Added a README.md file

README.md

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+# GFDL_atmos_cubed_sphere
+
+This is for the FV3 dynamical core and the GFDL Microphysics for use by NCEP/EMC within GFS.
+
+# Where to find information
+
+See the [FV3 documentation and references](https://www.gfdl.noaa.gov/fv3/fv3-documentation-and-references/) for more information.
+
+# Proper usage attribution
+
+Cite either Putman and Lin (2007) or Harris and Lin (2013) when describing a model using the FV3 dynamical core.
+Cite Chen et al (2013) and Zhou et al (2019) if using the GFDL Microphysics.
+
+# What files are what
+
+The top level directory structure groups source code and input files as follow:
+
+| File/directory    | Purpose |
+| --------------    | ------- |
+| ```LICENSE.md```  | a copy of the Gnu lesser general public license, version 3. |
+| ```README.md```   | this file with basic pointers to more information |
+| ```model/```      | contains the source code for core of the FV3 dyanmical core |
+| ```model_nh/```   | contains the source code for non-hydrostatic extensions |
+| ```driver/```     | contains drivers used by different models/modeling systems |
+| ```tools/```      | contains source code of tools used within the core |
+| ```GFDL_tools/``` | contains source code of tools specific to GFDL models |
+
+# Disclaimer
+
+The United States Department of Commerce (DOC) GitHub project code is provided
+on an "as is" basis and the user assumes responsibility for its use. DOC has
+relinquished control of the information and no longer has responsibility to
+protect the integrity, confidentiality, or availability of the information. Any
+claims against the Department of Commerce stemming from the use of its GitHub
+project will be governed by all applicable Federal law. Any reference to
+specific commercial products, processes, or services by service mark,
+trademark, manufacturer, or otherwise, does not constitute or imply their
+endorsement, recommendation or favoring by the Department of Commerce. The
+Department of Commerce seal and logo, or the seal and logo of a DOC bureau,
+shall not be used in any manner to imply endorsement of any commercial product
+or activity by DOC or the United States Government.
+
+This project code is made available through GitHub but is managed by NOAA-GFDL
+at https://gitlab.gfdl.noaa.gov.