scholarly journals Microphysical process of precipitating hydrometeors from warm-front mid-level stratiform clouds revealed by ground-based lidar observations

2021 ◽  
Vol 21 (23) ◽  
pp. 17649-17664
Author(s):  
Yang Yi ◽  
Fan Yi ◽  
Fuchao Liu ◽  
Yunpeng Zhang ◽  
Changming Yu ◽  
...  
Keyword(s):  
Liquid Water ◽  
Dense Layer ◽  
Depolarization Ratio ◽  
Microphysical Process ◽  
Light Rain ◽  
Bright Band ◽  
Stratiform Clouds ◽  
The Hours ◽  
Ground Based Lidar ◽  
Water Values

Abstract. Mid-level stratiform precipitations during the passage of warm fronts were detailedly observed on two occasions (light and moderate rain) by a 355 nm polarization lidar and water vapor Raman lidar, both equipped with waterproof transparent roof windows. The hours-long precipitation streaks shown in the lidar signal (X) and volume depolarization ratio (δv) reveal some ubiquitous features of the microphysical process of precipitating hydrometeors. We find that for the light-rain case precipitation that reaches the surface begins as ice-phase-dominant hydrometeors that fall out of a shallow liquid cloud layer at altitudes above the 0 ∘C isotherm level, and the depolarization ratio magnitude of falling hydrometeors increases from the liquid-water values (δv<0.09) to the ice/snow values (δv>0.20) during the first 100–200 m of their descent. Subsequently, the falling hydrometeors yield a dense layer with an ice/snow bright band occurring above and a liquid-water bright band occurring below (separated by a lidar dark band) as a result of crossing the 0 ∘C level. The ice/snow bright band might be a manifestation of local hydrometeor accumulation. Most falling raindrops shrink or vanish in the liquid-water bright band due to evaporation, whereas a few large raindrops fall out of the layer. We also find that a prominent δv peak (0.10–0.40) always occurs at an altitude of approximately 0.6 km when precipitation reaches the surface, reflecting the collision–coalescence growth of falling large raindrops and their subsequent spontaneous breakup. The microphysical process (at ice-bright-band altitudes and below) of moderate rain resembles that of the light-rain case, but more large-sized hydrometeors are involved.

scholarly journals Microphysical process of precipitating hydrometeors from warm-front mid-level stratiform clouds revealed by ground-based lidar observations

2021 ◽  
Author(s):  
Yang Yi ◽  
Fan Yi ◽  
Fuchao Liu ◽  
Yunpeng Zhang ◽  
Changming Yu ◽  
...  
Keyword(s):  
Liquid Water ◽  
Supercooled Liquid ◽  
Dense Layer ◽  
Microphysical Process ◽  
Light Rain ◽  
Bright Band ◽  
Surface Rainfall ◽  
Warm Front ◽  
Stratiform Clouds ◽  
Ground Based Lidar

Abstract. Mid-level stratiform precipitations during the passage of warm front were detailedly observed on two occasions (light and moderate rain) by a 355-nm polarization lidar and water-vapor Raman lidar, both equipped with waterproof transparent roof windows. The hours-long precipitation streaks shown in the lidar signal (X) and volume depolarization ratio (δv) reveal some ubiquitous features of the microphysical process of precipitating hydrometeors. We find that for the light rain case, surface rainfall begins as supercooled liquid-drop-dominated hydrometeors fall out of their liquid parent cloud at altitudes above the 0 °C level, and most liquid drops quickly freeze into ice particles (δv > 0.25) during the first 100–200 m of their descent, where humid aerosol particles exist. Subsequently, the falling hydrometeors yield a dense layer with an ice/snow bright band occurring above and a liquid-water bright band occurring below (separated by a lidar dark band) as a result of crossing the 0 °C level. The ice/snow bright band might be a manifestation of local hydrometeor accumulation. Most falling raindrops shrink or vanish in the liquid-water bright band due to evaporation, whereas a few large raindrops fall out of the layer. We also find that a prominent depolarization δv peak (0.10–0.35) always occurs at an altitude of approximately 0.6 km during surface rainfall, reflecting the collision-coalescence growth of falling large raindrops and their subsequent spontaneous breakup. The microphysical process (at ice-bright-band altitudes and below) of moderate rain resembles that of the light rain case, but more large-sized hydrometeors are involved.

