scholarly journals Contrail formation within cirrus: high-resolution simulations using ICON-LEM

2021 ◽  
Author(s):  
Pooja Verma ◽  
Ulrike Burkhardt
Keyword(s):  
High Resolution ◽  
Water Content ◽  
Survival Rates ◽  
Ice Nucleation ◽  
Ice Crystals ◽  
Cirrus Cloud ◽  
Ice Crystal ◽  
Vortex Phase ◽  
Ice Water Content ◽  
Ice Water

Abstract. Contrail formation within natural cirrus introduces large perturbations in cirrus ice crystal number concentrations leading to modifications in cirrus microphysical and optical properties. The number of contrail ice crystals formed in an aircraft plume depends on the atmospheric state and aircraft and fuel properties. Our aim is to study the impact of pre-existing cirrus on the contrail formation processes. We analyze contrail ice nucleation within cirrus and the survival of contrail ice crystals within the vortex phase and their change due to the presence of cirrus ice crystals within the high-resolution ICON-LEM at a horizontal resolution of 625 m over Germany. We have selected two different synoptic situations sampling a large range of cirrus cloud properties from very thick cirrus connected with a frontal system to very thin cirrus within a high-pressure system. We find that contrail formation within cirrus often leads to increases in cirrus ice crystal numbers by a few orders of magnitude. Pre-existing cirrus has an impact on contrail ice crystal number concentrations only if the cirrus is optically thick. In thick cirrus, contrail ice nucleation rates and ice crystal survival rates within the vortex phase are both increased. The sublimation of the cirrus ice crystals sucked into and subsequently sublimated within the aircraft’s engine leads to an increase in the contrail formation threshold by up to 0.7 K which causes an increase in the number of nucleated contrail ice crystals. This increase can be large at lower flight levels where ambient temperatures are close to the contrail formation threshold temperature and when the ice water content of the pre-existing cirrus cloud is large. During the contrail’s vortex phase the aircraft plume is trapped within the descending vortices in which the decrease in plume relative humidity leads to the sublimation of contrail ice crystals. This contrail ice crystal loss can be modified by the cirrus ice crystals that are mixed into the plume before the start of the vortex phase. In particular, high ice crystal number concentrations and large ice water content of the pre-existing cirrus cloud or low contrail ice crystal numbers are associated with significant increases in the contrail ice crystal survival rates.

scholarly journals Ice Crystal Sizes in High Ice Water Content Clouds. Part II: Statistics of Mass Diameter Percentiles in Tropical Convection Observed during the HAIC/HIWC Project

2017 ◽  
Vol 34 (1) ◽  
pp. 117-136 ◽  
Author(s):  
D. Leroy ◽  
E. Fontaine ◽  
A. Schwarzenboeck ◽  
J. W. Strapp ◽  
A. Korolev ◽  
...  
Keyword(s):  
Water Content ◽  
Ice Crystals ◽  
Ice Crystal ◽  
Potential Threat ◽  
Convective Systems ◽  
Imaging Probes ◽  
Ice Water Content ◽  
The Individual ◽  
Particle Imaging ◽  
Ice Water

AbstractHigh ice water content (IWC) regions in mesoscale convective systems (MCSs) are a potential threat to commercial aviation, as they are suspected to cause in-service engine power-loss events and air data probe malfunctions. To investigate this, the high-altitude ice crystals (HAIC)/high ice water content (HIWC) projects set up a first field campaign in Darwin (Australia) in 2014. The airborne instrumentation was selected to provide the most accurate measurements of both the bulk total water content (TWC), using a specially developed isokinetic evaporator, and the individual ice crystals properties, using particle imaging probes.This study focuses on determining the size ranges of ice crystals responsible for the mass in high IWC regions, defined here as cloud regions with IWC greater than 1.5 g m−3. It is shown that for high IWC areas in most of the encountered MCSs, median mass diameters (MMDs) of ice crystals range from 250 to 500 μm and decrease with increasing TWC and decreasing temperature. At the same time, the mass contribution of the smallest crystals (below 100 μm) remains generally low (below 15%).In contrast, data from two flight missions in a long-lasting quasi-stationary tropical storm reveal that high IWC values can also be associated with MMDs in the range 400–800 μm and peak values of up to 2 mm. Ice crystal images suggest a major growth contribution by vapor deposition (columns, capped columns) even for such larger MMD values.

