diff --git a/lib/step.rb b/lib/step.rb
index fd5f41e..96ed145 100644
--- a/lib/step.rb
+++ b/lib/step.rb
@@ -1,3 +1,4 @@
+# coding: iso-8859-1
 require 'fileutils'
 
 module CMORizer
@@ -186,6 +187,13 @@ def file_commands
       end
     end
     
+    class FLIP_SIGN < IndividualBaseStep
+      def file_commands
+        cmds = []
+        cmds << CDO_MULC_cmd.new(-1)
+        cmds
+      end
+    end
     
     class AUTO_CONVERT_UNIT < IndividualBaseStep
       def self.auto_convert_unit_possible?(from_unit, to_unit)
@@ -214,6 +222,29 @@ def self.convert_unit_commands(from_unit, to_unit)
             cmds << CDO_MULC_cmd.new(100)
           when ["K", "degC"]
             cmds << CDO_SUBC_cmd.new(-273.15)
+          when ["mmolC/m2/d", "kg m-2 s-1"]
+            # notes on how this factor was derived (by chrisdane "Christopher Danek")
+            # e.g. recom variable: CO2f => CMIP6_Omon.json: fgco2
+            # 1) mmolC -> molC: /1e3
+            # 2) molC -> gC: *12.0107
+            # 3) gC -> kgC: /1e3
+            # 4) d-1 -> s-1: /86400
+            # -> mult_factor = 1/1e3*12.0107/1e3/86400 # = 1.390127e-10
+            # In the CMIP6_Omon.json:fgco2 case, an additional sign change is necessary:
+            # >0: into ocean -> >0: into atm: *-1
+            # -> mult_factor = mult_factor*-1
+            # COMMENT: For sign change use flip_sign function 
+            cmds << CDO_MULC_cmd.new(1.390127e-10)
+          when ["uatm", "Pa"]
+            # notes on how this factor was derived (by chrisdane "Christopher Danek")
+            # e.g. recom variable: pCO2s => CMIP6_Omon.json: spco2
+            # 1) µatm -> atm: /1e6
+            # 2) atm -> Pa: *1.01325e5 (1 atm = 1.01325e5 Pa)
+            # -> mult_factor = 1/1e6*1.01325e5 # = 0.101325
+            #
+            # these notes are available on the following link
+            # https://notes.desy.de/F8hTyk3PRielZrVdZRtyaQ?view#Seamore-missing-features-FESOM1-and-2
+            cmds << CDO_MULC_cmd.new(0.101325)
           else
             raise "can not automatically convert unit from '#{from_unit}' to '#{to_unit}'"
           end