Abstract
The earth reflects a fraction of incident sunlight into the space (the remaining being absorbed by the earth). Some of the reflected sunlight reaches the moon and is further reflected back to the earth. This is called the earthshine and can be observed in the dark portion of the disk of a waxing or waning moon. Since the earthshine comes from sunlight that is first reflected by the earth, the intensity of earthshine is related to the earth's albedo, which is an important parameter concerning the global radiation energy budget. Thus we plan to set up long-term and multi-site earthshine observation in order to monitor the variation of the earth's albedo. The subject of this thesis is on the simulation of earthshine measurements and the earth's albedo, including the calculation of the flux of Earth-reflected sunlight at the moon, and the earth's monthly mean albedo. The purpose of doing simulation is to help us investigate the factors related to earthshine measurement, and to provide us a tool to test methods we will use to estimate the earth's albedo from earthshine measurements. The simulation is based on the angular radiation distribution models for the Earth Radiation Budget Experiments (ERBE), with surface geographical type data and cloud amount data given by the ERBE and the International Satellite Cloud Climatology Project (ISCCP) as the input. The temporal coverage of simulation is from July 1983 to December 2004. We also use satellite shortwave measurements of the ERBE to calculate the earth's monthly mean albedo for comparison with the simulation result. The simulation results are used to test Danjon's method for estimating the earth's monthly mean albedo from earthshine flux, with the outcome showing that it is possible to estimate the earth's albedo variations, especially long-term variations, from earthshine flux using this method.