fig, axes = plt.subplots(2,4, figsize = (15,8),constrained_layout=True)
vmin = -1
vmax = 1
p0 = axes[0,0].pcolormesh(ds_lp.x,ds_lp.t,ds_lp.z_inst,vmin = vmin, vmax = vmax,cmap = 'RdBu_r',shading='gouraud')
axes[0,1].pcolormesh(ds_lp.x,ds_lp.t,ds_lp.z_LM_at_mean,vmin = vmin, vmax = vmax,cmap = 'RdBu_r',shading='gouraud')
axes[0,2].pcolormesh(ds_lp.x,ds_lp.t,ds_lp.z_LM_at_mid,vmin = vmin, vmax = vmax,cmap = 'RdBu_r',shading='gouraud')
axes[0,3].pcolormesh(ds_lp.x,ds_lp.t,ds_lp.z_EM,vmin = vmin, vmax = vmax,cmap = 'RdBu_r',shading='gouraud')
axes[1,0].pcolormesh(ds_lp.x,ds_lp.t,ds_lp.z_inst - ds_lp.z_LM_at_mid,vmin = vmin, vmax = vmax,cmap = 'RdBu_r',shading='gouraud')
axes[1,1].pcolormesh(ds_lp.x,ds_lp.t,ds_lp.z_inst_at_mean - ds_lp.z_LM_at_mean,vmin = vmin, vmax = vmax,cmap = 'RdBu_r',shading='gouraud')
axes[1,2].pcolormesh(ds_lp.x,ds_lp.t,ds_lp.z_inst - ds_lp.z_LM_at_mean,vmin = vmin, vmax = vmax,cmap = 'RdBu_r',shading='gouraud')
axes[1,3].pcolormesh(ds_lp.x,ds_lp.t,ds_lp.z_inst - ds_lp.z_EM,vmin = vmin, vmax = vmax,cmap = 'RdBu_r',shading='gouraud')
fig.colorbar(p0,ax=axes[0,3],label='Relative vorticity')
fig.colorbar(p0,ax=axes[1,3],label='Relative vorticity')
textposx = 0.25
textposy = 37.8
bbox=dict(facecolor='white', edgecolor='none', boxstyle='round')
axes[0,0].text(textposx,textposy,r'a) $\zeta$',bbox=bbox)
axes[0,1].text(textposx,textposy-0.3,r'b) $\overline{\zeta}^\mathrm{L}$',bbox=bbox)
axes[0,2].text(textposx,textposy,r'c) $\zeta^*$',bbox=bbox)
axes[0,3].text(textposx,textposy-0.3,r'd) $\overline{\zeta}^\mathrm{E}$',bbox=bbox)
axes[1,0].text(textposx,textposy,r'e) $\zeta_{\mathrm{L1}}^\mathrm{w}$',bbox=bbox)
axes[1,1].text(textposx,textposy,r'f) $\zeta_{\mathrm{L2}}^\mathrm{w}$',bbox=bbox)
axes[1,2].text(textposx,textposy,r'g) $\zeta_{\mathrm{S-E}}^\mathrm{w}$',bbox=bbox)
axes[1,3].text(textposx,textposy,r'h) $\zeta_{\mathrm{E}}^\mathrm{w}$',bbox=bbox)
[axes[i,j].axes.set_yticklabels([]) for i in range(2) for j in range(1,4)];
[axes[i,j].axes.set_xticklabels([]) for i in range(1) for j in range(4)];
[axes[i,0].set_ylabel(r'$t^*$') for i in range(2)];
[axes[1,j].set_xlabel(r'$x$') for j in range(4)];
[axes[1,j].set_xticks([0,np.pi,2*np.pi]) for j in range(4)];
labels = ['0','$\pi$','$2\pi$']
[axes[1,j].set_xticklabels(labels) for j in range(4)];
fig.savefig('Figure-6.png',dpi=200,bbox_inches='tight')