| |
College Classroom
|
       |
|
You are El Nino Administrator. |
| Question of the Week: Week 1 |
|
Item 7 13-MAR-1998 18:48 Kristina (Tina) Bishop (tina)
We had listed in the course requirements that each week a reflective question should be answered by those taking the workshop for credit.
This is the first week's reflective question for you to post your thoughts about your learning thus far.
What has been the most interesting or surprising information you have gained from this workshop about how scientists study El Nino and how they know when it will occur?
The most impressive thing about how scientists study El Nino is the availability of global data and the use of modern technology. From the days of the direct and local observations by the Peruvian fisherman, scientists are now able to compare past and present El Ninos and are able to predict future ones.
Do you think we can get to see a drawing of the TOGA-TAO array in the Tropical Pacific? What shape do these buoys make? Is it like the Y-shaped array of the 27 radio telescopes (VLA) in New Mexico? How far down into the water do these thermometers go that are on the buoys? Perhaps the scientists don't use mercury or alcohol thermometers at all. Just how do these sensing devices work?
The most interesting thing I learned about the satellites and other instruments was the classification term of passive and active. A passive sensor simply measures the radiation given off by the oceans. The active sensor sends out a radar pulse and waits for a return signal. An altimeter is considered an active instrument because it also sends out a radar pulse and waits for a return signal. In this case, the time it takes to return to the altimeter will be interpreted as a measurement of sea level.
I understand that scientists must have the data on sea temperature, sea height, wave height, and wind speed in order to predict future El Ninos because the Trade Winds weaken during an El Nino and the sea level is much higher than usual in the Eastern Pacific. It must be a difficult job to keep track of the normal effects of global wind and ocean current patterns and to separate these out from the ones caused by El Nino and the ones caused by local weather conditions.
A statement was made in response number 2:14 about the altimeter. Prof. Vasquez said that the water vapor will increase the density of the atmosphere and will cause the travel time to decrease. In our basic weather unit, I have taught my students that an increase in water vapor or relative humidity means that there is a decrease in air pressure because water vapor is lighter than the nitrogen and oxygen molecules they pushed out. Doesn't low pressure correspond to low density and not high density of the atmosphere? If the density does increase, shouldn't the travel time of the radar pulse increase or get longer? In any case, without the help of the AVHRR satellites and other instruments, it would be impossible for the scientists to study and predict the future occurrence of El Nino.
The most impressive thing about how scientists study El Nino is the availability of global data and the use of modern technology. From the days of the direct and local observations by the Peruvian fisherman, scientists are now able to compare past and present El Ninos and are able to predict future ones.
Do you think we can get to see a drawing of the TOGA-TAO array in the Tropical Pacific? What shape do these buoys make? Is it like the Y-shaped array of the 27 radio telescopes (VLA) in New Mexico? How far down into the water do these thermometers go that are on the buoys? Perhaps the scientists don't use mercury or alcohol thermometers at all. Just how do these sensing devices work?
The most interesting thing I learned about the satellites and other instruments was the classification term of passive and active. A passive sensor simply measures the radiation given off by the oceans. The active sensor sends out a radar pulse and waits for a return signal. An altimeter is considered an active instrument because it also sends out a radar pulse and waits for a return signal. In this case, the time it takes to return to the altimeter will be interpreted as a measurement of sea level.
I understand that scientists must have the data on sea temperature, sea height, wave height, and wind speed in order to predict future El Ninos because the Trade Winds weaken during an El Nino and the sea level is much higher than usual in the Eastern Pacific. It must be a difficult job to keep track of the normal effects of global wind and ocean current patterns and to separate these out from the ones caused by El Nino and the ones caused by local weather conditions.
A statement was made in response number 2:14 about the altimeter. Prof. Vasquez said that the water vapor will increase the density of the atmosphere and will cause the travel time to decrease. In our basic weather unit, I have taught my students that an increase in water vapor or relative humidity means that there is a decrease in air pressure because water vapor is lighter than the nitrogen and oxygen molecules they pushed out. Doesn't low pressure correspond to low density and not high density of the atmosphere? If the density does increase, shouldn't the travel time of the radar pulse increase or get longer? In any case, without the help of the AVHRR satellites and other instruments, it would be impossible for the scientists to study and predict the future occurrence of El Nino.
In our Datastreme tour the meterologist was explaining how the hurricans increase in the Pacific/California coast and decrease in the Atlantic. She also indicated how the movement from the Pacific storms can swing up the coast and bring the Plains lots of moisture. Usually we get the Gulf of Mexico moisture. During an El Nino does this mean double trouble? Will there be more extremes in temp. as the "Farmers Alamanac" has a dry summer predicted? Has there been any indication of an increase of the surface water temp in the Pacific in the last 20 years as our climate seems to be changing? The agriculture is changing due to the change in growing seasons. Are there more earthquakes/volcanic eruptions during this El Nino? Are there other means of recording the temp., winds, wave height and sea height begin developed?
