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Land atmosphere interaction –conceptual model exercise. Bart van den Hurk (KNMI/IMAU). Last week. Explore the thermal coupling For instance : Look for a relationship between u and skin conductivity that has roughly the same T a /t using air = 1 (switching off radiation response)

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## Land atmosphere interaction –conceptual model exercise

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**Land atmosphere interaction –conceptual model exercise**Bart van den Hurk (KNMI/IMAU) Example of conceptual land-atmosphere model**Last week**• Explore the thermal coupling • For instance: Look for a relationship between u and skin conductivity that has roughly the same Ta/t using • air = 1 (switching off radiation response) • Ta-Tsoil = 10K (initial gradient) Example of conceptual land-atmosphere model**Layout of a conceptual land-atmosphere hydrology model**Fin Fout P R E ds/dt L Example of conceptual land-atmosphere model**Layout of a conceptual land-atmosphere hydrology model**Stochastic forcing P = 0.5 g(s) (uw/L + E) uw / L + s residual R = ePsr E = Epot sc • = evaporative fraction Q* = net radiation • = precip.efficiency • = runoff efficiency D = soil depth L = horizontal length scale uw = wind speed atm.moisture r, c = coefficients ds/dt = (P-E-R)/D Example of conceptual land-atmosphere model**Stochastic Differential Eq (SDE)**stochastic (forcing) term Discretization and rewriting leads to G = drift term (gains and losses by P, E, R) gr = random term r = Gaussian number with variance 1 and mean 0 Example of conceptual land-atmosphere model**Column structure**Fout = Fin Fin + Fout = Fin Fout = Fin P P P … E E E R R R ds/dt ds/dt ds/dt i=n i=1 i=2 Example of conceptual land-atmosphere model**Parameterization of , E, R**• Precipitation efficiency (s) = a s + b • Evaporation E(s) = Epot sc Epot(i) = linear interpolation between Epot(1) and Epot(n) i = column number, n = nr of columns • Runoff R = P sr Example of conceptual land-atmosphere model**Code list**weak / strong REAL RAEFF 0.0 / 0.2 ! coefficient A in PrecEff = A s + B REAL RBEFF 0.3 / 0.2 ! coefficient B in PrecEff = A s + B REAL RUW 200. ! advection U x W (m/s kg/m2 = kg/m s) REAL RLEN 1000000 ! horizontal length scale (m) REAL RSDEV 0.1 ! Standard deviation of stochastic term ! on UW/L (fraction) REAL RAEPOT 1. ! Epot at first column (m/yr) REAL RBEPOT 2. ! Epot at last column (m/yr) REAL RECOF 0.5 ! Coefficient c in E = Epot s^c REAL RR 0.1 ! Coefficient r in R = e P s^r REAL REPSIL 0.1 ! Coefficient e in R = e P s^r (runoff ! efficiency) REAL RSDEP 0.5 ! Storage reseroir depth (m) REAL RTIME 0.0001 ! Time step length (yr) REAL RZCR 0.01 ! soil saturation below which red noise is ! restricted to postive values REAL RSTMAX 1 ! clipping value of zst REAL RYEAR 10 ! Number of years to simulate INTEGER NCOL 10 ! nr of adjacent columns INTEGER NPPSTEP 1000 ! output interval (nr of steps) Example of conceptual land-atmosphere model**Weak coupling between s and **Example of conceptual land-atmosphere model**Strong coupling between s and **Example of conceptual land-atmosphere model**Soil moisture evolution**weak strong Example of conceptual land-atmosphere model**More information**• Bart van den Hurk • hurkvd@knmi.nl • www.knmi.nl/~hurkvd Example of conceptual land-atmosphere model

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