
08.02.2018 | International Institute for Applied Systems Analysis (IIASA)

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

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

Im Focus: Tiny implants for cells are functional in vivo

For the first time, an interdisciplinary team from the University of Basel has succeeded in integrating artificial organelles into the cells of live zebrafish embryos. This innovative approach using artificial organelles as cellular implants offers new potential in treating a range of diseases, as the authors report in an article published in Nature Communications.

In the cells of higher organisms, organelles such as the nucleus or mitochondria perform a range of complex functions necessary for life. In the networks of...

Im Focus: Locomotion control with photopigments

Researchers from Göttingen University discover additional function of opsins

Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...

Im Focus: Surveying the Arctic: Tracking down carbon particles

Researchers embark on aerial campaign over Northeast Greenland

On 15 March, the AWI research aeroplane Polar 5 will depart for Greenland. Concentrating on the furthest northeast region of the island, an international team...

Im Focus: Unique Insights into the Antarctic Ice Shelf System

Data collected on ocean-ice interactions in the little-researched regions of the far south

The world’s second-largest ice shelf was the destination for a Polarstern expedition that ended in Punta Arenas, Chile on 14th March 2018. Oceanographers from...

Im Focus: ILA 2018: Laser alternative to hexavalent chromium coating

At the 2018 ILA Berlin Air Show from April 25–29, the Fraunhofer Institute for Laser Technology ILT is showcasing extreme high-speed Laser Material Deposition (EHLA): A video documents how for metal components that are highly loaded, EHLA has already proved itself as an alternative to hard chrome plating, which is now allowed only under special conditions.

When the EU restricted the use of hexavalent chromium compounds to special applications requiring authorization, the move prompted a rethink in the surface...

All Focus news of the innovation-report >>>



Industry & Economy
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

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

Latest News

A new kind of quantum bits in two dimensions

19.03.2018 | Physics and Astronomy

Scientists have a new way to gauge the growth of nanowires

19.03.2018 | Materials Sciences

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Science & Research
Overview of more VideoLinks >>>