Methane plumes observed by TROPOMI¶
This example case focuses on detecting methane (CH4) plumes from oil/gas production in Turkmenistan using TROPOMI data. Turkmenistan has one of the largest natural gas reserves in the world and it is one of main oil and gas production basins. Turkmenistan ranks also as the highest methane "ultra-emitter" with 1.3 Mt emissions of CH4 per year (Lauvaux et al., Science, 2022). The methane plumes over Turkmenistan are frequently visible in TROPOMI data. This notebook focus on single overpass TROPOMI CH4 data from March 2023.
1. Python packages for the notebook ¶
The preparations needed to set up avl is shown in Use case 6. Following packages are needed to run this notebook (eofetch is used for data download):
import harp
import avl
import eofetch
2. TROPOMI Level 2 methane data ¶
The TROPOMI methane product data file provides the column average dry air mixing ratio of methane, XCH4. This notebook uses TROPOMI methane data from 12th March 2023 (orbit number 28034):
S5P_RPRO_L2__CH4____20210612T125610_20210612T143739_18985_03_020400_20221124T220051.nc
The TROPOMI level 2 data used in this notebook can be downloaded using the eofetch package. To be able to perform eofetch.download, you must have environment variables, CDSE_S3_ACCESS and CDSE_S3_SECRET, set as described in in eofetch README.
filename="S5P_OFFL_L2__CH4____20230312T082359_20230312T100529_28034_03_020500_20230315T154121.nc"
eofetch.download(filename)
3. Plotting single overpass XCH4 data on a map using AVL ¶
When when importing the methane data the following operations are done:
1)CH4_column_volume_mixing_ratio_dry_air_validity>50: for using only those pixels that are of high quality. More about the quality criteria recommended for CH4 product can be found from Product Readme File for methane.
2) latitude>34;latitude<43,longitude>5;latitude<67: to cut the data over Turkmenistan.
operations_avl = ";".join([
"CH4_column_volume_mixing_ratio_dry_air_validity>50",
"latitude>34;latitude<43","longitude>5;latitude<67"])
The parameter to be viewed is the bias corrected XCH4, i.e., the column volume mixing ratio that is corrected for the dependence on surface albedo. To change the default XCH4 to the bias correceted XCH4, ingestion option "ch4=bias_corrected" needs to be applied when importing the data:
ch4product=harp.import_product(filename, operations_avl, options="ch4=bias_corrected")
To plot the methane observations on the map, the avl.Geo is used as in Use case 6. The variable name to be plotted is "CH4_column_volume_mixing_ratio_dry_air" :
varname = 'CH4_column_volume_mixing_ratio_dry_air'
avl.Geo(ch4product, varname, colormap='magma_r', colorrange=(1910, 1940), opacity=0.5, showcolorbar=True, centerlat=38, centerlon=59.5, zoom=8)
On 12th March 2023 a methane plume east from Asgabat is visible in TROPOMI observations, as the emissions stand out clearly from the background.