Name

Name: ___________________________

Lab 1: Graphing Climatological & Meteorological data

QUESTION 1. Many people in Indiana are claiming winters are not as cold as they used to be. A very simple way to assess whether there has been any warming trend in winter temperatures is to construct a graph of temperatures through time. Table 1 presents data on the mean January temperatures for Indianapolis for the period 1961-2000. In order to assess any trends and the year-to-year variability, graph the data in Table 1 using the guidelines below.

NOTE: In questions 1 and 2 of this exercise you will be using imperial ("English") units, i.e., °F for temperature, and inches for snowfall. For most of you, these are the units you are most familiar with. In subsequent labs, most data will be reported in metric (SI units). You will study the basis and rationale for the metric (SI) system in Lab 2.

PART A:

1. In this exercise we are interested in temperature through time, i.e., time is our independent (x) variable, and temperature is our dependent (y) variable.

2. Select a scale for each axis so that all points fit on the plot and the graph fills the page (you can rotate the graph paper). Think about the range of temperatures to be plotted. How many years do you have data for? How many squares on the graph paper do you have for each axis following the guidelines in the introduction to this lab?

3. Label each axis with the appropriate variable name and units (e.g. "Temperature (° F)").

4. Use a small "x" or dot to mark the location of each data point.

5. In this example we are interested in a time series, i.e., how temperature has varied through time, so draw a line using a ruler, which connects each data point.

6. Add a title to the graph.

TABLE 1

Mean monthly January air temperature (°F) for 1961-2000 for Indianapolis

Source: United States National Climatological Data Center

Year	T (°F)	Year	T (°F)	Year	T (°F)	Year	T (°F)
1961	23.6	1971	23.4	1981	23.5	1991	26.9
1962	23.7	1972	26.5	1982	20.1	1992	31.5
1963	19.5	1973	30.7	1983	30.6	1993	31.6
1964	30.7	1974	31.6	1984	22.8	1994	21.8
1965	27.5	1975	32.0	1985	20.4	1995	28.6
1966	22.4	1976	23.9	1986	28.5	1996	25.1
1967	32.6	1977	10.3	1987	27.6	1997	24.3
1968	25.1	1978	18.2	1988	25.9	1998	36.6
1969	25.7	1979	18.0	1989	36.3	1999	28.5
1970	17.9	1980	28.5	1990	37.3	2000	27.9

PART B:

The climate at a place is often compared to the "Normal". The "Normal" is the average of 30 years of data for a particular phenomenon, in this case temperature. The Normal is used as a reference in subsequent years until the new Normal is calculated.

1. Calculate the "Normal" (i.e., mean temperature) for the 30-year period 1961-1990 and 1971-2000. Report your answers using only one decimal place.

Normal 1961-1990:

Normal 1971-2000:

This is calculated by adding up all the values of interest and dividing through by the number of observations. Remember for the Normal we are interested in 30 years (1961-90), not all the years (which in this case is 40).

In mathematics/science, special notation is often used. Using this notation the mean can be expressed as:

Where x_i is the variable of interest (in this case temperature);

n is the number of values of x_i (in this case, for the Normal, 30);

S sum from i=1 to n (in this case, for the Normal, n=30).

i=1 is the first value of x_i; i.e. x_i=x₁

Or putting this into words, sum all the values from the first to the thirtieth and divide through by the number of observations (i.e., 30).

2. Draw two lines to indicate the Normal (1961-90 and 1971-2000) air temperature on your graph. To do this draw straight lines at the y-axis level right across your graph. Label it as the Normal (mean) with the value that you have calculated. Be careful about where the line should start and end. Think about what this line is representing exactly.

3. Calculate the mean temperature for each decade (1961-70; 1971-80; 1981-90, 1991-2000). Record your results in the table below. Report your answers using only one decimal place.

Decade	1961-70	1971-80	1981-90	1991-2000
Temperature (°F)

4. Do you agree that January temperatures are getting warmer? Explain the basis for your answer in a couple of sentences.

HINT: Look at the trend through time.

QUESTION 2. Another claim being made by residents of Indiana is that the state gets less snowfall than it used to. Table 2 presents data on winter snowfall in Indianapolis for the period 1961-2000. The data are the total snowfall for each winter season (from October to April).

TABLE 2

Seasonal Snowfall Totals (in inches) for 1961-2000 for Indianapolis

Source: United States National Climatological Data Center: NCDC

Season	(Inches)	Season	(Inches)	Season	(Inches)	Season	(Inches)
1961-62	27.5	1971-72	19.9	1981-82	58.2	1991-92	14.7
1962-63	29.4	1972-73	7.9	1982-83	7.1	1992-93	28.5
1963-64	34.3	1973-74	44.8	1983-84	41.9	1993-94	30.7
1964-65	36.5	1974-75	31.8	1984-85	27.8	1994-95	19.2
1965-66	12.5	1975-76	21.1	1985-86	20.4	1995-96	50.3
1966-67	25.1	1976-77	30.0	1986-87	19.9	1996-97	31.5
1967-68	36.7	1977-78	57.9	1987-88	11.3	1997-98	10.4
1968-69	18.7	1978-79	38.4	1988-89	13.3	1998-99	29.7
1969-70	38.2	1979-80	24.8	1989-90	26.0	1999-00	24.1
1970-71	13.1	1980-81	17.3	1990-91	17.5

PART A:

Graph the data using a bar graph. Again select a scale so all values fit on the plot and the graph fills the page. Your horizontal axis will indicate the winter seasons. The vertical axis will indicate the amount of snow (in inches).

PART B:

1. Calculate the "Normal" (i.e., mean snowfall) for the 30-year period 1961-1991 and 1970-2000.

Normal 1961-62 to 1990-91:

Normal 1970-71 to 1999-2000:

2. What is the mean snowfall for the period 1990-91 to 1999-2000?

3. Do you think there is any evidence for decreasing snowfall? Explain the basis for your answer.

4. Why do you think snowfall is so variable on an annual basis in Indianapolis?

HINT: Look at both your temperature and snowfall graphs.

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