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CLARREO Science Requirements Review - Achieving Rigor in Mission Concept Design

This document reviews the questions and requirements for the CLARREO mission, designed to provide accurate spectrally resolved solar reflected flux and infrared radiance measurements for climate change research. The mission aims to reduce uncertainties in climate models, enable climate trend detection, and establish calibration traceability. It also highlights the unique role of CLARREO in testing climate models and its contribution to understanding the Earth system's changes and consequences.

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CLARREO Science Requirements Review - Achieving Rigor in Mission Concept Design

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  1. CLARREO Science Questionsand Requirements Review to DateBruce Wielicki, Dave YoungCLARREO Team (meetings, telecons)May 12, 2009 CLARREO Science Team Meeting May 12-15, 2009 Newport News, VA

  2. Baseline Mission from the Decadal Survey • Mission is designed to provide “SI-Traceable” spectrally resolved solar reflected flux and infrared radiance measurements: at accuracy sufficient for decadal climate change • Three satellites in 90° orbits to provide accurate temporal sampling • Instruments • Redundant infrared spectrometers on each of three satellites • 200 - 2000 cm-1 with 1 cm-1 spectral resolution • Nadir viewing with ~100 km FOV • Accuracy goal: 0.1 K (3 ) • Redundant solar spectrometers on the third satellite • 300 - 2000 nm with 15 nm spectral resolution • Accuracy goal: 3 parts per 1000 • GPS radio occultation receivers on each satellite • Calibration standard for CERES, CrIS, IASI • This is the Decadal Survey starting point: the telecons, meetings and studies since are to add rigor to requirements and to achieve a Mission Concept Design and control cost.

  3. CLARREO Reduces Climate Model Uncertainty • Climate sensitivity is likely to be in the range of 1.5 to 4.5°C. • The range of estimates arises from uncertainties in the climate models and their internal feedbacks, particularly those related to clouds and related processes. (Excerpted from IPCC) • CLARREO data will be used to test the realistic range of climate predictions • Reducing the range of future scenarios will enable more informed decisions concerning mitigation and adaptation

  4. Information Content of IR and Solar Spectra

  5. Test for human influence Test climate models CLARREO Enables Climate Trend Detection • CLARREO will provide spectral radiances and refractivities of sufficient accuracy to detect decadal scale climate trends • The documented, verifiable accuracy of the CLARREO data record will enable trend detection with a shorter time record • Unscrambling the trends has been demonstrated for clear-sky IR and GPS Temperature Trends: Error vs. Detection Anderson et. al. 2007

  6. Calibration is the Foundation of CLARREO • CLARREO requires complete calibration traceability during all phases of development through operations on orbit • Demonstrating on-orbit traceability will impact the accuracy of all future climate sensors • Technology can be incorporated into future designs • Operational sensors can be designed to make optimal use of CLARREO intercalibration Dykema et. al. 2008

  7. CLARREO Imperative • Initiate an unprecedented, high accuracy record of climate change that is tested, trusted and necessary to provide sound policy decisions. • Initiate a record of direct observables with the high accuracy and information content necessary to detect long term climate change trends and to test and systematically improve climate predictions. • Observe the SI traceablespectrally resolved radiance and atmospheric refractivity with the accuracy and sampling required to assess and predict the impact of changes in climate forcing variables on climate change.

  8. CLARREO Science Objectives

  9. NASA Earth Science Questions How is the global Earth system changing? What are the primary causes of change in the Earth system? How does the Earth system respond to natural and human-induced changes? What are the consequences for human civilization? How will the Earth system change in the future? CLARREO represents the beginning of a true climate observing system specifically designed with the accuracy required to answer these questions

  10. CLARREO’s Unique Role in Testing Climate Models Climate Models are the scientific hypothesis for how the world works. Most satellite missions attack individual processes in a climate model: Aerosols, Ice, CO2, Clouds…. Divide and conquer. e.g. AIRS/MODIS; A-Train CLARREO verifies the integrated climate model decadal change prediction with crosscutting S.I traceable calibration, IR spectra, solar reflected spectra, GPS… Integrate and test. CLARREO From CLARREO Science Questions Document, October 9, 2008

  11. How do Climate Observing System Simulation Experiments Work?

  12. What is a Decadal Climate Change Benchmark? • A climate change benchmark has 3 major elements: • SI traceability to recognized standards at the accuracy required to rigorously observe decadal change climate signals. • Sampling sufficient to reduce aliasing errors to levels below that of decadal climate change signals. • Information content sufficient to unambiguously relate the benchmark observation to climate change variables, forcings, responses, and/or feedbacks that are critical to understanding and predicting decadal climate change.

