24/02/2014. Where do forecasts come from? Presentation of teacher. Lesson outline. Dr. Kristine Madsen Danish Meteorological Institute

Transcription

1 Where do forecasts come from? Boundary: tides surge T & S Atmosphere: wind pressure temperature Observations: tide gauge (satellites) Storm surge x model Forecaster Authorities Media General public Dr. Kristine Madsen Danish Meteorological Institute Presentation of teacher Kristine S. Madsen kma@dmi.dk PhD in oceanography Scientist at Center for Ocean and Ice, Danish Meteorological Institute Main working areas Ocean modeling, including sea level forecasting Coastal altimetry Future sea level rise Lesson outline Here, I m going to talk about: 1. Where does the input data come from? 2. Who does the modeling? 3. How does the forecasting expert judge & decide? 4. How does the forecaster communicate? 5. What affects the efficacy of the communications uptake? 1

2 Lesson goals Lessons goals: Give an overview of the general principals of storm surge forecasting. Inform on how DMI handles the information flow through the storm surge forecasting chain, from raw data, through models, through appraisal by the forecaster, through to advisories and communications to the public. Add a global perspective. The forecasting chain Input data Boundary: tides surge T & S Atmosphere: wind pressure temperature Observations: tide gauge (satellites) The forecasting chain Input data Storm surge model Boundary: tides surge T & S Atmosphere: wind pressure temperature Observations: tide gauge (satellites) Storm surge model 2

3 The forecasting chain Input data Storm surge model Appraisal by the forecaster Storm surge x model Forecaster Authorities Media General public The forecasting chain Input data Storm surge model Appraisal by the forecaster Advisories and communications to the public Authorities Storm surge x model Forecaster Media General public Input data at DMI Meteorological forcing ECMWF DMI model 3

4 Input data at DMI Meteorological forcing ECMWF DMI model Boundary conditions Tides External surges Other data Temperature and salinity River discharge 2D model: external surges 3D main model Input data at DMI Meteorological forcing ECMWF DMI model Boundary conditions Tides External surges Other data Observations In situ sea level BOOS NOOS Input data at DMI Meteorological forcing ECMWF DMI model Boundary conditions Tides External surges Other data Observations In situ sea level BOOS Danish stations DMI level/ 4

5 Input data at DMI Meteorological forcing ECMWF DMI model Boundary conditions Tides External surges Other data Observations In situ sea level Data for assimilation Input data international sources Meteorological forcing ECMWF widely used in Europe Input data international sources Meteorological forcing ECMWF widely used in Europe NCEP Global Forecast System free nomads.ncep.noaa.gov 5

6 Input data international sources Boundary conditions Tides Several global solutions DTU10 (Ole B. Andersen, DTU, Denmark) Scientific_data_and_models/Global_Ocean_ Tide_Model Input data international sources Observations Tide gauge data: GLOSS fast database, University of Hawaii Sea Level Center Input data international sources 6

7 Input data international sources Input data Sources used by participants What is your experience with Meteorological forcing? Boundary conditions? Use of observations? The DMI storm surge model introduction and domain HBM model Developed by BSH (Germany) and DMI (Denmark), used in MyOcean for the Baltic Sea 3 2 way nested areas + eksternal surge model of the north east Atlantic 52 vertical layers 3 nm North Sea Baltic Sea 1 nm Wadden Sea ½ nm transition area 7

8 The DMI storm surge model introduction and domain HBM model Developed by BSH (Germany) and DMI (Denmark), used in MyOcean for the Baltic Sea 3 2 way nested areas + eksternal surge model of the north east Atlantic 52 vertical layers Extra fjord model: 400 m resolution, 9 vertical layers What do we want to forecast? Our task is to forecast: Hmax tmax t1 t2 maximum sea level time of max sea level when critical level is passed when we go back under critical level Sea level t max What do we want to forecast? Our task is to forecast: Hmax tmax t1 t2 maximum sea level time of max sea level when critical level is passed when we go back under critical level Peak error Sea level Forecast 8

9 The DMI storm surge model development cycle Model development User feedback Model testing Operationalization The DMI storm surge model development cycle Model development Example: the Sound High sea level November 2011 First peak missed Second peak well predicted User feedback Operationalization Model testing Sea level, Copenhagen [cm] Observed Modelled The DMI storm surge model development cycle Model development Example: the Sound High sea level November 2011 First peak missed Second peak well predicted Observed sea level gradient of 2.5 m not quite reproduced by model Development: Bathymetry Bottom friction User feedback Model testing Operationalization Bathymetry [m] 9

