Toward regional-scale modeling using the two-way nested global model TM5: Characterization of transport using SF6


Journal of Geophysical Research, Vol. 109 – October 12, 2004

I am not going to encourage you to read the source article.  I think that is the first time I am making that suggestion.  There are two main reasons:

  1. it costs $9 to buy it (and you can probably find a better way to spend your 9 bucks)
  2. it is a very difficult read.  I am not a meteorologist but I do have an engineering degree and even I struggled with this.  I know that I have several climate scientists as regular readers and I am sure they would understand much of the article but for the rest of my readers, I expect this is a little too deep.

I will copy the abstract below and I can actually make the biggest point from the abstract that I learned in the whole document.  I am hesitant to quote from the actual article since they are charging so much for it – I don’t want anyone getting mad at me for copyright infringement. Basically the article discusses how much improved this new climate modeling technique is then the older techniques.  They go on to rave about how it is only 19% off compared to observed measurements.  I don’t know about you but that sure gives me a lot of confidence that these types of models can accurately predict 50 years out – NOT!!

We present an evaluation of transport of sulfur hexafluoride (SF6) in the two-way nested chemistry-transport model “Tracer Model 5” (TM5). Modeled SF6 values for January 2000 to November 2003 are compared with NOAA CMDL observations. This includes new high-frequency SF6 observations, frequent vertical profiles, and weekly flask data from more than 60 sites around the globe. This constitutes the most extensive set of SF6 observations used in transport model evaluation to date. We find that TM5 captures temporal variability on all timescales well, including the relatively large SF6 signals on synoptic scales (2–5 days). The model overestimates the meridional gradient of SF6 by 19%, similar to previously used transport models. Vertical profiles are reproduced to within the standard error of the observations, and do not reveal large biases. An important area for future improvements is the mixing of the planetary boundary layer which is currently too slow, leading to modeled SF6 mixing ratios that are too large over the continents. Increasing the horizontal resolution over North America from 6×4°, to 3×2°, to even 1×1° (lon×lat) does not affect the simulated global scale SF6 distribution and potentially minimizes representation errors for continental sites. These results are highly relevant for future CO2 flux estimates with TM5, which will be briefly discussed.

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