15 Context 1: Number of birds affected

We can use the RCS estimates calculated previously to generate a rough estimate of the number of birds affected by the fireworks disturbance.

15.1 Processing environment

library(bioRad)
library(ggplot2)
library(dplyr)
library(tidyr)
library(tibble)
library(stringr)

First we load the PPIs at the timestamp of our selected scan.

selected_scan <- load("data/processed/pvol_selection.RData")
scan_dt <- str_extract(basename(pvol_dhl_path), "[0-9]{12}")
scan_dhl <- file.path("data/processed/final-ppis", paste0("RAD_NL61_VOL_NA_", scan_dt, "_ODIM.RDS"))
scan_hrw <- file.path("data/processed/final-ppis", paste0("RAD_NL62_VOL_NA_", scan_dt, "_ODIM.RDS"))
ppis_original <- lapply(list(scan_dhl, scan_hrw), function(x) readRDS(x))

We create a composite PPI and filter out all pixels outside of 66km from the radar.

source("R/comp_ppi.R")
ppis <- ppis_original
maxrange <- 66000
# Set all columns to NA if further than maxrange from radar
ppis[[1]]$data$VIR[ppis[[1]]$data$dist_radar > maxrange] <- NA
ppis[[1]]$data$land[ppis[[1]]$data$dist_radar > maxrange] <- NA
ppis[[2]]$data$VIR[ppis[[2]]$data$dist_radar > maxrange] <- NA
ppis[[2]]$data$land[ppis[[2]]$data$dist_radar > maxrange] <- NA

cppi <- comp_ppi(ppis, param = c("VIR", "land"), method = c("max", "min"), res = c(500, 500), )

## Warning in showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj
## = prefer_proj): Discarded datum Unknown based on WGS84 ellipsoid in Proj4
## definition

## Warning in showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj
## = prefer_proj): Discarded datum Unknown based on WGS84 ellipsoid in Proj4
## definition

## Warning in showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj
## = prefer_proj): Discarded datum Unknown based on WGS84 ellipsoid in Proj4
## definition

## Warning in showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj
## = prefer_proj): Discarded datum Unknown based on WGS84 ellipsoid in Proj4
## definition

## Warning in showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj
## = prefer_proj): Discarded datum Unknown based on WGS84 ellipsoid in Proj4
## definition

cppi$data$VIR[cppi$data$land == 0] <- NA
plot(cppi)

We can now calculate the total VIR within the radar domain and the number of birds that corresponds with given a few RCS values:

ptt_biomass <- readRDS("data/processed/sovon/ptt_biomass.RDS")
total_vir <- sum(cppi$data$VIR, na.rm = TRUE) * 1/4  # Convert to sum of VIR/0.5km2
paste0("Total VIR: ", format(total_vir, scientific = TRUE))
paste0("Response assuming mean RCS of ", round(mean(ptt_biomass$weighted_mean_crs)), " cm^2: ", 
       round(total_vir / mean(ptt_biomass$weighted_mean_crs)), " birds.")
paste0("Response assuming median RCS of ", round(median(ptt_biomass$weighted_mean_crs)), " cm^2: ", 
       round(total_vir / median(ptt_biomass$weighted_mean_crs)), " birds.")
paste0("Response assuming mean RCS of 11 cm^2: ", round(total_vir / 11), " birds.")

## [1] "Total VIR: 3.314054e+07"
## [1] "Response assuming mean RCS of 86 cm^2: 383404 birds."
## [1] "Response assuming median RCS of 82 cm^2: 406339 birds."
## [1] "Response assuming mean RCS of 11 cm^2: 3012776 birds."