node-red-contrib-dwd-local-weather

A node red node that returns German DWD MOSMIX current / forecasted weather for a given location.

It gives you the following data:

• Temperature in °C (in a 2 m height)
• Relative humidity in %
• Windspeed in m/s (in a 10 m height)
• Wind direction in degrees
• Rain probability in %
• Expected rain amount (precipitation) for the next 24 hours in kg/m²
• Timestamp of the forecast

Fig. 1: Node appearance

Remark: This node is mainly useful if you are interested in weather data for Germany. International weather data is available for only a couple of european locations (see MOSMIX stations below). Examples for international locations are Bergen, London, Dublin, Brussels, Luzern, Lille, Locarno, Le Mans, Madrid, Ibiza, Klagenfurt (and many others).

The weather data is provided by DWD (Deutscher Wetterdienst, Frankfurter Straße 135, 63067 Offenbach).

References:

• https://isabel.dwd.de/DE/leistungen/opendata/opendata.html
• https://www.dwd.de/DE/leistungen/met_verfahren_mosmix/met_verfahren_mosmix.html
• https://www.dwd.de/DE/leistungen/met_verfahren_mosmix/faq/faq_mosmix_node.html
• https://www.dwd.de/DE/leistungen/opendata/help/schluessel_datenformate/kml/mosmix_elemente_xls.html

Installation

In Node-RED (preferred)

• Via Manage Palette -> Search for "node-red-contrib-dwd-local-weather"

In a shell

• go to the Node-RED installation folder, e.g.: ~/.node-red
• run npm install node-red-contrib-dwd-local-weather

Usage

The easiest usage of the node is using internal triggering:

BasicUsageFlow.json

Fig. 2: Basic node usage

In this example the node cyclically reads out the DWD data and emits it as an output msg.

Node Configuration

Fig. 3: Node properties

Node configuration is quite simple. Only setting the property MOSMIX Station to select the required weather forecast location is mandatory.

MOSMIX station

Set this property to select the weather forecast location.
The format is a 5 character id. Allowed ids are given in the stations catalog (in CFG file format) of the DWD (german weather service): See coloumn 'id' and search for your location.

Examples:

• id = 10389 for Berlin, Alexanderplatz
• id = K1174 for Heinsberg (NRW)
• id = K4476 for Tirschenreuth (BY)

Look ahead Hours

Hours to look ahead into the future. Use 0 to get actual weather.

When you set Look ahead hours, the weather data returned will be for x hours in the future. If you look at the temperature for 12 hours ahead for example, you should see a different number returned unless that temperature happens to be exactly the same to the actual temperature.

Note: This configuration property is superseeded by an input msg with a msg.payload.lookAheadHours element (see secion Input below).

Omit message on start

For compatibility with the openweathermap node, this node emits a message with current weather data immediately once the flow is deployed. If this is not desirable, it can be deactivated here. In any case, the node will emit a message after the repeat cycle in case this is set (see below) or once it is triggered by receiving a message.

Repeat

Automatic cyclic repeat (in seconds). If set to a value > 0, the node automatically repeats the DWD data query and emits a msg telegram at its output.

Hint: Do not set this value too small to avoid unneccesary traffic. Appropriate repeat intervals are several minutes due to the weather data does not change at a higher rate than 15-20 seconds, typically one minute.

Additional fields

Basics

With the Additional fields property you can add further weather data to msg.payload.
Possible elements can be selected from this MOSMIX element list from the DWD.
Several elements can be selected and have to be comma-separated.

Output modifiers

The data provided by DWD is on an hourly basis. By default, output values will be linearly interpolated. Some data fields such as "SunD" (Yesterdays total sunshine duration) in the below example are only provided once every X hours or even once per day and interpolation does not make sense. With modifiers you can change how the output value is calculated in those cases. When not specifying a modifier, the value for those fields will be 'NaN' in most cases.

Output modifiers are added as a prefix to the field name. So instead of just using "SunD", you would use ">SunD" to return today's predicted total sunshine duration.

Available modifiers:

• < go back in time to find the last value for this field
• > go ahead in time to find the next value for this field
• ° assume the field value is a temperature and convert it from Kelvin to Celsius

See also: Node issue "NaN error with precipitation 24h and 3h".

Example

The following figure shows the msg.payload structure of an example with "FF,FX1,>SunD,SunD1,R101,°Td,VV,W1W2,wwTd":

Fig. 4: Additional fields example msg.payload contents

MOSMIX elements used by the node

The following MOSMIX elements are used as the basis for the node's msg.payload values:

• payload.tempc: "TTT"
• payload.humidity: "Td" and "TTT"
• payload.windspeed: "FF"
• payload.winddirection: "DD"
• payload.precipitation_perc: "wwP"
• payload.precipitationNext24h: "RR1c"

Name

A name for the wheather location may be set via this property.

Topic

Allows to configure the topic for emitted messages.

Input

The node is triggered by any input msg with arbitrary contents.

If the input msg contains the element msg.payload.lookAheadHours its value superseeds the Look ahead Hours node configuration property.

Outputs

The node emits a msg whenever it is triggered by an input msg or at the configured Repeat interval (see node configuration above).

The default msg attributes are:

• payload.station - Description (location) of the station
• payload.tempc - Temperature in °C
• payload.humidity - Relative humidity
• payload.windspeed - Windspeed in m/s
• payload.winddirection - Winddirection in °
• payload.precipitation_perc - probability of rain in per cent (so a value of 4 means 4%)
• payload.precipitationNext24h - total precipitation in the next 24 hours in kg/m2
• payload.forecast_dt - epoch timestamp of the forecast
• payload.precipitation% - DEPRECATED, same as payload.precipitation_perc

In case of a value set to the node configuration property Topic the output msg contains an additional attribute msg.topic with the set content in addition to the msg.payload object.
As an example, if the node configuration property Topic is set to "myTopic" the output msg looks like this:

Fig. 5: Example output msg with topic configuration property set to "myTopic"

Examples

Remark: Example flows are present in the examples subdirectory. In Node-RED they can be imported via the import function and then selecting Examples in the vertical tab menue.

Basic example

This example shows how to trigger the node and how to evaluate the msg.payload.tempc element.

BasicExampleFlow.json

Fig. 6: Basic example flow

Example using Additional fields

The configuration of the property Additional fields was set to "FX1,SunD1,VV". Therefore the elements msg.payload.FX1 (max. wind gust in the lasts hour), msg.payload.SunD1 (sunshine duration in the last hour) and msg.payload.VV (visibility) appear additionally at the output.

AdditionalFieldsExampleFlow.json
Fig. 7: Example with Additional fields flow

Note that often the values have to be scaled to have more 'handy' values.

License

Apache 2.0 (c) Christian Stein