scholarly journals Retrieving Cloud Ice Water Content Using Millimeter- and Centimeter-Wavelength Radar Polarimetric Observables

2015 ◽  
Vol 54 (3) ◽  
pp. 596-604 ◽  
Author(s):  
Yinghui Lu ◽  
Kültegin Aydin ◽  
Eugene E. Clothiaux ◽  
Johannes Verlinde
Keyword(s):  
Water Content ◽  
Electromagnetic Scattering ◽  
Ice Crystals ◽  
Ice Crystal ◽  
Ice Water Content ◽  
Extensive Collection ◽  
Crystal Type ◽  
Retrieval Errors ◽  
Cloud Ice ◽  
Ice Water

AbstractScattering properties of a large collection of pristine ice crystals at millimeter and centimeter wavelengths are calculated using the generalized multiparticle Mie method. Millimeter- and centimeter-wavelength radar observables are also calculated by employing particle size distributions (PSDs) that ensure the bulk properties (e.g., ice water content and total number concentration) fall within physically realistic ranges. The relationships between radar reflectivity Z and ice water content (IWC) are shown to be sensitive (from one to two orders of magnitude in variability) to the PSDs used and are thus not recommended for IWC retrievals. The relationships between IWC and specific differential phase KDP are less dependent on PSDs. Simple relationships between IWC and KDP at different radar elevation angles and wavelengths are given. If only the general crystal type is known (i.e., planar vs columnar), IWC retrieval errors based on KDP mostly fall within 30%. If more detailed ice crystal type is known, the retrieval errors are reduced to mostly within 10%. These results are similar to earlier reports in the literature but are based on a more extensive collection of model ice crystals and electromagnetic-scattering computations at four wavelengths: X, Ku, Ka, and W bands. The applicability of KDP in retrieving IWC is limited by the measurement accuracy of KDP, which usually requires averaging over several kilometers in range. Given the same noise level, the shorter wavelengths may have relatively smaller fractional errors than the longer wavelengths in KDP-based IWC retrievals and are promising wavelengths for further investigation.

scholarly journals Ice particle sampling from aircraft – influence of the probing position on the ice water content

2018 ◽  
Vol 11 (7) ◽  
pp. 4015-4031 ◽  
Author(s):  
Armin Afchine ◽  
Christian Rolf ◽  
Anja Costa ◽  
Nicole Spelten ◽  
Martin Riese ◽  
...  
Keyword(s):  
Water Content ◽  
Ice Crystals ◽  
Radiative Properties ◽  
Ice Crystal ◽  
Aircraft Wing ◽  
Particle Sampling ◽  
Research Aircraft ◽  
Ice Water Content ◽  
The Mean ◽  
Ice Water

