An Airborne Remote Sensing Perspective On Cloud And Precipitation Properties From Southeast Atlantic Stratocumulus Clouds PDF Download

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An Airborne Remote Sensing Perspective on Cloud and Precipitation Properties from Southeast Atlantic Stratocumulus Clouds

An Airborne Remote Sensing Perspective on Cloud and Precipitation Properties from Southeast Atlantic Stratocumulus Clouds
Author: Andrew Michael Dzambo
Publisher:
Total Pages: 169
Release: 2020
Genre:
ISBN:
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Stratocumulus (StCu) clouds cover a majority of the Earth's subtropical oceanic basins, and play an important role in the global energy balance. Cloud and precipitation processes in StCu are complex, and aerosol effects add further complexity to the cloud-precipitation-climate paradigm, where these interactions are among the most widely uncertain processes in present-day climate models. The NASA ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) field campaign between 2016-18 observed cloud-aerosol-precipitation interactions over the Southeast Atlantic Ocean. One of the 20+ instruments deployed during ORACLES was the Airborne Precipitation Radar - 3rd Generation (APR-3). The APR-3 collected over 18 million profiles during the three deployments. A precipitation retrieval algorithm (called 2C-RAIN) was adapted from the CloudSat 2C-RAIN-PROFILE precipitation retrieval algorithm to meet ORACLES science objectives. The majority of 2C-RAIN precipitation rates were under 0.01 mm/hr (0.25 mm/day). The sampling environments were considerably different in 2016 compared to 2017 and 2018, necessitating further investigation accounting for environmental controls. Cloud water path (CWP) retrievals were added to the 2C-RAIN algorithm. This retrieval expanded the utility of APR-3 measurements by collocating cloud and precipitation properties (namely CWP and RWP) for the investigation of aerosol indirect effects. This work find typical CWP to RWP ratios on the order of 50:1 to 200:1, implying CWP dominates the total liquid water path (LWP) signal. When partitioning rain rates with CWP and RWP for aerosol contact and non-contact cases, statistically significant differences are found in stable environments for CWP/RWP but not for retrieved rain rates, likely owing to the 100% and larger uncertainties associated with precipitation rate retrievals. Finally, evaporation processes are investigated between drizzling virga and surface precipitation. Evaporation rates/fluxes and corresponding latent cooling rates, between surface precipitation and virga, are on the order of 2:1 implying that surface precipitation contributes the most latent cooling to the local environment. Evaporating virga, regardless, cannot be ignored when studying latent heating and cooling. The development of the 2C-RAIN database for ORACLES, and analyses presented here, pave the way for additional observation-based studies in an area where satellite measurements have limited viability.

Remote Sensing of Aerosols, Clouds, and Precipitation

Remote Sensing of Aerosols, Clouds, and Precipitation
Author: Tanvir Islam
Publisher: Elsevier
Total Pages: 366
Release: 2017-10-18
Genre: Science
ISBN: 0128104384
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Remote Sensing of Aerosols, Clouds, and Precipitation compiles recent advances in aerosol, cloud, and precipitation remote sensing from new satellite observations. The book examines a wide range of measurements from microwave (both active and passive), visible, and infrared portions of the spectrum. Contributors are experts conducting state-of-the-art research in atmospheric remote sensing using space, airborne, and ground-based datasets, focusing on supporting earth observation satellite missions for aerosol, cloud, and precipitation studies. A handy reference for scientists working in remote sensing, earth science, electromagnetics, climate physics, and space engineering. Valuable for operational forecasters, meteorologists, geospatial experts, modelers, and policymakers alike. Presents new approaches in the field, along with further research opportunities, based on the latest satellite data Focuses on how remote sensing systems can be designed/developed to solve outstanding problems in earth and atmospheric sciences Edited by a dynamic team of editors with a mixture of highly skilled and qualified authors offering world-leading expertise in the field

Aerosol-cloud-precipitation Interaction in Ultraclean Layers and Optically Thin Veil Cloud System in the Stratocumulus to Cumulus Transition

