我正在用python中的matplotlib barb函数和basemap绘制风矢量倒钩图。
我有一个任意纬度和经度的矢量(风观测)列表,即不在规则网格上。
我需要旋转矢量到地图投影之前,绘制或倒钩指向错误的方向。最好的方法是什么?
例如

import numpy
from mpl_toolkits.basemap import Basemap
import matplotlib.pyplot as plt

# Define locations of my vectors
lat = numpy.array([50.1,46.2,51.6,52.2,54.4])
lon = numpy.array([-3.3,-1.0,-5.2,-1.2,0.2])

# Define some east-west vectors to illustrate the problem
u = numpy.array([5,5,5,5,5])
v = numpy.array([0,0,0,0,0])

# Set up map projection
m = Basemap(llcrnrlon=-15.,llcrnrlat=46.,urcrnrlon=15.,urcrnrlat=59.,
            projection='lcc',lat_1=40.,lat_2=50.,lon_0=-50.,
            resolution ='l')

# Calculate positions of vectors on map projection
x,y = m(lon,lat)

# Draw barbs
m.barbs(x,y,u,v, length=7, color='red')

# Draw some grid lines for reference
parallels = numpy.arange(-80.,90,20.)
meridians = numpy.arange(0.,360.,20.)
m.drawparallels(parallels)
m.drawmeridians(meridians)
m.drawcoastlines(linewidth=0.5)

plt.show()

请注意,在绘图中,矢量不指向东西方向。
我试过使用rotate_vector和transform_vector例程,但这些只适用于网格化的矢量数据。
对于任意的纬度、经度、经度对列表,是否有将矢量旋转到地图投影上的程序?
任何帮助都将不胜感激!

最佳答案

你的问题是你在lat,long中指定了你的uv。同时,在地图坐标中指定xybarbs似乎期望两者都在地图坐标中,而不是混合在一起。
最简单的方法是计算端点来获取组件。(我的描述毫无意义,所以我的想法是:)

x, y = m(lon, lat)
x1, y1 = m(lon+u, lat+v)
u_map, v_map = x1-x, y1-y

你还需要重新调整震级。作为一个完整的例子:
import numpy
from mpl_toolkits.basemap import Basemap
import matplotlib.pyplot as plt

# Define locations of my vectors
lat = numpy.array([50.1,46.2,51.6,52.2,54.4])
lon = numpy.array([-3.3,-1.0,-5.2,-1.2,0.2])

# Define some east-west vectors to illustrate the problem
u = numpy.array([5,5,5,5,5])
v = numpy.array([0,0,0,0,0])

# Set up map projection
m = Basemap(llcrnrlon=-15.,llcrnrlat=46.,urcrnrlon=15.,urcrnrlat=59.,
            projection='lcc',lat_1=40.,lat_2=50.,lon_0=-50.,
            resolution ='l')

# Calculate positions of vectors on map projection
x,y = m(lon,lat)

# Calculate the orientation of the vectors
x1, y1 = m(lon+u, lat+v)
u_map, v_map = x1-x, y1-y

# Rescale the magnitudes of the vectors...
mag_scale = np.hypot(u_map, v_map) / np.hypot(u, v)
u_map /= mag_scale
v_map /= mag_scale

# Draw barbs
m.barbs(x,y,u_map,v_map, length=7, color='red')

# Draw some grid lines for reference
parallels = numpy.arange(-80.,90,20.)
meridians = numpy.arange(0.,360.,20.)
m.drawparallels(parallels)
m.drawmeridians(meridians)
m.drawcoastlines(linewidth=0.5)

plt.show()

10-05 20:44
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