使用python pcolormesh绘制TERRA MODIS AOD

Question

我想使用python pcolormesh绘制2019055至2019063的每日MODIS AOD数据。但是，某些图片有奇怪的水平线。我不知道为什么有些图片有线条，而其他图片没有。我附上我的图片和代码。

import glob
import numpy as np
from pyhdf.SD import SD, SDC

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

for j in range(55, 63):
    date = str(j)
    file_list = glob.glob('MOD04_L2.A20190'+date+'*.hdf')

    hdf = SD(file_list[0], SDC.READ)
    Aerosol_merge = hdf.select('Optical_Depth_Land_And_Ocean')
    latitude_merge = hdf.select('Latitude')
    longitude_merge = hdf.select('Longitude')

    AOD_merge = Aerosol_merge[:,:]
    lat_merge = latitude_merge[:,:]
    lon_merge = longitude_merge[:,:]

    for i in range(1, np.size(file_list)):
        hdf = SD(file_list[i], SDC.READ)        

        Aerosol = hdf.select('Optical_Depth_Land_And_Ocean') #read AOD data
        latitude = hdf.select('Latitude')
        longitude = hdf.select('Longitude')

        lat = latitude[:,:]
        lon = longitude[:,:]
        AOD = Aerosol[:,:]                                  

        AOD = np.ma.masked_where(AOD < 0 , AOD)

        AOD = AOD*0.0010000000474974513    

        AOD_merge = np.vstack([AOD_merge,AOD])
        lat_merge = np.vstack([lat_merge,lat])
        lon_merge = np.vstack([lon_merge,lon])

    AOD_merge = np.ma.masked_where(AOD_merge < 0, AOD_merge)

    plt.hold(True)

    map = Basemap(projection='cyl', resolution='l', llcrnrlat=-90, urcrnrlat=90, llcrnrlon=-180, urcrnrlon=180)
    map.drawcoastlines(linewidth=0.5)

    map.drawparallels(np.arange(-90., 90., 35.), labels=[1, 0, 0, 0])
    map.drawmeridians(np.arange(-180., 180., 45.), labels=[0, 0, 0, 1])
    x, y = map(lon_merge, lat_merge)

    smap = map.pcolormesh(x, y, AOD_merge, cmap='jet')

    plt.clim(0, 1.5)

    smaplegend = map.colorbar(smap,location='bottom',pad="10%")
    smaplegend.set_label('AOD')
    plt.title("MODIS AOD "+date)

    fig = plt.gcf()
    plt.show()

    fig.savefig('MODIS AOD '+date+'_global'+'.png',dpi = 500)