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The diel vertical variations of chlorophyll a (Chl-a) concentration are thought of primarily as an external manifestation of regulating phytoplankton's biomass, which is essential for dynamically estimating the biogeochemical cycle in inland waters. However, information on these variations is limited due to insufficient measurements. Undersampled observations lead to delayed responses in phytoplankton assessment, impacting accurate evaluations of carbon export and water quality in dynamic inland waters. Here, we report the first lidar-observed diel vertical variations of inland Chl-a concentration. Strong agreement with r2 of 0.83 and a root mean square relative difference (RMSRD) of 9.0% between the lidar-retrieved and in situ measured Chl-a concentration verified the feasibility of the Mie–fluorescence–Raman lidar (MFRL). An experiment conducted at a fixed observatory demonstrated the lidar-observed diel Chl-a concentration variations. The results showed that diel variations of Chl-a and the formation of subsurface phytoplankton layers were driven by light availability and variations in water temperature. Furthermore, the facilitation from solar radiation-regulated water temperature on the phytoplankton growth rate was revealed by the high correlation between water temperature and Chl-a concentration anomalies. Lidar technology is expected to provide new insights into continuous three-dimension observations and be of great importance in dynamic inland water ecosystems. [ABSTRACT FROM AUTHOR]

A dual-wavelength high-spectral-resolution lidar (HSRL) based on an iodine absorption filter and a field-widened Michelson interferometer (FWMI) has been developed to profile backscatter and extinction coefficients of aerosols and clouds accurately. This instrument was tested and calibrated on multiple observations in Hangzhou and Zhoushan, respectively, from August 2018 to April 2019. This paper discusses the design and the internal calibration method of the lidar system in detail, with several typical cases of observations and the analysis of these data products. The optical properties of urban aerosols in Hangzhou and the evolvement of clouds in Zhoushan are presented, respectively.

Study on the upper ocean is of great significance to the global climate change and carbon cycle. Lidar can be used to effectively detect depth-resolved optical properties of the ocean. However, both theory and experiment of oceanic lidar are limited by complex multiple scattering. Several progresses by Zhejiang University will be illustrated in this paper: 1) a polarized lidar system was developed, and a Monte Carlo model and a radiative transfer model were established (Zhou, et al. remote sensing, 2019; Zhou, et al. Journal of remote sensing, 2019; Xu, et al. and Liu, et al. Journal of remote sensing, 2019); 2) Cross validations are demonstrated to verify the availability of the lidar system and models (Liu, et al. IEEE TGRS, 2019); 3) phase function effects on backscatter and attenuation are studied considering multiple scattering, respectively (Liu, et al. Optics Express, 2019). Oceanic lidar is proven to have great potential in marine studies.

This paper presents two approaches to calibrate the overlap factor under inhomogeneous atmospheric condition without critical assumption and delivers detailed analysis about the retrieval errors of overlap profile in High-Spectral-Resolution-Lidar (HSRL). The first method employs an additional optical subsystem with different field-of-view, that is dual field-of-view HSRL, for the retrieval of overlap profile. The second method takes advantage of the difference of the result between the HSRL and Klett method, that is about the retrieval of backscatter coefficient for uncorrected lidar signal, to correct overlap profile. Surprisingly, two methods show very high-level consistency and stability of the result. It is potential that this technique would be an excellent solution for experimental determination of lidar overlap in ground-based HSRL.

Multiple scattering is an inevitable effect in spaceborne oceanic lidar because of the large footprint size and the high optical density of seawater. The effective attenuation coefficient klidar in oceanic lidar equation, which indicates the influence of the multiple scattering effect on the formation of lidar returns, is an important parameter in the retrieval of inherent optical properties (IOPs) of seawater. In this paper, the nonlinearity of klidar and the relationships between klidar and the IOPs of seawater are investigated by solving the radiative transfer equation with an improved semianalytic Monte Carlo model. klidar is found to decrease exponentially with the increase of depth in homogeneous waters. klidar is given as an exponential function of depth and IOPs of seawater. The results in this paper can help to have a better understanding of the multiple scattering effect of spaceborne lidar and improve the retrieval accuracy of the IOPs of seawater using spaceborne lidar.

