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World Meteorological Organization Symposium on Nowcasting - WMO

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80<br />

4.5<br />

6.8 Towards the Blending of NWP with Nowcast - Operati<strong>on</strong> Experience in B08FDP<br />

A Comparis<strong>on</strong> of Visibility Measurements obtained during FRAM-S project during<br />

freezing fog and warm fog events<br />

I.Gultepe[1], R. Rasmussen[2], L. Malenfant[3], R. K. Ungar[4], S. Cober[1], and R.<br />

Nitu[5][1]Cloud Physics and Severe Weather Research Secti<strong>on</strong>, Science and Tech Branch,<br />

Envir<strong>on</strong>ment Canada, Tor<strong>on</strong>to, Ontario, M3H5T4[2]Nati<strong>on</strong>al Center for Atmospheric<br />

Research, PO Box 3000, Boulder, CO 80307[3]ATS Services Ltd., ATS Technology Systems<br />

Inc., 183 Briancrest Road, Halifax, NS B2T 1Z9[4]Verificati<strong>on</strong> and Incident M<strong>on</strong>itoring<br />

Radiati<strong>on</strong> Protecti<strong>on</strong> Bureau, 775 Brookfield Road, AL6302D1, Ottawa, Ontario K1A<br />

1C1[5]Atmospheric M<strong>on</strong>itoring and Water Survey Directorate, Envir<strong>on</strong>ment Canada, Tor<strong>on</strong>to,<br />

Ont. M3H5T4<br />

[1]Cloud Physics and Severe Weather Research Secti<strong>on</strong>, Science and Tech Branch,<br />

Envir<strong>on</strong>ment Canada, Tor<strong>on</strong>to, Ontario, M3H5T4[2]Nati<strong>on</strong>al Center for Atmospheric<br />

Research, PO Box 3000, Boulder, CO 80307[3]ATS Services Ltd., ATS Technology Systems<br />

Inc., 183 Briancrest Road, Halifax, NS B2T 1Z9[4]Verificati<strong>on</strong> and Incident M<strong>on</strong>itoring<br />

Radiati<strong>on</strong> Protecti<strong>on</strong> Bureau, 775 Brookfield Road, AL6302D1, Ottawa, Ontario K1A<br />

1C1[5]Atmospheric M<strong>on</strong>itoring and Water Survey Directorate, Envir<strong>on</strong>ment Canada, Tor<strong>on</strong>to,<br />

Ont. M3H5T4<br />

The purpose of this work is to compare the visibilities (Vis) obtained from the five sensors to<br />

human-based observati<strong>on</strong>s of Vis values to better understand issues related to low visibility<br />

c<strong>on</strong>diti<strong>on</strong>s. The ground-based observati<strong>on</strong>s from the Fog Remote Sensing and Modeling<br />

Project in St. John’s (FRAM-S), which took place during April of 2009, were being used for<br />

comparis<strong>on</strong>s. The instruments used to measure Vis were 1) the Biral HSS VPF-730<br />

Combined Visibility & Present Weather Sensor, 2) Sentry VIS sensor, 3) Vaisala FD12P<br />

present weather sensor, 4) Vaisala PWD12 sensor (two of them), and 5) Belfort Vis sensor.<br />

Human-based Vis observati<strong>on</strong>s were also available during the project. In the analysis, the<br />

measurements of Vis were compared to human-based Vis observati<strong>on</strong>s and to each other. In<br />

additi<strong>on</strong>, validati<strong>on</strong>s were performed estimating Vis from the particle measurements of a)<br />

MetOne aerosol sensor (for small wetted aerosols and droplets; 0.3-10 micr<strong>on</strong>), b) DMT Fog<br />

Measuring Device (FMD; 2-50 micr<strong>on</strong>), and 3) DMT Ground Cloud Imaging Probe (GCIP; 7.5-<br />

