Compute climate anomalies — cd

Calculates departure from a baseline for each year. Uses cd_variables() to determine the anomaly type: absolute deviation for temperature, VPD, RH, and the annual snow scalars; percent of normal for precipitation, soil moisture, and the monthly snow vars (swe, snowfall, snowmelt); percentage-point difference for variables that are already fractions/percentages (snow_cover, snowfall_fraction).

Usage

cd_anomaly(x, baseline, cap_pct = 200)

Arguments

x: A tibble from cd_extract() with columns variable, period, year, value.
baseline: A tibble from cd_baseline() with columns variable, period, baseline_mean.
cap_pct: Numeric. Cap for percent-of-normal anomalies. Values beyond +/- cap_pct are clamped. Default 200. Only applies to pct_normal variables; absolute and pct_point_diff anomalies are not capped.

Value

A tibble with columns variable, period, year, anomaly, anomaly_type, unit.

Examples

catalog <- cd_catalog(
  system.file("extdata", "example_catalog.json", package = "cd")
)
aoi <- sf::st_read(
  system.file("extdata", "example_aoi.gpkg", package = "cd"),
  quiet = TRUE
)
ts <- cd_extract(catalog, aoi)

# Compute anomalies relative to early-period baseline
# Absolute deviation for temperature; percent of normal for precipitation
bl <- cd_baseline(ts, baseline_years = 1951:1955)
cd_anomaly(ts, bl)
#> # A tibble: 10 × 6
#>    variable period  year anomaly anomaly_type unit 
#>    <chr>    <chr>  <int>   <dbl> <chr>        <chr>
#>  1 tmean    annual  1951 -1.43   absolute     °C   
#>  2 tmean    annual  1952 -0.571  absolute     °C   
#>  3 tmean    annual  1953  0.562  absolute     °C   
#>  4 tmean    annual  1954  1.22   absolute     °C   
#>  5 tmean    annual  1955  0.218  absolute     °C   
#>  6 tmean    annual  1956 -1.43   absolute     °C   
#>  7 tmean    annual  1957  0.0707 absolute     °C   
#>  8 tmean    annual  1958  0.106  absolute     °C   
#>  9 tmean    annual  1959  1.98   absolute     °C   
#> 10 tmean    annual  1960 -0.171  absolute     °C