Seasonal water storage change of the Yangtze River basin detected by GRACE

Abstract

US-Germany co-sponsered satellite gravimetry mission GRACE (Gravity Recovery And Climate Experiment), launched in March 2002, has been producing monthly time series of Earth gravity models up to degree and order of 120. The GRACE mission consists of two identical satellites flying on an almost polar orbit with an altitude of about 300-500 km and satelite-to-satellite ranging of about 220 km. Thanks to the payloads of space-borne GPS receivers, accelerometers and high-precision K-band satelite-to-satellite ranging mesurements, GRACE gravity models are expected to achieve more than one order of magnitude of improvement over previous models at spatial scales of a few hundred kilometers or larger. Recovery of surface mass re-distribution based on GRACE's time-varying gravity models is applied to studies in solid Earth geophysics, oceanography, climatology and geodesy. At secular time scales, GRACE is expected to provide valuable information on global ice changes, whose variations have profound influences on global climate, and in particular, on sea level changes. At seasonal time scales, GRACE is expected to reveal surface water changes with an accuracy of less than 1 cm, or ocean bottom pressure changes with an accuracy of less than 1 mbar (1 mbar =10 2 Pa). These surface mass redistribution measurements would impove our understanding of the global and regional mass and energy cycles that are critical to human life. Using 15 GRACE monthly gravity models covering the period from April 2002 to December 2003, this study compares seasonal water storage changes recovered from GRACE data and hydrology models at global and regional scales, with particular focus on the Yangtze River basin of China. Annual amplitude of 3.4 cm of equivalent water height change is found for the Yangtze River basin with maximum in Spring and Autumn, agreeing with two state-of-the-art hydrology models. The differences between GRACE results and model predictions are less than 1-2 cm. We conclude that satellite gravimetry has huge potentials in monitering water storage changes in large river basins such as Yangtze.

Uncertainties of the Gravity Recovery and Climate Experiment time-variable gravity-field solutions based on three-cornered hat method

“…3.2), and each column represents the difference between each time series and the reference. The covariance matrix S of the series of differences is computed as E Q -T A R G E T ; t e m p : i n t r a l i n k -; e 0 0 4 ; 1 1 6 ; 3 7 5 S ¼ covðYÞ; (4) where covð•Þ is the covariance operator. A generic element of S represents either a variance estimate (for i ¼ j) or a covariance estimate (for i ≠ j).…”

“…Yangtze, 4 Volta, 5 Nile, 6 and other river basins. Additional studies from GRACE are related to monitoring the groundwater withdrawal in India 7 and China, 8 contributions of glaciers and ice caps to sea-level rise, 9 and evaluation of naturally and anthropogenically induced variations in water availability in Africa.…”

Variations in water storage in China over recent decades from GRACE observations and GLDAS

“…In China, GRACE data have been compared with several model simulations and used to extract TWS's spatial and temporal variation characteristics as well as its responses to droughts (Duan et al, 2007;Zhong et al, 2009;Wang and Yang, 2013;Hu et al, 2006;Xu et al, 2013;Tang et al, 2013Tang et al, , 2014. The serious TWS depletion in north China has gained much attention in recent years (Su et al, 2011;Moiwo et al, 2009;Feng et al, 2013).…”

Inverting GRACE gravity data for local climate effects

“…Currently, there are ten years of useful and comparable data to analyze interannual (e.g., seasonal) and long-term (e.g., the mass loss in Greenland) changes in our climate system that allow for a better understanding of the global water cycle, and especially of droughts and floods. However, for direct basin (Rodell et al 2004b), the Yangtze river basin (Hu et al 2006), and the Zambezi river basin (Winsemius et al 2006), we can record a concentration on the Amazon river (see, e.g., Chen et al 2006, Chen et al 2009, Chen et al 2010, Fengler et al 2007, Syed et al 2005, Tapley et al 2004), which was observed for different periods of time with different techniques. The Amazon area is the largest water shed on Earth and, thus, has a major influence on the global climate, sea levels, and temperatures.…”