Rahul CARES
Meet Rahul Zaveri
Rahul Zaveri is the lead scientist for the CARES—Carbonaceous Aerosols and Radiative Effects Study—campaign taking place June 2-28, 2010, in the central California region to the northeast of Sacramento. This field campaign is designed to increase scientific knowledge about evolution of black carbon and secondary organic aerosols from both urban/manmade and biogenic sources. He'll be sharing his experiences with you through this travelogue, as well as PNNL's Facebook page. 
Rahul is a chemical engineer whose career has involved a wide range of research experience including assessment of transport, transformation, and fate of energy-related emissions. His expertise is in developing and applying multiphase gas-aerosol-cloud chemistry models in the analysis of field and laboratory measurements to solve complex atmospheric chemistry problems. »» Learn More
Dear CARES participants and interested colleagues
We are pleased to report again at the successful completion of the field portion of the CARES campaign. The field study began on June 2 and the last sampling day was June 28. The DOE G-1 aircraft flew 67.4 hours over 21 research flights. The NASA B-200 flew in coordination with the G-1 as well as sampled areas outside of the G-1's primary domain. The NOAA Twin Otter shifted its operation to Sacramento from June 15 through 28 to collaborate with CARES. I have attached a few slides of some pictures of the T0 and T1 ground sites, various aircraft, and participants; summary of the daily flights and other campaign activities; and links to outreach information and news media stories.
Thanks again to our hosts at McClellan Jet Services and American River College in Sacramento and Northside School in Cool, CA. And thanks to all the participants and support staff for their hard work and a great display of team spirit throughout the campaign.
We now look forward to working closely with all the CARES participants and other collaborators in analyzing the rich dataset and disseminating the results through conferences and peer-reviewed literature.
Best wishes,
Rahul Zaveri, Will Shaw, and Dan Cziczo
Campaign Highlights
Wednesday, June 30, 2010
Today, Rahul Zaveri returns to Pacific Northwest National Laboratory in Richland, Washington, to begin the task of evaluating and analyzing the aerosol data collected in the CARES campaign. Thank you to all the people who visited Rahul's travelogue throughout June.
Monday, June 28, 2010
We had the highest ozone and aerosol concentrations of the entire study on the last day! The high concentrations were the result of stagnating air over Sacramento in the morning coupled with hot temperatures and sunny skies. We carried out two G-1 and B-200 coordinated flights to sample the concentrated Sacramento plume in the morning and again in the afternoon as it slowly moved eastward. The NOAA Twin Otter also flew in the plume between 10:30 AM and 2:00 PM. The two ground sites also collected valuable data in the plume over the course of the day.
It's been a hectic month here in Sacramento, to say the least. I'd like to thank the entire CARES science team, aircraft crew, and the support staff for their hard work and professionalism as we went through the ups and downs of the campaign. Special thanks are also due to all the family members and who were away from their loved ones for up to 5 weeks straight during the field activities.
As I write this last blog entry tonight, I am reminded of Henry Ford's quote on teamwork:
"Coming together is a beginning.
Keeping together is progress.
Working together is success."
The CARES team came together, kept together, and worked together the past 4 weeks, but the job is not done yet. The end of the field portion of the CARES study marks the beginning of the long journey ahead that entails analyzing the data, presenting new findings at conferences, and publishing the results in peer-reviewed scientific journals. I look forward to working with the team over the coming months and years as we analyze the data and bear the fruits of the study.
Thanks to Kathryn Lang, Christine Novak, and Patricia Mosley at PNNL for managing the CARES blog site. I truly enjoyed writing about the daily field activities, participants' roles, their instruments, and the scientific issues related to the effects of air pollution on climate change. Thanks very much for reading!
Until the next adventure . . .
