plot_SST_aroud_Japan.R

pacman::p_load(
  ncdf4,
  sf,
  rnaturalearth,
  tidyverse,
  reshape2,
  scales)

world_map <- ne_countries(scale = "large",
                          returnclass = "sf")
box = c(xmin = 125, ymin = 25, xmax = 150, ymax = 50)
sf_use_s2(FALSE)
Asia <- st_crop(world_map, box) 


FILE <- "C:/Users/ ... /******.nc"

nc4data <- nc_open(FILE)
sst <- as.vector(ncvar_get(nc4data, "sst")) 
melt(matrix(sst, ncol = 1440, byrow =T)) |> 
  filter(value != is.na(value)) |> 
  mutate(lon = Var2 / 4 -  0.125) |> 
  mutate(lat = Var1 / 4 - 90.125) |> 
  dplyr::select(lon, lat, sst = value) |> 
  filter(lon >= 90) |> 
  filter(lon <= 180) |>
  filter(lat >= 0) |> 
  ggplot() +
  geom_point(aes(x = lon, y = lat, color = sst), size = 2) +
  geom_sf(data = Asia, linewidth = 0.1, color = "gray60") +
  scale_color_gradient2(low = muted("blue"), mid = "white",
                        high = "red", midpoint = 15) +
  theme_void() +
  xlim(c(125, 150)) + ylim(c(25, 50))