Monday, May 31, 2010
A friend who has been following the blog asked a question the other day: So, why are we doing CARES in Sacramento, CA; why not southern California, or some other city? Great question! The answer is related to the aircraft and ground-based sampling strategy, which I had promised I will describe a couple of days ago.
In the CARES study, we would like to measure the composition and climate-affecting properties of different carbonaceous aerosols just after they are emitted in an urban area. We also want to measure how these parameters and properties change with time.
Aerosol size, composition, and properties change with time due to various processes, which are collectively referred to as "aging." However, as aerosols "age," they can be transported from one location to another by wind, which makes it difficult to sample the same aerosols again after they have aged if we were to sample from a fixed location, such as a ground site. But if the prevailing wind direction is known, we could put another ground site at some distance in that direction and sample the aged aerosols when they arrive at the second location after a certain amount of time, depending on the wind speed. This is exactly what we are doing in CARES.
Wind patterns in the Sacramento area in summer are complex, but quite regular. As the ground and Sierra Nevada Mountains heat up during the daytime, the warm air above it rises and is pulled up the mountain slopes as cooler marine air gushes in through the Carquinez Strait, as shown in the diagram.
The direction and speed of wind in the Sacramento area is such that the aerosols emitted during the morning rush hour in the urban area will be transported to the northeast in the foothills area by late afternoon. We have therefore placed a ground site in the Sacramento urban area at American River College and another site in Cool at Northside School. The G-1 aircraft will sample across and along the urban plume in the morning and again in the afternoon to get a more complete picture of the evolution and dispersion of the aerosols from morning to late afternoon.
Jerome Fast of PNNL arrived in Sacramento yesterday and will be serving as CARES meteorologist. He will be providing daily weather briefings and forecasts of Sacramento urban plume transport based on the computer model calculations performed by our colleagues Bill Gustafson and Manish Shrivastava, back at PNNL.
Sunday, May 30, 2010
The Eagle has landed. Pilots Bob Hannigan, Mike Hubbell, Bill Svancara, Dick Hone, and mechanic Gene Dukes brought in the Gulfstream-1 research aircraft (G-1) from Pasco, WA (PNNL is located in nearby Richland.), where it is normally hangared when not in use. During CARES, it will be hangared at McClellan Airport, a former Air Force base. The G-1 is being deployed for CARES by the U.S. DOE's ARM Aerial Facility (AAF), which is an integral measurement capability of the ARM Climate Research Facility.
Beat Schmid, the technical director of AAF, and his team, John Hubbe, Jason Tomlinson, Jennifer Comstock, and Celine Kluzek, all at PNNL; along with John Shilling of PNNL; Liz Alexander, Matt Newburn, and Alex Laskin of the Environmental Molecular Sciences Laboratory at PNNL; John Jayne of Aerodyne; Stephen Springston, Gunnar Senum, Art Sedlacek, Jian Wang, and Chongai Kuang of Brookhaven National Laboratory; Kimberly Prather and her graduate students Kaitlyn Suski and Jack Cahill of UC San Diego; Manvendra Dubey and Brad Flowers of Los Alamos National Laboratory; and Fred Brechtel of Brechtel Manufacturing, Inc. have all done a fantastic job of integrating an unprecedented suite of instruments on the G-1, under a strict weight limit, power requirement constraints, and tight schedule.
The G-1 will carry a full payload of highly sophisticated instruments to measure aerosol size distribution, composition, and their climate-affecting properties. The payload also includes various instruments to measure aerosol precursors (gaseous pollutants such as sulfur dioxide, nitrogen oxides, and organic compounds) that upon oxidation in the presence of sunlight would form particles. All these measurements are extremely difficult to make while flying around at 100 meters per second.
In the coming days, I will introduce the AAF folks, the aircraft scientists, and the instruments that make these measurements possible.
Saturday, May 29, 2010
Most of the CARES participants have arrived with their specialized instruments. The remaining instruments will be coming in shortly. I will introduce all of them and their instruments in the coming days. At the moment everybody is very busy hauling, unpacking, and installing their equipment in the trailers at the two sites.
I would like to take this opportunity on behalf of the CARES team to thank our hosts, Mr. Laduan Smedley, Director of Administrative Services, and Dr. Derrick Booth, Asst. Dean of Science and Engineering, at American River College and Ms. Wendy Westsmith, Principal, at Northside School and their staff members for the kind hospitality and help as we settle down in our new home away from home for the next month.
The PNNL team did a great job of setting up the inlet towers and plumbing inside the trailers at both the sites. The inlet system is basically a combination of pipes that bring air into the trailer (via a pump) and distributes it to all the different instruments. It sounds simple, but several factors, such as the material of the pipe, number of bends, air flow rate, etc., have to be considered in the design and installation of the inlet system. It also takes several people to safely hoist the inlet tower and secure it, as you can see in the pictures.
Thanks to Jill Walters back at PNNL for arranging the delivery of all the necessary compressed gas cylinders (purified air, nitrogen, helium). They have arrived at both sites in a timely fashion. Purified air and nitrogen are needed in several aerosol sampling instruments, while helium is needed for weather balloons. Yes, we will be launching weather balloons from both the sites, which should be a fun activity to watch.
The G-1 aircraft arrives tomorrow at the McClellan Airport, which is located less than 3 miles from the American River College site. I will go to the airport tomorrow afternoon and see how we are doing there.
Have a nice Memorial Day. Look for new posts to Rahul CARES on Monday June 1, 2010.