Aerosol-cloud-precipitation Interaction in Ultraclean Layers and Optically Thin Veil Cloud System in the Stratocumulus to Cumulus Transition
Author: Kuan-Ting O
Publisher:
Total Pages: 114
Release: 2019
Genre:
ISBN:
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Recent observational studies have shown that ultraclean layers (UCLs) and optically thin veil clouds associated with precipitating deep cumulus are common features of the marine boundary layer in the stratocumulus to cumulus transition. The very low number concentration of cloud droplet and cloud condensation nuclei in UCLs, strong precipitation in the associated cumulus, together with the low optical thickness of optically thin veil clouds, make such a system particularly appealing for the study of aerosol-cloud-precipitation interactions. More importantly, low cloud radiative properties biases (i.e., too few, too bright low cloud bias) in the current generation of global climate models (GCMs) seems strongly associated with the uncertainty in representing optically thin veil clouds, and these clouds may serve as an important constraint on the too few, too bright problem. However, systematic investigation of (1) global contribution and seasonal variability of optically thin veil clouds and (2) aerosol-cloud-precipitation interactions in UCLs and optically thin veil clouds is still lacking. We aim to investigate these problems with aircraft remote sensing, satellite measurements and a cloud resolving model. The dissertation is organized into the following three sections: • Using high resolution aircraft remote sensing measurement to characterize optically thin veil clouds in the stratocumulus to cumulus transition (SCT): Aircraft remote sensing measurements (i.e., lidar and radar) taken abroad NSF/NCAR GV-HIAPER research flights flown during the Cloud System Evolution in the Trades field campaign (CSET) sampled marine air masses between Sacramento, California (38.68N, 121.58W), and Kona (19.68N, 156.08W) are used in our study. Optically thin veil clouds, defined as the subset of low clouds with cloud bases > 1 km that do not fully attenuate high-spectral-resolution lidar signal (HSRL) (i.e., indicating optical depths 3), comprise considerable cover of low clouds (~ 40 %) over the SCT. It is found that optically thin veil clouds are also geometrically thin with cloud thickness ~ 200 m, and commonly reside in the upper boundary layer with average cloud base 1.5 km. • Investigating deeper, precipitating PBLs associated with optically thin veil clouds in the Sc-Cu Transition using spaceborne satellite measurements: Variability and vertical structure of optically thin veil clouds over SCT regions around the globe are investigated using both passive and active satellite observations. These observations reveal pronounced relationships between optically thin veil clouds, strong precipitation, deep planetary boundary layer (PBL) height and low cloud droplet number concentration (CDNC). The results are in agreement with the hypothesis that the low optical thickness of veil clouds over the SCT is contingent on the low CDNC caused by strong precipitation scavenging occurring in active cumuli, a process whose efficiency is strongly dependent on maximum condensate amount in updrafts and thus is highly constrained by PBL height. • Exploring aerosol-cloud-precipitation processes in UCLs and optically thin veil clouds system using a cloud resolving model: Characteristics of UCLs and optically thin veil clouds are investigated in the cloud resolving model (CRM). The domain mean cloud and aerosol properties in UCLs and optically thin veil clouds from CRM simulations agree with recent observational studies in general. The simulation results show that the detrainment from active precipitating cumulus produces the stratiform veil clouds, which are strongly depleted in particle concentration due to very efficient coalescence-scavenging process in ascending parcels passing through cumulus towers. The simulation shows a median CDNC in thin veil clouds of 5.8 cm−3, implying that majority of thin veil clouds are UCLs as well and confirming the strong connection between veil clouds and UCLs. In addition, there is a strong correlation between surface precipitation and the fraction of low clouds that are UCLs, and such correlation implies the importance of precipitation scavenging for the formation of UCLs. A cloud resolving model coupled with a prognostic aerosol scheme is used in our study, enabling characterization of the spatiotemporal variability of aerosol in the boundary layer. The results show that depletion of aerosol concentration starts first in the upper boundary layer that is associated with in-cloud coalescence scavenging process. The evaporation of veil clouds leaves very low CCN number concentration (Na

