scholarly journals Simultaneous Determination of Aerosol and Thin Cirrus Optical Depths over Oceans from MODIS Data: Some Case Studies

2006 ◽  
Vol 63 (9) ◽  
pp. 2307-2323 ◽  
Author(s):  
J. K. Roskovensky ◽  
K. N. Liou
Keyword(s):  
Optical Depth ◽  
Crystal Size ◽  
A Priori ◽  
Lookup Table ◽  
Ice Crystal ◽  
Radiative Forcings ◽  
Modis Data ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Ice Crystal Size

Abstract The importance of separating thin cirrus and aerosols from satellite remote sensing to produce broader and more accurate fields for the determination of respective radiative forcings is highlighted. This has been accomplished through the development of a new methodology for retrieving both thin cirrus and aerosol optical depths simultaneously over oceans from the Moderate Resolution Imaging Spectroradiometer (MODIS) data. This method employs a procedure to quantify and remove the thin cirrus contribution to the observed reflectance through a correlation of visible and 1.38-μm reflectances so that the aerosol signal can be extracted. Aerosol optical depths are then retrieved through comparisons with the simulated reflectances created a priori. Using the aerosol optical depth along with the specific viewing geometry and surface reflectance as pointers to locations in a lookup table of modeled reflectances, cirrus optical depth and an effective ice crystal size can be retrieved. An iterative scheme has been created that uses the retrieved effective cirrus ice crystal size to account for the effect that the particle size distribution has on the correlation of visible and 1.38-μm reflectance. Retrievals of both aerosol and thin cirrus optical depths over the Atmospheric Radiation Measurement (ARM) Tropical Western Pacific (TWP) site of Nauru performed on a limited number of cases have proven to be consistent with values determined from ground measurements. Also, comparisons with the MODIS aerosol retrievals over a broad area of ocean have highlighted the potential usefulness of this procedure in increasing the amount of potential aerosol information recovered and removing the ever-present thin cirrus contamination.

scholarly journals Interpretation of AIRS Data in Thin Cirrus Atmospheres Based on a Fast Radiative Transfer Model

2007 ◽  
Vol 64 (11) ◽  
pp. 3827-3842 ◽  
Author(s):  
Qing Yue ◽  
K. N. Liou ◽  
S. C. Ou ◽  
B. H. Kahn ◽  
P. Yang ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Data Assimilation ◽  
Optical Depth ◽  
Crystal Size ◽  
Thermal Infrared ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Cirrus Cloud ◽  
Ice Crystal ◽  
Ice Crystal Size

Abstract A thin cirrus cloud thermal infrared radiative transfer model has been developed for application to cloudy satellite data assimilation. This radiation model was constructed by combining the Optical Path Transmittance (OPTRAN) model, developed for the speedy calculation of transmittances in clear atmospheres, and a thin cirrus cloud parameterization using a number of observed ice crystal size and shape distributions. Numerical simulations show that cirrus cloudy radiances in the 800–1130-cm−1 thermal infrared window are sufficiently sensitive to variations in cirrus optical depth and ice crystal size as well as in ice crystal shape if appropriate habit distribution models are selected a priori for analysis. The parameterization model has been applied to the Atmospheric Infrared Sounder (AIRS) on board the Aqua satellite to interpret clear and thin cirrus spectra observed in the thermal infrared window. Five clear and 29 thin cirrus cases at nighttime over and near the Atmospheric Radiation Measurement program (ARM) tropical western Pacific (TWP) Manus Island and Nauru Island sites have been chosen for this study. A χ2-minimization program was employed to infer the cirrus optical depth and ice crystal size and shape from the observed AIRS spectra. Independent validation shows that the AIRS-inferred cloud parameters are consistent with those determined from collocated ground-based millimeter-wave cloud radar measurements. The coupled thin cirrus radiative transfer parameterization and OPTRAN, if combined with a reliable thin cirrus detection scheme, can be effectively used to enhance the AIRS data volume for data assimilation in numerical weather prediction models.

scholarly journals Determination of Ice Crystal Size Distributions in Frozen Desserts

1991 ◽  
Vol 74 (10) ◽  
pp. 3334-3344 ◽  
Author(s):  
D.P. Donhowe ◽  
R.W. Hartel ◽  
R.L. Bradley
Keyword(s):  
Crystal Size ◽  
Size Distributions ◽  
Ice Crystal ◽  
Crystal Size Distributions ◽  
Ice Crystal Size

scholarly journals Characterization of Arctic mixed-phase cloud properties at small scale and coupling with satellite remote sensing

