Local effective slope at a paleo-reconstruction site — local_effective

Returns a per-draw vector of the d2H_wax-d2H_precip slope at a single site, combining the global posterior beta_oipc with the spatial slope GP prediction at that site. The returned vector is the raw posterior at the site; every draw the calibration produced is preserved without modification.

Usage

local_effective_slope(
  longitude,
  latitude,
  model_name,
  override = NULL,
  n_draws = NULL,
  verbose = FALSE
)

Arguments

longitude: Numeric, single longitude in decimal degrees.
latitude: Numeric, single latitude in decimal degrees.
model_name: Character, v10 model name (see available_models()). Must be a spatial model (*_sp) for the site-specific slope to differ from the global mean; non-spatial models return the global posterior unchanged.
override: Optional numeric. NULL (default) uses the model slope. A single value broadcasts across all draws. A vector of length n_draws is used per draw.
n_draws: Integer, optional number of posterior draws to use (NULL uses all). Forwarded to load_posteriors().
verbose: Logical, whether to print progress messages.

Value

Numeric vector of length n_draws, the per-draw effective slope at the site (after override, if any).

Details

Two modes:

Default: returns the model's per-draw slope at the site.
Override (single value or per-draw vector) replaces the model slope with a defended local value (e.g., from independent evidence about source-water seasonality, leaf-water enrichment, or vegetation).

Pass the returned vector to invert_d2H(..., slope = ...) to propagate it through the inversion.

Mechanistic reference values (e.g. the simple two-pool stationarity bound alpha = 1 + epsilon_app/1000 ~ 0.88 under epsilon_app ~= -120 permil; Sessions 2005) are documented for interpretation but are never applied to the returned draws. The frequency of draws above any chosen reference is computable directly from the returned vector (mean(slope > 0.88)) and carries scientific information about how often the calibration implicates non-stationarity at the site.

Examples

# \donttest{
# St. Louis with the baseline_sp model
s <- local_effective_slope(
  longitude = -90, latitude = 38,
  model_name = "baseline_sp",
  n_draws = 200
)
#> Warning: leafwax preview posteriors in use: 100 draws of 'baseline_sp'. Tail probabilities and 95% credible intervals are unstable at this sample size; not suitable for inference. Run download_model_data("baseline_sp") for the full posterior.
summary(s)
#>    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
#>  0.3927  0.5540  0.6020  0.6110  0.6820  0.8342 

# How often does the calibration imply a slope above the simple-model
# stationarity bound at this site?
mean(s > 0.88)
#> [1] 0

# Override with a defended local slope
s_fixed <- local_effective_slope(
  longitude = -90, latitude = 38,
  model_name = "baseline_sp",
  override = 0.55
)
#> Warning: leafwax preview posteriors in use: 100 draws of 'baseline_sp'. Tail probabilities and 95% credible intervals are unstable at this sample size; not suitable for inference. Run download_model_data("baseline_sp") for the full posterior.

# Pass through to the inversion. The slope vector and the
# inversion's posterior must use the same n_draws: pair
# local_effective_slope(..., n_draws = N) with
# invert_d2H(..., n_posterior_draws = N, slope = s), or pass a
# single point estimate (e.g., median(s)).
invert_d2H(d2H_wax = -180, d2H_wax_sd = 3,
           longitude = -90, latitude = 38,
           model_name = "baseline_sp",
           n_posterior_draws = 200,
           slope = s)
#> Loading model: baseline_sp 
#> Loading model: baseline_sp
#>   Loaded 100 draws, 271 parameters
#>   Loaded 125 spatial knots
#>   Loaded standardization parameters (20 fields)
#> Performing inversion for 1 locations
#>   Computing dual-GP spatial effects (Matern 3/2)...
#>   Using slope override (range: 0.393 to 0.834) instead of the model's site-specific slope.
#> Computing predictions...
#> 
#> Inversion complete:
#>   Mean prediction range: [-56.7, -56.7] per mil
#>   Mean uncertainty (SD): 26 per mil
#>   Mean 90% width: 88.3 per mil
#> Warning: leafwax preview posteriors in use (invert_d2H): 100 draws of 'baseline_sp'. Tail probabilities and 95% credible intervals are unstable at this sample size; not suitable for inference. Run download_model_data("baseline_sp") for the full posterior.
#>   longitude latitude elevation d2h_wax d2h_wax_err d2h_precip_mean
#> 1       -90       38         0    -180           3       -56.68282
#>   d2h_precip_median d2h_precip_sd d2h_precip_lower d2h_precip_upper
#> 1         -57.60734      26.01051        -105.0963        -16.82198
#>   prediction_interval_width
#> 1                  88.27435
# }