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These conditions are combined together by the logical AND operator. So a row of data is only added to the results when all the conditions match. |
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Sample data
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This is a summary of the data files used for the examples:
| File | Structure | Description | ||||||
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| Classic radiosonde data. One message contains a vertical profile for one station with various parameters (e.g. temperature, wind etc.) on a set of pressure levels. | ||||||
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| Tropical cyclone data. One message contains a full ensemble forecast with minimum mean sea level pressure and maximum wind speed values along the forecast tacks. |
Extracting a single parameter
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| Example | Filter | Results | Comments | ||
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For all the messages: extract the first temperature value which is greater than 300 K and also extract the pressure on which it occurs |
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| Here we explicitly say the we only want the matching temperature values which appear inside a pressure block (in these messages this is always the case). By using the coordinate condition pressure will be extracted as well because the EXTRACT_COORDINATE option is On by default. | ||
| For all the messages: extract the first temperature value which is greater than 300 K and the pressure is less than 950 hPa |
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| Here we further refined the coordinate condition. | ||
| For all the messages: extract the temperature value on the 500 hPa pressure level |
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For station 78016: extract the temperature on the second pressure level |
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| Here we restricted the filter form one station (message) only and used a rank condition for the coordinate. | ||
| For station 78016: extract the temperature on the first 6 pressure levels |
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| For coordinate rank a list of values can be specified. | ||
| For station 78016: extract the temperature on the 925, 850 and 700 hPa pressure levels |
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Extracting multiple parameters
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When we use multiple coordinate conditions these are assumed supposed to conceptually be nested, i.e. there is an inner coordinate and the other, inner coordinates, are nested in it. This puts a constrain on the order the coordinate conditions are specified: the outer coordinate has to be specified first then the other coordinates in the nesting order.
In the examples below we will use pressure and work with two coordinates to extract radiosonde data on certain levels: pressure will be the outer coordinate and verticalSoundingSignificance, which defines the type of the pressure levels, the inner coordinate. It reflects how a pressure block is built up in our radiosonde BUFR file:
| Task | Filter | Results | Comments | ||
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For station 78016: extract all the temperature values on standard pressure levels |
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| For station 78016: extract all the temperature values on temperature significant levels where the pressure is less than 500 hPa |
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Tropical cyclone tracks
| Example | Filter | Results | ||
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For the first message (storm IN-FA) extract the storm centre pressure values along the track for ensemble number =2 |
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