PACDEX Scientists Chat with Journalists


Scientists Chat


Scientists taking questions

  • Jeff Stith (NCAR), taking observations aboard the NSF/NCAR Gulfstream-V jet
  • V. "Ram" Ramanathan (Scripps), monitoring data from NCAR's Research Aviation Facility at Jefferson County Airport, Broomfield, Colorado

About the time stamps

  • the chat room time stamps are in Coordinated Universal Time (UTC), based on a 24-hour clock, with 20:00 UTC equal to 4:00 p.m. Eastern Daylight Time. Convert UT codes to other U.S. time zones with this conversion chart from the U.S. Naval Observatory.


Chat Log

[20:02] Moderator: Hello everyone and welcome to our chat today. My name is David Hosansky. I handle media relations for the National Center for Atmospheric Research (NCAR), and I'll be moderating the chat.

Joining us today are V. Ramanathan, or Ram for short, of the Scripps Institution of Oceanography and Jeff Stith of NCAR. They are principal investigators on the Pacific Dust Experiment, or PACDEX. This field campaign is examining plumes of airborne dust and pollutants that blow off Asia and cross the Pacific to North America. The plumes are so massive that scientists believe they might affect clouds and weather across thousands of miles while playing a role in global climate.

To study the plumes, the research team is using the nation's newest and most capable aircraft for environmental research, the National Science Foundation/NCAR Gulfstream V, also known as HIAPER. The aircraft, which has a range of more than 6,000 miles and can fly as high as the lower stratosphere, is outfitted with instruments to study the impacts of dust and pollutants. The plane is currently in flight over the Pacific on its second mission for PACDEX.

