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Global Biomass Variation and its Geodynamic Effects, 1982-1998Redistribution of mass near Earth's surface alters its rotation, gravity field, and geocenter location. Advanced techniques for measuring these geodetic variations now exist, but the ability to attribute the observed modes to individual Earth system processes has been hampered by a shortage of reliable global data on such processes, especially hydrospheric processes. To address one aspect of this deficiency, 17 yrs of monthly, global maps of vegetation biomass were produced by applying field-based relationships to satellite-derived vegetation type and leaf area index. The seasonal variability of biomass was estimated to be as large as 5 kg m(exp -2). Of this amount, approximately 4 kg m(exp -2) is due to vegetation water storage variations. The time series of maps was used to compute geodetic anomalies, which were then compared with existing geodetic observations as well as the estimated measurement sensitivity of the Gravity Recovery and Climate Experiment (GRACE). For gravity, the seasonal amplitude of biomass variations may be just within GRACE'S limits of detectability, but it is still an order of magnitude smaller than current observation uncertainty using the satellite-laser-ranging technique. The contribution of total biomass variations to seasonal polar motion amplitude is detectable in today's measurement, but it is obscured by contributions from various other sources, some of which are two orders of magnitude larger. The influence on the length of day is below current limits of detectability. Although the nonseasonal geodynamic signals show clear interannual variability, they are too small to be detected.
Document ID
20080045480
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Rodell, M.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Chao, B. F.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Au, A. Y.
(Raytheon Information Technology and Scientific Services Greenbelt, MD, United States)
Kimball, J. S.
(Montana Univ. Polson, MT, United States)
McDonald, K. C.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Date Acquired
August 24, 2013
Publication Date
January 1, 2005
Publication Information
Publication: Earth Interactions
Volume: 9
Issue: Paper No. 2
Subject Category
Earth Resources And Remote Sensing
Distribution Limits
Public
Copyright
Other

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