Depolarization ratio studies on liquid water

1973 ◽  
Vol 59 (4) ◽  
pp. 2132-2139 ◽  
Author(s):  
K. Cunningham ◽  
P. A. Lyons
Keyword(s):  
Liquid Water ◽  
Depolarization Ratio

scholarly journals A new classification of satellite derived liquid water cloud regimes at cloud scale

2019 ◽  
Author(s):  
Claudia Unglaub ◽  
Karoline Block ◽  
Johannes Mülmenstädt ◽  
Odran Sourdeval ◽  
Johannes Quaas
Keyword(s):  
Liquid Water ◽  
Smooth Transition ◽  
Cloud Base ◽  
Cloud Parameters ◽  
Stratiform Clouds ◽  
Inhomogeneity Parameter ◽  
Water Cloud ◽  
Cloud Regimes ◽  
Cloud Base Height

Abstract. Clouds are highly variable in time and space affecting climate sensitivity and climate change. To study and distinguish the different influences of clouds on the climate system it is useful to separate clouds into individual cloud regimes. In this work we present a new cloud classification for liquid water clouds at cloud scale defined using cloud parameters retrieved from combined satellite measurements from CloudSat and CALIPSO. The idea is that cloud heterogeneity is a measure that allows to distinguish cumuliform and stratiform clouds, and cloud base height a measure to distinguish cloud altitude. The approach makes use of a newly-developed cloud-base height retrieval. Using three cloud base height intervals and two intervals of cloud top variability as an inhomogeneity parameter provides six new liquid cloud classes. The results show a smooth transition between marine and continental clouds as well as between stratiform and cumuliform clouds in different latitudes at the high spatial resolution of about 20 km. Analyzing the micro- and macrophysical cloud parameters from collocated combined MODIS, CloudSat and CALIPSO retrievals shows distinct characteristics for each cloud regimes that are in agreement with expectation and literature. This demonstrates the usefulness of the classification.

scholarly journals Corrigendum to "Microphysical Process Rates and Global Aerosol-Cloud Interactions" published in Atmos. Chem. Phys., 13, 9855–9867, 2013

2014 ◽  
Vol 14 (17) ◽  
pp. 9099-9103 ◽  
Author(s):  
A. Gettelman ◽  
H. Morrison ◽  
C. R. Terai ◽  
R. Wood
Keyword(s):  
Steady State ◽  
Liquid Water ◽  
Chem Phys ◽  
Global Model ◽  
State Model ◽  
Liquid Water Path ◽  
Water Path ◽  
Microphysical Process ◽  
Steady State Model ◽  
Aerosol Cloud Interactions

Abstract. A mistake swapped process rates between autoconversion and accretion in global model solutions. Revised figures are presented. The accretion to autoconversion ratio in the model does increase with Liquid Water Path (LWP) as in the steady state model but biases remain. Simulated autoconversion rates are too high. Adjusting process rates following the steady state model ideas leads to an improvement in process rates. The main conclusion is unaffected.

scholarly journals Radiative–Dynamical Feedbacks in Low Liquid Water Path Stratiform Clouds

2012 ◽  
Vol 69 (5) ◽  
pp. 1498-1512 ◽  
Author(s):  
Jonathan L. Petters ◽  
Jerry Y. Harrington ◽  
Eugene E. Clothiaux
Keyword(s):  
Liquid Water ◽  
Cloud Layer ◽  
Flux Divergence ◽  
Liquid Water Path ◽  
Stratiform Cloud ◽  
Water Path ◽  
Droplet Concentration ◽  
Cloud Dynamics ◽  
Stratiform Clouds ◽  
Cloud Evolution

