scholarly journals In-situ cloud ground based measurements in Finnish sub-Arctic: Intercomparison of three cloud spectrometers

2020 ◽  
Author(s):  
Konstantinos-Matthaios Doulgeris ◽  
Mika Komppula ◽  
Sami Romakkaniemi ◽  
Antti-Pekka Hyvärinen ◽  
Veli-Matti Kerminen ◽  
...  
Keyword(s):  
Water Content ◽  
Liquid Water ◽  
Wind Direction ◽  
Liquid Water Content ◽  
Measured Parameter ◽  
Effective Diameter ◽  
Rotating Platform ◽  
Cloud Droplets ◽  
Median Volume

Abstract. Continuous, semi-long term, ground based, in-situ cloud measurements were conducted during the Pallas Cloud Experiment (PaCE) in 2013. The measurements were carried out in Finnish sub-Arctic region at Sammaltunturi station (67°58'N, 24°07'E, and 560 m a.s.l.), the part of Pallas Atmosphere – Ecosystem Supersite and Global Atmosphere Watch (GAW) programme. The main motivation of the campaign was to conduct in-situ cloud measurements with three different cloud spectrometer probes and perform an evaluation of their ground based setups. Therefore, we mutually compared the performance of the Cloud and Aerosol Spectrometer (CAS), the Cloud Droplet Probe (CDP) and the Forward Scattering Spectrometer Probe (FSSP-100), (DMT, Boulder, CO, USA). We investigated how different meteorological parameters affect each instrument operation and quantified possible biases and discrepancies of different microphysical cloud properties. Based on obtained results we suggested limitations for further use of the instruments in campaigns where focus is on investigating aerosol cloud interactions. Measurements in this study were made by Finnish Meteorological Institute owned instruments and results concern their operation in sub-Arctic conditions with frequently occurring super-cooled clouds. Measured parameter from each instrument was the size distribution and additionally we derived the number concentration, the effective diameter, the median volume diameter and the liquid water content. A complete intercomparison between the CAS probe and the FSSP-100 and additionally between the FSSP-100 and the CDP probe was made and presented. Unfortunately, there was not sufficient amount of common data to compare all three probes together due to operational problems of the CDP ground setup in sub-zero conditions. The CAS probe that was fixed to one direction lost significant number of cloud droplets when the wind direction was out of wind iso axial conditions in comparison with the FSSP-100 and the CDP which were both placed on a rotating platform. We revealed that CAS and FSSP-100 had good agreement in deriving sizing parameters (effective diameter and median volume diameter from 5 to 35 µm) even though CAS was losing a significant amount of cloud droplets. The most sensitive derived parameter was liquid water content which was strongly connected to the wind direction and temperature.

scholarly journals In situ cloud ground-based measurements in the Finnish sub-Arctic: intercomparison of three cloud spectrometer setups

2020 ◽  
Vol 13 (9) ◽  
pp. 5129-5147 ◽  
Author(s):  
Konstantinos-Matthaios Doulgeris ◽  
Mika Komppula ◽  
Sami Romakkaniemi ◽  
Antti-Pekka Hyvärinen ◽  
Veli-Matti Kerminen ◽  
...  
Keyword(s):  
Water Content ◽  
Liquid Water ◽  
Wind Direction ◽  
Liquid Water Content ◽  
Measured Parameter ◽  
Effective Diameter ◽  
Rotating Platform ◽  
Cloud Droplets ◽  
Median Volume

