Details
| Original language | English |
|---|---|
| Pages (from-to) | 249-259 |
| Number of pages | 11 |
| Journal | Geophysical journal international |
| Volume | 195 |
| Issue number | 1 |
| Publication status | Published - Oct 2013 |
| Externally published | Yes |
Abstract
Variations in the degree-2 Stokes coefficients C20, C21 and S21 can be used to understand longand short-termclimate forcing. Herewe derive changes in these coefficients for the period 2003 January-2012 April using Earth rotation data. Earth rotation data contain contributions from motion terms (the effects of winds and currents) and contributions from the effects of mass redistribution. We remove the effects of tides, atmospheric winds and oceanic currents from our data. We compare two different models of atmospheric and oceanic angular momentum for removing the effects of winds and currents: (1) using products from the National Centers for Environmental Prediction and (2) using data from the European Centre for Medium-range Weather Forecasts (ECMWF). We assess the quality of these motion models by comparing the two resulting sets of degree-2 Stokes coefficients to independent degree-2 estimates from satellite laser ranging (SLR), GRACE and a geophysical loading model. We find a good agreement between the coefficients from Earth rotation and the coefficients from other sources. In general, the agreement is better for the coefficientswe obtain by removing winds and currents effects using the ECMWF model. In this case, we find higher correlations with the independent models and smaller scatters in differences. This fact holds in particular for ΔC20 and ΔC21, whereas we cannot observe a significant difference for ΔS21. At the annual and semiannual periods, our Earth rotation derived coefficients agree well with the estimates from the other sources, particularly for ΔC21 and ΔS21. The slight discrepancies we obtain for ΔC20 can probably be explained by errors in the atmospheric models and are most likely the result of an over-/underestimation of the annual and semiannual contributions of atmospheric winds to the length-of-day excitation.
Keywords
- Earth rotation variations, Geopotential theory, Satellite geodesy, Time variable gravity
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)
- Geophysics
- Earth and Planetary Sciences(all)
- Geochemistry and Petrology
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In: Geophysical journal international, Vol. 195, No. 1, 10.2013, p. 249-259.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - An assessment of degree-2 Stokes coefficients from Earth rotation data
AU - Meyrath, T.
AU - van Dam, T.
AU - Weigelt, M.
AU - Cheng, M.
PY - 2013/10
Y1 - 2013/10
N2 - Variations in the degree-2 Stokes coefficients C20, C21 and S21 can be used to understand longand short-termclimate forcing. Herewe derive changes in these coefficients for the period 2003 January-2012 April using Earth rotation data. Earth rotation data contain contributions from motion terms (the effects of winds and currents) and contributions from the effects of mass redistribution. We remove the effects of tides, atmospheric winds and oceanic currents from our data. We compare two different models of atmospheric and oceanic angular momentum for removing the effects of winds and currents: (1) using products from the National Centers for Environmental Prediction and (2) using data from the European Centre for Medium-range Weather Forecasts (ECMWF). We assess the quality of these motion models by comparing the two resulting sets of degree-2 Stokes coefficients to independent degree-2 estimates from satellite laser ranging (SLR), GRACE and a geophysical loading model. We find a good agreement between the coefficients from Earth rotation and the coefficients from other sources. In general, the agreement is better for the coefficientswe obtain by removing winds and currents effects using the ECMWF model. In this case, we find higher correlations with the independent models and smaller scatters in differences. This fact holds in particular for ΔC20 and ΔC21, whereas we cannot observe a significant difference for ΔS21. At the annual and semiannual periods, our Earth rotation derived coefficients agree well with the estimates from the other sources, particularly for ΔC21 and ΔS21. The slight discrepancies we obtain for ΔC20 can probably be explained by errors in the atmospheric models and are most likely the result of an over-/underestimation of the annual and semiannual contributions of atmospheric winds to the length-of-day excitation.
AB - Variations in the degree-2 Stokes coefficients C20, C21 and S21 can be used to understand longand short-termclimate forcing. Herewe derive changes in these coefficients for the period 2003 January-2012 April using Earth rotation data. Earth rotation data contain contributions from motion terms (the effects of winds and currents) and contributions from the effects of mass redistribution. We remove the effects of tides, atmospheric winds and oceanic currents from our data. We compare two different models of atmospheric and oceanic angular momentum for removing the effects of winds and currents: (1) using products from the National Centers for Environmental Prediction and (2) using data from the European Centre for Medium-range Weather Forecasts (ECMWF). We assess the quality of these motion models by comparing the two resulting sets of degree-2 Stokes coefficients to independent degree-2 estimates from satellite laser ranging (SLR), GRACE and a geophysical loading model. We find a good agreement between the coefficients from Earth rotation and the coefficients from other sources. In general, the agreement is better for the coefficientswe obtain by removing winds and currents effects using the ECMWF model. In this case, we find higher correlations with the independent models and smaller scatters in differences. This fact holds in particular for ΔC20 and ΔC21, whereas we cannot observe a significant difference for ΔS21. At the annual and semiannual periods, our Earth rotation derived coefficients agree well with the estimates from the other sources, particularly for ΔC21 and ΔS21. The slight discrepancies we obtain for ΔC20 can probably be explained by errors in the atmospheric models and are most likely the result of an over-/underestimation of the annual and semiannual contributions of atmospheric winds to the length-of-day excitation.
KW - Earth rotation variations
KW - Geopotential theory
KW - Satellite geodesy
KW - Time variable gravity
UR - http://www.scopus.com/inward/record.url?scp=84885721904&partnerID=8YFLogxK
U2 - 10.1093/gji/ggt263
DO - 10.1093/gji/ggt263
M3 - Article
AN - SCOPUS:84885721904
VL - 195
SP - 249
EP - 259
JO - Geophysical journal international
JF - Geophysical journal international
SN - 0956-540X
IS - 1
ER -