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2.1.2. Biogeophysical and Biogeochemical Processes¶

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Biogeophysical and biogeochemical processes are simulated for each subgrid land unit, column, and plant functional type (PFT) independently and each subgrid unit maintains its own prognostic variables (see section 2.2.1.1 for definitions of subgrid units). The same atmospheric forcing is used to force all subgrid units within a grid cell. The surface variables and fluxes required by the atmosphere are obtained by averaging the subgrid quantities weighted by their fractional areas. The processes simulated include (Figure 2.1.1):

1. Surface characterization including land type heterogeneity and ecosystem structure (Chapter 2.2)

2. Absorption, reflection, and transmittance of solar radiation (Chapter 2.3, 2.4)

3. Absorption and emission of longwave radiation (Chapter 2.4)

4. Momentum, sensible heat (ground and canopy), and latent heat (ground evaporation, canopy evaporation, transpiration) fluxes (Chapter 2.5)

5. Heat transfer in soil and snow including phase change (Chapter 2.6)

6. Canopy hydrology (interception, throughfall, and drip) (Chapter 2.7)

7. Soil hydrology (surface runoff, infiltration, redistribution of water within the column, sub-surface drainage, groundwater) (Chapter 2.7)

8. Snow hydrology (snow accumulation and melt, compaction, water transfer between snow layers) (Chapter 2.8)

9. Stomatal physiology, photosythetic capacity, and photosynthesis (Chapters 2.9 and 2.10)

10. Plant hydraulics (Chapter 2.11)

11. Lake temperatures and fluxes (Chapter 2.12)

12. Glacier processes (Chapter 2.13)

13. River routing and river flow (Chapter 2.14)

14. Urban energy balance and climate (Chapter 2.15)

15. Vegetation carbon and nitrogen allocation (Chapter 2.19)

16. Vegetation phenology (Chapter 2.20)

17. Plant respiration (Chapter 2.17)

18. Soil and litter carbon decomposition (Chapter 2.21)

19. Fixation and uptake of nitrogen (Chapter 2.18)

20. External nitrogen cycling including deposition, denitrification, leaching, and losses due to fire (Chapter 2.22)

21. Plant mortality (Chapter 2.23)

22. Fire ignition, suppression, spread, and emissions, including natural, deforestation, and agricultural fire (Chapter 2.24)

23. Methane production, oxidation, and emissions (Chapter 2.25)

24. Crop dynamics, irrigation, and fertilization (Chapter 2.26)

25. Land cover and land use change including wood harvest (Chapter 2.27)

26. Biogenic volatile organic compound emissions (Chapter 2.29)

27. Dust mobilization and deposition (Chapter 2.30)

28. Carbon isotope fractionation (Chapter 2.31)

Figure 2.1.1 Land biogeophysical, biogeochemical, and landscape processes simulated by CLM (adapted from Lawrence et al. (2011) for CLM5.0).¶