[20:03] Moderator: Jeff Stith joins us today from aboard the aircraft. V. Ramanathan is monitoring data at the NCAR aviation facility outside Boulder, which is the ground base for PACDEX.
[20:03] Moderator: Our first question is from Peter Spotts of the Christian Science Monitor. Can you give an example or two of the more interesting observations you've made and add some informed speculation about what they may say about the processes you're trying to understand?
[20:05] ram: First we are finding that the entire Pacific Ocean is just a hop-skip and a jump away from N America; the dust and pollution plumes are traveling fast and Hiaper is able to keep up wthe the plume
[20:05] Jeff_Stith_G5: We have found pollution layers in very thin vertical regions, which may be one of the reasons why it is challenging to model these effects.
[20:06] ram: Next, we are seeing dust-soot events one after tha other almost every 3 to 4 days so far
[20:08] Moderator: Our next question is from Seth Borenstein of the Associated Press: What have you found in the preliminary flights pertaining to the net cooling or warming effects of the dust/pollution cloud? How is this different than what was previously known and how do you know this?
[20:08] ram: Fundamentally we are collecting data to get a better understanding of the influence of these aerosols (dust-soot-sulfates-others) on ice clouds, since there is a possibility they may increase very cold clouds which can enhance global warming due to greenhouse gases
[20:09] ram: My CO_PI Jeff Stith can comment on the ice nuclei we may be seeing during our high altitude flights
[20:11] Jeff_Stith_G5: We have found enhancements in pollution levels in some of the upper regions of the storm clouds we studied, just yesterday for example. This is the kind of situation we would like to study in detail to see how these clouds differ from clouds without the added pollution or dust. In the clouds yesterday ice crystals were favored over liquid water droplets in the regions we sampled, making it an ideal case to study.
[20:14] ram: Another interesting finding is that we are seeing dust and black carbon occuring simultaneously at the higher altitudes and the theory suggests that this will enhance their absorption of solar radiation and thus enhance the warming effects of black carbon
[20:15] ram: Fortunately we have radiation sampling instruments to check the theory of dust enhancement of BC (black carbon)warming
[20:16] Moderator: Our next question is from Deborah Zabarenko of Reuters: Some basics: what's the source of the dust and pollution measured in this experiment? Wildfires? Cooking fires? Coal soot? Factory pollution? Vehicle exhaust? Can it be seen by humans aboard the aircraft or just detected on instruments? If it can be seen, what does it look like from 45,000 feet up?
[20:17] Moderator: Satellite images make it look like normal cloud cover. How is this dust different in appearance and function?
[20:17] ram: Jeff: do you want to address this first and I will in later
[20:19] Jeff_Stith_G5: ram and moderator, sorry, I'm watching more than one screen here today.
[20:19] ram: Dust is lifted off from Mongolian and Taklamakan deserts; when it passes over E Asia, it is joined by pollution aerosols due to fossil fuel combusution; bio mass burning; buio fuel cooking; its normally brownish in color
[20:20] ram: The dust by itself will be yellowish in coolor; but when it si mixed with BC it gets brownish; Normally when you are above the dust layer and you look at the sky sideways it will be brwon in color
[20:21] MarkBradford-Jeffco: BC being black carbon
[20:21] ram: Satellite, particularly, SEAWIFS satellie and MODIS, shows the brownish haze
[20:21] Jeff_Stith_G5: We often see layers of dust or pollution and we also detect them with several instruments on the aircraft. We know that a wide variety of sources contribute to these plumes and our instruments can help sort part of that out. For example, we measure soot type particles in real time on the aircraft.
[20:22] ram: On flights in the Arabian sea and near most urban regions we see this brownish haze; I have photos of brown clouds in my websiite
[20:23] Moderator: We have a couple of questions from Todd Neff at the Boulder Daily Camera: Where are you flying right now? How high how fast how long and why?
[20:24] Moderator: Todd Neff also asks: What are the key differences in what you are doing here compared to previous Pacific plume studies, such as NOAA's in 2002?
[20:25] Jeff_Stith_G5: Hi Todd, we are just now flying at 40,000 feet. We will be at high altitude until we get near Japan. Then we will descend into a region that the models suggest may contain dust and pollution at different levels.
[20:25] ram: The main difference is: previous studies such as NOAA-2002 focussed on dust and pollution in clear skies, that too over east Pacific Ocean; this is the first expt, I know of, that is looking at dust-soot as well as how they intract with clouds as well as ice clouds
[20:26] Moderator: Another queestion from Seth Borenstein at the Associated Press: What have you found in the preliminary flights pertaining to storm tracks and the intersection of the dust/pollution cloud? How did the cloud change/interact with the storm and how do you know if there is a causal link?
[20:26] ram: Amother major new aspect of PACDEX is that, it is following the dust plumes and pollution all the way from west Pacific to N American coast
[20:28] Jeff_Stith_G5: Yes, I agree, we are looking for the interaction between the plumes of aerosols with clouds.
[20:28] ram: Not being an expert in synotic storms, I am amazed at how the stormm on the one hand speeds up the transport of dust and pollution eastwards; and at the same time over parts of the storm which is raining it seems to be cleaning the atmosphere
[20:30] ram: Few months ago we published a paper showing that during sprign time, over 75% of the BC over West Coast of NAmerica is due to transport from across the Pacific; now we are beginning to get some inisghts into how this export of BC from e Asia may be aided by the storm tracks
[20:31] Jeff_Stith_G5: We know the aerosols change as they age, which might, for example increase their ability to absorb water. On the other hand the amounts of aerosol are likely to be greater near the sourc
[20:32] Jeff_Stith_G5: e. So we expect to find differences in clouds in the Eastern versus the Western Pacific.
[20:33] Moderator: A question from Peter Spotts at the Christian Science Monitor: Can you give me an rough estimate of how thick the pollution layers are? Presumably separated by layers of relatively clean air?
