scholarly journals Comparison of Concurrent Radar and Aircraft Measurements of Cirrus Clouds

UND Datasets ◽  
2020 ◽  
Author(s):  
Nicholas Gapp ◽  
David J. Delene
Keyword(s):  
Cirrus Clouds ◽  
Aircraft Measurements

scholarly journals Observations and modelling of microphysical variability, aggregation and sedimentation in tropical storm cirrus outflow regions

2011 ◽  
Vol 11 (8) ◽  
pp. 23761-23800
Author(s):  
M. W. Gallagher ◽  
P. J. Connolly ◽  
A. Heymsfield ◽  
K. N. Bower ◽  
T. W. Choularton ◽  
...  
Keyword(s):  
Collection Efficiency ◽  
Aerosol Particles ◽  
Tropical Storm ◽  
Cirrus Clouds ◽  
Ice Crystals ◽  
Aircraft Measurements ◽  
Ice Crystal ◽  
Crystal Aggregation ◽  
Small Crystals ◽  
Bulk Model

Abstract. Aircraft measurements of the microphysics of a tropical convective anvil (at temperatures ~−60 °C) forming above the HECTOR storm have been performed. The observed microphysics has been compared to a bulk and explicit microphysical model of the anvil region including crystal aggregation and sedimentation. It has been found that in flights made using straight and level runs perpendicular to the storm that the number of ice crystals initially decreased with distance from the storm as aggregation took place resulting in larger crystals followed by their loss due to sedimentation. At still greater distances from the storm the number of very small crystals increased. This is attributed to the formation of new ice crystals on aerosol particles as the ice super saturation rose following the depletion of the larger ice particles following aggregation and sedimentation. Comparison with the explicit microphysics model showed that the changes in the shapes of the ice crystal spectra as a function of distance from the storm could be explained by the explicit microphysical model if the aggregation efficiency was set to E~0.02. It is noteworthy that this aggregation efficiency is much larger than values normally used in cloud resolving models at these temperatures (typically E~0.0016). Furthermore if the bulk model is used then optimum agreement was reached with a collection efficiency for aggregation of E~0.05. These results are important for the treatment of the evolution and lifetime of tropical cirrus clouds.

Cirrus Clouds and the Climate

1971 ◽  
Vol 28 (8) ◽  
pp. 1513-1515 ◽  
Author(s):  
Stephen K. Cox
Keyword(s):  
Cirrus Clouds

scholarly journals Aircraft measurements of polar organic tracer compounds in tropospheric particles (PM<sub>10</sub>) over central China

2014 ◽  
Vol 14 (8) ◽  
pp. 4185-4199 ◽  
Author(s):  
P. Q. Fu ◽  
K. Kawamura ◽  
Y. F. Cheng ◽  
S. Hatakeyama ◽  
A. Takami ◽  
...  
Keyword(s):  
Organic Nitrogen ◽  
Ground Surface ◽  
Organic Aerosol ◽  
Central China ◽  
Gas Chromatography Mass Spectrometry ◽  
Strong Positive Correlation ◽  
Aircraft Measurements ◽  
Nitrogen Species ◽  
West China ◽  
Biological Aerosols

Abstract. Atmospheric aerosol samples were collected by aircraft at low to middle altitudes (0.8–3.5 km a.g.l.) over central East to West China during summer 2003 and spring 2004. The samples were analyzed for polar organic compounds using a technique of solvent extraction/BSTFA derivatization/gas chromatography–mass spectrometry. Biogenic secondary organic aerosol (SOA) tracers from the oxidation of isoprene were found to be more abundant in summer (3.3–138 ng m−3, mean 39 ng m−3) than in spring (3.2–42 ng m−3, 15 ng m−3), while α/β-pinene and β-caryophyllene SOA tracers showed similar abundances between these two seasons. A strong positive correlation (R2 = 0.83) between levoglucosan and β-caryophyllinic acid was found in the spring samples vs. a weak correlation (R2 = 0.17) in the summer samples, implying substantial contributions from biomass burning to the β-caryophyllinic acid production in spring. Two organic nitrogen species (oxamic acid and carbamide) were detected in the aircraft aerosol samples, and their concentrations were comparable to those of biogenic SOA tracers. Most of the primary organic aerosol (POA) and SOA tracers were less abundant at higher altitudes, suggesting they are of ground surface origin, either being directly emitted from anthropogenic/natural sources on the ground surface, or rapidly formed through photooxidation of their precursors emitted from the ground surface and then diluted during uplifting into the troposphere. This study demonstrates that primary biological aerosols, biogenic SOA, and organic nitrogen species are important components of organic aerosols in the troposphere over central China during warm seasons.