Remote Sensing of Clouds and Precipitation

Remote Sensing of Clouds and Precipitation
Author: Constantin Andronache
Publisher: Springer
Total Pages: 288
Release: 2018-02-21
Genre: Technology & Engineering
ISBN: 3319725831
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This book presents current applications of remote sensing techniques for clouds and precipitation for the benefit of students, educators, and scientists. It covers ground-based systems such as weather radars and spaceborne instruments on satellites. Measurements and modeling of precipitation are at the core of weather forecasting, and long-term observations of the cloud system are vital to improving atmospheric models and climate projections. The first section of the book focuses on the use of ground-based weather radars to observe and measure precipitation and to detect and forecast storms, thunderstorms, and tornadoes. It also discusses the observation of clouds using ground-based millimeter radar. The second part of the book concentrates on spaceborne remote sensing of clouds and precipitation. It includes cases from the Tropical Rainfall Measuring Mission (TRMM) and the Global Precipitation Measurement (GPM) mission, using satellite radars to observe precipitation systems. Then, the focus is on global cloud observations from the ClaudSat, Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), including a perspective on the Earth Clouds, Aerosols, and Radiation Explorer (EarthCARE) satellite. It also addresses global atmospheric water vapor profiling for clear and cloudy conditions using microwave observations. The final part of this volume provides a perspective into advances in cloud modeling using remote sensing observations.

Investigation of the Cloud Microphysics and Albedo Susceptibility of the Southeast Pacific Stratocumulus Cloud Deck

Investigation of the Cloud Microphysics and Albedo Susceptibility of the Southeast Pacific Stratocumulus Cloud Deck
Author: David Painemal
Publisher:
Total Pages:
Release: 2011
Genre:
ISBN:
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Marine stratocumulus cloud regimes exert a strong climatic influence through their high solar reflectivity. Human-induced changes in stratocumulus clouds, attributed to an increase of the aerosol burden (indirect effects), can be significant given the cloud decks proximity to the continents; nevertheless, the magnitude and the final climatic consequences of these changes are uncertain. This thesis investigates further the interactions between aerosols, cloud microphysics, regional circulation, and radiative response in the Southeast Pacific stratocumulus cloud deck, one of the largest and most persistent cloud regimes in the planet. Specifically, three different aspects are addressed by this thesis: The importance of the synoptic atmospheric variability in controlling cloud microphysical and radiative changes, a validation analysis of satellite retrievals of cloud microphysics from MOderate Resolution Imaging Spectroradiometer (MODIS), and the quantitative assessments of cloud aerosol interactions along with their associated radiative forcing using primarily aircraft remote sensing data. Synoptic and satellite-derived cloud property variations for the Southeast Pacific region associated with changes in coastal satellite-derived cloud droplet number concentration (Nd) are analyzed through a composite technique. MAX and MIN Nd composites are defined by the top and bottom terciles of daily area-mean Nd values over the Arica Bight, the region with the largest mean oceanic Nd, for the five October months of 2001, 2005, 2006, 2007, and 2008. The MAX-Nd composite is characterized by a weaker subtropical anticyclone and weaker winds than the MIN-Nd composite. Additionally, the MAX-Nd composite clouds over the Arica Bight are thinner than the MIN-Nd composite clouds, have lower cloud tops, lower near-coastal cloud albedos, and occur below warmer and drier free tropospheres. At 85 ̊W, the top-of-atmosphere shortwave fluxes are significantly higher (50%) for the MAX-Nd, with thicker, lower clouds and higher cloud fractions than for the MIN-Nd. The change in Nd at this location is small, suggesting that the MAX-MIN Nd composite differences in radiative properties primarily reflects synoptic changes. The ability of MODIS level 2 retrievals to represent the cloud microphysics is assessed with in-situ measurements of droplet size distributions, collected during the VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx). The MODIS cloud optical thickness (t) correlates well with the in-situ values with a positive bias (1.42). In contrast, the standard 2.1 micron-derived MODIS cloud effective radius (r_e) is found to systematically exceed the in-situ cloud-top r_e, with a mean bias of 2.08 um. Three sources of errors that could contribute to the MODIS r_e positive bias are investigated further: the spread of the cloud droplet size distribution, the presence of a separate drizzle mode, and the sensor viewing angles. The sensor zenith viewing angles were found to have little impact, while the algorithm assumption about the cloud droplet spectra and presence of a precipitation mode could affect the retrievals but not by enough to fully explain the positive MODIS r_e bias. The droplet spectra effects account for r_e offsets smaller than 0.6 um, 0.9 um, and 1.6 um for non-drizzling, light-drizzling, and heavy-drizzling clouds respectively. An explanation for the observed MODIS bias is lacking although three-dimensional radiative effects were not considered. This investigation supports earlier studies documenting a similar bias, this time using data from newer probes. MODIS r_e and t were also combined to estimate a liquid water path (LWP) and Nd. A positive bias was also apparent in LWP, and attributed to r_e. However, when selected appropriate parameters a priori, the MODIS Nd estimate was found to agree the best with the insitu aircraft observations of the four MODIS variables. Lastly, the first aerosol indirect effect (Twomey effect) is explicitly investigated with VOCALS-REx observations, collected during three daytime research flights (Nov 9, 11, and 13), utilizing an aerosol-cloud interactions metric, and defined as ACI=dln(t)/dln(Na), with Na corresponding to the accumulation mode aerosol concentration, t derived from a broadband pyranometer, and ACI binned by cloud LWP derived from a millimeter-wavelength radiometer. Aircraft remote sensing estimates of the ACI, during sub-cloud transects, show that the cloud aerosol-interactions are strong and close to the maximum theoretical value for thin clouds, with a decrease of ACI with LWP. Although an explanation for the dependence of ACI on LWP is lacking, we found that a decrease in ACI with LWP is associated with decreases in both surface meridional winds and Nd. Similar to ACI, albedo fractional changes due to Nd fractional changes also tended to be smaller for higher LWPs, but with an overall radiative forcing larger than conservative global estimates obtained in global circulation models. The findings of this thesis emphasize the strong stratocumulus albedo response to an aerosol perturbation and its dependence on the regional scale atmospheric configuration. The results presented here can be used as a benchmark for testing regional and climate models, as well as helping to improve the current parameterizations of the first aerosol indirect effect.

