Pan-spectral observing system simulation experiments of shortwave reflectance and long-wave radiance for climate model evaluation

Abstract

Abstract. Top-of-atmosphere (TOA) spectrally resolved shortwave reflectances and long-wave radiances describe the response of the Earth's surface and atmosphere to feedback processes and human-induced forcings. In order to evaluate proposed long-duration spectral measurements, we have projected 21st Century changes from the Community Climate System Model (CCSM3.0) conducted for the Intergovernmental Panel on Climate Change (IPCC) A2 Emissions Scenario onto shortwave reflectance spectra from 300 to 2500 nm and long-wave radiance spectra from 2000 to 200 cm −1 at 8 nm and 1 cm −1 resolution, respectively. The radiative transfer calculations have been rigorously validated against published standards and produce complementary signals describing the climate system forcings and feedbacks. Additional demonstration experiments were performed with the Model for Interdisciplinary Research on Climate (MIROC5) and Hadley Centre Global Environment Model version 2 Earth System (HadGEM2-ES) models for the Representative Concentration Pathway 8.5 (RCP8.5) scenario. The calculations contain readily distinguishable signatures of low clouds, snow/ice, aerosols, temperature gradients, and water vapour distributions. The goal of this effort is to understand both how climate change alters reflected solar and emitted infrared spectra of the Earth and determine whether spectral measurements enhance our detection and attribution of climate change. This effort also presents a path forward to understand the characteristics of hyperspectral observational records needed to confront models and inline instrument simulation. Such simulation will enable a diverse set of comparisons between model results from coupled model intercomparisons and existing and proposed satellite instrument measurement systems.

Spatial Coverage of Monitoring Networks: A Climate Observing System Simulation Experiment

“…If deseasonalized values were not used, most locations outside of the tropics would correlate strongly with each other-either positively for locations in the same hemisphere or negatively for locations in opposite hemispheres. If satellite data were not available, global model output may have been used, as is often the case for some climate observing system simulation experiments when no data exist (e.g., Andersen et al 2006;Feldman et al 2015).…”

How Does Radiation Code Accuracy Matter?

“…The impacts of parameterrization (approximation) of various aspects of the radiative transfer, such as spectral resolution and vertical resolution, on these radiative quantities have been documented in the aforementioned projects. In rare cases, such validation efforts extend to spectrally resolved radiances (e.g., Feldman et al, 2015;Huang et al, 2007), which affords a stricter and more informative test but at higher computing expenses. These practices have been critical for identifying the deficiency in the radiation models and led to continual improvement of them.…”

Response to Reviewer 1

“…The thin blue and green lines indicate the original data before offsets were corrected to create a continuous record. The success of the analytical effort to combine these three satellite records is confirmed by the good agreement of the merged data set with the zonal mean data derived from ground-based Brewer and Dobson data as part of the WOUDC (World Ozone and UV Data Center, update from Fioletov et al, 2002), which is presented as the thick grey line. GOME-2.…”