  13. CLARREO Science Questions • CLARREO can address climate science questions using one of three methodologies: • Questions that CLARREO will address directly with current technology and without the need for any other observations: primarily mid-infrared spectra. • Questions that CLARREO will address directly with expected definition study and IIP confirmation of recent advances in metrological technology and sampling strategies: primarily solar and far-infrared spectra. • Questions that CLARREO will address in combination with other satellite solar and infrared sensors: mid-IR, far-IR, and solar spectra • Defining what CLARREO is and what it is not • Not a replacement for process missions • Not a replacement for operational sounders • NASA portion of CLARREO is complementary to continuity of TSIS and CERES measurements (NOAA part of CLARREO).

  14. CLARREO Science Questions: Climate Forcing • For each forcing, we ask 2 questions: • How is this forcing changing over time (on a decadal scale)? • How accurately is this forcing change represented in climate models? • Implementation Approach Key • (i) Questions that CLARREO will address directly with current technology and without the need for any other observations • (ii) Questions that CLARREO will address directly with expected definition study and IIP confirmation of recent advances in metrological technology and sampling strategies • (iii) Questions that CLARREO will address in combination with other satellite solar and infrared sensors

  15. CLARREO Science Questions: Climate Response • For each response, we ask 3 questions: • How is this climate response changing over time (on a decadal scale)? • How accurately is this response change represented in climate model projections? • What part of the change is consistent with anthropogenic forcing? Science Impact is a combination of science question importance and uniqueness of CLARREO contribution

  16. CLARREO Science Questions:Climate Feedbacks and Sensitivity • For each feedback, we ask 2 questions: • What is the amplitude of this feedback? • How accurately is this feedback change represented in climate models?

  17. What about "retrievals" in benchmarks? • Radiative transfer is not SI traceable at accuracies of 0.1K (3s) or 0.3% (2s): uncertainties in gas absorption lines/overlap, 3-D radiative transfer, non spherical particles etc. • An instantaneous "retrieval" of temperature, water vapor, and cloud is not possible at these accuracies, even if we had the SI traceable accuracy in the infrared and solar radiances. • But "retrievals" of decadal change are dramatically more linear: they are small perturbations on large ensemble mean fields: these perturbations are inherently linear in the same sense as linear perturbations of nonlinear equations. • Examples of this are used by the climate modeling community to understand decadal change feedbacks: • Radiative perturbation methods (Weatherald and Manabe, 1998, ...) • Radiative kernel method: Soden et al., 2008 • Infrared spectra fingerprinting • Leroy et al., 2008, Huang and Ramaswamy

  18. What about nonlinearity in benchmarks? • Relationships of radiance (infrared or solar) are nonlinearly related to the climate variables of interest (temperature, water vapor, cloud) in a real 3-D instantaneous surface and atmospheric state: especially at accuracy of 0.1K (3s) in the infrared and 0.3% (2s) in the solar. This is the normal weather prediction / process regime. • But at 1000km decadal change scales, they are very linear. They are small decadal change perturbations on large ensemble frequency distributions of nonlinear short time scale physics. This is the decadal climate change regime. • CLARREO decadal climate change OSSEs, and simulations of CLARREO spectra using observations confirm that the linearity for benchmarks holds • a) for individual changes: temperature, humidity, cloud, surface • b) the total decadal change is the simple sum of the individual changes

  19. Requirements Table: Benchmarking Spatial Scales for CLARREO Science: Global, Zonal, Land/Ocean Zonal, regional (TBR) Time Scales for CLARREO Science: Seasonal, Annual, Decadal Requirements Highlighted in Yellow are Driving Requirement for that observation

  20. Requirements Table: Testing Climate Models Spatial Scales for CLARREO Science: Global, Zonal, Land/Ocean Zonal, regional (TBR) Time Scales for CLARREO Science: Seasonal, Annual, Decadal

  21. Requirements Table: Complete View

  22. Summary • Science objectives have two major areas: • Decadal climate change benchmark observations. • Decadal climate change observations needed to test climate model predictions: forcing, feedback uncertainties. • Presentations and discussion will focus on relating the science objectives to measurement requirements. These are elements of the requirements table. Individual documents are also being developed for each requirement. • The goals of this meeting include: • Refine critical science questions and/or remaining studies needed to finalize for MCR, with schedule for completion • Refine observation requirements and/or remaining studies needed to finalize for MCR, with schedule for completion

  23. Backup Slides

  24. Why does CLARREO Impact Climate So Broadly? • CLARREO is the first complete high spectral resolution observation of the earth at climate accuracy. • CLARREO is the first mission to bring climate accuracy calibration to a wide range of other sensors (solar and infrared) through in-space inter-calibration: "NIST in orbit". • The solar and infrared spectra that CLARREO observes are the heart of earth's energy balance, i.e. climate change. • CLARREO is the first mission to focus on climate calibration above space/time/angle sampling: other instruments handle regional sampling. • CLARREO is building on NIST, EOS, and IPCC advances over the last decade in calibration, sampling, validation, remote sensing, and understanding where the "tall poles" are.

