WMO Intercomparison of Instruments and methods for the Measurement of Solid Precipitation and

Snow on the Ground, WMO-SPICE: Pre-SPICE Studies

R. Rasmussen(1) ,R. Nitu (2),B. Baker(3),E Lanzinger (4),D Yang(7),C Smith(7),Y.A. Roulet (5),B Goodison((15) ,H Liang(6),F Sabatini(8),J Kochendorfer (3),M Wolff(9) ,J Hendrikx (10), E Vuerich(11),L Lanza(12),P. Joe(2),O Aulamo(13),V Vuglinsky(14) , Michael Earle(2) ,Jeffery Hoover(2), S Landolt(1)

(1) National Center for Atmospheric Research, Boulder, USA, rasmus@ucar.edu (2) Environmemt Canada, Toronto, Canada, Rodica.nitu@ec.gc.ca , 3) NOAA Air Resources Laboratory, Oak Ridge, TN, 37830 ,4)Deutscher Wetterdienst, Hamburg, Germany,(5)Météo Suisse,PAYERNE, Switzerland, (6)China Meteorological Administration, BEIJING, China. 7)Environment Canada, Saskatoon, Canada . (8) CNR-IBIMET, Institute of Biometeorology, Florence, Italy, (9)Norwegian Meteorological Institute,Oslo, Norway, (10)Montana State University, Montana, U.S.A., (11) Italian Met Service – Air Force, Centre of Meteorological Experimentations, Vigna di Valle (Rome) Italy, 12) DICAT - Department of Civil, Environmental and Territorial Engineering, University of Genoa , GENOVA Italy , 13) Finnish Meteorological Institute, Arctic Research Centre, Sodankyla , (14) State Hydrological institute,St.Petersburg, Russian Federation, (15) World meteorological Organization, EC-PORS, GCOS, Geneva Switzerland

How well are we measuring snow?

National Center for Atmospheric Research

Updraft generated upstream of gauge

Challenge to Measuring Snowfall

Theriault et al. 2011

Data from single alter GEONOR gauge at Marshall (box plots)

Model results (lines) from Fluent simulation of flow past single Alter GEONOR with snowflake trajectory modeling

Sing

le A

lter G

EON

OR

Due to updraft, snowgauges significantly undercatch

National Center for Atmospheric Research

Capping of gauge

Challenges to Measuring Snowfall

Key goal of Pre-SPICE: Establish Field Reference Systems for SPICE

• Need to establish a recognized field reference using automatic gauges to calculate the undercatch as a function of wind speed (transfer function).

– Proposed configuration: DFIR shield surrounding a Weighing Gauge (WG)

– Develop transfer functions to characterize the proposed reference against the WMO Secondary Reference (Tretyakov gauge inside DFIR);

• Options for the configuration of a Filed Reference using WG:– Type of WG: proposed Geonor T-200, OTT Pluvio 2;

– Configuration of WG: ▪ heated/non-heated; ▪ wind shield:

– DFIR,

– Double Alter, Belfort Double Alter.

Instruments and Site Focus for Pre-SPICE

– A WMO secondary field reference, using a manual Tretyakov gauge installed in a DFIR, was used in Canada and Finland.

– A DFIR shield surrounding an automatic precipitation weighing gauge was configured and assessed as a field working reference in Canada (CARE and Bratt’s Lake), Finland (Jokioinen), Norway (Haukeliseter), and USA (Boulder),(DFAR)

– In Switzerland, the focus of the pre-SPICE experiment was the assessment of the heating of a weighing gauge, in alpine conditions, in the presence of large amounts of snowfall.

– A laboratory calibration of the instruments considered for use as part of the working field reference was performed at the Precipitation Intensity Lead Centre in Genoa (Italy). This focused on the testing of the weighing gauges at temperatures representative of the winter operating conditions.

Week long meeting was held the week of June 11th in Boulder, Colorado to review the results of the Pre-SPICE testing

Current reference for snowfall observations are manual

Primary Reference (Valdai, Russia)Only one!

