13 September 1995
PH: Okay. To summarize this flight it was devoted to two plumes, which were sampled about 100 miles north of Porto Velho. First plume was what we could call a primary forest burn, although it was still burning of slash and encroaching on the forest. We got some good chemistry samples close on the fire for emission factors. Then the plume was going pretty much straight up. We moved up higher and got some penetrations at various levels. And then up through the cloud above it got some samples in the cloud. Sampled some smoke coming out of the cloud. Then descended. By this time, the cloud was dissipating somewhat. Descended back down; fire had pretty much diminished by quite a bit by that time, much less flaming combustion. Then some time later, after doing background samples, we did a pasture, grass fire, got series of good samples in that for both chemistry and downwind samples, humidigraph, CCN. And then finally as we headed back, we went through a few of the cumulus clouds. Ray, summarize?
RW: Pretty good optical data through both fires. The first fire was very white. In fact, all passes of it were very characteristic of the background air here. The grass fire had at least one component on two passes that had a little more absorbing component to it than the other. So there was some difference there. The stuff going up into the cloud was a darker smoke. And we took a humidigraph of that as well. That's about it.
PH: Yes, when we started off that grass fire was flaming quite well, and produced the blacker stuff you saw. Then we went through some more smoldering whiter stuff, and then we went again through the blacker smoke that had gone higher up when I think you saw it.
RF: Say, it wouldn't surprise me if they spread some gasoline on that to start it. That first flash of flame was possibly due to gas.
PH: Yes, it may well be. That's something we don't know very much about, but I never see any one down there and see no sign of activity.
RW: But you know, it didn't really look black and it was more of a heavy brown.
PH: Yes, it didn't look black, it was just a brownish puff. Maybe with a flaming component. Are you ready, Ron?
RF: Yes. Basically two emission factors. One on the forest and one on the grass fire. The usual for Vanderlei and a lot of hot and cold DMPS on the bags.
PH: Okay. Don.
DS: Okay. Well, CCN worked pretty good again today, although I want to note that after the grass fire, when I shut the CCN down for chemistry measurements, I couldn't get it going again. The AC breaker kept popping every time I turned on the pumps. So it got a little too hot.
PH: Okay, Art.
AR: Okay. We had a conditionally unstable day. Almost like the kind you might see in the south or Florida with regional blotches of haze over the area. We left Porto Velho, which was very hazy and murky, and after getting to the point of where we were going to look for fires there was a much cleaner region there and the cumulus were really popping by that time up to levels far above 10,000 ft, generally 10,000 to 20,000 ft, some ice indicated in the area. We passed through a number of those to establish cloud droplet spectra in these cumulus congestus clouds, which I estimated had updrafts of 5 to 10 meters per second. We found what may have been a warm rain event here. It's on the marginal side and we will have to do a little more research to see about that. That would be the first of those events.
PH: And we went through some rain about that time as well. Didn't we? Quite a nice little shower.
AR: That's right. We went through about three showering clouds and I think the first one was a warm rain event, but I'll have to go back and look at the video and try and figure the top on that a little better. And we had light and variable winds. They were light and southwesterly at Porto Velho during take off and then switched to the north and northeast by cloud base at the mid-cloud levels of about 5 knots. As a result, we saw big switchbacks in most of the plumes, where they would start out going to the north or almost straight up and then hook back toward the southwest.
PH: Okay. Any other comments?
AR: Yes, I wanted to add that cloud base on climb out was around 3,800 ft and about plus 22[[ring]]C and then here at the end of the day it was at about 5,200 and about plus 19[[ring]]C.
PH: Okay. Good.
PH: Okay, Art. Why don't you just describe briefly what you've just done?
AR: Well, we were trying to establish a firm number on cloud base height and temperature. It wouldn't be exactly the same that we started with because they tend to rise during the day, but it's in that ballpark. And then we're trying to look at how the droplet spectrum develop from the cloud base measurements that we made to the next level increment of 2,000 ft and then subsequently I think we went to 6,500 ft and finished things off. Rod got back on the airway and prepared for his trek to Porto Velho.
PH: Okay. Good.
AR: We have three steps of cloud base droplet spectra data.