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| IMS mask based on altitude (>1500m) | IMS mask based on SDFOR (>200) |
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IMS thinning
In the current operational system, a data thinning is applied to IMS by using "bufr_filter" to select 1 from every 36 raw observations. However, it leads to inhomogeneous coverage of IMS, especially in some areas. In order to improve it, new data thinning has been tested by using "bufr_grid_screen_parallel" as same as other satellite observations. The thinning selects nearest observations on a gaussian grid of 31km. As a result, the coverage becomes homogeneous and number of observations is reduced from 251926 to 109223.
| Simple thinning (select 1 from every 36) | Updated thinning (select nearest IMS on a gaussian grid of 31km) |
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