how to tackle wet deposition of radionuclides?€¦ · in ims rn threshold monitoring applications....

CTBT Science & Technology Conf., Vienna, 8-10 June 2011 Becker, Ross and Ceranna: How to tackle wet RN deposition? Slide 1 of 20

1Deutscher Wetterdienst, Frankfurter Straße 135, 63067 Offenbach, Germany [email protected], [email protected]

How to tackle wet deposition of radionuclides? A proposal by the Global Precipitation Data Centre at Deutscher Wetterdienst and by the NDC Germany

Andreas Becker1

Ole Ross2

Lars Ceranna2

1Head Global Precipitation Climatology Centre at DWD, Germany2BGR / B4.3 Hannover, Germany (NDC Germany)

2Bundesanstalt für Geowissenschaften und Rohstoffe, Stilleweg 2, 30655 Hannover [email protected], [email protected]

mailto:[email protected]





Outline

1

3

2An easy approach to wet deposition recognitionin IMS RN threshold monitoring applications

Motivation

The Global Precipitation Data Centre (GPCC) and other suppliers of public available products

4 Summary and Pointer to GPCC Products


Enhance PTS capabilities in RN Threshold Monitoringand Source Attribution by appropriate recognition of the

wet deposition impact

In the past decade PTS has built up unprecedented capabilitiesin RN monitoring and source location of RN events

• Built up of the IMS RN networks with unprecedented detection limits for particulate radio-nuclides and radio-xenon

• Remarkable source location capabilities based on ATM and the data fusion technique proven during CTBTO-WMO exercises, NDC preparedness exercises (NPEs) and DPRK I and II

Motivation


Enhance PTS capabilities in RN Threshold Monitoringand Source Attribution by appropriate recognition of the

wet deposition impact

However, …. (!!)

• The integrated re-analysis of multiple nuclide detection scenarios is hampered by the non-recognition of the particulates’ wet-deposition in current PTS methods applied for atmospheric backtracking

• Nuclide specific IMS RN threshold monitoring is currently not faithful for particulate nuclides being susceptible to wet deposition.

• In consequence current PTS threshold monitoring products tend to overestimate actual monitoring caps.

Motivation


Outline

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3

1

An easy approach to wet deposition recognitionin IMS RN threshold monitoring applications

Motivation




The Global Precipitation Climatology Centre (GPCC)

Established by the World Meteorological Organization WMO in the year 1989

• undertaken by Deutscher Wetterdienst DWD

• contributes to the Global Climate Observing System GCOS• and the World Climate Research Programme WCRP• thousands of users world-wide• scientific task: quantitative assessment of global precipitation

and investigation of the global water cycle• new function proposed: high-quality data source to parametrize the

wet deposition factor

GPCC Facts


The functions of the GPCC

collection of observed (gauges) precipitation data world-wide

data processing, quality control, storage

data analysis, production of gridded data fields

distribution of the gridded data fields

contribution to international programs

GPCC Facts


5 days First Guess Anomalies drought monitoring FAO ~ 6,500

2 months Monitoring Product WCRP/GEWEX early reference ~ 8,000

GPCC near real-time monthly productsRoutinely produced gridded data setsavailable within: application: number of stations:

GPCC Products

Additional information provided for monitoring product• Number of stations per grid box • Sampling error• Stochastic error• Systematic error assessment

Monitoring product also feeds global GPCP product that combines rain gauge and satellite data


Precipitation [mm/month] in May 2011

GPCC First Guess(public available!)


GPCC Monitoring-> GPCP Product example(public available!)Precipitation during La Niña year ending June 2000


Recognition of wet deposition for reanalysis of RN detection events would require precipitation products at time scales shorter than a month!

GPCC has commenced generation of real-time daily precipitation analysis products

GPCC First Guess Daily


Outline

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Motivation




Take advantage of striking similarities in ATM constrainedthreshold monitoring and precipitation monitoring products

Proposed Approach

Figure 1: Xe-133 threshold monitoring in the IMS Xenon network for summer year 2008/2009. GPCP monitoring product for the same period. Areas of apparently high pattern correlation are indicated by circles. Monthly precipitation totals (right plot) expose also the Indian monsoon area.

