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Question about length scale and WRFDA increments in synop (AWS) process

AheanJang

New member
Hello everyone,

While studying WRF 3D-Var, I encountered something unusual and would like to ask a question about it.

Currently, I am conducting experiments in the WRFDA process by adjusting the length scale to find an appropriate value. I observed that when length scale increase, increments peak value decrease and gradually shifts toward the center in domain 3.

To investigate this further, I performed a Single Observation Test at a point in Daegu, South Korea. I found that this phenomenon becomes more pronounced at locations closer to the boundary layer.

I suspect this issue arises when the length scale becomes larger than the defined domain, but I’m having difficulty understanding the exact cause of this behavior. I would appreciate any help or insights.

I upload a AWS Pressure O-B and increments to show my strange problem. The white area means domain 3.

For the data assimilation process, I am using a 136 x 191 domain with a 500 m resolution.

Thank you
 

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