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HadISDH - gridded global surface humidity dataset

HadISDH is a global gridded monthly mean surface humidity dataset. Quality controlled and homogenised / bias adjusted monthly mean anomalies (relative to a 1981-2010 base period) are provided alongside uncertainty estimates (observation and gridbox sampling). Actual values, climatological mean and standard deviation and no. observations are also provided. The dataset begins in January 1973 and is updated annually.

HadISDH.land is a global gridded monthly mean land surface humidity dataset based on the quality controlled sub-daily HadISD dataset which is in turn based on the ISD dataset from NOAA's NCEI. Hourly dew poinbt temperature and air temperature are converted to various humidity variables and then averaged to monthly values. These are homogenised and averaged over 5° by 5° degree gridboxes for each month.

HadISDH.marine is a global gridded monthly mean ocean surface humidity dataset. Hourly in situ dew point temperature and marine air temperature data from ships are taken from ICOADS. These are then converted to various humidity variables, quality controlled, bias adjusted and averaged over 5° by 5° degree gridboxes for each month.

HadISDH.blend is a global gridded monthly mean land and marine surface humidity dataset combining HadISDH.land and HadISDH.marine.


Gridded products are available for six humidity variables in addition to temperature:

LATEST VERSIONS:
The current version of HadISDH.land is 4.2.0.2019f and continues until December 2019. Only one update will be made this year so this is a final (f) version. Please read the Update Document.
The current version of HadISDH.marine is 1.0.0.2019f and continues until December 2019. Only one update will be made this year so this is a final (f) version. Please read the Update Document.
The current version of HadISDH.blend is 1.0.0.2019f and continues until December 2019. Only one update will be made this year so this is a final (f) version
For previous versions please contact the dataset maintainers.



Brief description of the data

Land

HadISDH utilises simultaneous subdaily temperature and dew point temperature data from >8000 quality controlled HadISD stations that have sufficiently long records. Further information on the quality control tests and HadISD can be found here. All humdiity variables are calculated at hourly resolution and monthly means are created.

Monthly means are homogenised to detect and adjust for features within the data that do not appear to be of climate origin. While unlikely to be perfect, this process does help remove large errors from the data an improve robustness of long-term climate monitoring. We have used NCEI's Pairwise Homogenisation Algorithm directly on DPD and T. We have designed an indirect PHA method (ID PHA) whereby changepoints detected in DPD and T are used to make adjustments to q, e, Tw and RH. Changepoints from DPD are also applied to T. Td is derived from homogenised T and DPD. Further information can be found here. Stations with very large (>5 °C in T and Td, > 3 g kg-1 in q and > 15 %rh in RH) adjustments applied are removed.

Measurement, climatological and homogeneity adjustment uncertainty is estimated for each month.

Climatological averages over the 1981 to 2010 period are calculated and monthly mean climate anomalies obtained. These anomalies (in addition to climatological mean and standard deviation, actual values and uncertainty components) 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.

Given the uneven distribution of stations over time and space, sampling uncertainty is estimated for each gridbox month. Further in formation on uncertainty estimates can be found here.

Marine

HadISDH.marine utilises simultaneous subdaily air temperature and dew point temperature data from ships, moored buoys and ocean platforms from ICOADS.3.0.0 and ICOADS.3.0.1 (Freeman et al., 2016). All humidity variables are calculated at hourly resolution.

Hourly humidity and temperature values are quality controlled to to remove gross random errors (bad locations, bad timings, climatological outliers, neighbourhood outliers). Bias adjustments are also applied to the hourly data to account for increasing ship heights over time and changing proportions of poorly ventilated instruments. 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 1981 to 2010 climatology, actual values, climatologies and a climatological standard deviation.

Uncertainty has been assessed at the observation level for measurement uncertainty, rounding uncertainty, climatology uncertainty, height adjustment uncertainty and ventilation adjustment uncertainty. These are made available at the gridbox monthly mean level along with spatio-temporal sampling uncertainty.

Blend

HadISDH.blend combines HadISDH.land and HadISDH.marine. Where both land and marine gridboxes are present a weighted average is taken based on land fraction with a lower limit of 0.25/0.75 enforced when either the land fraction is below 25% or above 75%.

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.


2019 ANNUAL ANOMALIES (1981-2010 climatology)

HadISDH.landq

HadISDH.lande

HadISDH.landTd

HadISDH.landRH

HadISDH.landDPD

HadISDH.landTw

HadISDH.landT

Go to download page Data are freely available from the: land download page; marine download page; and blend download page. Please read the licence conditions. Data are also available from the CEDA Catalogue.

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


References

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

Land

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

We strongly recommend that you read the Willett et al. (2014) paper before making use of the data. Additionaly information can be found in the reference for version 1.0.0:

Willett, K. M., Williams Jr., C. N., Dunn, R. J. H., Thorne, P. W., Bell, S., de Podesta, M., Jones, P. D., and Parker D. E., 2013: HadISDH: An updated land surface specific humidity product for climate monitoring. Climate of the Past, 9, 657-677, doi:10.5194/cp-9-657-2013.
PDF file (5.4MB)

Marine

Willett, K. M., Dunn, R. J. H., Kennedy, J. J., and Berry, D. I.submitted: Development of the HadISDH marine humidity climate monitoring dataset. Earth System Science Data.
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

Blend

Please use all of the above references.


Useful Diagnostics

Figures from the Willett et al. 2014 paper.

Figures from the Willett et al. 2013 paper.

Figures from State of the Climate and IPCC monitoring plots.

Decadal Trend maps for each variable: LAND; MARINE; BLEND.

Annual and monthly average timeseries for the globe, hemispheres and tropics, including uncertainty estimates: LAND; MARINE; BLEND.

Annual anomaly maps from 1973 onwards for specific humidity: LAND; MARINE; BLEND.

Annual anomaly maps from 1973 onwards for relative humidity: LAND; MARINE; BLEND.

Annual anomaly maps from 1973 onwards for vapour pressure: LAND; MARINE; BLEND.

Annual anomaly maps from 1973 onwards for dew point temperature: LAND; MARINE; BLEND.

Annual anomaly maps from 1973 onwards for wet bulb temperature: LAND; MARINE; BLEND.

Annual anomaly maps from 1973 onwards for air temperature: LAND; MARINE; BLEND.

Annual anomaly maps from 1973 onwards for dew point depression: LAND; MARINE; BLEND.

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.2.0.0.2013p is the preliminary version of the dataset containing data up to the end of 2012.


Dataset and Diagnostic Creation Code

The IDL and python code used (excluding quality control, homogenisation and regional average uncertainty estimates) was written by Kate Willett and can be found 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:

Met Office NOAA NCDC CICS-NC CRU NPL NOC