Question

我正在处理WRF气候数据（北美地区4 km分辨率，可在此处找到：https://rda.ucar.edu/datasets/ds612.0/index.html#!description）。数据格式为netcdf。我想以栅格形式读取数据，并使用R将数据投影到经/纬度坐标。我想这样做，因此我可以提取数据的空间子集并使用栅格代数。但是，我在投影数据时遇到了麻烦。

在线上已经有很多关于WRF投影以及如何使用它们的技巧（见this和this）。

首先，我一直使用常量文件（纬度，经度，地形高度，土壤类型等）。可从原始来源https://rda.ucar.edu/datasets/ds612.0/index.html#cgi-bin/datasets/getWebList?dsnum=612.0&action=customize&disp=&gindex=1此处获得，它称为RALconus_4km_wrf_constants.nc。我已经提供了该文件的副本here。该文件包含尺寸为[west_east，south_north，Time]的字段'HGT'（地形高度）以及尺寸为[west_east，south_north]的字段'XLAT'和'XLONG'。每个网格单元的纬度和经度值都是唯一的。从print（nc）：

Time  Size:1   *** is unlimited ***
        units: hours since 1901-01-01 00:00:00
        calendar: standard
        long_name: Time
        description: Time
    south_north  Size:1015
    west_east  Size:1359

我从WRF文档（here）中知道，投影是lambert保形圆锥，而netcdf文件提供了一些其他详细信息：

    110 global attributes:
    TITLE:  OUTPUT FROM WRF V3.4.1 MODEL
    START_DATE: 2001-02-28_00:00:00
    SIMULATION_START_DATE: 2000-10-01_00:00:00
    WEST-EAST_GRID_DIMENSION: 1360
    SOUTH-NORTH_GRID_DIMENSION: 1016
    BOTTOM-TOP_GRID_DIMENSION: 51
    DX: 4000
    DY: 4000
    GRIDTYPE: C
    DIFF_OPT: 1
    KM_OPT: 4
    DAMP_OPT: 3
    DAMPCOEF: 0.200000002980232
    KHDIF: 0
    KVDIF: 0
    MP_PHYSICS: 28
    RA_LW_PHYSICS: 4
    RA_SW_PHYSICS: 4
    SF_SFCLAY_PHYSICS: 11
    SF_SURFACE_PHYSICS: 4
    BL_PBL_PHYSICS: 1
    CU_PHYSICS: 0
    SURFACE_INPUT_SOURCE: 1
    SST_UPDATE: 1
    GRID_FDDA: 2
    GFDDA_INTERVAL_M: 360
    GFDDA_END_H: 999999
    GRID_SFDDA: 0
    SGFDDA_INTERVAL_M: 0
    SGFDDA_END_H: 0
    HYPSOMETRIC_OPT: 2
    SF_URBAN_PHYSICS: 0
    SHCU_PHYSICS: 0
    MFSHCONV: 0
    FEEDBACK: 0
    SMOOTH_OPTION: 2
    SWRAD_SCAT: 1
    W_DAMPING: 1
    MOIST_ADV_OPT: 1
    SCALAR_ADV_OPT: 1
    TKE_ADV_OPT: 1
    DIFF_6TH_OPT: 0
    DIFF_6TH_FACTOR: 0.119999997317791
    FGDT: 0
    GUV: 4.99999987368938e-05
    GT: 4.99999987368938e-05
    GPH: 4.99999987368938e-05
    IF_RAMPING: 1
    DTRAMP_MIN: 60
    OBS_NUDGE_OPT: 0
    BUCKET_MM: 100
    BUCKET_J: 1e+09
    PREC_ACC_DT: 60
    OMLCALL: 0
    ISFTCFLX: 0
    ISHALLOW: 0
    OPT_SFC: 1
    DVEG: 4
    OPT_CRS: 1
    OPT_BTR: 2
    OPT_RUN: 1
    OPT_FRZ: 1
    OPT_INF: 1
    OPT_RAD: 3
    OPT_ALB: 2
    OPT_SNF: 4
    OPT_TBOT: 1
    OPT_STC: 1
    DFI_OPT: 0
    WEST-EAST_PATCH_START_UNSTAG: 1
    WEST-EAST_PATCH_END_UNSTAG: 1359
    WEST-EAST_PATCH_START_STAG: 1
    WEST-EAST_PATCH_END_STAG: 1360
    SOUTH-NORTH_PATCH_START_UNSTAG: 1
    SOUTH-NORTH_PATCH_END_UNSTAG: 1015
    SOUTH-NORTH_PATCH_START_STAG: 1
    SOUTH-NORTH_PATCH_END_STAG: 1016
    BOTTOM-TOP_PATCH_START_UNSTAG: 1
    BOTTOM-TOP_PATCH_END_UNSTAG: 50
    BOTTOM-TOP_PATCH_START_STAG: 1
    BOTTOM-TOP_PATCH_END_STAG: 51
    GRID_ID: 1
    PARENT_ID: 0
    I_PARENT_START: 1
    J_PARENT_START: 1
    PARENT_GRID_RATIO: 1
    DT: 15
    CEN_LAT: 39.7000122070312
    CEN_LON: -98
    TRUELAT1: 28
    TRUELAT2: 50
    MOAD_CEN_LAT: 39.7000122070312
    STAND_LON: -98
    POLE_LAT: 90
    POLE_LON: 0
    GMT: 0
    JULYR: 2001
    JULDAY: 59
    MAP_PROJ: 1
    MMINLU: MODIFIED_IGBP_MODIS_NOAH
    NUM_LAND_CAT: 20
    ISWATER: 17
    ISLAKE: -1
    ISICE: 15
    ISURBAN: 13
    ISOILWATER: 14
    Conventions: CF-1.6
    history: Tue Apr  4 15:29:54 2017: ncks -A mylatlon4.nc myclean.nc
    history_of_appended_files: Tue Apr  4 15:29:54 2017: Appended file mylatlon4.nc had no "history" attribute

