# Multiple ensemble diagnostic regression (MDER) for constraining future austral jet position#

## Overview#

Wenzel et al. (2016) use multiple ensemble diagnostic regression (MDER) to constrain the CMIP5 future projection of the summer austral jet position with several historical process-oriented diagnostics and respective observations.

The following plots are reproduced:

Absolute correlation between the target variable and the diagnostics.

Scatterplot between the target variable and the MDER-calculated linear combination of diagnostics.

Boxplot of RMSE for the unweighted multi-model mean and the (MDER) weighted multi-model mean of the target variable in a pseudo-reality setup.

Time series of the target variable for all models, observations and MDER predictions.

Errorbar plots for all diagnostics.

Scatterplots between the target variable and all diagnostics.

## Available recipes and diagnostics#

Recipes are stored in recipes/

recipe_wenzel16jclim.yml

Diagnostics are stored in diag_scripts/

austral_jet/asr.ncl

austral_jet/main.ncl

mder/absolute_correlation.ncl

mder/regression_stepwise.ncl

mder/select_for_mder.ncl

## User settings in recipe#

Preprocessor

`extract_region`

: Region extraction.`extract_levels`

: Pressure level extraction.`area_statistics`

: Spatial average calculations.

Script austral_jet/asr.ncl

`season`

,*str*: Season.`average_ens`

,*bool*, optional (default:`False`

): Average over all given ensemble members of a climate model.`wdiag`

,*array of str*, optional: Names of the diagnostic for MDER output. Necessary when MDER output is desired.`wdiag_title`

,*array of str*, optional: Names of the diagnostic in plots.

Script austral_jet/main.ncl

`styleset`

,*str*: Style set used for plotting the multi-model plots.`season`

,*str*: Season.`average_ens`

,*bool*, optional (default:`False`

): Average over all given ensemble members of a climate model.`rsondes`

,*array of str*, optional: Additional observations used in the plot but not for MDER output.`rsondes_file`

,*array of str*, optional: Paths to the additional observations Necessary when`rsondes`

is given.`rsondes_yr_min`

,*int*, optional: Minimum year for additional observations. Necessary when`rsondes`

is given.`rsondes_yr_max`

,*int*, optional: Maximum year for additional observations. Necessary when`rsondes`

is given.`wdiag`

,*array of str*, optional: Names of the diagnostic for MDER output. Necessary when MDER output is desired.`wdiag_title`

,*array of str*, optional: Names of the diagnostic in plots.`derive_var`

,*str*, optional: Derive variables using NCL functions. Must be one of`"tpp"`

,`"mmstf"`

.`derive_latrange`

,*array of float*, optional: Latitude range for variable derivation. Necessary if`derive_var`

is given.`derive_lev`

,*float*, optional: Pressure level (given in*Pa*) for variable derivation. Necessary if`derive_var`

is given.

Script mder/absolute_correlation.ncl

`p_time`

,*array of int*: Start years for future projections.`p_step`

,*int*: Time range for future projections (in years).`scal_time`

,*array of int*: Time range for base period (in years) for anomaly calculations used when`calc_type = "trend"`

.`time_oper`

,*str*: Operation used in NCL`time_operation`

function.`time_opt`

,*str*: Option used in NCL`time_operation`

function.`calc_type`

,*str*: Calculation type for the target variable. Must be one of`"trend"`

,`"pos"`

,`"int"`

.`domain`

,*str*: Domain tag for provenance tracking.`average_ens`

,*bool*, optional (default:`False`

): Average over all given ensemble members of a climate model.`region`

,*str*, optional: Region used for area aggregation. Necessary if input of target variable is multidimensional.`area_oper`

,*str*, optional: Operation used in NCL`area_operation`

function. Necessary if multidimensional is given.`plot_units`

,*str*, optional (attribute for`variable_info`

): Units for the target variable used in the plots.

Script mder/regression_stepwise.ncl

`p_time`

,*array of int*: Start years for future projections.`p_step`

,*int*: Time range for future projections (in years).`scal_time`

,*array of int*: Time range for base period (in years) for anomaly calculations used when`calc_type = "trend"`

.`time_oper`

,*str*: Operation used in NCL`time_operation`

function.`time_opt`

,*str*: Option used in NCL`time_operation`

function.`calc_type`

,*str*: Calculation type for the target variable. Must be one of`"trend"`

,`"pos"`

,`"int"`

.`domain`

,*str*: Domain tag for provenance tracking.`average_ens`

,*bool*, optional (default:`False`

): Average over all given ensemble members of a climate model.`smooth`

,*bool*, optional (default:`False`

): Smooth time period with 1-2-1 filter.`iter`

,*int*, optional: Number of iterations for smoothing. Necessary when`smooth`

is given.`cross_validation_mode`

,*bool*, optional (default:`False`

): Perform cross-validation.`region`

,*str*, optional: Region used for area aggregation. Necessary if input of target variable is multidimensional.`area_oper`

,*str*, optional: Operation used in NCL`area_operation`

function. Necessary if multidimensional is given.`plot_units`

,*str*, optional (attribute for`variable_info`

): Units for the target variable used in the plots.

Script mder/select_for_mder.ncl

`wdiag`

,*array of str*: Names of the diagnostic for MDER output. Necessary when MDER output is desired.`domain`

,*str*: Domain tag for provenance tracking.`ref_dataset`

,*str*: Style set used for plotting the multi-model plots.`average_ens`

,*bool*, optional (default:`False`

): Average over all given ensemble members of a climate model.`derive_var`

,*str*, optional: Derive variables using NCL functions. Must be one of`"tpp"`

,`"mmstf"`

.

## Variables#

*ta*(atmos, monthly, longitude, latitude, pressure level, time)*uajet*(atmos, monthly, time)*va*(atmos, monthly, longitude, latitude, pressure level, time)*ps*(atmos, monthly, longitude, latitude, time)*asr*(atmos, monthly, longitude, latitude, time)

## Observations and reformat scripts#

ERA-Intermin (

*ta*,*uajet*,*va*,*ps*)CERES-EBAF (

*asr*)

## References#

Wenzel, S., V. Eyring, E.P. Gerber, and A.Y. Karpechko: Constraining Future Summer Austral Jet Stream Positions in the CMIP5 Ensemble by Process-Oriented Multiple Diagnostic Regression. J. Climate, 29, 673–687, doi:10.1175/JCLI-D-15-0412.1, 2016.