  25. CLARREO - Why Now? • The timing of the CLARREO mission (why now?) is a result of recent advances in a wide range of scientific, metrology, and technological research. These recent advances include: • a clearer understanding of the value of decadal change observations at high accuracy in providing the critical testing ground for the accuracy of climate model predictions. • a clearer understanding of the level of uncertainty in climate forcings and feedbacks, • improved accuracy of infrared blackbody sources using phase change temperature measurements as part of highly accurate deep well blackbodies. • improved accuracy of spaceborne spectral and total solar irradiance using active cavity absolute detectors (e.g. SORCE) • factor of 1000 improved sensitivity of active cavity detectors through cryogenic cooling (including mechanical coolers) to low temperatures. • new methods at national physics laboratories developed to increase the accuracy of solar wavelength standards by an order of magnitude. ( SIRCUS ) • greatly increased experience with more accurate high spectral resolution mid-infrared spectrometers and interferometers for temperature, water vapor, and cloud sounding (AIRS, IASI, CrIS spaceborne instruments as well as AERI, NAST-I, HIS, and Intessa ground and airborne instruments. • the first successful Far Infrared interferometer flights on a high altitude balloon (FIRST) • greatly improved methods and understanding of how to accurately intercalibrate instruments in orbit including interferometers, imagers, and broadband radiation budget instruments.

  26. CLARREO - Why Now? • These advances combine to enable CLARREO to be a completely new type of climate mission. • A mission focused on accuracy at decade time scales through two complementary methodologies: spectral radiance benchmarks, and intercalibration of other orbiting sensors. • A mission focused on high spectral resolution and broad spectral coverage throughout the solar and infrared spectrum that drive the Earth’s climate energy system and climate change. • A mission able to leverage its capability across a wide range of climate science disciplines, and satellite earth observing systems. • CLARREO will be the first mission capable of providing an anchor at decade time scales to a climate observing system which is currently an accident of international weather and research observing systems. • Every year we delay is a year lost in beginning that climate observing system.

  27. Improvement and Validation of Climate Models

  28. CLARREO Benchmark Radiance Climate Model OSSEs • CLARREO Mission Objectives include monitoring of climate change using SI-traceable spectral radiance benchmarks at high absolute accuracy • Key benchmark radiance trade studies: • Add CLARREO simulators to major climate models to test CLARREO decadal change spectra signals. • Verify accuracy of simulators using monthly mean properties versus individual time steps. • Approach • Climate OSSE using CLARREO simulator in climate model for decadal change • NCAR, GFDL, and NASA GISS climate models key participants • IR clear-sky already published, IR all-sky underway, Solar is new. • The first use of the OSSE concept with decade to century climate models

  29. How do Climate Observing System Simulation Experiments Work?

  30. CLARREO and Intercalibration • CLARREO will provide a calibration source for the Earth observing system • Calibration requirements for climate addressed by several international organizations: • Global Climate Observing System (GCOS) • Achieving Satellite Instrument Calibration for Climate Change (ASIC3) • Global Spacebased Inter-Calibration System (GSICS) • CEOS Working Group on Calibration / Validation

  31. Additional CLARREO Benefits • Provide the first space-based measurements of the Earth’s far infrared spectrum which is half of the cooling to space and the majority of the water vapor greenhouse. • Dramatically reduce the effects of climate record data gaps

  32. CLARREO Solar Spectral Intercalibration • CLARREO Mission Objectives require that climate variables remotely sensed from space using reflected solar radiation be at accuracies sufficient for detection of decadal change. • Accuracy requirements for decadal change taken from previous reports • A potential method to achieve climate accuracy is for CLARREO to calibrate other sensors. Aqua MODIS, CERES 705km orbit • There are several key intercalibration studies • Does spectral response of filters change enough over time to alias climate change (e.g. MODIS, VIIRS)? • Can CLARREO detect and correct spectral response changes of other sensors? • Can CLARREO achieve sufficient space-time-angle sampling for intercalibration of other • Three approaches • Climate OSSE using CLARREO simulator in climate model for decadal change • Simulate MODIS and VIIRS using Schiamachy in orbit spaceborne spectrometer (< 1nm ; 30 by 60km fov) • Simulate CLARREO using MODIS surface/aerosol/cloud properties + radiative transfer theory (< 1nm ; 1km fov)