Abstract. Continuous, semi-long-term, ground-based in situ cloud measurements were conducted during the Pallas Cloud Experiment (PaCE) in 2013. The measurements were carried out in Finnish sub-Arctic region at Sammaltunturi station (67∘58′ N, 24∘07′ E; 560 m a.s.l.), part of Pallas Atmosphere – Ecosystem Supersite and Global Atmosphere Watch (GAW) program. The main motivation of the campaign was to conduct in situ cloud measurements with three different cloud spectrometer probes and perform an evaluation of their ground-based setups. Therefore, we mutually compared the performance of the cloud and aerosol spectrometer (CAS), the cloud droplet probe (CDP) and the forward-scattering spectrometer probe (FSSP-100) (DMT; Boulder, CO, USA). We investigated how different meteorological parameters affect each instrument's ground-based setup operation and quantified possible biases and discrepancies of different microphysical cloud properties. Based on the obtained results we suggested limitations for further use of the instrument setups in campaigns where the focus is on investigating aerosol–cloud interactions. Measurements in this study were made by instruments owned by the Finnish Meteorological Institute and results concern their operation in sub-Arctic conditions with frequently occurring supercooled clouds. The measured parameter from each instrument was the size distribution, and additionally we derived the number concentration, the effective diameter, the median volume diameter and the liquid water content. A complete intercomparison between the CAS probe and the FSSP-100 ground setups and additionally between the FSSP-100 and the CDP probe ground setups was made and presented. Unfortunately, there was not a sufficient amount of common data to compare all three probes together due to operational problems of the CDP ground setup in sub-zero conditions. The CAS probe that was fixed to one direction lost a significant number of cloud droplets when the wind direction was out of wind iso-axial conditions in comparison with the FSSP-100 and the CDP, which were both placed on a rotating platform. We revealed that CAS and FSSP-100 had good agreement in deriving sizing parameters (effective diameter and median volume diameter from 5 to 35 µm) even though CAS was losing a significant amount of cloud droplets. The most sensitive derived parameter was liquid water content, which was strongly connected to the wind direction and temperature.

In situ ground based measurements of low level clouds during 10 years of Pallas cloud experiments.

2020 ◽  
Author(s):  
Konstantinos Doulgeris ◽  
David Brus
Keyword(s):  
Water Content ◽  
Liquid Water ◽  
Meteorological Data ◽  
Liquid Water Content ◽  
Data Set ◽  
Radiative Balance ◽  
Low Level ◽  
Major Factors

<p>Clouds and their interaction with aerosols are considered one of the major factors that are connected with uncertainties in predictions of climate change and are highly associated with earth radiative balance. Semi long term in-situ measurements of Arctic low-level clouds have been conducted during last 10 year (2009 - 2019) autumns at Sammaltunturi station (67◦58´N, 24◦07´E, and 560 m a.s.l.), the part of Pallas Atmosphere - Ecosystem Supersite and Global Atmosphere Watch (GAW) programme. During these years a unique data set of continuous and detailed ground-based cloud observations over the sub-Arctic area was obtained. The in-situ cloud measurements were made using two cloud probes that were installed on the roof of the station: the Cloud, Aerosol and Precipitation Spectrometer probe (CAPS) and the Forward Scattering Spectrometer Probe<strong> (</strong>FSSP<strong>)</strong>, both made by droplet measurement technologies (DMT, Longmont, CO, USA). CAPS in­cludes three instruments: the Cloud Imaging Probe (CIP, 12.5 μm-1.55 mm), the Cloud and Aerosol Spectrometer (CAS-DPOL, 0.51-50 μm) with depolarization feature and the Hotwire Liquid Water Content Sensor (Hotwire LWC, 0 - 3 g/m<sup>3</sup>). Vaisala FD12P weather sensor was used to measure all the meteorological data. The essential cloud microphysical parameters we investigated during this work were the size distributions, the total number concentrations, the effective radius of cloud droplets and the cloud liquid water content. The year to year comparison and correlations among semi long term in situ cloud measurements and meteorology are presented.</p>

A New Analytical Expression of Overall Collision Efficiency for the Water Droplet Impinging on a Cylinder

2013 ◽  
Vol 392 ◽  
pp. 90-94
Author(s):  
Ling Chen ◽  
Rui Liu ◽  
Yong Xing Cao
Keyword(s):  
Numerical Calculation ◽  
Water Content ◽  
Numerical Computation ◽  
Liquid Water ◽  
Water Droplet ◽  
Liquid Water Content ◽  
Collision Efficiency ◽  
Analytical Expression ◽  
Median Volume ◽  
Calculation Results

The ice amount accreting on the rotating multi-cylinders can be used to obtain the liquid water content (LWC) and the median volume diameter of water droplet (MVD) based on cylindrical icing model. In this model, the overall collision efficiency is usually calculated by Finstads (φ100) and Langmuirs formulations (φ<100). But this combined expression doesnt agree well with the numerical calculation in some case. This paper gives a new expression based on a large number of numerical calculation results, and this expression agrees better with the numerical computation than existing expression.

