Changes between Version 2 and Version 3 of OMI_use_global_obs


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Timestamp:
Nov 25, 2020, 4:33:46 PM (3 months ago)
Author:
lnerger
Comment:

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  • OMI_use_global_obs

    v2 v3  
    11= Using thisobs%use_global_obs=0 =
    22
    3 In the domain-localized filters (LESTK, LETKF, LSEIK, LNETF) observations are assimilated that are located within the localization around some grid point. When a model uses parallelization with domain-decomposition some of these observations might belong to a different process-domain. In the default mode (`thisobs%use_global_obs`=1) PDAF-OMI gathers all globally available observations so that each process has access to all observations. It can be more efficient to restrict the observations on a process-domain to those observations that are located inside the domain or within the localization radius arond it. Then, in the local analyses a smaller number of observation have to be checked for their distance. Setting `thisobs%use_global_obs=0` activates this feature. However, it needs additional preparations to make PDAF-OMI aware of the limiting coordinates of a process sub-domain.
     3[[PageOutline(2-3,Contents of this page)]]
     4
     5== Overview ==
     6
     7In the domain-localized filters (LESTK, LETKF, LSEIK, LNETF) observations are assimilated that are located within the localization around some grid point. When a model uses parallelization with domain-decomposition some of these observations might belong to a different process-domain. In the default mode (`thisobs%use_global_obs`=1) PDAF-OMI gathers all globally available observations so that each process has access to all observations. It can be more efficient to limit the observations on a process-domain to those observations that are located inside the domain or within the localization radius around it. Then, in the local analyses a smaller number of observation have to be checked for their distance. Setting `thisobs%use_global_obs=0` activates this feature. However, it needs additional preparations to make PDAF-OMI aware of the limiting coordinates of a process sub-domain.
    48
    59In order to make use of the restricted observations, one has to provide PDAF-OMI with the limiting coordinates of a process-subdomain. There are two routines that can to this task:
    610- `PDAFomi_set_domain_limits`
    711- `PDAFomi_get_domain_limits_unstrc`
    8 One of these routines should be called in `init_pdaf` to set the domain information.
     12One of these routines has to be called in `init_pdaf` to set the domain information.
     13
     14After this call, OMI is set up to use domain-limited observations with `thisobs%use_global_obs=0`. The necessary operation will be performed by PDAF-OMI inside PDAFomi_gather_obs and inside the observation operators.
    915
    1016
     
    2531           (2,1)
    2632   (:,1)+---------+
    27         |         |           - (1,1) coordinate of the western (or left) edge of the domain
    28         |         |           - (1,2) coordinate of the eastern (or right) edge of the domain
    29   (1,1) |         | (1,2)     - (2,1) coordinate of the northern (or upper) edge of the domain
    30         |         |           - (2,2) coordinate of the southern (or lower) edge of the domain
     33        |         |           - (1,1) longitude of the western edge of the domain (or x-coordinate of the left edge)
     34        |         |           - (1,2) longitude of the eastern edge of the domain (or x-coordinate of the right edge)
     35  (1,1) |         | (1,2)     - (2,1) latitude of the northern edge of the domain (or y-coordinate of the upper edge)
     36        |         |           - (2,2) latitude of the southern edge of the domain (or y-coordinate of the lower edge)
    3137        |         |
    3238        +---------+(:,2)
    3339           (2,2)
    3440}}}
    35 thus, (:,1) specifies the north-western corner of the sub-domain and (:,2) the souther-estern corner. The first (x) coordinate grows from left to right, while the second coordinate (y) increases from bottom to the top.
     41Thus, (:,1) specifies the north-western corner of the sub-domain and (:,2) the souther-estern corner. The first (x) coordinate grows from left to right, while the second coordinate (y) increases from bottom to the top.
    3642
    3743If the model grid is not decomposed in cardinal directions, but e.g. rotated, the coordinates should specife the extrema. Thus, lim_coords(1,1) would be the coordinate of the northernmost grid point of a domain.