MODIS LAI time resolution

[Utkarsh Mital]

Hello,

I understand MODIS LAI has a 4-day temporal resolution, and that is reflected when the dynamic time series is extracted via watershed workflow. When computing an average or a typical year using watershed_workflow.timeseries.computeAverageYear, there is an interpolation performed which results in a temporal resolution of 1-day. We see this demonstrated in this example.

I'm curious to know how does ATS treat the LAI forcing when it gets data at a 4-day resolution. For instance, if we have LAI for Jan1 and then Jan 5, what values of LAI does ATS assume for Jan 2, Jan 3, Jan 4? Is there an interpolation that happens under the hood?

Thank you,

Utkarsh

[Coon, Ethan]

There is always an interpolation under the hood, even in the daily data case.  ATS is a variable temporal resolution code — it chooses an adaptive time step size based on solver performance, which is effectively how fast are things changing.  So data must be interpolated to arbitrary step sizes, and we usually enforce a maximum step size of 1 day to match the incoming data (through the “required times” option).

By default, it is always linear interpolation of input data in time.  

Ethan

Sent from Ethan Coon’s phone.

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From: ats-...@googlegroups.com <ats-...@googlegroups.com> on behalf of Utkarsh Mital <umi...@lbl.gov>
Sent: Thursday, June 12, 2025 8:17:31 PM
To: Amanzi-ATS Users <ats-...@googlegroups.com>
Subject: [EXTERNAL] MODIS LAI time resolution

 

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