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| Welcoming Dr. Vasquez |
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Item 2 09-MAR-1998 12:39 Lynn Whitley (lwhitley)
Hello,
I'm Lynn Whitley from USC Sea Grant, and I have the honor of introducing Dr. Jorge Vasquez from the Jet Propulsion Laboratory. In addition to being an expert in his field, Dr. Vasquez also has experience in speaking at teacher workshops. I was at one of the workshops that he participated in, and can say from first hand experience that it was an excellent and enjoyable presentation. For our workshop this week, Dr. Vasquez will be presenting information on the history of El Nino, satellite observations, and impacts. Welcome, Dr. Vasquez!
Hello! I am Phyllis Grifman, Associate Director of the Sea Grant Program at the University of Southern California. It is my pleasure and privilege this morning to welcome you all to the Main Hall and to introduce our first keynote speaker, Dr. Jorge Vasquez.
Jorge was born in Cuba and immigrated, with his parents and brother, to the
United States in 1961. He grew up in West Virginia with the mountains,
but long walks with his father during summer vacations in Miami
instilled a love of the oceans.
Jorge graduated with a Bachelor's degree in Physics from the University of Miami
and went on to study oceanography at the University of Rhode Island's Graduate School of Oceanography. From there he went to JPL and began research on using satellite
information to detect sea level and sea surface temperature changes in the world's oceans. His specific area of interest was the Gulf Stream.
While working at JPL he finished his PHD at USC in Geological Sciences.
Today his research interests include how sea surface temperature and
sea level are coupled in the different ocean basins.
Please join me in welcoming Jorge. I look forward to "meeting" all of you and to an interesting and exciting month studying El Nino.
History of El Nino
During the 1700s Peruvian Fishermen noticed that every December
the waters off of the coast would get very warm. They associated this
event with the coming of the Christ Child. Interesting enough they associated
it with something good, namely the Christ Child. How did something that
happened every December turn into an event that happens every 3-5 years
and is generally associated with negative climatic changes around the
world.? The Peruvian fisherman were not far off from the true story.
The waters do get warm every December. The part they missed was that
every 3-5 years the waters became warmer than usual.
During the 1960s and 1970s Professor Klaus Wyrtki at the University of Hawaii
observed that every 3-5 years the waters off Peru became not only warm but
even warmer than usual. He also observed that the warming of the waters
in the Pacific was associated with a change in the Trade Winds.
Normally the Trade Winds blow from West to East piling up water in the
Western Pacific. For reasons that are not fully understood every 3-5 years
these trade winds shut down and actually at times reverse allowing the
warm waters of the Western Pacific to return to the Eastern Pacific. Because
colder waters contain more oxygen and more oxygen means more life the arrival
of the warm waters kills the fisheries off Peru. In the 1970s further work
indicated that these changes in the Trade Winds where part of a much larger
change in the coupled ocean-atmosphere system known as the El Nino Southern
Oscillation or ENSO. Bascially what they found was that changes were occuring
worldwide not just in a small area off Peru. The area of convection (vertical
movement of air that creates clouds, rains) in the Pacific moved from West
to East. Where does this leave us today?
There exists today a vast network of buoys in the Tropical Pacific that is
used to observe El Nino. This network is known as the TOGA-TAO array and
monitors changes in the temperature of the Tropical pacific that usually
means an El Nino is coming. However because we now know the effects are global
dramatic changes in the understanding of El Nino have resulted from Satellite
Technology. There are primarly two classes of satellites used to study the
world's oceans. One of them is known as a passive sensor because it basically
measures the radiation that is emitted by the ocean. The other is known
as an active sensor because it emits a radar pulse and from the return
signal to satellite we get information on the condition of the ocean surface.
Because one sends a signal and one does not the term active and passive are
used.