Bush Gauge

DRAFT – Page 11 – April 18, 2023

Secondary Reference: DFIR surrounding a Tretyakov precipitation gauge

• WMO Solid Precipitation Measurement Inter-comparison (WMO CIMO IOM Report No. 67, WMO/TD-No. 872, 1998 http://www.wmo.int/pages/prog/www/IMOP/publications/IOM-67-solid-precip/WMOtd872.pdf)

– Recommended : “The Double Fence Intercomparison Reference (DFIR) should be accepted as a secondary reference for the (manual) measurement of solid precipitation;” (section 6.1.2)

– (DFIR): “The octagonal vertical double-fence inscribed into circles 12 m and 4 m in diameter, with the outer fence 3.5 m high and the inner fence 3.0 m high surrounding a Tretyakov precipitation gauge mounted at a height of 3.0 m.”( section 2.2.2)

Double Fence Intercomparison Reference

Cross section of

DFIR shield

Federal Department of Home Affairs FDHAFederal Office of Meteorology and Climatology MeteoSwiss

Pre-SPICEWinter 2011-2012

11.6.2012

Set-up and some results from Weissfluhjoch/Davos

Testing at Davos, Switzerland by MeteoSwiss

- Impact of heating on OTT Pluvio2 200 cm2 gauge with Tretyakov shield

15 Title of presentation | SubtitleAuthor

21.02.2012

16 Title of presentation | SubtitleAuthor

Schematic of ice bridging inside the OTT PLUVIO2

Summary of Testing at Switzerland Impact of heating unshielded OTT Pluvio2 200 cm2 gauge

1. For prevailing alpine conditions, measurement is difficult with an unheated gauge: snow can induce mechanical effects on the sensor, with possible formation of ice or snow bridges between the housing and the weighing elements.

2. Heating of the ring is mandatory to ensure good quality measurements in Alpine winter conditions with high snow amount.

3. No under-catch due to the heating.

18/04/23Finnish Meteorological Institute 18

Jokioinen: Pre-SPICE field

60° 48' 50.44" N, 23° 29' 51.40” E, 104 m, from the sea level

Measurements 19.02.2012 – 30.04.2012

Manual measurements only once every day at 0600 UTC

Compared manual measurement in DFIR with Tretyakov shield and can with automated measurement in DFIR with OTT Pluvio2 gauge

18/04/23Finnish Meteorological Institute 19

Rain

Both gauges in DFIR

18/04/23Finnish Meteorological Institute 20

Snow

Both gauges in DFIR

18/04/23Finnish Meteorological Institute 21

Results from testing in Finland:

The daily precipitation amount from the automated gauge in the DFIR compared well with the manual measurement from the Tretyakov can also in a DFIR.

Suggests that can use an automated gauge in a DFIR as a reference for SPICE (DFAR).

Summary of results from the Canadian contribution to Pre-SPICE

Rodica Nitu, Paul Joe, Daqing Yang, Craig Smith, Michael Earle, Jeff Hoover, Jim Waller, Faisal Boudala

Pre-SPICE Workshop

Boulder, Colorado

June 11, 2012

Toward the definition of a SPICE field reference

Page 23 – April 18, 2023

Measurements from two field sites Centre for Atmospheric Research

Experiments (CARE) Egbert, Ontario

CARE

Bratt’s Lake

Bratt’s Lake (BL) Bratt’s Lake, Saskatchewan

Canada

Bratt’s

LakeCARE

Instruments at the Canadian CARE site

Tretyakov manual gauge in DFIR

Geonor T-200 heated (DFIR)

Pluvio 2 (Belfort Double Alter)

Geonor T-200 in BDA

Summary of Catch Efficiency vs. Wind SpeedGeonor T-200B w/ wind shields

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0

Wind Speed (m/s)

Ca

tch

Eff

icie

nc

y

DF SA DA Yang et al (1993)

The Bratt’s Lake Precipitation Intercomparison Facility

Heated Geonor gauge (CRN heating)

Unheated Geonor gauge

Bratt’s Lake, Saskatchewan:Under test:

Unheated Geonor in a DFIRHeated Geonor (using the CRN heating algorithm), in a DFIR

Page 26 – April 18, 2023

Rim heating has a positive impact on the gauge performance (accuracy, improved catch), both GEONOR T-200 or OTT PLUVIO2.

