erf_surface_moisture Namespace Reference

Enumerations
enum	Component : int {   SoilFactor = 0 , VegetationFraction , CanopyResistanceWithoutVPD , SoilResistance ,   GroundRelativeHumidity , NumComponents }

Functions
AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE amrex::Real	surface_mixing_ratio (const amrex::Real beta, const amrex::Real q_sat, const amrex::Real q_air)
AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE amrex::Real	vapour_deficit_factor (const amrex::Real hs, const amrex::Real q_sat, const amrex::Real q_air)
AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE amrex::Real	canopy_resistance (const amrex::Real r_c_without_vpd, const amrex::Real hs, const amrex::Real q_sat, const amrex::Real q_air)
AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE amrex::Real	aerodynamic_resistance (const amrex::Real z_ref, const amrex::Real z0, const amrex::Real psi_h, const amrex::Real kappa, const amrex::Real u_star)
AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE amrex::Real	surface_layer_aerodynamic_resistance (const similarity_funs &sfuns, const amrex::Real z_ref, const amrex::Real z0, const amrex::Real u_star, const amrex::Real olen, const amrex::Real wind, const amrex::Real wind_min, const amrex::Real kappa, const amrex::Real unset)
AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE amrex::Real	two_source_surface_mixing_ratio (const amrex::Real r_a, const amrex::Real r_c, const amrex::Real r_soil, const amrex::Real f_veg, const amrex::Real q_sat, const amrex::Real rh_ground, const amrex::Real q_air)

Variables
constexpr amrex::Real	no_flux_resistance = amrex::Real(1.0e6)

Detailed Description

Pieces of the surface layer's land surface mixing ratio when the two-stream balance supplies the surface's moisture (erf.radiation.seb_surface_layer_uses_moisture): the surface evaporates at beta times the potential rate, and its mixing ratio is beta * q_sat + (1 - beta) * q_air. Without a soil type, beta is the soil-water factor. With one, the surface mixing ratio comes from two source fluxes instead (two_source_surface_mixing_ratio): bare soil evaporates from its pore air (RH q_sat) through its resistance, and with a vegetation type a canopy transpires from q_sat through its own, each in series with the aerodynamic resistance.

Enumeration Type Documentation

Component

enum erf_surface_moisture::Component : int

Components of the per-column field the balance hands the surface layer (TwoStreamRadiation::seb_surface_moisture): the soil-water factor beta in [0, 1]; with a soil type, the bare-soil resistance [s/m] and the relative humidity of the bare soil's pore air; with a vegetation type as well, the vegetated fraction and the canopy resistance without its vapour-deficit factor [s/m]. Absent pieces are a fraction of 0, resistances of no_flux_resistance (1e6 s/m) and a relative humidity of 1.

Enumerator
SoilFactor
VegetationFraction
CanopyResistanceWithoutVPD
SoilResistance
GroundRelativeHumidity
NumComponents

               : int {
    SoilFactor = 0,
    VegetationFraction,
    CanopyResistanceWithoutVPD,
    SoilResistance,
    GroundRelativeHumidity,
    NumComponents
};

Function Documentation

aerodynamic_resistance()

AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE amrex::Real erf_surface_moisture::aerodynamic_resistance	(	const amrex::Real	z_ref,
		const amrex::Real	z0,
		const amrex::Real	psi_h,
		const amrex::Real	kappa,
		const amrex::Real	u_star
	)

Aerodynamic resistance to the moisture flux between the surface and the reference height [s/m]: max(ln(z_ref / z0) - psi_h, 1) / (kappa u*).

This is the limited CmPsih of the surface layer's surface_temp kernel (ERF_MOSTStress.H), which uses z0 for heat and moisture too. Its q* is kappa (q_air - q_surf) / CmPsih, so the flux is u* q* = (q_air - q_surf) / r_a. u* is floored at 1e-3 m/s.

{
    const amrex::Real cm_psi_h = amrex::max(std::log(z_ref / z0) - psi_h, amrex::Real(1.0));
    return cm_psi_h / (kappa * amrex::max(u_star, amrex::Real(1.0e-3)));
}

Referenced by SLM::solve_ground_skin_temperature(), and surface_layer_aerodynamic_resistance().

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canopy_resistance()

AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE amrex::Real erf_surface_moisture::canopy_resistance	(	const amrex::Real	r_c_without_vpd,
		const amrex::Real	hs,
		const amrex::Real	q_sat,
		const amrex::Real	q_air
	)

The canopy resistance the surface layer uses [s/m]: the balance's resistance without the vapour-deficit factor (TwoStream's seb_canopy_resistance_without_vpd) divided by that factor, capped at no_flux_resistance after the divide (the factor alone can raise it 100-fold).

Parameters

[in]	r_c_without_vpd	canopy resistance without the vapour-deficit factor [s/m]
[in]	hs	the canopy's vapour-deficit parameter [1/(kg/kg)]
[in]	q_sat	saturation mixing ratio at the surface temperature [kg/kg]
[in]	q_air	mixing ratio of the air at the reference height [kg/kg]

{
    // A local copy: amrex::min takes references, which CUDA cannot bind to
    // a namespace constexpr in device code
    const amrex::Real r_max = no_flux_resistance;
    return amrex::min(r_max, r_c_without_vpd / vapour_deficit_factor(hs, q_sat, q_air));
}

Referenced by SurfaceLayer::fill_qsurf_with_skin_moisture().

