data_tables_and_unit_conversions.rst
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Sabine Schröder authoredSabine Schröder authored
data tables and unit conversions
data tables
:red:`a. TABLE <parameter>_hourly`
primary key: (id, datetime)
:red:`b. TABLE <parameter>_monthly`
primary key: (id, datetime)
:red:`c. TABLE <parameter>_event`
primary key: (id, datetime)
unit conversions
In the database all parameter series are stored in common default units. These are listed in the table below. In some cases, unit conmversion may be necessary when adding data from the original format into the JOIN database. These conversions are also described below.
| name | display name | formula | default unit | moleweight | unit conversion |
|---|---|---|---|---|---|
| benzene | Benzene | C6H6 | nmol mol-1 | 78.1104 | µg m-3->default: *0.30802 |
| ch4 | CH4 | CH4 | nmol mol-1 | 16.0425 | µg m-3->default: *1.49973 |
| co | CO | CO | nmol mol-1 | 28.0104 | µg m-3->default: *0.85895 |
| ethane | Ethane | C2H6 | nmol mol-1 | 30.0669 | µg m-3->default: *0.77698 |
| mpxylene | m,p-Xylene | C8H10 | nmol mol-1 | 106.165 | µg m-3->default: *0.22662 |
| no | NO | NO | nmol mol-1 | 30.0061 | µg m-3->default: *0.80182 |
| no2 | NO2 | NO2 | nmol mol-1 | 46.0055 | µg m-3->default: *0.52297 |
| nox | NOx | nmol mol-1 | -- | µg m-3->default: not possible! | |
| µg(NO2) m-3-> default: *0.52297 | |||||
| o3 | Ozone | O3 | nmol mol-1 | 47.9982 | µg m-3->default: *0.50124 |
| oxylene | o-Xylene | C8H10 | nmol mol-1 | 106.165 | µg m-3->default: *0.22662 |
| propane | Propane | C3H8 | nmol mol-1 | 44.0922 | µg m-3->default: *0.52982 |
| so2 | SO2 | SO2 | nmol mol-1 | 64.0648 | µg m-3->default: *0.37555 |
| toluene | Toluene | C7H8 | nmol mol-1 | 92.1362 | µg m-3->default: *0.26113 |
| pm1 | PM 1 | µg m-3 | none | ||
| pm10 | PM 10 | µg m-3 | none | ||
| pm2p5 | PM 2.5 | µg m-3 | none | ||
| humidity | Humidity | g kg-1 | kg kg-1->g kg-1: *1000 | ||
| g m-3->g kg-1: *1.2041 | |||||
| *293K/(actual temp[K]) | |||||
| *(actual press[hPa]) | |||||
| /1013.25hPa | |||||
| (for sea-level stations the | |||||
| last factor can be omitted) | |||||
| press | Pressure | hPa | Pa->hPa: *0.01 | ||
| mbar->hPa: *1. | |||||
| temp | Temperature | degC | K->degC: -273.15 | ||
| wdir | Wind direction | degrees | none | ||
| wspeed | Wind speed | m s-1 | knots->m/s: *0.51444 |
Explanation of conversion from concentration to mixing ratio:
We assume that data are reported in concentration "at standard conditions", and we take "standard conditions" to mean 20 degC and 1013.25 hPa. The density of air under these conditions is 1.2041 kg m-3. The mole fraction of a gas X is given by mu = c(X)/dens * mw(air)/mw(X), hence for ozone for example, you will get mu = c(X)/1.2041 * 28.97 / 48.0 = c(X) * 0.50124. Note that µg m-3 is 10^9 times kg m-3, thus this conversion factor directly converts from µg m-3 to nmol mol-1. Useful tools: - Air density calculator (http://www.gribble.org/cycling/air_density.html) - Molecular Mass Calculator (http://www.bmrb.wisc.edu/metabolomics/mol_mass.php)
Note that for NOx no such conversion can be performed, because NOx is a mixture of two components with different molecular masses. Hence, by default the concept of NOx only makes sense for mole fractions (or mixing ratios). Sometimes NOx is given as "NOx expressed as NO2" or "NOx expressed as N". Then you can of course use the conversion formula above using either 46 or 14 as molecular mass.