[develop] Fixing dead link (#1310)

Quick link fix to resolve build errors

Author: jdkublnick

doc/UsersGuide/Reference/Glossary.rst

@@ -159,7 +159,7 @@ Glossary
       The Model of Emissions of Gases and Aerosols from Nature (`MEGAN <https://bai.ess.uci.edu/megan>`__) is a modeling system for estimating the emission of gases and aerosols from terrestrial ecosystems into the atmosphere. It has been integrated into a number of chemistry and transport models, including :ref:`NEXUS <nexus>`. 
 
    MERRA2
-      The `Modern-Era Retrospective analysis for Research and Applications, Version 2 <https://gmao.gsfc.nasa.gov/reanalysis/MERRA-2/>`__ provides satellite observation data back to 1980. According to NASA, "It was introduced to replace the original MERRA dataset because of the advances made in the assimilation system that enable assimilation of modern hyperspectral radiance and microwave observations, along with GPS-Radio Occultation datasets. It also uses NASA's ozone profile observations that began in late 2004. Additional advances in both the GEOS model and the GSI assimilation system are included in MERRA-2. Spatial resolution remains about the same (about 50 km in the latitudinal direction) as in MERRA."
+      The `Modern-Era Retrospective analysis for Research and Applications, Version 2 <https://gmao.gsfc.nasa.gov/gmao-products/merra-2>`__ provides satellite observation data back to 1980. According to NASA, "It was introduced to replace the original MERRA dataset because of the advances made in the assimilation system that enable assimilation of modern hyperspectral radiance and microwave observations, along with GPS-Radio Occultation datasets. It also uses NASA's ozone profile observations that began in late 2004. Additional advances in both the GEOS model and the GSI assimilation system are included in MERRA-2. Spatial resolution remains about the same (about 50 km in the latitudinal direction) as in MERRA."
 
    MET
    METplus