Climate science, particularly climate prediction, has been stymied by difficult and longstanding problems – mostly related to clouds. Through the present day, our poor understanding of how clouds might change with their changing environment “remains the largest source of uncertainty” in model based projections of future climate (IPCC, 2007).

This difficult problem motivates a two-year field study by the Max Planck Institute for Meteorology (MPI-M), department „Atmosphere in the Earth System“, on the Caribbean island of Barbados starting in early 2010. The study will focus on the interplay between the aerosols, clouds, precipitation and climate as it endeavours to collect the data needed to better test theories and improve models. The specific focus will centre on the question: What controls the distribution and structure of clouds in the trade winds, and by implication their sensitivity to their changing global environment?

In close collaboration with scientists at the Caribbean Institute for Meteorology and Hydrology scientists at the MPI-M in Hamburg will deploy state of the art remote sensing (lidar and cloud radar) instrumentation on a windward bluff of the Island. These will be combined with in situ observations, analysis of satellite observations and observations from the new German research aircraft HALO.

On Barbados the conditions for desired measurements are optimal. The island nation is located in the eastern part of the Caribbean, and the inflowing trades are not disturbed by any land masses. Barbados samples a variety of flow regimes, or cloud forms, mostly segregated by season. Winter and early spring are dominated by trade wind flow with periods of human influence due to biomass burning. Early summer samples the transport of mineral dust originating over the Sahara, while late summer brings bursts of deep tropical convection. An attractive feature of the measurement site is its unique long-term record of dust and aerosol concentrations that has been developed by researchers at the University of Miami.

The field study endeavours to develop a large database through ground-based measurements. This data will be mined to explore relationships between cloud cover and precipitation, ambient meteorological conditions, such as moisture and the aerosol composition and concentration. By making use of this data base, results from previous field campaigns may be generalized, and data from a new generation of active satellite remote sensors (such as CALIPSO, CloudSat, and eventually the European Space Agency EARTHCARE Mission) can be more meaningfully interpreted. The long-range, high-altitude capability and extended endurance of the new German research aircraft HALO affords the possibility of connecting the local measurements to the structure of the trade winds as a whole.

The MPI-M measurements are supported by ongoing activities at the site including: aerosol and meteorological measurements by the University of Miami; meteorological and precipitation measurements by the Caribbean Institute for Meteorology and Hydrology. Cooperation with further partners in this project is planned – including scientists at the MPI for Chemistry in Mainz, Germany, as well as at the Institute for Tropospheric Research (IfT) in Leipzig, Germany, and at the Research Centre in Karlsruhe, Germany. By the end of 2009 the MPI instrumentation should be ready for shipment, with a set-up phase planned for early 2010. This project would not be possible without the close collaboration of scientists at the Caribbean Institute for Meteorology and Hydrology.

Literature:

IPCC, 2007: Summary for policymakers. in S. Solomon, D. Qin, M. Manning, Z. Chen, M. Marquis, K. B. Averyt, M. Tignor and H. Miller, editors, Climate Change 2007: The physical science basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

Contact:

Dr. Lutz Hirsch

Max Planck Institute for Meteorology

Phone: +49 40 41173 206

Email: lutz.hirsch@we dont want spamzmaw.de

Prof. Dr. Bjorn Stevens

Max Planck Institute for Meteorology

Phone: +49 40 41173 422

Email: bjorn.stevens@we dont want spamzmaw.de

June 30, 2009