Monthly gravity field models derived from GRACE Level 1B data using a modified short‐arc approach

Abstract

In this study, a new time series of Gravity Recovery and Climate Experiment (GRACE) monthly solutions, complete to degree and order 60 spanning from January 2003 to August 2011, has been derived based on a modified short-arc approach. Our models entitled Tongji-GRACE01 are available on the website of International Centre for Global Earth Models (http://icgem.gfz-potsdam.de/ICGEM/). The traditional short-arc approach, with no more than 1 h arcs, requires the gradient corrections of satellite orbits in order to reduce the impact of orbit errors on the final solution. Here the modified short-arc approach has been proposed, which has three major differences compared to the traditional one: (1) All the corrections of orbits and range rate measurements are solved together with the geopotential coefficients and the accelerometer biases using a weighted least squares adjustment; (2) the boundary position parameters are not required; and (3) the arc length can be extended to 2 h. The comparisons of geoid degree powers and the mass change signals in the Amazon basin, the Antarctic, and Antarctic Peninsula demonstrate that our model is comparable with the other existing models, i.e., the Centre for Space Research RL05, Jet Propulsion Laboratory RL05, and GeoForschungsZentrum RL05a models. The correlation coefficients of the mass change time series between our model and the other models are better than 0.9 in the Antarctic and Antarctic Peninsula. The mass change rates in the Antarctic and Antarctic Peninsula derived from our model are À92.7 ± 38.0 Gt/yr and À23.9 ± 12.4 Gt/yr, respectively, which are very close to those from other three models and with similar spatial patterns of signals.

A comparative study of changes in the Lambert Glacier/Amery Ice Shelf system, East Antarctica, during 2004–2008 using gravity and surface elevation observations

“…We eliminated these inter-coefficient correlations using a two-step filtering procedure. The first step involves the method of Chen andothers (2007, 2009), which removes the correlation noise at spherical harmonic orders of eight or more. This method fits a third-order polynomial to a set of even or odd coefficients corresponding to each order.…”

Mass Flux Solution in the Tibetan Plateau Using Mascon Modeling

“…In this paper, the GRACE monthly gravity field models, i.e., CSR RL05 [29], JPL RL05 [30], GFZ RL05a [31], and Tongji-GRACE02 (Tongji University, Shanghai, China) [32] are used. All C 20 terms and their uncertainties derived from the GRACE monthly solutions are replaced by those from satellite laser ranging data [33].…”

“…Tongji-GRACE02 models were developed with modified short-arc approach by modeling the non-conservative acceleration and attitude observation errors [33], while other groups apply a dynamic approach [30][31][32]. Chen et al suggested that the difference between Tongji-GRACE02 models and others models is contributed by the modeling of the acceleration and attitude data errors, which may absorb parts of signals [65].…”

Tongji-GRACE01: A GRACE-only static gravity field model recovered from GRACE Level-1B data using modified short arc approach

“…In the modified short arc approach proposed by Shen et al (2013) and Chen et al (2015a), the gravity field parameters are estimated together with the orbit correction vector in one step. The satellite's position vector is expressed as kinematic or reduced dynamic orbit vector plus its correction vector as follows,…”

“…However, the main disadvantage is that the orbit corrections and the gravity field model were calculated separately. Thereby, a modified short arc approach in which the orbit corrections and the gravity field model were solved in one step, was presented by Shen et al (2013) and implemented in the SAtellite Gravimetry Analysis Software (SAGAS) by Tongji University, and then was applied by Chen et al (2015a) to derive time-variable gravity field models. In this paper, using this modified short arc approach, we develop the static gravity field model Tongji-GRACE01 from 49 months of real GRACE Level-1B observations over the period [2003][2004][2005][2006][2007] .…”