Update to RRTMGP v1.7

[mathomp4]

This release of GEOSradiation_GridComp moves it to use RRTMGP v1.7. Note this release will not compile unless also used with RRTMGP v1.7 as there are file changes in CMake. Moreover, to run RRTMGP you also need a corresponding change in AGCM.rc, see GEOS-ESM/GEOSgcm_App#585

This release is zero-diff to GEOSradiation_GridComp v1.7 when not running RRTMGP, but is non-zero-diff for RRTMGP.

Note also that RRTMGP v1.7 can be run in Single Precision mode with the CMake option:

-DRRTMGP_SINGLE_PRECISION=ON

Tests show that single-precision RRTMGP is about 10-20% faster than DP. But, for now we are keeping the default build to be double precision by default until further testing. Per @dr0cloud:

I have noticed around a -0.15W/m2 difference in global OSR in SP mode, but individual clouds can be -2 W/m2 or more.

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This discussion was created from the release Update to RRTMGP v1.7.