RELEASE NOTES FOR CRU TS v4.05: 16 March 2021

The CRU TS dataset was developed and has been subsequently updated,
improved and maintained with support from a number of funders,
principally the UK's Natural Environment Research Council (NERC) and the
US Department of Energy. Long-term support is currently provided by the
UK National Centre for Atmospheric Science (NCAS), a NERC collaborative
centre. 

The 4.05 release of the CRU TS dataset covers the period 1901-2020.

This is the fourth release of the new interpolation algorithm, which is
unchanged since v4.03.

To understand this dataset, it is important to understand its
construction and limitations. It is therefore recommended that all users
read the relevant paper:

Harris, I., Osborn, T.J., Jones, P. et al. Version 4 of the CRU TS
monthly high-resolution gridded multivariate climate dataset.
Sci Data 7, 109 (2020). https://doi.org/10.1038/s41597-020-0453-3


1. What's new in 4.05

1.1 Process changes

No process changes have been made for this release.

1.2 Bug fixes

As part of the upgrading of the Google Earth interface to CRU TS, it was
discovered that synthetic VAP stations (used to 'top up' when actual VAP
observation counts are insufficient) were being allocated on a 'first
come, first served' basis, when the nearest should have been selected.
All stations used were within the CDD, so the results could not be said
to be 'wrong' - but they could have been better. A comparison between
4.04 VAP and the 'corrected' VAP (v4.01.01, unreleased) is here:
https://crudata.uea.ac.uk/cru/data/hrg/blog_files/blog_files_030620/cc2a.cruts404vs40401.VAP.pdf

An exercise to plot anomaly counts for various variables revealed a
cluster of stations near 100°W, at various latitudes. Investigations
revealed that the new-format MCDW data includes stations with lat and
lon missing; this was unexpected (as previous MCDW updates always had
location information) and the exception was handled poorly at the two
points where it could have been caught. Comparisons between v4.03,
v4.04, and a product with that bug corrected, (v4.04.02, unreleased) are
available as PDFs:
https://crudata.uea.ac.uk/cru/data/hrg/blog_files/blog_files_060620/cc3a.cruts4.03.vs.cruts4.04.vs.cruts4.04.02.TMP.pdf
https://crudata.uea.ac.uk/cru/data/hrg/blog_files/blog_files_060620/cc3a.cruts4.03.vs.cruts4.04.vs.cruts4.04.02.DTR.pdf
https://crudata.uea.ac.uk/cru/data/hrg/blog_files/blog_files_060620/cc3a.cruts4.03.vs.cruts4.04.vs.cruts4.04.02.PRE.pdf
https://crudata.uea.ac.uk/cru/data/hrg/blog_files/blog_files_060620/cc3a.cruts4.03.vs.cruts4.04.vs.cruts4.04.02.VAP.pdf
https://crudata.uea.ac.uk/cru/data/hrg/blog_files/blog_files_060620/cc3a.cruts4.03.vs.cruts4.04.vs.cruts4.04.02.WET.pdf
https://crudata.uea.ac.uk/cru/data/hrg/blog_files/blog_files_060620/cc3a.cruts4.03.vs.cruts4.04.vs.cruts4.04.02.CLD.pdf
https://crudata.uea.ac.uk/cru/data/hrg/blog_files/blog_files_060620/cc3a.cruts4.03.vs.cruts4.04.vs.cruts4.04.02.TMN.pdf
https://crudata.uea.ac.uk/cru/data/hrg/blog_files/blog_files_060620/cc3a.cruts4.03.vs.cruts4.04.vs.cruts4.04.02.TMX.pdf
https://crudata.uea.ac.uk/cru/data/hrg/blog_files/blog_files_060620/cc3a.cruts4.03.vs.cruts4.04.vs.cruts4.04.02.VAP.pdf
https://crudata.uea.ac.uk/cru/data/hrg/blog_files/blog_files_060620/cc3a.cruts4.03.vs.cruts4.04.vs.cruts4.04.02.WET.pdf
Note that many of the changes in the corrected version (green) simply
return the series to the 4.03 values (thin black). 


2. Output files

For now, the approach of issuing NetCDF and ASCII files in parallel will
remain, as will the publications of decadal files as well as full-length
versions. However, decadal files may not be archived when superceded, in
order to make best use of space.


As always, please contact BADC in the first instance if you have any
questions, observations or suggestions. If, however, you wish to contact
CRU directly about these datasets, please contact me at
i.harris@uea.ac.uk, as mail to other members of the Unit will be passed
through to me anyway.

Ian Harris
NCAS-Climate
Climatic Research Unit
School of Environmental Sciences
University of East Anglia
Norwich
NR4 7TJ

i.harris@uea.ac.uk