Study of the Effect of Temporal Sampling Frequency on DSCOVR Observations Using the GEOS-5 Nature Run Results (Part I): Earth’s Radiation Budget

Daniel Holdaway,Yuekui Yang

doi:10.3390/rs8020098

Abstract

Satellites always sample the Earth-atmosphere system in a finite temporal resolution. This study investigates the effect of sampling frequency on the satellite-derived Earth radiation budget, with the Deep Space Climate Observatory (DSCOVR) as an example. The output from NASA’s Goddard Earth Observing System Version 5 (GEOS-5) Nature Run is used as the truth. The Nature Run is a high spatial and temporal resolution atmospheric simulation spanning a two-year period. The effect of temporal resolution on potential DSCOVR observations is assessed by sampling the full Nature Run data with 1-h to 24-h frequencies. The uncertainty associated with a given sampling frequency is measured by computing means over daily, monthly, seasonal and annual intervals and determining the spread across different possible starting points. The skill with which a particular sampling frequency captures the structure of the full time series is measured using correlations and normalized errors. Results show that higher sampling frequency gives more information and less uncertainty in the derived radiation budget. A sampling frequency coarser than every 4 h results in significant error. Correlations between true and sampled time series also decrease more rapidly for a sampling frequency less than 4 h.

Highlights

Satellite remote sensing remains the only feasible way of observing the Earth on a global scale
Deep Space Climate Observatory (DSCOVR) is equipped with two Earth-observing instruments: the National Institute of Standards and Technology Advanced Radiometer (NISTAR) and the Earth Polychromatic Imaging Camera (EPIC) [1]
The original Nature Run time series provides a suitable substitute of the truth, and a subsampling of the time series with a specific frequency mimics the observations of DSCOVR, or some other satellite

Summary

Introduction

Satellite remote sensing remains the only feasible way of observing the Earth on a global scale. Geophysical parameters retrieved from satellite observations have been playing a critical role in studying the Earth-atmosphere system. Earth’s, the DSCOVR satellite always stays near the Sun-Earth line. DSCOVR is equipped with two Earth-observing instruments: the National Institute of Standards and Technology Advanced Radiometer (NISTAR) and the Earth Polychromatic Imaging Camera (EPIC) [1]. NISTAR views the Earth as one pixel and provides broadband radiation information about the Earth and its atmosphere. EPIC images the Earth with 10 spectral channels ranging from the ultraviolet to the near infrared with it 2048 by 2048 CCD array. Combined information from the Remote Sens. 2016, 8, 98; doi:10.3390/rs8020098 www.mdpi.com/journal/remotesensing

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Results

Conclusion