RN Threshold Monitoring Product purelycontrained by ATM and detection limits

Global Precipitation Climatology ProjectMonitoring Product (public available!)

• The IMS radionuclide (RN) monitoring capability is reduced in areas of systematically reduced surface level horizontal transport that is – due to the conservation of mass accompanied by regions of ascending air.

• The uplifting of air gives rise to condensation and formation of precipitation. It is thus straightforward to use precipitation patterns derived from public available re-analysis data sets as proxies to describe areas of limited detection capabilities.

[mm/month]


Proposed Approach

1. Apply a wet deposition related reduction factor during read in of the ATM based SRS fields disseminated by the PTS

2. Parameterize this factor from available gridded precipitation monitoring products!

• Extension of the source-receptor relationship by the W term representing the wet deposition factor that can be parameterized from precipitation monitoring products

• In this approach wet deposition is only recognized at the source location thus treated in similarity to a containment factor for underground explosions

• Application of this wet deposition factor alleviates clearance of several apparently CTBT relevant detections as bogus. These were encountered in the past and in the wake of the Fukushima nuclear power plant accident

ijnkijnk SWMc )( ⋅•=


Wet Deposition

How to find the right W? Parameterization of wet deposition is challenging.

Two basic types:1. Below-cloud scavenging, washout by rain droplet impact2. In-cloud scavenging, related to nucleation process Dependencies on:• Particle size• Precipitation rate• Humidity• Cloud liquid water content, droplet size distribution• Height of scavenging columnFirst order approach for below-cloud scavenging:

dc/dt (s-1)= A * RB with precipitation rate R (mm/h)

Empiric values for I-131 (Jylhä, 1991): A=(7 ± 5) x10-5 B= 0.69 ± 0.12


Impact on Detectability

First guess: Estimate possible impact of a heavy rain event over the source region with ~10% of monthly precipitation within 3 h

Example: Detection Threshold Monitoring for I-131 andmonthly GPCC 1° precipitation data for January 2009

Preliminary result:

difference betweendetection thresholdsfor I-131 in Jan 2009;with and w/o possiblewet deposition impact


Outline

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3

1


Motivation

The Global Precipitation Data Centre (GPCC) and other suppliers of public available products2

Summary and Pointer to GPCC Products


Summary I/II

• A gap analysis on PTS methods in atmospheric backtracking and ATM based threshold monitoring reveals the yet non existing recognition of wet deposition

• Non recognition of the wet-deposition impact hampers the integrated assessment of joint noble-gas and particulate detections and their reliable attribution to a joint source

• Limitation of the wet-deposition assessment to the possible source region allows for a treatment of the problem by a simple post-processing (parameterization) approach during read in of the PTS source-receptor sensitivity fields utilized for all atmospheric backtracking and RN threshold monitoring purposes.

• Public available gridded precipitation monitoring products are suitable to serve the data base for the parameterization of the wet deposition factor field


Summary II/II

• We propose here the utilization of the monthly/daily gridded precipitation monitoring products of the Global Precipitation Climatology Centre (GPCC) for the diagnosis of a monthly/daily global wet-deposition factor field across land-surfaces.

• A similar global product for the entire globe is available from the Global Precipitation Climatology Project (GPCP) monthly product

• GPCC products are public available, a comprehensive description of the GPCC is provided on http://gpcc.dwd.de. To visualize and download GPCC products consult ftp://ftp-anon.dwd.de/pub/data/gpcc/html/download_gate.html

• GPCC is ready to provide gridded precipitation data suitable for PTS needs to parameterize wet deposition if mandated by CTBTO through WMO

http://gpcc.dwd.de/

ftp://ftp-anon.dwd.de/pub/data/gpcc/html/download_gate.html


GPCC download Portal: ftp://ftp-anon.dwd.de/pub/data/gpcc/html/download_gate.html

Thank you!




how to tackle wet deposition of radionuclides?€¦ · in ims rn threshold monitoring applications....

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