diff --git a/definitions/mars/grib.olda.tpa.def b/definitions/mars/grib.olda.tpa.def
new file mode 100644
index 000000000..198e4144f
--- /dev/null
+++ b/definitions/mars/grib.olda.tpa.def
@@ -0,0 +1,15 @@
+# aliasing MARS date and Time to the date and time defined in local section,
+# corresponding to the end of the Ocean NRT data assimilation
+alias mars.date = dateOfAnalysis;
+alias mars.time = timeOfAnalysis;
+
+# aliasing the new offset date and time to the date and time
+# coming fron the section 1, i.e. reference date and time
+alias mars.offsetdate = dataDate;
+alias mars.offsettime = dataTime;
+
+unalias mars.step;
+alias mars.step = stepRange;
+if (defined(perturbationNumber)) {
+ alias mars.number = perturbationNumber;
+}