Demo Descriptions

In the tutorial, we’ll be using the DASH toolbox to implement several data assimilation algorithms. To facilitate this, we’ve provided two demo datasets. Each demo is derived from a published assimilation and includes some climate model output, proxy records, and other data needed to implement the assimilation. Before continuing, you should choose and download one (or both) of these datasets. Be sure to extract the .zip file after downloading.

Demo 1

The first demo dataset is designed for a Common Era assimilation. This demo uses a set of temperature-sensitive tree-ring records to reconstruct surface temperature in the Northern Hemisphere over the last millennium. The demo relies on (1) climate model output from the CESM Last Millennium Ensemble, and (2) the NTREND tree-ring network. To generate proxy estimates, we will use univariate linear forward models trained on the temperature at each site. You can download the files for this demo here: NTREND demo. We will refer to this demo as the NTREND Demo in the remainder of the workshop.

The downloaded demo includes the following data files:

ntrend.mat

This MAT-file holds the data records and some metadata the NTREND tree-ring network. It also includes linear slopes for the forward models, and proxy uncertainties for the Kalman filter.

b.e11.BLMTRC5CN.f19_g16.002.cam.h0.TREFHT.085001-184912.nc

The two NetCDF files hold surface temperatures (TREFHT) output from the CESM Last Millennium Ensemble. (Specifically, output from full-forcing run 2). This output is a spatial field with a 1.9 x 2.5 (latitude x longitude) resolution. The output is provided on a monthly time step. This first file holds output from 850-1849 CE.

b.e11.BLMTRC5CN.f19_g16.002.cam.h0.TREFHT.185001-200512.nc

This second model output file holds output from 1850-2005 CE.

The demo also includes two other files: ntrend.grid and temperature-cesm.grid. These are the data catalogue files that we will examine in the next open coding session. ntrend.grid catalogues the tree-ring dataset, and temperature-cesm.grid catalogues the climate model output.

Demo 2

The second demo is designed for a Last Glacial Maximum (LGM) assimilation. This demo uses a set of UK’37 records to reconstruct sea surface temperatures (SSTs) at the LGM. The demo relies on (1) climate model output from 16 iCESM LGM simulations, and (2) 89 UK’37 proxy records. To generate proxy estimates, we will use the BaySPLINE forward model for UK’37. For the sake of simplicity, we will ignore seasonal considerations in this demo. You can download the files for this demo here: LGM demo. We will refer to this demo as the LGM Demo for the remainder of the workshop.

The downloaded demo includes the following data files:

UK37.mat

This MAT-file holds data and metadata for the UK’37 proxy records. It also includes proxy uncertainties for the Kalman filter. The proxy records are time-averaged over the interval 18-21 ka.

SST.mat

This MAT-file holds sea-surface temperature (SST) climate model output from iCESM. The dataset includes output from 16 model runs, each using an LGM boundary condition. The output consists of the monthly climatologies for each model run. The output is provided on a tripolar ocean grid.

The demo also includes two other files: UK37.grid and SST.grid. These are the data catalogues that we’ll examine in the next coding session. UK37.grid catalogues the proxy dataset, and SST.grid catalogues the climate model output.