Extracting Methane and Carbon Dioxide at a geolocation


I am currently trying to extract methane and Carbon dioxide emission at a point coordinate (75,43). When I'm plotting the time series data for the two gases, I can't understand the value on the y-axis. For example for CH4 - there is 'f' next to the value and CO2 there is a 'p'. See attached figures. I'm currently expecting the CH4 emission to be in ppb (10^9) and CO2 emission in ppm (10^6). When I'm downloading the Nedcdf files, there is 1e^-15 associated with each CH4 values- is there a conversion to make at this point? Any suggestions please?

Thank you.

Best Regards,

Here is my code for Carbon dioxide (same code has been written for CH4, except data name has been changed):

import cdstoolbox as ct

layout = {'input_ncols': 3,}
variables = {'xco2': 'xco2'}

# List of longitude and latitude to be used
longitude = [75.,80.]
latitude = [43.,50.]

@ct.application(title='Extract a time series for Carbon Dioxide at a geolocation', layout=layout)
@ct.input.dropdown('var', label='Gas', values=variables.keys(), description='Carbon Dioxide')
@ct.input.dropdown('lon', label='lon', values=longitude, description='longitude variables')
@ct.input.dropdown('lat', label='lat', values=latitude, description='latitude variables')

def plot_time_series(var, lon, lat):
# Time range
data = ct.catalogue.retrieve(
'processing_level': 'level_3',
'variable': 'xco2',
'sensor_and_algorithm': 'merged_obs4mips',
'version': '4.1',

# Location selectiondata_sel = ct.geo.extract_point(data, lon=lon, lat=lat)

data_nan = ct.math.nan_to_num(data_sel)
fig = ct.chart.line(data_nan)

return data_nan, fig

Hi Zafiirah,

The units were meant to be mol mol^-1. However I found that there was an error in the conversion when we read the data into the toolbox. I have corrected this and the units are now mol mol^-1 as expected. You can use the ct.cdm.convert_units to convert this into ppm as I have done this workflow:


I hope this helps,


Hi Edward,

Thank you for your suggestion and help. I've just tried it and it works perfectly. Thanks again.

Best Regards,