To measure the temperature of the sea surface an instrument known as
the Advanced Very High Resolution Radiometer is used. This instruments
measures the infrared energy emitted from the ocean surface and after
calibrating the signal one can convert it to sea surface temperature, a
parameter critical to observing El Nino. The other parameter that is critical
to observing El Nino is sea level. This parameter is measured by an instrument
known as an altimeter. The Advanced Very High Resolution Radiometer is a passive
instrument while the altimeter is an active instrument. because it sends a radarpulse to the ocean surface and measures the time it takes to return to the
satellite.
This travel time is then converted to a measurement of the sea level. This
conversion is not trivial. Both these instrument have played a curcial role in
observing and forecasting the recent El Nino.
What impact has the observation of El Nino had locally and worldwide?
In California we have basically seen winter storms that have been
fueled by the warm waters of the Pacific bring larger than usual
rain amounts to the Southland. This had been great for the ski industry
but not so for individuals whose houses were effected by mudslides, etc.
Recently I received a note from friends in Ethiopia. In their email
they talked about the starvation, homelessness and desease that has
been brought about by the recent El Nino condition. In Africa such
conditions are usually associated with drought conditions. Perhaps
someday in the not too distant future such observations of El Nino
will allow us to mitigate the potential devastation and economic
impact.
EEROR IN KEYNOTE: I mistakenly said the Trades blow
normally from West to East. They normally blow from East
to West. During an El Nino event they reverse and can
blow from West to East.
The following images are a time sequence of Sea Surface Temperature Anomaly in the Pacific Ocean from December of
1996 to December of 1997. The definition of the anomaly is the
difference between the actual sea surface temperature for that time of year and the normal sea surface temperature. White indicates waters that are warmer than usual by 3-5 degrees Celsius. Notice the warming of the waters in
the Tropical Pacific during 1997. These images came directly from the Advanced Very High Resolution Radiometer.
The following images are from the TOPEX/Poseidon altimeter which measures the level of the sea surface. The way to interpret these images is the same as with sea surface temperature. The images shows the difference between sea level for that date and
the normal conditions for that time of year. Notice how during the El Nino year sea level is much higher than usual in the Eastern Pacific. Notice the similarities between sea surface temperature and sea level. This
is partially due to warmer waters expanding, thus there should
be a relationship between sea surface temperature and sea level. However notice also the differences which indicate the situation is more complicated than this because of the ocean currents and circulation.
The following two images show the two satellites from which
sea surface temperature and sea level are measured. It is important to remember that in measuring the sea surface temperature and sea level errors are involved due to different
atmospheric conditions. For example for the AVHRR satellite water vapor and aerosols attenuate the infrared energy being released by the ocean surface. Thus what is received at the satellite might not be a true estimate of what the sea surface
is emitting. In the case of the altimeter water vapor in the atmosphere increases the density of the atmosphere and thus the travel time (the time it takes the radar pulse to go from the satellite to the ocean surface and back again) decreases. This
shows how complicated the measurement of sea surface temperature and sea level can be and that models are needed to accurately represent the influences of such things as water vapor and aerosols.
Jorge,
All these images are great! Really help to illustrate what is going on.
I wondered if the reversed trade winds (going from West to East) help elevate the water level in the Eastern Pacific. Or is it just the sea water temperature that does it?
This is great! I was wondering how much do you rely on your passive satellites verses the buoy array. Also, what type of instrumentation was on the satalites that documented the 82-83 event.
Rick Baker, Orange County Marine Institute.
Thanks Jorge'
How can you tell from these images where it all starts? where do the first signs of change occur?
In response to Kristina Bishop's question
Your question is very good and I have to admit once again
one of the things that is not fully understood. What we
do know is that when the Trades (East to West) die down
the warm water piled up in the Western Pacific can return
to the Eastern Pacific. Think of a wave tank. Say you have a fan
blowing the water from one end of the wave tank to the other.
That water will pile up at the one end and stay piled up
until you turn off the fan. Of course if you have two fans
and turn the other one on as you turn one off (the two fans
are at opposite ends of the wave tank) the water will return
quicker. This is a very simple example and things in real
life are never that simple. One reason is that in the Ocean
you have what we call a thermocline that separates warm
water at the top from colder water at greater depths. Thus
in a very simple way the Ocean is like a two layer system,
unlike a wave tank where you probably only have one layer at
the same temperature. But the example illustrates in a basic
way how the ocean surface in a closed basin is reacting to
a wind stress.
