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HadISDH-marine.1.0.0.2018f - gridded global surface humidity dataset (TEST PRODUCT)

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 from 1973 to 2018. These are then converted to various humidity variables, quality controlled, bias adjusted and averaged over 5° by 5° degree gridboxes for each month. Monthly mean anomalies relative to the 1981-2010 climatology period are currently available along with actual values, climatology and climatological standard deviations. Uncertainty estimates are also available for each gridbox month.

Gridded products are available for six humidity variables in addition to temperature - HadISDH-marine*.1.0.0.2018f:

Specific humidity (q), expressed in g kg^-1. The ratio of the mass of water vapour to the mass of moist air.
Relative humidity (RH), expressed as a percentage (%rh). The amount of water vapour in the air compared to how much water could potentially be held as a vapour at that temperature.
Dew point temperature (T_d), expressed in °C. The temperature at which the air becomes saturated at that current level of water vapour, measured by artificially cooling a surface until water condenses onto it.
Wet bulb temperature (T_w), expressed in °C. The amount of evaporative cooling of a thermometer in a moistened wick. Air that is not saturated will evaporate water from the wick, cooling the 'wet bulb' thermometer.
Vapour pressure (e), expressed in hPa. The partial pressure exerted by water vapour alone.
Dew point depression (DPD), expressed in °C. The amount the air has to be cooled by to reach its dew point temperature.
Temperature (T), expressed in °C. The temperature measured by the dry bulb thermometer.

LATEST VERSION: The current version of HadISDH-marine is 1.0.0.2018f and continues until December 2018. PLEASE NOTE THAT THIS IS A TEST PRODUCT AND HAS NOT YET PASSED THROUGH PEER REVIEW!!! 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-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) from January 1st 1973 to December 31st 2018. 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.

Regional average time series are also available with uncertainties averaged over the region including spatial coverage uncertainty.

Keep in touch

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

2018 ANNUAL ANOMALIES (1981-2010 climatology)

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

References

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

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

Useful Diagnostics

To follow...

Annual and monthly average timeseries for the globe, hemispheres and tropics, including uncertainty estimates.

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 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: