The Soil Moisture Active/Passive (SMAP) Mission: Monitoring Soil Moisture and Freeze/Thaw State John...
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Transcript of The Soil Moisture Active/Passive (SMAP) Mission: Monitoring Soil Moisture and Freeze/Thaw State John...
The Soil Moisture Active/Passive (SMAP) Mission: Monitoring Soil Moisture and
Freeze/Thaw State
John Kimball,
Global Vegetation Workshop, June 16-19 2009
NTSG, The University of Montana
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SMAP Science ObjectivesSMAP Science Objectives
Primary Science Objectives:
• Global, high-resolution mapping of soil moisture and its freeze/thaw state to: Link terrestrial water, energy and carbon
cycle processes
Estimate global water and energy fluxes at the land surface
Quantify net carbon flux in boreal landscapes
Extend weather and climate forecast skill
Develop improved flood and drought prediction capability
SMAP is one of the four first-tier missions recommended by the NRC Earth Science Decadal Survey Report
Soil moisture and freeze/thaw state are major constraints to land-atmosphere
energy, water & carbon exchange
Source: Nemani et al. 2003. Science 300
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SMAP Instrument & Mission OverviewSMAP Instrument & Mission Overview
• Science Measurements Soil moisture and freeze/thaw state
• Orbit: Sun-synchronous, 6 am/6pm equatorial crossing 670 km altitude
• Instruments: L-band (1.26 GHz) radar
Polarization: HH, VV, HV SAR mode: 1-3 km resolution (degrades over center
30% of swath) Real-aperture mode: 30 x 6 km resolution
L-band (1.4 GHz) radiometer Polarization: V, H, U 40 km resolution
Instrument antenna (shared by radar & radiometer) 6-m diameter deployable mesh antenna Conical scan at 14.6 rpm incidence angle: 40 degrees
Creating Contiguous 1000 km swath Swath and orbit enable 2-3 day revisit
• Mission Ops duration: 2013 launch; 3 year baseline
SMAP has significant heritage from Hydros ESSP mission concept and Phase A studies
Sample SMAP Coverage Plot
Radiometer,Low-Res Radar
High-Res Radar
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““Link Terrestrial Water, Energy and Carbon Link Terrestrial Water, Energy and Carbon Cycle Processes”Cycle Processes”
Do Climate Models Correctly Represent the Land surface Control on Water and Energy Fluxes?
What Are the Regional Water Cycle Impacts of Climate Variability?
Landscape Freeze/Thaw Dynamics Constrain the Boreal Carbon Balance
Water and Energy Cycle
Soil Moisture Controls the Rate of Continental Water and Energy Cycles
Carbon Cycle
Are Northern Land Masses Sources or Sinks for Atmospheric Carbon?
Surface Soil Moisture [% Volume] Measured by L-Band Radiometer
Campbell Yolo Clay Field Experiment Site, California
Soi
l Eva
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tion
Nor
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ized
by
Pot
entia
l Eva
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““Estimate Global Water and Energy Fluxes Estimate Global Water and Energy Fluxes at the Land Surface”at the Land Surface”
Li et al., (2007): Evaluation of IPCC AR4 soil moisture simulations for the second half of the twentieth century, Journal of Geophysical Research, 112.
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ΔSMΔT
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Relative soil moisture changes (%) in IPCC models for scenario from 1960-1999 to 2060-2099
SMAP soil moisture observations will help constrain model parameterizations of surface fluxes and improve model performance
• IPCC models currently exhibit large differences in soil moisture trends under simulated climate change scenarios
• Projections of summer soil moisture change (ΔSM) show disagreements in Sign among IPCC AR4 models
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““Quantify Net Carbon Flux in Boreal Quantify Net Carbon Flux in Boreal Landscapes”Landscapes”
Primary thaw day (DOY)
McDonald et al. (2004): Variability in springtime thaw in the terrestrial high latitudes: Monitoring a major control on the biospheric assimilation of atmospheric CO2 with spaceborne microwave remote sensing. Earth Interactions 8(20), 1-23.
