Lab10_GEOL1147 (Patrick)
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Apr 3, 2024
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Lab 10 for GEOL 1147 (Introduction to Meteorology Lab) The Southern Oscillation Index (SOI) is a standardized index based on the observed sea level pressure
differences between Tahiti and Darwin, Australia. The SOI is one measure of the large-scale fluctuations in
air pressure occurring between the western and eastern tropical Pacific (i.e., the state of the Southern
Oscillation) during El Niño and La Niña episodes. When the SOI is negative (positive), it corresponds to El
Niño (La Niña) event. 1.Use the SOI index listed in Lab10_soi.xls to calculate the averaged SOI index in Jan and Feb.
2. Plot time series of SOI (Jan & Feb) and Precipitation at San Diego (Jan & Feb). Plot the scatter plot of
SOI (Jan & Feb) and Precipitation at San Diego (Jan & Feb). Copy Jan & Feb precipitation at San Diego
from Lab9_SAN.xls to Lab10_soi.xls. Calculate averaged precipitation in Jan & Feb. Then plot averaged
SOI (Jan & Feb) versus Precipitation at San Diego (Jan & Feb).
3.Does negative SOI (El Nino event) correspond to wet winter at San Diego?
yes
4. The National Atmospheric and Oceanic Administration's Earth Systems Research Laboratory (ESRL), in
Boulder, Colorado, provides Web access to many years of atmospheric observations analyzed for use
originally by computer forecasting models. Among other things, the Web site allows you to construct
"composites" (by which ESRL means averages of spatial patterns over time) of a variety of atmospheric
quantities, including wind speed at various levels in the atmosphere.
4a.
Access
ESRL's
Monthly/Seasonal
Climate
Composites
Web
site
at
http://www.esrl.noaa.gov/psd/cgibin/data/composites/printpage.pl. 4b. Specify the quantity that you want to analyze and plot: Pull down the "Which variable?" menu and select "Scalar Wind Speed". 4c. Specify the level in the atmosphere where you want to analyze the wind speed: Pull
down the "Level?" menu and select "300 mb". 4d. Specify the period of particular months of the year (the "season") during which you want to analyze the
wind speed at 300 mb: Pull down the "Beginning month of the season" menu and select "Jan". Pull down the "Ending month"
menu and select "Feb". 4e. Specify the range of years for which you want to compute a composite average of 300 mb wind speed
during January and February (JF):
In the "Enter range of years" text box, enter "1950" to "2012". 4f. You are going to create a "color-filled" contour plot, which is a contour plot (of lines of constant wind
speed, or isotachs) in which the area between each pair of adjacent contour lines is filled in with a different
color. Specify a plot color: Pull down the "Color" menu and select "Black and White". 4g. Under "Override default contour interval?", in the "Interval" text box, enter "2.5" (which means 2.5
meters per second). In the "Range: low" text box, enter "30" (that is, 30 meters/second). In the "Range:
high" text box, enter "50" (that is, 50 meters/second). 4h. Rather than viewing a plot for the entire world, create one for North America (which focuses more
closely on the area of interest to us, the West Coast of the U.S.): Pull down the "Map projection" menu and
select "North America". 4i. Click on the "Create plot" button. This should create the specified plot and display it in your Web
browser. 4j. Plot Scalar Wind Speed for El Niño years (1983, 1992, 1998) and La Niña years (1974, 2008, 2011).
Describe the differences of jet stream during the El Nino and La Nina years. During El Niño years, the jet stream tends to be stronger and more persistent across the southern
United States, leading to increased storm activity and higher than average precipitation in the southern U.S.
The jet stream is also shifted further south than its usual position, which can result in warmer temperatures
and drier conditions in the northern U.S.
During La Niña years (1974, 2008, 2011), the jet stream tends to be weaker and less persistent, with more
frequent shifts in position. The jet stream is typically shifted further north, leading to cooler and wetter
conditions in the northern U.S., and warmer, drier conditions in the southern U.S.
5. Plot 1000 mb air temperature for Jan and Feb in El Niño years (1983, 1992, 1998) and La Niña years (1974, 2008, 2011). Also plot the anomaly figure for 1000 mb air temperature for El Niño years (1983, 1992, 1998) and La Niña years (1974, 2008, 2011). Plot the figure for the whole globe. Describe differences in the 1000 mb air temperature between El Nino and La Nina years. During El Niño years, you can expect to see above-average air temperatures over the eastern Pacific Ocean
and cooler temperatures over the western Pacific. The warming of the eastern Pacific can lead to an
increase in global temperatures, with the effect being more pronounced in the tropical regions.
During La Niña years, the opposite pattern is observed, with cooler than average temperatures in the
eastern Pacific and warmer temperatures in the western Pacific. This can lead to a slight cooling effect on
global temperatures, especially in the tropical regions.
6. Plot the 300 mb vertical velocity (omega) for Jan and Feb in El Niño years (1983, 1992, 1998) and La
Niña years (1974, 2008, 2011) over the North America. Negative (positive) omega refers to rising
(sinking) air. Describe differences of vertical velocity between El Niño and La Niña years and their
relationships to the precipitation at San Diego.
During El Niño years, the 300 mb vertical velocity (omega) over North America tends to exhibit
rising air motion (negative omega) over the southern U.S. and sinking air motion (positive omega) over the
northern U.S. The rising air in the south can lead to increased precipitation, including at San Diego.
During La Niña years, the opposite pattern is typically observed, with sinking air motion (positive omega)
in the southern U.S. and rising air motion (negative omega) in the northern U.S. This can lead to decreased
precipitation in the southern U.S., including San Diego, and increased precipitation in the northern U.S.
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