Observational Simulations in Support of CLARREO Development Collins Group Meeting October 10, 2008

Outline Motivations for & Overview of CLARREO Measurement & Attribution – LW – SW Discussion of Observational Simulations Progress so far …

CLARREO CLARREO = CLimate Absolute Radiance & Refractivity Observatory – Recommended by NRC Decadal Survey Space Studies Board – Measures spectrally-resolved LW & SW – Spectral calibration is central to the mission success Allowing for a meaningful comparison between current and future satellite-based observations

Trend Detection Trend detection with long-term satellite-based datasets has been difficult – MSU/SSU – ERBE/CERES Satellites = $$$, most missions therefore address short-term weather phenomena Monitoring slowly-changing climate variables has only recently become a science priority

Expected Signals in LW & SW Climate system isresponding to CO 2 forcing which will be detectable in distinct spectral regions – Temperature profile: mid-IR – H 2 O profile: NIR, mid-IR, far-IR – Land surface type/albedo: SW – Aerosol: SW – Cloud: SW & LW windows

Instrument Development Flowchart Science requirements motivate general engineering requirements Extensive pre-flight simulations for specifics – Number of satellites – Orbit – Viewing geometry – Active/passive measurements – Spectral coverage and resolution With instrument development, known unknowns vs unknown unknowns.

LW Measurements Spectral coverage: 5 to 50 μm at 1 cm -1 resolution Interferometer with 0.1 K accuracy Calibration derived from: – Redundant blackbodies – Deep-space views Significant heritage from existing instrument suite: CERES, AIRS, IASI

SW Measurements Spectral coverage: 0.3 to 2.0 μm, 15 nm resolution Calibration derived from: – Sun views – Possible use of lamps, hot blackbody for low cal. Long-term SW calibration is uncharted territory

Observational Simulations Overview Instrument specifications From model results (e.g., CCMS3), sufficient info to construct what CLARREO would see – Can CLARREO detect what it is supposed to detect where the underlying signal is known? – Orbit details, spectral coverage & resolution can be explored. Open question: if models are imperfect, can/should engineering requirements be based on them?

Progress So Far Connected MODTRAN with CCSM3 outputs for test spectra