Use cases selected for the 1st WMS Interoperability Experiments for Best Practices (Time issue)

Introduction

These use cases have been selected out of the tank of use cases because they fit the first issue that have been discussed during the WMS teleconferences about the multidimensional time which is specific to Met Ocean data.

Two main families of use cases can be distinguish :

• One for Met Ocean Professional users ( and Met Ocean professional WMS clients), framed by the Stephan 1 general use case
• one for end users (and all WMS clients), framed by the Stephan 2 general use case

The Stephan1 general use case have been detailed into two real scenarii from on duty forecasters : Jeff1 and Cecile1 The Stephan 2 general use case still has to be detailed into a real story or the data has to be made available on WMS servers for uses we don't know completely as providers.

Use Cases:

1st Family for Met Ocean professional users : Stephan 1 : Analysis of a weather feature

A forecaster at a NWS and a analyst at ECMWF are observing and analysing a weather feature and trying to predict its future developments. They want to compare its development between different model runs and look at ensemble outputs. The aim is to see how forecasters can easily use maps of other NWP forecasts to improve their ability to access a meteorological situation.

Ideally I would add that the ECMWF and NWS analysts should be easily be able to exchange the maps they are looking at!

What this use case tests:

• this would test time dimensions
• security (hopefully) is here a limited factor since we have "trusted" channels?
• EGOWS community could pick this up since the clients are forecaster workstations
• this use case can be later extended to let forecaster workstation requesting related data through WCS and exchange meteorological objects (in GML/CSML) between workstations ...

Challenges for the IE:

• How to define "different model runs"
• How to generate "ensemble outputs"
• How to serve the models via WMS

Jeff 1 : Building an ANASYG/PRESYG Product.

• Step : definition of the level of confidence into the model via comparison of the Mean Sea Level Pressure on several models

At 9:00 UTC and 18:UTC, Jeff wants to build an ANASYG/PRESYG for a 24 hour forecast. He visualizes the Mean Sea Level Pressure (field only available a surface level) over the north atlantic area but today, the French model he uses regularly seems doubtful to him : He identifies some "anomalies" that can be due to an exageration from the model in certain meteorological situations. But they can be real anomalies (anomalies are non common values but can be reality to distinguish from exagerations or errors of the models which are just artifacts of the numerical outputs and not reality).

So he wants to access and visualize the behaviour of all other available modeles over the same area for the same validity date. The Run can be different but not older than 12 hours.

Note: an expanded version of this with image explanations can be found here. WARNING: the file images are large.

Note: a simplified, reworded take on the use case, with smaller images can be found here.

What this use case tests:

• this would test time dimensions
• EGOWS community could pick this up since the clients are forecaster workstations and the need is a basic need for all NWS
• this use case can be later extended to let forecaster workstation requesting related data through WCS and exchange meteorological objects (in GML/CSML) between workstations ...

Challenges for the IE:

• How to represent Mean Sea Level Pressure (SLD does not do isolines, so would need to be extended, but that work is ongoing)
• How to browse the time dimensions
• How to request "Mean sea level pressure"

Cecile 1 : Checking the good calibration of the model (= good localisation of the significant meteorological patterns).

• Step 1: Check of modele calibration at surface level via the comparison of the pressure available via the observations and the analysis of Mean Sea Level Pressure provided by the numerical model (RUN_START_TIME = TIME, FORECAST_OFFSET= 0H)

It is 14 UTC. Cecile visualizes the observations at 12UTC because she has a run available at 12 UTC (i.e. she visualises observations at the RUN_START_TIME of the model she wants to calibrate) and overlays the Mean Sea level Pressure from the model she wants to calibrate. She can also overlay other models available at same TIME (validity date) but which RUN_START_TIME is not older than 12hours (same use case as Jeff1)

• Step 2: Check of modele calibration at surface level via the comparison of the precipitations available via the water wave and accumulated precipitations available at the first time step of the model

It is 14 UTC. Cecile wants to calibrate a modele which step is 1 hour and which last run available is at 12 UTC. She visualizes the water waves over 1 hour at 13UTC (i.e. she visualises water wave at the TIME = RUN_START_TIME+first FORECAST_OFFSET) and visualizes into another window the Total precipitations from the model she wants to calibrate. Remark : The Total precipitations field is not available at FORECAST_OFFSET= 0H so it has to be made at the first FORECAST_OFFSET(here = 1H). If the step of the model is > 1hour, all combination has to be made on the same duration (i.e. if step = 3hours, water wave has to be over 3hours)

• Step 3: Check of modele calibration in altitude via the comparison of the watervapor satellite image and the alitude of the 2PVU from the numerical model

Cecile visualizes the Water vapor from Meteosat at 12 UTC. She overlays the field of geopotential on the 2.0 level expressed in PVU (Potential Vorticity Unit) at 12 UTC. She then checks if the dark areas of the image fit to the area of strong gradient.

• Step 4: Check of modele calibration in altitude via the comparison of the infrared satellite image and the Humidity field at 850 hPa from the numerical model

Cecile visualizes the infrared from Meteosat at 12 UTC. She overlays the field of Humidity at 850 hPa at 12 UTC. She then checks if the white areas of the image fit to the area where the humidity is over 90% (thicker isoline from the Humidity field)

What this use case tests: Step 1 same as Jeff1 Step2

• this would test accumulations over time
• this use case can be later extended to let forecaster workstation requesting related data through WCS and exchange meteorological objects (in GML/CSML) between workstations ...

Challenges for the IE: Step 1 same as Jeff1 Step2

• How to define an accumulation duration
• How to combine observations and forecast

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2nd Family for end users : Stephan 2 : Obtaining forecasts

Several government agencies are observing a disaster zone (like Haiti). They have to plan relief from air, sea and by road. They have maps of roads, storage facilities, hospitals, etc and would like to overlay these with forecasts to make decisions to co-ordinate the relief (like the average/accumulated rainfall). The aim is to see how well NWS can provide forecasts reliable&fast to be used in standard OGC clients.

What this use case tests:

• Only our servers are really tested here
• security a big issue
• meteorological specific clients would only be consider if very thin - more likely they would be standard OGC clients (such as ESRI)
• This use case can be used to make a business case of using OGC standards ...

Challenges for the IE:

• How to define different "forecasts"

-- MarieFrancoiseVoidrotMartinez - 08 Apr 2010