1 | ;+ |
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2 | ; ================ |
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3 | ; lwdown_clark.pro |
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4 | ; ================ |
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5 | ; |
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6 | ; .. function:: lwdown_clark(sst, qair, cld, tair, ps) |
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7 | ; |
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8 | ; DESCRIPTION |
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9 | ; =========== |
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10 | ; |
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11 | ; Net longwave from the Clark et al. (1974) bulk formula |
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12 | ; Clark, N. E., L. Eber, R. M. Laurs, J. A. Renner, and J. F. T. Saur, |
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13 | ; 1974: Heat exchange between ocean and atmosphere in the |
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14 | ; eastern North Pacific for 1961-71. NOAA Tech. Rep. NMRS |
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15 | ; SSRF-682, National Oceanic and Atmospheric Administration, |
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16 | ; U.S. Department of Commerce, Washington, DC, 108 pp. |
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17 | ; |
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18 | ; See also Gill, p34. |
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19 | ; |
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20 | ; INPUTS |
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21 | ; sst : Sea surface temperature (degC) |
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22 | ; qair: specific humidity (g/kg) |
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23 | ; cld : cloud cover |
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24 | ; tair: surface air temperature (degC) |
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25 | ; ps : surface pressure (mb) |
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26 | ; OUTPUT |
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27 | ; lw : estimated longwave (W/m2) |
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28 | ; |
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29 | ; EVOLUTIONS |
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30 | ; ========== |
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31 | ; |
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32 | ; $Id$ |
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33 | ; |
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34 | ; $URL$ |
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35 | ; |
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36 | ; - fplod 20120319 |
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37 | ; |
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38 | ; * minimal header |
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39 | ; |
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40 | ;- |
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41 | function lwdown_clark, sst,qair,cld,tair,ps |
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42 | ; |
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43 | @common |
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44 | ; |
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45 | eps=.97 ; emissivity of sea-water |
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46 | sig=5.67e-8 ; Stefan-Boltzman constant (W/m2/K4) |
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47 | Ts=(sst+273.15) ; SST in K |
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48 | Ta=(tair+273.15) ; Tair in K |
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49 | q=qair/1000. ; specific humidity (kg/kg) |
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50 | r=q/(1-q) ; Mixing ratio |
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51 | ea=ps*r/(r+.62197) ; Specific humidity into vapor pressure |
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52 | ; |
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53 | lw= eps*sig*Ts^4*(.39-.05*ea^.5)*(1.-.51*cld^2) $ |
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54 | +4.*eps*sig*Ts^3*(Ts-Ta) |
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55 | ; |
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56 | lwup=eps*sig*Ts^4 |
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57 | ; |
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58 | lwdown=lwup-lw |
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59 | ; |
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60 | return, lwdown |
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61 | ; |
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62 | end |
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