I'm currently wondering at what latitudes the precipitation water for Europe evaporates. For some reason I can hardly find any data on where the source of the vapour can be, which is then transported to Europe by advection with the westerly winds. Do you know any reliable sources or, even better, online models?


2 Answers 2


A challenge is going to be "which moisture is from where". Because the atmosphere doesn't ever completely empty of moisture, for any given precipitation, which water molecules were from which spot?

But a satellite loop of precipitable water (the amount of water vapor in the tropospheric column) like the MIMIC-TPW2 one from CIMMS-Wisconsin should help to shed light on your question. Basically looking at the animation the lion's share of the moisture making it to Europe looks to be a mix of nearer northern Atlantic moisture -- particularly from the warmer Gulf Stream -- and then additional wider-scale evaporation nearer the ITCZ closer to the Equator in the Atlantic plus sub-basins like the Caribbean and Gulf of Mexico.

enter image description here

Perhaps a bit more is from more local areas when winds are reduced, and a bit more distant during cooler parts of the year when the jet stream is more active. But I am confident that overall meteorologically these source areas would be rather consistently dominant throughout the year, as hinted at in this image of annual oceanic latent heat flux shows:

enter image description here (Found on NOAA page about Jet Stream, indicated as from Wood's Hole OA Flux Project)

That image, plus a close look at the animation, both seem to hint that the greatest percentage of your moisture tends to come from latitudes more like 30 north. I might have thought it was more equally balanced with the deeper tropics. Either way it's going to be the region roughly between the Equator and about 40 North where the vast majority of your moisture comes from, as that's where SSTs are much warmer... with the moisture carrying capacity of air almost doubling between 20°C and 30°C (and again between 10°C and 20°C), meaning that SSTs and air (low) temperatures nearer 25-30°C bring much more significant amounts of moisture.

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    $\begingroup$ The paper Moisture sources of heavy precipitation in Central Europe in synoptic situations with Vb-cyclones offers an interesting dissent to me. They indicate their model simulations of strong precip events show "overall, up to 80% of the precipitation originates from the European continent, indicating the importance of continental moisture recycling, especially within the respective river catchment. Other major moisture uptake regions are the North Sea, the Baltic Sea, the North Atlantic, and for a few events the Black Sea" $\endgroup$ Commented Jun 29, 2022 at 20:45
  • $\begingroup$ And "the Vb-cyclones with the highest precipitation are associated with anomalously high evaporation in the Mediterranean Sea, even though the Mediterranean Sea is only a minor moisture source region on average" But that's only specific types of cyclones, ones that grow more locally. And honestly, I am still a bit surprised by the results and would take them with a grain of sand. But just lays a counterpoint to my thoughts/images. $\endgroup$ Commented Jun 29, 2022 at 20:53
  • $\begingroup$ You may also have a little interest playing with the forward/backward source trajectories at ready.noaa.gov/hypub-bin/trajsrc.pl $\endgroup$ Commented Jun 30, 2022 at 1:41
  • $\begingroup$ I now realize by looking at your other questions that you may've been looking for a more explicit, scientific calculation of objective values, and some of my details may have been basic for you. But I hope it offers you a start at least :) $\endgroup$ Commented Jun 30, 2022 at 1:43

I recently became aware of this dataset and paper, which I think is the sort of thing you're looking for:

Tuinenburg et al (2020): Global evaporation to precipitation flows obtained with Lagrangian atmospheric moisture tracking, PANGAEA, https://doi.pangaea.de/10.1594/PANGAEA.912710

Tuinenburg et al (2020): High-resolution global atmospheric moisture connections from evaporation to precipitation, Earth Syst. Sci. Data, 12, 3177–3188, https://doi.org/10.5194/essd-12-3177-2020

From which we have Figure 1: The UTrack atmospheric moisture tracking model. (a) The model tracks evaporation through the atmosphere from source cells to target cells using a Lagrangian moisture tracking scheme forced with ERA5 reanalysis data. (b) An example of an “evaporation footprint”, or “evaporation shed”, from the UTrack model. (c) An example of a “precipitation footprint”, or “precipitation shed”:

Fig 1 schematic from from Tuinenburg et al (2020)

I must admit I haven't looked into the data yet, so I don't know how easy it is to use.


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