scholarly journals A Polar Low Pair over the Norwegian Sea

2009 ◽  
Vol 137 (8) ◽  
pp. 2559-2575 ◽  
Author(s):  
Burghard Brümmer ◽  
Gerd Müller ◽  
Gunnar Noer
Keyword(s):  
Heat Budget ◽  
Cloud Layer ◽  
Sea Surface ◽  
Cloud Base ◽  
Aircraft Measurements ◽  
Polar Lows ◽  
The North ◽  
Polar Low ◽  
Upper Level Jet ◽  
Almost All

Abstract During the Lofotes cyclone experiment (LOFZY 2005), two polar lows developed one behind the other inside a cold-air outbreak from the north in the lee of Spitsbergen on 7 March 2005. Buoys, ship, and aircraft measurements as well as satellite imagery are applied to analyze the polar low bulk properties, the horizontal and vertical structure, and the mass, moisture, and heat budget. The lifetime of the system until landfall at northern Norway was 12 h. The generation occurred under the left exit region of an upper-level jet with 70 m s−1. Both polar lows had a radius of 100–130 km and extended to a height of about 2.5 km. The propagation speeds were within 14–17 m s−1 and correspond to the vertically averaged wind velocity of the lowest 2.5 km. In the polar low centers the pressure was about 2–3 hPa lower and the air was 1–2 K warmer and drier than in the surroundings. Aircraft measurements in the second of the two polar lows show an embedded frontlike precipitation band north of the center. Here, the highest low-level winds with 25 m s−1 and the largest fluxes of sensible and latent heat with 290 and 520 W m−2, respectively, were measured (areal averages amounted to 115 and 190 W m−2). Aircraft data show mass convergence in the subcloud layer (0–900 m) and divergence in the cloud layer (900–2500 m). Moisture supply by evaporation from the sea surface was about twice as large as that by convergence in the subcloud layer. The condensation rate in the cloud layer nearly equaled the rate of evaporation at the sea surface. Almost all condensed cloud water was converted to precipitation water. Only half of the precipitation at the cloud base reached the sea surface.

Specular scattering in cirrus clouds

1995 ◽  
Author(s):  
Joseph G. Shanks ◽  
David K. Lynch
Keyword(s):  
Cirrus Clouds ◽  
Specular Scattering

scholarly journals Correction Method for RS80-A Humicap Humidity Profiles and Their Validation by Lidar Backscattering Profiles in Tropical Cirrus Clouds

2005 ◽  
Vol 22 (1) ◽  
pp. 18-29 ◽  
Author(s):  
Ulrich Leiterer ◽  
Horst Dier ◽  
Dagmar Nagel ◽  
Tatjana Naebert ◽  
Dietrich Althausen ◽  
...  
Keyword(s):  
Evaluation Method ◽  
Time Lag ◽  
Correction Method ◽  
Cirrus Clouds ◽  
Temperature Dependent ◽  
Upper Troposphere ◽  
Statistical Comparison ◽  
Daily Show ◽  
Tropical Tropopause ◽  
Humidity Profiles

Abstract Routine radiosonde relative humidity (RH) measurements are not reliable as they are presently used in the global upper-air network. The new Lindenberg measuring and evaluation method, which provides RH profile measurements with an accuracy of ±1% RΗ in the temperature range from 35° to −70°C near the tropical tropopause is described. This Standardized Frequencies (FN) method uses a thin-film capacitive polymer sensor of a modified RS90-H Humicap radiosonde. These research humidity reference radiosondes (FN sondes) are used to develop a correction method for operational RS80-A Humicap humidity profiles. All steps of correction and quality control for RS80-A radiosondes are shown: ground-check correction, time-lag and temperature-dependent correction, and the recognition of icing during the ascent. The results of a statistical comparison between FN sondes and RS80-A sondes are presented. Corrected humidity data of operational RS80-A sondes used in Lindenberg (4 times daily) show no bias when compared to FN radiosondes and have an uncertainty of about ±3% RH at the 1 σ or 68% confidence level from 1000 to about 150 hPa. Only a small dry bias of at most −2% RH remains in the lowest part of the boundary layer (up to 500-m height). Finally, some examples of corrected RS80-A RH profiles in cirrus clouds validated by lidar backscattering profiles in a region of the intertropical convergence (Maldive Islands) are demonstrated. The soundings indicate that ice-saturated and ice-supersaturated air above 10-km height were connected with cirrus clouds in all 47 investigated cases, and, second, that the corrected RS80-A RH profiles also provide good quality information on water vapor in the upper troposphere.

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