Python⽓象数据可视化学习笔记5——基于cartopy绘制contour并对中国地区
进。。。
基于cartopy绘制contour并对中国地区进⾏⽩化（包含南海）
1. 写在前⾯
2. 效果图
先看效果图，（a）©两图给出了完整的中国地图和完整的南海九段线，其中（a）添加了海岸线；（b）(d)两图中南海被放到了右下⾓，这也是常⽤的⽅法。
3. 导⼊库
主要⽤的库有读取netcdf的库，绘图的cartopy和matplotlib。最重要的是maskout.py这个库，可以从帖⼦1中第四种⽅法中获取。
import os
import maskout
from netCDF4 import Dataset
import numpy as np
import matplotlib as mpl
s as ccrs
import cartopy.feature as cfeature
from idliner import LONGITUDE_FORMATTER, LATITUDE_FORMATTER
from cartopy.mpl.ticker import LongitudeFormatter, LatitudeFormatter
from cartopy.io.shapereader import Reader
import matplotlib.pyplot as plt
import matplotlib.ticker as mticker
4. 读取数据
测试数据在帖⼦1中获取，shp⽂件在帖⼦2中获取，不再重复。感谢两位楼主⼤佬。
## 读数据
f = Dataset(')
lat = f.variables['latitude'][:]
lon = f.variables['longitude'][:]
t = f.variables['t'][2,1,:,:]# ⽓温
>>>>>>>>>>>###
#⽩化中国地图，加南海九段线，加海岸线
气象python零基础入门教程SHP =r'C:\Users\qiuyu\.local\share\cartopy\shapefiles\natural_earth\cultural\china_shp'
5. 定义绘图函数
这⼀部分的思路就是，先绘制标准地图和标准的填⾊图，然后利⽤maskout.shp2clip进⾏⽩化，把中国地图以外的区域的填⾊给取消。可以选择添加或者不添加海岸线。
def make_map(ax,box,lon,lat,var,proj,title,if_coast, if_nanhai):
projection = ccrs.PlateCarree()
# 加国界
ax.add_geometries(Reader(os.path.join(SHP,'cnmap.shp')).geometries(),
ccrs.PlateCarree(),facecolor='none',edgecolor='k', linewidth=0.7)
# 加海岸线
if if_coast:
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ax.add_geometries(Reader(os.path.join(SHP,'coastline.shp')).geometries(),
ccrs.PlateCarree(),facecolor='none',edgecolor='k', linewidth=0.7)
#标注坐标轴
ax.set_extent([box[0],box[1],box[2],box[3]])
ax.set_xticks(np.linspace(box[0], box[1],5), crs=projection)
ax.set_yticks(np.linspace(box[2], box[3],5), crs=projection)
#zero_direction_label=True 有度的标识，False则去掉'''
lon_formatter = LongitudeFormatter(zero_direction_label=True)
lat_formatter = LatitudeFormatter()
ax.xaxis.set_major_formatter(lon_formatter)
ax.yaxis.set_major_formatter(lat_formatter)
#添加⽹格线
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# plot
cf = ax.contourf(lon,lat,var,cmap = RdBu_r,
transform=ccrs.PlateCarree())
maskout.shp2clip(cf,ax,shpfile=os.path.join(SHP,'country1.shp'),region='China',proj= proj)
ax.set_title(title)
return ax
6. 绘图
定义经纬度区间，建⽴画布和轴，调⽤make_map函数进⾏画图。此时，画出的（b）（d）两图没有包含南海⼩地图。
box1=[70,140,0,50]#经纬度范围
box2=[70,140,15,50]#经纬度范围
proj=ccrs.PlateCarree()
fig = plt.figure(figsize=(15,7))
ax1 = fig.add_subplot(221,projection = ccrs.PlateCarree())
ax2 = fig.add_subplot(222,projection = ccrs.PlateCarree())
ax3 = fig.add_subplot(223,projection = ccrs.PlateCarree())
ax4 = fig.add_subplot(224,projection = ccrs.PlateCarree())
make_map(ax1,box1,lon,lat,t,proj,title='(a) With coastline',if_coast=True, if_nanhai=True)
make_map(ax2,box2,lon,lat,t,proj,title='(b) With coastline + Nanhai',if_coast=True, if_nanhai=False)
make_map(ax3,box1,lon,lat,t,proj,title='(c) Without coastline',if_coast=False, if_nanhai=False)
make_map(ax4,box2,lon,lat,t,proj,title='(d) Without coastline + Nanhai',if_coast=False, if_nanhai=True)
7. 添加南海⼩地图
添加南海⼩地图的思路就是（1）先⽤fig.add_axes⽣成新的ax_nanhai插⼊到figure中，插⼊的位置由pos确定；（2）然后再重复画⼤地图的⽅法，⽤ax_nanhai绘制，选定新的区域（box_nanhai）。
#----------添加南海⼩地图------------------
def add_nanhai(ax,pos,if_coast):
#--------------右下⾓添加南海地图------------------------------------------
box_nanhai=[103,125,2,25]
ax_nanhai = fig.add_axes(pos,projection = ccrs.PlateCarree())
# 加国界
ax_nanhai.add_geometries(Reader(os.path.join(SHP,'cnmap.shp')).geometries(),
ccrs.PlateCarree(),facecolor='none',edgecolor='k', linewidth=0.7)
if if_coast:
ax_nanhai.add_geometries(Reader(os.path.join(SHP,'coastline.shp')).geometries(),                        ccrs.PlateCarree(),facecolor='none',edgecolor='k', linewidth=0.7)