I will pass on to you some URL's which illustrate the winds,
etc.
In response to Rick Baker's question
All the questions today are great!
One of the things we use the buoy data for is to calibrate
the satellite data. The main advantage in the satellite data
is that once it is calibrated it gives us a global view of what
is going on, not just in the Equatorial Pacific. That allowed
NOAA this year to put out the warning of El Nino. Remember this
event in reality was not forecasted but observed. I am sure Professor
O'Brien will have more to say on this, but none of the models
got the magnitude of the current El Nino right. If one can't
predict the magnitude it becomes very difficult to predict
the consequences. During the 82-83 event we had buoys in the Tropical Pacific. However as you remember during
the 82-83 event the observation of the event was not made until
it was well developed. With satellites for the first time we
have been able to see it developing overtime. This is
predominately because of the global view the satellite gives
us.
I also wanted to add that the AVHRR satellite was functional
in 1982-1983 but the quality of the data made it difficult
to observe the event. The models developed since then have
improved the quality of the data tremendously and allowed us
to observe El Nino. The TOPEX/Poseidon altimeter has played
a major role in observing the event.
In response to Peter's question:
From the sea surface temperature one can see how the waters
in the Tropical Pacific begin to get warmer during the middle
to late of 1997. The same thing can pretty much be observed
in the sea level data. One of the great mysteries of all this
is what causes the Trade Winds to shut down and the event
to begin. Basically it is very much a Chicken and Egg argument.
Does the ocean spin up the atmosphere or does the atmosphere
cause changes in the ocean.
Let me see if I can find some of the earlier sea level images.
The following are some homepages people might be interested
in. You can also see more images showing the time development
of the El Nino event.
http://podaac-www.jpl.nasa.gov/el_nino
http://podaac-www.jpl.nasa.gov/
The following shows how El Nino effects Southern California
and other areas. As you can see most of this is based
on statistics and not theory. That is something is correlated
with something. In Southern California El NIno is correlated
with more rain.
Enjoy
http://podaac-www.jpl.nasa.gov/sue/el_nino.html
Some recommendations if you are time limited.
Look at the JPL el nino page (you can get to it from
the http://podaac-www.jpl.nasa.gov/el_nino link.It
has a complete set of images showing the development
of El NIno. Also
look at the PMEL (http://www.pmel.noaa.gov/toga-tao/el-nino/home.html) homepage and you can see some data from
the TOGA-TAO array in the Equatorial Pacific.
Any questions let me know. If anyone is interested in more
details about how the satellites function and the measurements
taken let me know.
Dear Jorge,
Does the water that is building up in the eastern Pacific correspond with an equal but opposite effect in the western Pacific?
And a second part to my question, do we know specifically where the extra water comes from; is it an east-west change or does the water come from north or south as well?
This question goes back somewhat to what Kristina asked and
I don't think I answered it very well. There is a time scale
involved in all of this. The reason the water piles up
in the Western Pacific is that normally the trades blow from
east to west. They blow over a long enough period of time allowing the water to pile up or be pushed towards the
Western Pacific. (normally several years) (Think of the fan and the difference if you turn it off an on quickly or whether you
leave it on for a long time). The El Nino event (
time period when winds have died down or reversed) is amall
, on the order of a few months, and is only sufficient for allowing
the water in the Western Pacific to return towards the East.
However (Professor O'brien will talk about this) there is
an equal effect known as La NIna when the waters in the
Eastern pacific are colder than normal. What triggers these
episodes is still a mystery and Professor O'brien might thave
more to say on this. In a sense La Nina is the opposite effect
to El Nino. However remember both effects involve changes from
the normal condition in the Eastern Tropical Pacific. One
results in temperature warmer than normal (El Nino) and the
other temperatures colder than Normal (La Nina).
