问题描述
我正在尝试从 https://nomads.ncep.noaa.gov/pub/data/nccf/com/hrrr/prod/hrrr.20210511/conus/ 找到的 grib 文件中提取点数据。
这些文件由 170 或 173 层（变量）组成。我想使用 terra:extract 提取点处单元格的值。但是，提取失败（层之间有些混乱）。这是我想为每个变量提取数据的 lon/lat：
latlon_df <- structure(list(Lon = c(-103.289,-96.6735,-96.9041,-96.76864,-102.4694,-96.6814,-97.7504,-99.6754,-96.4802,-103.0007,-96.8897,-101.8539,-103.9717,-101.253,-99.1134,-96.5849,-98.0301,-99.9537,-99.4601,-99.7122,-103.8278,-98.931,-102.1081,-101.7162,-100.115,-101.3448,-100.7805,-103.5606,-96.5302,-99.4156,-103.281,-100.0063,-97.9928,-100.7208,-98.5289,-96.762,-96.9218,-97.1024,-103.3793,-101.0841,-102.6745,-96.9188,-97.5154,-100.7435,-98.6938),Lat = c(45.5194,44.3099,43.0526,44.3252,45.5183,43.7316,45.6796,45.4406,44.7154,44.0006,43.7687,43.9599,43.4737,44.9875,45.0292,44.0867,45.5735,44.9895,44.5256,43.5938,43.7343,45.7163,45.9189,43.1672,45.6716,45.9154,45.7963,44.6783,44.5073,43.7982,43.3784,44.2912,43.3841,43.2002,44.8579,43.5048,43.5033,45.1055,44.4245,45.4167,44.5643,44.304,45.2932,43.5601,43.7321)),class = "data.frame",row.names = c(NA,-45L))
library(terra)
latlons <- terra::vect(latlon_df,geom=c('Lon','Lat'),crs="+proj=longlat")
latlons <- project(latlons,"+proj=lcc +lat_0=38.5 +lon_0=262.5 +lat_1=38.5 +lat_2=38.5 +x_0=0 +y_0=0
+R=6371229 +units=m +no_defs")
grib_data <- terra::rast(path to grib downloaded grib file)
extracted_data <- terra::extract(grib_data,latlons)
提取的数据是一团糟，毫无意义。如果我一次做一层效果很好（但需要更长的时间）。
terra::extract(grib_data[[layer]],latlons)[,2]
解决方法
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