ax_nanhai.set_extent([box_nanhai[0],box_nanhai[1],box_nanhai[2],box_nanhai[3]]) pos1 =[0.757,0.54,0.1,0.1]#南海⼩地图在figure中的位置和⼤⼩
pos2 =[0.757,0.124,0.1,0.1]
add_nanhai(ax2,pos1,if_coast=True)
add_nanhai(ax4,pos2,if_coast=False)
plt.savefig('map.png')
8. 完整代码
import os
import maskout
from netCDF4 import Dataset
import numpy as np
import matplotlib as mpl
s as ccrs
import cartopy.feature as cfeature
from idliner import LONGITUDE_FORMATTER, LATITUDE_FORMATTER from cartopy.mpl.ticker import LongitudeFormatter, LatitudeFormatter
from cartopy.io.shapereader import Reader
import matplotlib.pyplot as plt
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import matplotlib.ticker as mticker
>>>>>>>>>>>###
## 读数据
f = Dataset(')
lat = f.variables['latitude'][:]
lon = f.variables['longitude'][:]
t = f.variables['t'][2,1,:,:]# ⽓温
>>>>>>>>>>>###
#⽩化中国地图，加南海九段线，加海岸线
SHP =r'C:\Users\qiuyu\.local\share\cartopy\shapefiles\natural_earth\cultural\china_shp'
def make_map(ax,box,lon,lat,var,proj,title,if_coast, if_nanhai):
projection = ccrs.PlateCarree()
# 加国界
ax.add_geometries(Reader(os.path.join(SHP,'cnmap.shp')).geometries(),
ccrs.PlateCarree(),facecolor='none',edgecolor='k', linewidth=0.7)
# 加海岸线
if if_coast:
ax.add_geometries(Reader(os.path.join(SHP,'coastline.shp')).geometries(),
ccrs.PlateCarree(),facecolor='none',edgecolor='k', linewidth=0.7)
#标注坐标轴
ax.set_extent([box[0],box[1],box[2],box[3]])
ax.set_xticks(np.linspace(box[0], box[1],5), crs=projection)
ax.set_yticks(np.linspace(box[2], box[3],5), crs=projection)
#zero_direction_label=True 有度的标识，False则去掉'''
lon_formatter = LongitudeFormatter(zero_direction_label=True)
lat_formatter = LatitudeFormatter()
ax.xaxis.set_major_formatter(lon_formatter)
ax.yaxis.set_major_formatter(lat_formatter)
#添加⽹格线
#添加⽹格线
# plot
cf = ax.contourf(lon,lat,var,cmap = RdBu_r,
transform=ccrs.PlateCarree())
maskout.shp2clip(cf,ax,shpfile=os.path.join(SHP,'country1.shp'),region='China',proj= proj)
ax.set_title(title)
return ax
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box1=[70,140,0,50]
box2=[70,140,15,50]
proj=ccrs.PlateCarree()
fig = plt.figure(figsize=(15,7))
ax1 = fig.add_subplot(221,projection = ccrs.PlateCarree())
ax2 = fig.add_subplot(222,projection = ccrs.PlateCarree())
ax3 = fig.add_subplot(223,projection = ccrs.PlateCarree())
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ax4 = fig.add_subplot(224,projection = ccrs.PlateCarree())
make_map(ax1,box1,lon,lat,t,proj,title='(a) With coastline',if_coast=True, if_nanhai=True)
make_map(ax2,box2,lon,lat,t,proj,title='(b) With coastline + Nanhai',if_coast=True, if_nanhai=False) make_map(ax3,box1,lon,lat,t,proj,title='(c) Without coastline',if_coast=False, if_nanhai=False)
make_map(ax4,box2,lon,lat,t,proj,title='(d) Without coastline + Nanhai',if_coast=False, if_nanhai=True) #----------添加南海⼩地图------------------
def add_nanhai(ax,pos,if_coast):
#--------------右下⾓添加南海地图------------------------------------------
box_nanhai=[103,125,2,25]
ax_nanhai = fig.add_axes(pos,projection = ccrs.PlateCarree())
# 加国界
ax_nanhai.add_geometries(Reader(os.path.join(SHP,'cnmap.shp')).geometries(),
ccrs.PlateCarree(),facecolor='none',edgecolor='k', linewidth=0.7)
if if_coast:
ax_nanhai.add_geometries(Reader(os.path.join(SHP,'coastline.shp')).geometries(),
ccrs.PlateCarree(),facecolor='none',edgecolor='k', linewidth=0.7)
ax_nanhai.set_extent([box_nanhai[0],box_nanhai[1],box_nanhai[2],box_nanhai[3]])
pos1 =[0.757,0.54,0.1,0.1]
pos2 =[0.757,0.124,0.1,0.1]
add_nanhai(ax2,pos1,if_coast=True)
add_nanhai(ax4,pos2,if_coast=False)
plt.savefig('map.png')
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