The option to combine datasets "temporally" is also useful if there are periods of missing data from a particular dataset. Combining the datasets temporally allows the user to substitute data from an alternate dataset to visualize the entire time period of interest.

Task 4 will demonstrate the "Combine TINs Temporally" function using precipitation grids from the Lower Mississippi River Forecast Center (LMRFC) and South East River Forecast Center (SERFC) for the 29-31 August 2021 event.



Create a New Map Window.

Right‐Click on the "Pearl-Part A" Session.

From the "Sessions and Maps" option, select Add Map Window.

Enter the name "Temporal Combine-Multiple" for the new Map Window in the dialog that pops up and press OK. 

Combine TINs Temporally.

Within the "Temporal Combine-Multiple" Map Window, right-click on the TIN node and click on "Select DSS paths..."

Ensure the selected Combine TINs method is "Temporally."

Make the following DSS file selection:

...\HEC-MetVue_DssDataReader\HEC-MetVue_DssDataReader_Start\Data\DSS\precip.2021.08.dss

Filter the B-Part to "Pearl River" and the F-Part to "SERFC-QPE."

Select the SERFC-QPE precipitation grids for 29 August 2021 00:00 to 29 August 2021 24:00 by highlighting the pathname within the "Available TINs" window and clicking "Add Sel."

Next, change the F-Part filter to "LMRFC-QPE."

Select the LMRFC-QPE precipitation grids for 30 August 2021 00:00 to 31 August 2021 24:00 by highlighting the pathname within the "Available TINs" window and clicking "Add Sel."

Select "OK" to add the selected data to the map window.

The SERFC precipitation data for 29 August 2021 and the LMRFC precipitation data for 30-31 August 2021 has been temporally combined and added to the map window  with basin-average totals from a temporal combination of the grids from two different data sources displayed.

Zoom in closer to the Pearl River watershed if necessary.

While the full period of 29-31 August 2021 is actually available from both the SERFC and LMRFC data sources, the temporal combine method can be very useful for supplementing a primary dataset if there are periods of missing data.

It's important to note that using the SERFC data to "append" missing periods of precipitation in this area is not the best option since the SERFC extents do not cover the entire watershed:

 

 Question: What do you notice about the temporally combined SERFC & LMRFC dataset? 

  • The basin-average values of most subbasins are slightly different for this temporal combination of the SERFC & LMRFC datasets than they were for the temporal combination of just the "SERFC Precip" or just the "LMRFC Precip" for the same event. For example, the basin-average precipitation in the Lower Pearl subbasin was:
    • 5.47" with just the "SERFC Precip"
    • 6.20" with just the "LMRFC Precip"
    • 5.87" with the temporally combined SERFC & LMRFC precipitation. 

This is due to the combination of data sources being utilized during this event to demonstrate temporally combining multiple datasets.

  • Looking closely, you can see the outline of the SERFC data extents within the temporally combined data, particularly on the south and east boundaries. This is due to the varying extents of each dataset.


Check for Data Warnings.

Within the "Temporal Combine" node, expand the TIN node to view the list of data that's been added to the Map Window.

Note that the SERFC-QPE grids are loaded for 29 August 2021 and the LMRFC-QPE grids for 30-31 August 2021.

Scroll through the full list of TINs to verify that each record has a green and blue symbol () to its left, indicating that there are no warnings associated with the data within the Map Window. 

Right-click on the TIN node and click on "Select DSS paths..."

Update the F-Part filter to "LMRFC-QPE" and add the LMRFC precipitation grids for 29 August 2021 00:00 to 31 August 2021 24:00 to the list of selected TINs. 

Select "OK" to add the selected data to the map window.

Look again at the Map Window data that's been added within the TIN node.

There's a new red and green symbol () to the left of select data to notify the user that HEC-MetVue has warnings about the data within the Map Window.

Hover the cursor over one of the red and green symbols () to read the warning. 

The warning states that the "the timespan of the previous path overlaps this record." 

This is because we now have data from both the SERFC and LMRFC loaded into the Map Window for 29 August 2021. 

Question: What is the basin-average precipitation for the Lower Pearl subbasin?

  • The basin-average precipitation in the Lower Pearl subbasin was 7.18 inches. This is higher than the previous examples since the 29 August 2021 00:00-24:00 time period is being double-counted as its represented by both the SERFC and LMRFC data.
    • Previous Lower Pearl subbasin averages for reference were: 
      • 5.47" with just the "SERFC Precip"
      • 6.20" with just the "LMRFC Precip"
      • 5.87" with the temporally combined SERFC (29 August 2021) & LMRFC (30-31 August 2021) precipitation. 

Prior Task(s):

Task 1 - Open the HEC-MetVue Program

Task 2 - Combine TINs Temporally - Single Dataset

Task 3 - Compare Different Datasets

Current Task:

Task 4 - Combine TINs Temporally - Multiple Datasets

Next Task(s):

Task 5 - Combine TINs Spatially

Task 6 - Combine TINs Temporally & Spatially ("Both")