Thanks for your responses Hellen and Charlene! Your questions will need to be answered by one of the scientists; maybe by Jorge after he returns next week.
The most intersring and surprising information I gained from the workshop was that the scientists can actually get a for-warning that the El Nino can be begining. The 70 TAO Array buoys in the Tropical Pacific monitor changes in the ocean temperature. This change from the normal temperatures can indicate that an El Nino Event is beginning.
I had read in the newspapers that scientists thought we might have an El Nino Event, but the press seemed to be trying to scare people rather than to explain the sequence of how an El Nino begins. I am not sure that we know all but from what I have learned I believe the sequence is as follows:
(Please let me know if I am wrong...I am learning.)
1. TAO Array in Tropical Pacific detects changes from the normal sea temperature.(an annomally)
2. Satellites with the AVHRR measure IR emmitted from the Ocean and an annomally is detected. Water temperatures on both sides of the Pacific are shifted from the norm. The Eastern Pacific is warming and the Western Pacific is cooling. The trade winds which normally blow from East to West weaken.
3. Satellites with altimeters measrure the time it takes for a radar pulse to travel from the satellite to the ocean surface and back. An annomally in sea levels is detected. In the Eastern Pacific sea levels are higher and Western Pacific sea levels are lower.
4. The atmosphere is effected...more rain in South America, Mexico and Califronia, less in the countries around the Western Pacific. (This topic has yet to be explained in the workshop.)
I was also surprised to learn that there seems to be about 3 monthes from the SOI to the time of maximum rainfall.
re: http://podaac-www.jpl.nasa.gov/sue/el_nino.html
We folks on land do not think much about El Nino beginning until we are rained upon!! In Sonoma County, Ca. (38 miles north of San Francisco) we had record breaking rainfall, mud slides, and flooding in Feb. of '98. When I saw the satellite maps from Dec. '97 I as wondering, if El Nino was in full effect in the ocean waters why was the weather so nice in Sonoma County?? This web site shed some light on a possible reason.
This does bring another question to mind .."Have the scientists decided upon a definition as to when does El Nino begin??" or "Are we still just in the stages of observing all the events which bring about the changes we have come to call El Nino?? It seems to me we are all are still in process of learning and observing El Nino.
Wow!! Science in Action. What an opportunity for our youth to be encouraged to enter the Sciences as a profession.
Cathleen,
Thanks for sharing your thoughts on your learning. Don't know if there is a precise definition of when El Nino begins. I agree that we are all in the process of learning.
Cathleen,
I think you have a good handle on the observations used to see El Nino evolving. However, I would re-order them somewhat:
1. TAO observations detect changes in temperature at depth.
2. Altimeters detect sea-level changes (equivalent to temperature changes at depth).
3. AVHRR detects surface temperature changes.
4. Weather Changes.
The TAO data and altimeter data would actually see changes at almost the same time if the altimeter processing was not so much more complicated and time consuming. TAO data is received and processed every day. The TOPEX/Poseidon altimeter data has a several week lag as satellite positions are calculated and models to correct for path delay are added.
The SST data sees the anomalous warming last, since it spreads from the deeper levels to the surface.
Dr. Chambers,
Thank-you for responding to my reflective question. I was responding to what I had learned from week one. Now that I have had the oportunity to "attend" your presentation, from week two, I see that you have provided direction and answers to many of my questions. Thank-you for all your efforts and research! Cathleen
As a hopelessly right-brained individual, I find that I
struggle somewhat with the technical jargon, but the
presenters have done an excellent job of rephrasing the
more challenging information to a level understandable by
those of us who may not have a science background. The
images of the phenomenon were classic (I'm a visual learner,
you see). I feel somewhat humble in my background knowledge
of basic scientific principles - for example, that colder
water contains more oxygen than warm water. Having been clued in to that fact, I now have a much better understanding of why the fisheries of the western Americas can be so severely affected.
As a social studies teacher, I'm deeply interested in the
perspectives of people who work on the land, and the
potential for myth-making, religious penance, and so on and
so forth, that the El Nino may create. I've searched the web
for information on the Indian Ocean El Nino, because I'm
interested in the socio-cultural relevance of the monsoons,
especially in India. I found some great stuff, including a
report from Fodor's Travel that claims that travel in India
this spring/summer may be unbearable if the predicted El Nino-caused drought comes about. The writer notes that
"hepatitis, shigella, typhoid, and cholera," as well as
"malaria, dengue and yellow fevers, encephalitis, and plague" are more prevalent during those times when the
monsoon is deflected from the subcontinent. As I mentioned,
they are predicting a less-than-moist monsoon season this
year. It's interesting to note that a cholera outbreak has
recently been identified in Thailand - El Nino-induced
dryness perhaps?
|