  33. CLARREO / CERES Science Connections:Climate Sensitivity Uncertainty Uncertainty in Feedback Defines Climate Sensitivity Uncertainty The Climate Feedback System The skewed tail of high climate sensitivity is inevitable in a feedback system IPCC Mean Sensitivity 2 Reducing uncertainty in predictions of T is critical for public policy since changes in global surface temperature drive changes in sea level and precipitation Feedback Factor, f Current Climate Uncertainty IPCC Climate Feedback Uncertainty T for 2 x CO2 (oC) 0.26 Total Cloud W. Vapor Lapse Rate Surface Albedo Feedback Factor, f Current measured feedback uncertainties result in large uncertainties in predicted T (Roe and Baker, 2007). To = the Earth’s temperature as a simple blackbody The uncertainty in climate feedback is driven by these three components. The feedback for the climate system is f = 0.62 ± 0.26 (2)

  34. CLARREO Requirements Based on Reducing Feedback Uncertainty: Cloud Feedback Example Reducing Climate Uncertainty Requires a More Accurate Measurement of Feedback CLARREO Reduces Climate Uncertainty T for 2 x CO2 (oC) 0.09 Total Cloud W. Vapor Lapse Rate Surface Albedo Feedback Factor, f The high accuracy measurements from CLARREO can constrain predictions of T through improved estimates of the feedback. The accuracy requirement is driven by the goal for climate uncertainty reduction. These feedback uncertainty goals define the CLARREO observation requirements CloudFeedback Uncertainty Goal Defines the Observation Requirement Decadal Trend Observation Requirement The uncertainty goal for feedback factor f sets the observation goal for Net Cloud Radiative Forcing (CRF) at 1.2 Wm-2/K IPCC models predict a 0.2 K / decade warming in the next few decades independent of sensitivity. (because the warming is controlled by the slow ocean response time) Therefore, the Net CRF observation goal is: (1.2 Wm-2/K) * (0.2K/decade) = 0.24 Wm-2/decade

  35. CLARREO Requirements for Cloud Feedback CLARREO Calibration Requirement For Measuring Cloud Feedback CLARREO Sampling Requirement The Net CRF observation goal sets the decadal calibration goal: Net CRF = SW CRF + LW CRF CRF = Clear minus All-Sky TOA Flux Shortwave (SW): 0.24/50 = 0.5% (2) Longwave (LW): 0.24/30 = 0.8% (2) This requirement is four times more accurate than the current SW broadband channel absolute accuracy: Requires overlap for current observations (no gap) and/or Requires CLARREO for future observations (gap OK) • The Net CRF observation goal also sets the sampling requirements • 20+ year record for trend to exceed natural variability • Full swath sampling for low observation sampling noise • 20km FOV or smaller to separate clear and cloud scenes • Solution: CLARREO required to calibrate broadband observations to needed absolute accuracy. CERES provides sampling of the Net CRF decadal change. The Quest Has Just Begun Additional Climate Feedbacks: • A new era of climate Observing System Simulation Experiments (OSSEs), a new era of calibration. • A new methodology for linking climate model uncertainties to observation requirements has been highlighted. • The current large uncertainties in climate feedbacks are not inevitable, nor is large uncertainty in climate sensitivity. CLARREO will likely play a key role. • The example of cloud feedback linked to Net CRF does NOT eliminate the need to separately determine aerosol indirect effect. This remains the largest radiative forcing uncertainty and must be subtracted from the observed decadal change in SW CRF. • Similar climate model and data sampling analyses could be performed for other climate feedbacks • water vapor/lapse rate feedback will require latitude profile and height profile requirements for temperature and humidity. Can be extended to spectral fingerprinting. • surface albedo (e.g. snow/ice) will require latitude dependent requirements • other feedbacks could also be considered in this framework. • climateprediction.net perturbed physics modeling provides an ideal framework to explore the relationships.

  36. Definition Studies Underway • Verify IR and solar spectral benchmarking in cloudy sky conditions, determine accuracy and sampling requirements • Climate OSSE groups, Harvard, LaRC, CU-LASP • IR and solar intercalibration space/time/angle match requirements, spectral resolution/coverage requirements • LaRC, UW, GSFC, JPL • Role of polarization in solar benchmarking and intercalibration • GISS, LaRC, GSFC, CU-LASP • Orbit design to optimize benchmarking and intercalibration goals: inclination, altitude, number of orbits (sampling) • LaRC, Harvard, Climate OSSE groups • Integrate results with science question priorities and with mission cost engineering studies to determine science value/cost trade space in spring 2009. MCR late 2009.

