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'graph.npt' control

Mon, 04/19/2010 - 7:27am — Kyung
Hi all In the graph.npt section, if the value of 'CDMULT' for 'Total phosphorus, mg/m^3' is 1000, the output unit of 'total phosphorus' is g/m^3 ? Kyung
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Water Quality
Tue, 04/20/2010 - 5:30pm — chris

Hi Kyung, The units will be mg/m^3 for CDMULT=1000. Internally W2 uses units of grams, meters, seconds, and the CDMULT=1000 converts units of g/m^3 to mg/m^3. For example: 1 g/m^3 * 1000 mg/g = 1000 mg/m^3 Chris
Tue, 04/20/2010 - 11:40pm — Kyung

Hi Chris, Thank you for replying. I understand what you explain units in the W2 model. However, I wonder why unit of chlorophyll a(mg/m^3) doesn't need 1000 CDMULT in 'graph.npt'. In the 'graph.npt' file, default value of CDMULT for Chlorophyll a(mg/m^3) is '1.0'. When the output unit of chlorophyll a is mg/m^3, does 1000 values for CDMULT need to convert g/m^3 into mg/m^3? And also, I have another question. I am calbrating chlorophyll a in my model. But the result show that concentration of simulated chlorophyll a is pretty low than measured chlorophyll a concentration(2~3 order difference between simulated and measured). - Input water quality : TDS, SS(g/m^3), PO4(g/m^3), NH4(g/m^3), NO3(g/m^3), L-DOM(g/m^3), R-DOM(g/m^3), L-POM(g/m^3), R-POM(g/m^3), CBOD(g/m^3), Algae(g/m^3), DO(g/m^3) - Chlorophyll-algae ratio[ACHLA]: 100 I'm sorry to bother you. I'm looking forward to your response. Kyung
Wed, 04/21/2010 - 2:23pm — chris

Hi Kyung, Chlorophyll a is treated differently in W2. Because chlorophyll a is calculated by dividing algae (g/m^3) by ACHLA (Ratio between algal biomass and chlorophyll a in terms of mg algae/μg chl a), it already in units of mg/m^3 (or ug/l) and does not need to be multiplied by a CDMULT of 1000. Hope this helps. Chris