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Exploring Earth from Space:
Oceans
Dr. David Adamec, NASA/GSFC
National Air and Space Museum
September 14, 2000
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| Thank you
Marshall. Hasn't this been great? I've seen these visuals before and I
still am wowed when I see them. I'm going to speak to you about the third
piece of the climate puzzle, the oceans. Why are the oceans important
to the earth's climate system? The answer is because of their enormous
capacity to store heat. How much heat? The oceans on average are about
2 and a half miles deep, but there is as much heat in the upper six feet
of the ocean as there is in the entire atmosphere! With this incredibly
large storage capacity, it's no wonder that the oceans are the memory
of the earth's climate system. |
View Movie: [0.6 MB QuickTime] [3.3 MB MPEG-1] |
| You're looking
at a representation of the global ocean with sea surface temperatures
indicated by color and sea surface height by the bumps you see on the
globe. I'll explain why sea surface height is so important later. As we
move in time through spring 1997 we see a warm patch of water develop
off the west coast of South America. This is El
Niño, and as many of you are aware, it has an enormous impact on global
weather. You can easily begin to guess why it might as that area in red
is huge, actually covering as big an area as the continental United States.
That warm water heats a large area of the atmosphere and disrupts the
weather globally. On the other side of the globe, and not as well publicized,
the Indian Ocean was seeing the warmest temperatures it had seen in over
40 years. It is the moisture and heat provided by these warm sea surface
temperatures off the east coast of Africa that was responsible for the
torrential rains and floods experienced then. As we continue around the
globe we come to the Atlantic Ocean. |
View Movie: [2.1 MB QuickTime] [11.5 MB MPEG-1] |
| Now
when I see the Atlantic ocean, I think of the Gulf Stream. The Gulf Stream is the
Willie Mays of ocean currents. Its waters move at the break neck speed of almost 5
miles per hour. That's really moving in the ocean. We're
going to look at the Gulf Stream through one of NASA's new sensors, MODIS,
which is on the first EOS platform. I'd like you to notice the unprecedented
detail we are now able to see at systems like the Gulf Stream. The Gulf
Stream meanders its way through the North Atlantic shedding pools of warm
and cold water along the way. We call these pools eddies, and they are analogous
to the low and high pressure systems you see in the atmosphere. These are
the ocean's storms. You can see how the Gulf Stream narrows as it gives
up heat to the atmosphere as it moves on its northeastward path. Some of
the water is still warm as it reaches the other side of the ocean - warm
enough to heat the atmosphere so that you find palm trees on the west coast
of Ireland. |
View Movie: [1.5 MB QuickTime] [7.9 MB MPEG-1] |
| The
MODIS instrument not only looks at temperature structures, it also has the
ability to look at ocean color. What makes the color of the water so interesting?
Depending on how much life there is in the water, the color of the water
changes and this can be viewed from space. That life indicated by the ocean
color represents the lowest rung of the food chain. In this sequence, we're
viewing the color of the Pacific Ocean from another NASA instrument run
out of Goddard called SeaWiFS. Higher concentrations of biology are indicated
by the light green colors. The change over the equator you see is the recovery
from the 1997 El Niño. We're going to zoom in on the Galapagos and watch
a two week transition from almost no life in the water to a hundred fold
increase in life in the water once the El Niño ended. The lack of life and
that lowest part of the food chain in the ocean during El Niño resulted
in a 100% mortality rate for the juvenile bird and marine mammal population
in the equatorial Pacific. El Niño affects more than people. That change
over two weeks is incredible isn't it? |
View Movie: [1.0 MB QuickTime] [6.5 MB MPEG-1] |
| I've mentioned
El Niño more than once and we're going to see a rather unique view of
the 1997 event as viewed from different sensors that measure temperature,
the wind, and sea surface height. Sea surface height is important because
it is a measure of how much heat is stored in the water. Water expands
when it's heated, and this causes the height of the ocean to change. The
last El Niño was so strong that the sea surface height changed by about
two feet off the coast off South America, due to water expansion. You
can see how the height gets elevated when the water warms, but now we're
gong to add the atmospheric response, the winds. Look how the wind is
quickly drawn to the warm water. This is what changes the global weather.
