Met Office Hadley Centre observations datasets

HadISDH-blend. - gridded global surface humidity dataset (TEST PRODUCT)

HadISDH-blend is a blended land and marine global gridded monthly mean ocean surface humidity dataset. It combines HadISDH-land. and HadISDH-marine. Please see the respective pages for more details. Gridded (5° by 5°) monthly mean anomalies relative to the 1981-2010 climatology period are available from 1973 to 2016.

Gridded products are available for six humidity variables in addition to temperature - HadISDH-blend*.

LATEST VERSION: The current version of HadISDH-blend is and continues until December 2016. PLEASE NOTE THAT THIS IS A TEST PRODUCT AND HAS NOT YET PASSED THROUGH PEER REVIEW!!! In the HadISDH-marine data, a distinct dry period is apparent since 2011/2012(very clear in relative humidity) which is drier than in the similar in situ NOCSv2.0 product. This feature of HadISDH-marine may not be truly representative - a full investigation has not yet been completed. Please provide feedback on any issues and errors found to Kate Willett. Updates and full documentation will appear here in due course...

Brief description of the data

HadISDH-blend is a gridded monthly mean product based on hourly in situ observations that have been quality controlled and then homogenised (land) or bias adjusted (marine) to remove systematic error. The marine and land products have been blended at the 5%deg by 5%deg monthly mean anomaly resolution. Gridboxes containing both a land and sea value are combined using weights based on the proportion of land in that gridbox. Neither land nor marine component is permitted to represent less than 25%/more than 75% in the case where both are present.

The data are then averaged over 5° by 5° gridboxes centred on -177.5°W and -87.5°S to 177.5°E and 87.5°N for each month as anomalies and actual values. No interpolation is applied.

Data are available as monthly mean anomaly values relative to a 1981 to 2010 climatology.

Uncertainty has been assessed for both products but this has not yet been propogated through to the blended product.

Keep in touch

Follow us on twitter: @metofficeHadOBS for updates, news and announcements.

For more detailed information, follow our HadISDH blog. Here we describe bug fixes, routine updates and other exploratory analysis.

2016 ANNUAL ANOMALIES (1981-2010 climatology)








Go to download page Data are available from the download page without charge, please read the licence conditions.

Commercial and media enquiries

You can access the Met Office Customer Centre, any time of the day or night by phone, fax or e-mail. Trained staff will help you find the information or products that are right for you.
Contact the Met Office Customer Centre


When using the dataset please use the following four citations and state the version used:

Willett, K. M., Dunn, R. J. H., Thorne, P. W., Bell, S., de Podesta, M., Parker, D. E., Jones, P. D., and Williams Jr., C. N.: HadISDH land surface multi-variable humidity and temperature record for climate monitoring, Clim. Past, 10, 1983-2006, doi:10.5194/cp-10-1983-2014, 2014.
Main Text PDF file 2.6Mb
Supplementary Material PDF file 1.8Mb

Smith, A., N. Lott, and R. Vose, 2011: The Integrated Surface Database: Recent Developments and Partnerships. Bulletin of the American Meteorological Society, 92, 704\u2013708, doi:10.1175/2011BAMS3015.1.
Available from BAMS

Willett, K. M., Dunn, R. J. H., Kennedy, J. J., Berry, D. I. and Parker, D. E., in prep: Exploring marine humidity data for climate monitoring as part of the HadISDH dataset. To be submitted to Climate of the Past.
File available in due course

Freeman, E., S.D. Woodruff, S.J. Worley, S.J. Lubker, E.C. Kent, W.E. Angel, D.I . Berry, P. Brohan, R. Eastman, L. Gates, W. Gloeden, Z. Ji, J. Lawrimore, N.A. Rayner, G. Rosenhagen, and S.R. Smith, 2016: ICOADS Release 3.0: A major update to the historical marine climate record. Int. J. Climatol. (doi:10.1002/joc.4775).
Available from IJC

Useful Diagnostics

To follow...

We have adapted our versioning system from CRUTEM4, and so the dataset numbering is of the form HadISDH.type.X.Y.Z.1234i. 'type' refers to the variable (e.g., landq=specific humidity). 'X' is for a major change and would be accompanied by a peer-reviewed paper or Met Office Technical Note. 'Y' is a more minor change, e.g., in one of the QC tests or homogenisation algorithms and would be described in a tech-note. 'Z' is a small change, for example addition or changes to data in the past. The last complete year of the dataset is given by '1234', and the final character shows if the dataset is f-final or p-preliminary. Therefore HadISDH.landq. is the preliminary version of the dataset containing data up to the end of 2012.

Dataset and Diagnostic Creation Code

The python code used was written by Kate Willett, John Kennedy and Robert Dunn. Some of it will be made available later here. We do not intend to provide in-depth support for this code. We do appreciate constructive feedback on this code.

Dataset produced in collaboration with: