获取了WRFout结果文件之后如何求取可降水量

janweis

　　各位大神好，实属新手，翻阅了很多文献之后发现都没有详细的教程，也没有一个切入点，在此特广发英雄帖，请求各路大神指点！（金钱不多，只能奖励１块了。谢谢）
问题：
　　跟据WRF-ARW的wrf.exe获取了WRFout结果文件，如何利用后处理获取某个地点某一时刻的可降水量。
以往资料总结：
　　１、在ARW的guide文档中只在两个地方提到了Precipitable water，一个实在讲NCL的wrf_user_getvar (nc_file, fld, it)工具时讲到了这一点，似乎只要将fld设为PW就好了，但是没有测试，主要是由于，不知道如何使用这个函数，文中有提到编写script,说明是可以使用的，求大神指导，
　　２、在guide文档中另一处也提到了precipitable water ,是在讲GrADS的unipost中提到,这个比NCL中的似乎还要难得理解，但是很多帖子上都是使用的GrADS,在无敌泡的《[脚本编辑]GRADS 计算大气可降水量》中提到了可以使用脚本的方法计算可降水量，hustlh的《关于可降水量单位问题》中讲解的更为详细，总结两帖都使用了'.nc'文件并采用了一个质量加权垂直积分函数vint,但是我并没有他们的.nc文件，这应当如何处理（这个已经解决在处理wrfout文件时，直接加上后缀就好）
求助:
　　1、我想实现的东西应该很简单，我先用wrf作出了大范围的格网数据，而后利用格网数据获取某个地方的可降水量，这个思路不知道对不对，望指导。
      ２、到底是选择使用NCL还是使用GrADS，反正这两个我都不会，哪一个都是从头开始，不过，我暂时只装了NCL（因为比较容易安装），望指导
　　３、选择软件后，如何使用，谢谢感激不尽，这一点非常需要指导{:soso_e183:}(忘了，我不是想绘图，只是想获得一个数值)
       4、在NCL的介绍中出现了一个list of available diagnostics.如下，我的理解是，“这些diagnostics是小写的来与可直接从netCDF文件中的变量做区分”，他的fld是大小写敏感的，那么也就是说diagnostics对于我们来说是直接可以利用的，那么应该在wrfout文件中就应该已经有了这些diagnostics,还望大神指导，这是如何做到的？如何让wrfout文件中直接拥有这些diagnostic。在某帖中我看到有说修改registry的，可以直接在生成wrfout文件中获取，不知道是不是这样？{:soso_e183:}
function wrf_user_getvar (nc_file, fld, it)
      Usage: ter = wrf_user_getvar (a, “HGT”, 0)      

Get fields from a netCDF file for
        1. Any given time by setting it to the time required.
        2. For all times in the input(投入) file(s), by setting it = -1
        3. A list of times from the input file(s), by setting it to (/start_time,end_time,interval/) ( e.g. (/0,10,2/) ).
        4. A list of times from the         input(投入) file(s), by setting it to the list required ( e.g. (/1,3,7,10/) ).
        
        Any field available in the netCDF file can be extracted(萃取的).
        fld is case sensitive(敏感的). The policy(政策) adapted(适应) during development was to set all diagnostic(诊断的) variables(变量) calculated(计算) by NCL to lower-case(小写字母的) to distinguish(区分) them from fields directly available from the netCDF files.

List of available diagnostics:

      

avo: Absolute(绝对的) Vorticity [10-5 s-1]
        eth: Equivalent(等价的) PotentialTtemperature [K]
        cape_2d: Returns 2D fields mcape/mcin/lcl/lfc
              cape_3d: Returns 3D fields cape(海角)/cin
              dbz: Reflectivity [dBZ]
              mdbz: Maximum Reflectivity [dBZ]
          geopt/geopotential: Full Model Geopotential [m2 s-2]
          helicity: Storm Relative Helicity [m-2/s-2]
          lat: Latitude  (will return either XLAT or XLAT_M, depending on which is available)
          lon: Longitude (will return either XLONG or XLONG_M, depending on which is available)
          p/pres: Full Model Pressure [Pa]
          pressure: Full Model Pressure [hPa]
        pvo: Potential(潜能) Vorticity [PVU]
        pw: Precipitable Water
        rh2: 2m Relative Humidity [%]
        rh: Relative Humidity [%]
        slp: Sea Level Pressure [hPa]
        ter: Model Terrain Height [m] (will return either HGT or HGT_M, depending on which is available)
        td2: 2m Dew Point Temperature [C]
        td: Dew Point Temperature [C]
        tc: Temperature [C]
        th/theta: Potential(潜能) Temperature [K]
        tk: Temperature [K]
        times: Times in file (note this return   strings - recommended)
        Times: Times in file (note this return characters)
        updraft_helicity: Updraft Helicity [m-2/s-2]
        ua: U component(成分) of wind on mass points
        va: V component of wind on mass points
        wa: W component of wind on mass points
        uvmet10: 10m U and V components of wind rotated(旋转的) to earth coordinates(坐标)
        uvmet: U and V components of wind rotated to earth coordinates
        z/height: Full Model Height [m]

