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The origin of moisture feeding up Atmospheric Rivers over the Arctic
* 1 , 1 , 1, 2 , 1
1  Environmental Physics Laboratory (EPhysLab), Facultade de Ciencias, Universidad de Vigo, Ourense, Spain.
2  Department of Atmospheric Sciences, Institute of Astronomy, Geophysics and Atmospheric Sciences, University of São Paulo, São Paulo, Brazil


The Arctic system is one of the most vulnerable region under climate change conditions and it has suffered important changes on last decades. Several recent studies have suggested the influence of moisture transport in the observed sea ice loss on this region. Changes in moisture transport could affect the arctic region by changing the cloud cover, by affecting river discharge or by direct effect of precipitation over the sea ice, for example. Atmospheric rives (ARs) represent one of the main mechanism of global moisture transport, being especially relevant on the connection between lower and higher latitudes. Despite this importance, the influence of ARs over the Arctic system has not been widely study.

The objective of this is work is to establish a first step on the study of the influence of the occurrence of ARs over the polar region. For this purpose, the lagrangian model FLEXPART was used to analyze moisture sources for those regions of maximum occurrence of ARs for the period 1994-2014 in order to analyze the origin of moisture transported by these meteorological structures. The location of ARs affecting the Arctic was realized using an automated algorithm and the region of maximum occurrence was defined taking into account the number of ARs detected for August and September (when sea ice is minimum over the Arctic ocean) over a band of 10° of latitude centered on 60°N. For these regions and considering those days of ARs occurrence, the anomalous moisture sources was defined in relation with mean situation for the complete period.

From the results, main moisture sources for ARs events extends over the North Atlantic and North Pacific oceans, moreover local input of moisture over the region of maximum ARs occurrence seems to be especially relevant. It is interesting to highlight the moisture uptake from Eastern Asia for the month of August. In general it could be conclude that, for ARs events the moisture uptake around and over the maximum occurrence area highly increase becoming relevant sources of moisture feeding up the event.

The location of the origin of the moisture that feed up Arctic ARs is an important step forward on the study of the influence of these structures over the region. Further analysis regarding the contribution of moisture from ARs over the region should be realized in order to complete the relation ARs-sea ice; being this study suitable for a future work.

Comments on this paper
Danica Ciric
Nice work
Dear authors,
I would like to say that you made very interesting study of moisture sources for regions of maximum occurrence of ARs for the period 1994-2014 over the Arctic.
For a future extension of article maybe you can add some numerical calculation or graphs. For example: percentage of contribution of each identified moisture sources via backward experiments.
This is really nice work, congratulations!
Danica Ciric
Marta Vázquez
Dear Danica,

Thank you so much for the sugestion. It definitely would improve the article. We will consider it for a future extension.

Kind regards,

Marta and Co-authors

Ricardo Trigo
Spatial orientation
Dear Authors

I enjoyed your work but have some difficulty visualizing the orientaton of these ARs in the northern Atlantic and Pacific.
I guess that unlike many ARs bound for western Europe and west USA coasts (that are mostly W-E oriented) these ARs have an important meridional component (S-N), correct?
In that regard it would be advantageous if you can show same examples of real ARs that cross these northern latitudes and possible the spatial distribution of their axis orientation.

Best regards

Ricardo Trigo
Marta Vázquez
Dear Dr. Trigo,

Thank you for your comment. We agree and some examples of real ARs crossing these latitudes are necessary to visualize the orientation and characteristics of ARs affecting the Arctic. Moreover, it would be helpful to set the study for the reader.
We definitely will consider including it in a future extension of the article.

Kind regards,

Marta and Co-authors