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HadISDH 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. Quality controlled and homogenised monthly mean anomalies (relative to a 1981-2010 base period) are provided alongside uncertainty estimates (station [climatological, measurement and homogeneity] and gridbox sampling). Actual values, climatological mean and standard deviation and no. stations per gridbox are also provided. The dataset begins in January 1973 and is updated annually.
Gridded products are available for six humidity variables in addition to temperature - HadISDH.land*.22.214.171.1248f:
LATEST VERSION: The current version of HadISDH is 126.96.36.1998f and continues until December 2018. Only one update will be made this year so this is a final (f) version. For previous versions please contact the dataset maintainers. Please read the Update Document.
NEW MARINE VERSION: HadISDH-marine.188.8.131.528f is now available as a TEST product. PLEASE NOTE THAT THIS HAS NOT YET BEEN THROUGH PEER REVIEW!!! Feedback on any issues/errors found is much appreciated - please contact Kate Willett. You can find out more about this dataset and download it from the HadISDH-marine.184.108.40.2068f webpage.
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. Further in formation on uncertainty estimates can be found here.
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.
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.
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.
Annual and monthly average timeseries for the globe, hemispheres and tropics, including uncertainty estimates.
Annual anomaly maps from 1973 onwards for specific humidity.
Annual anomaly maps from 1973 onwards for relative humidity.
Annual anomaly maps from 1973 onwards for vapour pressure.
Annual anomaly maps from 1973 onwards for dew point temperature.
Annual anomaly maps from 1973 onwards for wet bulb temperature.
Annual anomaly maps from 1973 onwards for temperature.
Annual anomaly maps from 1973 onwards for dew point depression.
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.220.127.116.113p is the preliminary version of the dataset containing data up to the end of 2012.
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.
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