scholarly journals Gamma Distribution Parameters for Cloud Drop Distributions from Multicylinder Measurements

2014 ◽  
Vol 53 (6) ◽  
pp. 1606-1617 ◽  
Author(s):  
Kathleen F. Jones ◽  
Gregory Thompson ◽  
Keran J. Claffey ◽  
Eric P. Kelsey
Keyword(s):  
Water Content ◽  
Gamma Distribution ◽  
Liquid Water ◽  
Liquid Water Content ◽  
Cloud Microphysics ◽  
Drop Diameter ◽  
Cloud Models ◽  
Median Volume ◽  
Drop Number ◽  
Mount Washington

AbstractThe liquid water content and drop diameters in supercooled clouds have been measured since the 1940s at the summit of Mount Washington in New Hampshire using a rotating multicylinder. Many of the cloud microphysics models in the Weather Research and Forecasting Model (WRF) assume a gamma distribution for cloud drops. In this paper, years of multicylinder data are reanalyzed to determine the best-fitting gamma or monodisperse distribution to compare with parameters in the WRF cloud models. The single-moment cloud schemes specify a predetermined and constant drop number density in clouds, which leads to a fixed relationship between the median volume drop diameter and the liquid water content. The Mount Washington drop number densities are generally larger and best-fit distributions are generally narrower than is typically assumed in WRF.

In situ estimation of effective liquid water content on a wind turbine using a thermal based sensor

2021 ◽  
Vol 184 ◽  
pp. 103235
Author(s):  
Patrice Roberge ◽  
Jean Lemay ◽  
Jean Ruel ◽  
André Bégin-Drolet
Keyword(s):  
Wind Turbine ◽  
Water Content ◽  
Liquid Water ◽  
Liquid Water Content

In situ measurements of liquid water content profiles in midlatitude stratiform clouds

2007 ◽  
Vol 133 (628) ◽  
pp. 1693-1699 ◽  
Author(s):  
A. V. Korolev ◽  
G. A. Isaac ◽  
J. W. Strapp ◽  
S. G. Cober ◽  
H. W. Barker
Keyword(s):  
Water Content ◽  
Liquid Water ◽  
Liquid Water Content ◽  
In Situ Measurements ◽  
Stratiform Clouds

scholarly journals Characterizing and Predicting Marine Fog Offshore Newfoundland and Labrador

2020 ◽  
Vol 35 (2) ◽  
pp. 347-365 ◽  
Author(s):  
George A. Isaac ◽  
Terry Bullock ◽  
Jennifer Beale ◽  
Steven Beale
Keyword(s):  
Water Content ◽  
Liquid Water ◽  
Newfoundland And Labrador ◽  
Liquid Water Content ◽  
Time Frame ◽  
Microphysical Properties ◽  
Droplet Concentration ◽  
Air Temperatures ◽  
Summer Time

Abstract As several review papers have concluded, marine fog is imperfectly characterized, and quantitative visibility forecasts are difficult to produce accurately. Some unique measurements have been made offshore Newfoundland and Labrador of the climatology of occurrence and the microphysical characteristics of marine, or open-ocean, fog. Based on measurements made at an offshore installation over 21 years, the percent of time with visibilities less than 0.5 n mi or approximately 1 km (1 n mi ≈ 1.85 km) reaches 45% in July, with a low of about 5% during the winter. The occurrence of fog is mainly due to warm air advection, with the highest frequency occurring with wind directions from over the warm Gulf Stream, and with air temperatures about 2°C warmer than the sea surface temperature. There is no diurnal variation in the frequency of occurrence of fog. The microphysical properties of the fog have been documented in the summer time frame, with over 550 h of in situ measurements made offshore with fog liquid water content greater than 0.005 g m−3. The fog droplet number concentration spectra peaks near 6 μm, with a secondary peak near 25–40 μm, which typically contains most of the liquid water content. The median droplet concentration is approximately 70–100 cm−3. The microphysical spectra have been used to develop a new NWP visibility parameterization scheme, and this scheme is compared with other parameterizations currently in use.

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