Total Column of NO2

[pedrorodrigues.48203]

hello
I need the data of the total column of NO2 between 2007 and 2019 obtained by the OMI, for a city in Portugal. How do I proceed to acquire this data?
thanks

[GES DISC - jimacker]

Hello,

I would recommend starting with our Giovanni system. Giovanni has both tropospheric and total column NO2 at 0.25 deg resolution. Use this link to access these data variables: OMI NO2 in Giovanni.

You can create a bounding box using latitude and longitude coordinates for the corners, and you can specify the time range to create a time-series (note the plot options at top left). The time-series values can be downloaded as CSV or netCDF.

The GES DISC also provides a subsetting service that operates on Level 2 data (Giovanni uses Level 3 data). The subsetting service can thus provide data at higher spatial resolution than Giovanni, but the data would require additional processing steps after it is downloaded to extract the data values of interest. Click on this link to access the data products and subsetting service: OMI NO2 data at GES DISC.

Please reply for additional assistance, if necessary.

[pedrorodrigues.48203]

Hello

Thank you for your last help!

I currently need the data from the vertical columns of NO2 and O3 obtained by Tropomi.

What procedure should I follow?

Best regards

[GES DISC - jimacker]

Hello,

I'm glad our previous reply was useful to you. Note that TROPOMI data is not available back to 2007.

To get TROPOMI data from the GES DISC, go to the home page: https://disc.gsfc.nasa.gov/.

Type "TROPOMI NO2" in the search box.

The first search result should be "TROPOMI/S5P NO2 Tropospheric, Stratospheric and Total Columns MINDS 1-Orbit L2 Swath 5.5 km x 3.5 km (TROPOMI_MINDS_NO2 1.1)"

Use the "Subset/Get Data" capability, under the text shown above, to receive data files for a specific place and time period. The process of requesting the data should be straightforward, but if you have questions or encounter a difficulty, please reply.

[pedrorodrigues.48203]

Hello

Thank you again for your help!

I used the "Subset/Get Data" functionality to retrieve the data for the specific area and desired period.

Then, to read the nc file, I used the PANOPLY application, exporting the data in CSV format.

I obtained three columns of data (nTimes, nXtrack, SCIENCE_DATA/ColumnAmountNO2), with over 1 million data entries for each data day, although with a considerable number of NAN entries.

I was surprised by the amount of data collected in one day!

Could you help me?

Best regards



GES DISC - jimacker wrote:
> Hello,
>
> I'm glad our previous reply was useful to you. Note that TROPOMI data is
> not available back to 2007.
>
> To get TROPOMI data from the GES DISC, go to the home page:
> [url]https://disc.gsfc.nasa.gov/[/url].
>
> Type "TROPOMI NO2" in the search box.
>
> The first search result should be "TROPOMI/S5P NO2 Tropospheric,
> Stratospheric and Total Columns MINDS 1-Orbit L2 Swath 5.5 km x 3.5 km
> (TROPOMI_MINDS_NO2 1.1)"
>
> Use the "Subset/Get Data" capability, under the text shown above,
> to receive data files for a specific place and time period. The process of
> requesting the data should be straightforward, but if you have questions or
> encounter a difficulty, please reply.

[GES DISC - alouise517]

Dear User,

Could you please provide the input parameters you used to make your download and subset request (i.e., screenshots or typing them out is fine too) from the GES DISC website? And which "Subset/Get Data" option you used for your subset? There are two options: the green “Subset/Get Data Beta” or the one below it that says “Subset/Get Data” which holds our legacy services. This information will help our team further diagnose your issue.

Thank you!

Regards,
GES DISC User Services

[pedrorodrigues.48203]

Hello

I used “Subset/Get Data Beta”

>>>Dataset

TROPOMI/S5P NO2 Tropospheric, Stratospheric and Total Columns MINDS 1-Orbit L2 Swath 5.5 km x 3.5 km V1.1 (TROPOMI_MINDS_NO2) at GES DISC

>Variables

GEOLOCATION_DATA/Latitude
GEOLOCATION_DATA/Longitude
GEOLOCATION_DATA/SolarZenithAngle
GEOLOCATION_DATA/Time
GEOLOCATION_DATA/UTC
SCIENCE_DATA/ColumnAmountNO2
Date Range
2018-05-01T00:22:27.000Z to 2018-05-03T20:43:38.000Z
Spatial
Bounding Box: -7.91, 38.57, -7.91, 38.57

>>>OUTPUT

nTimes nXtrack SCIENCE_DATA/ColumnAmountNO2
"1 of 2905" "1 of 450" NaN
"1 of 2905" "2 of 450" NaN
"1 of 2905" "3 of 450" NaN
... ....
"252 of 2905" "65 of 450" 2.5260367E15
"252 of 2905" "66 of 450" 2.07609002E15
"252 of 2905" "67 of 450" NaN
"252 of 2905" "68 of 450" NaN
... ....
"2168 of 2905" "374 of 450" 4.7819409E15
"2168 of 2905" "375 of 450" 5.1018403E15
"2168 of 2905" "376 of 450" 4.8482283E15
"2168 of 2905" "377 of 450" 4.8793239E15
... ....
"2905 of 2905" "447 of 450" 6.8538643E15
"2905 of 2905" "448 of 450" 7.0617025E15
"2905 of 2905" "449 of 450" 6.3825147E15
"2905 of 2905" "450 of 450" 7.0404043E15

I'm waiting for your help!

Best regards

[GES DISC - alouise517]

Good Afternoon,

Our team has taken a look at your latest post, and is currently investigating this issue. Please stay tuned for our response. We will provide our feedback as soon as possible.

In the meantime, please let us know if you have any further questions or issues.

Regards,
GES DISC User Services

[GES DISC - alouise517]

Hello,

Thank you for sending along your input parameters. It appears that after looking at the bounding box coordinates (xmin, ymin, xmax, ymax) that you may be trying to find a single point location. However, this service does support single point subsetting. In this case the coordinates entered are invalid to define a four-sided bounding box for the requested data search area and the entire Level 2 swath is returned. This is the reason why you see many more data points than expected.

When you are defining a bounding box using the Subset/Get Data (Beta) tool, try defining a bounding box centered over the location you wish to extract data, but make the size so that each side of the box is a little bit larger in distance than the spatial resolution of the data.

For the TROPOMI_MINDS_NO2 collection the spatial resolution is 3.5km x 5.5km (pixel size). Note that your location of interest may reside within the domain of a single pixel, but it is important to remember that the pixel’s location is usually based on the central latitude and longitude of that particular pixel. Therefore, we recommend to draw or define a 6km x 6km (~0.06° x 0.06°) "box" centered over your area of interest (i.e., [-7.94, 38.54, -7.88, 38.60])
if you are trying to minimize the extent of the data, but still retrieve data.

Keep in mind with a bounding box this size, the subset request will likely yield a single pixel per granule. However, in this case, note that if data at that location is missing for that particular granule, then no granule will be returned. You can always draw a bigger box depending on the geographic context needed for your study.

We also encourage you to read the "README" documentation for this data collection, which is located in the "Documentation" tab on the dataset landing page. This "README" will contain definitions of the variables/fields of interest - but also fields that represent quality flags, standard error, and/or weight for the most accurate way to represent your data. You can select those fields as output variables when doing your subset.

Thank you and please don't hesitate to reach back out if any of this is unclear or if you have any questions.

Best,
GES DISC User Services