A case study of formation and maintenance of a lower stratospheric cirrus cloud over the tropics

Sandhya, M.; Sridharan, S.; Devi, M.; Kandula, Niranjan; Jayaraman, A.

doi:10.5194/angeo-33-599-2015

Cited by 11 publications

(6 citation statements)

References 47 publications

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“…During Plinian explosive eruptions, solid and liquid ejecta, ash, and gas-vapor emissions intermix with each other, heat, and ascend inside the "convective thrust region" of an eruption column. Then the heated air together with erupted materials is known to expand, cool, and form the "umbrella region" of the eruption column (Woods, 1988;Scase, 2009). The most heated fraction of gas-vapor emissions from the convective thrust region has the highest speed and can therefore penetrate through the higher-density umbrella region of the eruption column and reach altitudes higher than H MPA due to the cumulative (jet) effect (Raible et al, 2016).…”

Section: Discussionmentioning

confidence: 99%

30-year lidar observations of the stratospheric aerosol layer state over Tomsk (Western Siberia, Russia)

et al. 2017

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Abstract. There are only four lidar stations in the world which have almost continuously performed observations of the stratospheric aerosol layer (SAL) state over the last 30 years. The longest time series of the SAL lidar measurements have been accumulated at the Mauna Loa Observatory (Hawaii) since 1973, the NASA Langley Research Center (Hampton, Virginia) since 1974, and Garmisch-Partenkirchen (Germany) since 1976. The fourth lidar station we present started to perform routine observations of the SAL parameters in Tomsk (56.48° N, 85.05° E, Western Siberia, Russia) in 1986. In this paper, we mainly focus on and discuss the stratospheric background period from 2000 to 2005 and the causes of the SAL perturbations over Tomsk in the 2006–2015 period. During the last decade, volcanic aerosol plumes from tropical Mt. Manam, Soufrière Hills, Rabaul, Merapi, Nabro, and Kelut and extratropical (northern) Mt. Okmok, Kasatochi, Redoubt, Sarychev Peak, Eyjafjallajökull, and Grímsvötn were detected in the stratosphere over Tomsk. When it was possible, we used the NOAA HYSPLIT trajectory model to assign aerosol layers observed over Tomsk to the corresponding volcanic eruptions. The trajectory analysis highlighted some surprising results. For example, in the cases of the Okmok, Kasatochi, and Eyjafjallajökull eruptions, the HYSPLIT air mass backward trajectories, started from altitudes of aerosol layers detected over Tomsk with a lidar, passed over these volcanoes on their eruption days at altitudes higher than the maximum plume altitudes given by the Smithsonian Institution Global Volcanism Program. An explanation of these facts is suggested. The role of both tropical and northern volcanic eruptions in volcanogenic aerosol loading of the midlatitude stratosphere is also discussed. In addition to volcanoes, we considered other possible causes of the SAL perturbations over Tomsk, i.e., the polar stratospheric cloud (PSC) events and smoke plumes from strong forest fires. At least two PSC events were detected in 1995 and 2007. We also make an assumption that the Kelut volcanic eruption (Indonesia, February 2014) could be the cause of the SAL perturbations over Tomsk during the first quarter of 2015.

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Section: Discussionmentioning

confidence: 99%

30-year lidar observations of the stratospheric aerosol layer state over Tomsk (Western Siberia, Russia)

et al. 2017

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“…where SR cirrus is the cirrus clouds back SR, β a (r), and β m (r) are the backscattering coefficients of aerosols and molecules with respect to the altitude r. Throughout the analysis, a threshold value of SR > 1.5 is maintained for the determination of cirrus clouds (Sandhya et al, 2015). It can be noted that the presence of cirrus can be in the altitude region 10-18 km on many days during January-December 2013.…”

Section: Instrumentation and Data Analysismentioning

confidence: 99%

Lidar Observed Optical Properties of Tropical Cirrus Clouds Over Gadanki Region

Kumar

Venkatramanan

2020

Front. Earth Sci.

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The presence of cirrus cloud has its impact on the earth's radiation budget. In order to study the effect of cirrus clouds in the tropical regions, it is essential to understand, and characterize their optical properties. The optical properties of high altitude cirrus clouds are obtained using the polarization diversity ground based Mie lidar instrument at a tropical latitude station in the Indian subcontinent. Lidar measurements are taken for one year (2013) at National Atmospheric Research Laboratory (NARL), located at Gadanki (13.5 • North, 79.2 • East; 375 m AMSL), India and are used for the present investigation. Altitude variations of optical depth and depolarization ratio are discussed. In the altitude range of 10-17 km, the range of the optical depth and depolarization ratio of cirrus cloud was found to be 0.01-0.4 and 0.1-0.4, respectively. The interdependence of optical depth as a function of depolarization ratio is analyzed and a positive correlation is observed (0.3950). From the measured optical depth values, it is categorized that 8, 77, and 14% of the cirrus clouds are sub-visual, thin, and thick clouds. The monthly and seasonal variations of optical properties of cirrus clouds were analyzed. Summary of cirrus cloud layer statistics and the statistical variation (seasonal) of the optical properties of cirrus clouds is presented for the period of study.

