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Conversion scheme for land covers (CSLC)

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Ting Sun edited this page Oct 20, 2018 · 4 revisions

Conversion scheme for land cover (CSLC) WRF-SUEWS

background

When coupling SUEWS with WRF, one of noticeable differences/challenges resides in the lands/land cover (LULC) classification: depend ending on the LULC dataset, WRF can use different numbers of LULCs (e.g., USGS with 24 LULCs, MODIS with 20, etc.), whereas SUEWS has seven types of LCs.. The conversion scheme for land covers (CSLC) proposed here (also implemented in the current WRF-SUEWS coupled system) is to reconcile the differences in the LULC scheme and related properties between the WRF framework and SUEWS.

implementation

Given the contrast in architecture design between WRF and SUEWS (WRF is class based while SUEWS is grid/site based), to make SUEWS compatible with the framework it is seated in and to allow measurable inter-comparison with other LSMs, we adopt the class-based scheme this work by reclassifying the WRF LULC classes into seven types as used by SUEWS. As such, most of the existing land surface properties can be seamlessly inherited by SUEWS (however, some SUEWS specific ones still need to passed in via WRF_input files).

usage

The CSLC is exposed to users via the namelist.suews file as a landuse section shown below:

&landuse
suews_cat_ind(1,  1:10)     = 13,
suews_cat_frac(1, 1:10)     = 0.5,
suews_cat_ind(2,  1:10)     = 13,
suews_cat_frac(2, 1:10)     = 0.5,
suews_cat_ind(3,  1:10)     = 1,  2,  5,
suews_cat_frac(3, 1:10)     = 1,  1,  1,
suews_cat_ind(4,  1:10)     = 3,  4,
suews_cat_frac(4, 1:10)     = 1,  1,
suews_cat_ind(5,  1:10)     = 6,  7,  8,  9,  10,  12,  14,
suews_cat_frac(5, 1:10)     = 1,  1,  1,  1,  1,   1,   1,
suews_cat_ind(6,  1:10)     = 16, 18, 19, 20,
suews_cat_frac(6, 1:10)     = 1,  1,  1,  1,
suews_cat_ind(7,  1:10)     = 11, 17,
suews_cat_frac(7, 1:10)     = 1,  1,
suews_cat_ind(8,  1:10)     = -999, -999
suews_cat_frac(8, 1:10)     = 1,  1,

The landuse section consists of two types of entries:

  1. suews_cat_ind: referencing indices to the LULC codes used by the main WRF framework (e.g., MODIS).
  2. suews_cat_frac: contributing fractions of corresponding LULCs specified in suews_cat_ind.
  • For instance, in the example above, we use LC 13 of WRF as the basis for LC 1 and 2 of SUEWS by splitting it in halves and distributing it as paved and building surfaces.
  • Another example is suews_cat_ind(5, 1:10), where multiple WRF LCs are aggregated into SUEWS LC 5 and their properties values are averaged to be used by SUEWS.

One caveat/limitation that should be appreciated here is that the number of WRF LC candidates for each SUEWS LC is limited to 10 due to the programming inflexibility (i.e., varying-length arrays are not easy to handle and demand unnecessary work at this stage).

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