Archive for April, 2009

Good and Bad Ozone

Thursday, April 23rd, 2009
Chris Boxe
by Chris Boxe
Scientist and Engineer

Oxygen, or O2 on the table of chemical elements, is a vital component for life on Earth. It is the second most abundant gas in Earth’s atmosphere, making up about 21 percent of its volume. On the other hand, its cousin ozone (O3) makes up less than 0.00001 percent. In fact, if all the ozone in Earth’s atmosphere were brought down to the surface, air pressure and temperature conditions would compress ozone into a layer just three millimeters thick, equivalent to two pennies stacked one on top of the other. ! Despite its tiny amount, ozone is also a vital ingredient for life on Earth.

Ozone in fact is vital for life on Earth, but it also has a “bad” side as well - that is, there is both good and bad ozone out there. Good ozone, which accounts for about 91 percent of the ozone in Earth’s atmosphere, is present in the stratosphere, the middle layer in Earth’s atmosphere. This portion of ozone is commonly referred to as the “ozone layer.” The ozone layer absorbs more than 90 percent of the sun’s high-frequency ultraviolet light, which is potentially damaging to life on Earth. Without the ozone layer, this radiation would not be filtered as it reaches the surface of Earth, resulting in detrimental health effects for life on Earth. Among the health effects humans could experience as a result of overexposure to ultraviolet radiation are skin cancers, premature aging of the skin and other skin problems, cataracts and other forms of eye damage, and suppression of our bodies’ immune systems and our skin’s natural defenses.

The troposphere, the part of the atmosphere closest to Earth, contains both good and bad ozone. In the lower troposphere, ozone may serve as an air pollutant since it is a major component of photochemical smog. In the middle troposphere, ozone acts as an atmospheric cleanser, and in the upper troposphere, ozone is a greenhouse gas, which could be bad if concentrations get too high.

artist concept of NASA's Aura spacecraft
The Tropospheric Emission Spectrometer flies aboard NASA’s Aura spacecraft. Image credit: NASA JPL

The Tropospheric Emission Spectrometer, a science instrument onboard NASA’s Aura satellite, is improving our understanding of the good and bad ozone in the troposphere. The spectrometer, which was launched in 2004, provides the first global view of tropospheric ozone and vertical concentrations of ozone, as well as temperature and other important tropospheric features, including carbon monoxide (CO), methane (CH4), water vapor and ammonia (NH3). The instrument has studied the origin and distribution of tropospheric ozone. It has also shed light on how the increasing ozone abundance in the troposphere is affecting air quality on a global scale, as well as ozone’s role in chemical reactions that “clean” the atmosphere, and climate change.

These data are used by scientists to determine the degree to which natural sources, like lightning and plant growth, and human-produced sources, like automobiles, industrial pollution, and biomass burning, contribute to ozone production and chemistry. For example, during summertime in the upper troposphere, where ozone acts as a greenhouse gas, lightning generates much greater amounts of ozone than do human activities, thereby having a big impact on regional pollution. Over the last few years, the spectrometer has obtained global data on ozone and chemicals that participate in ozone formation. The fact that the instrument is able to quantify vertical profiles of ozone improves our understanding of how various reactions taking place at specified heights contribute to ozone chemistry. Similar to ozone, chemicals that participate in its production also exist in tiny amounts. Still, this enables scientists to better understand long-term variations in the quantity, distribution and mixing of many tropospheric gases that have a large impact on climate and air quality.

My role with the instrument is to validate the quality of the most recent ozone measurements, which are taken in a special observation mode, called “stare.” This mode is used to monitor biomass burning events and volcanic activity. I compare measurements taken by an ozonesdone (a lightweight, balloon-borne instrument that measures ozone, air pressure, temperature and humidity as it ascends through the atmosphere) with measurements from the tropospheric spectrometer. We do this so we can demonstrate the accuracy and precision of the instrument’s readings. I am also participating in projects that use the instrument data to better understand the chemistry and transport of pollutants coming from wildfires, such as those that occurred in Australia in December 2006. For the future, I am interested in using the tropospheric spectrometer satellite data for ozone and methane to better quantify the degree to which they contribute to global warming and climate change.

Oceans Up Close - From Space

Thursday, April 2nd, 2009
Jorge Vazquez
by Jorge Vazquez

Not all oceanographers spend their time out on the seas. As a project scientist for the Physical Oceanography Distributed Active Archive Center here at JPL , I study the world’s ocean from my computer, using data from a series of NASA satellites that orbit Earth. These data measure everything from how the ocean changes during an El Nino to how such climatic changes affect local regions like California’s coast.

This kind of precise data was impossible 100 years ago. In fact, scientific and technological advances over the last century have revolutionized the field of oceanography. Today, we gather data both from instruments in the ocean and from satellites in space. These satellite data measure changes in sea surface topography (the ocean surface has changes in elevation, just like the land), ocean surface winds, sea surface temperature and water pressure at the bottom of the ocean. The satellites view the ocean from 700 to 1,300 kilometers (440 to 800 miles) above Earth. Current advanced technologies allow scientists to combine data from different satellites to view ocean conditions in near-real time, only 6 to 12 hours from when the satellite acquires the data. This information can then be sent to researchers and decision makers for use in improving forecasts for hurricanes to the regional and local impacts of ocean phenomena like El Nino and La Nina.

The image shows temperatures off the coast of California in September of 1997 (El Nino).
Image above: Sea surface temperatures in 1997 during El Nino and in 2008, when the waters had returned to more normal conditions.Image credit: NOAA

Examples of satellite data can be seen in these images. The view on the left shows temperatures off the coast of California in September of 1997 (El Nino). On the right, sea surface temperatures from September of 2008 (normal conditions). Notice the warmer temperatures (seen in red) resulting from the 1997-1998 El Nino event. Such temperature changes have direct impacts on local climate and fisheries. These data are leading to a new understanding of how hurricanes get their energy from the ocean. These satellite data also help forecast regional ocean temperatures, which affect local weather.

As technology improves, along with the availability of these data in real time, new opportunities will continue to expand to better understand our planet and its impacts on our lives.