West Point Ozone
1st part
due date: TBA
General Problem: Why did West Point experience ozone levels above 100 ppb in the summer of 1993?
Some general remarks:
Data entry:
Enter the data into the spreadsheed following the format discussed in class. Some abbreviations used on the data sheet: "DLTEMP": Temp(2m)-Temp(10m), indicator of inversion there are two ozone channels (OZONE and O3DUM) that should give you similar results; "SD1" is the standard deviation of the wind direction; "SCAWSP" is the scalar windspeed (not needed here); "WETNES" is an indicator of fog; "D" air flow was turned off, data should not be used; "<" less than full set to calculate average; "F" failure.1 Geographic setting:
Where is West Point? Look at the maps and note its relationship to the Hudson River, neighboring mountains, etc. The location of the ozone monitoring station is 41o21'N, 74o3'W, at an elevation of 200m.
2. Precursor sources:
What and where are the likely sources of NOx and VOCs in a 300 km radius around West Point? How far away and in which directions are possible sources of anthropogenic emissions? (Use the provided maps, you may also want to look at this image of the US at night.
3. Ozone reaction:
How does solar radiation, temperature and relative humidity vary over the course of your day? How can you explain these trends?
How does ozone concentration vary over the course of the day? Note the time of the ozone maximum. How does the pattern of ozone concentration relate to solar radiation?
Does the daily ozone maximum occur at the same time as the peak in solar radiation, earlier or later (By how many hours)? Why does this occur?
4. Meteorological conditions:
How does the wind direction vary over the course of the day? Are changes in the wind direction related to changes in the wind speed? How can you explain these variations?
What are the wind directions during the time of highest ozone levels?
The National Research Council states that high ozone levels are associated with low winds, so that little mixing occurs. Is this the case here?
5. Summary of your day:
How can you explain the observed relationship between ozone concentration and the other parameters measured at West Point on your day?
2nd part
Store your spreadsheet including the plots on a disk. We will ask you to present your plots in front of the class and interpret the data. Print out the plots you find most important.
Download the merged multiple day data set from the WWW (http://www.ldeo.columbia.edu/~martins/eda.html) and answer the following questions:
6. Extended time series:
Plot up all data for the entire time series vs. time, as we discussed in class. Discuss how environmental conditions change during these 10 days and result in variations in the ozone concentration. High ozone levels often persist for several days, when meteorologic conditions are appropriate. How long do the event[s] last in this data set?
7. Temperature and ozone:
The NRC report showed that at temperatures less than 90— F, there is no correlation between temperature and ozone concentration. But above 90— F, there is a strong correlation. Plot up the data as a scatter plot and see if you see a similar picture or something different.
8. Maximum temperature and ozone:
There is supposed to be a correlation between maximum temperature and maximum ozone level on a daily basis. Plot up the maximum values for each day as a time series (so this is different from the question above, because here you are picking the maximum temperature and maximum ozone concentration, without paying attention to the time of day), and as an x-y plot, and see if there is any correlation e.g. which days are cloudy? How do you know? Do these days have lower ozone concentrations?
9. Wind direction and ozone:
Plot the ozone concentration and the wind speed as a function of wind direction (scatter plot). Does it matter for the ozone concentration where the wind is coming from and at which speed it is blowing?
We want you to summarize your findings in a laboratory report format. We will discuss the details next week. In the lab report, you should answer the general question:
Why did West Point experience ozone levels above 100 ppb in the summer of 1993? Be creative in your answer, and illustrate it with a couple of key plots. Conclude with any questions that you have about the data and/or the processes involved.
