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2.2.6. 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:
    1. surface wetness state (wet/dry) based on the calculated surface wetness state and soil moisture.

    2. 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_WinterWet and OHMCode_WinterDry).

Note

  1. 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.

  2. AnOHM is under development in v2018b and should NOT be used!

No.

Column Name

Use

Description

1

Code

L

Code linking to a corresponding look-up table.

2

a1

MU

Coefficient for Q* term [-]

3

a2

MU

Coefficient for dQ*/dt term [h]

4

a3

MU

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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