Investigating Passive Cloud Retrievals of Marine Stratocumulus Over the South East Pacific

Investigating Passive Cloud Retrievals of Marine Stratocumulus Over the South East Pacific
Author: Nicholas James King
Publisher:
Total Pages:
Release: 2013
Genre:
ISBN:
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Clouds are an important modulator of the global radiation budget and yet representing their formation, evolution and interaction with aerosols still remains as one of the largest uncertainties in modelling future climate. An important requirement to understanding the processes which govern clouds is accurate measurement of their global distribution and microphysical properties over a wide range of spatial and temporal scales which can only be satisfied by passive remote sensing measurements from satellite platforms. As such the development and validation of cloud remote sensing techniques is an important ongoing task. Of particular radiative importance are marine stratocumulus clouds, due to their large global extent and high solar reflectance. This thesis uses a range of in situ and remote sensing observations of marine stratocumulus over the South East Pacific taken during the Variability of the American Monsoon Systems (VAMOS) Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) to investigate some outstanding issues relating to passive remote sensing. In particular answers to two questions are sought: 1) Do measurements of solar reflectance at multiple wavelengths with different absorption properties allow information about the vertical structure of the cloud to be derived? 2) Is there a high bias in passive retrievals of droplet effective radius? A unique airborne hyperspectral data set is evaluated for its potential to provide insight into these problems but through extensive comparison to collocated in situ and satellite observations along with an analysis of historical calibrations, it is concluded that the calibration quality of this dataset is not sufficient to meet its scientific objectives. A theoretical study into the information content of multi-wavelength measurements to retrieve the vertical variation of droplet size is presented. Measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite instrument are shown to contain little information related to the vertical structure of typical marine stratocumulus. The information content of hyperspectral measurements is shown to be significantly larger, indicating the potential to perform profile retrievals from future measurements. A comparison of in situ profile measurements to collocated MODIS cloud retrievals adds to the existing body of evidence that passive retrievals of the droplet effective radius of marine stratocumulus are high biased when compared to other measurement sources. Potential sources of this bias are investigated and many of the previously postulated reasons behind the bias are ruled out. It is also shown that the differences between MODIS retrievals of effective radius performed at different wavelengths bear no relation to the in situ observed vertical structure of the cloud.

