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3.2.6. SUEWS_OHMCoefficients.txt#
OHM, the Objective Hysteresis Model [Grimmond et al., 1991] calculates the storage heat flux as a function of net all-wave radiation and surface characteristics.
For each surface, OHM requires three model coefficients (a1, a2, a3). The three should be selected as a set.
The SUEWS_OHMCoefficients.txt file provides these coefficients for each surface type.
A variety of values has been derived for different materials and can be found in the literature (see: Typical Values).
- Coefficients can be changed depending on:
surface wetness state (wet/dry) based on the calculated surface wetness state and soil moisture.
season (summer/winter) based on a 5-day running mean air temperature.
To use the same coefficients irrespective of wet/dry and summer/winter conditions, use the same code for all four OHM columns (
OHMCode_SummerWet,OHMCode_SummerDry,OHMCode_WinterWetandOHMCode_WinterDry).
Note
AnOHM (set in RunControl.nml by
StorageHeatMethod= 3) does not use the coefficients specified in SUEWS_OHMCoefficients.txt but instead requires three parameters to be specified for each surface type (including snow): heat capacity (AnOHM_Cp), thermal conductivity (AnOHM_Kk) and bulk transfer coefficient (AnOHM_Ch). These are specified in SUEWS_NonVeg.txt, SUEWS_Veg.txt, SUEWS_Water.txt and SUEWS_Snow.txt. No additional files are required for AnOHM.AnOHM is under development in v2018b and should NOT be used!
No. |
Column Name |
Use |
Description |
|---|---|---|---|
1.0 |
Code linking to a corresponding look-up table. |
||
2.0 |
Coefficient for Q* term [-] |
||
3.0 |
Coefficient for |
||
4.0 |
Constant term [W m-2] |
An example SUEWS_OHMCoefficients.txt can be found below:
1 2 3 4
Code a1 a2 a3 ! Surface type Reference Not recommended (NR)
10 0.71 0.04 -39.7 ! "Canyon (E-W), Japan" Yosheida (1990/91)
11 0.32 0.01 -27.7 ! "Canyon, Vancouver" Nunez (1974)
100 0.515 0.025 -33.7 ! Canyon (average)
200 0.336 0.313 -31.4 ! "Vegetation (average). This is the average of Codes 20, 30, 50, 51, 52, 53, 60 (i.e. includes soil and water)."
201 0.215 0.325 -19.85 ! NEW Vegetation only (average of codes 20 and 30).
2011 0.230 0.276 -16.91 ! Code 201 x Mulitplier for summer
2012 0.270 -0.435 6.62 ! Code 201 x Multiplier for winter
20 0.11 0.11 -12.3 ! Mixed Forest McCaughey (1985)
30 0.32 0.54 -27.4 ! Short grass Doll et al. (1985)
50 0.38 0.56 -27.3 ! Bare soil Novak (1982)
51 0.33 0.07 -34.9 ! Bare soil (wet) Fuchs & Hadas (1972)
52 0.35 0.43 -36.5 ! Bare soil (dry) Fuchs & Hadas (1972)
53 0.36 0.27 -42.4 ! Bare soil Asaeda & Ca (1983)
55 0.355 0.335 -35.275 ! "Bare soil (average). This is the average of Codes 50, 51, 52, 53."
