Agenda of the Meteorology and Air Quality Group

MAQ Colloquium announcement

11 October 2021, 16:00 - 16:40 o'clock

Teams & Gaia 1

Speaker: Bernard Postema (MSc thesis)

Title: Dynamics of Jet Stream, Local Wave Activity, and
Diabatic Processes Over the North Atlantic.

Abstract: Cyclone clustering, the occurrence of multiple cyclones in a small period of time can have grave environmental and socio-economic impacts in Western Europe. The dynamical meteorological causes of cyclone clustering are unclear Several studies suggest that cyclone clustering is related to a strong and extended jet stream, flanked by Rossby wave breaking (RWB), which could converge momentum into the jet. Contrastingly, analysis of the isentropic slope (a measure for baroclinicity) has recently shown that diabatic processes (latent heat release) within cyclones can trigger the formation of the next one, leading to cyclone clustering. This thesis employs a relatively new large-scale meteorological metric, local wave activity (LWA), to study the interplay between the jet stream, RWB, and diabatic processes; in circumstances that promote cyclone clustering. On synoptic timescales, the results show that when the jet stream strengthens, an increase of LWA takes place south of it. The LWA budget equation and the isentropic slope framework indicate that this can (partly) be attributed to diabatic processes in
cyclones. It is also shown that RWB and LWA partly describe the same
non, suggesting that RWB is also related to diabatic processes. Climatologically,
it is found that LWA (and its budget) behaves qualitatively differently based
on the phase of the North Atlantic Oscillation. Together, the results extend
the conceptual model of the large-scale dynamics during cyclone clustering,
showing that diabatic processes influence LWA, which is in tight interplay with
the jet and linked to RWB.

Supervisor: Chris Weijenborg

MAQ Colloquium announcement


11 October 2021, 16.40 - 17.15 uur

Teams & Gaia 1

Speaker: Freek Kortekaas (MSc thesis)

Title: Global TM5 simulations for N2O and evaluation with in-situ and satellite observations.

Abstract: Nitrous oxide (N2O) is the
largest ozone-depleting substance emitted through human activities and the
third most important greenhouse gas. In general, four emission categories of
N2O can be described, adding up to roughly 17 Tg N yr-1: Biomass burning, Oceanic, Natural Soil and Anthropogenic. The spatial and temporal variation of these N2O emissions are still largely uncertain. In this thesis, a prioriemissions from several databases were used to simulate global N2Oconcentrations using Transport Model 5 (TM5). The model was run for twodifferent vertical resolutions (25 and 60 levels), and the output was evaluated
with observations, both in-situ and by satellites. A sensitivity analysis has
been performed to learn how the uncertainties in the input propagate to the
output, and to better understand how N2O is transported in the atmosphere by
showing the influence of each emission category to total N2O concentrations per
TransCom region. The results show that the simulated N2O concentrations are mostly in line with the observations, although the seasonality in southern hemispheric or agriculture-dominant regions has a considerable misfit. The uncertainties are highest in the northern hemispheric mid-latitudes, where anthropogenic emissions are dominant. When increasing the vertical resolution of TM5, the model performance improves, both at the surface and in the stratosphere. All in all, this research shows that TM5 is suitable for modelling N2O concentrations. The next step is to perform inversions, which could greatly improve the spatial and temporal variation of the a priori emissions.

Supervisor: Gerbrand Koren

MAQ Colloquium announcement


18 October 2021, 16.00 - 16.45 uur Teams

Speaker: Janine Fraas

Title & Abstract: will follow 

Supervisor: Arnold Moenen