Comparisons of atmospheric data and reduction methods for the analysis of satellite gravimetry observations

Abstract

[1] The Gravity Recovery and Climate Experiment (GRACE) derived gravity solutions contain errors mostly due to instrument noise, anisotropic spatial sampling, and temporal aliasing. Improving the quality of satellite gravimetry observations, in terms of using more sensitive sensors and/or increasing the spatial isotropy, has been discussed in the context of the designed scenarios of future satellite gravimetry missions. Temporal aliasing caused by incomplete reducing of background models, however, is still a factor that affects the quality of the gravity field solutions. This paper specifically explores the possible physical, geometrical, and numerical modifications of the three-dimensional (3-D) integration approach to eliminate the high-frequency atmospheric effects from satellite gravimetry observations. The new modified 3-D approach is then applied to compute new sets of atmospheric dealiasing products, using atmospheric fields from the European Centre for Medium-Range Weather Forecasts (ECMWF) operational analysis model and ERA-Interim reanalysis. Impacts of modifications are compared to the prelaunch baseline and the current error-curve of GRACE as well as an error-curve of a Bender-type multiorbit satellite configuration. Specifically, we found that using latitude-dependent radius, latitude-and altitude-dependent gravity accelerations along with numerical modifications have a considerable impact on the 3-D integral. Comparing the new products to those of GRACE Atmosphere and Ocean Dealiasing level-1B shows a nonnegligible difference with respect to the prelaunch baseline of GRACE and a possible Bender-type mission up to harmonic degrees 13 and 50, respectively. A big difference is also found between the derived dealiasing products from ECMWF operational analysis and ERA-Interim indicating the importance of input parameters on the final atmospheric dealiasing products.

Estimating and predicting corrections for empirical thermospheric models

“…whereP nm are the fully normalized associated Legendre polynomials, θ and λ are the colatitude and longitude, and dσ is the surface element. We solve this integral numerically following the approach in Forootan et al (2013) and limit the maximum degree and order to 10. Finally, the scale fields can be obtained by synthesizing An example of the updated global thermospheric neutral density of 1 February 2004, 18:00 hr is shown in the Appendix A.…”

Comparison of accelerometer data calibration methods used in thermospheric neutral density estimation

“…These data are used to estimate monthly global albedo and emission fields. Monthly albedo and emission fields are converted to equivalent spherical harmonic coefficients of low degree (< 20) using a numerical integration as in Forootan et al (2013). The temporal evolution of the albedo and emission coefficients are modeled by fitting cyclic functions of sine and cosine with annual and semi-annual frequencies (see also Rodríguez-Solano, 2009).…”

Water Budget Analysis within the Surrounding of Prominent Lakes and Reservoirs from Multi-Sensor Earth Observation Data and Hydrological Models: Case Studies of the Aral Sea and Lake Mead

“…For over 14 years, the time-variable gravity field solutions computed from GRACE data have enabled to study the total mass change at regional and global scales [24][25][26][27]. GRACE has also been used for comparisons, validation and calibration of hydrological models [28][29][30].…”