    NCO: "4.5.5"

我首先尝试投影HGT字段。来自netcdf文件的HGT字段的原始数据看起来像this。

在尝试正确投影栅格的过程中，我查看了this和其他文章，但尚未成功。我已经尝试了以下代码及其变体：

  wrfdir <- '/Volumes/Web/abby/DATA/WRF/'
  metafn <- paste0(wrfdir, 'RALconus4km_wrf_constants.nc')
  rr <- raster(metafn,varname='HGT')
  projection(rr) <- '+proj=lcc +lat_1=28.0 +lat_2=50.0 +lat_0=39.7000122070312 +lon_0=-98.0 +ellps=sphere +a=6370000 +b=6370000 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs'
  # then project to lat lon
  rrLL = projectRaster(rr, crs="+init=epsg:4326")
  plot(rrLL[[1]])

这将导致以下地图，其中纬度和经度显然不正确： first projection attempt

基于此post，我还尝试了以下操作：

 crs(rr) <- '+proj=longlat +ellps=sphere +a=6370000 +b=6370000 +units=m +no_defs' 
 rrLL <- projectRaster((rr),crs='+proj=lcc +lat_1=28.0 +lat_2=50.0 +lat_0=39.7000122070312 +lon_0=-98.0 +ellps=sphere +a=6370000 +b=6370000 +units=m +no_defs')

这将导致以下错误消息：

Error in if (nr != x@nrows | nc != x@ncols) { : missing value where TRUE/FALSE needed
In addition: Warning messages:
1: In rgdal::rawTransform(projfrom, projto, nrow(xy), xy[, 1], xy[,  :
634 projected point(s) not finite
2: In rgdal::rawTransform(projection(obj), crs, nrow(xy), xy[, 1],  :
4 projected point(s) not finite

任何关于如何执行此操作的想法将不胜感激！

无法在R中投影WRF数据

0 个答案: