A finger to the wind

Mar 06, 2012
Aircraft sampling flight patterns are shown over Central California in this aerial overlay. Researchers collected and analyzed measurements from aircraft sampling, ground-based, and remote-sensing atmospheric data and analyzed them for this study.

Like testing the wind direction before taking flight, researchers led by scientists at Pacific Northwest National Laboratory assessed the meteorological conditions during a large observational study of carbon-containing atmospheric particles in central California. Researchers documented the weather conditions during the study and gauged how these affected the sampled areas on a daily basis. This study provides a large body of foundational information of mixing patterns for future analysis of data from the Carbonaceous Aerosol and Radiative Effects Study (CARES).

The phrase "" often conjures images of black exhaust spewing from the back of a diesel truck or belching from an industrial smoke stack. These sources of soot, a.k.a. , are easily pictured. But carbon is also released from natural, or biogenic, processes not usually visible to the naked eye. As plants and forests grow, they emit volatile chemicals into the atmosphere that react and can form carbon-containing particles. One of the main questions scientists want to answer is what happens when the carbon from human activities, such as industry and transportation, meets and mixes with these natural sources. Knowing the fate of different sources of carbon, and how they mingle and react with each other in the atmosphere, will reveal interactions and their effect on the .

Researchers simulated carbon monoxide (CO) tracers to mimic the flight and in situ observations. The observed (blue) and the simulated (red) CO tracers are binned over 250 meter increments along all of the G-1 flight paths, in percentiles, by altitude. Dots denote 50th percentile, boxes represent the range between 25th and 75th percentile, and lines denote 5th and 95th percentile.

The CARES campaign combined aircraft and ground-based sampling of weather and atmospheric conditions, and . The PNNL G-1 aircraft flew over 67 hours of sampling flights in 21 instances. The NASA B-200 aircraft provided remote sensing of aerosol profiles to complement the G-1 aircraft and ground-based data.

For this study, the purpose of research was threefold. First was to provide an overview of meteorology during the campaign which can be used by other scientists to interpret their data. For this purpose, scientists ran the Forecasting model and emitted unique carbon monoxide tracers from separate cities to trace and document the source of pollutants. Next, they analyzed the model output to look for periods when the atmosphere was dominated by air from Sacramento, or the San Francisco Bay area. A unique feature of the area is that due to thermally driven wind patterns, the Sacramento area is "cleaned out" periodically and then the aerosols build up again. These winds change the aerosol measurements on a daily basis.

Finally, they found that local atmospheric recirculation can create layers of pollution over Sacramento that can be entrained into the lowest part of the atmosphere, the local boundary layer, the next day. Aircraft-based atmospheric measurements were timed for twice a day to capture this phenomenon by specifically looking at the layers above the boundary layer in the morning. They also found that the Sierra mountains trap the urban pollutants and send them back into the valley. This will have an impact on how SOAs are formed.

Their next move is to run the meteorological models with simple tracers, with aerosol field variations and properties. They will allow the aerosols to form and transform within the same meteorology to determine if the model can simulate the observational data. The end game is to develop improved model representations for the aerosol-forming processes such as SOAs.

Explore further: Magnitude-7.2 earthquake shakes Mexican capital

More information: Fast JD, et al. 2011. "Transport and Mixing Patterns Over Central California During the Carbonaceous Aerosol and Radiative Effects Study (CARES)," Atmospheric Chemistry and Physics, 12, 1759-1783. DOI:10.5194/acp-12-1759-2012

add to favorites email to friend print save as pdf

Related Stories

Atmospheric scientists start monthlong air sampling campaign

Jun 02, 2010

More than 60 scientists from a dozen institutions have converged on this urban area to study how tiny particles called aerosols affect the climate. Sending airplanes and weather balloons outfitted with instruments up in the ...

Connecting the dots on aerosol details

Jul 27, 2011

Predicting future climate change hangs on understanding aerosols, considered the fine details in the atmosphere. Researchers at Pacific Northwest National Laboratory and the National Center for Atmospheric ...

Down-and-dirty details of climate modeling

May 04, 2011

For the first time, researchers have developed a comprehensive approach to look at aerosols—those fine particles found in pollution—and their effect on clouds and climate. Scientists from Pacific ...

Recommended for you

Magnitude-7.2 earthquake shakes Mexican capital

Apr 18, 2014

A powerful magnitude-7.2 earthquake shook central and southern Mexico on Friday, sending panicked people into the streets. Some walls cracked and fell, but there were no reports of major damage or casualties.

User comments : 0

More news stories

China says massive area of its soil polluted

A huge area of China's soil covering more than twice the size of Spain is estimated to be polluted, the government said Thursday, announcing findings of a survey previously kept secret.

UN weather agency warns of 'El Nino' this year

The UN weather agency Tuesday warned there was a good chance of an "El Nino" climate phenomenon in the Pacific Ocean this year, bringing droughts and heavy rainfall to the rest of the world.

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...