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“…Six encounters in total 90 encounters with ice clouds in the tropical lower stratosphere were observed from Forward Scattering Spectrometer Probe (FSSP-100) and Cloud Imaging Probe (CIP) measurements (De Reus et al, 2009). 5-day lasting SICs at 18.6 km on March 2014 were found over Gadanki from the ground-based Mie lidar observations and space-borne observations (Sandhya et al, 2015). Several cases of ice clouds were discovered above convective anvils reaching up to the lower stratosphere from the Geostationary Operational Environmental Satellite (GOES) and the Next Generation Weather Radar (NEXRAD) program Weather Surveillance Radar-1988 Doppler (WSR-88D) network (Homeyer et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

A global view on stratospheric ice clouds: assessment of processes related to their occurrence based on satellite observations

Zou¹,

Grießbach²,

Hoffmann³

et al. 2022

Preprint

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Abstract. Ice clouds play an important role in regulating water vapor and influencing the radiative budget in the atmosphere. In this study, stratospheric ice clouds (SICs) and stratospheric aerosols from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), deep convection and gravity waves from Atmospheric Infrared Sounder (AIRS) observations and tropopause temperature from ERA5 are analyzed to investigate their long-term variation and processes potentially related to the formation of SICs on the global scale. SICs with cloud top heights 0.25 km above the first tropopause are mainly detected over the tropical continents. SICs associated with the double tropopause events, where the cloud top is between the first and second thermal tropopause, are mostly located in midlatitudes (between 25°–60°). The seasonal cycle and the inter-annual variability of SIC frequencies from 2007 to 2019 show that high SIC frequencies are mainly observed south of the equator from November to March, and at 10° N–20° N from July to September. At mid- and high latitudes, more SICs are observed from December to May in the northern hemisphere and in the southern hemisphere during May to October. Relations between SICs and first tropopause temperature, deep convection, gravity waves, and stratospheric aerosol were analyzed, respectively, on a global scale. Positive correlations between SIC frequencies and deep convection, gravity waves, and stratospheric aerosol and an inverse correlation between SIC frequency and tropopause temperature were observed worldwide. Overlaps of high correlations/anti-correlations were detected over tropical continents, i.e., tropical South America, equatorial Africa, and western Pacific, suggesting a combined effect of tropopause temperature, deep convection, gravity waves, and stratospheric aerosol on SIC occurrence in these regions. Over Central America, North America, the Asian Monsoon, and mid- and high latitudes deep convection and gravity waves present a strong correlation with the occurrence of SICs, individually or interdependently. Regional analyses demonstrated specific relations of tropopause temperature, deep convection, gravity waves, and stratospheric aerosol with SICs at a finer scale. Low tropopause temperature and high occurrence frequency of stratospheric aerosol show strong correlations with high frequencies of SICs over the Indo-Pacific Warm Pool, tropical South America, and equatorial Africa. Deep convection and gravity waves have the strongest correlation with the occurrence frequency of SICs over the Asian Monsoon and the North American Monsoon. Gravity waves and tropopause temperature are highly correlated with SIC occurrence over South America and the northern Atlantic. Moreover, the El Niño phenomenon in 2009–2010 and 2015–2016 coincides with low SIC occurrences over the Indo-Pacific Warm Pool. High stratospheric aerosol loads related to volcanic eruptions (Puyehue-Cordón Caulle and Nabro in 2011) and wildfires (over the United States and Canada in 2017) are closely related to high occurrence frequencies of SICs. We investigated the global distribution and long-term variation of SICs and present a global view of relations between SIC occurrence and tropopause temperature, deep convection, gravity wave activity, and stratospheric aerosol. This work provides a better understanding of the physical processes and climate variability of SICs.

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A case study of formation and maintenance of a lower stratospheric cirrus cloud over the tropics

Cited by 11 publications

References 47 publications

30-year lidar observations of the stratospheric aerosol layer state over Tomsk (Western Siberia, Russia)

30-year lidar observations of the stratospheric aerosol layer state over Tomsk (Western Siberia, Russia)

Lidar Observed Optical Properties of Tropical Cirrus Clouds Over Gadanki Region

A global view on stratospheric ice clouds: assessment of processes related to their occurrence based on satellite observations

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