The lidar ratio of seawater is an essential quantity related to both lidar retrieval and water constituent. However, few studies discuss its spatial–temporal characteristics and ecological significance, which limits its applications in lidar remote sensing and marine science. This paper investigates the spatial–temporal characteristics and ecological significance of the lidar ratio of seawater using satellite passive remote sensing, which is validated by in situ measurements. Spatially, nearshore lidar ratio values are higher than offshore, mainly owing to the high concentration of colored dissolved organic matter in nearshore water. Temporally, the lidar ratio in each hemisphere exhibits lower values in summer than in winter due to the annual boom–bust cycle of phytoplankton. Furthermore, the variability patterns of the lidar ratio are nearly consistent with those of the chlorophyll-to-carbon ratio, implying the high ecological significance of phytoplankton physiology. These findings will provide the foundation for the application of lidar ratio in marine science and lidar remote sensing. [ABSTRACT FROM AUTHOR]

Tidal stream turbines may operate under yawed conditions due to variability in ocean current directions. Insight into the wake structure of yawed turbines can be essential to ensure efficient tidal stream energy extraction, especially for turbine arrays where wake interactions emerge. We studied experimentally the effects of turbines operating under varying yaw conditions. Two scenarios, including a single turbine and a set of two turbines in alignment, were configured and compared. The turbine thrust force results confirmed that an increasing yaw angle results in a decrease in the turbine streamwise force and an increase in the turbine spanwise force. The velocity distribution from the single turbine scenario showed that the wake deflection and velocity deficit recovery rate increased at a rate proportional to the yaw angle. The two-turbine scenario results indicated that the deployment of an upstream non-yawed turbine significantly limited the downstream wake steering (i.e., the wake area behind the downstream turbine). Interestingly, a yawed downstream turbine was seen to influence the steering of both the upstream and the downstream wakes. These systematically derived data could be regarded as useful references for the numerical modelling and optimisation of large arrays. [ABSTRACT FROM AUTHOR]

The thin layers in the ocean are temporally-coherent aggregations of phytoplankton with high concentrations at small vertical scales, presenting important hotspots of ecological activity. Lidar could identify thin phytoplankton layers at a large spatial scale due to its capabilities of profile detection with a high efficiency. However, studies that linked thin layers to environmental factors are few, which limits our understanding of the layer formation mechanism. This paper investigates the characteristics and formation conditions of thin phytoplankton layers in the northern Gulf of Mexico using airborne lidar. The results depict that the chlorophyll concentration determines the formation probability of the phytoplankton layer. The layer is mainly formed at concentrations less than 6 mg m−3 and mostly distributed at 2 mg m−3. In addition, layer thicknesses were within 5 m and layer depths were mainly in the range of 10–15 m. Layer depths in the nearshore region were shallower than those in the offshore region. We conclude that the characteristics and formation conditions of the thin phytoplankton layers depend on the nutrients and light that are related to the seabed topography, turbidity, eddies and upwelling. The findings of this paper will enhance the understanding of layer formation mechanisms. [ABSTRACT FROM AUTHOR]

aimed to investigate the effects of preoperative EA on RPH in patients undergoing thyroidectomy. Methods: A total of 80 patients who were scheduled to undergo elective thyroidectomy were randomly assigned to two groups: an EA group and a sham EA (SEA) group. EA was delivered at the Zusanli (ST36) and Neiguan (PC6) acupoints 24 h before the surgery. To ensure uniformity across all patients, remifentanil was administered at the same set rate (0.3 μg/kg/min) to all patients. Mechanical pain thresholds were recorded by an electronic von Frey device around the skin incision and on the arm before surgery as well as at 30 min and 6, 24, and 48 h after surgery. Results: At 30 min and 6 h after surgery, the EA group showed considerably greater mechanical pain thresholds surrounding the surgical site compared with the SEA group. At 30 min and 6 h after surgery, the patients in the SEA group showed a greater incidence of postoperative hyperalgesia surrounding the surgical site than those in the EA group. At 24 and 48 h after surgery, no significant differences were found between the two groups, although the pain intensity of the EA group was less than that of the SEA group. There were also no substantial differences between the two groups in the frequency of postoperative adverse reactions and rescue analgesia needed. Conclusion: EA administered 24 h before surgery could alleviate RPH in patients undergoing thyroidectomy. [ABSTRACT FROM AUTHOR]

