.. _GEOS-DYAMOND-SUMMER:

GEOS
========================================


Model description
-----------------


The Goddard Earth Observing System (GEOS) model
is a modular Earth system model designed for
simulation and assimilation to address a vast
array of applications for Earth system science.
The GEOS model is built around the FV3
non-hydrostatic dynamical core on the
cubed-sphere maintained in collaboration with
NOAA. GEOS includes the Goddard Chemistry
Aerosol Radiation and Transport (GOCART)
model.GOCART models the emissions, mixing,
chemistry, and deposition of some of the key
aerosol types found in the troposphere, like
sulfates, dust, and black carbon. Surface
emissions and uptake of aerosols and trace gases
is driven by daily volcanic and biomass burning
emissions, biogenic sources and sinks of CO2,
and high-resolution inventories of anthropogenic
sources.

More information can be found on the `GEOS
website <https://gmao.gsfc.nasa.gov/GEOS_systems/>`__.

Contact 
~~~~~~~
`William Putman <william.m.putman@nasa.gov>`__, NASA's Goddard Space Flight Center (NASA/GSFC), USA


Data structure
--------------

Horizontal
~~~~~~~~~~
Grid resolutions that are being used are c768
(12km) c1536 (6km) and c3072 (3km). 

Vertical
~~~~~~~~

The vertical
resolution is chosen set to 72 levels from the
surface to 0.01 mb.


Data
----



Initialisation and Boundary conditions
--------------------------------------

Soil Initialisation
~~~~~~~~~~~~~~~~~~~
The land surface and soil initialisation come
the GEOS ADAS system (see below).



Input Data
~~~~~~~~~~
Initialisation data come from the GEOS
atmospheric data assimilation system (ADAS). The
GEOS ADAS in these experiments uses aHybrid
4D-Ensemble Variational (Hyb-4DEnVar) approach
using acentral ADAS with a 25-km resolution
version of the GEOS AGCM, with the hybrid GSI
analysis produced at 50 km. The 32-member
ensemble operates at roughly 100 km (for both
the AGCM and the analysis).


Treatment of SST and Sea Ice
~~~~~~~~~~~~~~~~~~~~~~~~~~~~


GEOS uses the dailyOperational Sea Surface
Temperature and Sea Ice Analysis (OSTIA) at
1/8th degree resolution.



See also
--------