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surface_layer_aerodynamic_resistance()

AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE amrex::Real erf_surface_moisture::surface_layer_aerodynamic_resistance	(	const similarity_funs &	sfuns,
		const amrex::Real	z_ref,
		const amrex::Real	z0,
		const amrex::Real	u_star,
		const amrex::Real	olen,
		const amrex::Real	wind,
		const amrex::Real	wind_min,
		const amrex::Real	kappa,
		const amrex::Real	unset
	)

The aerodynamic resistance [s/m] the surface layer's moisture flux sees over a land column whose skin temperature the two-stream balance gives it.

Skin coupling needs erf.most.surf_temp, so that flux comes from the surface_temp kernel. Its stability function is Jimenez's psi_h2 at z_ref / L (calc_psi_h2), not Businger-Dyer's psi_h, and it is limited as in aerodynamic_resistance.

The resistance uses the last u* and Obukhov length L. Before the first flux, u* is unset or non-finite, and a neutral first guess is used: u* = kappa max(U, U_min) / max(ln(z_ref / z0), 1), with psi_h2 = 0. An unset, non-finite or zero L also gives psi_h2 = 0.

{
    amrex::Real ustar = u_star;
    amrex::Real psi_h = amrex::Real(0.0);
    if (ustar == unset || !amrex::Math::isfinite(ustar)) {
        ustar = kappa * amrex::max(wind, wind_min) /
                amrex::max(std::log(z_ref / z0), amrex::Real(1.0));
    } else if (olen != unset && amrex::Math::isfinite(olen) && olen != amrex::Real(0.0)) {
        psi_h = sfuns.calc_psi_h2(z_ref / olen);
    }
    return aerodynamic_resistance(z_ref, z0, psi_h, kappa, ustar);
}

Referenced by SurfaceLayer::fill_qsurf_with_skin_moisture().

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surface_mixing_ratio()

AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE amrex::Real erf_surface_moisture::surface_mixing_ratio	(	const amrex::Real	beta,
		const amrex::Real	q_sat,
		const amrex::Real	q_air
	)

Surface mixing ratio of a surface with moisture availability beta: the saturation mixing ratio at the surface temperature where beta = 1, the air's own where beta = 0 (no moisture flux), linear in between. A surface-layer moisture flux proportional to (q_surface - q_air) is then beta times the potential one.

Parameters

[in]	beta	moisture availability, clamped to [0, 1]
[in]	q_sat	saturation mixing ratio at the surface temperature and pressure [kg/kg]
[in]	q_air	mixing ratio of the air at the surface layer's reference height [kg/kg]

{
    const amrex::Real b = amrex::max(amrex::Real(0.0), amrex::min(amrex::Real(1.0), beta));
    return b * q_sat + (amrex::Real(1.0) - b) * q_air;
}

Referenced by SurfaceLayer::fill_qsurf_with_skin_moisture().

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two_source_surface_mixing_ratio()

AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE amrex::Real erf_surface_moisture::two_source_surface_mixing_ratio	(	const amrex::Real	r_a,
		const amrex::Real	r_c,
		const amrex::Real	r_soil,
		const amrex::Real	f_veg,
		const amrex::Real	q_sat,
		const amrex::Real	rh_ground,
		const amrex::Real	q_air
	)

Surface mixing ratio [kg/kg] of a surface whose vegetated fraction f_veg transpires through a canopy resistance r_c from q_sat, and whose bare fraction evaporates through a soil resistance r_soil from its pore air, rh_ground * q_sat (Noah-MP's bare ground), each in series with the aerodynamic resistance r_a:

q_surf = q_air + r_a [ f_veg (q_sat - q_air) / (r_a + r_c)

• (1 - f_veg) (rh_ground q_sat - q_air) / (r_a + r_soil) ],

so that the surface layer's flux (q_surf - q_air) / r_a is the sum of the two. With rh_ground = 1 it is beta q_sat + (1 - beta) q_air with beta = f_veg r_a/(r_a + r_c) + (1 - f_veg) r_a/(r_a + r_soil). Over dry soil q_surf can fall below q_air: the soil then takes up water vapour, as in Noah-MP.

{
    const amrex::Real f = amrex::max(amrex::Real(0.0), amrex::min(amrex::Real(1.0), f_veg));
    const amrex::Real rh = amrex::max(amrex::Real(0.0), amrex::min(amrex::Real(1.0), rh_ground));
    return q_air + r_a * (f * (q_sat - q_air) / (r_a + r_c) +
                          (amrex::Real(1.0) - f) * (rh * q_sat - q_air) / (r_a + r_soil));
}

Referenced by SurfaceLayer::fill_qsurf_with_skin_moisture().

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vapour_deficit_factor()

AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE amrex::Real erf_surface_moisture::vapour_deficit_factor	(	const amrex::Real	hs,
		const amrex::Real	q_sat,
		const amrex::Real	q_air
	)

The vapour-deficit factor of the Jarvis canopy resistance, 1 / (1 + HS * max(0, q_sat - q_air)), floored at 0.01 as in Noah-MP (ResistanceCanopyStomataJarvisMod).

{
    const amrex::Real deficit = amrex::max(amrex::Real(0.0), q_sat - q_air);
    return amrex::max(amrex::Real(0.01), amrex::Real(1.0) / (amrex::Real(1.0) + hs * deficit));
}

Referenced by canopy_resistance().

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Variable Documentation

no_flux_resistance

constexpr amrex::Real erf_surface_moisture::no_flux_resistance = amrex::Real(1.0e6)

inlineconstexpr

The largest resistance [s/m]: a canopy or soil at this resistance does not transpire or evaporate. Noah-MP has no such cap; it keeps the resistances finite.

Referenced by canopy_resistance(), and TwoStreamRadiation::seb_surface_moisture().