1) An El-Nino occurred during the years of 1982-1983 and 1991-1992; a La-Nina occurred during 1988-1989. Based upon the information in the tables, what happens to the precipitation amounts in the cities of Minneapolis, Los Angeles, and New Orleans during these times?
Based upon the yearly totals compared to the normal yearly total, it appears that during an El-Nino precipitation is above average, while during a La-Nina precipitation is below average. (An exception to this rule is the year 1991 in Los Angeles).
2) Find the total precipitation for the three cities between the following
months. These dates approximate a 12 month block when an El-Nino
or a La-Nina was most intensely felt.
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| July 1982 - June 1983 | 37.68 inches | 25.61 inches | 87.71 inches |
| June 1988 - May 1989 | 22.59 inches | 6.55 inches | 52.66 inches |
| Sept. 1991 - August 1992 | 33.69 inches | 14.94 inches | 64.43 inches |
| Minneapolis: 28.32 inches | Los Angeles: 12.01 inches | New Orleans: 61.88 inches |
4) Based on the above information, how does an El-Nino and/or a La-Nina affect precipitation amounts in the three cities?
It appears that during an El-Nino year, the
cities all receive more precipitation, and during a La-Nina year, the cities
all receive less precipitation.
5) For April 1983, how many inches above average was the precipitation
in each city?
| Minneapolis: 1.55 inches | Los Angeles: 2.46 inches | New Orleans: 10.26 inches |
6) What percentage of the average was the precipitation for each
city in this month?
Have the students find this by dividing the
precipitation for April 1983 by the normal April precipitation, then converting
the decimal number to a percentage. For example, if the April rainfall
equaled the average, the division would produce an answer of 1, or 100%
of the average.
| Minneapolis: 164% | Los Angeles: 442% | New Orleans: 328% |
7) In what year and by how much was the amount of precipitation in each city off from the average (make sure you indicate if the amount was above average or below average)?
Minneapolis: 1983, 10.75 inches above average
Los Angeles: 1983, 17.45 inches above average
New Orleans: 1991, 51.86 inches above average
Extension Exercises:
1) On a separate sheet of paper (or on the computer),
create a line graph: the horizontal axis should represent the months of
the year, the vertical axis the amount of precipitation in inches.
Choose one city: either Minneapolis, Los Angeles, or New Orleans.
Graph three different lines: one representing the amount of precipitation
for each month during 1983, one representing the amount of precipitation
for each month during 1988, and one representing the normal precipitation
amounts for each month.
2) Check your conjectures about precipitation from another El-Nino or La-Nina year for the above cities. Your teacher has the web site addresses for the years of other El-Nino and La-Nina occurrences.
3) Check you conjectures using other cities in the United States. The links on the bottom of the Monthly Temperature and Precipitation Totals page contains this information for several weather stations across the United States.