Intracerebral neuroinflammation, closely related to brain mast cell (MC) activation, performs an integral function in the pathogenic process of postoperative cognitive dysfunction (POCD). In addition to regulating cognitive activities, the alpha-7-nicotinic acetylcholine receptor (α7nAChR) engages in the progression of cognitive deficiency. In this research, we aimed to investigate how electroacupuncture (EA) affects the cognitive function in rats after tibial fracture surgery to determine whether the underlying mechanism involves the inhibition of hippocampal MC degranulation via α7nAChR. A rat model of tibial fracture surgery for inducing POCD was developed and subjected to treatment with EA or the α7nAChR antagonist α-bungarotoxin (α-BGT) and the α7nAChR agonist PHA-543613. The spatial memory tasks in the Morris Water Maze (MWM) test showed that both EA and PHA-543613-treated rats performed significantly better than untreated rats, with reduced escape latency and increased frequency of passage through the platform. However, EA and PHA-543613 intervention decreased the protein and mRNA levels of High-mobility group box-1(HMGB-1) and proinflammatory cytokines tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) in the serum and hippocampus, respectively, by upregulating α7nAChR in the hippocampus. Furthermore, EA and PHA-543613 pretreatment reduced the number of activated MCs and suppressed neuronal apoptosis after tibial fracture surgery in the hippocampal CA1 regions, which was reversed by α-BGT. The findings indicated that EA pretreatment ameliorated POCD after tibial fracture surgery in rats by inhibiting brain MC activation and neuroinflammation mediated by the α7nAChR-dependent cholinergic anti-inflammatory system. [ABSTRACT FROM AUTHOR]

Cerebral ischemia/reperfusion (I/R) injury can induce the mitophagy of neurons in the ischemic brain. Electroacupuncture (EA) pretreatment has a protective effect on cerebral ischemia/reperfusion injury. However, its internal mechanism still needs to be further studied. The present study's purpose is to investigate whether mitophagy is involved in neuroprotection elicited by EA pretreatment in a rat model of cerebral ischemia/reperfusion injury. The rats were pretreated with vehicle, EA at the Baihui (GV20) and Shuigou (GV26) acupoints 30 min daily, for 5 days consecutively prior to the focal cerebral ischemia injury induced by the middle cerebral artery occlusion (MCAO) model. Compared to the sham group, the neurological scores, infarction volume, number of autophagosomes, FUNDC1, p62, and the ratio of LC3-II/I were significantly increased but mitochondrial membrane potential and autophagy-related protein p-mTORC1 significantly decreased in the I/R group. However, EA pretreatment significantly reversed these trends. Overall, the results of this study demonstrated that EA pretreatment protected the cerebral ischemia/reperfusion injury which maybe correlated with mitophagy. [ABSTRACT FROM AUTHOR]

Detecting the vertical profile of optical properties is an important task in the remote sensing of the upper ocean, especially for 3-D reconstruction. Ocean color remote sensing can only provide surface information, while the light detection and ranging (lidar) technique can provide depth-resolved data. Lidar can provide global-scale observations of the upper ocean for days and nights with minimal atmospheric correction errors. Unfortunately, due to the strong multiple scattering effects that occur when light propagates in seawater, the simple lidar equation may cause some deviations between the actual measurements and the simulation of the lidar signals. In this paper, we present a shipborne oceanic lidar, which was developed to detect the optical properties of seawater. For evaluating the performance of the lidar system, a Monte Carlo (MC) model was established to simulate lidar signals based on the simultaneous in situ inherent optical properties of seawater. The lidar measurements and the MC simulation can provide both the lidar signals and the retrieved lidar attenuation coefficient $\alpha $. The results of the comparison indicate that the lidar-measured signals correspond well with the MC-simulated signals at different experiment stations in the Yellow Sea and at various receiving fields of view (FOVs). We also observed strong correlations between the lidar-measured $\alpha $ and MC-simulated $\alpha $ at different stations ($r = 0.95$) and at various FOVs ($r = 0.96$). The results indicate the reliability of the developed lidar system. [ABSTRACT FROM AUTHOR]

We propose a novel technique for simultaneous multi-impairment monitoring and autonomous bit-rate and modulation format identification (BR-MFI) in next-generation heterogeneous fiber-optic communication networks by using principal component analysis-based pattern recognition on asynchronous delay-tap plots. The results of numerical simulations performed for three commonly used modulation formats at two different bit-rates each demonstrate simultaneous and independent monitoring of optical signal-to-noise ratio, chromatic dispersion, and differential group delay with mean errors of 1 dB, 4 ps/nm, and 1.6 ps, respectively, without knowing the signal's bit-rate and modulation format. Similarly, the results for joint BR-MFI validate accurate identification of all the bit-rates and modulation formats despite the presence of various network impairments. The effects of fiber nonli-nearity and transmitter variations on the performance of the proposed technique are also investigated. [ABSTRACT FROM PUBLISHER]