10 The DMI storm surge model development cycle Model development Example: the Sound High sea level November 2011 First peak missed Second peak well predicted Observed sea level gradient of 2.5 m not quite reproduced by model Development: Bathymetry Bottom friction Test / validation: Corrects local error Does not make the model worse in other places or situations User feedback Operationalization Model testing Sea level, Copenhagen Observed Old model version New model version Participants experiences What is your experience with Choice of ocean models? Model development and test? Operational model execution and surveillance Non operational expert staff develop and test forecast system, and prepare for operationalization incl. manual. IT staff (24 7) secures execution and handle breakdowns according to manual. IT experts (on call) handle nonstandard IT issues. Operational weather service (24 7) analyzes output, issues warnings and may perform search & rescue and oil spill simulations. 10

11 Regional storm surge model ensembles In the Baltic Sea the different national authorities work together to share and compare forecasts. This provides an uncertainty estimate that combines the error sources of weather forecasts and models. Hornbæk Storm surge model ensemble based on weather forecast ensemble The British and Dutch national authorities work with ensemble forecasting by running their ocean model with members of a weather forecast ensemble. This provide a detailed estimate of the weather forecast error effect. Adjustment of forecast to fit observations Before the DMI sea level forecast for individual harbors is send out, an autoregressive filter is used to adjust the forecast to observations. This is done every 10 minutes, using real time observations. Uses most recent observations Observations should never be more than 1 hour old Requires real time quality check of observations Easier and less computer demanding than data assimilation Only works at locations where observations are available Observed sea level Forecasted sea level Most recent observation New forecast Time 11

12 Presentation to the forecaster Criteria for warnings General values of critical water level heights are set for the Danish West coast and the Inner Danish Waters. Local values may also apply. Warnings are sent out 24 hours in advance. Emergency management 2 approaches: Denmark: Sector responsibility, same authority takes care of everyday services and emergency situations. DMI have the responsibility of sea level forecasting and communication in all cases. The Netherlands: 12

13 Participants experiences What is your experience with Operational model execution? Ensemble forecasting and cooperation with neighbouring countries? Presentation to the forecaster and criteria for warning? Communication to authorities and media State, regional and local authorities are informed by fax and phone 24 hour or 18 hour pre warning From 7 hours before exceeding critical level, hourly forecasts are sent out Media is informed by phone and press releases Communication to the general public General ocean forecast Continuous sea level information Forecast fitted to observations 13

14 Communication to the general public General ocean forecast Continuous sea level information Forecast fitted to observations Information in warning situations Communication uptake the Bodil storm(surge) The Bodil storm hit Denmark on December 5, 2013 A storm surge hit the Danish North Sea Coast at the same time as the storm A second storm surge hit the inner Danish waters 1 day later This storm surge also hit in fjord areas without a validated model, and certainly not for that storm surge height Communication uptake the Bodil storm(surge) Udsendt d. 5. december :29 lokal dansk tid DMI Varsel om forhøjet vandstand i indre farvande og/eller ved Østersøen Fredag morgen ventes vandstanden ved kysterne fra sydlige Kattegat og ned til den nordlige del af Fyn, samt den nordlige del af Øresund at stige til typisk 1,20 til 1,50 m over DVR90. Senere på fredagen kan vandstanden i de nordvendte fjorde, Odense fjord, Isefjorden og Roskilde fjord nå op mellem 1,40 og 1,80 m over DVR90. Udsendt d. 6. december :20 lokal dansk tid DMI Varsel om forhøjet vandstand i indre farvande og/eller ved Østersøen Ved kysterne fra sydlige Kattegat og ned til den nordlige del af Fyn, samt Øresund fra København og nordover vil vandstanden ligge mellem 1,3 m og 1, 8 m frem til sidst på natten. I Isefjorden og Roskilde fjord vil vandstanden i aften være mellem 1,80 og 2,0 m, men ventes at falde i løbet af natten. 14

15 Communication uptake authorities Old routines improved forecast ability The harbour in Hornbæk on Friday December in the afternoon Photo: Keld Navntoft, brought by Berlingske Communication uptake media So much focus on the storm that we tend to forget to communicate the surge (at least until after the storm has peaked) Media get tired of hearing about the event Communication uptake general public It is easy to reach the group of people that know they are at risk. The challenge is the group that are not used to be affected by sea level variations. It is important to: reach this group quickly and efficiently Make them aware that they or/and their property are at risk Make them react in time, remembering that the reaction may take some time Here social media such as Twitter are becoming increasingly important 15

16 Participants experiences What is your experience with Communication to authorities, media and the general public? Communication uptake and use of social media? Summary High quality forecast needs detailed, high quality input Model development requires oceanographers with local knowledge and resources to learn from past events Operational forecasting benefit greatly from 24 7 staff, but may be combined with e.g. weather service Communication should be directed at several different audiences 16