1. © Crown copyright Met Office HumEx - HUMidty EXperiment Amanda Kerr-Munslow, Research Scientist, Cardington

2. © Crown copyright Met Office HumEx Table of Contents Why, what, where and when? General weather conditions Case studies Survival? Conclusions

3. © Crown copyright Met Office Why, what, where and when? To investigate the response of a variety of humidity sensors in high humidity conditions. How accurate are they? How good is their response rate? Do they survive?

4. © Crown copyright Met Office Why, what, where and when? Standard surface site 10m mast, radiation, soil, visibility, rain gauge, 1.2 m screen Chilled mirror instruments: Michell hygrometer with sintered metal cover to 04/10/2011 (MIC_OM) Michell hygrometer with plastic cover from 04/10/2011 (MIC_OP) Meteolabor Thygan hygrometer (THY_OO)

5. © Crown copyright Met Office Why, what, where and when? Aspirated Instruments (3m/s)Non-aspirated instruments Covered instruments Vaisala Humicap HMP44 (V44_AC) Vaisala Humicap HMP155 (V15_AC)* Rotronics Hygroclip (Rot_AC) Rotronics Hygroclip (Rot_NC) Vaisala Humicap HMP155 (V15_NC) Hobo with hygroscopic tape (H08) Hobo with hygroscopic tape (H09) Not covered instruments Vaisala Humicap HMP44 (V44_AN) Vaisala Humicap HMP44 (V44_RN)* Rotronics Hygroclip (Rot_AN) Honeywell HIH-4000-001 (Hwl_AN) Vaisala Humicap HMP44 (V44_NN) Honeywell HIH-4000-001 (Hwl_NN) Hobo without tape (H10) Hobo without tape (H11) * V44_RN and V55_AC in variable rate aspirated screen 1-6m/s

6. © Crown copyright Met Office Why, what, where and when? As a follow on from COLPEX, at the Springhill Site A ridge top between valleys in Shropshire, near the Welsh border. 402m a.s.l. 585 days from 17th September 2010 to 24th April 2012.

7. © Crown copyright Met Office Weather conditions

8. © Crown copyright Met Office Weather conditions

9. © Crown copyright Met Office Weather conditions

10. © Crown copyright Met Office RH PDF

11. © Crown copyright Met Office Timeseries of key readings 1.2m Temperature (C) RH (%) Rain (mm) Minimum Visibility (km) 30 -20 0 100 0 0 0 60 40 mean, min, max Oct 2010April 2012June 2011

12. © Crown copyright Met Office Early Low RH data

13. © Crown copyright Met Office Early Low RH data

14. © Crown copyright Met Office Saturation issues

15. © Crown copyright Met Office Late case

16. © Crown copyright Met Office Late saturated period 1km 5 km 10 km

17. © Crown copyright Met Office Increasing to saturated

18. © Crown copyright Met Office Increasing to saturated

19. © Crown copyright Met Office Drying out

20. © Crown copyright Met Office Drying out

21. © Crown copyright Met Office Did they survive?

22. © Crown copyright Met Office Did they survive?

23. © Crown copyright Met Office Did they survive? Aspirated Instruments (3m/s)Non-aspirated instruments Covered instruments Vaisala Humicap HMP44 (V44_AC) Vaisala Humicap HMP155 (V15_AC)* Rotronics Hygroclip (Rot_AC) Rotronics Hygroclip (Rot_NC) Vaisala Humicap HMP155 (V15_NC) Hobo with hygroscopic tape (H08) Hobo with hygroscopic tape (H09) Not covered instruments Vaisala Humicap HMP44 (V44_AN) Vaisala Humicap HMP44 (V44_RN)* Rotronics Hygroclip (Rot_AN) Honeywell HIH-4000-001 (Hwl_AN) Vaisala Humicap HMP44 (V44_NN) Honeywell HIH-4000-001 (Hwl_NN) Hobo without tape (H10) Hobo without tape (H11) Chilled Mirror instruments Michell hygrometer with metal cover (MIC_OM) Michell hygrometer with plastic cover (MIC_OP) Meteolabor Thygan hygrometer (THY_OO) * V44_RN and V55_AC in variable rate aspirated screen 1-6m/s

24. © Crown copyright Met Office Do we trust the data? Aspirated Instruments (3m/s)Non-aspirated instruments Covered instruments Vaisala Humicap HMP44 (V44_AC) Vaisala Humicap HMP155 (V15_AC)* Rotronics Hygroclip (Rot_AC) Rotronics Hygroclip (Rot_NC) Vaisala Humicap HMP155 (V15_NC) Hobo with hygroscopic tape (H08) Hobo with hygroscopic tape (H09) Not covered instruments Vaisala Humicap HMP44 (V44_AN) Vaisala Humicap HMP44 (V44_RN)* Rotronics Hygroclip (Rot_AN) Honeywell HIH-4000-001 (Hwl_AN) Vaisala Humicap HMP44 (V44_NN) Honeywell HIH-4000-001 (Hwl_NN) Hobo without tape (H10) Hobo without tape (H11) Chilled Mirror instruments Michell hygrometer with metal cover (MIC_OM) Michell hygrometer with plastic cover (MIC_OP) Meteolabor Thygan hygrometer (THY_OO) * V44_RN and V55_AC in variable rate aspirated screen 1-6m/s

25. © Crown copyright Met Office Conclusions The location was a little too wet. Hobos have relatively slow responses. Untaped hobos respond more quickly than taped hobos, but die sooner. Uncovered and covered Vaisala and Rotronics instruments have similar response rates at medium RHs, but uncovered instruments saturate too quickly. Aspirated and not aspirated instruments also have similar response rates at medium RHs. Aspiration shortens the saturated period for Vaisala 44 and Rotronics instruments but not Vaisala 155s.

26. © Crown copyright Met Office Questions and answers