# # File: # traj1.py # # Synopsis: # Draws lines and polymarkers over a map to trace the paths of bouys. # # Categories: # Maps # Polylines # Polygons # Polymarkers # # Author: # Fred Clare # # Date of initial publication: # September, 2004 # # Description: # Draws lines and polymarkers over a map to trace the paths of # buoys set afloat off the eastern coast of South America. # The colors of path segments indicate salinity measurements. # # Effects illustrated: # o Reading from a NetCDF file. # o Polylines. # o Polygons. # o Polymarkers. # o Maps using a Cylindrical Equidistant projection. # o Using named colors. # # Output: # A single visualization showing the paths of buoys set afloat # off the eastern coast of South America. # # Notes: # This program implements a version of a trajectory plot # based on an NCL code developed by NCAR's Climate and # Global Dynamics Division. # # # Import numpy. # from __future__ import print_function import numpy, os # # Import Nio. # import Nio # # Import Ngl support functions. # import Ngl #---------------------------------------------------------------------- # nint returns the nearest integer to a given floating value. #---------------------------------------------------------------------- def nint(r): if (abs(int(r)-r) < 0.5): return int(r) else: if (r >= 0.): return int(r)+1 else: return int(r)-1 #---------------------------------------------------------------------- # Create map of southern tip of South America #---------------------------------------------------------------------- def create_map(wks): #---Map resources res = Ngl.Resources() # map resources res.nglDraw = False # don't draw map res.nglFrame = False # don't advance frame res.mpDataBaseVersion = "MediumRes" # better map outlines res.mpLimitMode = "LatLon" res.mpMaxLatF = -20 # select subregion res.mpMinLatF = -62 res.mpMinLonF = -78 res.mpMaxLonF = -25 res.mpOutlineOn = True res.mpGridAndLimbOn = False res.mpFillOn = True res.mpLandFillColor = "beige" res.mpOceanFillColor = "paleturquoise1" res.mpInlandWaterFillColor = "paleturquoise1" res.tmYROn = True # Turn on right tickmarks res.tmXTOn = True # Turn on top tickmarks res.tiMainString = "Trajectories colored by salinity (ppt)" res.tiMainFontHeightF = 0.02 map = Ngl.map(wks,res) # Draw map. return map #---------------------------------------------------------------------- # Add the trajectory lines. #---------------------------------------------------------------------- def add_trajectories(wks,map,filename,cmap): #---Open the netCDF file containing the salinity data for the trajectories. ncfile = Nio.open_file(filename) traj = [1,10,53,67,80] # choose which trajectories to plot pres = Ngl.Resources() # polyline resources pres.gsLineThicknessF = 5.0 # line thickness mres = Ngl.Resources() # marker resources mres.gsMarkerSizeF = 17.0 # marker size mres.gsMarkerColor = "black" # marker color mres.gsMarkerIndex = 15 # circle with an X mres.gsMarkerThicknessF = 2.0 # thicker marker outlines # # Loop through the chosen trajectories. # sdata = ncfile.variables["sdata"] sid = [] for i in range(len(traj)): lat = sdata[2,:,traj[i]] # extract lat from whole array lon = sdata[1,:,traj[i]] # extract lon from whole array sst = sdata[8,:,traj[i]] # # Map the salinity values between 34.55 and 34.85 into color # indices between 0 and 9 and draw polylines, with those # colors, between adjacent lat/lon values. # for j in range(len(lat)-2): sval = 0.5*(sst[j]+sst[j+1]) cindex = nint(30.*(sval-34.55)) pres.gsLineColor = cmap[cindex] sid.append(Ngl.add_polyline(wks,map,[lon[j],lon[j+1]],[lat[j],lat[j+1]],pres)) #---Draw a polymarker at the beginning of each trajectory. sid.append(Ngl.add_polymarker(wks,map,[lon[0]],[lat[0]],mres)) return #---------------------------------------------------------------------- # Manually create a labelbar using polygons, lines, and text to # draw various primitives. The lat/lon space of the map is used # to indicate where to draw the labelbar. By using the various # Ngl.add_xxxx functions, this actually attaches the primitives to # the map, so if you were to resize the map later (say in a panel # plot), the primitives would be resized automatically. # # This is the harder way to draw a labelbar, but it shows how to # do more custom labelbars, if desired. #---------------------------------------------------------------------- def add_labelbar(wks,map,cmap): gsres = Ngl.Resources() # Line resources. delta_lon = 4.0 delta_lat = 2.1 start_lon = -68. start_lat = -58. txres = Ngl.Resources() # For labeling the label bar. txres.txFontHeightF = 0.015 gid = [] lid = [] tid = [] for i in range(4,14,1): lon0 = start_lon+(i-4)*delta_lon lon1 = lon0+delta_lon lat0 = start_lat lat1 = start_lat+delta_lat lons = [lon0,lon1,lon1,lon0,lon0] lats = [lat0,lat0,lat1,lat1,lat0] gsres.gsFillColor = cmap[i-4] # Change fill color. gid.append(Ngl.add_polygon(wks,map,lons,lats,gsres)) lid.append(Ngl.add_polyline(wks,map,lons,lats,gsres)) if (i == 4): tid.append(Ngl.add_text(wks,map,"34.55",lon0,lat0-delta_lat,txres)) elif(i == 6): tid.append(Ngl.add_text(wks,map,"34.61",lon0,lat0-delta_lat,txres)) elif(i == 8): tid.append(Ngl.add_text(wks,map,"34.67",lon0,lat0-delta_lat,txres)) elif(i == 10): tid.append(Ngl.add_text(wks,map,"34.73",lon0,lat0-delta_lat,txres)) elif(i == 12): tid.append(Ngl.add_text(wks,map,"34.79",lon0,lat0-delta_lat,txres)) else: tid.append(Ngl.add_text(wks,map,"34.85",start_lon+10*delta_lon,lat0-delta_lat,txres)) return #---------------------------------------------------------------------- # Main code #---------------------------------------------------------------------- #---Get the path to the NetCDF file. dirc = Ngl.pynglpath("data") filename = os.path.join(dirc,"cdf","traj_data.nc") #---Define a list of named colors to use for trajectory lines and labelbar cmap = ["brown4","yellow1","navyblue","forestgreen","hotpink","purple",\ "slateblue","thistle","deeppink4","darkgoldenrod"] wks = Ngl.open_wks ("png","traj1") map = create_map(wks) add_labelbar(wks,map,cmap) add_trajectories(wks,map,filename,cmap) Ngl.draw(map) Ngl.frame(wks) Ngl.end()