Both GEONOR T-200 and OTT PLUVIO2 performed well in terms of accuracy

Either GEONOR T-200 or OTT PLUVIO2 acceptable at weighing gauge for Field Reference

Summary of Canadian Pre-SPICE testing

DRAFT – Page 27 – April 18, 2023

Marshall (Boulder, CO USA) site with DFIR and Alter shielded snow guages

Summary of Pre-SPICE Results from Marshall Field Site, USA

1. Gauge performance in Small DFIR and standard DFIR similar in terms of accuracy.

2. Provided estimate of the performance of various wind shield types.

3. Noted the importance of heating the entire collection tube of the GEONOR T-200 gauge.

4. Noted that the current OTT PLUVIO2 heating algorithm may not be sufficient for heavy, wet snow conditions (dumps occurred in this situation).

Test site Haukeliseter, NorwayPre-SPICE Data

Mareile Wolff, Ketil Isaksen, Ragnar BrækkanNorwegian Meteorological Institute, Oslo, Norway

Norwegian Meteorological Institute met.no

Haukeliseter

59°48.71’N, 7°12.86’E, 991m

Norwegian Meteorological Institute met.no

Summary

Identified the need for improved identification of the onset and offset of weak precipitiation events- Suggested use of a precipitation detector, yes/no sensor, video camera

Blowing snow needs to be taken into account in open, high alpine sites

WMO-CIMO LEAD CENTRE“BENEDETTO CASTELLI”

ON PRECIPITATION INTENSITYITALY

Laboratory tests of SPICE reference instruments

2nd WMO SPICE, Boulder ,CO, USA, 11-15 June 2012 32

Experiment setup Temperature tests

33

Set-up for Geonor

Set-up for OTT

Gauges in the cold chamber

Conclusions 3/3

34

The dynamic tests show that both gauges are able to reproduce likely real world events with comparable performance;The results from laboratory tests open the way for possible improvements of their accuracy and precision (including low intensities, the interest for SPICE)The Lead Centre is currently conducting additional tests.

Matteo Colli from the U. of Genoa is currently visiting NCAR and testing the GEONOR T-200 gauge with the NCAR snow machine for heater performance for various snowfall rate and temperature conditions (snow capping elimination).

Deutscher WetterdienstTI 23 - Sensorik

Reference Systems for SPICE

- LWE Precipitation Amount

R1: DFIR + Tretyakov gauge (manual measurements) + Tretyakov shield designated in the 1989-1993 intercomparison as secondary field reference WMO/TD-872/1998);

R2: DFIR + automatic weighing gauge (AWG) + shield

Shield will be an Alter shield Either GEONOR T-200 or OTT

PLUVIO2 acceptable as the weighing gauge

Both gauges will be heated with the CRN heating algorithm (heat between +2 and -5 C, every 24 hours otherwise)

A capacitive precipitation detector will be used to detect the presence of precipitation

Working Field Reference for Precipitation Amount

As agreed during the Boulder Meeting June 2012

R3: An automatic weighing gauge in a (small) windshield paired with an unshielded gauge

- The Working Field Reference System type R3 consists of a pair of identical automatic weighing gauges heated in the same manner, one being unshielded and the second installed with a single Alter Shield. The configuration of the Alter shield is specified by the SPICE IOC. Gauge type: GEONOR T-200 or OTT PLUVIO2

- A capacitive precipitation detector will

be used to detect the presence of precipitation.

Working Field Reference for Precipitation Amount

As agreed during the Boulder Meeting June 2012

+A +

How well are we measuring snow? Hopefully, after SPICE

a lot better!

Thank You!

http://www.wmo.int/pages/prog/www/IMOP/reports/2011/Joint_ET-II_IOC-SPICE.pdf

rasmus@ucar.edu