Abstract. The ice water content (IWC) of cirrus clouds is an essential parameter determining their radiative properties and thus is important for climate simulations. Therefore, for a reliable measurement of IWC on board research aircraft, it is important to carefully design the ice crystal sampling and measuring devices. During the ML-CIRRUS field campaign in 2014 with the German Gulfstream GV HALO (High Altitude and Long Range Research Aircraft), IWC was recorded by three closed-path total water together with one gas-phase water instrument. The hygrometers were supplied by inlets mounted on the roof of the aircraft fuselage. Simultaneously, the IWC is determined by a cloud particle spectrometer attached under an aircraft wing. Two more examples of simultaneous IWC measurements by hygrometers and cloud spectrometers are presented, but the inlets of the hygrometers were mounted at the fuselage side (M-55 Geophysica, StratoClim campaign 2017) and bottom (NASA WB57, MacPex campaign 2011). This combination of instruments and inlet positions provides the opportunity to experimentally study the influence of the ice particle sampling position on the IWC with the approach of comparative measurements. As expected from theory and shown by computational fluid dynamics (CFD) calculations, we found that the IWCs provided by the roof inlets deviate from those measured under the aircraft wing. As a result of the inlet position in the shadow zone behind the aircraft cockpit, ice particle populations with mean mass sizes larger than about 25 µm radius are subject to losses, which lead to strongly underestimated IWCs. On the other hand, cloud populations with mean mass sizes smaller than about 12 µm are dominated by particle enrichment and thus overestimated IWCs. In the range of mean mass sizes between 12 and 25 µm, both enrichment and losses of ice crystals can occur, depending on whether the ice crystal mass peak of the size distribution – in these cases bimodal – is on the smaller or larger mass mode. The resulting deviations of the IWC reach factors of up to 10 or even more for losses as well as for enrichment. Since the mean mass size of ice crystals increases with temperature, losses are more pronounced at higher temperatures, while at lower temperatures IWC is more affected by enrichment. In contrast, in the cases where the hygrometer inlets were mounted at the fuselage side or bottom, the agreement of IWCs is most frequently within a factor of 2.5 or better – due to less disturbed ice particle sampling, as expected from theory – independently of the mean ice crystal sizes. The rather large scatter between IWC measurements reflects, for example, cirrus cloud inhomogeneities and instrument uncertainties as well as slight sampling biases which might also occur on the side or bottom of the fuselage and under the wing. However, this scatter is in the range of other studies and represent the current best possible IWC recording on fast-flying aircraft.

scholarly journals Cirrus Cloud Properties as Seen by the CALIPSO Satellite and ECHAM-HAM Global Climate Model

2018 ◽  
Vol 31 (5) ◽  
pp. 1983-2003 ◽  
Author(s):  
B. Gasparini ◽  
A. Meyer ◽  
D. Neubauer ◽  
S. Münch ◽  
U. Lohmann
Keyword(s):  
Water Content ◽  
Cirrus Clouds ◽  
Ice Crystals ◽  
Water Vapor Transport ◽  
Formation Mechanisms ◽  
Ice Crystal ◽  
Extinction Coefficients ◽  
Ice Water Content ◽  
Ice Water

Cirrus clouds impact the planetary energy balance and upper-tropospheric water vapor transport and are therefore relevant for climate. In this study cirrus clouds at temperatures colder than −40°C simulated by the ECHAM–Hamburg Aerosol Module (ECHAM-HAM) general circulation model are compared to Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations ( CALIPSO) satellite data. The model captures the general cloud cover pattern and reproduces the observed median ice water content within a factor of 2, while extinction is overestimated by about a factor of 3 as revealed by temperature-dependent frequency histograms. Two distinct types of cirrus clouds are found: in situ–formed cirrus dominating at temperatures colder than −55°C and liquid-origin cirrus dominating at temperatures warmer than −55°C. The latter cirrus form in anvils of deep convective clouds or by glaciation of mixed-phase clouds, leading to high ice crystal number concentrations. They are associated with extinction coefficients and ice water content of up to 1 km−1 and 0.1 g m−3, respectively, while the in situ–formed cirrus are associated with smaller extinction coefficients and ice water content. In situ–formed cirrus are nucleated either heterogeneously or homogeneously. The simulated homogeneous ice crystals are similar to liquid-origin cirrus, which are associated with high ice crystal number concentrations. On the contrary, heterogeneously nucleated ice crystals appear in smaller number concentrations. However, ice crystal aggregation and depositional growth smooth the differences between several formation mechanisms, making the attribution to a specific ice nucleation mechanism challenging.

