I have found through granger causality and information flow (by Liang) that the strongest causation of NAO to rainfall happens at a time lag of 8 months. However, I have not been able to find any paper which agree with my finding. Do you know any paper that shows a strongest time-lagged of several months, correlation ?
Can tell me why it is so important to find similar results? If you can explain your findings, you should good to go.
Dear Anastasia
I really believe that your relation found makes sense. The literature might not be very clear on the lag between NAO, ENSO and other teleconnections vs precipitation but it is in some sense known that this lag exist.
See the following paper:
Article Lagged influence of Atlantic and Pacific climate patterns on...
The above article shows lag up to 3 seasons.
I myself studied relationship between NAO, ENSO and the following intensity of pollen season (which depens on precip, temp.) and found similar relationship
i.e. the NAO of last year would apparently influences the impact of the pollen season this year. So lag for 8 months up to almost 2 years can influence terrestrial ecosystems. That was my findings. Therefore, it is quite possible that NAO of last year also influecnes precipitation this year.
See Statistical modeling, forecasting and time series analysis of birch phenology in Montreal, Canada
📷
- December 2017
- Aerobiologia 33(4):1-26
- DOI:
- 10.1007/s10453-017-9488-0
Dear Anastasia,
The time lag you are observing between the phases of the North Atlantic Oscillation (NAO) and rainfall intensity (presumably in Crete) are very plausible.
It should be clear that atmospheric pressure at sea level (SLP) in Iceland or in the Azores cannot directly and immediately affect precipitation processes elsewhere. However, those pressure fluctuations are the result of--and generate further--modifications in the general circulation of the atmosphere. In other words, the atmosphere, as a compressible fluid, is permanently trying to react and adjust to changes in its physical properties by moving air around. Those adjustments propagate in the form of waves, fronts, etc. and those perturbations take a while to reach other locations.
I can't tell you whether it is reasonable for those effects to show up at your location of interest after 8 months (it probably depends in part on the distance between the locations involved), but some delays are to be expected and other authors have found comparable time lags in their investigations. Remember also (1) that NAO phases are not instantaneous event but evolve over some period of time, and (2) that other local factors may be responsible for dampening or amplifying those effects. So you should not expect a one-to-one correspondence between a NAO event and a fluctuation of precipitation at some remote place.
You will find plenty of publications on those teleconnections and the time lags involved by searching the web for "ENSO NAO precipitation time lags" or similar keywords.
I hope this helps. Michel.
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