[Narrator] Weather forecasters use them to create the nightly weather report. 
Airline pilots use them to learn how to fly planes. Experts use them in virtually every
industry and discipline. They are computer models. At NASA, 
scientists use computer models to enhance their understanding of the earth, the solar system
and the universe. NASA satellites orbiting the earth
relay immense amounts of data to scientists on the ground, who then enter that data
into computer model simulations. [Cynthia Rosenzweig] We have then, equations and then
computer code which solves those equations on a day-to-day basis.
[Narrator] NASA is the source for most of the research satellite observations of the atmosphere,
land and oceans. [Phil Webster] So the NASA scientists will look at the observational data and
make theoretical projections about what a model might look like and they will build a numerical model
based on the data and then run that on our computers and compare that to reality.
[Narrator] With rapid increases in computer technology, models are becoming 
evermore powerful and sophisticated, allowing us to simulate our complex environment in greater detail.
NASA uses a variety of weather models such as the Goddard Earth Observing System model.
It creates an extraordinarily high resolution, realistic-looking 
image of our atmosphere. These GEOS-5 simulations showcase the model's 
ability to capture fine-scale cloud features worldwide, like the swirling clouds in the Atlantic
Ocean off the coast of North America. 
The goal of weather models is to give the most accurate prediction of weather in the next week to ten days.
In 2005, when Hurricane Katrina formed over the Atlantic Ocean, scientists
wanted to understand the storm. How intense was it, what was its size and structure and what 
would be its final path? NASA satellites continuously monitored many aspects of the storm
from windspeed, rainfall and sea surface temperature to the storm's three-dimensional structure.
To get a more complete picture of the storm and predict its evolution, scientists entered
the data into a computer model. Then, high-powered supercomputers capable of trillions of calculations
per second crunched the numbers. This process is called data assimilation.
Data assimilation is a two-step cycle that repeats itself whenever new data becomes available. 
In the first step, the model runs forward in time to provide an estimate of the atmosphere. In the second
step, this estimate gets corrected using observations. The cycle begins again, each step
building upon the last and accumulating the information from satellite and ground observations.
Weather models are updated every six hours to include the most current observations for the next forecast.
This approach prevents the model from straying too far from reality and acts as a checks-and-balance system
to acheive the most accurate forecast. While weather models predict
conditions for up to ten days, climate models predict trends over much longer periods of time.
[Phil Webster] The climate models that are run at the NCCS are numerical expressions of the
various processes that make up climate. This includes things like land surface, 
water in the ocean and the movement of air in the atmosphere. [Narrator] Just as in weather prediction, 
data assimilation is a way of bringing all the observations of the earth together to provide an analysis of our climate
. One example of this technique is MERRA - the Modern Era Retrospective Analaysis for Research
and Applications. MERRA incorporates data from the entire satellite record.
Over 30 years of data. Its results are a data encyclopedia that can be used for research and
analysis. MERRA can help meteorologists understand the variations associated with specific 
weather events in the past. While MERRA gives us a climate picture across decades, the Goddard Institutde
for Space Studies, or GISS, can extend that view across centuries. GISS models 
have already unraveled average temperature trends over 200 years. New GISS simulations will cover the last
1,000 years to verify model accuracy. They'll also look forward, projecting climate
trends to the end of the 21st century. With each satellite launched, we gain billions of measurements
that tell us more about our planet. Having so much more data will require increases in
computing power to synthesize this information into meaningful representations of the climate system as a whole.
[Phil Webster] At Goddard Space Flight Center, we have a tremendous amount of observational data,
captured by our satellites. We have probably the largest collection of earth scientists
in the world. And we have this new state-of-the-art computing center. So the combination of
the scientists, data and computing puts us in a unique position to enable
advances in weather and climate research.
