From f04872d77a62fa9f76355b1e2a608b7d328867f6 Mon Sep 17 00:00:00 2001
From: Trygve Aspelien <trygveasp@met.no>
Date: Thu, 9 Jan 2025 15:40:38 +0100
Subject: [PATCH] Set accumulated values to zero for first time step (#47)

* Set accumulated values to zero for first time step

* Bump python version since 3.8 is EOL

* Bump python version since 3.8 is EOL

* Black
---
 .github/workflows/linting.yaml       |  2 +-
 .github/workflows/python-package.yml | 10 +++++-----
 pyproject.toml                       |  2 +-
 pysurfex/variable.py                 | 17 +++++++++++++++--
 4 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/.github/workflows/linting.yaml b/.github/workflows/linting.yaml
index 9bde1c7..72fe443 100644
--- a/.github/workflows/linting.yaml
+++ b/.github/workflows/linting.yaml
@@ -29,7 +29,7 @@ jobs:
         id: setup-python
         uses: actions/setup-python@v4
         with:
-          python-version: '3.8'
+          python-version: '3.9'
 
       #----------------------------------------------
       #  --- configure poetry & install project  ----
diff --git a/.github/workflows/python-package.yml b/.github/workflows/python-package.yml
index c2964e8..e59437f 100644
--- a/.github/workflows/python-package.yml
+++ b/.github/workflows/python-package.yml
@@ -17,7 +17,7 @@ jobs:
       matrix:
         os: [ "ubuntu-latest" ]
         env: [ "pytest" ]
-        python-version: [ "3.8" ]
+        python-version: [ "3.9" ]
 
     name: "${{ matrix.os }}, python=${{ matrix.python-version }}"
     runs-on: ${{ matrix.os }}
@@ -70,7 +70,7 @@ jobs:
           poetry run pytest
 
       - name: Coveralls
-        if: ${{ matrix.python-version == 3.8 }}
+        if: ${{ matrix.python-version == 3.9 }}
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         run: |
@@ -79,13 +79,13 @@ jobs:
           poetry run coveralls
 
       - name: Create documentation
-        if: ${{ matrix.python-version == 3.8 }}
+        if: ${{ matrix.python-version == 3.9 }}
         run: |
           cd docs
           poetry run python auto_sphinx.py
           make html
       - name: Commit documentation changes
-        if: ${{ matrix.python-version == 3.8 }}
+        if: ${{ matrix.python-version == 3.9 }}
         run: |
           git clone https://github.com/metno/pysurfex.git --branch gh-pages --single-branch gh-pages
           cp -r docs/build/html/* gh-pages/
@@ -97,7 +97,7 @@ jobs:
           # The above command will fail if no changes were present, so we ignore
           # the return code.
       - name: Push changes
-        if: ${{ matrix.python-version == 3.8 && github.event_name != 'pull_request' }}
+        if: ${{ matrix.python-version == 3.9 && github.event_name != 'pull_request' }}
         uses: ad-m/github-push-action@master
         with:
           branch: gh-pages
diff --git a/pyproject.toml b/pyproject.toml
index 9f2ffce..27993d2 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -43,7 +43,7 @@
     requires = ["poetry-core > 1.2.0"]
 
 [tool.poetry.dependencies]
-    python = "^3.8"
+    python = "^3.9"
     dateutils = "^0.6.12"
     f90nml = "^1.4.3"
     humanize = ">=3.14.0"
diff --git a/pysurfex/variable.py b/pysurfex/variable.py
index f3cecf8..b92b255 100644
--- a/pysurfex/variable.py
+++ b/pysurfex/variable.py
@@ -394,6 +394,7 @@ def read_variable(self, geo, validtime, cache=None):
         """
         # Set variable info
         previous_field = None
+        first_time = False
         if self.accumulated:
             # Re-read field
             previoustime = validtime - as_timedelta(seconds=self.interval)
@@ -408,14 +409,26 @@ def read_variable(self, geo, validtime, cache=None):
                     cache=cache,
                 )
             else:
+                first_time = True
                 previous_field = np.zeros([geo.npoints])
         elif self.instant > 0:
             previous_field = np.zeros([geo.npoints])
 
-        field = self.read_var_points(self.file_var, geo, validtime=validtime, cache=cache)
+        deaccumulate = False
+        if self.accumulated or self.instant > 0:
+            deaccumulate = True
+
+        # Always set accumulated values to zero the first time
+        if first_time:
+            deaccumulate = False
+            field = np.zeros([geo.npoints])
+        else:
+            field = self.read_var_points(
+                self.file_var, geo, validtime=validtime, cache=cache
+            )
 
         # Deaccumulate if either two files are read or if instant is > 0.
-        if self.accumulated or self.instant > 0:
+        if deaccumulate:
             field = self.deaccumulate(field, previous_field, self.instant)
             if any(field[field < 0.0]):
                 raise RuntimeError(