Abstract When stratiform-cloud-integrated radiative flux divergence (heating) is dependent on liquid water path (LWP) and droplet concentration Nd, feedbacks between cloud dynamics and this heating can exist. These feedbacks can be particularly strong for low LWP stratiform clouds, in which cloud-integrated longwave cooling is sensitive to LWP and Nd. Large-eddy simulations reveal that these radiative–dynamical feedbacks can substantially modify low LWP stratiform cloud evolution when Nd is perturbed. At night, more rapid initial evaporation of the cloud layer occurs when Nd is high, leading to more cloud breaks and lower LWP values that both result in less total cloud longwave cooling. Weakened circulations result from this reduced longwave cooling and entrainment drying is able to counteract cloud growth. When Nd is low, the cloud layer is better maintained because cloud longwave cooling is still relatively strong. During the day, the addition of shortwave warming leads to reduced LWP for all values of Nd and, consequently, further reduced longwave cooling and weakened circulations. For high Nd, these reductions are such that the cloud layer cannot be maintained. For lower Nd, the reductions are smaller and the cloud layer thins but does not dissipate. These results suggest that low LWP cloud layers are more tenuous when Nd is high and are more prone to dissipating during the day. Comparison with other studies suggests the modeled low LWP cloud response may be sensitive to the initial thermodynamic profile and model configuration.

Acidic and related constituents in liquid water stratiform clouds

1984 ◽  
Vol 89 (D1) ◽  
pp. 1447 ◽  
Author(s):  
P. H. Daum ◽  
S. E. Schwartz ◽  
L. Newman
Keyword(s):  
Liquid Water ◽  
Stratiform Clouds

scholarly journals The Potential Use of the Linear Depolarization Ratio to Distinguish between Convective and Stratiform Rainfall to Improve Radar Rain-Rate Estimates

2017 ◽  
Vol 56 (11) ◽  
pp. 2927-2940 ◽  
Author(s):  
Caroline Sandford ◽  
Anthony Illingworth ◽  
Robert Thompson
Keyword(s):  
Degrees Of Freedom ◽  
Depolarization Ratio ◽  
Convective Storms ◽  
Bright Band ◽  
Precipitation Estimates ◽  
Linear Depolarization Ratio ◽  
Radar Rain Rate ◽  
Quantitative Precipitation Estimates ◽  
Rain Rates ◽  
Peak Value

AbstractA major source of errors in radar-derived quantitative precipitation estimates is the inhomogeneous nature of the vertical reflectivity profile (VPR). Operational radars generally scan in azimuth at constant elevation (PPI mode) and provide limited VPR information, so predetermined VPR shapes with limited degrees of freedom are needed to correct for the VPR in real time. Typical stratiform VPRs have a sharp peak below the 0° isotherm, known as the “bright band,” caused by the presence of large melting snowflakes, but this feature is not present in convective cores where the melting ice is in the form of graupel or compact ice. Inappropriate correction assuming a brightband VPR can lead to underestimation of rain rates, with particular impacts in intense convective storms. This paper proposes the use of high values of linear depolarization ratio (LDR) measurements to confirm the presence of large melting snowflakes and lower values for melting graupel or high-density ice as a prerequisite to selecting a suitable profile shape for VPR correction. Using a climatologically representative dataset of short-range, high-resolution C-band vertical profiles, the peak value of the LDR in the melting layer is shown to have robust skill in identifying VPRs without bright band, with the “best” performance at a threshold of −20 dB. Further work is proposed to apply this result to improving corrections for VPR at longer range, where the limited effect of beam broadening on LDR peaks could provide advantages over other available methods.

Stratospheric Australian fire smoke layers over Punta Arenas, Chile, measured by ground-based lidar and AEOLUS

2020 ◽  
Author(s):  
Kevin Ohneiser ◽  
Holger Baars ◽  
Cristofer Jimenez ◽  
Johannes Bühl ◽  
Patric Seifert ◽  
...  
Keyword(s):  
Optical Properties ◽  
Southern Hemisphere ◽  
Lower Stratosphere ◽  
Depolarization Ratio ◽  
Upper Troposphere ◽  
Fire Smoke ◽  
First Results ◽  
Linear Depolarization Ratio ◽  
Ground Based Lidar ◽  
Depolarization Ratios

