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Chasing droplets

Logo https://tudelft.pageflow.io/chasing-droplets

Research

Welcome to the Costa Rican jungle. A dense tropical forest, which hides bright coloured snakes between the ferns and monkeys in the trees. This ecosystem has one of the most complex water cycles in the world, therefore it is the ideal setting for PhD candidate Cesar Jimenez Rodriguez to study evaporation.
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With climate change upon us, it is essential to understand the earths' water system. If one part of the system changes, the effects may be enormous. 

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As opposed to rainforests, forests in temperate climates generally consist of only one dominant type of trees, a so called canopy layer. Cesar: "The tropical forest, however, are so complex that even the presence of a dominant tree species does not mean that it rules the water fluxes to the atmosphere''. 

Cesar aims to determine the contribution of water vapor from different canopy layers to the total water exported to the atmosphere.

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“Rains during the dry season are a constant feature of these tropical forests. Once the rain stops, vapor plumes from the forest canopy move water back into the atmosphere. That is the water we chase.”
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''Some plants with lower abundance, or smaller size can provide the same amount of water of even more due to their physiological processes or water access. That is why I measure the evaporation of the different canopy layers''. But how does that work?
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Sometimes research requires strong nerves. Some of the trees in the area are over 50 meters. Making accurate measurements of the canopy layer means that Cesar needs to climb into the measurement towers time and again.


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But all the climbing is worth it. ''Up in the tower you are rewarded with amazing data, great views and a lot less mosquitoes than in the forest''.
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How do you measure evaporation? How do you chase the droplets and identify where they come from? 

First of all, you need to go into the field (or jungle in this case).



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Cesar collects soil water, rainfall and evaporation from leaves from different canopy levels and identifies the water based on isotopes.
Isotopes are atoms of the same element which have a slight difference in their nucleus (more or less neutrons). This means that the isotopes vary slightly in weight.


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That means that water molecules carry unique fingerprints, based in part on differing proportions of the oxygen and hydrogen isotopes that constitute all water.

Analyzing the composition of a sample makes it possible to determine where the water came from. By identifying the 'fingerprint' of a sample Cesar can track the probable source. Thereby illuminating in which way the way water or vapor contributes to the water cycle.  
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For more information about Cesar, please visit the TU Delft website

This research is made possible by:
NWO (Dutch Organisation for Scientific Research, partially through the VENI grant of dr.ir. Miriam Coenders)
PINN - MICITT (Costa Rican Ministry of Science, Technology and Telecommunications, contract: PED-032-2015-1 )
and
OTS (Organisation for Tropical Studies, Glaxo Centro America Fellowship - fund 502) 

These organisations enable his investigations.

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PhD

La Selva Biological Station accounts for more than 50 years of research experience in Tropical Ecology. The field station has the equipment to do high quality research, including a set of towers with internet connection with optic fiber, electricity and basic laboratories.
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But what makes it the best spot for Cesar's research is the supporting staff. ''Their knowledge is unmeasurable and this allows you to step in a tropical forest with a strong basic knowledge about biotic and abiotic conditions; studied for decades in advance helping you to understand the phenomena that you are interested in''.
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Costa Rica

''First of all, Costa Rica is my home country and I do want to understand the processes that happen in a complex ecosystem as the Tropical Wet Forest.''


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''Doing research in Costa Rica is a known feeling for me and it is enjoyable if you like the contact with nature. It is not a wild environment as you can find in the middle of the Amazon, however the country size allows you to be in a close contact with Nature. I’m working along the vertical axis of the forest, from ground level to the reachable highest point of the canopy.''
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Working in the Costa Rican jungle means you sweat a lot, not necessarily for the high temperatures, but because the air is so humid that the sweat does not evaporate from your skin.


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Best chances of understanding the weather is by working with the people of the region. There is no app to tell you when it will rain. Even on a nice sunny day you can have quick showers without warning, located over small spots on the landscape, if you are lucky you can see the rain approaching from the horizon towards you.
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