## Frequently Asked Questions

### Which observational data are used?

Observational data stem from ACTRIS, EMEP, GAW, NOAA, AERONET, PHOTONS, SKYNET, NDACC, ESA, NASA and other networks. The data source can be found on Time Series and Profile plots. If several networks are used for a parameter, a menu pops up showing the reference networks.

PIs, instruments, institutions are shown on time series and profile plots based on metadata information provided through EBAS, EARLINET, EMEP. Suggestions to complete these are very welcome !!

The “OBSERVATIONS-ONLY” Category in the Dataset Menu can be used to see (almost) all observations currently available for model-data comparisons.

### Which version of the data?

We use irregular updates. EBAS/EMEP/ACTRIS/EARLINET data are updated every 1-3 months. Aeronet data approxiamtely every year, except AERONET-NRT data (monthly). Not all plots are renewed at all times. You can check for the revision date on time series plots, see lower left below graph (Rev. YYYYMMDD), which represents the date when the data were updated. See also the “image created YYYY.MM.DD HH.MM” tag, which indicates when a particular plot was created.

### Which stations are used?

An overview can be gathered from the SITELOCATION plot

Example and Time series plots Example

### Standard statistics?

Visible on the SCATTERLOG plot Example) and in SCORE pot Example

### Can I share with colleague? Report Error?

To share what you see on the aerocom webinterface with a colleague, click on mail-share button upper right, (should open an email with URL link) or click on Button “Show URL link to current”, below images, and copy link from popup window appearing. Use this also to report errors to Michael.

### Scroll through all options?

Select a menu and use left/right arrows on keyboard.

### All Models / Stations for year XXXX?

Below the images there is a “Filter Models/Stations on year:” menu, which can be used to preselect the models or station time series plots to those from a given year.

### Compare models synchron?

Use 2/4/6 panels, push “SYNCHRONISE PANEL” Example

### Table of all comparisons?

Not yet available, see graph type SCORE table plot.

### Daily / Monthly?

Most plots are availabile per month, per season, monthly, yearly. Example

### Bias on a map?

Use StatmapBias plots. Example

### Difference to reference version?

DIFFMAP plots are available for some parameters. They show the difference in percent to a reference field as map.

### Display and compare two model/data versions

Use two panels, use “synchronise panels” to see corresponding images Example

(note: the year is not changed on the second panel, so that this setting can also be used to compare different years)

### Meaning of the variables

A long description is visible by hovering over the Parameter menu item, and - in the info text (appearing above image when hovering over image) Example

### Missing variable for a given model/data?

Not all variables make it by default into the AeroCom catalogue. If you have specific idea or request, send email to Michael with variable name.

### 3D diagnostics?

Ozone sonde and vertical extinction profiles are now implemented in AeroCom. Filter models on variables VMR3D_O3 AND EC5323D_AER: Example

### Which year is used?

The year in the menu refers to the year of observation used. Note that anCLIM (or 9999) is used to point to a climatology for either model or observations, typically comprising 5-10 years. The meaning of the “year” may be more complicated for model data, because meteorology or emissions may come from another year. Thus a model simulation of year x maybe be compared to year y in observations. Eventually the reference item contains than also the reference year. Example A different year for the observation and model shows up also in eg x and y-axis of SCATTERLOG plot.

### Is this public?

yes - all world can see version EMEP_svn4738_141231HF_SuperDuper .

### Remove version?

Versions can be removed from website, but that requires email to Jan & Michael.

### Definition of Statistics used in Score tables and in Scatter plots

Explanation for abbreviations used on scatter plots and in score tables:

”#“: Number of “observations” used for statistics (eg daily, monthly or yearly values)

”#st“: Number of sites

“Obs”: Observational mean constructed from all values in scatter plot (e.g. means from yearly station means are different from all daily value means : Example)

“Mod”: Model/Dataset mean constructed from all values in scatter plot, eg correspond to “Obs” values consistently.

“NMB”: Normalized mean bias, = (Mod-Obs)/Obs

“RMS”: Root Mean Square Error: SQRT(Sum( (y'-x')^2)/#)

“R”: Pearson Correlation Coefficient

“RMSbc”: Bias corrected RMS: SQRT(Sum( (ybc'-x')^2)/#) ; ybc' contains all model/data values corrected for the NMB bias. ybc=y*(Sum(x)/Sum(y))

“RMSspatial”: RMS from yearly mean station vales in observations and models. Model values consistently chosen for times when observations are available.

“RMStemporal”: Residual RMS after subtracting RMSspatial from RMS ( RMStemporal = SQRT( RMS^2 - RMSspatial^2 ), assuming error propagation and no covariance in temporal and spatial fields)

…additional statistics in score tables

“Spearman Rank Correlation”: https://en.wikipedia.org/wiki/Spearman%27s_rank_correlation_coefficient

“Spatial yearly Mean Corr Coeff”: Pearson correlation coefficient from yearly mean values

“Seasonal Anomaly Corr Coeff”: Correlation coefficient of local anomalies wrt to annual mean.

“Slope fit forced through zero”: Regression of model on obs data, slope

“Regression coefficient”: Regression of model on obs data, regression

“Regression constant, offset”: Y intercept

“STDDEV(Model)/STDDEV(Data)”. Ratio of standard deviations

“Score (mean relative bias )”: sum(abs(tm-td))/# [ tm= model values, td= obs values ]

“Taylor score”: 4*(1+r)/((1+0.9)*(sm/sd+sd/sm)*(sm/sd+sd/sm) ) [ sm= Stddev of model, sd=Stddev of observations ]

### Known bugs/problems/wishes

-mountain sites are compared from surface level model output, use relative height