7 May 2007
ESRL scientists are two months from the start of a planned field mission based in Costa Rica, the Tropical Composition, Cloud, and Climate Coupling (TC4) experiment. The effort is an interagency project led by NASA that will take place from ~mid-July to ~mid-August. A major Science Team Meeting at the end of April put the finishing touches on the plans for a suite of instruments to be flown on three major aircraft (the high-altitude NASA ER-2, the NASA WB57-F, and the NASA DC-8), providing measurements from the surface to 20 kilometers altitude. Scientists in the Chemical Sciences Division will have instruments on the NASA WB-57F (the SP2 carbon soot photometer, ozone instruments, and a frost point hygrometer) and the NASA DC-8 (single-particle chemical composition). ESRL's Global Monitoring Division is also fielding instruments to measure trace gases, water vapor, and radiation.
Background: The TC4 mission is aimed at gathering chemical and meteorological measurements for the cold, dry conditions of the upper tropical tropopause (the transition region between troposphere and stratosphere). This extreme environment, with temperatures below 190 K, will test retrieval algorithms for several instruments on the Aura satellite that measure trace gases (High Resolution Dynamic Limb Sounder [HIRDLS], Microwave Limb Sounder [MLS], and Thermal Emission Spectrometer [TES]). In addition, lidar measurements of ozone and temperature from medium-altitude aircraft will provide tropical upper troposphere and lower stratosphere profiles and structure. The mission is the latest in a series of field missions over the last few years that have gathered data to help validate the measurements of instruments onboard the Aura satellite.
Significance: This mission is aimed at understanding climate-cloud-chemistry interactions in the tropical tropopause, a highly active and climate-relevant region of the atmosphere. The research addresses objectives in the Climate Forcing Program of NOAA's Climate Goal.