To overcome the retrieval problems in complex water, dual working wavelengths are required instead of a single wavelength in oceanic lidar. The wavelength optimization method of detecting chlorophyll a and Colored Dissolved Organic Matter (CDOM) absorption coefficient with a dual-wavelength lidar is studied in this paper. The inversion methods of chlorophyll a and CDOM absorption are developed based on the water absorption characteristics, which then lead to the inversion error equations. The effects of the wavelength on the inversion errors are studied. For the case in which λ1 and λ2 are both random, the errors are relatively small when λ1 is chosen between 420 and 560 nm and λ2 is selected under 420 nm. For the case in which λ1 is fixed at 532 nm, the errors generally decrease with decreasing λ2, with minimums around 300 and 356–360 nm under different water conditions. The wavelength optimization method discussed in this paper and the penetration depth criterion will be beneficial to the design of the dual-wavelength lidar. [ABSTRACT FROM AUTHOR]

The analytical model based on the quasi-single small-angle scattering approximation can efficiently simulate oceanic lidar signals with multiple scattering; thus, its accuracy is of particular interest to scientists. In this paper, the model is modified to include refraction at oblique incidence and is then compared with Monte Carlo (MC) simulations and experimental results. Under different conditions, the results calculated by the analytical model demonstrate good agreement with the MC simulation and experimental data. The coefficient of determination R2 considering the logarithm of signals and the root mean square of the relative difference δ are R2 = 0.998 and δ = 10% in comparison with the semi-analytic MC simulation and R2 = 0.952 and δ = 46% for the lidar experiment. Thus, the results demonstrate the validity of the analytical model in the simulation of oceanic lidar signals. [ABSTRACT FROM AUTHOR]

Cardiac dysfunction is a critical event during sepsis/septic shock. Tanshinone IIA (TIIA), a compound extracted from herb medicine Danshen, has been shown possessing anti-inflammatory and anti-oxidative properties. It is possible, therefore, that treatment with TIIA may attenuate cardiac dysfunction during sepsis/septic shock through inhibition of inflammation. To test this possibility, we preadministrated C57BL/6 mice with TIIA prior to lipopolysaccharide (LPS) challenge. LPS significantly suppressed left ventricular function as evidenced by decreases in EF% and FS% in mice. However, TIIA pretreatment significantly attenuated cardiac dysfunction following LPS challenge. Furthermore, TIIA markedly attenuated the LPS-induced upregulation of circulating tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) levels. Meanwhile, LPS challenge significantly increased myocardial reactive oxygen species (ROS) production, which was attenuated by TIIA. Moreover, TIIA treatment dramatically decreased the level of the Nox2, reduced phosphorylation levels of extracellular signal-regulated kinase 1/2 (ERK1/2) and p38 mitogen-activated protein kinase (p38 MAPK) expression. In conclusion, TIIA effectively improves cardiac function during endotoxemia in mice. This is attributed to TIIA reducing inflammatory cytokines release and inhibiting the Nox2 signaling during endotoxemia. [ABSTRACT FROM AUTHOR]

Myocardial fibrosis plays a central role in the development of heart failure. It has been shown that recurrent exposure to subclinical lipopolysaccharide (LPS) increases mortality and induces cardiac fibrosis in mice, which is not mediated by the common renin-angiotensin system. LPS increased NADPH oxidase2 (NOX2) in isolated adult mouse cardiac fibroblasts and NOX2 may mediate LPS-induced cardiac fibrosis. Therefore, the current study was designed to delineate the role of NOX2 in LPS-induced fibrosis model and to investigate the preventive role of Tanshinone IIA (TIIA) on the development of cardiac fibrosis. The protective mechanism of TIIA was determined to be associated with the inhibition of NOX2, by comparing its effects with the NADPH oxidase inhibitor, apocynin. The results revealed remarkable effects of apocynin and TIIA on attenuating the development of myocardial fibrosis and fibrosis-related genes and mediators. Furthermore, TIIA and apocynin decreased the expression of NADPH oxidase subunits (NOX2 and P67 phox ) expression and the ROS levels. The anti-fibrotic effect of apocynin suggested that NOX2 inhibition may be a potential preventive strategy for attenuating the progression of LPS-induced cardiac fibrosis. Our results demonstrate that TIIA may be a potent agent against subclinical LPS-induced cardiac fibrosis in mice partially via inhibition of NADPH oxidase 2. [ABSTRACT FROM AUTHOR]

