38 | | The dictionary is a table that defines the conversion between the variables of the model and the standard variables defined in the Vocabulary. The dictionary is a comma-sepparated text file (csv), that is identified with the same name than the dataset, and the extension ''.dic''. In addition, it should be stored in the same directory that the dataset. The creation of the dictionary must be made by the user 'by hand', because it requires knowledge about the characteristics of the data stored in the dataset. The columns of the dictionary are next described: |
| 38 | The dictionary is a table whose aim is twofold: |
| 39 | 1. On the one hand, the dictionary is intended for the translation of generic variables, as idiosyncratically defined in each particular dataset, to the standard variables defined in the vocabulary with their corresponding nomenclature and units. This is achieved by providing a correspondence between the name of the variable as encoded in the dataset (`short_name`) and the corresponding name of the standard variable as defined in the vocabulary (`identifier`), and by applying the corresponding transformation to the native variable in order to match the standard units by means of a `scale` factor and an `offset`. |
| 40 | 2. In addition, the dictionary provides additional metadata often not explicitly declared in the datasets, regarding the ''time'' aggregation of the dataset (often referred to as the ''cell method''). This includes the fields `time_step`, which is merely informative, and describes the time interval between two consecutive values, and the `lower_time_bound` and `upper_time_bound`, which are the values that should be summed to each verification time to unequivocally delimit the time span encompassed by each value. |
| 41 | |
| 42 | The dictionary is a comma-sepparated text file (csv), that by default is identified with the same name than the dataset, and the extension ''.dic'', and stored in the same directory than the dataset, although its name and location can be other if adequately specified in the loading functions. The dictionary must be created ''"by hand"'' by the user, because it requires some ''a priori'' knowledge about the characteristics of the data stored in the dataset, which can be partly obtained from the output of the function `dataInventory`. The columns of the dictionary are next described: |
50 | | identifier short_name time_step lower_time_bound upper_time_bound aggr_fun offset scale |
51 | | 1 ta air 6h 0 0 none -273.15 1.00 |
52 | | 2 zg hgt 6h 0 0 none 0.00 1.00 |
53 | | 3 hur rhum 6h 0 0 none 0.00 0.01 |
54 | | 4 hus shum 6h 0 0 none 0.00 1.00 |
55 | | 5 psl slp 6h 0 0 none 0.00 1.00 |
56 | | 6 ua uwnd 6h 0 0 none 0.00 1.00 |
57 | | 7 va vwnd 6h 0 0 none 0.00 1.00 |
| 57 | identifier,short_name,time_step,lower_time_bound,upper_time_bound,aggr_fun,offset,scale,deaccum |
| 58 | tasmax,Maximum_temperature_at_2_metres_since_last_24_hours_surface,24h,0,24,max,-273.15,1,0 |
| 59 | tasmin,Minimum_temperature_at_2_metres_since_last_24_hours_surface,24h,0,24,min,-273.15,1,0 |
| 60 | tas,Mean_temperature_at_2_metres_since_last_24_hours_surface,24h,0,24,mean,-273.15,1,0 |
| 61 | pr,Total_precipitation_surface,24h,0,24,sum,0,1000,1 |
| 62 | psl,Mean_sea_level_pressure_surface,6h,0,0,none,0,1,0 |