Should we use a simple or complex model for moisture recycling and atmospherix moisture tracking?

Should we use a simple or complex model for moisture recycling and atmospherix moisture tracking?

Van der Ent, R.J.
Tuinenburg, O.A.
Knoche, H.R.
Kunstmann, H.
Savenije, H.H.G.

Civil Engineering and Geosciences

Water Management

2013-12-06

This paper compares state-of-the-art atmospheric moisture tracking models. Such models are typically used to study the water component of coupled land and atmosphere models, in particular quantifying moisture recycling and the source-sink relations between evaporation and precipitation. There are several atmospheric moisture tracking methods in use. However, depending on the level of aggregation, the assumptions made and the level of detail, the performance of these methods may differ substantially. In this paper, we compare three methods. The RCM-tag method uses highly accurate 3-D water tracking (including phase transitions) directly within a regional climate model (online), while the other two methods (WAM and 3D-T) use a posteriori (offline) water vapour tracking. The original version ofWAM is a single-layer model, while 3D-T is a multi-layer model, but both make use the “well-mixed” assumption for evaporation and precipitation. The a posteriori models are faster and more flexible, but less accurate than online moisture tracking with RCM-tag. In order to evaluate the accuracy of the a posteriori models, we tagged evaporated water from Lake Volta inWest Africa and traced it to where it precipitates. It is found that the strong wind shear in West Africa is the main cause of errors in the a posteriori models. The number of vertical layers and the initial release height of tagged water in the model are found to have the most significant influences on the results. With this knowledge small improvements have been made to the a posteriori models. It appeared that expanding WAM to a 2-layer model, or a lower release height in 3D-T, led to significantly better results. Finally, we introduced a simple metric to assess wind shear globally and give recommendations about when to use which model. The “best” method, however, very much depends on the research question, the spatial extent under investigation, as well as the available computational power.

http://resolver.tudelft.nl/uuid:2b1a9618-bbfa-4721-a2d9-e9700142dbb3

https://doi.org/10.5194/hess-17-4869-2013

European Geosciences Union (EGU)

1027-5606

http://www.hydrol-earth-syst-sci.net/17/4869/2013

Hydrology and Earth System Sciences, 17 (12), 2013

Institutional Repository

journal article

© 2013 The Author(s)
CC Attribution 3.0 License