WMO Technical Conference on
Download
1 / 23

Inter-comparison of raingauges in a sub-tropical environment Tam Kwong-hung - PowerPoint PPT Presentation


  • 91 Views
  • Uploaded on

WMO Technical Conference on Meteorological and Environmental Instruments and Methods of Observation TECO-2012 Brussels, Belgium, 16 – 18 October 2012. Inter-comparison of raingauges in a sub-tropical environment Tam Kwong-hung Senior Scientific Officer

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Inter-comparison of raingauges in a sub-tropical environment Tam Kwong-hung' - aric


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

WMO Technical Conference on Meteorological and Environmental Instruments and Methods of ObservationTECO-2012Brussels, Belgium, 16 – 18 October 2012

Inter-comparison of raingauges

in a sub-tropical environment

Tam Kwong-hung

Senior Scientific Officer

Hong Kong Observatory, Hong Kong, China

16 October 2012



Background continued
Background (continued)

HKO = 46

GEO = 86

DSD = 20

Total = 152

All are 0.5 mm resolution raingauges


Background cont
Background (cont.)

  • Started inter-comparison in 2000

  • Formal comparison in 2011 (with revised recording method and test bed)

  • Gathered results so far from 2011 – 2012 (latest results of 2012 included in this presentation)

  • Target:

    • evaluate 0.1 mm resolution raingauge models meeting WMO +/-5 % accuracy requirement

    • suitable for use in the sub-tropical environment with rainfall intensity exceeding 300 mm/hr

    • Raingauge robust enough to be deployed in the field


Background cont1
Background (cont.)

Hong Kong

International Airport (HKIA)

King’s Park (KP)




Spatial distribution of various rain gauges used for the field inter comparison at king s park
Spatial distribution of various rain gauges Station test bedused for the field inter-comparison at King’s Park


Location of raingauges at the hong kong international airport meteorological station test bed
Location Station test bedof raingauges at the Hong Kong International Airport Meteorological Station test bed.


Equipment set up for in house calibration of raingauges
Equipment set-up for in-house calibration of Station test bedraingauges

High precision dispensing pump to provide constant water flow rate in order to determine the accuracy of the raingauge under different simulated rainfall intensities

Water bottle to act as water reservoir

Electronic balance for determining the amount of water pumped out of the bottle

Raingauge under calibration


Error curves (compared with WMO’s Station test bed+ 5% uncertainty limits) obtained in the laboratory under different simulated rainfall rates for those raingauges at the King’s Park inter-comparison site

Note: second order polynomial functions are used for curve fitting


Error curves (compared with WMO’s Station test bed+ 5% uncertainty limits) obtained in the laboratory under different simulated rainfall rates for those raingauges at the HKIA inter-comparison site

Note: Second order polynomial functions are used for curve fitting. Ogawa raingauges were checked up to

100 mm/hr as their errors exceed 5 % for rainfall intensity reaching above 100 mm/hr (Chan et.al, 2004).


Summary of rainfall comparison results at King’s Park Station test bed

(Data period : 1 April 2011 to 17 September 2012. )


Summary of rainfall comparison results at Station test bedthe Met Garden in AMO

(Data period : 19 March 2011 to 13 September 2012 )


Time series of rainfall intensities recorded by various 0.1/0.2-mm resolution raingauges at the King’s Park on the morning of 17 June 2011.


Time series of rainfall intensities recorded by various 0.1 mm resolution raingauges at the HKIA on the morning of 28 June 2011.


Results and discussions
Results and Discussions mm resolution

  • Total number of rain episodes (24 hr rainfall >=10mm) recorded in 2011-2012: 75 (KP) and 62 (HKIA)

  • Highest rainfall rate recorded: ~ 150 mm/hr (at KP by R102_ETG) and ~ 300 mm/hr (at HKIA by Ogawa)

  • Observations from KP Test Bed:

  • Very small spatial variability of rainfall during test period (< 1mm difference between 2 manual raingauges; mean absolute percentage difference of same model raingauges ~1-2%)

  • Mean absolute percentage differences (MAPD) of most (except R102_ETG and one Logotronic) raingauges < 5 %

  • SL3-1 performs the best among 0.1 mm raingauges

  • MAPD of Casella 0.5 mm < 3% (good for use though coarser resolution)

  • Observations from HKIA Test Bed:

  • MAPD of MeteroSevis < 4% (meeting WMO requirement)

On the other hand, the Ogawa, Logotronic, R102_ETG and MeteoServis raingauges which were equipped with sophisticated electronics would be vulnerable to the impact of lightning. The former two raingauges also required considerable amount of manpower to maintain their operations. Hence, the Working Group considered that it would be more appropriate to deploy them at manned stations rather than automatic weather stations.


Results and discussions cont
Results and Discussions (cont.) mm resolution

  • SL3-1 is a good choice to replace existing Casella 0.5mm resolution raingauges (simple design, relatively low equipment cost (~1:3) and ease of maintenance.

  • Ogawa, Logotronic, R102_ETG and MeteoServis raingauges more appropriate to be deployed at manned stations rather than AWS:

    • equipped with sophisticated electronics

    • vulnerable to the impact of lightning,

    • required considerable amount of manpower to maintain operations

On the other hand, the Ogawa, Logotronic, R102_ETG and MeteoServis raingauges which were equipped with sophisticated electronics would be vulnerable to the impact of lightning. The former two raingauges also required considerable amount of manpower to maintain their operations. Hence, the Working Group considered that it would be more appropriate to deploy them at manned stations rather than automatic weather stations.


The design of the 0.1mm resolution SL3-1 mm resolution raingauge. A two-layer tipping mechanism is used to provide a larger buffering capacity to cope with higher intensity rainfall events.


Way forward
Way Forward mm resolution

  • Extend the field inter-comparison to 2013

  • Start a new phase of testing – deploy SL3-1 at some existing AWS remote sites to test its robustness and durability and compare its performance with Casella 0.5mm resolution raingauges

  • Start rainfall intensity measurement and comparison


Thank you
Thank you ! mm resolution


ad