scholarly journals Aircraft Observations of Characteristics and Growth of Ice Particles of Two Different Snowfall Clouds in Shanxi Province, China

Atmosphere ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 477
Author(s):  
Qiujuan Feng ◽  
Shengjie Niu ◽  
Tuanjie Hou ◽  
Zhiguo Yue ◽  
Dongdong Shen
Keyword(s):  
Water Content ◽  
Exponential Function ◽  
Liquid Water ◽  
Liquid Water Content ◽  
Ice Crystals ◽  
Ice Crystal ◽  
Ice Particles ◽  
Ice Water Content ◽  
Ice Crystal Habits ◽  
Ice Water

The ice crystal habits, distributions and growth processes in two snowfall cloud cases on 29 November 2009 and 3 March 2012 in northern China were compared and analyzed with aircraft data. The results showed that ice crystal habits were affected by the height of ice clouds. Ice crystals in clouds with cloud top temperatures of −12.6 °C were predominantly needle, plate, dendrite and irregular. When the cloud top temperature was lower than −19.5 °C, plates, dendrites and irregular ice crystals were observed in addition to needles, capped-column crystals were observed in the lower and middle layers of clouds, and column crystals were observed in the upper layer of clouds. The liquid water content of the two snowfall processes was lower than 0.1 g·m–3. Ice particles grew mainly via deposition, riming and aggregation processes. On 29 November, the liquid water content of the stratospheric mixed snowfall cloud was distributed in the lower part of the cloud. The maximum values of particle concentration and ice water content detected by a cloud imaging probe were 187 L–1and 1.05 g·m–3, which were at −8.7 °C, and the ice water content was higher. On 3 March, the liquid water content of snowfall in stratiform clouds was located in the middle layer, and the maximum ice water was low, which was only 0.052 g m–3. The ice water value on 29 November was higher, which was mainly due to the convective zone embedded in the cumulus mixed cloud containing a large number of riming and aggregated snow crystals. Using an exponential function to fit the crystal spectrum of the two snowfall processes, N0 and λ were 109–1011 m–4 and 108–1010 m–4 and 103–104 m–1 and 104 m–1, respectively. Compared with 3 March, N0 on 29 November was larger and the variation range of λ was one more order of magnitude. N0 and λ conformed to a power function distribution. By analyzing the scatter plot of the correlation coefficient and slope, it was found that the exponential function can accurately express the crystal spectrum of snow clouds.

scholarly journals An algorithm to retrieve ice water content profiles in cirrus clouds from the synergy of ground-based lidar and thermal infrared radiometer measurements

2019 ◽  
Vol 12 (3) ◽  
pp. 1545-1568
Author(s):  
Friederike Hemmer ◽  
Laurent C.-Labonnote ◽  
Frédéric Parol ◽  
Gérard Brogniez ◽  
Bahaiddin Damiri ◽  
...  
Keyword(s):  
Water Content ◽  
Correction Factor ◽  
Phase Function ◽  
Extinction Ratio ◽  
Optimal Estimation ◽  
Thermal Infrared ◽  
Cirrus Clouds ◽  
Ice Crystals ◽  
Ice Water Content ◽  
Ice Water

