Schröder Marc

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  • Article
    Uncertainties in ocean latent heat flux variations over recent decades in satellite-based estimates and reduced observation reanalyses
    (American Meteorological Society, 2020-08-31) Robertson, Franklin R. ; Roberts, Jason B. ; Bosilovich, Michael G. ; Bentamy, Abderrahim ; Clayson, Carol A. ; Fennig, Karsten ; Schröder, Marc ; Tomita, Hiroyuki ; Compo, Gilbert P. ; Gutenstein, Marloes ; Hersbach, Hans ; Kobayashi, Chiaki ; Ricciardulli, Lucrezia ; Sardeshmukh, Prashant ; Slivinski, Laura
    Four state-of-the-art satellite-based estimates of ocean surface latent heat fluxes (LHFs) extending over three decades are analyzed, focusing on the interannual variability and trends of near-global averages and regional patterns. Detailed intercomparisons are made with other datasets including 1) reduced observation reanalyses (RedObs) whose exclusion of satellite data renders them an important independent diagnostic tool; 2) a moisture budget residual LHF estimate using reanalysis moisture transport, atmospheric storage, and satellite precipitation; 3) the ECMWF Reanalysis 5 (ERA5); 4) Remote Sensing Systems (RSS) single-sensor passive microwave and scatterometer wind speed retrievals; and 5) several sea surface temperature (SST) datasets. Large disparities remain in near-global satellite LHF trends and their regional expression over the 1990–2010 period, during which time the interdecadal Pacific oscillation changed sign. The budget residual diagnostics support the smaller RedObs LHF trends. The satellites, ERA5, and RedObs are reasonably consistent in identifying contributions by the 10-m wind speed variations to the LHF trend patterns. However, contributions by the near-surface vertical humidity gradient from satellites and ERA5 trend upward in time with respect to the RedObs ensemble and show less agreement in trend patterns. Problems with wind speed retrievals from Special Sensor Microwave Imager/Sounder satellite sensors, excessive upward trends in trends in Optimal Interpolation Sea Surface Temperature (OISST AVHRR-Only) data used in most satellite LHF estimates, and uncertainties associated with poor satellite coverage before the mid-1990s are noted. Possibly erroneous trends are also identified in ERA5 LHF associated with the onset of scatterometer wind data assimilation in the early 1990s.
  • Article
    Closing the water cycle from observations across scales: where do we stand?
    (American Meteorological Society, 2021-10-01) Dorigo, Wouter ; Dietrich, Stephan ; Aires, Filipe ; Brocca, Luca ; Carter, Sarah ; Cretaux, Jean-François ; Dunkerley, David ; Enomoto, Hiroyuki ; Forsberg, René ; Güntner, Andreas ; Hegglin, Michaela I. ; Hollmann, Rainer ; Hurst, Dale F. ; Johannessen, Johnny A. ; Kummerow, Christian ; Lee, Tong ; Luojus, Kari ; Looser, Ulrich ; Miralles, Diego ; Pellet, Victor ; Recknagel, Thomas ; Vargas, Claudia Ruz ; Schneider, Udo ; Schoeneich, Philippe ; Schröder, Marc ; Tapper, Nigel ; Vuglinsky, Valery ; Wagner, Wolfgang ; Yu, Lisan ; Zappa, Luca ; Zemp, Michael ; Aich, Valentin
    Life on Earth vitally depends on the availability of water. Human pressure on freshwater resources is increasing, as is human exposure to weather-related extremes (droughts, storms, floods) caused by climate change. Understanding these changes is pivotal for developing mitigation and adaptation strategies. The Global Climate Observing System (GCOS) defines a suite of essential climate variables (ECVs), many related to the water cycle, required to systematically monitor Earth’s climate system. Since long-term observations of these ECVs are derived from different observation techniques, platforms, instruments, and retrieval algorithms, they often lack the accuracy, completeness, and resolution, to consistently characterize water cycle variability at multiple spatial and temporal scales. Here, we review the capability of ground-based and remotely sensed observations of water cycle ECVs to consistently observe the hydrological cycle. We evaluate the relevant land, atmosphere, and ocean water storages and the fluxes between them, including anthropogenic water use. Particularly, we assess how well they close on multiple temporal and spatial scales. On this basis, we discuss gaps in observation systems and formulate guidelines for future water cycle observation strategies. We conclude that, while long-term water cycle monitoring has greatly advanced in the past, many observational gaps still need to be overcome to close the water budget and enable a comprehensive and consistent assessment across scales. Trends in water cycle components can only be observed with great uncertainty, mainly due to insufficient length and homogeneity. An advanced closure of the water cycle requires improved model–data synthesis capabilities, particularly at regional to local scales.