46 research outputs found
Improved Micro Rain Radar snow measurements using Doppler spectra post-processing
The Micro Rain Radar 2 (MRR) is a compact Frequency Modulated Continuous Wave (FMCW) system that operates at 24 GHz. The MRR is a low-cost, portable radar system that requires minimum supervision in the field. As such, the MRR is a frequently used radar system for conducting precipitation research. Current MRR drawbacks are the lack of a sophisticated post-processing algorithm to improve its sensitivity (currently at +3 dBz), spurious artefacts concerning radar receiver noise and the lack of high quality Doppler radar moments. Here we propose an improved processing method which is especially suited for snow observations and provides reliable values of effective reflectivity, Doppler velocity and spectral width. The proposed method is freely available on the web and features a noise removal based on recognition of the most significant peak. A dynamic dealiasing routine allows observations even if the Nyquist velocity range is exceeded. Collocated observations over 115 days of a MRR and a pulsed 35.2 GHz MIRA35 cloud radar show a very high agreement for the proposed method for snow, if reflectivities are larger than â5 dBz. The overall sensitivity is increased to â14 and â8 dBz, depending on range. The proposed method exploits the full potential of MRR's hardware and substantially enhances the use of Micro Rain Radar for studies of solid precipitation
Marine and terrestrial influences on ice nucleating particles during continuous springtime measurements in an Arctic oilfield location
Aerosols that serve as ice nucleating particles (INPs) have the potential to
modulate cloud microphysical properties and can therefore impact cloud
radiative forcing (CRF) and precipitation formation processes. In remote
regions such as the Arctic, aerosolâcloud interactions are severely
understudied yet may have significant implications for the surface energy
budget and its impact on sea ice and snow surfaces. Further, uncertainties in
model representations of heterogeneous ice nucleation are a significant
hindrance to simulating Arctic mixed-phase cloud processes. We present
results from a campaign called INPOPÂ (Ice Nucleating Particles at Oliktok
Point), which took place at a US Department of Energy Atmospheric Radiation
Measurement (DOE ARM) facility in the northern Alaskan Arctic. Three time-
and size-resolved aerosol impactors were deployed from 1Â March to 31Â May 2017
for offline ice nucleation and chemical analyses and were co-located with
routine measurements of aerosol number and size. The largest particles (i.e.,
â„ 3 ”m or âcoarse modeâ) were the most efficient INPs by
inducing freezing at the warmest temperatures. During periods with snow- and
ice-covered surfaces, coarse mode INP concentrations were very low (maximum
of 6 Ă 10â4 Lâ1 at â15 âC), but higher
concentrations of warm-temperature INPs were observed during late May
(maximum of 2 Ă 10â2 Lâ1 at â15 âC). These
higher concentrations were attributed to air masses originating from over
open Arctic Ocean water and tundra surfaces. To our knowledge, these results
represent the first INP characterization measurements in an Arctic oilfield
location and demonstrate strong influences from mineral and marine sources
despite the relatively high springtime pollution levels. Ultimately, these
results can be used to evaluate the anthropogenic and natural influences on
aerosol composition and Arctic cloud properties.</p
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JOYCE: JĂŒlich Observatory for cloud evolution
The JĂŒlich Observatory for Cloud Evolution (JOYCE), located at Forschungszentrum JĂŒlich in the most western part of Germany, is a recently established platform for cloud research. The main objective of JOYCE is to provide observations, which improve our understanding of the cloudy boundary layer in a midlatitude environment. Continuous and temporally highly resolved measurements that are specifically suited to characterize the diurnal cycle of water vapor, stability, and turbulence in the lower troposphere are performed with a special focus on atmosphereâsurface interaction. In addition, instruments are set up to measure the micro- and macrophysical properties of clouds in detail and how they interact with different boundary layer processes and the large-scale synoptic situation. For this, JOYCE is equipped with an array of state-of-the-art active and passive remote sensing and in situ instruments, which are briefly described in this scientific overview. As an example, a 24-h time series of the evolution of a typical cumulus cloud-topped boundary layer is analyzed with respect to stability, turbulence, and cloud properties. Additionally, we present longer-term statistics, which can be used to elucidate the diurnal cycle of water vapor, drizzle formation through autoconversion, and warm versus cold rain precipitation formation. Both case studies and long-term observations are important for improving the representation of clouds in climate and numerical weather prediction models
The Second ARM Training and Science Application Event : Training the Next Generation of Atmospheric Scientists
Non peer reviewe
The relative impact of cloud condensation nuclei and ice nucleating particle concentrations on phase partitioning in Arctic mixed-phase stratocumulus clouds
This study investigates the interactions between cloud dynamics and aerosols
in idealized large-eddy simulations (LES) of Arctic mixed-phase stratocumulus
clouds (AMPS) observed at Oliktok Point, Alaska, in April 2015. This case was chosen
because it allows the cloud to form in response to radiative cooling
starting from a cloud-free state, rather than requiring the cloud ice and
liquid to adjust to an initial cloudy state. Sensitivity studies are used to
identify whether there are buffering feedbacks that limit the impact of
aerosol perturbations. The results of this study indicate that perturbations
in ice nucleating particles (INPs) dominate over cloud condensation nuclei
(CCN) perturbations; i.e., an equivalent fractional decrease in CCN and INPs
results in an increase in the cloud-top longwave cooling rate, even though
the droplet effective radius increases and the cloud emissivity decreases.
