METR 104:
Our Dynamic Weather
Lab Exploration #2:
Solar Radiation & Temperature
Part III: The Weather
Complicates Things
Dr. Dave Dempsey
Chris Stumpf
Dept. of Geosciences
SFSU, Spring 2012

(5 points)
(Lab Section 1: Wed., Feb. 29; Lab Section 2: Friday, March 2)

Learning Objectives. After completing this activity, you should be able to: Materials Needed. To complete this activity, you will need:

I. Introduction. As noted in Lab #2, Part II, forecasting temperature is one of the most common and useful aspects of weather forecasting. Modern professional weather forecasters typically do it by starting with current and recent observations of weather conditions and applying their understanding of the underlying physical causes of temperature change in a largely quantitative way, to estimate near-future changes in temperature from current conditions. Our intuition is that the sun plays a central (though not the only) role in causing daily temperature variations, as we began to explore in Parts I and II of Lab #2. However, the effect of the sun can in turn be modified or otherwise affected by other aspects of the weather, as the observations presented in this lab should begin to suggest.

II. Instructions. Respond in writing to the questions posed below. Turn in your responses at the end of lab.

Solar radiation and temperature: a complication

    1. Dealing with missing data. Examine the two, 24-hour, back-to-back meteograms for Boulder/Jefferson County Airport (KBJC), Colorado, recorded on April 23 and 24, 2005, linked below:

      Note the missing observations on both meteogrms. In 2005, observations at KBJC were recorded by a human observer, and the airport didn't operate at night, so there were no observations recorded at night. To get a sense of what the temperature might have been doing over the full 48-hour period, we might examine the two, 24-hour meteograms for Denver International Airport (KDEN) recorded at the same time, below. KDEN is perhaps 30-40 miles away from KBJC.

      Considering just the broader aspects of the daytime temperture patterns at KDEN and KBJC and not the small details, do you think that the basic temperature pattern at KDEN is similar to that at KBJC over these two days? (If not, why not?)

      (If they are similar enough, we can use KDEN observations as a substitute for KBJC for some purposes.)

    2. Patterns of observed temperature. Describe the 24-hour temperature pattern at KDEN on each day. How do the temperature patterns differ?

      (In your description, use local standard times, not UTC. KDEN is in the Mountain time zone, which is 7 hours behind UTC.)

    3. Possible explanation(s) for changes in the daily temperature cycle. What other information on the two KDEN meteograms might offer insight that might help explain the differences betwen the two days? Why do you think so?

    4. Refer to the accompanying graph showing plots of one-hour average insolation vs. time (1) at the top of the atmosphere and (2) at the earth's surface, observed at Golden, Colorado on the same two days covered by the meteograms above. Golden, CO is perhaps 10 miles or so away from the Boulder/Jefferson County Airport.

      1. Patterns of observed insolation. For each day, describe the insolation patterns at the top of the atmosphere and at the earth's surface, and compare the patterns on the two days. In particular, how do they differ?

        (Again, use local standard time in your descriptions.)

      2. Possible explanation(s) for the change in observed insolation. There is no noticeable difference in insolation at the top of the atmosphere on the two days, so differences in insolation at the top of the atmosphere cannot account for the differences in insolation at the surface. What weather information on the KDEN meteograms might offer insight to help explain the difference in insolation at the earth's surface? Why do you think so?

        (Be specific about the observations that you think might help, and why. Note that air temperature by itself has no significant affect on insolation, so air temperature is not going to help here.)

      3. More complete possible explanation(s) for the change in the daily temperature cycle. Combine your answers to Questions (3) and (4)(b) above to offer a more complete and better supported possible explanation for the observed change in daily temperature cycle than your response to Question (3) alone can offer.

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