CWS 9B

DataStr= eme Atmosphere Current Weather Studies 9B:

¡EL NIÑO!

Do Now:

Print this file.
Print the Wednesday Curre= nt Weather Studies Image 1, Image 2 and Image 3 Files.
When available, answer the two Concept of the Day questions in the Thursday, 5 November 2009 Daily Summary File.

To Complete Investigation:

Read Chapter 9 in the DataStreme Atmosphere textbook and respond to the Chapter Progress Questions in the DataStreme Atmosphere Study Guide Investigations binder. [Do not complete the Questions for Review and Critical Thinking Questions appearing in the = Weather Studies Investigations Manual].
Complete the introductory portion of Investigation 9B in the Weather Studies Investigations Manual, which ends when you reach the statement, "As direc= ted by your course instructor, complete this investigation by either: ---<= /b>." [Do not complete the Applications portion of the Investigation.= ]

Go to the Wednesday - = CWS B (Current Weather Studies B) link on the course website to comple= te this investigation.

Following the intense El Niño episode of 1982-83 with its worldwi= de weather impacts, an instrumented array of buoys (Tropical Atmosphere Ocean (TAO) or TAO/TRITON array) was deployed across the tropical Pacific from ten degrees North latitude to ten degrees South latitude. Figure 1 is a map sho= wing the buoy locations. This array, along with satellite observations, has allo= wed realtime monitoring of tropical Pacific ocean and atmosphere conditions and= input for models used to predict future episodes.

Figure 1.= The locations of TAO-Triton instrumented buoys in the tropical Pacific Ocean. [http://www.p= mel.noaa.gov/tao/proj_over/map_array.html]

6= .      The most recent reporting of TAO surface data is presented in Image 1. The upper panel of Image 1 depicts the five-day mean tropical Pacific sea surface temperatures (SST) and wind conditions ending on November 2, 20= 09, the current situation. The SST are shaded and isothermed at one-half degree intervals and the winds= are shown by arrows. The shading and isotherms indicate that the warmest waters across the tropical Pacific are located from about [(170° E to 170°W)(160° W to 140° = W)(120° W to 100° W)] longitude. [Note, the Pacific east of 180° longitude has W(est) numbered longitudes while the Pacific west of 180° has E(ast) numbers.]

7= .      The winds across the central and eastern tropical Pacific were generally from t= he [(west)(east)].

8= .      The lower panel of Image 1 displays Anomalies, that is, departures from = the long-term average. Positive temperature anomaly isotherms are solid lines, negative anomaly isotherms would be dashed lines. The interval between line= s is one-half degree Celsius. A bold solid line would denote the 0-degree depart= ure (i.e. average). The broad pattern of current SST anomalies shows = [(overall negative)(overall positive= )(negative in the west and positive in the east)(positive in the west and negative in the east)] values over the tropical Pacific region.=

9= .      The magnitude of the greatest positive anomalies is at least [(0.5= )(1.0)(2.0)] Celsius degrees.

1= 0. The anomalous wind directions, i.e. departures from the average, are generally = from the [(west)(east)= ] over the tropical Pacific. For example, an anomalous west wind exists near 120° W, when the actual wind is from the east. This means that the real east wind is less strongly from the east than average.

For contrast and comparison, we will look at TAO data acquired during re= cent significant El Niño and La Niña events. In much of 1997 and e= arly 1998, the tropical Pacific Ocean experie= nced a strong El Niño. Image 2 is a depiction of the average ocean surface temperatures and atmosphe= ric surface winds in the tropics over the month of November as measured by the = TAO array, near the peak of the 1997-98 El Niño epis= ode.

1= 1. The t= op view (November 1997 Means) is the average sea surface temperatures a= nd surface winds for the month of November 1997. The sea surface temperatures (SSTs) across the region ranged from about 26 °C as the "coolest&q= uot; in the southeast corner to about 30 °C as the "warmest" just south of the Equator, west of center in the upper panel. These highest SSTs were located at about [(170° W)(120° W)] Longitude in the tropical Pacific.

1= 2. The w= ind directions in the eastern Pacific were generally from the southeast. In the western Pacific, near the Equator (from about 140° E to 150° W), wi= nds were generally light with some blowing from the west and some from the east. These observed winds and SSTs generally [(were)(were not)] consistent with the dep= iction of the Figure 2 schematic on p. 9B-3 of the Weather Studies Investigatio= ns Manual for an El Niño. (For larger views of these schematics, se= e http://www.pm= el.noaa.gov/tao/elnino/nino_normal.html.)

1= 3. The b= ottom view of Image 2 (November 1997 Anomalies) is a depiction of SST and = wind anomalies, departures of the observed values shown in the top view f= rom the long-term average. (Recall: Positive temperature anomalies are solid li= nes in intervals of one-half degree Celsius. A heavy line labeled 0 shows where no temperature anomaly exists, i.e. conditions are average.) <= /p>
The SST anomalies in the eastern Pacific were positive, with the greatest values being more than [(1.5)(4.5)(7.5)] C°. S= ST anomalies along the equator were virtually all positive or zero. The locati= on and degree of the warm SST anomalies is what defines the El Niño situation.

1= 4. Now e= xamine Image 3. These are the tropical Pacific SST and wind conditions for November 1998, one year later than Image 2, showing that La Niña conditions h= ad replaced El Niño. For November 1998, the sea-surface temperatures al= ong the Equator in the eastern Pacific were near 22 °C, several degrees = [(warmer)(cooler)] than those of the same ar= ea during the El Niño in November 1997. The winds across the entire Pac= ific area of the depiction were generally blowing from the east at that time. The warmest waters were found in the extreme western Pacific.

1= 5. These observed winds and SSTs in November 1998 generally [(were<= span class=3DGramE>)(were not)] consistent with the dep= iction of those of the Figure 3 (p. 9B-3) schematic for a La Niña.

1= 6. The l= ower panel of November 1998 Anomalies shows the Pacific SST anomalies alo= ng the Equator being almost all negative, denoted by the dashed lines, with negative values dropping below [(–2)(–3<= /u>)] C°. This relatively cool [compared to the Neutral ("Normal") Conditions] water is characteristic of La Niña.

1= 7. The N= OAA Climate Prediction Center (CPC) ENSO description of Pacific conditions and their forecast can be found at http://www.cpc.ncep.noaa.gov/products/analysis_monitori= ng/enso_advisory/ensodisc.html. For the past several months, warm anomalies have covered the equatorial Pacific. The forecasts suggest that these warm conditions will strengthen somewhat through the fall and remain over the winter. The CPC discussion and the warm SST and wind anomalies (compare Image 1 to Image 2) across the cen= tral tropical Pacific are all consistent with the existence of [(a La Niña)(neutral conditions)(an El Ni&ntild= e;o)].

For additional displays of current Pacific information related to El Niño and La Niña conditions, including SSTs, anomalies, depth= cross-sections, winds and some animations, go to: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/enso.shtml.

After completing this week's applications, transmit the following work to your instructor:

Investigations 9A and 9B = Investigation Answer Form, from the Study Guide, Week 9, or the DataStreme Atmosphere website.

Current Weather Studies activities 9A and 9B CWS Answer Form.

Return to <= span class=3DSpellE>DataStreme Atmosphere website

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