Chiel van Heerwaarden
With our group on clouds, radiation, and land-atmosphere interactions and atmospheric convection and turbulence as the processes that bring these topics together. We aim to study these topics with a combination of modelling and field observations. We aim not only to learn more about the physics, but we also try to innovate the tools that we use, for instance with GPU computing for 3D radiation computations, novel instruments to measure surface irradiance, or machine learning to learn and emulate physical processes.
My research explores how machine learning techniques can be used to model (near-)surface turbulent fluxes in the atmospheric boundary layer with higher accuracy. Specifically, I explore the potential of machine learning techniques for modelling 1) sub-grid turbulence in partly-resolved MicroHH simulations and 2) the actual surface evapotranspiration as measured (by eddy-covariance systems) at irrigated fields in the desert. (In both cases, we find that machine learning techniques show promise, but also challenges still need to be overcome
The aim of my PhD research is to better understand the complex interactions between clouds, solar radiation, and the Earth's surface. I work on developing radiative transfer models that are very accurate, yet fast enough to be integrated in high-resolution simulations of the atmosphere. That way, we can learn not only how clouds drive irradiance variability, but also how irradiance variability drives clouds.
In the SLOCS project, I work on observing solar irradiance variability on the scale of clouds using a spatial network of low-cost custom made radiometers. I use these spatial observations and existing solar radiation datasets to better understand what clouds are doing with solar radiation at the small, intra-day scales. But also, these observations serve as validation for numerical modelling.
I work on modelling solar radiation, more specifically, my focus is on finding simple and fast methods to model the variability of radiation at the surface. To this end, I work with 3D simulation of cumulus clouds with MicroHH with simple radiative transfer calculations and I compare my model simulations to observations. I’m developing a method that can be used to add more realism to these simple radiative transfer calculations.
My research focuses on improving short-term (2-6 hours ahead) UV and solar radiation forecasts using satellite observations. Satellites can provide data for large and remote areas. However, compared to ground observations, they are often lacking in terms of spatial and temporal resolution. I work on methods to enhance the spatial resolution of satellite retrievals and include estimates of high-frequency fluctuations of solar radiation in the forecast.
I am currently enrolled in the master programme Earth and Environment and am now working on my master thesis under the supervision of Wouter and Chiel. For my thesis I try to find the relation between cloud velocity and wind speed, because these might not be one to one linked. Maybe the cloud velocity is linked to the wind profile in the boundary layer, or maybe the surface fluxes are more important. I wouldn’t know, but that’s what I am trying to figure out.
In my thesis I will look into a controversial theory called the biotic pump. The biotic pump links the phase change of water vapor in the atmosphere to atmospheric pressure and according to the authors it is a main driver of atmospheric circulation. Although already more than 10 years old, the theory remains under debate. It seems that the authors are unable to convince everyone of the theory, whereas the criticists are unable to disprove the theory in a convincing way. Therefore, I will try to contribute to (dis)proving the theory by doing a literature study on both the papers that propose the biotic pump theory as well as the reviews of the criticists. It is my goal to implement their theories/assumptions in a simple atmospheric model to see how this in the end influences atmospheric pressure and as a result atmospheric circulation.
I am currently doing the Master Earth and Environment focusing on meteorology. My primary interests are related to small-scale phenomena such as cloud microphysics. Currently, I am investigating extreme dry convective wildfires for my master thesis. The goal is to better understand the wildfire plume dynamics, such as the rotational motions within the plume.
Tom van der Velde
During my master thesis, which is part of the master Earth and Environment, I am investigating the distribution of diffuse radiation over the sky hemisphere. Especially clouds can cause large shifts in this distribution. Hence, the aim of my thesis is to get more insight in the relationship between the diffuse radiation distribution and cloud composition, which could help in making more accurate predictions for the amount of radiation on tilted surfaces (e.g. solar panels).
- Anja Raznjevic (defense upcoming in 2023, now at Rabobank)
- Imme Benedict (defense in 2020, now at WUR as a teacher / researcher)