July 7, 2010
Today's run started out with clear skies at 2:00pm GMT. There was significantly, for Decatur, low humidity outside; but the Aerosol Optical Thickness was still about 1.218 for our location and for the wavelength of EARL's laser. Laura Bishop, from ITS, set the EARL computer so that a person could access the ASC Network drive for Students, the W drive, on it. As a result, we did not take data from 3:55pm GMT until 4:39pm GMT. However, now we are able to access EARL data directly from both the EARL computer and the SARA computer if we save the data folder to the EARL folder on the W drive. That way, we do not have to save data to a CD disk every day, as we have been doing, in order to view the data and analyze it with Matlab. Matlab is only on the SARA computer, not on the EARL computer. This makes life much easier for the two of us. It also allows the professors to access the data as long as they are logged onto the ASC server, which they usually are.
They were several low-lying clouds today, righta bout 1 kilometer, from about 3:00pm GMT until 3:55pm GMT, when the laser and EARL computer were temporarily turned off. Later on, at around 6:00pm GMT until 7:30pm GMT, there were several clouds up at 2 kilometers. Since none of these sections show up as depolarized on the Depolarization Ratio graph, we can safely assume that they did not have any significant amount of ice or aerosols. At that altitude, the clouds should only be composed of water and should only show up on the Range Corrected Backscatter graph. They do, and so everything seems normal.
They were several low-lying clouds today, righta bout 1 kilometer, from about 3:00pm GMT until 3:55pm GMT, when the laser and EARL computer were temporarily turned off. Later on, at around 6:00pm GMT until 7:30pm GMT, there were several clouds up at 2 kilometers. Since none of these sections show up as depolarized on the Depolarization Ratio graph, we can safely assume that they did not have any significant amount of ice or aerosols. At that altitude, the clouds should only be composed of water and should only show up on the Range Corrected Backscatter graph. They do, and so everything seems normal.
Once again, however, we see the interesting effect that always shows up with low-lying clouds. Where the low clouds are, the depolarization signal is very noisy directly overhead. It seems like a spike of noise goes downward directly to the cloud layer, but otherwise is clear in the bottom section of the graph. The noise at higher altitudes is always frequent. Also, for about a meter or so below the clouds, there is a noisy depolarized signal, compared to the complete lack of noise and utter blackness/zero returns where the clouds themselves are.
Overall, today was a rather uneventful day. We had to place the cloud cover on at 5:15pm GMT and at 6:11pm GMT, but neither time did we have to have the cover on for more than 15 minutes. However, at 6:11, the cloud cover's necessity was due to an extreme saturation of both the short and long range channels. The long range channel was up at 90,000 counts when it usually is about -10,000 for lower clouds. The cloud corresponding to this time on the Range Corrected Backscatter graph, however, seems no different than any of the other clouds that only produced -10,000 counts.