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