SMAP will provide important information on environmental constraints to land-atmosphere carbon source/sink dynamics. It will provide more than 8-fold increase in spatial resolution over existing moderate resolution microwave sensors.
(r = 0.550; P = 0.042)
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1988 1990 1992 1994 1996 1998 2000
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SSM/I thaw date CO2 Spring drawdown
(r = 0.550; P = 0.042)
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1988 1990 1992 1994 1996 1998 2000
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SSM/I thaw date CO2 Spring drawdown
Th
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y d
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ulti
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Gro
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atm
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O2
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Annual comparison of pan-Arctic thaw date and high latitude growing season onset inferred from atmospheric CO2 concentrations, 1988 – 2001
Mean growing season onset for 1988 – 2002 derived from coarse resolution SSM/I data
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“Extend Weather and Climate Forecast Skill”
Predictability of seasonal climate is dependent on boundary conditions such as sea surface temperature (SST) and soil moisture – Soil moisture is particularly important over continental interiors.
Difference in Summer Rainfall: 1993 (flood) minus
1988 (drought) years
Observations
Prediction driven by SST and soil moisture
Prediction driven by SST
-5 0 +5 Rainfall Difference [mm/day]
(Schubert et al., 2002)With Realistic Soil Moisture
24-Hours Ahead High-Resolution
Atmospheric Model Forecasts
Observed Rainfall0000Z to 0400Z 13/7/96(Chen et al., 2001)
Buffalo CreekBasin
High resolution soil moisture data will improve numerical weather prediction (NWP) over continents by accurately initializing land surface states
Without Realistic Soil Moisture
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““Develop Improved Flood and Drought Develop Improved Flood and Drought Prediction Capability”Prediction Capability”
“…delivery of flash-flood guidance to weather forecast offices are centrally dependent on the availability of soil moisture estimates and observations.”
“SMAP will provide realistic and reliable soil moisture observations that will potentially open a new era in drought monitoring and decision-support.”
Decadal Survey:
• Current Status: Indirect soil moisture indices are based on rainfall and air temperature (by county or ~30 km)
• SMAP Capability: Direct soil moisture measurements – global, 3-day, 10 km resolution
NOAA National Weather Service Operational Flash Flood Guidance (FFG)
Operational Drought Indices Produced by NOAA and National Drought Mitigation Center (NDMC)
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Satellite Global Biospheric Monitoring & The Problem with Clouds…Satellite Global Biospheric Monitoring & The Problem with Clouds…
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SMAP Science, Instrument and Mission RequirementsSMAP Science, Instrument and Mission Requirements
Scientific Measurement Requirements
Instrument Functional Requirements Mission Functional Requirements
Soil Moisture: ~4% volumetric accuracy in top 5 cm for vegetation water content < 5 kg m-2; Hydrometeorology at 10 km; Hydroclimatology at 40 km
L-Band Radiometer: Polarization: V, H, U; Resolution: 40 km; Relative accuracy*: 1.5 K L-Band Radar: Polarization: VV, HH, HV; Resolution: 10 km; Relative accuracy*: 0.5 dB for VV and HH Constant incidence angle** between 35 and 50
Freeze/Thaw State: Capture freeze/thaw state transitions in integrated vegetation-soil continuum with 2-day precision, at the spatial scale of landscape variability (3 km).
L-Band Radar: Polarization: HH; Resolution: 3 km; Relative accuracy*: 0.7 dB (1 dB per channel if 2 channels are used); Constant incidence angle** between 35 and 50
DAAC data archiving and distribution.
Field validation program.
Integration of data products into multisource land data assimilation.
