Extremely overestimating tropical cyclogenesis

Any problems/questions that might not fall into the other topics in this category.

Extremely overestimating tropical cyclogenesis

Postby kala » Sat Mar 18, 2017 12:38 am

I have been trying to run a year-long global simulation to observe the patterns of tropical cyclone formation, but I've noticed that WRF (or at least my current settings) seem to overestimate by threefold or more, the number of tropical cyclones which should be forming. I started a simulation based on some GFS output on March 12, and ran the model until April 13 and about 15 tropical cyclones formed in the southern hemisphere during a time when there should be less than 5 on average.

I was wondering if anyone here has ever encountered anything similar or potentially has some solutions or ideas to fix this. Ideally I would like to get a near-realistic number of tropical cyclones in my simulations.

I'm running the global model at ~87 km resolution, which seems to handle tropical cyclones well (better than 133 km, which I tried originally), but it forms them way too often. I'm wondering if this is because the resolution is too coarse and the structure of the cyclones are "ideal" so they are prone to form? I was reading a paper or two about TC climatology using WRF and I found one that mentioned the overformation of cyclones and high biases in tropical rainfall which referenced another paper (Bullock et al 2015) which describes a modified cumulus scheme which decreases the rainfall anomaly, but it doesn't really mention cyclogenesis. I also read somewhere that setting cu_rad_feedback = true fixes the rainfall anomalies at coarser resolutions (as in my case), and I just ran a simulation with that on, but the output is almost identical.

Does anyone have any ideas for what I could try to fix this? I can hardly find any information about it.
kala
 
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