Merge pull request #147 from NOC-MSM/127_interpolation_error_in_TandS

issue 127, a fix for the temp and salinity interpolation issues.

I want this in to simplify my AMM7v4.0.4 documentation that is in progress

src/pybdy/nemo_bdy_extr_tm3.py

@@ -873,13 +873,19 @@ def extract_month(self, year, month):
                 else:
                     id_121 = self.id_121_3d
                     tmp_filt = self.tmp_filt_3d
-
-                tmp_valid = np.invert(np.isnan(dst_bdy.flatten("F")[id_121]))
-
+
+                #tmp_valid = np.invert(np.isnan(dst_bdy.flatten("F")[id_121]))
+                # interpolation points that are not wet (=0) need to be reflected
+                # in the denominator
+                tmp_valid = np.invert(dst_bdy.flatten('F')[id_121] == 0 )
+                # raises invalid divide error when all points are dry,
+                # this is ok because the numerator=0 as well so it will
+                # set to NaN which is set to zero later in code
+                np.seterr(invalid='ignore')
                 dst_bdy = np.nansum(
                     dst_bdy.flatten("F")[id_121] * tmp_filt, 2
                 ) / np.sum(tmp_filt * tmp_valid, 2)
-
+                np.seterr(invalid='warn')
                 # Finished first run operations
                 # self.first = False
 
@@ -890,6 +896,7 @@ def extract_month(self, year, month):
                     np.nanmax(dst_bdy),
                 )
                 dst_bdy[nan_ind] = 0
+
                 self.logger.info(
                     " post dst_bdy %s %s", np.nanmin(dst_bdy), np.nanmax(dst_bdy)
                 )