2017 ◽  
Author(s):  
Guillaume Mioche ◽  
Olivier Jourdan ◽  
Julien Delanoë ◽  
Christophe Gourbeyre ◽  
Guy Febvre ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Crystal Size ◽  
Mixed Phase ◽  
Ice Crystals ◽  
Small Scale ◽  
Vertical Profiles ◽  
Liquid Droplets ◽  
Ice Crystal ◽  
High Concentration ◽  
Ice Crystal Size

Abstract. This study aims to characterize the microphysical and optical properties of ice crystals and supercooled liquid droplets within low-level Arctic mixed-phase clouds (MPC). We compiled and analyzed cloud in situ measurements from 4 airborne campaigns (18 flights, 71 vertical profiles in MPC) over the Greenland Sea and the Svalbard region. Cloud phase discrimination and representative vertical profiles of number, size, mass and shapes of ice crystals and liquid droplets are assessed. The results show that the liquid phase dominates the upper part of the MPC with high concentration of small droplets (120 cm−3, 15&tinsp;μm), and averaged LWC around 0.2 g m−3. The ice phase is found everywhere within the MPC layers, but dominates the properties in the lower part of the cloud and below where ice crystals precipitate down to the surface. The analysis of the ice crystal morphology highlights that irregulars and rimed are the main particle habit followed by stellars and plates. We hypothesize that riming and condensational growth processes (including the Wegener-Bergeron-Findeisein mechanism) are the main growth mechanisms involved in MPC. The differences observed in the vertical profiles of MPC properties from one campaign to another highlight that large values of LWC and high concentration of smaller droplets are possibly linked to polluted situations which lead to very low values of ice crystal size and IWC. On the contrary, clean situations with low temperatures exhibit larger values of ice crystal size and IWC. Several parameterizations relevant for remote sensing or modeling are also determined, such as IWC (and LWC) – extinction relationship, ice and liquid integrated water paths, ice concentration and liquid water fraction according to temperature. Finally, 4 flights collocated with active remote sensing observations from CALIPSO and CloudSat satellites are specifically analyzed to evaluate the cloud detection and cloud thermodynamical phase DARDAR retrievals. This comparison is valuable to assess the sub-pixel variability of the satellite measurements as well as their shortcomings/performance near the ground.

scholarly journals Saharan dust infrared optical depth and altitude retrieved from AIRS: a focus over North Atlantic – comparison to MODIS and CALIPSO

2010 ◽  
Vol 10 (4) ◽  
pp. 1953-1967 ◽  
Author(s):  
S. Peyridieu ◽  
A. Chédin ◽  
D. Tanré ◽  
V. Capelle ◽  
C. Pierangelo ◽  
...  
Keyword(s):  
Optical Depth ◽  
North Atlantic ◽  
Western Indian Ocean ◽  
Saharan Dust ◽  
Orthogonal Polarization ◽  
Dust Layer ◽  
The North ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Good Agreement

Abstract. Monthly mean infrared (10 μm) dust layer aerosol optical depth (AOD) and mean altitude are simultaneously retrieved over the tropics (30° S–30° N) from almost seven years of Atmospheric Infrared Sounder (AIRS) observations covering the period January 2003 to September 2009. The method developed relies on the construction of look-up-tables computed for a large selection of atmospheric situations and follows two main steps: first, determination of the observed atmospheric thermodynamic situation and, second, determination of the dust properties. A very good agreement is found between AIRS-retrieved AODs and visible optical depths from the Moderate resolution Imaging Spectroradiometer (MODIS/Aqua) during the main (summer) dust season, in particular for three regions of the tropical North Atlantic and one region of the north-western Indian Ocean. Outside this season, differences are mostly due to the sensitivity of MODIS to aerosol species other than dust and to the more specific sensitivity of AIRS to the dust coarse mode. AIRS-retrieved dust layer mean altitudes are compared to the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP/CALIPSO) aerosol mean layer altitude for the period June 2006 to June 2009. Results for a region of the north tropical Atlantic downwind of the Sahara show a good agreement between the two products (σ≈360 m). Differences observed in the peak-to-trough seasonal amplitude, smaller from AIRS, are principally attributed to the large difference in spatial sampling of the two instruments. They also come from the intrinsic limit in sensitivity of the passive infrared sounders for low altitudes. These results demonstrate the capability of high resolution infrared sounders to measure not only dust aerosol AOD but also the mean dust layer altitude.

