How will climate change influence

evapotranspiration?Matt Roby

Introduction

• Climate change will alter flows of water, energy, and carbon between the biosphere and the atmosphere

• Evapotranspiration = plant transpiration + soil evaporation

• How will projected changes in temperature, land-use, and atmospheric CO2 influence evapotranspiration?

The Midwest is vulnerable to climate change

• Rain-fed agriculture

• Crops selected for a specific climate

• Soil and water quality

Evapotranspiration is the sum of transpiration and evaporation

http://blogs.oregonstate.edu/jonperry/files/2011/07/evapotranspiration1.jpg

How will changing temperature influence evapotranspiration?• Mean air temperature

• Diurnal temperature range

• Growing season duration

Effects of changes in mean air temperature• Atmospheric demand for moisture

• Vapor pressure deficit drives evapotranspiration• 1°C increase in air temperature produces a 6 – 7 % increase in the vapor

pressure deficit• “Thirsty” atmosphere• Increased evapotranspiration

(Kirschbaum 2004)

Decrease in the diurnal temperature range• Midwest: warmer nights• Reduction in diurnal temperature range• Reduction in transpiration rate (Kirschbaum 2004).

Extended growing season

• Longer growing seasons in the Midwest, US

• Potential for increased evapotranspiration

(Bagley et al. 2015)

2049-2068 climate

Effects of land-use change

• Climate change may encourage the expansion of new and different crops with their own biophysical properties• Leaf-area-index (LAI)• Canopy density• Canopy albedo

(Le et al. 2015)

Summary

• Climate change will alter flows of water, energy, and carbon between the biosphere and the atmosphere • Temperature• Land-use change

• Interactive effects• Feedbacks