Sample diurnal cycle at consistent time of day Global, 3-4 day revisit Boreal, 2 day revisit
Swath Width: 1000 km Minimize Faraday rotation (degradation factor at L-band)
Orbit: 670 km, circular, polar, sun-synchronous, ~6am/pm equator crossing
Observation over a minimum of three annual cycles
Minimum three-year mission life Three year baseline mission***
* Includes precision and calibration stability, and antenna effects ** Defined without regard to local topographic variation *** Includes allowance for up to 30 days post-launch observatory check-out
SMAP requirements were developed under Hydros and refined through extensive community interaction - The July ’07 NASA SMAP Science Workshop confirmed that these requirements satisfy the SMAP mission science objectives
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Baseline Science Data ProductsBaseline Science Data Products
Data Product Description
L1B_S0_LoRes Low Resolution Radar σo in Time Order
L1C_S0_HiRes High Resolution Radar σo on Earth Grid
L1B_TB Radiometer TB in Time Order
L1C_TB Radiometer TB on Earth Grid
L2/3_F/T_HiRes Freeze/Thaw State on Earth Grid
L2/3_SM_HiRes Radar-only Soil Moisture on Earth Grid
L2/3_SM_40km Radiometer-only Soil Moisture on Earth Grid
L2/3_SM_A/P Radar/Radiometer Soil Moisture on Earth Grid
L4_Carbon Carbon Model Assimilation on Earth Grid
L4_SM_profile Soil Moisture Model Assimilation on Earth Grid
Global Mapping L-Band Radar and Radiometer
High-Resolution and Frequent-Revisit
Science Data
Observations + Models =Value-Added Science Data
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SMAP L4_Carbon product: Land-atmosphere COSMAP L4_Carbon product: Land-atmosphere CO22 exchange exchange
• Motivation/Objectives: Quantify net C flux in boreal landscapes; reduce uncertainty regarding missing C sink on land;
• Approach: Apply a soil decomposition algorithm driven by SMAP L4_SM and GPP inputs to compute land-atmosphere CO2 exchange (NEE);
• Inputs: Daily surface (<5cm) soil moisture & T (L4_SM) & GPP (MODIS/NPP); • Outputs: NEE (primary/validated); Reco & SOC (research/optional);
• Domain: Vegetated areas encompassing boreal/arctic latitudes (≥45°N);
• Resolution: 10x10 km;
• Temporal fidelity: Daily (g C m-2 d-1);
• Latency: Initial posting 12 months post-launch, followed by 14-day latency;
• Accuracy: Commensurate with tower based CO2 Obs. (RMSE ≤ 30 g C m-2 yr-1).
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Prototype L4_C Product ExamplePrototype L4_C Product Example
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1/1 2/10 3/21 4/30 6/9 7/19 8/28 10/7 11/16 12/26
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Carbon Model with AMSR and MODIS BGC Tower
+Source
-Sink
NEE for NSA-OBS Ameriflux Site
L4_C algorithm using MODIS - AMSR-E inputsBIOME-BGC simulations using local meteorologyTower CO2 eddy flux measurement results
C source (+)
C sink (-)
L4_C application using MODIS GPP (MOD17) & AMSR-E (SM & T) inputs. The graph (above) shows 2004 seasonal pattern of daily NEE for a mature boreal conifer stand from L4_C, ecosystem model and tower measurements. SMAP L4_C resolution/sampling will allow characterization of surface processes approaching scale & accuracy of tower flux measurements: ~10km resolution, daily repeat, NEE ≤ 30 g C m-2 yr-1 RMSE. NEE (g C m-2) DOY 177, 2004
>7 4 2 0 -2 -4 <-7
Mean Daily net CO2 Exchange (NEE)
Source: Kimball et al. 2009 TGARS 47.
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Global Biophysical Station Networks
SMAP Calibration and Validation activitiesSMAP Calibration and Validation activities
Pre-launch (2009-2013): - Development, testing & selection of baseline
algorithms;
- Development of algorithm software test-bed for algorithm testing & sensitivity studies;
- Verify algorithm sensitivity & accuracy requirements using available satellite, in situ and model based data & targeted field campaigns;
- Initialization/calibration/optimization of algorithm parameters (e.g. BPLUT, SOC pools);
Post-launch (2013-2015):
- Verify product accuracy through focused field campaigns and global observation networks;
- Model assimilation based value assessment (GMAO, TOPS, CarbonTracker);
Pre-launch L4_C Test using MODIS & AMSR-E Inputs
Kimball et al. TGARS 2009