Rahul
Sunday, June 27, 2010
While I don't have the actual numbers, I believe we have collected a few terabytes of data over the last 4 weeks. Each instrument's principal investigator will check the quality of their data in the coming weeks, apply calibration corrections where necessary, and prepare preliminary datasets for further analysis. This is a painstakingly slow process. More comprehensive data analyses will begin once the final datasets are prepared and shared with all the participants of the study. One of the main objectives of the CARES study is to use the field data to evaluate, improve, and validate mathematical representations of aerosol processes and properties used in computer climate simulation models. The collection of computer codes (programs) that describes the various aerosol processes and properties is referred to as an "aerosol module."
Over the past 12 years at PNNL, I have led the development of a comprehensive aerosol module called "MOSAIC" (Model for Simulating Aerosol Interactions and Chemistry). MOSAIC was recently implemented in the next-generation Weather Research and Forecasting (WRF) model to simulate aerosol formation, transport, and the associated direct and indirect radiative effects at regional scales.
As part of CARES data analyses, we will evaluate and improve representations of carbonaceous aerosols in MOSAIC, including secondary organic aerosol formation, new particle formation and growth, black carbon aging, and the related optical properties, and cloud condensation nuclei activation properties.
The ultimate goal is to produce a reduced and more efficient version of MOSAIC that is well evaluated using field and laboratory measurements under a variety of conditions for use in global climate models.
Tomorrow is the last day of the study. It's going to be another hot and sunny day, with highs in the mid 90s. The forecast calls for stagnating conditions over Sacramento in the morning, with the urban plume slowly moving to the east by late afternoon. We are scheduled to carry our last two flights, and the plan is to sample the freshly emitted aerosols in the Sacramento plume in the morning and aged aerosols in the same plume in the afternoon one last time.
Saturday, June 26, 2010
We are nearing the end of the CARES field study, with just two more days to go. Everybody is quite anxious to go home after having spent nearly 5 weeks here. At the same time, everybody is excited about the data we have collected in this study. We had our third and final science meeting today to review the data and discuss preliminary findings from the different instruments at the two ground sites and on the aircraft. Overall, we have collected a very rich and unique dataset, which should provide new insights into the evolution of different types of carbonaceous aerosols and their climate-affecting properties.
I'd like to take this opportunity to highlight the remaining instruments we have deployed in CARES. Dr. Will Shaw, Mr. Danny Nelson, Dr. Larry Berg, and Dr. Mikhail Pekour of PNNL have set up weather stations at both the ground sites and special radars at the Cool site that measure wind speed and direction at different altitudes. They also have been launching radiosonde weather balloons—5 on days we have aircraft flights and 1 on the remaining days—to measure vertical profiles of temperature, pressure, and relative humidity. These meteorological measurements will be very useful in characterizing the vertical structure of the atmospheric boundary layer and in figuring out the transport of aerosols from different source regions to our sampling locations on the ground and in the air aloft.
The other set of instruments are specialized particle samplers, which essentially collect aerosol particles on disks or filters for detailed analyses to be carried out later with a number of sophisticated laboratory techniques. Dr. Alex Laskin of the Environmental Molecular Sciences Laboratory (EMSL), a DOE national scientific user facility at PNNL, has deployed his "Time Resolved Aerosol Collectors" (TRAC) at the two ground sites and onboard the G-1 aircraft. Alex's collaborators Dr. Ryan Moffet and Dr. Mary Gilles of Lawrence Berkeley National Laboratory (LBNL) are operating these devices in the field, and they will together analyze the collected aerosols using various microscopic and spectromicroscopic techniques at EMSL and LBNL.
Dr. Claudio Mazzoleni, Assistant Professor, Michigan Tech, and his student Kyle Gorkowski have deployed particle collectors for analysis using a Scanning Electron Microscope to determine the shape and morphology of different types of carbonaceous aerosols.
Dr. Jeff Gaffney, Professor, University of Arkansas, and his students Angie Marchany and Mahbuba Begum have deployed high-volume samplers that collect aerosol particles on filters. They plan to perform radiocarbon dating analysis on their aerosol samples to distinguish between carbonaceous aerosols from fossil fuel combustion (i.e., old carbon) and from biogenic hydrocarbons emitted from trees (i.e., new carbon).
