TAHMO In 2014, the Trans-African Hydro-Meteorological Observatory (TAHMO) was officially founded as a Dutch not-for-profit foundation. Now, five years later, TAHMO has become the largest provider of scientific weather and climate data for sub-Sahara Africa. The present network of 500 stations in 20 countries still falls well short of the final network of 20,000 stations but we should already consider TAHMO as a major success, as it has shown that it is possible to run a cost-effective observation network. TAHMO distinguishes itself through different approaches with respect to technology, operation, and financial sustainability. Innovations in all these aspects are needed to move forward and will be discussed in some detail during the presentation. Technology TAHMO has partnered with METER Group in the co-design of the current weather station. Originally, the thought was to develop a very cheap ($200) station ourselves but the engineering needed to move from a proof-of-concept to a fool-proof concept is more complex than one may think. Many ideas have been bounced between the two teams and tested in the field in Africa, leading to a third generation apparatus that is very robust. Operation Over 90% of TAHMO stations are placed at (secondary) schools. This provides some physical but especially social protection. Educational material is provided to engage teachers and students and to encourage them to help out with simple maintenance, such as cleaning. Also the IT backbone, developed with support through IBM's Corporate Social Responsibility activities is worth mentioning as it supports state-of-the-art QA/QC. Financial sustainability So far, most stations have been funded through projects funded by different donors and agencies. A large investment by IBM / Weather Underground formed the basis for a rapid expansion of 333 stations. To ensure long-term financial sustainability, TAHMO provides data services to commercial users. Clearly, value chains run from raw data to actionable information. Willingness to pay increases exponentially along that chain. For this reason TAHMO has become part of a network of entities that bridge the gap between weather station and information market. ... Read more

Trees play a crucial role in the water, carbon and nitrogen cycle on local, regional and global scales. Understanding the exchange of momentum, heat, water, and CO 2 between trees and the atmosphere is important to assess the impact of drought, deforestation and climate change. Unfortunately, ground measurements of tree properties such as mass and canopy interception of precipitation are often expensive or difficult due to challenging environments. This paper aims to demonstrate the concept of using robust and affordable accelerometers to measure tree properties and responses. Tree sway is dependent on mass, canopy structure, drag coefficient, and wind forcing. By measuring tree acceleration, we can relate the tree motion to external forcing (e.g., wind, precipitation and related canopy interception) and tree physical properties (e.g., mass, elasticity). Using five months of acceleration data of 19 trees in the Brazilian Amazon, we show that the frequency spectrum of tree sway is related to mass, canopy interception of precipitation, and canopy–atmosphere turbulent exchange. ... Read more

Trees play a crucial role in the water, carbon and nitrogen cycle on local, regional and global scales. Understanding the exchange of heat, water, and CO2 between trees and the atmosphere is important to assess the impact of drought, deforestation and climate change. Unfortunately, ground measurements of tree dynamics are often expensive, or difficult due to challenging environments. We demonstrate the potential of measuring (bio)physical properties of trees using robust and affordable acceleration sensors. Tree sway is dependent on e.g. mass and wind energy absorption of the tree. By measuring tree acceleration we can relate the tree motion to external loads (e.g. precipitation), and tree (bio)physical properties (e.g. mass). Using five months of acceleration data of 19 trees in the Brazilian Amazon, we show that the frequency spectrum of tree sway is related to mass, precipitation, and canopy drag. This presentation aims to show the concept of using ccelerometers to measure tree dynamics, and we acknowledge that the presented example applications is not an exhaustive list. Further analyses are the scope of current research, and we hope to inspire others to explore additional applications. ... Read more

Over the past ten years, Distributed Temperature Sensing (DTS) has been applied for monitoring many different environmental processes, from groundwater movement, to seepage into streams and canals, to soil moisture, and internal waves in lakes. DTS uses optical fibres, along which temperatures are determined by measuring Raman shifts in light that scatters back after a laser pulse has been sent into the fiber. Over the past decade, performance of DTS equipment has dramatically improved. It is now possible to determine fiber temperatures with 0.05 K accuracy, for each 25 cm along a fiber optic cable. With typical spatial resolutions of 1 m, cable lengths can run up to 5 km. Accuracy improves with integration over longer sampling intervals, but measurements over 60 s can give 0.1 K accuracy with proper in-field calibration. DTS can also be used for atmospheric properties such as air temperature, vapor pressure, and wind speed. This presentation provides a complete overview of recent advances in atmospheric DTS observations. Air temperature is the simplest, as one simply has to suspend a fiber optic cable along the profile of interest. This can be from a balloon or along poles. Care has to be taken to correct for radiative heating of the cable. Using a thin white cable minimalizes radiative effects and normally brings the measured temperature to within 1 K of actual air temperature, sufficient for studies on effects of shading in natural and urban landscapes. It is also possible to correct for radiative heating by modeling in some detail the cable’s thermal behavior or by using two cables of different diameters. Supporting structures may also have an effect on cable temperatures, which should be minimized or corrected for. Water vapor can be measured by comparing the temperatures of wet and dry cables. These wet and dry bulb temperatures allow derivation of humidity profiles, which, in turn, allows for Bowen-ratio type of calculations of latent and sensible heat fluxes. This has proven especially useful in otherwise difficult to measure profiles such as through forest canopies. Wind speed can be measured by including a conductive element in the fiber optic cable and heating the cable actively by sending a current through that element. In effect, the cable then acts as a hot wire anemometer but then over long lengths of cable and with high spatial resolutions. When carefully executed, experiments with heated cables give very detailed insight into turbulent processes in the lower boundary. It is even possible to resolve bigger individual turbulent and sub-meso-scale eddies for studying fast evolving fluid flows (orders of seconds). A comprehensive overview of atmospheric applications will be presented, together with pitfalls, common errors, and practical tips to avoid those in the field. ... Read more

The session that this poster is in, the: “Self-made sensors and unintended use of measurement equipment”, also known as the “MacGyver-session” has had 7 years of scientists contributing their self made devices, hacks and solutions with the hydrological community. In 2009, the first session was held at the AGU fall meeting and since 2011 a session is also organised at the EGU General Assembly. On this poster, and in the accompanying review paper, we will present an overview of the work presented in the last 7 years, cataloging the work of the inventive scientists who have contributed to these successful, and above all: fun, sessions. ... Read more