[20:36] Moderator: Just FYI to the reporters: the current flight path of the aircraft can be seen at the PACDEX Multimedia Gallery
[20:37] Jeff_Stith_G5: We have found layers that are only a few hundred feet think. An interesting thing is that we have observed layers overlying other layers, with significantly different characteristics, such as the humidity threshold where they will transform into cloud droplets.
[20:37] ram: I am assuming Jeff is busy; the dust layers can be as thick as 3 to 10 km near the west Pacific; but as they travel across the Pacific Ocean, the paek dust levels are mainly between 4 km and 12 km. Let us not forget this layer also is mixed with sulfates, BC,CO and other pollution
[20:37] Moderator: Another question from Deborah Zabarenko from Reuters: What happens when the cloud gets to the U.S. West Coast? Does it dissipate or does any of it get further east?
[20:38] Moderator: While we're waiting for Jeff and Ram to respond to the last question, I'll clarify some acronyms: BC is black cabon and CO is carbon monoxide.
[20:39] ram: Our observations do not cover interior N America; but the dust and pollution above 3 km should travel across N America into Atlantic, unless they are removed by rain; this is why dust and soot getting into the higher layers is so important; this is what makes a local into a global problem.
[20:40] Jeff_Stith_G5: Some of it continues further East, depending on its altitude and whether it get removed by storms. These are related to the sizes and types of aerosol in the plumes.
[20:41] Moderator: A question from Todd Neff at the Boulder Daily Camera: NOAA says there's a pacific dust plume over Boulder right now. Did you follow it across?
[20:41] ram: An important climate issue to keep in mind is that, the dust-soot layers whereever they are will be causing dimming at the surface and enhancing heating of the atmosphere
[20:44] Jeff_Stith_G5: Todd, there is a good chance we sampled that plume on Sunday or yesterday. I'd need to compare our locations and data with the trajectories into Boulder to confirm.
[20:44] Moderator: A question from Peter Spotts at the Christian Science Monitor for Ram: Based on INDOEX, did you expect to see dust and BC soot that high? Or is this somewhat unexpected?
[20:46] ram: This is a great question Peter; No; the INDOEX plumes from S Asia were confined mainly below the so-called tradewind inversion at 3 km; whereas these E Asian/Russian plumes are quite high; that worries me greatly, because the igher they are the longer is yheir life times in the atmosphere and greater is their impact on climate
[20:47] ram: For example, a BC aerosol at 10 km may have a factor of 2 to 3 larger climate warming effect that a BC at 1 km
[20:48] Moderator: Another question from Todd Neff at the Daily Camera: How long to you expect it to take until you have a chance to analyze the raft of data you're collecting and report on it? Will it be in a referreed journal?
[20:51] Jeff_Stith_G5: We will have some early results out soon, probably within the year. Analysis of the data, including comparing with simulations will continue for a few years, maybe even longer. We expect to publish most of the results in the peer-reviewed literature.
[20:52] Jeff_Stith_G5: Although some of the earliest results get reported in scientific conferences.
[20:53] Moderator: Let me ask a question: This is the second mission of PACDEX. How does it differ from the first mission?
[20:55] Moderator: And a related question from Laura Allen at Popular Science: How many more flights do you expect in this mission? When will they finish?
[20:55] ram: The first mission git excellent data on the dust-soot plumes and how they are transported long distances; and their geneeral interaction with clouds; during thsi second mission our primary focus is on the interaction between dust-soot and the storm tracks; we are focussing primarily on clouds above 3 km.
[20:55] Jeff_Stith_G5: In the first mission we sampled a variety of dust and pollution sources in the West Pacific, and we also obtained detailed measurements in a frontal storm system in the East-Central Pacific, where more aged aerosols would be expected.
[20:57] Jeff_Stith_G5: We are anticipating stronger dust sources this trip, which will make for an interesting comparison with the data from the first set of missions.
[20:57] ram: We are anticipating about 4 more science mission-related flights: 2 from Japan ; one from Japan to Hawaii or Anchoarge and one near N American coast
[20:58] ram: We expect to finish by April 23rd to 25th.
[20:58] Moderator: Todd Neff at the Daily Camera asks: How many folks are involved in the effort? How many from NCAR?
[21:01] Moderator: Ram, do you want to clarify the finish date -- do you mean May 23 to 25?
[21:01] ram: Oops: Yes It is May 23 to 25th!
[21:02] Jeff_Stith_G5: We have about 30 scientists involved in the project from various institutions as well as several students. About a third of the scientists are from NCAR. NCAR also is providing the flight crew and the support staff, which involves at least a dozen people part time.
[21:02] Moderator: Laura Allen from Popular Science asks: Have there been other major assessments of how the plume pollution affects the U.S. West Coast beyond the paper Ram mentioned? Will PACDEX contribute to assessing the potential health effects for North Americans, or will the work mostly enhance climate understanding?
[21:04] ram: This is an important question that is often misunderstood. The dust-soot plumes we discussed thus far, is mainly aerosols above at least 1 km; some of this does get to the surface which then can become a health issue; We do not know how much of this dust-soot settles over N American surface; subject of future studies, but I am not a
[21:05] ram: I am not aware of any tsudy that has tackled this difficult issue
[21:05] Jeff_Stith_G5: Our focus is on the impacts of the dust and pollution on weather and climate, not on health. However, we expect our results to contribute to the improvement of models that attempt to predict the levels and sources of health-related pollutants and natural dusts.
[21:08] Moderator: That's all the time we have. I want to thank everyone for participating. If reporters have follow-up questions, please let me know. Again, this is David Hosansky at NCAR. My phone number is 303-497-8611 and my email address is Thank you!
[21:09] ram: Thanks to you and the reporters for the penetrating questions.
[21:10] Jeff_Stith_G5: Thanks for setting this up, I hope it was informative. This is Jeff Stith from 40,000 feet and temperature -45 C
[21:10] Jeff_Stith_G5: In pretty clean air, for now!



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