Dr. Alena Kubatova, Associate Professor, University of North Dakota, and her postdoctoral research associate Dr. Haewoo Jeong have also deployed a high-volume sampler at each ground site. They are collecting aerosol particles, which they will analyze to determine the polar and non-polar organic compounds using organic solvent extraction and GC/MS techniques.
Friday, June 25, 2010
After carrying out two back-to-back flights, two days in a row, today was declared a hard down day so aircraft crew can relax and rejuvenate. I took this opportunity to visit the Cool ground site and join Berk Knighton and his student Cody Floerchinger on a short hike along the American Canyon Creek Falls trail. It was a hot and sunny day, but I really enjoyed the hike as the trail was well shaded.
Both Berk and Cody have spotted rattlesnakes in this area several times, and Mikhail Pekour found one right next to the trailers at the Cool site. I was really hoping to see one today. As luck would have it, I didn't see any snakes, but spotted other interesting wildlife, a big frog, a couple of lizards, and several lesser goldfinches and turkey vultures. The highlight was a nice little waterfall and a natural swimming pond at the end of the trail.
Tomorrow is going to be a soft down day, which means the aircraft instrument operators will have access to the aircraft and power so they can calibrate their instruments and perform the necessary maintenance. I have taken this opportunity to have another science meeting to review the data we have collected so far. This will be the last time we will all meet to discuss the data while we are all still here.
Thursday, June 24, 2010
We did two flights yesterday to sample the Sacramento plume as it was transported to the northeast over the course of the day.
Today was another long day with two more back-to-back flights. The morning flight was carried out close to the Carquinez Strait to sample the inflow of aerosols and their precursors from oil refineries along the river and the wider Bay Area emission sources into the Central Valley. The afternoon flight was carried out over Sacramento and to the northeast to again sample the flow of "aged" aerosols and their climate-affecting properties.
In the previous blog entry I had described some of the key instruments that have been deployed in CARES to measure the light scattering and absorption properties of aerosols. Scattering of light by aerosols causes a cooling effect on the atmosphere while absorption of light by certain types of carbonaceous aerosols (black carbon or soot) causes a warming effect on the atmosphere. These are referred to as "direct radiative effects" on climate, because in these processes the aerosols directly affect the amount of sunlight that reaches the surface of the earth and the amount that is reflected back to space.
Under very humid conditions, the available water vapor in the air can condense upon aerosol particles, some of which then grow into relatively bigger cloud droplets of average diameter of 0.02 millimeters (i.e., 100 times bigger than aerosol particles). The process of cloud formation is quite complex and depends greatly on the size of the aerosol particles, the hygroscopicity (solubility) of the chemicals that are present in the particles, and the relative humidity. The bigger and more hygroscopic (i.e., more soluble) the aerosol particles, the more efficient they are in forming cloud droplets. Since cloud droplets are more efficient in scattering sunlight than aerosol particles, this phenomenon is referred to as the "indirect radiative effect" of aerosols on climate.
We have deployed special instruments called "Cloud Condensation Nucleation (CCN) Counters" in CARES that measure the concentrations of aerosol particles that can become cloud droplets under specified humidity conditions. Post-doctoral research associates Dr. Manish Shrivastava and Dr. Naruki Hiranuma of Pacific Northwest National Laboratory are operating these instruments at the American River College and the Cool ground sites, respectively. Manish is also operating another instrument called the "OC-EC Analyzer" from Sunset Laboratory, Inc. at the American River College, while Dr. Nels Laulainen of PNNL is operating another OC-EC unit along with several other instruments at the Cool site. The OC-EC instrument measures the concentrations of organic carbon (OC) and elemental carbon (EC) components of carbonaceous aerosols.
Dr. Jim Barnard of PNNL has deployed an instrument called Multifilter Rotating Shadowband Radiometer (MFRSR) at both the ground sites to measure different types of incoming solar irradiances at multiple wavelengths.
Dr. Jeff Gaffney, Professor, University of Arkansas, has deployed an Ultraviolet MFRSR unit as well at the Cool site.