An August 19 image taken at 1:45 a.m. and provided by the Naval Research Laboratory shows Hurricane Dean on a descending orbit of CloudSat (shown as a red line, coming from the northeast down). CloudSat made a very close crossing to the storm's eye, the dark "dot in the infrared imagery. The radar return (lower panel) shows large red filament structures, powerful convective clouds embedded within the system. You can get a hint of the "eye" as seen by CloudSat in the sudden reduction of bright returns. (Click to enlarge.) (U.S. Naval Research Center)
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CloudSat - a $217 million satellite designed in Colorado to peer deep into clouds for clues on weather and climate - has given scientists around the world a wealth of information since its April 2006 launch.

Despite the enormous number of images of clouds from space, previously there had been little real information about the properties of clouds. CloudSat is the first radar to look vertically at the characteristics of clouds, particularly their water and ice content. That data will help scientists better predict weather patterns and climate changes.

Those improvements will give us more confidence in predicting droughts and severe storms in the future, including the effects of global warming.

CloudSat

A painting of clouds by scientist Graeme Stephens decorated the Delta rocket that carried CloudSat into orbit last year. (Special | CSU)
- designed at Colorado State University in Fort Collins and built by Boulder's Ball Aerospace - flies in NASA's "A-Train" constellation of satellites, maintaining a separation of about 15 seconds from the CALIPSO spacecraft, which carries a laser system called "lidar" to study clouds and aerosols (dust and pollution). The lidar complements the CloudSat radar, in that each is particularly well-suited for studying a certain class of clouds. Together, they give a complete picture of clouds from the thinnest cirrus high in the atmosphere to the thickest, most heavily precipitating clouds.

Since 1993, I have dedicated my career to proposing and implementing the CloudSat mission. Working with NASA's Jet Propulsion Laboratory and my crew at Colorado State University, we saw the immense potential of multi-satellite observations to provide improved data to the scientific community and championed the approach of formation-flying CloudSat with the CALIPSO satellite.

Among some of the new discoveries gathered in the first 12 months of CloudSat's operations:

  • CloudSat research is leading to a promising new technique for estimating the intensity of hurricanes from space. The method could one day supplement existing techniques, assist in designing future tropical cyclone satellite observing systems and improve disaster preparedness and recovery efforts. Developed by scientists at CSU, NASA's Jet Propulsion Laboratory, and the Massachusetts Institute of Technology, the technique uses NASA satellite data, including data from CloudSat, to remotely estimate hurricane intensity.

  • CloudSat has provided the first real information on the fraction of clouds that produce precipitation. Over the Earth's oceans, CloudSat has shown that precipitation is much more common than was previously thought, due to the fact that precipitation over oceans is extremely hard to measure and the light rain that often falls has been completely missed by satellite observations until now. Weather and climate models fail to predict this precipitation, but the CloudSat observations will lead to improvements in the predictions. CloudSat has shown that 15 percent of all oceanic clouds produce rain that falls to the surface.

  • Weather and climate-prediction models predict that the majority of rain that falls comes from deep thunderstorms. CloudSat has revealed that this is not the case, and instead the observations show that a large proportion of rain falls from much shallower clouds.

  • CloudSat has provided new insights on the greenhouse effects of clouds, identifying where and when clouds trap heat in the atmosphere and where and when they increase the amount of heat lost from the atmosphere to space. This dynamic trade-off between heating and cooling is one of the basic controls on global climate and the new knowledge gives scientists better tools to estimate future climate.

    The CloudSat radar also provides observations of clouds over the polar regions during winter. These clouds have been largely invisible to earlier satellite observations because of the lack of sunlight and the difficulty of sensing a difference, from space, between cold clouds and cold ice-covered surfaces. As we are finding out, the polar regions are extremely sensitive to climate warming, and the complex interplay between the polar surface and polar clouds can now be studied for the first time.

    Water is our planet's most precious resource. Through evaporation, water moves from the land surface and ocean to the atmosphere and returns back to the surface in the form of rain and snow. This recirculation of water is known as the water cycle. Not only are clouds one of the most commonly recognized aspects of weather, they are the way that the water cycle transports the fresh water that we depend upon, replenishing the freshwater reservoirs in lakes, rivers, snowpacks and even underground aquifers. Without clouds, our freshwater resources would eventually disappear and all water on this planet would be locked in the saltwater of the oceans.

    Clouds also exert a large influence on the climate of our planet, not only by way of the precipitation they produce but also by altering the Earth's greenhouse effect in ways that are not yet fully understood. It is for these reasons that clouds and their effects on climate are one of the most uncertain aspects of the recent Intergovernmental Panel on Climate Change projections of climate change.

    Perhaps the most urgent issue of climate change is associated with uncertainties of how rainfall and snowfall may change in a warming climate. Will wet regions get wetter and dry regions get drier? Will storms become more frequent and more severe? Answers to these questions depend upon improving our understanding of how clouds form, how much water they carry, what determines when and how much they precipitate, and how precipitation may be influenced by temperature and pollution.

    CloudSat goes a long way toward fulfilling scientists' desire to answer those questions. The data retrieved from the satellite go directly to the Air Force, which then sends all of it to the Cooperative Institute for Research in the Atmosphere, based at CSU. CIRA then processes the data for the scientific community.

    Missions such as CloudSat take a decade or more to conceive, propose, and implement. CloudSat owes its success to the scientific leadership of scientists at Colorado State University; a team of engineers and mission designers at NASA's Jet Propulsion Laboratory in Pasadena, Calif.; spacecraft designers at Ball Aerospace and Technologies Corp. in Boulder; satellite controllers at the U.S. Air Force in Albuquerque, N.M.; and a host of international and interagency scientific collaborators.

    NASA has recently recognized the enormous early success and promise of the CloudSat mission by extending its funding by three years, to 2011. That decision makes CloudSat the only Earth science mission selected by NASA to receive additional funding for enhanced scientific research beyond the mission's original purpose.

    For more on the CloudSat project, go to cloudsat.atmos.colostate.edu, or www.cloudsat.cira.colostate.edu.

    Graeme Stephens is a University distinguished professor at CSU and a principal investigator of the CloudSat mission