The dominant effect of ice in the simulated mixed-phase cloud is a thinning
rather than a glaciation, causing the mixed-phase clouds to radiate as a
grey body and the radiative properties of the cloud to be more sensitive to
aerosol perturbations. It is demonstrated that allowing prognostic CCN and
INPs causes a layering of the aerosols, with increased concentrations of CCN
above cloud top and increased concentrations of INPs at the base of the
cloud-driven mixed layer. This layering contributes to the maintenance of
the cloud liquid, which drives the dynamics of the cloud system.</p
Airborne observations of Arctic air mass transformations during the HALO-(AC)3 campaign
The HALO-(AC)3 campaign was conducted in March and April 2022
to investigate warm air intrusions into the Arctic and marine cold air outbreaks. In
coordinated flights over the Arctic, the High Altitude and Long Range Research Aircraft
(HALO), equipped with a remote sensing payload and dropsondes, investigated these
air mass transformations together with the research aircraft Polar 5 and Polar 6. In
this report, we give an overview about the research flights and preliminary results from
projects, which are carried out by employees of the Leipzig Institute for Meteorology
(LIM).Die HALO-(AC)3 Kampagne wurde im MĂ€rz und April 2022
durchgefĂŒhrt, umWarmlufteinbrĂŒche in die Arktis und marine KaltluftausbrĂŒche zu untersuchen.
Das 'High Altitude and Long Range Research Aircraft' (HALO), ausgestattet
mit Instrumenten zur Fernerkundung und Standardmeteorologiesonden, untersuchte
zusammen mit den Forschungsflugzeugen Polar 5 und Polar 6, in koordinierten FlĂŒgen
ĂŒber der Arktis, diese VerĂ€nderungen der Luftmassen. In diesem Bericht wird eine
Ăbersicht ĂŒber die durchgefĂŒhrten ForschungsflĂŒge gegeben und Forschungsprojekte
werden vorgestellt, welche von Mitarbeitern des Leipziger Instituts fĂŒr Meteorologie
(LIM) durchgefĂŒhrt werden
Introducing the Video In Situ Snowfall Sensor (VISSS)
The open-source Video In Situ Snowfall Sensor (VISSS) is introduced as a novel instrument for the characterization of particle shape and size in snowfall. The VISSS consists of two cameras with LED backlights and telecentric lenses that allow accurate sizing and combine a large observation volume with relatively high pixel resolution and a design that limits wind disturbance. VISSS data products include various particle properties such as maximum extent, cross-sectional area, perimeter, complexity, and sedimentation velocity. Initial analysis shows that the VISSS provides robust statistics based on up to 10â000 unique particle observations per minute. Comparison of the VISSS with the collocated PIP (Precipitation Imaging Package) and Parsivel instruments at HyytiĂ€lĂ€, Finland, shows excellent agreement with the Parsivel but reveals some differences for the PIP that are likely related to PIP data processing and limitations of the PIP with respect to observing smaller particles. The open-source nature of the VISSS hardware plans, data acquisition software, and data processing libraries invites the community to contribute to the development of the instrument, which has many potential applications in atmospheric science and beyond.</p
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The influence of local oil exploration and regional wildfires on summer 2015 aerosol over the North Slope of Alaska
Here, the Arctic is warming at an alarming rate, yet the processes that contribute to the enhanced warming are not well understood. Arctic aerosols have been targeted in studies for decades due to their consequential impacts on the energy budget, both directly and indirectly through their ability to modulate cloud microphysics. Even with the breadth of knowledge afforded from these previous studies, aerosols and their effects remain poorly quantified, especially in the rapidly changing Arctic. Additionally, many previous studies involved use of ground-based measurements, and due to the frequent stratified nature of the Arctic atmosphere, brings into question the representativeness of these datasets aloft. Here, we report on airborne observations from the US Department of Energy Atmospheric Radiation Measurement (ARM) program's Fifth Airborne Carbon Measurements (ACME-V) field campaign along the North Slope of Alaska during the summer of 2015. Contrary to previous evidence that the Alaskan Arctic summertime air is relatively pristine, we show how local oil extraction activities, 2015's central Alaskan wildfires, and, to a lesser extent, long-range transport introduce aerosols and trace gases higher in concentration than previously reported in Arctic haze measurements to the North Slope. Although these sources were either episodic or localized, they serve as abundant aerosol sources that have the potential to impact a larger spatial scale after emission
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Marine and terrestrial influences on ice nucleating particles during continuous springtime measurements in an Arctic oilfield location
Aerosols that serve as ice nucleating particles (INPs) have the potential to modulate cloud microphysical properties and can therefore impact cloud radiative forcing (CRF) and precipitation formation processes. In remote regions such as the Arctic, aerosolâcloud interactions are severely understudied yet may have significant implications for the surface energy budget and its impact on sea ice and snow surfaces. Further, uncertainties in model representations of heterogeneous ice nucleation are a significant hindrance to simulating Arctic mixed-phase cloud processes. We present results from a campaign called INPOP (Ice Nucleating Particles at Oliktok Point), which took place at a US Department of Energy Atmospheric Radiation Measurement (DOE ARM) facility in the northern Alaskan Arctic. Three time- and size-resolved aerosol impactors were deployed from 1 March to 31 May 2017 for offline ice nucleation and chemical analyses and were co-located with routine measurements of aerosol number and size. The largest particles (i.e., â„â3â”m or âcoarse modeâ) were the most efficient INPs by inducing freezing at the warmest temperatures. During periods with snow- and ice-covered surfaces, coarse mode INP concentrations were very low (maximum of 6âĂâ10â4âLâ1 at â15ââC), but higher concentrations of warm-temperature INPs were observed during late May (maximum of 2âĂâ10â2âLâ1 at â15ââC). These higher concentrations were attributed to air masses originating from over open Arctic Ocean water and tundra surfaces. To our knowledge, these results represent the first INP characterization measurements in an Arctic oilfield location and demonstrate strong influences from mineral and marine sources despite the relatively high springtime pollution levels. Ultimately, these results can be used to evaluate the anthropogenic and natural influences on aerosol composition and Arctic cloud properties