Also in answer to Tom Nolan's question about whether the water
comes from North and South, we generally believe it is an
East-West effect but there are models which indicate that
the whole thing might be triggered by events away from the
Equatorial Pacific.
Also in answer to Kristina Bishop's question. The images
seem to indicate that there is a good correlation between
sea surface temperature and sea level. This makes sense because
as water heats up it expands. However remember the ocean is
not still. It has currents which carry heat (such as the
Gulf Stream). Thus the ocean circulation also changes things
dramatically from just a simple model of heat expansion.
that is why from the images you can tell that sea level and
sea surface temperature are not in a one-one correspondence.
I noticed that there are quite a few educators taking part
in the workshop. In case people are interested at JPL we
have produced one TOPEX informational CDROM and are currently
in the process of producing a second educational CDROM. For
more information on ordering, etc. contact Susan Digby
at podaac@podaac.jpl.nasa.gov. I am sure Dr. Chambers next
week will speak a lot more about altimetry and how it
was used to detect El Nino.
Hello Jorge,
This is a great presentation and outstanding graphics! I had a question about the "active" satellite measurements. You mentioned that data received from the altimeter can tell us about the conditions of the ocean surface, besides sea level, what other kinds of information does it give us about the ocean surface and does any of that information correlate to El Nino conditions?
Jorge, I've really enjoyed your presentation, and it has highlighted for me something very important about the predictive capacity of the technology we now have available. Looking at all the El Nino "hype" we've suffered through for months before there was even a hint of rain, it seems to me that the availability of data has been a very important factor in the public's awareness of what science can do. Comparing this El Nino with the 1982-83 event, we can see how advances in satellite telemetry and data analysis, AND the availability of the data on the WWW etc. has greatly contributed to our knowledge and to the media's interest in covering it.
And now, I have a couple of questions. One of the things I've read several times is that El Nino has no relation to the the greenhouse effect, global warming and sea level rise. But just this morning, one of the faculty in the Biology Department here asked me whether or not they were related. Another set of things I've read says that although El Nino is a fairly normal cyclical phenomenon, there may be indications that the cycle itself is changing -- from a 7 to 10 year cycle to one that occurs as often as 4-5 years. Can you (or can anyone) shed any light there?
In response to the questions by Lynn and Phyllis-The
questions are so good. You guys are so intuitive because
they are the same questions being asked by many scientist
in the field.
In relation to your question Lynn, there are more parameters
that can be measured by the TOPEX altimeter. Briefly the
TOPEX altimeter sends a radar pulse to the surface of the
ocean and it bounces back to the satellite. Thus the only
thing the satellite knows is how long it took that radar pulse
to return and what we call the strength or scatter of
the pulse at its return. Remember when the radar (microwave)
pulse hits the ocean surface it is going to get scattered.
The amount of scatter depends on the state of the ocean
(waves, etc). Thus by knowing the scatter of the return
pulse to the satellite one can indirectly measure the
wave height. In reality this is more complicated than it
sounds. Also because the state of the ocean (big waves-
turbulent sea, small waves-calm sea) is related to the
wind speed we can also indirectly measure the wind speed.
However a more sophisticated satellite such as NSCAT
(NASA scatterometer) is needed to get the direction of the wind.
another parameter that one can measure is the amount of
water vapor but this involves another instrument besides
the altimeter. The three primary measurements we can get from
an altimeter are sea height, sea state (wave height) and
wind speed. The wind speed is affected by El Nino because
the Trades weaken during an El Nino, but wave height is
usually associated with more local phenomena such as storms
hurricanes, etc. Nonetheless there might be a correlation
because the wind speed is also related to wave height.
It can get pretty complicated.
Let me see if I can dig up some images to illustrate some
of this.
In answer to Phyllis's question (also refer to Dr. Tom
Chambers response to a similar question in the OPEN CIRCLE
discussion)-There is no conclusive evidence (despite the
politics) about how El Nino might be tied in with global Warming.
greenhouse effect, etc. One of the great things about
satellite data is that for the first time we are starting to
have a long enough time record to look at some of these questions, but I want to stress we are only beginning to be
able to look at these issues.
