Now we present a quick tutorial to help you get up and running. We suggest printing out this help page and following along (if you're in Windows Help, just go to File > Print Topic... to print this page).
Loading a little data
Digital Atmosphere comes with a set of prepackaged data for November 18, 2000. To load this data, just choose File > Import a File and select the folder "tutorial". Select the file "incoming.txt". Digital Atmosphere will import all the weather data in this file (this file contains METAR surface observations and upper air radiosonde reports). On a Pentium III it takes about 15 seconds. That's all there is to it! Now you can plot the data, analyze it, or perform other operations.
Make sure we're at the surface
We want to make sure we're looking at data at the surface, so check the toolbar and make sure Active Level shows "Surface". Digital Atmosphere usually starts with this set to Surface.
Looking at the big picture
Meteorologists usually like to get their first look at a weather chart using isobars (lines of equal pressure). To display these, choose Analysis > Pressure > Sea level pressure. Congratulations -- you've made your first weather map, and it was incredibly easy. You'll notice a deep low over the northern Plains, with a Pacific high dominating the western U.S. and an old polar air mass over the southeastern United States.
Generating a new base map
Sometimes we don't want to look at the same location all the time. Let's zoom in on the West Coast. First choose Map > Generate Base Map. Set projection to "Orthographic" (this is the default projection). Set Scale to 1000 miles. Note that you can change the image size if you want to; if you feel like it, go right ahead (we suggest a width of 1000 and height of 750 for most purposes). Most importantly, under Quick Pick put SLC in "By Station". This tells Digital Atmosphere that you want the map centered on the identifier for Salt Lake City, Utah. Pick "OK" and wait about 30 seconds. During this time you will see the map drawn. Watch for a "Map drawing completed" in the status window to the left, and for the cursor to change from an hourglass to a pointer. Is it done? Good. Let's save this map for future use. Pick Map > Save base map and in the File window type saltlake and press Save. Now you can retrieve this map at any time in the future!
Recentering the map
Centering the map on a new location is easy. Right-click on the center of Wyoming, and choose Recenter Map. If you want another 30 seconds you'll see a new map drawn, centered on Wyoming! When it's finished, however, let's load the Salt Lake City map again. Go to Map > Load base map and choose the "saltlake" file.
Easy map operations
Did you know you can measure distances with Digital Atmosphere? Simply put the cursor over a certain spot on the map, and hold down the left mouse button as you move the mouse around. Notice that you see a box and a line that moves with you. The line helps show you the path between your two points. The box defines an area, which is often used to quality-check a group of observations. At the bottom of the window, note that the status bar is displaying the latitude and longitude of each point, and the bearing and distance between the two! The line drawn on the map is actually a great circle line, and on global map views you will notice that it forms an arc rather than a line. This arc is actually the shortest distance between the two points, and it just appears as an arc because of the map projection distortion.
Looking at station plots
Station plots are little "packets" of data that appear on the map at various locations, showing the actual observed conditions at that location. Plotting them in Digital Atmosphere is a snap. Just click on Data > Data plots. Instantly the map is filled with a smorgasbord of information. Take a look at the plot next to the Great Salt Lake. It shows a temperature of 27 degrees, a dewpoint of 16 degrees, and a sea level pressure of 1032.5 mb (prefix it with "10" if it's below 500, "9" if it's above 500, and add a decimal point between the second and third digit). The line at the right is the pressure trend over the past 3 hours; it was steady, and the change was 0.0 mb (divide the number shown by ten). The long shaft sticking eastward is the wind direction; it always sticks INTO the wind, so the wind is blowing from the east. There is one tiny barb on the shaft, indicating a wind speed of 5 mph (every long barb is 10 mph; every short one is 5 mph). And in the center circle, there is a quarter of shading, indicating 2/8ths cloud cover. The amount of shading is proportional to the amount of clouds. You'll also note that some stations have a square; this means the observation was made by a computerized station. Some stations (not in this particular example) have a red color; this means bad (IFR) weather, while some are blue which means marginal (MVFR) weather. The coloring is determined strictly by visibility and cloud height and is more for the use of pilots and experienced meteorologists, though they can clue you in on where significant weather is happening. If you look in the southeast U.S., you'll see that some stations have two fat dots. This is the international symbol for rain.
Cutting down on crowding
Notice that in Wyoming and Colorado the plots are a little too close together. We can easily change this to improve legibility. On the tool panel take the Data Plot Crowding slider and move it to 50. Now go to Map > Erase map, and choose Data > Data Plots again. You'll notice a lot of stations have disappeared! You can use the data plot crowding slider to control how many observations are shown. Most meteorologists try to max out the setting without making the plots so crowded the data is unreadable. Let's move the slider back where it was: move the Data Plot Crowding slider to 80.
Overlaying more contours
Now choose Analysis > Pressure/Height > Sea level pressure. Nice! You just added the same field seen earlier on top of the map. This illustrates how you can view different meteorological fields at the same time.
Seeing the wind flow
It is possible to visualize the wind field. Go ahead and click on Map > Erase map. Now choose Analysis > Wind > Wind speed (barbs). You'll see a pretty cool gridded array of wind patterns! It's the ideal thing to depict how the air is moving.
Looking at isotherms
Remember how you overlaid isobars on the map? It's easy to overlay other fields, such as isotherms (lines of equal temperature). Just go to Analysis > Temperature > Temperature (F).
Get new weather data
Now it's time to get real data! Make sure you're connected to the Internet. Now go to Internet > Retrieve Data. Press Uncheck All to make sure we start with a blank "shopping list". Now check METAR from COD. This makes sure we retrieve surface (METAR) data from College of DuPage's server. Now press Retrieve. The data will be loaded in just a matter of seconds and is ready to view (if you have any error messages please see our FAQ at http://www.weathergraphics.com/faq.htm ). Now go to Map > Erase Map and choose Data > Data plots. You're looking at current weather!
That completes the quick tour of Digital Atmosphere. This tour was only intended to give you a feel for how Digital Atmosphere works. You've covered all of the basic functions, and now you can build on your knowledge by playing around with the software and reading through this help guide. There's almost no way you can "break" Digital Atmosphere just by experimenting. Have fun!