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本帖最后由 fanxiqing 于 2017-4-29 11:05 编辑
nudging中的两个参数if_no_pbl_nudging_uv and if_zfac_uv含义,实在想不明白,为啥指定层以下是否逼近,还有边界层是否逼近要用两个参数设置,不是重合的吗?然后问了下wrfhelp,得到的回复,大致理解了一下,就是说这两个参数是是决定另外两个控制权重的参数wpbl和wzfac,它们是要相乘的,最后得出一个权重系数。具体的设置我也理解了下,不知道对不对。还有,是不是应该是两个同时发挥作用才需要相乘,其中一个不发挥作用权重不就是0,能不能简单地取并集呢?
if_no_pbl_nudging_uv = 0,不限制边界层逼近(不等于边界层逼近,只是关闭了控制边界层是否逼近的功能) if_zfac_uv = 1,10层以下不逼近 假定按WRF中的边界层高度定义,1000米定义为边界层(假定是1000米),1000米以内有7层(或11层等别的层数都没有影响) 则10层以下不逼近,具体以k_zfac_uv 指定层数为准,边界层不管多少层都不参与控制 if_no_pbl_nudging_uv = 1,边界层不逼近 if_zfac_uv = 1,10层以下不逼近 两个参数同时发挥作用 若边界层7层,则10层以下不逼近 若边界层11层,则11层以下不逼近(取并集) if_no_pbl_nudging_uv = 0,边界层逼近 if_zfac_uv = 0,没有指定层数限制 没有任何层数限制,所有层数都逼近 if_no_pbl_nudging_uv = 1,边界层不逼近 if_zfac_uv = 0,没有指定层数限制 只有边界层是否逼近的限制,没有指定层数的限制 若边界层7层,则7层以内不逼近 若边界层11层,则11层以内不逼近
Xiqing,
The model computes weighting coefficients, wpbl and wzfac, based on the setting of if_no_pbl_nudging_t and if_zfac_t for example, they are typically 0 or 1. The final weighting is the multiplication of the two. The definition of PBL is defined by PBL height and its associated K level index. If you use if_no_pbl_nudging_t only, the no-nudging levels will change depending on the PBL depth, and day and night. There may be reasons you just don't want to nudge low levels, period. That's when if_zfac_t is useful.
wrfhelp
On 4/27/17 10:22 PM, fanxiqing wrote:Dear Sir/Madam, I was using fdda utility in wrf, but I have problems understanding some of the parameters in namelist.input, as well as how to choose those parameters for my own purpose (simulation of a hurricane).Some of the parameters I get confused is the if_no_pbl_nudging_uv and if_zfac_uv ,which means whether to nudging in the PBL and whether to nudge under certain vertiacl layers, respectively. I was wondering if the specified vertical layer under which no nudging is need can be contradictory/coincide with if_no_pbl_nudging_uv because the PBL is about 1000m or so ,and it is probably within or beyond the specified layer(say,10th layer).So why this has been separated into two control parameters? What's the definition of PBL in this parameter, is it defined by pressure layer or height(in meters)? Thank you , Yours Xiqing Fan.
&fdda
grid_fdda = 1, 1, 1,
gfdda_inname = "wrffdda_d",
gfdda_end_h = 18, 18, 18,
gfdda_interval_m = 360, 360, 360,
fgdt = 0, 0, 0,
if_no_pbl_nudging_uv = 0, 0, 0,
if_no_pbl_nudging_t = 1, 1, 1,
if_no_pbl_nudging_q = 1, 1, 1,
if_zfac_uv = 1, 1, 1,
k_zfac_uv = 10, 10, 10,
if_zfac_t = 0, 0, 0,
k_zfac_t = 10, 10, 10,
if_zfac_q = 0, 0, 0,
k_zfac_q = 10, 10, 10,
guv = 0.0003, 0.0003, 0.0003,
gt = 0.0003, 0.0003, 0.0003,
gq = 0.0003, 0.0003, 0.0003,
if_ramping = 1,
dtramp_min = 360.0,
io_form_gfdda = 2,
/
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