We've essentially put a barrier into the normal atmospheric flow. Disrupting
that flow. This barrier, remember as big as the United States is large
enough to affect the weather patterns around the globe. Another analogy
I like to use is throwing a rock in a pond. There's a big splash where
you throw in the rock, but lots of ripples elsewhere. That blue patch
of water you see at the end of this animation is the La Nina that lasted
for two years and just ended this past spring. La Nina also affects global
weather patterns. It is also a barrier, except the winds are pushed away
from the cold water of La Nina as opposed to being drawn in as happens
during an El Niño. |
View Movie: [1.8 MB QuickTime] [12.0 MB MPEG-1] |
| Over the
past 25 minutes, we've shown you a number of views of our planet in a
way many of you have probably never seen before. How does NASA and Goddard
bring this menagerie of information that is gathered from space together?
How can this information be used to help you? NASA is a technology agency
as well as a space agency. Goddard has always been able to maintain itself
at the forefront of computer technology. Three years ago, NASA dedicated
what was then the fifth most powerful computer in the world to the NASA
Seasonal to Interannual Prediction Project, NSIPP for short. NSIPP endeavours
to take the data from various space sensors and ingest that information
into a computer model of the earth's climate system in order to predict
short term changes in the climate system, events such as El Niño. The
computer model includes where we live, the land, the environment that
for the most part we live in, the atmosphere, and the memory of the climate
system, the ocean. Let's take a look at what a model forecast looks like. |
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| This one
year ocean forecast out to June 2001 is shown quickly because, the ocean,
our memory here, reacts more slowly than other parts of the climate system.
You'll note the warm temperatures in the tropical Pacific at the end of
this forecast. Yes, that's an El Niño predicted by this model. By the
way, that time bar changes color on September 14th. Now I don't want you
leaving here with the idea that there's an El Niño coming next year. This model,
and every other model in the world, does not have the skill to make skillful
forecasts that far into the future. So why do I show you this forecast
if there's no skill? Well, we might get lucky and maybe the forecast is
good. But, more importantly this forecast demonstrates that the model
is taking into account processes that are capable of generating realistic
El Niños. There's hope, the model can do it, we just have to work now
to make it skillful. Let's take a look at more of the model's forecast. |
View Movie: [0.3 MB QuickTime] [1.6 MB MPEG-1] |
| You
are now looking at the same forecast, but with the added variability of
the water vapor in the atmosphere and the soil moisture in the land. There
are deficiencies with the model that we're working to correct,but there's
a lot right with this model too. For example, I would challenge anybody
to be able to distinguish the variations in the water vapor, represented
by the mist on this visualization, from the time lapse satellite water vapor
loops you sometimes see on television weather broadcasts. Those phantom-like
fingers you see are the storm fronts, the day-to-day weather. The soil moisture
can not be emphasized enough in this forecast. Wet conditions are indicated
by green and dryer conditions by brown in this visual. There is currently
no global network for soil moisture observations, and only sparse observations
over the United States. Yet, soil moisture is so important for our agriculture,
and as we've seen this past summer, for wild fire potential. It is a crucial
part of the climate system that needs to be better understood. You can see
how closely tied the soil moisture is tied to the water vapor variations
in the atmosphere. |
View Movie: [1.9 MB QuickTime] [10.8 MB MPEG-1] |
| The model
is global, but let's zoom in on North America and replay the visual. You
can see how dry the west is at the start of this forecast. You can also
watch the southern tier of the United States eventually recover from dry
conditions as this particular scenario evolves. One thing I like to watch
during this view is the storms during winter consistently hitting the
northwest United States, and then the El Niño appears and the storms move
further south and start slamming into the California coast. Also watch
for the southeast to get particularly moist as often happens during an
El Niño. |
View Movie: [2.0 MB QuickTime] [10.8 MB MPEG-1] |
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Before I
pass the podium back to Dr. Asrar, I wanted to make a few closing remarks.
Is this model perfect? Certainly not. Is it useful? Well sure, even if
only to start to understand how events like El Niño occur. Will it get
better? You bet it will! NASA has just begun its series of new satellites
comprising the Earth Observing System. The unprecedented resolution and
types of data that will be available make it an incredibly exciting time
for the people who are involved or just interested in earth science. There
is one thing I can forecast with some degree of certainty. If you like
what you've seen tonight, you ain't seen nothing yet.
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View Movie: [0.6 MB QuickTime] [3.3 MB MPEG-1] |
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Go Back to the Introduction
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