#### kunaldayal

##### Member

I have run simulations using the WRF model for two-way nested domains for a tropical country with two major islands for the purpose of mesoscale wind resource mapping.

The 3 domains initially used was D1 = 20 km x 20 km, D2 = 4 km x 4 km and D3 = 1.33 km x 1.33 km. With this simulation configuration, the 10 m wind speed, 2 m temperature and the diurnal cycle of wind speed and temperature on the windward side for domain 3 (1.33 km x 1.33 km) are simulated similar to those observed on the ground from automatic weather stations (AWSs).

But on the leeward side stations, there is a poor simulation of the diurnal cycle of wind speed and temperature in comparison with the observations from AWSs. Also, there is overnight over-estimation of wind speed at almost all locations.

To fix the problem, I ran two test simulations over one island only by increasing the grid resolution of domain 3 to 1 km x 1 km and 0.8 km x 0.8 km.

To my surprise, these simulations at 1 km x 1 km and 0.8 km x 0.8 km actually solved the problem on the leeward side. Now, I could see a big improvement in the simulated 10 m wind speed, 2 m temperature and the diurnal cycle of wind speed and temperature on the leeward side of the island.

But, few locations (3 out of 6) on the windward of the island now have a poor simulation of the diurnal cycle of wind speed and temperature. Also, there is overnight over-prediction of wind speed for these windward side stations.

I am not sure whether such contrasting behavior is normal for the WRF model at higher resolutions of 1 km x 1 km and 0.8 km by 0.8 km. But the results are consistent for 1 km x 1 km and 0.8 km x 0.8 km grid resolutions.

I seek assistance and advice as to whether such behavior is normal for the WRF model?

And whether the 1 km x 1 km and 0.8 km x 0.8 km result consistency can be used to say that both are optimal grid resolutions?

Appreciate your assistance and advice.

Regards

Kunal