Generalizing MITgcm read in to enabele read in of SPARC

.flake8

@@ -1,5 +1,5 @@
 [flake8]
-ignore = R0913, R0914, C0415, E0402, F401, E203, F811, W503
+ignore = R0913, R0914, C0415, E0402, F401, E203, F811, W503, C901
 max-line-length = 88
 max-complexity = 18
 select = B,C,E,F,W,T4,B9

gcm_toolkit/core/const.py

@@ -7,7 +7,7 @@
 These variable names are currently in sync with the naming scheme
 from the cubedsphere package.
 The advantage of that is that we do not need to worry about
-variable naming inconsistancies with exorad data.
+variable naming inconsistancies with mitgcm data.
 ==============================================================
 """
 VARNAMES = dict(
@@ -62,8 +62,12 @@
     P_orb="P_orb",
     g="g",
     R_p="R_p",
+    Kappa="Kappa",
     cp="cp",
-    R="R",
+    R="R",  # specific gas constant
+    p_ref="p_ref",
+    p0="p0",
+    dt="dt",
 )
 
 SUPPORTED_GCMS = ["MITgcm"]

gcm_toolkit/core/units.py

@@ -46,13 +46,15 @@ def convert_pressure(dsi, current_unit, goal_unit):
                 .to(u.Unit(goal_unit))
                 .value
             )
-    dsi.attrs.update(
-        {
-            "p_ref": (dsi.p_ref * u.Unit(current_unit))
-            .to(u.Unit(goal_unit))
-            .value
-        }
-    )
+    for attr in [c["p_ref"], c["p0"]]:
+        if attr in dsi.attrs:
+            dsi.attrs.update(
+                {
+                    attr: (dsi.attrs[attr] * u.Unit(current_unit))
+                    .to(u.Unit(goal_unit))
+                    .value
+                }
+            )
 
     # store the units in the dataset attributes
     dsi.attrs["p_unit"] = goal_unit
@@ -90,17 +92,17 @@ def convert_time(dsi, current_unit, goal_unit):
     if (
         current_unit != goal_unit
         and (current_unit == "iter" or goal_unit == "iter")
-        and dsi.attrs.get("dt") is None
+        and dsi.attrs.get(c["dt"]) is None
     ):
         raise ValueError(
             "You can only convert units if the timestep is known. "
         )
 
     # Convert time:
     if current_unit == "iter" and goal_unit == "day":
-        dsi[c["time"]] = dsi.iter * dsi.attrs["dt"] / (3600 * 24)
+        dsi[c["time"]] = dsi.iter * dsi.attrs[c["dt"]] / (3600 * 24)
     if current_unit == "day" and goal_unit == "iter":
-        dsi[c["time"]] = dsi.iter / dsi.attrs["dt"] * (3600 * 24)
+        dsi[c["time"]] = dsi.iter / dsi.attrs[c["dt"]] * (3600 * 24)
 
     # store the units in the dataset attributes
     dsi.attrs["time_unit"] = goal_unit