Post on 08-Jan-2017
Pis David Lawrence1, Paul Dirmeyer2,
Ahmed Tawfik1, and Liang Chen2
1National Center for Atmospheric Research, Boulder, COCo-chair CESM Land Model Working Group
2George Mason University
Land-Use Change and Land-Atmosphere Feedback Processes as Regulators of Regional Climate Change
Collaborative Research: EaSM3, NSF/NIFA
Land-Use Change and Land-Atmosphere Feedback Processes as Regulators of Regional Climate Change
Collaborative Research: EaSM3, NSF/NIFA
Problem statement
1. Land-use and land-cover change (LULCC) impacts on climate and weather are significant, but complex and remain uncertain
2. LULCC impacts are likely to be modulated by the tightness of local land-atmosphere coupling, which is itself uncertain
3. Land management can be as impactful as land cover; different types of land management have unique impacts
1. Land-use and land-cover change (LULCC) impacts on climate and weather are significant, but complex and remain uncertain
2. LULCC impacts are likely to be modulated by the tightness of local land-atmosphere coupling, which is itself uncertain
3. Land management can be as impactful as land cover; different types of land management have unique impacts
Problem statement
… as highlighted by LUCID …
de Noblet-Ducoudré et al. 2012, Boisier et al. 2012
• Uncertainty in LULCC impact on temperature larger than for CO2• Models do not agree on sign of impact on evapotranspiration
Earth System Models exhibit wide range of responses to LULCC
Lee et al. 2011
Radiative forcingdue to changes in
albedo
Energy Redistributiondue to changes
in surface roughness
Energy Redistribution due to changes in Bowen ratio
Slide courtesy Liz Burakowski
Diagnosing sources of LULCC impactsIntrinsic biophysical mechanism (IBPM)
Diagnosing dominant mechanisms for land-cover change impact on temperature using paired flux towers
Chen and Dirmeyer, 2016
Method applied to climate model simulationGlobal deforestation
Chen and Dirmeyer2016
CESM1JJA
1. Land-use and land-cover change (LULCC) impacts on climate and weather are significant, but complex and remain uncertain
2. LULCC impacts are likely to be modulated by the tightness of local land-atmosphere coupling, which is itself uncertain
3. Land management can be as impactful as land cover; different types of land management have unique impacts
Problem statement
Land-atmosphere coupling strength modulates deforestation response
Land-atmosphere coupling strength for T
Lorenz et al., 2014
Soil moisture – precipitation feedback in models
Warm colors show positive soil moisture-precipitation feedback
Models show wet soil more rain
Koster et al. 2004
Soil moisture influence on precipitation inconsistent in observations and models
Drier soils have a higher probability of rain in obs…
Soil moisture influence on precipitation inconsistent in observations and models
Taylor et al., 2014
ObsParameterizedExplicit
Models w/o explicit convection show ‘incorrect’ soil moisture precip relationship
Convective triggers• Convective Available Potential Energy (default)• Heated Condensation Framework with subgrid threshold (Tawfik et al. 2016)
- Improved diurnal phase, intensity of precip- Improved propagation of mesoscale complex
* indicates significant change at the 95% confidence level
No significant feedback in the CTRL simulations. With the HCF trigger PRECT↓
Chen et al., 2016; Chen et al., in prep
Representation of convective trigger altersland-cover change response
1. Land-use and land-cover change (LULCC) impacts on climate and weather are significant, but complex and remain uncertain
2. LULCC impacts are likely to be modulated by the tightness of local land-atmosphere coupling, which is itself uncertain
3. Land management can be as impactful as land cover; different types of land management have unique impacts
Problem statement
Land management
Erb et al., GCB, 2016
~80% non-ice land area under land management
~25% non-ice land area undergone anthropogenic land-cover change
Set of land-only historic (1850 – 2014) simulations with one-at-a-time modification of particular aspects of land management
1 Land historical all management2 Year 1700 instead of 1850 start3 No LULCC change4 Alternate land use histories5 No shifting cultivation6 Crop and pasture as unmanaged
grassland7 Crops with crop model but no
irrigation/fertilization8 No irrigation9 No fertilization
10 No wood harvest11 No grazing on pastureland12 No human fire ignition/suppression13 Constant 1850 CO2
14 Constant 1850 climate
Land Use Change ✗✗ ✗
Land Use Model Intercomparison Project (LUMIP) for CMIP6Land management experiments
Lawrence et al., 2016
Corn*
Soy*
Wheat** Sugarcane
Cotton Rice
* Temperate and tropical varieties
CLM-Crop
** Spring wheat only in CLM4.5; Winter variety available in CLM5
Objective
Chen and Dirmeyer, 2016
Objective
Glacier
Lake
River Routing
Runoff
River discharge
Urban
Land Use Change
Wood harvest
Disturbance
Vegetation Dynamics
Growth
CompetitionWetland
CropsIrrigation
Flooding
Understand and quantify the nature of land-atmosphere interactions • as they exist today• as they may be modulated by
the radiatively-driven component of climate change
• as they may evolve with changing land use