The last two El Nino's have been out of the ordinary. The
93-93 event was small compared to the 82-83 event but
lasted a long time. It also appears that the latest El Nino
is lasting a long time. the problem lies in how one defines
an El Nino event. Remember the orignal Peruvian fisherman
associated it with something that happened every year. Now
we have developed a system of defining El Nino based on
such things as how much warm water there is or how much
the temperature exceeds normal conditions for that time
of year. However these are pretty aribritary and work is
still underway to come up with a good definition of when
El Nino occurs. Obviously this year we have had one. In response
to the 7 to 10 year cycle this issue is still very much
open to debate. Coming to these conclusions is like fitting
a straight line to two data points. One can always do it.
But one needs the third, fourth, etc. data points to really
know what is going on. We are now at the stage where we are
only beginning to have the third and fourth data points.
The Education resource list that is linked on the PO.DAAC page that you recommended,Jorge, is really a good set of resources. They should be helpful to many of the teachers in this group.
I came across a current homepage on El Nino that I think
would interest people. It has animations that show
sea surface temperature, sea level, and winds (from the
NASA scatterometer) in time sequence. It gives a very
good picture of how the three respond to an El Nino
event.
Take a a look at (http://airsea-www.jpl.nasa.gov/ENSO/welcome.html).
Any questions let me know!
-Jorge.
When you go into the homepage click on movies then go to the
last movie (2.1MB). Hopefully things will be fast. If not
I think it is worht the patience to see all three measurements
in sequence and how they are interrelated.
-Jorge.
Thanks Jorge, that is an interesting page. Here is a neat "slideshow" they put together.
Thanks Peter!
Jorge.
A little El Nino humor! Why it is important to separate
fact from fiction.
I like that one! It's a cute and colorful addition to our conversation.
Thanks.
Great visuals and humor. :-)
Do you know of any data such as sandstone band records, treering studies, archaeological evidence, or ethnographic studies that could help point the way to uncovering a more historical interpretation of El Niņo's rhythm?
In response to Stephen,
I don't know of any. I really hope that studies (maybe they
have already begun) will concentrate on local effects (someone
already has pointed this out and I agree completely) of
el Nino. I agree completely that the satellite data is great
but we need to start looking at how things are effected locally.
Some friends I have in Ethiopia have said it has been a devasting
year. We should look seriously to see if droughts in that
part of the world are intensified or caused by el nino.
Looking at geological records, etc. might not be a bad way
of finding out.
One more example. At John's Hopkins they are looking
at how infectious deseases are correlated with sea
surface temperature (deseases such as cholera, etc).
If so is this because of algae blooms, etc. More
attention needs to be paid to these local effects.
There are many interesting fluctuations in the rates of infectious diseases over time that are tied in to changes in climate, other than those just related to water temperature . For instance, after several years of drought, there was a wet winter in California associated with the smaller El Nino in we had in 1993. Shortly after the big increase in rainfall, we stareted seeing a massive increase in "valley fever" an infection caused by a fungus called coccidiomycosis. It turned out that the cocci spores in the soil will stay there dormant for years and years, but only convert to an infectious form after a significant amount of moisture. We hadn't seen much cocci in years during the drought, but as soon as we had enough rain, they all converted at once and there was a massive increase in the disease. It had started to taper off over the last couple of years, but we're interested to see if this winter's rains cause another increase. While we've known about cocci for decades, this association with weather has only been recognized in the last 5 years.
I really hope that more attention is paid to these locak
problems. In my humble opinion we need to fund more efforts
in understanding the coupling between the physics and biology
especially at a local level.
I have to leave for one week but thank you for the wonderful
experience. I am sure Dr. Chambers and Professor O'brien
will have more to say. If I can ever be of assitance in
the future don't hesitate to contact me at:
jv@pacific.jpl.nasa.gov
I will check in again on the 21st.
Dear Jorge,
Thank you very much for a stimulating week--you have gotten this workshop off to a good start. Excellent job! We really appreciate the time you spent with all of us. Hope you will check back in here next week.
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