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

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>

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

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.

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 A Technique for Estimating Liquid Droplet Diameter and Liquid Water Content in Stratocumulus Clouds Using Radar and Lidar Measurements

2020 ◽  
Vol 37 (11) ◽  
pp. 2145-2161
Author(s):  
Jothiram Vivekanandan ◽  
Virendra P. Ghate ◽  
Jorgen B. Jensen ◽  
Scott M. Ellis ◽  
M. Christian Schwartz
Keyword(s):  
Water Content ◽  
Liquid Water ◽  
Droplet Diameter ◽  
Particle Diameter ◽  
Liquid Water Content ◽  
Lidar Measurements ◽  
Stratocumulus Clouds ◽  
Characteristic Particle ◽  
Lidar Observations

AbstractThis paper describes a technique for estimating the liquid water content (LWC) and a characteristic particle diameter in stratocumulus clouds using radar and lidar observations. The uncertainty in LWC estimate from radar and lidar measurements is significantly reduced once the characteristic particle diameter is known. The technique is independent of the drop size distribution. It is applicable for a broad range of W-band reflectivity Z between −30 and 0 dBZ and all values of lidar backscatter β observations. No partitioning of cloud or drizzle is required on the basis of an arbitrary threshold of Z as in prior studies. A method for estimating droplet diameter and LWC was derived from the electromagnetic simulations of radar and lidar observations. In situ stratocumulus cloud and drizzle probe spectra were input to the electromagnetic simulation. The retrieved droplet diameter and LWC were validated using in situ measurements from the southeastern Pacific Ocean. The retrieval method was applied to radar and lidar measurements from the northeastern Pacific. Uncertainty in the retrieved droplet diameter and LWC that are due to the measurement errors in radar and lidar backscatter measurements are 7% and 14%, respectively. The retrieved LWC was validated using the concurrent G-band radiometer estimates of the liquid water path.

Retrieval of Hydrometeor Profiles in Tropical Cyclones and Convection from Combined Radar and Radiometer Observations

2006 ◽  
Vol 45 (8) ◽  
pp. 1096-1115 ◽  
Author(s):  
Haiyan Jiang ◽  
Edward J. Zipser
Keyword(s):  
Water Content ◽  
Tropical Cyclones ◽  
Liquid Water ◽  
Liquid Water Content ◽  
Retrieval Algorithm ◽  
Large Variability ◽  
Ice Water Content ◽  
Ice Water ◽  
Combined Algorithm

Abstract A retrieval algorithm is described to estimate vertical profiles of precipitation ice water content and liquid water content in tropical cyclones and convection over ocean from combined spaceborne radar and radiometer measurements. In the algorithm, the intercept parameter N0s in the exponential particle size distribution for rain, snow, and graupel are adjusted iteratively to minimize the difference between observed brightness temperatures and simulated ones by using a simulated annealing optimization method. Sensitivity tests are performed to understand the effects of the input parameters. The retrieval technique is investigated using the Earth Resources (ER)-2 aircraft Doppler radar and Advanced Microwave Precipitation Radiometer data in tropical cyclones and convection. An indirect validation is performed by comparing the measured and retrieved 50-GHz (independent channel) brightness temperature. The global agreement shows not only the quality of the inversion procedure, but also the consistency of the retrieved parameters with observations. The direct validation of the ice water content retrieval by using the aircraft in situ microphysical measurements indicates that the algorithm can provide reliable ice water content estimates, especially in stratiform regions. In convective regions, the large variability of the microphysical characteristics causes a large uncertainty in the retrieval, although the mean difference between the retrieved ice water content and aircraft-derived ice water content is very small. The ice water content estimated by a radar-only empirical relationship is higher than those retrieved by the combined algorithm and derived by the aircraft in situ observations. The new combined algorithm contains information that should improve ice water content estimates from either radar-only or passive microwave–only measurements. An important caveat for this study is that it concerns precipitation estimates. In this paper, ice and liquid water content should be interpreted as precipitation ice and liquid water content.

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.

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