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Net Primary Productivity and the Miami Model

I haven't been posting for a while as I now realise. So here a new post about a fairly simple and/but old model to calculate the net primary productivty (NPP), the so called Miami Model (Lieth, 1973):

\[ NPP(T) = 3000(1+\exp(1.315-0.119 T)) \\ NPP(P) = 3000 (1-\exp(-0.000664 P)) \\ NPP = \min(NPP(T),NPP(P)) \]

After reading through the more recent literature, it turns out that the Miami-Model is still regarded as useful proxy for annual NPP. Global NPP observations are available, for example the Terra/MODIS Net Primary Production Yearly L4 Global 1km. But these are currently not available as global data set. Instead you can download all tiles (i.e., chunks of 1km by 1km tiles). I have no idea why, but apparently, nobody is interested in compiling it from the available tile data. (Maybe a topic for another blog post?). Anyways, here is what the annual NPP looks like for a present-day climatology, i.e. the Ten Minute Climatology.

Annual Net Primary Productivity from 10' climatology temperature and precipitation

Here is a simple Python implementation:

import numpy as np
def miami_model(temp,prec,a=3000.,b=1.315,c=0.119,d=0.000664):
    npp_temp = a/(1.+np.exp(b-c*temp))
    npp_prec = a*(1.-np.exp(-d*prec))
    return np.fmin(npp_temp,npp_prec)
Tags: models 2017/11/20
About Mario Krapp
I'm a physicist by training and graduated in Earth System Science.

And I like coding. I've been working with complex computer models ever since my undergrad and I enjoy data exploration and data analysis to gain insights into the underlying principles.

Feel free to contact me.