First Observations of Cirrus Clouds Using the UZ Mie Lidar over uMhlathuze City, South Africa

Mbatha, Nkanyiso; Shikwambana, Lerato

doi:10.3390/app12094631

Cited by 3 publications

(1 citation statement)

References 26 publications

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“…The system primarily measures the backscatter signal of atmospheric molecules, but there are inevitably aerosols and clouds present in the atmosphere, such as the stratospheric aerosol layer around 20 km, and the cirrus in the upper troposphere [26][27][28]. Therefore, the impact of Mie signals on wind measurement must be considered.…”

Section: For Rayleigh-mie Backscattering Signalsmentioning

confidence: 99%

The Impacts of Deformed Fabry–Perot Interferometer Transmission Spectrum on Wind Lidar Measurements

Zhao,

Chen,

Xie

et al. 2024

Remote Sensing

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The Fabry–Perot interferometer (FPI) plays a crucial role as the frequency discriminator in the incoherent Doppler wind lidar. However, in the practical receiver system, reflections occurring between optical elements introduce non-normal incident components in the light beams passing through the FPI. This phenomenon results in the deformation of the FPI transmission spectral lines. Based on that, a theoretical model has been developed to describe the transmission spectrum of the FPI when subjected to obliquely incident light beams with a divergence angle. By appropriately adjusting the model parameters, the simulated transmission spectrum of the FPI edge channels can coincide with the experimentally measured FPI spectral line. Subsequently, the impact of deformations in the transmission spectrum of the two edge channels on wind measurements is evaluated. The first implication is a systematic shift of 30.7 m/s in line-of-sight (LOS) wind velocities. This shift is based on the assumption that the lidar echo is solely backscattered from atmospheric molecules. The second consequence is the inconsistency in the response sensitivities of Doppler frequency shift between Rayleigh signals and Mie signals. As a result, the lidar system fails to fully achieve its initial design objectives, particularly in effectively suppressing interference from Mie signals. The presence of aerosols can introduce a significant error of several meters per second in the measurement of LOS wind velocity.

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Section: For Rayleigh-mie Backscattering Signalsmentioning

confidence: 99%

The Impacts of Deformed Fabry–Perot Interferometer Transmission Spectrum on Wind Lidar Measurements

Zhao,

Chen,

Xie

et al. 2024

Remote Sensing

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Seasonal distribution of cirrus cloud characteristics and their rapid descent from polarization lidar measurements at the west coast of India

Aswini

Ruchith

Das

et al. 2023

Theor Appl Climatol

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Cirrus clouds are highly re ective clouds that play an important role in the atmospheric radiative balance and hence contribute to climate change. We present seasonal distribution of cirrus cloud occurrence, their characteristics and evolution over a coastal station (Goa, 15.4 o N, 73.8 o E, 40m above MSL) in India, using ground-based Micro Pulse lidar and Vaisala radiosonde observations from July 2013 to June 2015.The frequency of cirrus occurrence was observed around 44%, 33%, 17% and 6% in winter (JF), premonsoon (MAM), south west monsoon (JJAS) and post-monsoon (OND) respectively. Thicker cirrus were more frequent in September with an average value of > 1.7 ± 0.89 Km. The frequency of cirrus descent occurs almost similar in monsoon and post-monsoon (42% and 43% respectively) months. Two extreme cirrus descending cases were observed during the monsoon: (1) on 22 August 2014 with a displacement of 9.6 km from the initial height of 14 km with a descending rate and geometrical thickness of 0.4 ms − 1 and 1.5 km respectively; (2) on 14 September 2013 with a displacement of 7.8 km with descending rate and thickness of 0.2 ms − 1 and 2.3km respectively. Relatively high humidity (> 60%) and low (<-20 o C) ambient temperature caused thick cirrus formation in September 2013. However, during August 2014 event, relatively thinner (optically) cirrus was observed and the same is attributed to lower humidity conditions (45 to 60%). The wind shear associated with the tropical easterly jet (TEJ) appears to play a major role in cirrus displacement by modifying their vertical velocity. The positive and negative vertical velocity elds cause cirrus to a descending shape. The gradual descending pattern of cirrus is moving parallel to the vertical velocity contour, while the rapid descending in 2014 was mainly due to the occurrence of cirrus perpendicular to the velocity contour. Overall, this study represents the descending nature of cirrus clouds and their impact on the surface radiative characteristics over a coastal station in India.

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Selenium efficiency in protecting sperm quality and testicular parameters of South African indigenous Zulu rams exposed to heat stress

Lekola,

Ngcobo,

Lehloenya

2024

Trop Anim Health Prod

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The study investigated selenium’s (Se) efficiency in preserving South African Zulu rams’ sperm quality and testicular parameters when they were exposed to heat stress. Indigenous Zulu rams (20) between 2 and 5 years old were allocated into four groups, namely the Se, testicular heat stress (THS), selenium plus testicular heat stress (SeTHS), and control. Each group comprised five rams; the groups were balanced according to the rams’ body weight and scrotal circumference. The Se and SeTHS groups received sodium selenite orally bi-weekly for 5 months. To induce heat stress, testicular heat insulation bags were wrapped around the testes of the rams receiving the THS and SeTHS treatments for 49 days. Semen was collected from the rams weekly from the third month onward; the first two months were for Se & THS acclimatization. In addition, testicular measurements were taken bi-weekly. Analysis of variance was used to analyze the sperm quality data. Duncan’s multiple range test was used to compare the groups’ data for significant differences. The results showed that the Se-supplemented rams’ scrotal circumference was smaller (p < 0.05) compared with the other groups. The Se, SeTHS, and control groups demonstrated similar total sperm motility; in contrast, the THS and SeTHS groups recorded low and high total sperm motility, respectively, compared with other treatment groups (p < 0.05). The semen from the rams that received THS without Se displayed a significantly higher number of immotile sperm cells (p < 0.05) and poor sperm quality, including total and progressive motility, and kinematic parameters when compared with other treatments, suggesting that Se protects sperm against THS. We concluded that selenium protected some sperm parameters (TSM, PSM, MV, VCL, VSL) of THS- treated rams while others did not improve (RV, NSM, C, STR).

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First Observations of Cirrus Clouds Using the UZ Mie Lidar over uMhlathuze City, South Africa

Cited by 3 publications

References 26 publications

The Impacts of Deformed Fabry–Perot Interferometer Transmission Spectrum on Wind Lidar Measurements

The Impacts of Deformed Fabry–Perot Interferometer Transmission Spectrum on Wind Lidar Measurements

Seasonal distribution of cirrus cloud characteristics and their rapid descent from polarization lidar measurements at the west coast of India

Selenium efficiency in protecting sperm quality and testicular parameters of South African indigenous Zulu rams exposed to heat stress

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