Abstract. The algorithm presented in this paper was developed to retrieve ice water content (IWC) profiles in cirrus clouds. It is based on optimal estimation theory and combines ground-based visible lidar and thermal infrared (TIR) radiometer measurements in a common retrieval framework in order to retrieve profiles of IWC together with a correction factor for the backscatter intensity of cirrus cloud particles. As a first step, we introduce a method to retrieve extinction and IWC profiles in cirrus clouds from the lidar measurements alone and demonstrate the shortcomings of this approach due to the backscatter-to-extinction ambiguity. As a second step, we show that TIR radiances constrain the backscattering of the ice crystals at the visible lidar wavelength by constraining the ice water path (IWP) and hence the IWC, which is linked to the optical properties of the ice crystals via a realistic bulk ice microphysical model. The scattering phase function obtained from the microphysical model is flat around the backscatter direction (i.e., there is no backscatter peak). We show that using this flat backscattering phase function to define the backscatter-to-extinction ratio of the ice crystals in the retrievals with the lidar-only algorithm results in an overestimation of the IWC, which is inconsistent with the TIR radiometer measurements. Hence, a synergy algorithm was developed that combines the attenuated backscatter profiles measured by the lidar and the measurements of TIR radiances in a common optimal estimation framework to retrieve the IWC profile together with a correction factor for the phase function of the bulk ice crystals in the backscattering direction. We show that this approach yields consistent lidar and TIR results. The resulting lidar ratios for cirrus clouds are found to be consistent with previous independent studies.

scholarly journals Determination of ice water content (IWC) in tropical convective clouds from X-band dual-polarization airborne radar

2019 ◽  
Vol 12 (11) ◽  
pp. 5897-5911 ◽  
Author(s):  
Cuong M. Nguyen ◽  
Mengistu Wolde ◽  
Alexei Korolev
Keyword(s):  
Water Content ◽  
Ice Crystals ◽  
Airborne Radar ◽  
Dual Polarization ◽  
Differential Phase ◽  
Convective Clouds ◽  
X Band ◽  
Ice Water Content ◽  
Differential Reflectivity ◽  
Ice Water

Abstract. This paper presents a methodology for ice water content (IWC) retrieval from a dual-polarization side-looking X-band airborne radar. Measured IWC from aircraft in situ probes is weighted by a function of the radar differential reflectivity (Zdr) to reduce the effects of ice crystal shape and orientation on the variation in IWC – specific differential phase (Kdp) joint distribution. A theoretical study indicates that the proposed method, which does not require a knowledge of the particle size distribution (PSD) and number density of ice crystals, is suitable for high-ice-water-content (HIWC) regions in tropical convective clouds. Using datasets collected during the High Altitude Ice Crystals – High Ice Water Content (HAIC-HIWC) international field campaign in Cayenne, French Guiana (2015), it is shown that the proposed method improves the estimation bias by 35 % and increases the correlation by 4 % on average, compared to the method using specific differential phase (Kdp) alone.

scholarly journals A Comparison of Airborne In Situ Cloud Microphysical Measurement with Ground-Based C-Band Radar Observations in Deep Stratiform Regions of African Squall Lines

2015 ◽  
Vol 54 (12) ◽  
pp. 2461-2477 ◽  
Author(s):  
E. Drigeard ◽  
E. Fontaine ◽  
W. Wobrock ◽  
A. Schwarzenböck ◽  
C. Duroure ◽  
...  
Keyword(s):  
Water Content ◽  
Ice Crystals ◽  
Southwestern Part ◽  
Radar Observations ◽  
Squall Lines ◽  
Ice Water Content ◽  
Ice Water ◽  
Reflectivity Factor

AbstractThis study addresses clouds with significant ice water content (IWC) in the stratiform regions downwind of the convective cores of African squall lines in the framework of the French–Indian satellite Megha-Tropiques project, observed in August 2010 next to Niamey (13.5°N, 2°E) in the southwestern part of Niger. The objectives included comparing the IWC–Z reflectivity relationship for precipitation radars in deep stratiform anvils, collocating reflectivity observed from ground radar with the calculated reflectivity from in situ microphysics for all aircraft locations inside the radar range, and interpreting the role of large ice crystals in the reflectivity of centimeter radars through analysis of their microphysical characteristics as ice crystals larger than 5 mm frequently occurred. It was found that, in the range of 20–30 dBZ, IWC and C-band reflectivity are not really correlated. Cloud regions with high IWC caused by important crystal number concentrations can lead to the same reflectivity factor as cloud regions with low IWC formed by a few millimeter-sized ice crystals.

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