ice clouds
Recently Published Documents


TOTAL DOCUMENTS

609
(FIVE YEARS 127)

H-INDEX

56
(FIVE YEARS 4)

2021 ◽  
Author(s):  
Iris Papakonstantinou-Presvelou ◽  
Johannes Quaas

<p>This study investigates low-level ice clouds in the Arctic and their potential relation to the surface aerosols. These aerosols or ice nucleating particles (INPs), are necessary for the heterogeneous nucleation of ice in temperatures above -38°C. Several studies in the past have investigated the sources of INPs and their nucleating behavior with response to the temperature. According to these studies, it has been suggested that a marine source of INPs coming from sea spray is able to nucleate ice in temperatures close to -5<sup>o</sup>C. What we do here is a large-scale comparison of boundary-layer ice clouds over open ocean and sea ice, over the whole Arctic region for the time period of 2006-2016. We use for this purpose a satellite-retrieved quantity, the ice crystal number concentration (N<sub>i</sub>), which we investigate in relation to the temperature. We study clouds with regard to the region and season they form and we examine their coupling to the surface. Our findings show - contrary to previous expectation - enhanced ice crystal numbers over sea ice compared to open ocean, in temperatures above -10<sup>o</sup>C. In lower temperatures this difference still persists for the lower Arctic latitudes (<70<sup>o</sup>N), especially for clouds that are coupled to the surface.</p>


2021 ◽  
Author(s):  
Pradeep Khatri ◽  
Tadahiro Hayasaka ◽  
Hitoshi Irie ◽  
Husi Letu ◽  
Takashi Y. Nakajima ◽  
...  

Abstract. The Second-generation Global Imager (SGLI) onboard the Global Change Observation Mission – Climate (GCOM-C) satellite launched on December 23, 2017, observes various geophysical parameters with the aim of a better understanding of the global climate system. As part of that aim, SGLI has great potential to unravel several uncertainties related to clouds by providing new cloud products along with several other atmospheric products related to cloud climatology, including aerosol products from polarization channels. However, a very little is known about the quality of the SGLI cloud products. This study uses data about clouds and global irradiances observed from the Earth’s surface using a sky radiometer and a pyranometer, respectively, to understand the quality of the two most fundamental cloud properties—cloud optical depth (COD) and cloud-particle effective radius (CER)—of both water and ice clouds. The SGLI-observed COD agrees well with values observed from the surface, although it agrees better for water clouds than for ice clouds, while the SGLI-observed CER exhibits poorer agreement than does the COD, with the SGLI values being generally higher than the sky radiometer values. These comparisons between the SGLI and sky radiometer cloud properties are found to differ for different cloud types of both the water and ice cloud phases and different solar and satellite viewing angles by agreeing better for relatively uniform and flat cloud type and for relatively low solar zenith angle. Analyses of SGLI-observed reflectance functions and values calculated by assuming plane-parallel cloud layers suggest that SGLI-retrieved cloud properties can have biases on the solar and satellite viewing angles, similar to other satellite sensors including the Moderate Resolution Imaging Spectroradiometer (MODIS). Furthermore, it is found that the SGLI-observed cloud properties reproduce global irradiances quite satisfactorily for both water and ice clouds by resembling several important features of the COD comparison, such as the better agreement for water clouds than for ice clouds and the tendency to underestimate (resp. overestimate) the COD in SGLI observations for optically thick (resp. thin) clouds.


Author(s):  
B. Cooper ◽  
M. Torre Juárez ◽  
M. Mischna ◽  
M. Lemmon ◽  
G. Martínez ◽  
...  

2021 ◽  
Author(s):  
Andries Jan de Vries ◽  
Franziska Aemisegger ◽  
Stephan Pfahl ◽  
Heini Wernli