We propose a novel technique for automatic classification of modulation formats/bit-rates of digitally modulated signals as well as non-data-aided (NDA) estimation of signal-to-noise ratio (SNR) in wireless networks. The proposed technique exploits modulation format, bit-rate, and SNR sensitive features of asynchronous delay-tap plots (ADTPs) for the joint estimation of these parameters. Simulation results validate successful classification of three commonly-used modulation formats at two different bit-rates with an overall accuracy of 99.12%. Similarly, in-service estimation of SNR in the range of 0−30 dB is demonstrated with mean estimation error of 0.88 dB. The proposed technique requires low-speed asynchronous sampling of signal envelope and hence, it can enable simple and cost-effective joint modulation format/bit-rate classification and NDA SNR estimation in future wireless networks. [ABSTRACT FROM AUTHOR]

Background and Aims: Exosome-based therapies are gaining increasing attention, with growing evidence suggesting a link between alterations in mesentery adipose tissue (MAT) and intestinal disease in Crohn's disease (CD). However, the specific mechanism by which mesenchymal stem cells (MSCs)-Exos may alleviate colitis through targeting MAT remains not fully understood., Methods: Human umbilical cord MSCs (HucMSCs) were cultured to isolate the corresponding exosomes (HucMSCs-Exos), which were confirmed by their morphology, size distribution, and expression of markers. In vivo, 2,4,6-trinitrobenzenesulfonic acid solution (TNBS) and dextran sodium sulfate (DSS) -induced mouse colitis models were used to detect the therapeutic effects of HucMSCs-Exos. ELISA, qRT-PCR, western blotting, and immunofluorescence determined the expression of key molecules. Luciferase reporter assay was used to confirm the relationship between miR-21-5p and SPRY2., Results: Exosomes treatment through mesenteric injection demonstrated therapeutic effects on mesenteric inflammation and colitis. These therapeutic benefits were contingent on macrophages, significantly facilitating the M2 polarization of mesenteric macrophages. The expression data from GSE159814 and GSE211008 revealed that exosomal miR-21-5p was enriched in HucMSCs-Exos and could be delivered to macrophages. Additionally, the results indicated that miR-21-5p could directly target the 3'UTR of SPRY2 and activate the phosphorylation of ERK to modify macrophage phenotypes. Mechanistically, exosomal miR-21-5p derived from HucMSCs could promote macrophage M2 polarization via the SPRY2/ERK axis., Conclusion: Mesenteric injection of HucMSCs-Exos significantly alleviates mesenteric inflammation and colitis by promoting mesenteric macrophage M2 polarization, making it a promising approach to treat colitis and suggesting therapeutic potential role of exosomal miR-21-5p in CD., (© The Author(s) 2024. Published by Oxford University Press on behalf of European Crohn’s and Colitis Organisation. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Measuring the characteristics of seawater constituent is in great demand for studies of marine ecosystems and biogeochemistry. However, existing techniques based on remote sensing or in situ samplings present various tradeoffs with regard to the diversity, synchronism, temporal-spatial resolution, and depth-resolved capacity of their data products. Here, we demonstrate a novel oceanic triple-field-of-view (FOV) high-spectral-resolution lidar (HSRL) with an iterative retrieval approach. This technique provides, for the first time, comprehensive, continuous, and vertical measurements of seawater absorption coefficient, scattering coefficient, and slope of particle size distribution, which are validated by simulations and field experiments. Furthermore, it depicts valuable application potentials in the accuracy improvement of seawater classification and the continuous estimation of depth-resolved particulate organic carbon export. The triple-FOV HSRL with high performance could greatly increase the knowledge of seawater constituents and promote the understanding of marine ecosystems and biogeochemistry., (Copyright © 2023 Kai Zhang et al.)

