articles by Szymon Malinowski
As a complement to measurements, numerical modeling facilitates improved understanding of the com... more As a complement to measurements, numerical modeling facilitates improved understanding of the complex turbulent processes in the stratocumulus-topped boundary layer (STBL). Due to limited computational resources simulations are often run at too coarse resolutions to resolve details of cloud-top turbulence and potentially in computational domains too small to account for the largest scales of boundary layer circulations. The effects of such deficiencies are not fully understood. Here the influence of resolution/ anisotropy of the computational grid and domain size in under-resolved implicit large-eddy simulation of the STBL is investigated. The performed simulations are based on data from the first research flight of the DYCOMS-II campaign. Regarding cloud cover and domain-averaged liquid water path, simulations with hori-zontal/vertical grid spacing of 35/5 m, 70/10 m, and 105/15 m are found to agree better with measurements than more computationally expensive simulations with isotropic grid boxes, e.g., with 10/10 m or 15/15 m grid spacing. While decreasing the vertical grid spacing allows more representative simulation of the thin, turbulent, stably stratified interfacial layer between the STBL and the free troposphere, coarsening the horizontal resolution dampens vertical velocity fluctuations in this region and mimics the observed anisotropy of stably stratified small-scale turbulence near the cloud top. The size of the computational domain is found to have almost no impact on mean cloud properties. However, increasing it from 3:533:5 km 2 to 14314 km 2 does lead to the occurrence of larger coherent updraft structures. Increasing it further to 21321 km 2 shows little or no increase in the updraft size.
Buoyancy reversal by evaporative cooling in entrainment holes has a minimal influence on stratocu... more Buoyancy reversal by evaporative cooling in entrainment holes has a minimal influence on stratocumulus (Sc) observed during the Physics of Stratocumulus Top (POST) aircraft field study held off the California coast in 2008. High-resolution temperature and microphysics measurements show only small differences for Sc with and without buoyancy reversal predicted by mixing fraction analysis that relates mixtures of cloudy air and freeatmospheric air to buoyancies of the mixtures. The reduction of LWC due to evaporation in the holes is a small percentage (average ;12%) of liquid water diluted in the Sc by entrainment from the entrainment interface layer (EIL) located above unbroken cloud top where most mixing, evaporation, and reduction of the large buoyancy jump between the cloud and free atmosphere occur. Entrainment is dominated by radiative cooling at cloud top.
Retrieving atmospheric turbulence information from regular commercial aircraft using Mode-S and ADS-B
Navigational information broadcast by commercial aircraft in the form of Mode-S EHS (Mode-S Enhan... more Navigational information broadcast by commercial aircraft in the form of Mode-S EHS (Mode-S Enhanced Surveillance) and ADS-B (Automatic Dependent Surveillance-Broadcast) messages can be considered a new source of upper tropospheric and lower stratospheric turbulence estimates. A set of three processing methods is proposed and analysed using a quality record of turbulence encounters made by a research aircraft. The proposed methods are based on processing the vertical acceleration or the background wind into the eddy dissipation rate. Turbulence intensity can be estimated using the standard content of the Mode-S EHS/ADS-B. The results are based on a Mode-S EHS/ADS-B data set generated synthetically based on the transmissions from the research aircraft. This data set was validated using the overlapping record of the Mode-S EHS/ADS-B received from the same research aircraft. The turbulence intensity, meaning the eddy dissipation rate, obtained from the proposed methods based on the Mode-S EHS/ADS-B is compared with the value obtained using on-board accelerometer. The results of the comparison indicate the potential of the methods. The advantages and limitation of the presented approaches are discussed. © 2016 Author(s).
Papers by Szymon Malinowski
Journal of the Atmospheric Sciences, Oct 1, 2022
In this work we show how to retrieve information about temporal changes of turbulence in the atmo... more In this work we show how to retrieve information about temporal changes of turbulence in the atmosphere based on in situ wind velocity measurements performed by aircraft. We focus on the stratocumulus-topped boundary layer high-resolution data taken by a helicopter-borne platform Airborne Cloud Turbulence Observation System (ACTOS). We calculate two nondimensional indicators, the dissipation factor and the integral-to-Taylor-scale ratio, and study their dependence on the Taylor-scale-based Reynolds number. By analyzing these results, we can identify regions where turbulence is in its stationary state and regions where turbulence decays in time or, on the contrary, becomes stronger. We can also detect nonequilibrium turbulence states, which indicate the presence of rapidly changing external conditions. SIGNIFICANCE STATEMENT: The purpose of this work is to retrieve new information on turbulence in the atmosphere. We consider data from a field study based on in situ observations from a measurement payload below a slowflying helicopter. We show that it is possible to retrieve information on temporal tendencies in a given region from such measurements. We attempt to estimate whether turbulence is in its stationary state, or possibly, turbulence decays due to insufficient production, or, on the contrary, becomes stronger. Such information provide useful knowledge of smallscale processes in the atmospheric boundary layer and can be used to improve their parameterizations.
