wind pattern is wrong

Question

ahmed shaaban 2014-3-31

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/123916-wind-pattern-is-wrong

评论： Chad Greene 2014-7-29

Hello All I am trying to plot wind from era interim data , I compare my plot with plot by NCL and Grads and I found that the pattern plotted by the MatLab is wrong. here is the code . I have attached the file data and output. thanks in advance

if true
file2='era_interim_0.5_uv.nc'
lat2 =ncread(file2,'latitude')
long2 =ncread(file2,'longitude')
time2 =double(ncread(file2,'time'))
ncdisp(file2)
u10 = ncread(file2,'u10',... 
  [1 1 1],[length(long2) length(lat2) length(time2)],[1 1  1]);
v10 = ncread(file2,'v10',... 
  [1 1 1],[length(long2) length(lat2) length(time2)],[1 1  1]);
%%drawing wind 
a_lat2=21.5
a_lat1=-11.5
a_lon1=1.5
a_lon2=51.5
lat1i=find(lat2 == a_lat1)
lat2i=find(lat2 == a_lat2)
lon1i=find(long2 == a_lon1)
lon2i=find(long2 == a_lon2)
lats = [a_lat1 a_lat2];
lons = [a_lon1 a_lon2];
f1=figure;
H1 = worldmap(lats,lons);
coast = load('coast');
geoshow(coast.lat,coast.long);
states = shaperead('cntry02.shp','UseGeoCoords', true);
geoshow(states,'DisplayType', 'polygon', 'FaceColor', 'none','edgecolor','black','LineWidth',2)
a=double(squeeze(lat2(lat2i:lat1i)));
b=double(squeeze(long2(lon1i:lon2i)));
[b1 a1]=meshgrid(b,a);
u100=u10(lon1i:lon2i,lat2i:lat1i,1);
v100=v10(lon1i:lon2i,lat2i:lat1i,1);
quiverm(a1,b1,u100',v100',2)
geoshow(states,'DisplayType', 'polygon', 'FaceColor', 'none','edgecolor','black','LineWidth',2)
end

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Answer 1

Chad Greene 2014-5-22

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/123916-wind-pattern-is-wrong#answer_137899

Read the quiverm documentation carefully. It confoundingly defines u as the meridional component and v as the zonal component. Further, it wants u and v to be in units of degrees, not distance or speed. This effectively shrinks the zonal component of the vectors close to the poles. You can try to fix the second issue with the reckon function, or you can use ncquiverref instead of quiverm to fix both issues.