Thursday, May 27, 2010
The 18-wheeler full of PNNL instruments and related equipment arrived at the American River College site promptly at 8:00 AM. The estimated total weight of the equipment: about 20,000 pounds! The PNNL squad — Will Shaw, Danny Nelson, Jane McKinney, Dan Cziczo, Mikhail Pekour, Nels Laulainen, Jim Barnard, Chen Song, and I — spent the entire day unloading, unpacking, and sorting all the equipment and arranging the trailers. We were getting them ready for more CARES participants from other institutions who are scheduled to arrive tomorrow with additional equipment. Jeremy and Oscar from the PNNL IT department were busy setting up internet connections for the trailers.
As expected, the temperature started to drop in a hurry around noon, and dark clouds rolled in just as we were finishing unloading the truck at the Cool site. It was pouring by 1:00 PM, and we even had a brief spell of hail! The rain slowed us down a little, but we pretty much accomplished what we had set out to do for the day.
We all worked hard, and I was particularly impressed with Danny Nelson’s experience and skill in operating a forklift. Way to go, Danny! The pictures should give you an idea of how much stuff had to be carefully moved around today at just one site. Tomorrow we will continue unpacking the instruments, welcome our collaborators and help them settle into their assigned spots in the trailers.
While all this is happening here in Sacramento, the aircraft team, who I will introduce later, is busy preparing and test-flying the DOE G-1 aircraft back at PNNL. The plane is scheduled to arrive here on Sunday, May 30. The NASA B-200 King Air aircraft is already here. In the next couple of blog entries, I will describe the air sampling strategy we plan to use during CARES and the roles of ground sites and aircraft in achieving our science objectives.
Wednesday, May 26, 2010
Since this blog's audience includes folks who may not be familiar with atmospheric aerosols and their role in climate change, I thought it would be worthwhile to provide a very short background.
Atmospheric aerosols are tiny particles suspended in air. They are present everywhere (in varying concentrations), and their sizes can range from a thousandth of a micron to a few microns (the average thickness of human hair is about 0.1 millimeter, which is 100 times bigger than 1 micron). Furthermore, these particles can be composed of naturally occurring substances such as soil dust, sea spray, organic compounds emitted from trees, etc., as well as manmade substances resulting from various types of air pollution, such as vehicular exhaust, power plant emissions, industrial emissions, etc.
While greenhouse gases such as carbon dioxide, water vapor, methane, and ozone tend to warm the earth's atmosphere by absorbing infrared radiation emitted from the earth's surface, aerosols generally tend to cool the atmosphere by scattering (reflecting) the incoming solar radiation. However, certain carbonaceous aerosols (i.e., those composed of carbon-containing compounds), formed from both manmade and natural processes, can absorb light and therefore tend to warm the atmosphere.
Aerosols are also precursors of clouds, which are significantly more efficient than aerosols in scattering light and cooling the atmosphere. The efficiency with which aerosols can scatter and absorb light and form clouds depend greatly on their size, type (chemical composition), and how they are vertically distributed in the earth's atmosphere.
While tremendous progress has been made in the scientific understanding of the effects of aerosols on climate, significant uncertainties and knowledge gaps still exist in role of carbonaceous aerosols and their radiative effects, which essentially serve as motivations for the CARES field study.
The U.S. Department of Energy's Atmospheric System Research (ASR) program is an international leader in climate-relevant atmospheric research related to aerosols, clouds, and cloud-aerosol interactions, and the CARES field study is a part of this program.
CARES officially begins on June 2. At the moment, we are setting up the two ground sites – one in Sacramento at the American River College and another in Cool, CA, at the Northside School where we will make intensive measurements of aerosols and their climate-affecting properties with a suite of specialized instruments.
The four construction trailers (two at each site) that will house all the instruments arrived today. Washington State University's mobile atmospheric chemistry laboratory also arrived today. Most of the day was spent in setting these trailers, leveling them, and hooking up power. The trucks carrying all the instruments will arrive early tomorrow morning, and it will be a busy day unloading them and sorting everything out according to the two sites. Rain is in the forecast all day tomorrow, so we bought some tarps to protect the equipment while the trailers are still being prepared. Hope everything goes smoothly.
Tuesday, May 25, 2010
Hi, welcome to my CARES field study blog. I am on my flight to Sacramento, California, as I begin to write the first entry for my first blog.
Sacramento is the base for the month long (June 2-28) CARES field study that is funded by the U.S. Department of Energy (DOE), and it is focused on improving the scientific understanding of the effects of certain types of air pollution and naturally occurring particles in the atmosphere (a.k.a. atmospheric aerosols) on climate change.
I will write more about the what, why, where, who, and how about CARES in the coming days, but before we embark on this exciting scientific adventure, I would like to take this opportunity to thank the entire CARES team who has worked diligently and sometimes around the clock to pull everything together.
The CARES research team includes more than 70 scientists, post-doctoral fellows, and students from 20 institutions (national laboratories, universities, and research organizations) across the United States. We have been preparing for this intensive field study for over a year now, and the last few months have been pretty hectic, to say the least.
I would also like to acknowledge and extend sincere thanks to the administrators, contracts personnel, engineers, aircraft pilots, mechanics, communications specialists, IT personnel, and other support staff at PNNL and other team institutions, who have worked very hard so execution of CARES can proceed smoothly, efficiently, and most importantly, safely. Thank you all for a job well done!
Now, let the adventure begin . . .Rahul