  37. CLARREO and Tier 1 Strategy • Tier 1 Decadal Survey Missions: • Extend and Expand upon current key observations • CLARREO extends broadband CERES and TSIS continuity • CLARREO expands the ability of other sensors to observe decadal climate change by anchoring their calibration • Demonstrates and Initiates New Measurements • CLARREO initiates the first IR and solar spectral benchmarks at the accuracy required for decadal change observation and climate model testing. • CLARREO provides the first Far-Infrared Spectral Measurements to verify the water vapor greenhouse effect and water vapor feedback. • CLARREO provides the calibration anchor for much of the climate observing system: a new “NIST-in-Orbit” capability.

  38. Detector Blackbody Beamsplitter CLARREO Technology Investments • CORSAIR: Calibrated Observations of Radiance Spectra from the Atmosphere in the far-InfraRed (NASA Langley) • Performance goals are 0.1 Kelvin absolute radiometric accuracy (3 standard deviations) over a spectral range from 200 to 2000 cm-1 with a resolution of 1.0 cm-1. • Technologies include • IR detector elements sensitive from 15 to 50 µm that do not require cryogenic cooling • SI traceable blackbody radiance standards for wavelengths beyond 15 µm • Robust optical beamsplitters with continuous high efficiency over the full 200 to 2000 cm-1 spectral range • A New Class of Advanced Accuracy Satellite Instrumentation (AASI) for the CLARREO Mission (Wisconsin / Harvard) • Develop and demonstrate key technologies necessary to measure IR spectrally resolved radiances with ultra-high accuracy (<0.1 K 3 sigma) brightness temperature (at scene temperature) for CLARREO. • Technologies include: • On-orbit Absolute Radiance Standard including Miniature Phase Change Cells • On-orbit Cavity Emissivity Module using quantum cascade laser (QCL) and heated halo reflection • On-orbit Spectral Response Module using QCL • A Hyperspectral Imager to Meet CLARREO Goals of High Absolute Accuracy and On-Orbit SI Traceability (LASP) • Improve radiometric accuracy of visible & Near-Infrared hyperspectral imaging needed for Earth climate studies via cross-calibrations from spectral solar irradiances. • Enable on-orbit end-to-end spatial/spectral imager radiometric calibrations and degradation tracking with 0.2% SI-traceable accuracy

  39. CLARREO Science Workshop • Agenda • The Workshop was organized to focus on 5 critical aspects of CLARREO that will drive mission requirements • S.I. Traceable measurements for climate benchmarking • CLARREO’s role in climate prediction and climate model testing • Temporal and spatial sampling requirements • Applied S.I. traceability (and Instrument Incubator Proposals) • Inter-calibration of operational instruments Using CLARREO • Plans and initial results of specific Pre-Phase A studies targeting these areas were presented and discussed • Additional presentations from NASA HQ, NOAA, NIST, and the Earth Systematic Mission Program Office Summary • Held October 21-23, 2008 in Washington DC • Focus of presentations was on Pre-Phase A work • Also 21 contributed posters from the broader community • Over 100 participants • Included representatives from Academia, Industry, NASA HQ, GSFC, JPL, LaRC, NOAA, NIST, and EUMETSAT • Major participation by climate modeling groups • The meeting successfully met major objectives • Presented results from on-going science trade studies and Instrument Incubator projects for community comment • Clarification of the key science objectives • General consensus concerning CLARREO’s role • Represents the beginning of a true climate observing system • CLARREO complements (does not replace) process missions • Steps Towards Mission Concept Review • Begin new studies focused on identified issues • Mission studies will continue through 2008 and continue in 2009. • Finalize Science Requirements • Using input from this workshop the team will produce a final version of the Science Objectives document by November 30 • Develop draft Level 1 requirements with some basic trades: • Feb: Develop several mission concepts based on these requirements/trades • March: Produce initial cost scenarios for assistance in cost/science prioritization at April team meeting • April team meeting for agreement on Level 1 requirements • Plan for MCR in September/October 2009 • Remaining Challenges • Science Questions finalization and prioritization • Working to clearly state the unique aspect of CLARREO relative to the existing and planned climate observing system • Answering key questions • Temporal and Spatial Sampling • Are accuracy goals based on global, zonal, or regional means? • What are the optimal temporal sampling for both IR and solar? • Solar portion of CLARREO • What constitutes a reflected solar benchmark? • Can we define the accuracy of Intercalibration in the solar? • Incorporating Climate Observing System Simulation results into mission planning

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