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January 16, 2004
From Neighborhoods to Globe, NASA Looks At Land
Satellites and computers are getting so
good, that now they can help study human activity
on scales as local as ones own neighborhood, and
may answer questions concerning how local
conditions affect global processes, like water
and energy cycles.
NASA’s Land Information System (LIS)
uses computer models to predict impacts that
cities and other local land surfaces might have
on regional and global land and atmospheric
processes. Dr. Christa Peters-Lidard,
Co-Principal Investigator and Project Manager for
LIS, at NASA’s Goddard Space Flight Center
(GSFC) in Greenbelt, Md., gave a presentation on
LIS this week at the annual meeting of the
American Meteorological Society in Seattle.
Until recently, scientists could not model
detailed, local interactions between land and
atmosphere on the global scale because satellites
did not provide a close enough view of Earth, and
computers were too limited. But with cheaper
high-performance computers, and with satellite
technologies like the Moderate Resolution Imaging
Spectroradiometer (MODIS) instrument on the Terra
and Aqua satellites, scientists are working to
predict energy and water cycles for the entire
globe at a scale of 1 kilometer (km) (.6 miles).
That means computer models can now supply
information about processes that occur locally,
like within neighborhoods where people live, for
example. The global LIS has been implemented at 5
km (3.1 miles) resolution and will be implemented
at 1 km resolution in February, 2004.
“Now we can apply all these resources to
understand and predict how humans impact their
local water and energy cycles and ultimately
their weather and climate,” said
Peters-Lidard.
As a case study implementing one simple aspect
of what LIS can do, Peters-Lidard, colleague Paul
Houser of NASA GSFC, and others used a model to
predict summertime temperatures in Houston for
August 22, 2002. The model found temperatures
were 1 to 2 degrees Celsius (1.8 to 3.6 degrees
Fahrenheit) warmer than surrounding non-urban
areas on that day. While this example offers an
illustration of the model, predictions like this
may be made over days, months, and years, for
temperatures, amounts of moisture in soils, water
runoff and drainage, snowpack amounts, energy
fluxes, and much more.
In the demonstration, the model predicted for
the same day that the Houston urban surface
temperature was approximately 0.5 to 1 degree C
warmer (0.9 to 1.8 degrees F) throughout the
night and as much as 3 degrees C warmer (5
degrees F) around midday. Prior NASA studies have
shown that built-on surfaces with few trees
absorb heat and create urban heat islands, which
in turn create updrafts of warm air, leading to
more rain around and downwind of cities like
Houston and Atlanta.
The LIS case study offers an example of the
future of climate-related computer models, where
models will incorporate the land-atmosphere
processes created by local land surfaces. By
including local energy and water cycles in
computer models, people will be able to apply
predictions to climate and weather, agricultural
forecasting, water resource management, hazard
mitigation and more.
The LIS uses several land surface models,
which are typically run on computers capable of
billions of calculations per second. These models
contain precipitation and radiation observations,
near-real time meteorological information, and
data on topography and soils. They also make use
of 1 km MODIS Leaf Area Index (LAI), which
measures plant density and growth, and assigns a
quantifiable value to the amount of vegetation on
the ground.
MODIS LAI measurements show, that on average
between 2001 and 2002, leaf area in some areas
within Houston decreased, likely associated with
development in the metropolitan area. Non-urban
areas to the northwest and west of the city show
higher LAI values compared to the 2001-2002
average, indicating more vegetation.
LIS may also allow scientists to possibly
mitigate heat islands by running “what
if” scenarios, like testing how
temperatures change when hypothetical trees are
planted.
The project has been supported by NASA’s
Earth Science Technology Office Computational
Technologies Project. 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.
Applications of the LIS are countless. For
example, the U.S. Bureau of Reclamation plans to
use the LIS to help determine snowpack, amounts
of soil moisture, and the loss of water into the
atmosphere from plants and the soil, a process
known as evapotranspiration. Understanding these
variables in the water cycle is a key to managing
water in such resource-limited areas.
For more information and images:
http://www.gsfc.nasa.gov/topstory/2004/ 0113landair.html
Contact:
Krishna Ramanujan
Goddard Space Flight Center, Greenbelt, Md.
Phone: 607/273-2561
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Houston Metro Area
The Houston metro area, with case study area in
red. Credit: NASA/Land Information Systems
Average Difference in Leaf Area Index
for Houston Metro Area between 2001 and
2002
This 5 kilometer resolution image of the
Houston area shows the differences in Leaf Area
Index (LAI) as an average for August between 2001
and 2002. MODIS LAI measurements show, that on
average for August between 2001 and 2002, leaf
area in some areas within Houston decreased,
likely associated with development in the
metropolitan area. Non-urban areas to the
northwest and west of the city show higher LAI
values compared to the 2001-2002 average,
indicating more vegetation. This slide
underscores the importance of using current LAI
data (rather than climatological, as is standard)
in models like LIS. Credit: NASA/Land Information
Systems
Houston Area Temperatures, August 22,
2002
Surface temperature on August 22, 2002 at 20:00
Greenwich Mean Time (GMT) for the Houston area as
predicted by the Land Information System (LIS).
As shown, the temperatures in the Houston area
are 1-2 degrees Kelvin (K) (1.8-3.6 F) warmer
than the surrounding areas. The black areas are
lakes or water bodies, which are not currently
modeled by the Land Information System. Credit:
Credit: NASA/Land Information Systems
Temperature Comparison Between Houston
Urban and Outlying Non-Urban Areas, August 22,
2002
Surface temperatures predicted by the Land
Information System for August 22, 2002. The blue
curve depicts the Houston urban area, while the
green curve depicts the surrounding non-urban
area. As shown, the urban surface temperature is
approximately 0.5-1 degree K (0.9-1.8 F) warmer
throughout the night and up to 3 degrees K (5.4
F) warmer around midday. Credit: NASA/Land
Information Systems
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