Interannual variability patterns of the world’s total column water content: Amazon River basin
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Global trend patterns of yearly mean total column water (TCW) from the European Centre for Medium Range Weather Forecasts (ECMWF) 20th century atmosphere model ERA-20CM (1900–2009) and the currently state-of-the-art reanalysis ERA-Interim (1979–2012) show common features of statistically significant upward trends. Of particular interest appears a pronounced regional dipole pattern of interannual climate variability over the South American continent particularly evident in ERA-Interim data. The trend dipole affects two distinct areas: the Andean Amazon basin and the Northeast Brazil. The target regions are characterized by rising and decreasing water content associated with water vapor convergence (divergence) and upward (downward) mass fluxes, respectively. As expected, local water vapor feedback due to local surface temperature change does to not fully explain this TCW trend dipole; other mechanisms may play a role in establishing the observed feature such as moisture transports and monsoon variability in the last decade. The observed trends of the normalized difference vegetation index (NDVI) during the period 1982–2005 show an increasing greenness that coincides with the moistening of the atmospheric column in the Amazon basin. These results are substantiated by two single-station ground-based GPS measurements of TCW vapor (TCWV) from the two target regions.
KeywordsNormalize Difference Vegetation Index Advanced Very High Resolution Radiometer Advanced Very High Resolution Radiometer International GNSS Service Global Precipitation Climatology Project
We acknowledge the ECMWF for the ERA-Interim data retrieved at their web site http://apps.ecmwf.int/datasets/. We also acknowledge the Earth Observing Laboratory, National Center for Atmospheric Research, University Corporation for Atmospheric Research, 2011: NCAR Global, 2-hourly Ground-Based GPS Precipitable Water. Research Data Archive at the National Center for Atmospheric Research, Computational and Information Systems Laboratory, Boulder, CO [available online at http://rda.ucar.edu/datasets/ds721.1], accessed 9 October 2013. NDVI data have been freely retrieved at the url http://glcf.umd.edu/data/gimms/index.shtml/. GPCP data were provided by the NOAA/ Office of Oceanic and Atmospheric Research/Earth System Research Laboratory (OAR/ESRL) Physical Sciences Division (PSD), Boulder, Colorado, USA, from their web site at http://www.esrl.noaa.gov/psd/. GPCC precipitation data were provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, from their web site at http://www.esrl.noaa.gov/psd/. Support by the Max Planck Society is acknowledged (KF). This is a contribution to the BMBF-Project CarBioCial (BMBF/PTJ; FKZ: 01LL0902J).
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