Climatic Regions Lab

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The objective of this lab is to relate the synoptic climate model to different locations on the surface of the Earth.

Relating climatographs to synoptic climatology

1 Synoptic climate model
2 Exercise
3 Results
4 Objectives

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Synoptic climate model

Model of general atmospheric circulation.

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Air masses

Circulation in the Earth's atmosphere consists of 3 circulation cells in each hemisphere. As a result the atmosphere can be divided into three different air masses with substantially different characteristics.

Polar air: Cold air near the poles.
Tropical air: Warm air near the equator.
Temperate air: which lies between the tropical and polar air.

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Fronts

The high and low pressure boundaries between (and within) these air masses also have differnt characteristics.

Polar high pressure: Cold air descending near the poles. Very low humidity.
Sub-polar low pressure: At the boundary between the polar snd temperate air is the sub-polar low. At all areas of low pressure the air is rising. If there is any moisture in this rising air, such as when the air is rising over the oceans, the cooling that occurs as the air rises will produce clouds and rainfall.
Sub-tropical high pressure: Just like the polar high, the sub-tropical high is an area of air descending from the upper atmosphere. This air a very dry (low humidity) so regions affected by the sub-tropical high will have very little clouds and rainfall, which may result in desert climates.
Tropical low pressure (Inter-tropical convergence zone (ITCZ)): This occurs where air from the northern and southern hemispheres converge near the equator. The converging air rises (this is a low pressure area) and can produce substantial amounts of rainfall.

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The atmosphere in motion

The locations of these fronts and air masses change from day to day and over the course of the seasons. For example:

In January it is winter in the northern hemisphere and summer in the southern hemisphere;
- Winter hemisphere
  - the north pole receives no sunlight for 6 months so the pole gets colder and the polar high stronger. The high pressure causes the region of polar air to expand so more area near the north pole experiences the cold polar air.
  - as the polar high expands it pushes the sub-polar low to the south so areas to the south of the average position of the polar low will get the cold, rainy weather associated with the polar low.
  - the sub-tropical high is also pushed to the south and the brings it's warm, dry conditions to more southernly areas.
  - the ITCZ gets pushed into the southern hemisphere.

- Summer hemisphere
  - the ITCZ follows the sun into the summer hemisphere, so the area of heavy rainfall is also in the southern hemisphere.
  - since the sun is over the southern hemisphere the southern hemisphere tropics are warmer and the region of tropical air expands to the south.
  - the sub-tropical high is pushed to the south
  - the sub-polar low deminishes and is pushed to the south.
  - the south pole is receiving continuous sunlight, which deminishes the southern polar high and causes the area of polar air to become much smaller.

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Exercise

The project requires you to download some data from the U.S. National Climatic Data Center (NCDC) website and analyze that data for climatic patterns.

Sample data set for Bangkok, Thailand

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Downloading climate data from NGDC

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Step 1

Select a country or city that you will examine the climatology for.

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Step 2: Finding the data

Go to the website of the National Geophysical Data Center.

Monthly data from global sites - This link for data.
Find data for the country you are interested in by selecting the Country and hitting the "Continue" button.

Select country

If you selected the United States or some of the other large countries then you will be asked if you want to select a state. You should select "Selected Stations in the state" to find your city then hit the "Continue" button.

Select state or find data for entire country.

Select your city from the list on the new page, then press the new "Continue" button. In the example below I selected Knoxville.

Select city.

Select a range of at least 10 years (if possible) and press continue. (use all of the default values for Format Delimiter etc.)

Choose a 10 year range of dates. (I chose 1995 to 2005 in this example.

On the next page is a table that has a "View Inventory" link. Go to this link to check that data is available for all the months (12) in all or most of the years.
- Note: You might find that there is a price attached to some of the data files. This will occur if you are trying to download the data from somewhere other than the university. The data on this website should be free for educational institutions.

View inventory to check how much data is available.

Check that there are a full 12 months of data for at least 5 years. The last column gives the number of months in each year for which there is data. In this example, there is only 1 month of data for 1995, and only 11 months for 1998. This still leaves me with 9 full years.

View inventory to check how much data is available.

If you do not have at least 5 years of full data you will need to go back and find a new city. Otherwise you can download the data.

If the site tries to charge you (usually between $10 and $40) do not pay you should be able to get the data for free if you use a computer on campus.
- A few students have trouble even from campus computers. If you are one of those let me know and we can sort it out.

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Step 3: Download the data

On the website
- select the box saying you have reviewed the inventory then
- enter your email address (not mine),
- click the Submit Request button.

Request data.

It will take a few minutes for the website to process your request but when it has you should be able to click on the link given to access your files.

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The next page will give you a table with 4 different files.
1. The first file is the actual data that you requested,
2. The second file is the file listing the inventory (the number of month of existing data) that you've already looked at,
3. The third file lists the station. There will only be one station listed unless you have tried to get data for an entire state rather than a city,
4. Finally, the last file tells you how to read the data in the first file. The first file, the data file has all the climatic information you requested but it is full of acronyms so you need the final file to interpret it.

Right click on all four files and save them to your computer.

Save files.

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Step 4: Formatting the data

You will import the data into Microsoft Excel and create graphs of the data in order to analyze it. If you do not have Excel on your personal computer, it is available on all university machines.

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Editing and analysing climatic data

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Importing the data file to MS Excel

Open up MS Excel.
Under the "File" menu select "Open" and select the data file you just saved to the desktop. This will give a window asking how you want to import the file.
In this import file window select the option for "Delimited" and press the "Next" button.

Select the delimiter option for "Comma" and press "Finish".

Your file is now in Excel. It should look something like this:

Be sure to save your Excel file as the file type "Excel workbook". It is recommended you save the file by the name of the city.

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Rearanging and graphing data in Excel

You will need to re-arrange the data to be able to answer the questions in this exercise.

Add a new spreadsheet to your workbook (Insert --> Worksheet) and create a table for months and years.

Spreadsheet template

Copy and paste the correct data from the data sheet to the new table.
- You will be using the Mean Monthly Temperature (MTMP) and the total precipitation (TOTP) columns. The dates are located in the YRMNTN column.

Note that the data is given in units of 1 tenth of a degree Celcius for temperature and millimeters for precipitation
- As a result, you may want to divide you temperature numbers by 10 to show the temperature in degrees Celcius.