Abstract. Tropical ice clouds have an important influence on the Earth’s radiative balance. They often form as a result of tropical deep convection, which strongly affects the water budget of the tropical tropopause layer. Ice cloud formation involves complex interactions on various scales, which are not fully understood yet and lead to large uncertainties in climate predictions. In this study, we investigate the formation of tropical ice clouds related to deep convection in the West African monsoon, using stable water isotopes as tracers of moist atmospheric processes. We perform simulations using the regional isotope-enabled model COSMOiso with different resolutions and treatments of convection for the period of June–July 2016. First, we evaluate the ability of our simulations to represent the isotopic composition of monthly precipitation through comparison with GNIP observations, and the precipitation characteristics related to the monsoon evolution and convective storms based on insights from the DACCIWA field campaign in 2016. Next, a case study of a mesoscale convective system (MCS) explores the isotope signatures of tropical deep convection in atmospheric water vapour and ice. Convective updrafts within the MCS inject enriched ice into the upper troposphere leading to depletion of vapour within these updrafts due to the preferential condensation and deposition of heavy isotopes. Water vapour in downdrafts within the same MCS are enriched by non-fractionating sublimation of ice. In contrast to ice within the MCS core regions, ice in widespread cirrus shields is isotopically in approximate equilibrium with the ambient vapour, which is consistent with in situ formation of ice. These findings from the case study are supported by a statistical evaluation of isotope signals in the West African monsoon ice clouds. The following five key processes related to tropical ice clouds can be distinguished based on their characteristic isotope signatures: (1) convective lofting of enriched ice into the upper troposphere, (2) cirrus clouds that form in situ from ambient vapour under equilibrium fractionation, (3) sedimentation and sublimation of ice in the mixed-phase cloud layer in the vicinity of convective systems and underneath cirrus shields, (4) sublimation of ice in convective downdrafts that enriches the environmental vapour, and (5) the freezing of liquid water in the mixed-phase cloud layer at the base of convective updrafts. Importantly, the results show that convective systems strongly modulate the humidity budget and the isotopic composition of the lower tropical tropopause layer. They contribute to about 40 % of the total water and 60 % of HDO in the 175–125 hPa layer in the African monsoon region according to estimates based on our model simulations. Overall, this study demonstrates that isotopes can serve as useful tracers to disentangle the role of different processes in the Earth’s water cycle, including convective transport, the formation of ice clouds, and their impact on the tropical tropopause layer.


2021 ◽  
Author(s):  
Grigorii P. Kokhanenko ◽  
Yurii S. Balin ◽  
Anatoli G. Borovoi ◽  
Marina G. Klemasheva ◽  
Sergei V. Nasonov ◽  
...  
Keyword(s):  

2021 ◽  
Vol 923 (2) ◽  
pp. 264
Author(s):  
Shang-Min Tsai ◽  
Matej Malik ◽  
Daniel Kitzmann ◽  
James R. Lyons ◽  
Alexander Fateev ◽  
...  

Abstract We present an update of the open-source photochemical kinetics code VULCAN to include C–H–N–O–S networks and photochemistry. The additional new features are advection transport, condensation, various boundary conditions, and temperature-dependent UV cross sections. First, we validate our photochemical model for hot Jupiter atmospheres by performing an intercomparison of HD 189733b models between Moses et al., Venot et al., and VULCAN, to diagnose possible sources of discrepancy. Second, we set up a model of Jupiter extending from the deep troposphere to upper stratosphere to verify the kinetics for low temperature. Our model reproduces hydrocarbons consistent with observations, and the condensation scheme successfully predicts the locations of water and ammonia ice clouds. We show that vertical advection can regulate the local ammonia distribution in the deep atmosphere. Third, we validate the model for oxidizing atmospheres by simulating Earth and find agreement with observations. Last, VULCAN is applied to four representative cases of extrasolar giant planets: WASP-33b, HD 189733b, GJ 436b, and 51 Eridani b. We look into the effects of the C/O ratio and chemistry of titanium/vanadium species for WASP-33b, we revisit HD 189733b for the effects of sulfur and carbon condensation, the effects of internal heating and vertical mixing (K zz) are explored for GJ 436b, and we test updated planetary properties for 51 Eridani b with S8 condensates. We find that sulfur can couple to carbon or nitrogen and impact other species, such as hydrogen, methane, and ammonia. The observable features of the synthetic spectra and trends in the photochemical haze precursors are discussed for each case.


2021 ◽  
Author(s):  
Jonathan H Jiang ◽  
Kyle Johnson ◽  
Qing Yue ◽  
Kristen Fahy ◽  
Scott E. Palo
Keyword(s):  

2021 ◽  
Author(s):  
Jonathan Jiang ◽  
Kyle Johnson ◽  
Qing Yue ◽  
Kristen A Fahy ◽  
Scott Palo
Keyword(s):  

2021 ◽  
Vol 2 ◽  
Author(s):  
Tamás Várnai ◽  
Alexander Marshak ◽  
Alexander Kostinski

Satellite images often feature sun glints caused by the specular reflection of sunlight from water surfaces or from horizontally oriented ice crystals occurring in clouds. Such glints can prevent accurate retrievals of atmospheric and surface properties using existing algorithms, but the glints can also be used to infer more about the glint-causing objects—for example about the microphysical properties and radiative effects of ice clouds. This paper introduces the recently released operational glint product of the Earth Polychromatic Camera (EPIC) onboard the Deep Space Climate Observatory (DSCOVR) spacecraft. Most importantly, the paper describes the algorithm used for generating the key component of the new product: a glint mask indicating the presence of sun glint caused by the specular reflection of sunlight from ice clouds and smooth water surfaces. After describing the glint detection algorithm and glint product, the paper shows some examples of the detected glints and discusses some basic statistics of the glint population in a yearlong dataset of EPIC images. These statistics provide insights into the performance of glint detection and point toward possibilities for using the glint product to gain scientific insights about ice clouds and water surfaces.


Sign in / Sign up

Export Citation Format

Share Document