Journal cover Journal topic
Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
Geosci. Model Dev., 7, 1051-1068, 2014
© Author(s) 2014. This work is distributed
under the Creative Commons Attribution 3.0 License.
Model description paper
03 Jun 2014
Earth Orbit v2.1: a 3-D visualization and analysis model of Earth's orbit, Milankovitch cycles and insolation
T. S. Kostadinov1,2,* and R. Gilb1 1Department of Geography and the Environment, 28 Westhampton Way, University of Richmond, Richmond, VA 23173, USA
2Formerly at Earth Research Institute, University of California Santa Barbara, Santa Barbara, CA 93106, USA
*T. S. Kostadinov dedicates this paper to his mother, who first sparked his interest in the magnificent night sky and the science of astronomy, and to his father, who showed him the pivotal importance of mathematics.
Abstract. Milankovitch theory postulates that periodic variability of Earth's orbital elements is a major climate forcing mechanism, causing, for example, the contemporary glacial–interglacial cycles. There are three Milankovitch orbital parameters: orbital eccentricity, precession and obliquity. The interaction of the amplitudes, periods and phases of these parameters controls the spatio-temporal patterns of incoming solar radiation (insolation) and the timing and duration of the seasons. This complexity makes Earth–Sun geometry and Milankovitch theory difficult to teach effectively. Here, we present "Earth Orbit v2.1": an astronomically precise and accurate model that offers 3-D visualizations of Earth's orbital geometry, Milankovitch parameters and the ensuing insolation forcing. The model is developed in MATLAB® as a user-friendly graphical user interface. Users are presented with a choice between the Berger (1978a) and Laskar et al. (2004) astronomical solutions for eccentricity, obliquity and precession. A "demo" mode is also available, which allows the Milankovitch parameters to be varied independently of each other, so that users can isolate the effects of each parameter on orbital geometry, the seasons, and insolation. A 3-D orbital configuration plot, as well as various surface and line plots of insolation and insolation anomalies on various time and space scales are produced. Insolation computations use the model's own orbital geometry with no additional a priori input other than the Milankovitch parameter solutions. Insolation output and the underlying solar declination computation are successfully validated against the results of Laskar et al. (2004) and Meeus (1998), respectively. The model outputs some ancillary parameters as well, e.g., Earth's radius-vector length, solar declination and day length for the chosen date and latitude. Time-series plots of the Milankovitch parameters and several relevant paleoclimatological data sets can be produced. Both research and pedagogical applications are envisioned for the model.

Citation: Kostadinov, T. S. and Gilb, R.: Earth Orbit v2.1: a 3-D visualization and analysis model of Earth's orbit, Milankovitch cycles and insolation, Geosci. Model Dev., 7, 1051-1068, doi:10.5194/gmd-7-1051-2014, 2014.
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