scholarly journals Microwave assisted freezing part 2: Impact of microwave energy and duty cycle on ice crystal size distribution

2020 ◽  
Vol 62 ◽  
pp. 102359
Author(s):  
Mathieu Sadot ◽  
Sébastien Curet ◽  
Sylvie Chevallier ◽  
Alain Le-Bail ◽  
Olivier Rouaud ◽  
...  
Keyword(s):  
Size Distribution ◽  
Duty Cycle ◽  
Crystal Size ◽  
Microwave Energy ◽  
Crystal Size Distribution ◽  
Ice Crystal ◽  
Microwave Assisted ◽  
Ice Crystal Size

A COMPARISON OF INJURY AND SURVIVAL OF LARVAE OF CEPHUS CINCTUS NORT. AFTER INTRACELLULAR AND EXTRACELLULAR FREEZING

1961 ◽  
Vol 39 (3) ◽  
pp. 349-357 ◽  
Author(s):  
R. W. Salt
Keyword(s):  
Strong Evidence ◽  
Crystal Size ◽  
Activity Level ◽  
New Method ◽  
Freezing Injury ◽  
Ice Crystal ◽  
Wheat Stem Sawfly ◽  
Cephus Cinctus ◽  
Level Of Activity ◽  
Ice Crystal Size

Extracellular freezing of larvae of the wheat stem sawfly, Cephus cinctus Nort., was produced at −2.5 °C by a new method. Slow further cooling to −10, −15, or −20 °C added to extracellular ice with no intracellular freezing. Other larvae that were supercooled to and frozen at −10, −15, or −20 °C froze intracellularly. Comparisons of the effects of these two types of freezing were therefore possible at equivalent temperatures. Level of activity after freezing was used as the criterion of injury.Intracellular freezing was more injurious than extracellular freezing at −15 and −20 °C, but not at −10 °C. Injuries, as well as differences in injury due to type of freezing, decreased gradually to insignificance above −10 °C. Although larvae frozen extracellularly held an initial advantage over those frozen intracellularly, survivors of the latter group retained their vitality better, probably because they lost weight more slowly.Differences in injury and in activity level after freezing at −15 and −20 °C were insufficient to justify the use of freezing site (intracellular or extracellular) as a principal basis for explaining freezing injury. The same conclusion applies to ice crystal size and configuration, which differed vastly in the two types of freezing.These conclusions depend on whether freezing was actually intracellular or extracellular as represented. Strong evidence is presented that freezing was in fact as specified.

Effect of static electric field on ice crystal size reduction during freezing of pork meat

2013 ◽  
Vol 20 ◽  
pp. 115-120 ◽  
Author(s):  
E. Xanthakis ◽  
M. Havet ◽  
S. Chevallier ◽  
J. Abadie ◽  
A. Le-Bail
Keyword(s):  
Electric Field ◽  
Crystal Size ◽  
Size Reduction ◽  
Pork Meat ◽  
Ice Crystal ◽  
Static Electric Field ◽  
Ice Crystal Size

scholarly journals Crystal Size and Orientation Patterns in the Wisconsin-Age Ice from Dye 3, Greenland

1988 ◽  
Vol 10 ◽  
pp. 109-115 ◽  
Author(s):  
C.C. Langway ◽  
H. Shoji ◽  
N. Azuma
Keyword(s):  
Crystal Size ◽  
Ice Core ◽  
Ice Crystal ◽  
Axis Orientation ◽  
Measuring Device ◽  
Thin Sections ◽  
Core Samples ◽  
Physical Measurements ◽  
Ice Crystal Size ◽  
Velocity Measuring

Crystal size and c-axis orientation patterns were measured on the Dye 3, Greenland, deep ice core in order to investigate time-dependent changes or alterations in the physical character of the core as a function of time after recovery. The physical measurements were expanded to include depth intervals not previously studied in the field. The recent study focused on core samples located between 1786 m and the bottom of the ice sheet at 2037 m.Manual c-axis measurements were made on 23 new thin sections using a Rigsby-type universal stage. A new semi-automatic ultrasonic wave-velocity measuring device was developed in order to compare the results with the earlier manual measurements and to study an additional 114 ice-core samples in the Wisconsin-age ice. Crystal-size measurements were made on specimen surfaces by inducing evaporation grooves at crystal boundaries and measuring linear intercepts. The ultrasonically measured test samples were subsequently cleaned and analyzed by ion chromatography in order to measure impurity concentration levels of Cl−, NO3− and SO42− and study their effects on crystal growth and c-axis orientation.

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