551 0.379 0.284 -30.05 ! Code 55 x Mulitplier for summer
552 0.445 -0.448 11.77 ! Code 55 x Mulitplier for winter
60 0.5 0.21 -39.1 ! Water (shallow - turbid) Souch et al. (1998)
601 0.534 0.178 -33.31 ! Code 60 x Multiplier for summer
602 0.627 -0.281 13.05 ! Code 60 x Multiplier for winter
61 0.25 0.6 -30 ! Snow Jarvi et al. (2014)
713 0.17 0.1 -17 ! "Roof (tar and gravel, summer)" summer
701 0.3 0.96 -24 ! "Roof (commerical or industrial, gravel, dry, WS < 1 m/s, Vancouver)" "Meyn & Oke (2009) Table 4, Pg 750"
702 0.26 0.89 -21 ! "Roof (commerical or industrial, gravel, dry, WS 1-1.4 m/s, Vancouver)" "Meyn & Oke (2009) Table 4, Pg 750"
703 0.23 0.87 -24 ! "Roof (commerical or industrial, gravel, dry, WS 1.5-2 m/s, Vancouver)" "Meyn & Oke (2009) Table 4, Pg 750"
704 0.23 0.69 -21 ! "Roof (commerical or industrial, gravel, wet, WS 0.9-1.9 m/s, Vancouver)" "Meyn & Oke (2009) Table 4, Pg 750"
705 0.06 0.28 -3 ! "Roof (commerical or industrial, bitumen spread over flat industrial membrane, wet & dry, WS 1.1-2 m/s, Vancouver)" "Meyn & Oke (2009) Table 4, Pg 750"
706 0.15 0.28 -6 ! "Roof (residential, asphalt shingle on plywood, dry, WS < 1 m/s, Vancouver)" "Meyn & Oke (2009) Table 4, Pg 750"
707 0.12 0.25 -5 ! "Roof (residential, asphalt shingle on plywood, dry, WS < 1.0-1.4 m/s, Vancouver)" "Meyn & Oke (2009) Table 4, Pg 750"
708 0.1 0.23 -6 ! "Roof (residential, asphalt shingle on plywood, dry, WS < 2 m/s, Vancouver)" "Meyn & Oke (2009) Table 4, Pg 750"
709 0.09 0.18 -1 ! "Roof (STAR, residential, high albedo asphalt shingle, dry, WS 1.0-1.4 m/s)" "Meyn & Oke (2009) Table 4, Pg 750"
710 0.07 0.26 -6 ! "Roof (STAR, Japanese ceramic tile)" "Meyn & Oke (2009) Table 4, Pg 750"
711 0.06 0.43 -4 ! "Roof (STAR, slate tile, dry, WS 1.0-1.4 m/s)" "Meyn & Oke (2009) Table 4, Pg 750"
712 0.07 0.06 -5 ! "Roof (STAR, clay tile, dry, WS 1.0-1.4 m/s)" "Meyn & Oke (2009) Table 4, Pg 750"
750 0.19 0.54 -15.125 ! "Roof (own for SMEAR III, Helsinki)" Jarvi et al. (2014)
751 0.12 0.24 -4.5 ! Own for Montreal suburban (calculated as a average from shingle types) Jarvi et al. (2014)
752 0.26 0.85 -21.4 ! Own for Montreal urban (calculated as a average from gravel) Jarvi et al. (2014)
790 0.44 0.57 -28.9 ! Roof (Uppsala) Taseler (1980) NR
791 0.82 0.34 -55.7 ! Roof (membrane & concrete) Yoshida et al. (1990/91) NR
798 0.477 0.337 -33.87 ! "Rooftop average (of Taesler, Yap and Yoshida, as in Grimmond et al. 1992)" Keogh et al. (2012)
7981 0.510 0.286 -28.85 ! Code 798 x Multiplier for summer
7982 0.598 -0.451 11.30 ! Code 798 x Multiplier for winter
799 0.238 0.427 -16.7 ! Original roof average (inlcudes two not recommended - Meyn 2001 and old Meyn 2001 coefficients)
800 0.719 0.194 -36.6 ! "Impervious (average). This is the average of Codes 801, 802, 901, 902, 903, 905, 906."
801 0.81 0.1 -79.9 ! Concrete Doll et al. (1985)
802 0.85 0.32 -28.5 ! Concrete Asaeda & Ca (1993)
901 0.36 0.23 -19.3 ! Asphalt Narita et al. (1984)
902 0.64 0.32 -43.6 ! Asphalt Asaeda & Ca (1993)
903 0.82 0.68 -20.1 ! Asphalt - check these values? Anandakumar (1998)
905 0.72 0.54 -40.2 ! Asphalt (winter) - check these values? Anandakumar (1998)
906 0.83 -0.83 -24.6 ! Asphalt (summer) - check these values? Anandakumar (1998)
904 0.805 -0.193 -9.39 ! An99 weighted average (all year) - calculated by HCW
907 0.767 0.452 -34.76 ! An99 Apr-Sep weighted average (summer) - calculated by HCW
908 0.843 -0.838 15.98 ! An99 Oct-Mar weighted average (winter) - calculated by HCW
909 0.67 0.493 -47.97 ! An99 August average - calculated by HCW
910 0.718 0.532 -40.81 ! An99 JJA average - calculated by HCW
850 0.665 0.243 -42.825 ! "Impervious (average) excluding all An99 values, i.e. average of Codes 801, 802, 901, 902."
851 0.676 0.300 -42.42 ! "NEW Impervious (average). This is the average of Codes 801, 802, 901, 902, 910." Ward et al. (2015)
8511 0.722 0.255 -36.14 ! Code 851 x Multiplier for summer
8512 0.848 -0.402 14.16 ! Code 851 x Multiplier for winter
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