janweis

对于第四个问题，我在官网上找到了答案，他的dignogistic是可以直接使用的
wrf_user_getvar is modifiable by the user, if you want to add your own diagnostics. To add your own diagnostics:

    Copy the file "$NCARG_ROOT/lib/ncarg/nclscripts/wrf/WRFUserARW.ncl" to your own directory.

    Edit this file with any UNIX editor and look for the lines:

    undef("wrf_user_getvar")
    function wrf_user_getvar( file_handle, varin

:string, time:integer )

    Before the final lines in this function:

      return(var)

    end

    Add these lines, replacing newvar as appropriate:

      if( variable .eq. "newvar" ) then
        . . . fill in code here . . .
      end if

    To use the new version of this function, you can do one of two things:

        Copy your modified script over "$NCARG_ROOT/lib/ncarg/nclscripts/wrf/WRFUserARW.ncl" and use the new "wrf_user_getvar" with your new entry:

        load "$NCARG_ROOT/lib/ncarg/nclscripts/wrf/WRFUserARW.ncl"
        xxx = wrf_usr_getvar(f,"XXX",0)

        Remove all but the modified "wrf_user_getvar" function from your copy, rename the function ("wrf_user_getvar2"), and rename the file ("my_new_script.ncl"). You will need to load the above script and your new script to use the new function:

        load "$NCARG_ROOT/lib/ncarg/nclscripts/wrf/WRFUserARW.ncl"
        load "my_new_script.ncl"
        xxx = wrf_usr_getvar2(f,"XXX",0)

wrf_user_getvar is part of a library of functions and procedures in WRFUserARW.ncl written to help users plot ARW WRF model data.

Questions on this function should be sent to wrfhelp@ucar.edu.

See Also

wrf_user_getvar, wrf_user_ij_to_ll, wrf_user_intrp2d, wrf_user_intrp3d, wrf_user_list_times, wrf_user_ll_to_ij, wrf_user_unstagger

See the full list of WRF functions.
Examples

Example 1

Get variables from a single WRF ARW file:

  load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
  load "$NCARG_ROOT/lib/ncarg/nclscripts/wrf/WRFUserARW.ncl"

  a = addfile("wrfout_d01_2000-01-24_12:00:00.nc","r")

  time = 1
  slp = wrf_user_getvar(a,"slp",time)  ; slp
  tc2 = wrf_user_getvar(a,"T2",time)   ; T2 in Kelvin
  u10 = wrf_user_getvar(a,"U10",time)  ; u at 10 m
  v10 = wrf_user_getvar(a,"V10",time)  ; v at 10 m

  ua  = wrf_user_getvar(a,"ua",time)   ; u on mass points
  va  = wrf_user_getvar(a,"va",time)   ; v on mass points

  avo = wrf_user_getvar(a,"avo",-1)    ; calculate avo for all times in file

Example 2

As of NCL V6.0.0, you can get a variable from a list of WRF ARW NetCDF files:

  load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
  load "$NCARG_ROOT/lib/ncarg/nclscripts/wrf/WRFUserARW.ncl"

  files = systemfunc("ls -1 wrfout_d01_2000*") + ".nc"
  a = addfiles(files,"r")

  slp = wrf_user_getvar(a,"slp",-1)

and_zj

我也看不懂……

深情

RAINC+RAINNC

tbag

pwp=vint(surface pressure, qvapor, pressure top)