The Surface Energy Balance and Turbulent Fluxes. Why The SEB? What and How? SEB components ( Rn , SH, LE, G, B, Tskin , ε , α , examples) ABL (neutral, stable, unstable, Ri , z/L, entrainment, LCL, eddy covariance, bulk formulations, examples) SEB measurements SEB remote sensing
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Bonan, Ch. 13, Ch. 14; Kiehl and Trenberth (1997)
ABL = The part of the troposphere that is directly influenced by the presence of the earth’s surface, and responds to surface forcings with a time scale of about an hour or less. See http://lidar.ssec.wisc.edu/papers/akp_thes/node6.htmhttp://apollo.lsc.vsc.edu/classes/met455/notes/section9/1.html
The potential temperature (θ) of a parcel of air at pressure P is the temperature that the parcel would acquire if adiabatically brought to a standard reference pressure P0 (= 1000 millibars).
where T = the current absolute temperature (in K) of the parcel, R = the gas constant of air, and cp= the specific heat capacity at a constant pressure. See GPC Appendix C for derivations.
θ is a more dynamically important quantity than T. Under almost all circumstances, θincreases upwards in the atmosphere, unlike T which may increase or decrease. θis conserved for all dry adiabatic processes, and as such is an important quantity in the ABL (which is often very close to being dry adiabatic). The dry adiabatic lapse rate: Γd = g/cp = 9.8 °C/km
θis a useful measure of the static stability of the unsaturated atmosphere.
stable, vertical motion is suppressed;
unstable, convection is likely
A parcel with P, T, q Td =? q*=?, RH=?, LCL=? Δq=?
Air flow can be imagined as a horizontal flow of numerous rotating eddies, a turbulent vortices of various sizes, with each eddy having 3D components, including vertical components as well. The situation looks chaotic, but vertical movement of the components can be measured from the tower.
τ = ρCDM Ur2
SH = cpρ CDH Ur[Ts – Ta(zr)]
LE = L ρ CDE Ur[qs – qa(zr)]
CDN = [κ/ ln(zr/z0)]2
CDM = CDN,M fM(RiB)
CDH = CDN,H fH(RiB)
CDE = CDN,E fE(RiB) or Eqn (14.31) in Bonan (2008)
West Palm Beach, Fl energy balance (ly/day) West Palm Beach, Florida is located in a warm and moist climate. Latent energy transfer into the air is greatest during the summer time which is the wettest period of the year, and when net radiation is the highest. During the summer, sensible heat transfer decreases as net radiation is allocated to evaporation and latent heat transfer.
Yuma, AZ energy balance (ly/day)
At the other extreme is Yuma, Arizona, a warm and dry climate. The most noticeable characteristic of this place is the lack of latent heat transfer. Though ample radiation is available here, there is no water to evaporate. Nearly all net radiation is used for sensible heat transfer which explains the hot dry conditions at Yuma.
NCAR CLM: http://www.cgd.ucar.edu/tss/clm/ for global climate modeling and projections
NCEP Noah LSM: for numerical weather predictions
NCAR CLM 3.5
2008 CCSM Distinguished Achievement Award
Niu & Yang, 2003, 2006
Yang et al., 1997, 1999
Niu, Yang, et al., 2005
Niu, Yang, et al., 2007
Yang & Niu, 2003
Collaborators: UT (Z.-L. Yang, G.-Y. Niu, R.E. Dickinson); NCAR (G.B. Bonan, K. Oleson, D. Lawrence)
Explicit diffusive wave overland flow
reservoir routing &
Explicit channel routing
Collaborators: UT (Z.-L. Yang, G.-Y. Niu, D. Maidment), NCAR (Fei Chen, Dave Gochis); NCEP (Mike Ek, Ken Mitchell)
Dynamical Routing Methodologies
1-D ‘Noah’ Community
Land Surface Model
See also other flux measurement networks (e.g., Ameriflux, CarboEurope, Fluxnet Canada, and iLEAPS).