Details of mixing events at the top of marine stratocumulus observed during ACORES2017
EGUGA, Apr 1, 2019
Quarterly Journal of the Royal Meteorological Society, 2016
The effects of wind shear and radiative cooling on the stratocumulus‐topped boundary layer (STBL)... more The effects of wind shear and radiative cooling on the stratocumulus‐topped boundary layer (STBL) were investigated via a set of large‐eddy simulations. The set‐up of the numerical experiments was based on Flight TO13 from the Physics of Stratocumulus Top (POST) field campaign, in which sensible and latent heat fluxes at the surface were small and thermodynamic conditions prevented cloud‐top entrainment instability.The results demonstrate that the presence of radiative cooling invigorated convective circulations across the STBL and sharpened the inversion above the cloud, while wind shear at the top of the STBL was a source of turbulence in the capping inversion and caused dilution of the cloud top. The flux and gradient Richardson numbers in the capping inversion and in the topmost layer of the cloud were nearly critical.Analysis of the turbulent kinetic energy (TKE) budget and its transport indicated that turbulence in the inversion capping the cloud was produced locally by wind s...
In this paper we propose two approaches to estimating the turbulent kinetic energy (TKE) dissipat... more In this paper we propose two approaches to estimating the turbulent kinetic energy (TKE) dissipation rate, based on the zero-crossing method by . The original formulation requires a fine resolution of the measured signal, down to the smallest dissipative scales. However, due to finite sampling frequency, as well as measurement errors, velocity time series obtained from airborne experiments are characterized by the presence of effective spectral cutoffs. In contrast to the original formulation the new approaches are suitable for use with signals originating from airborne experiments. The suitability of the new approaches is tested using measurement data obtained during the Physics of Stratocumulus Top (POST) airborne research campaign as well as synthetic turbulence data. They appear useful and complementary to existing methods. We show the number-of-crossings-based approaches respond differently to errors due to finite sampling and finite averaging than the classical power spectral method. Hence, their application for the case of short signals and small sampling frequencies is particularly interesting, as it can increase the robustness of turbulent kinetic energy dissipation rate retrieval.
Journal of the Atmospheric Sciences, Aug 1, 2009
This note presents an analysis of several dozens of direct numerical simulations of the cloud-cle... more This note presents an analysis of several dozens of direct numerical simulations of the cloud-clear air mixing in a setup of decaying moist turbulence with bin microphysics. The goal is to assess the instantaneous relationship between the homogeneity of mixing and the ratio of the time scales of droplet evaporation and turbulent homogenization. Such a relationship is important for developing improved microphysical parameterizations for large-eddy simulation of clouds. The analysis suggests a robust relationship for the range of time scale ratios between 0.5 and 10. Outside this range, the scatter of numerical data is significant, with smaller and larger time scale ratios corresponding to mixing scenarios that approach the extremely inhomogeneous and homogeneous limits, respectively. This is consistent with the heuristic argument relating the homogeneity of mixing to the time scale ratio.
Temperature dissipation in convective clouds during ACORES and EUREC4A
Observed and simulated turbulence in cumulus and stratocumulus clouds
EGU General Assembly Conference Abstracts, Apr 1, 2018
Physics of Stratocumulus Top: anisotropic turbulence at the cloud top and entrainment mechanism
EGU General Assembly Conference Abstracts, Apr 1, 2018
On the Influence of Grid Resolution and Domain Size on the Structure and Evolution of the Stratocumulus-Topped Boundary Layer: A Large-Eddy Simulation Study
Entrainment and anisotropic turbulence in the stratocumulus-topped boundary layer: A large-eddy simulation study
Scaling of Temperature and Liquid Water Content in Cloudy Marine Boundary Layer Duringphysics of Stratocumulus Top Research Campaign
Turbulent Inversion: A Missing Piece in the Puzzle of Stratocumulus Entrainment?
