diff --git a/topic-hierarchy/earth-system-discipline/hydrology/index.csv b/topic-hierarchy/earth-system-discipline/space-weather/hydrology/index.csv
similarity index 100%
rename from topic-hierarchy/earth-system-discipline/hydrology/index.csv
rename to topic-hierarchy/earth-system-discipline/space-weather/hydrology/index.csv
diff --git a/topic-hierarchy/earth-system-discipline/weather/prediction/forecast/medium-range/deterministic/index.csv b/topic-hierarchy/earth-system-discipline/weather/prediction/forecast/medium-range/deterministic/index.csv
index f858b2f..0422310 100644
--- a/topic-hierarchy/earth-system-discipline/weather/prediction/forecast/medium-range/deterministic/index.csv
+++ b/topic-hierarchy/earth-system-discipline/weather/prediction/forecast/medium-range/deterministic/index.csv
@@ -1,3 +1,4 @@
 Name,Description,Source
 global,A prediction system that covers the entire globe,
 limited-area,A prediction system that does not cover the entire globe,
+trajectory,"Line in space representing the successive positions of (i) moving particles in the air, such as radioactive particles from a nuclear accident or (ii) the centre of a weather system, such as a tropical cyclone.",
diff --git a/topic-hierarchy/earth-system-discipline/weather/prediction/forecast/medium-range/probabilistic/index.csv b/topic-hierarchy/earth-system-discipline/weather/prediction/forecast/medium-range/probabilistic/index.csv
index f858b2f..30178f1 100644
--- a/topic-hierarchy/earth-system-discipline/weather/prediction/forecast/medium-range/probabilistic/index.csv
+++ b/topic-hierarchy/earth-system-discipline/weather/prediction/forecast/medium-range/probabilistic/index.csv
@@ -1,3 +1,4 @@
 Name,Description,Source
 global,A prediction system that covers the entire globe,
 limited-area,A prediction system that does not cover the entire globe,
+trajectory,"Line in space representing the successive positions of (i) moving particles in the air, such as radioactive particles from a nuclear accident or (ii) the centre of a weather system, such as a tropical cyclone.",
\ No newline at end of file
diff --git a/topic-hierarchy/earth-system-discipline/weather/prediction/forecast/short-range/deterministic/index.csv b/topic-hierarchy/earth-system-discipline/weather/prediction/forecast/short-range/deterministic/index.csv
index f858b2f..30178f1 100644
--- a/topic-hierarchy/earth-system-discipline/weather/prediction/forecast/short-range/deterministic/index.csv
+++ b/topic-hierarchy/earth-system-discipline/weather/prediction/forecast/short-range/deterministic/index.csv
@@ -1,3 +1,4 @@
 Name,Description,Source
 global,A prediction system that covers the entire globe,
 limited-area,A prediction system that does not cover the entire globe,
+trajectory,"Line in space representing the successive positions of (i) moving particles in the air, such as radioactive particles from a nuclear accident or (ii) the centre of a weather system, such as a tropical cyclone.",
\ No newline at end of file
diff --git a/topic-hierarchy/earth-system-discipline/weather/prediction/forecast/short-range/probabilistic/index.csv b/topic-hierarchy/earth-system-discipline/weather/prediction/forecast/short-range/probabilistic/index.csv
index f858b2f..30178f1 100644
--- a/topic-hierarchy/earth-system-discipline/weather/prediction/forecast/short-range/probabilistic/index.csv
+++ b/topic-hierarchy/earth-system-discipline/weather/prediction/forecast/short-range/probabilistic/index.csv
@@ -1,3 +1,4 @@
 Name,Description,Source
 global,A prediction system that covers the entire globe,
 limited-area,A prediction system that does not cover the entire globe,
+trajectory,"Line in space representing the successive positions of (i) moving particles in the air, such as radioactive particles from a nuclear accident or (ii) the centre of a weather system, such as a tropical cyclone.",
\ No newline at end of file