&lt;p&gt;Exceptionally strong wildfire activity in Australia in summer 2019-2020 triggered the evolution of pyrocumulonimbus clouds, releasing enormous amounts of fire smoke into the upper troposphere and lower stratosphere region of the usually very clean southern hemisphere. Measurements at the lidar site of Punta Arenas (53&amp;#176;S), Chile, show that the first stratospheric smoke layers arrived over Punta Arenas at 6 Jan 2020.&lt;/p&gt;&lt;p&gt;First results show striking similarities to a record-breaking event of stratospheric smoke layers from wildfires in Canada in 2017 (Baars et al., ACP 2019). At Punta Arenas, lidar ratios reach values of 45-50&amp;#160;sr at 355&amp;#160;nm, and 60-65&amp;#160;sr at 532&amp;#160;nm wavelength. Particle linear depolarization ratios reach values of 19% at 355&amp;#160;nm, and 15% at 532&amp;#160;nm wavelength.&lt;/p&gt;&lt;p&gt;Aeolus is able to detect these intense layers of stratospheric smoke in the southern hemisphere as well. In this contribution, we will discuss our findings of extensive and intensive smoke optical properties over Punta Arenas to the related Aeolus aerosol spin off products of nearby overpasses. Especially the particle linear depolarization ratio at 355 nm are of relevance as AEOLUS is only able to measure the co-polarized 355&amp;#160;nm signal.&lt;/p&gt;

Evaluation of local weather observations as predictors of fog and low-level stratiform clouds at the airport of Odessa

2020 ◽  
Author(s):  
Inna Khomenko ◽  
Oleksii Hustenko
Keyword(s):  
Relative Humidity ◽  
Weather Conditions ◽  
Stratiform Cloud ◽  
Local Conditions ◽  
Low Level ◽  
Weather Observations ◽  
Stratiform Clouds ◽  
Diurnal Distribution ◽  
The Hours ◽  
Radiation Fogs

&lt;p&gt;Fog that limit visibility and low-level stratiform clouds represent a significant hazard to aviation especially during takeoff and landing, and also low-level flying of aircrafts, because accidents often occur in reduced visibility conditions and low clouds. Therefore, forecasting fog and low ceilings is one of the most important, but at the same time the most difficult issue, because both phenomena strongly depend on local conditions and unsteady in both time and space. So weather observations can be used for statistical dependencies of fog/&amp;#160;low-level stratiform cloud characteristics on numerical model outputs.&lt;/p&gt;&lt;p&gt;To study fog and low-level stratiform clouds event characteristics occurring at the airport of Odessa, Ukraine, half hourly observations in the period of 2010-2018 are used. Applying a statistical approach annual, seasonal and diurnal distribution of fog and low stratus and their frequency distribution associated with various meteorological parameters are obtained.&lt;/p&gt;&lt;p&gt;The monthly distributions of low-level stratiform clouds reveal maximum occurrence frequencies in November and January, and fog most frequently occurs in December. No significant diurnal cycle of stratiform cloud occurrence is discovered, as opposed to fog for which the highest frequency is observed in the hours before sunrise, while when the day sets in, frequencies are declining and increasing at night.&lt;/p&gt;&lt;p&gt;Fog and low-level stratiform clouds have the same distribution in duration and the mean event duration is 4.5&amp;#160;h while 55% of the events lasted 2 h or less. The most long-lived fog and stratiform clouds can last about 4 days during the December-January period.&lt;/p&gt;&lt;p&gt;Occurrence of fog and stratiform clouds as function of temperature and relative humidity reveals a close statistical relationship, especially for fog events. More than 33% of all fogs are observed at temperatures of 0&amp;#176;C to 6&amp;#176;C and 96-100% relative humidity, the most frequencies of low-level clouds (13%) occur in the same temperature interval, but at lower values of relative humidity (91-95%).&lt;/p&gt;&lt;p&gt;Regarding fog density 75% of the events have minimum visibility lower than 400 m, which indicates the severity of the problem, because, despite the season and type of fog, they are usually quite intense and dense.&lt;/p&gt;&lt;p&gt;In all seasons of the year, the highest frequency of low-level stratiform clouds is in interval of 3...4&amp;#160;m/s, excluding summer, when most often such cloud is registered at higher speeds. The wind directions associated with low-level stratiform clouds are, as a rule, northern and eastern ones, which meant that forming stratiform clouds is also related to cyclonic activity.&lt;/p&gt;&lt;p&gt;Fogs, on the contrary, most often in all seasons, except winter, are formed at calm, meaning that radiation fogs are the most common type in the Odessa airport. In winter fogs are most commonly associated with northern and easterly winds; in all other seasons the southern wind is the most frequent.&lt;/p&gt;&lt;p&gt;On this basis, a relationship between the weather conditions near the surface and occurrence of fog and low-level stratiform clouds can be found.&lt;/p&gt;

Sign in / Sign up

Export Citation Format

Share Document