Is the BRDF atlas a climatology?

[Andrew Prata]

Hi James

I’m trying to describe the RTTOV BRDF atlas and from the resources I’ve found online it’s not clear to me if the BRDF atlas actually represents a climatology or if it’s just for the year 2007.

In the latest user guide there is the following statement (Section 8.3.7 BRDF atlas):
“RTTOV provides a BRDF atlas (Vidot and Borbas, 2013) which is similar in many ways to the IR emissivity atlases. It provides monthly climatological land surface BRDF values based on the MODIS BRDF MCD43 product including
climatological snow.”

In Vidot and Borbas (2014*), I found the following statement (Section 4. The RTTOV BRDF atlas):
“The methodology was as follows: for all original MODIS MCD43C1 data within a month, we extracted the information for a 4 by 4 pixel box (from an original pixel resolution at 0.05° to a final grid at 0.1°).”

So, I assume that “all original MODIS MCD43C1 data within a month”, means that all years for the given month were averaged(?), which would indeed imply a climatology.

However, there are two points that appear to contradict the above:
1. The BRDF atlas files provided (e.g. CMSsolarbrdf_V1.0_0.1deg_200701_mask.nc) indicate that the data are from 2007.
2. In a later paper by Vidot et al. (2017), they state the following:
“In the future, we plan to extend the database to other years since only the year 2007 is implemented in RTTOV.”

So, I’m left unsure if the BRDF atlas file is actually a climatology or if it just represents the year 2007.

Are you able to clarify?

Thanks
Andrew

*I see that the accepted manuscript went online on 31 October 2013, but the “Version of Record” online is 12 February 2014.

References

Vidot, J. and Borbás, É.: Land surface VIS/NIR BRDF atlas for RTTOV‐11: model and validation against SEVIRI land SAF albedo product, Quart J Royal Meteoro Soc, 140, 2186–2196, https://doi.org/10.1002/qj.2288, 2014.

Vidot, J., Brunel, P., Dumont, M., Carmagnola, C., and Hocking, J.: The VIS/NIR Land and Snow BRDF Atlas for RTTOV: Comparison between MODIS MCD43C1 C5 and C6, Remote Sensing, 10, 21, https://doi.org/10.3390/rs10010021, 2017.

[James Hocking]

Hi Andrew,

I am pretty sure that the current BRDF atlas is based on data from 2007 only. I am checking with Jerome Vidot and will let you know when I hear back from him.

Best wishes,
James

[James Hocking]

Hi Andrew,

Jerome has confirmed that the current BRDF atlas is based on data from 2007 only. He is working on an updated atlas for RTTOV that is based on data from 2017-2021.

Best wishes,
James

[Andrew Prata]

Hi James

Many thanks for looking into this for me and for confirming that it’s for 2007. I will look out for the new atlas in the future.

Thank you!

[Author]

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