Time and Place: 10:30 am, Aug.26, 2014. A420 Jupiter Hall on the fourth floor of the Jiuzhang Building, the National Space Science Center.
Title: Monitoring of Climate Change and Greenhouse Gases by Microwave and IR-laser Occultation: Exciting Science and Cooperation Opportunities
Lecturor:
Prof. Gottfried Kirchengast
Wegener Center for Climate and Global Change (WEGC) and Institute for Geophysics, Astrophysics, and Meteorology/Inst. of Physics, University of Graz, Graz, Austria
E-mail: gottfried.kirchengast@uni-graz.at
More information:
Since the pioneering GPS radio occultation (RO) mission GPS/Met in the mid-1990ties, and fostered by many missions since then such as CHAMP, Formosat-3/COSMIC and others, the RO method was firmly established as an essential new Earth remote sensing technique. RO meanwhile provides vital contributions to meteorology, climate, and other fields. Building on this success, a next-generation technique now emerges beyond RO: occultation between Low Earth Orbit (LEO) satellites that uses GPS-type coherent signals at centimeter, millimeter, and micrometer wavelengths. This new technique, termed LEO-LEO microwave and infrared-laser occultation (LMIO), enables to vastly expand from the RO refractivity-based sounding to a complete set of weather and climate variables, including thermodynamic ones (pressure, temperature, water vapor), greenhouse gases, wind speed, and others (Kirchengast and Schweitzer, GRL, 2011;
LMIO combines microwave signals at cm and mm wavelengths (within 8-25 GHz and 175-200 GHz) for thermodynamic state profiling with infrared-laser signals within 2 to 2.5 µm for greenhouse gas and line-of-sight wind profiling; greenhouse gases include water vapor (H2O), the three key long-lived ones (CO2, CH4, N2O) and others. I will present the scientific and technical fundamentals and discuss the estimated performance of LMIO-based atmospheric profiling, including from quasi-realistic end-to-end performance simulations and considering also clouds and aerosols. To indicate the performance, we found monthly-mean profiles accurate to <0.1 to 0.2 K (temperature), <0.15 to 0.5 % (greenhouse gases, e.g., CO2 <1 ppm), and <0.5 m/s (wind speed), respectively, in the upper troposphere and lower stratosphere at about 1 km vertical resolution. I will discuss these results in light of the key promise of LMIO to become an authoritative reference standard for global monitoring of greenhouse gases and climate in Earth’s free atmosphere over the 21st century.
Encouraged by such results we recently also conducted a first ground-based demonstration experiment of IR-laser sounding of greenhouse gases (CO2, CH4, H2O) along a 144 km link at about 2.4 km altitude between the islands of La Palma and Tenerife at the subtropical Canary Islands (28°N/17°W, known for pristine atmospheric conditions). Results show that this basic demonstration was successful; another milestone underlining the promise of LMIO as next-generation technique. I also comment on newest conceptions to complement LMIO during the times between occultation events by nadir-looking IR-laser reflectometry, providing near-surface CO2 and CH4 monitoring for tracking carbon sources and sinks.
Finally, possible collaboration opportunities between WEGC Graz and NSSC Beijing, will be addressed.