Quarterly Journal of the Royal Meteorological Society, 2012
In this survey we consider the impact of turbulence on cloud formation from the cloud scale to th... more In this survey we consider the impact of turbulence on cloud formation from the cloud scale to the droplet scale. We assess progress in understanding the effect of turbulence on the condensational and collisional growth of droplets and the effect of entrainment and mixing on the droplet spectrum. The increasing power of computers and better experimental and observational techniques allow for a much more detailed study of these processes than was hitherto possible. However, much of the research necessarily remains idealized and we argue that it is those studies which include such fundamental characteristics of clouds as droplet sedimentation and latent heating that are most relevant to clouds. Nevertheless, the large body of research over the last decade is beginning to allow tentative conclusions to be made. For example, it is unlikely that small‐scale turbulent eddies (i.e. not the energy‐containing eddies) alone are responsible for broadening the droplet size spectrum during the i...
Low-cost devices for particulate matter measurements are characterized by small dimensions and li... more Low-cost devices for particulate matter measurements are characterized by small dimensions and light weight. This advantage makes them ideal for drone measurements, where those parameters are crucial. However, they also have some issues, like the values of particulate matter from low-cost optical particle counters can be biased by high ambient humidity. In this article, we are evaluating low-cost optical particle counter Alphasense OPC-N3 for measuring the microphysical properties of fog. This study aimed to show that OPC-N3 not only registers aerosols or humidified aerosols but also registers fog droplets. The study was done on the rooftop of Institute of Geophysics, University of Warsaw, Poland, during autumn-winter 2021. To validate the results, the data from OPC-N3 were compared with data obtained from the reference instrument, which was Oxford Laser VisiSize D30. VisiSize D30 is a shadowgraph device able to register photos of individual droplets. Taking into consideration the effective radius of droplets, it is possible to differentiate low-visibility situations between fog conditions (which are not hazardous for people) from haze events, when highly polluted air can cause health risks to people. The compared microphysical proprieties were liquid water content (LWC), number concentration (N c), effective radius < r ef f > and statistical moments of radius. The Pearson correlation coefficient for LWC was 0.91, N c was 0.94, and for < r ef f > was 0.63. Overall, these results suggest a good compliance between devices. However, the OPC-N3 has to be corrected in reference to professional equipment. To conclude, our study provides the foundation for a new application of the optical particle counter Alphasense OPC-N3 within drones to measure the vertical profiles of the microphysical properties of fog.
Naukaoklimacie.pl - popular science blog, quizz and social media about climate change
EGU General Assembly Conference Abstracts, Apr 1, 2018
Numerical simulation of convective cloud fields past complex terrain
ABSTRACT We highlight a unique series of multiscale simulations of natural atmospheric flow past c... more ABSTRACT We highlight a unique series of multiscale simulations of natural atmospheric flow past complex terrain of southern Poland, set in the scenario of a summer NW synoptic inflow. The routine hydrostatic mesoscale predictions at 17˜km resolution, using the Unified Model for Poland Area (UMPL meteo.icm.edu.pl) continuously supply the initial, boundary, and ambient conditions high-resolution simulations, using the non-hydrostatic anelastic model EULAG . The EULAG domain 240 x 200 km2 embedded within the UMPL Central European domain (2000 x 2400 km2) has been covered with 4, 2, and 1 km horizontal grid intervals; while keeping the vertical resolution double of UMPL. Notwithstanding the abrupt changes in the nested domainsrq horizontal resolutions, our comparison of simulated cloud fields with the AQUA/TERRA (rapidfire.sci.gsfc.nasa.gov) satelite photographs documents that the evolution (viz. location and timing) of moist convection is well captured in all simulations. As the resolution of the EULAG domain improves, the representation of convective clouds becoms increasingly more realistic. In particular, at 2 km resolution, irregular convective Rayleigh-Benard type cells are observed in simulated boundary layers. These cells are even better seen at 1 km resolution, in which individual shallow convective clouds with bases at 1100m and tops at about 2500m are nicely represented. Consistently, the strongest clouds appear over the intersection of the updrafts in the cells and in the regions where orographic forcing is dominant.
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articles by Szymon Malinowski
Papers by Szymon Malinowski