About NCEP/CPC L3 Half Hourly merged IR

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partha3602
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About NCEP/CPC L3 Half Hourly merged IR

by partha3602 » Thu Jul 08, 2021 11:01 am America/New_York

Hello,

I am Dr. Partha Roy from India. I am utilizing the NCEP/CPC L3 Half Hourly 4km Global (60S - 60N) merged IR V1 data for my scientific study. It is really very useful data.

But, I have one query about this data. In the original data file, so many NaN values are coming with real values. I could not get why it is there. I have attached one figure (white color represents NaN values). Please go through the figure.

It would be very helpful if you kindly let me know the reason for this.

Thanking you,

Best regards,

Partha Roy
National Atmospheric Research Laboratory
Dept. of Space, Govt. of India
India 517502
Attachments
IR data plot over South Asia region
IR data plot over South Asia region
plot.jpg (32.47 KiB) Not viewed yet

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GES DISC - jimacker
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Re: About NCEP/CPC L3 Half Hourly merged IR

by GES DISC - jimacker » Thu Jul 08, 2021 3:19 pm America/New_York

Hello,

My colleague who would be the best to address this question is out of the office for a few more days. I have sent your message to him and I will post his reply after he has considered it.

Jim Acker

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Re: About NCEP/CPC L3 Half Hourly merged IR

by GES DISC - jimacker » Thu Jul 08, 2021 5:03 pm America/New_York

Another GES DISC colleague has provided this response:

The missing values in this dataset are declared as "_FillValue
= -9999." in the local attributes to the "Tb" variable, in accordance with the Climate and Forecast (CF) conventions. The CF-compliant tools will honor this attribute and will automatically place NaN where fill values are encountered.

In case you write your own program, you must carefully observe this local attribute and manage the pixels with fill value in the data, as declared in the attribute, in any suitable way that does not allow these pixels to enter your calculations. Missing values in this dataset result for different reasons, one possible reason being that corrections for erroneously cold pixels off-nadir fail for the satellites that are available for merging into the particular 30-minute interval.

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Re: About NCEP/CPC L3 Half Hourly merged IR

by GES DISC - zliu » Mon Jul 12, 2021 9:17 am America/New_York

In addition, more information is available in the data provider site,

https://www.cpc.ncep.noaa.gov/products/ ... _res.shtml

Please read through the documents to better understand the dataset.

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