Temporal Variogram Can we compute temporal variograms just like spatial variograms? I know about spatio-temporal variograms but I am more interested in doing a comparison of separate spatial and temporal variograms and then comparing the results with spatio-temporal variograms to better understand the concepts. So far I have not gotten a straight answer from reading. 
In my mind to calculate a temporal variogram we have to take 3 columns x, y and z. X and Y acting as coordinates and z being the value. If we have columns with x=zeros and y=date/time,
x y z
0 1/01/2004 0:00 15
0 1/04/2004 0:00 224
0 1/08/2004 0:00 34
0 1/12/2004 0:00 65

can I do that? If not, what should I do to calculate the spatio-temporal variogram with temporal variations.
 A: Of course you can use variograms also for time series data. The variogram has one advantage as compared to the autocorrelation function, it only needs the hypothesis of intrinsic stationarity, not stationarity (definitions can be found here: Intrinsic spatial stationarity: doesn't it only apply for small lags?).  So it only assumes that the expectation of differences are zero, but the global mean, for instance, do not need to exist.  So the variogram is defined even in cases where the variance do not exist, while the autocovariance function do need that the variance exists.  So, potentially the variogram could be of interest for time series with long-range dependence.  But I have never used it this way myself, nor seen it used. 
But here is a relevant paper:  https://rss.onlinelibrary.wiley.com/doi/abs/10.1111/1467-9884.00101
A: If I have understood you correctly, instead of a 2D "smearogram", make a 3D "blobogram." Making it somewhat transparent would help. That is, plot three coordinates, for example, difference in distance, at time, and versus difference in concentration.