Remote Sensing of Drizzle Onset and Cloud Microphysical Properties in Marine Stratocumulus

Remote Sensing of Drizzle Onset and Cloud Microphysical Properties in Marine Stratocumulus
Author: Jasmine Rémillard
Publisher:
Total Pages:
Release: 2013
Genre:
ISBN:
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"Low-level stratiform clouds remain one of the wildcards in future climate simulations. Despite their important role in the earth's radiation budget and the large number of dedicated field campaigns, several cloud-scale processes in marine stratocumulus clouds remain misrepresented. The 19-month-long deployment of the Atmospheric Radiation Measurement Program Mobile Facility in the Azores provided the longest and most comprehensive ground-based observational dataset of marine boundary layer clouds to date. The first objective of this project was the documentation of the frequency of occurrence of different cloud and precipitation systems in the Azores using a combination of passive and active measurements. The analysis indicates that, even though clouds were often observed (close to 80 % of the time), especially in the boundary layer (~50 %), a single-layer stratocumulus coverage rarely persisted more than a day. In fact, many stratocumulus clouds were observed to have cumulus clouds underneath them. This is linked to the nearly constant decoupled state of the boundary layer in the Azores, contrary to what has been observed in the Pacific decks. 35 cases of mostly single-layer persisting stratocumulus coverage were selected for further analysis. Results include similarities with other studies (e.g., maximum coverage at night, thicker clouds needed to drizzle, and importance of cloud-top radiative cooling at night), as well as differences (e.g., coherent structures account for a smaller fraction of the updraft mass flux). The second objective of this project was to revisit the detection of drizzle-size particles in stratocumulus clouds using radar observations. First, the cloud and drizzle size distributions are related theoretically to the radar measurements, including the effects of the dynamics. Then, a forward radar Doppler spectra model was developed to test the sensitivity of the radar measurements to modifications of the drizzle contribution. Finally, a simple 1-D steady-state model was exploited to simulate drizzle growth as it falls in a cloud, using the forward model to link the output back to the radar observations. Using that combination of models, some observed features of the drizzle evolution inside continental and maritime stratocumulus clouds were successfully investigated. Overall, it was found that the skewness of a radar Doppler spectrum is a good indicator of the presence of early drizzle droplets, while a reflectivity or Doppler velocity threshold indicates the change in dominance in the Doppler spectrum occurring when drizzle is well developed. The third and final objective of this project was to revisit another long-standing challenge: the retrieval of cloud microphysical properties using a combination of radar-radiometer measurements. A new technique was developed to retrieve the cloud particle size distribution in stratocumulus clouds, adding a microphysical condensational model under steady-state supersaturation conditions to a common retrieval method. The results appear reasonable in two nondrizzling marine stratocumulus clouds, and the derived cloud optical depth compares well with the one derived independently with another instrument. The errors of the retrievals were also estimated, demonstrating the added value of the new technique." --

Stratocumulus Precipitation and Entrainment Experiment (SPEE) Field Campaign Report

Stratocumulus Precipitation and Entrainment Experiment (SPEE) Field Campaign Report
Author:
Publisher:
Total Pages: 7
Release: 2016
Genre:
ISBN:
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The scientific focus of this project was to examine precipitation and entrainment processes in marine stratocumulus clouds. The entrainment studies focused on characterizing cloud turbulence at cloud top using Doppler cloud radar observations. The precipitation studies focused on characterizing the precipitation and the macroscopic properties (cloud thickness, and liquid water path) of the clouds. This project will contribute to the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility's overall objective of providing the remote-sensing observations needed to improve the representation of key cloud processes in climate models. It will be of direct relevance to the components of ARM dealing with entrainment and precipitation processes in stratiform clouds. Further, the radar observing techniques that will be used in this study were developed using ARM Southern Great Plains (SGP) facility observations under Atmospheric System Research (ASR) support. The observing systems operating automatously from a site located just north of the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) aircraft hangar in Marina, California during the period of 1 May to 4 November 2015 included: 1. Microwave radiometer: ARM Microwave Radiometer, 3-Channel (MWR3C) with channels centered at 23.834, 30, and 89 GHz; supported by Dr. Maria Cadeddu. 2. Cloud Radar: CIRPAS 95 GHz Frequency Modulated Continuous Wave (FMCW) Cloud Radar (Centroid Frequency Chirp Rate [CFCR]); operations overseen by Drs. Ghate and Albrecht. 3. Ceilometer: Vaisala CK-14; operations overseen by Drs. Ghate and Albrecht.