900 micr<strong>on</strong>). Results representing various freezing fog, drizzle, and snow c<strong>on</strong>diti<strong>on</strong>s will be<br />

presented in the talk and probability curves developed earlier based <strong>on</strong> <strong>on</strong>ly FD12P<br />

measurements will be discussed. Possible applicati<strong>on</strong>s of the results will be offered for<br />

nowcasting issues.<br />

Wai-kin W<strong>on</strong>g [1], Linus H.Y. Yeung [1]; Ying-chun Wang [2], Min Chen [2]<br />

[1] H<strong>on</strong>g K<strong>on</strong>g Observatory, H<strong>on</strong>g K<strong>on</strong>g, China; [2] Institute of Urban Meteorology, Beijing,<br />

China<br />

One of the major advancements achieved in the Beijing 2008 Forecast Dem<strong>on</strong>strati<strong>on</strong> Project<br />

(B08FDP), under the <str<strong>on</strong>g>World</str<strong>on</strong>g> Weather Research Programme of the <str<strong>on</strong>g>World</str<strong>on</strong>g> <str<strong>on</strong>g>Meteorological</str<strong>on</strong>g><br />

<str<strong>on</strong>g>Organizati<strong>on</strong></str<strong>on</strong>g>, was the incorporati<strong>on</strong> of numerical weather predicti<strong>on</strong> (NWP) model outputs in<br />

an attempt to extend the nowcast of precipitati<strong>on</strong> and c<strong>on</strong>vective storm development bey<strong>on</strong>d<br />

the radar extrapolati<strong>on</strong> technique. In several participating nowcasting systems in B08FDP,<br />

storm-scale NWP models with horiz<strong>on</strong>tal resoluti<strong>on</strong> at several kilometres were operated <strong>on</strong> a<br />

real-time basis to simulate the evoluti<strong>on</strong> of severe weather systems. Various types of<br />

observati<strong>on</strong>s from the automatic weather stati<strong>on</strong>s, wind profilers, Global Positi<strong>on</strong>ing System<br />

(GPS), radars and satellites were assimilated in the models in order to better describe the<br />

initial c<strong>on</strong>diti<strong>on</strong>s and produce more skilful numerical guidance for blending computati<strong>on</strong>. The<br />

analyses and short-term forecasts from the NWP models also provided valuable reference to<br />

forecasters for their subjective assessment of the potential of c<strong>on</strong>vective storm development<br />

and related decisi<strong>on</strong> making.In this paper, the impact of NWP models in blending with radar<br />

nowcast techniques <strong>on</strong> aspects like quantitative precipitati<strong>on</strong> forecasts (QPF), c<strong>on</strong>vective<br />

storm development and storm tracking will be discussed. In particular, the phase correcti<strong>on</strong><br />

technique adopted in the H<strong>on</strong>g K<strong>on</strong>g Observatory nowcasting system to correct the locati<strong>on</strong><br />

of model QPF, the methodology to adjust the model rainfall intensity and the blending<br />

algorithm to seamlessly merge the radar-based QPF with that from NWP models will be<br />

illustrated by cases. By applying the time-lagged ensemble approach to the rapidly updated<br />

NWP model forecasts and blending computati<strong>on</strong>, probabilistic precipitati<strong>on</strong> nowcast products<br />

were also developed, the performance and potential benefits of which in nowcast applicati<strong>on</strong>s<br />

will be discussed. On the other hand, the Beijing rapid update cycle system (BJ-RUC) based<br />

<strong>on</strong> the Weather Research and Forecasting (WRF) model was developed with the primary<br />

goal to improve the very short range forecasts (3-12h) and to support nowcast operati<strong>on</strong>.<br />

The applicati<strong>on</strong> of analyses and forecasts from BJ-RUC including the model output<br />

soundings, stability indices and wind shear to predict the evoluti<strong>on</strong> of near storm envir<strong>on</strong>ment<br />

will be presented. The experience gained during B08FDP operati<strong>on</strong> will be summarized, and<br />

suggesti<strong>on</strong>s and views <strong>on</strong> the future development and applicati<strong>on</strong> of the NWP products and<br />

blending techniques in nowcasting will be presented.<br />

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