TY - JOUR
T1 - A global water cycle reanalysis (2003-2012) merging satellite gravimetry and altimetry observations with a hydrological multi-model ensemble
AU - van Dijk, A. I. J. M.
AU - Renzullo, L. J.
AU - Wada, Y.
AU - Tregoning, P.
PY - 2014/8/1
Y1 - 2014/8/1
N2 - We present a global water cycle reanalysis that merges water balance
estimates derived from the Gravity Recovery And Climate Experiment
(GRACE) satellite mission, satellite water level altimetry and off-line
estimates from several hydrological models. Error estimates for the
sequential data assimilation scheme were derived from available
uncertainty information and the triple collocation technique. Errors in
four GRACE storage products were estimated to be 11-12 mm over land
areas, while errors in monthly storage changes derived from five global
hydrological models were estimated to be 17-28 mm. Prior and posterior
water storage estimates were evaluated against independent observations
of river water level and discharge, snow water storage and glacier mass
loss. Data assimilation improved or maintained agreement overall,
although results varied regionally. Uncertainties were greatest in
regions where glacier mass loss and subsurface storage decline are both
plausible but poorly constrained. We calculated a global water budget
for 2003-2012. The main changes were a net loss of polar ice caps (-342
Gt yr-1) and mountain glaciers (-230 Gt yr-1),
with an additional decrease in seasonal snowpack (-18 Gt
yr-1). Storage increased due to new impoundments (+16 Gt
yr-1), but this was compensated by decreases in other surface
water bodies (-10 Gt yr-1). If the effect of groundwater
depletion (-92 Gt yr-1) is considered separately, subsurface
water storage increased by +202 Gt yr-1 due particularly to
increased wetness in northern temperate regions and in the seasonally
wet tropics of South America and southern Africa. The reanalysis results
are publicly available via www.wenfo.org/wald/.
AB - We present a global water cycle reanalysis that merges water balance
estimates derived from the Gravity Recovery And Climate Experiment
(GRACE) satellite mission, satellite water level altimetry and off-line
estimates from several hydrological models. Error estimates for the
sequential data assimilation scheme were derived from available
uncertainty information and the triple collocation technique. Errors in
four GRACE storage products were estimated to be 11-12 mm over land
areas, while errors in monthly storage changes derived from five global
hydrological models were estimated to be 17-28 mm. Prior and posterior
water storage estimates were evaluated against independent observations
of river water level and discharge, snow water storage and glacier mass
loss. Data assimilation improved or maintained agreement overall,
although results varied regionally. Uncertainties were greatest in
regions where glacier mass loss and subsurface storage decline are both
plausible but poorly constrained. We calculated a global water budget
for 2003-2012. The main changes were a net loss of polar ice caps (-342
Gt yr-1) and mountain glaciers (-230 Gt yr-1),
with an additional decrease in seasonal snowpack (-18 Gt
yr-1). Storage increased due to new impoundments (+16 Gt
yr-1), but this was compensated by decreases in other surface
water bodies (-10 Gt yr-1). If the effect of groundwater
depletion (-92 Gt yr-1) is considered separately, subsurface
water storage increased by +202 Gt yr-1 due particularly to
increased wetness in northern temperate regions and in the seasonally
wet tropics of South America and southern Africa. The reanalysis results
are publicly available via www.wenfo.org/wald/.
U2 - 10.5194/hess-18-2955-2014
DO - 10.5194/hess-18-2955-2014
M3 - Article
SN - 1027-5606
VL - 18
SP - 2955
EP - 2973
JO - Hydrology and Earth System Sciences
JF - Hydrology and Earth System Sciences
IS - 8
ER -