Paul C. Stoy, Tobias Gerken, Gabe Bromley, Mallory Morgan, Liza Vick. Montana State University

Transcription

1 The role of agricultural management on the flux of water, carbon, and heat to and from Montana agroecosystems: Implications for precipitation processes Paul C. Stoy, Tobias Gerken, Gabe Bromley, Mallory Morgan, Liza Vick Montana State University

2 Acknowledgements Montana Wheat and Barley Committee Montana University System Water Center/USGS NSF EPSCoR TrackII OIA NSF DEB (CAREER) USDA NIFA Hatch

3 Why are parts of the northern North American Great Plains cooling?

4 From Gabe Bromley s presentation (ECMWF ERA 20C) AWRA 2016

5 Observations In the Canadian Prairies over the past 4 decades, Summer Tmax: - 1 C trend Precip: + 10 mm/decade trend -6 W m -2 summer forcing! Anthropogenic warming +2.5 W m -2 Gameda et al., (2007) Betts et al. (2013 a,b)

6 Why? Fallow reduction? In the Canadian Prairies over the past 4 decades, Summer Tmax: - 1 C trend Precip: + 10 mm/decade trend -6 W m -2 summer forcing! Anthropogenic warming +2.5 W m -2 Gameda et al., (2007) Betts et al. (2013 a,b)

7 Summer fallow (Mha) How big is 14 Mha? 16 Canada United States Year Mha 14 Mha (Canada) + 11 Mha (U.S.) = 25 Mha = bigger than the UK!

8 Summer fallow (Mha) The largest changes are in Saskatchewan 16 Canada Saskatchewan Alberta 14 Manitoba Other Year

9 Summer fallow (Mha) and North Dakota (2) (3) (1) Colorado Kansas Montana Nebraska N. Dakota Oklahoma S. Dakota Texas Other Year Is this a win-win-win scenario for regional climate, soil conservation, and income?

10 What are the carbon, water, and heat consequences of fallow?.fallow 2014.WW 2013 SW 2014.Creston ( 15-16).Sun River ( 16).Judith Basin ( 13-14).Bangtail (tomorrow-?).huntley( 15-16)

11 Cumulative F c (g C m -2 ) Carbon uptake or loss depend on crop management Winter Wheat Spring Wheat Fallow Winter Wheat Harvest Spring Wheat Harvest Vick, Stoy, Tang, and Gerken (2016) April May June July Aug Sept A

12 Cumulative ET (mm) Latent Heat Winter Wheat Spring Wheat Fallow Winter Wheat Harvest Spring Wheat Harvest April May June July Aug Sept A Vick, Stoy, Tang & Gerken (2016)

13 Cumulative ET (mm) Cumulative H (MJ m -2 ) Latent Heat Sensible Heat Winter Wheat Spring Wheat Fallow Winter Wheat Harvest Spring Wheat Harvest Winter Wheat Spring Wheat Fallow Winter Wheat Harvest Spring Wheat Harvest 50 0 April May June July Aug Sept A April May June July Aug Sept A Parcels of air that interact with the fallow field are more buoyant Vick, Stoy, Tang & Gerken (2016)

14 Height (m) Consequences for atmospheric boundary layer development 3500 A Nearly 1 km Spring wheat h Fallow h 500 h LCL Spring wheat harvest 0 April May June July Aug Sept Lifted condensation level response to RH changes is important Vick, Stoy, Tang & Gerken (2016)

15 1-D atmospheric boundary layer modeling results are promising

16 Montana is warming at the same rate as the globe

17 Montana s air is getting way more humid! (according to PGF climate dataset) p( SH) MT SH = specific humidity SH (fraction/year) 10-5

18 Plants are very sensitive to atmospheric dryness

19 Soil Moisture Climate change will increase the importance of atmospheric constraints on carbon and water fluxes in terrestrial ecosystems Soil moisture changes are less certain Novick, Ficklin, Stoy et al. (2016) Nature Climate Change (mean of 10 GCMs for 38 FLUXNET sites in North America)

20 Water: more than just a liquid

21 Future work: Regional climate modeling & fallow attribution Business as usual modeling approach Scenario 1 Result G1S1 General (e.g. RCP 2.6) Circula on Scenario 2 Result G1S2 Model 1 (e.g. RCP 4.5) Scenario n Result G1Sn The coupled climate human system Climate* Anthropogenic climate forcing Human system** GCM x Scenario 1 Scenario 2 Result GxS1 Result GxS2 Human response To climate *internal dynamics that are unrelated to humans **internal dynamics that are unrelated to climate Scenario n Result GxSn Synthesis, e.g. IPCC

22 MT versus global precipitation trends Sheffield et al. (2012) Little change in global drought over the past 60 years. Nature doi: /nature11575

23 Background: Imagine an imaginary parcel of air

24 Imagine an imaginary parcel of air It receives heat and moisture from the surface, causing it to rise H LE

25 Imagine an imaginary parcel of air CAPE: Convective available potential energy (J/kg) As it rises, it is subjected to forces CIN: Convective inhibition anti-cape (J/kg)

26 Imagine an imaginary parcel of air The height at which it condenses is called the Lifted condensation level (LCL) PV = nrt

27 Imagine an imaginary parcel of air The maximum height that it reaches under the Influence of the surface alone is the Atmospheric boundary layer (ABL) height

28 Imagine an imaginary parcel of air LCL These two levels have to intersect for convective precipitation to form. ABL Have these processes changed over the past 4-5 decades in MT?

29 Both LCL & ABL will decrease under cooler & more humid conditions LCL ABL

30 CAPE and CIN in the morning

31 2014 Spring Wheat / Fallow comparison: CO 2 flux (unfiltered) Liza Harris June Late July

32 Scanlon & Kustas (2010) offer a method to separate T and E from high-frequency eddy covariance data. Stomatal exchange Non-stomatal exchange Stomatal & non-stomatal exchange Deviation from a correlation of -1 provides evidence about the magnitude of E and T, as well as (net) photosynthesis and respiration

33 Fraction Initial progress: T & E partitioning in a wheat/fallow rotation LE t LE e Hour (June 7, 2013)