Background: The impact of chronic kidney disease (CKD) on adverse cardiovascular outcomes after percutaneous coronary intervention in patients with diabetes mellitus (DM) is still unclear. This study aimed to systematically assess evidence on this topic., Methods: The PubMed, Embase, and CENTRAL databases were searched for studies comparing mortality, myocardial infarction (MI), or revascularization outcomes between patients with DM with and without CKD., Results: In 11 studies, the presence of CKD was associated with significantly increased risk of early all-cause mortality (risk ratio [RR], 3.45; 95% CI, 3.07-3.87; I2 = 0%; P < .001), late all-cause mortality (RR, 2.78; 95% CI, 1.92-4.02; I2 = 83%; P < .001), cardiac mortality (RR, 2.90; 95% CI, 1.99-4.22; I2 = 29%; P < .001), and MI (RR, 1.40; 95% CI, 1.06-1.85; I2 = 13%; P = .02) compared with no CKD. There was no difference in the risk of any revascularization between those with and without CKD. Analysis of adjusted hazard ratios (HRs) indicated significantly increased risk of mortality (HR, 2.64; 95% CI, 1.91-3.64; I2 = 0%; P < .001) in the CKD group but only a nonsignificant tendency of increased MI (HR, 1.59; 95% CI, 0.99-2.54; I2 = 0%; P = .05) and revascularization (HR, 1.24; 95% CI, 0.94-1.63; I2 = 2%; P = .12) in the CKD group., Conclusion: The presence of CKD in patients with DM significantly increases the risk of mortality and MI. However, CKD had no impact on revascularization rates., (© 2023 by the Texas Heart® Institute, Houston.)

SignificanceAerosol-cloud interaction affects the cooling of Earth's climate, mostly by activation of aerosols as cloud condensation nuclei that can increase the amount of sunlight reflected back to space. But the controlling physical processes remain uncertain in current climate models. We present a lidar-based technique as a unique remote-sensing tool without thermodynamic assumptions for simultaneously profiling diurnal aerosol and water cloud properties with high resolution. Direct lateral observations of cloud properties show that the vertical structure of low-level water clouds can be far from being perfectly adiabatic. Furthermore, our analysis reveals that, instead of an increase of liquid water path (LWP) as proposed by most general circulation models, elevated aerosol loading can cause a net decrease in LWP.

Seawater properties can be retrieved from oceanic lidar returns. However, the actual returns include the ideal returns convolved by the instrument response, which inevitably introduces retrieval error. In this paper, instrument response effects on the retrieval of oceanic lidar are analyzed from different aspects. The results demonstrate that the retrieval of the lidar attenuation coefficient near the water surface is affected by the instrument response in homogeneous water. Considering the ratio of the signal distortion region (relative error of attenuation >10 % ) to the maximum detection depth (three dynamic ranges) is less than 20%, the pulse width of the instrument response should be less than 10 -0.042( K d ) -2 +0.709( K d ) -1 +1.136 n s . In addition, an average relative error of 55% will be introduced to the retrieval of phytoplankton layer thickness in the stratified water, which can be reduced to 6% after correcting for the influence of the instrument response. However, a relative error greater than 20% still exists when the instrument response length is two times larger than the layer thickness. These conclusions provide guidelines to a future design of oceanic lidar.

In this paper, a high-spectral-resolution lidar (HSRL) for profiling atmospheric temperature from the ground to 10 km is proposed. A double Nd:YAG laser produces the transmitted laser at 532 nm. The backscattering lidar signal is passed through two different saturated iodine-vapor filters and thus obtains molecular scattering signals that can be employed to determine the temperature. A coaxial postposition transceiver is constructed with an off-axis aspheric reflective telescope (OART). The design of the transceiver and that of the OART are demonstrated. With this transceiver, the lidar blind zone where the overlap factor is zero can be reduced greatly, and accurate temperature measurement for full elevation can be achieved. The whole system is optimized with theoretical models based on geometrical optics and statistical error analyses. Monte Carlo simulations display the performance of the designed HSRL, showing that the all-day temperature retrieval error is better than 1.4 K from the ground to 10 km. The proposed HSRL is expected to provide more accurate atmospheric auxiliary parameters for the detection of aerosols' optical characteristics.

The return spectrum of the oceanic high-spectral-resolution lidar (HSRL) is simulated with a semianalytic spectral Monte Carlo (MC) method. The results show that the spectrum is similar to the single scattering spectrum at the water surface but broadens with the depth due to multiple scattering. Therefore, if the non-spectral MC method that ignores the spectrum broadening is used, deviations will be introduced into the HSRL retrieval, e.g., the effective particulate 180° volume scattering function (backscatter) and lidar attenuation coefficient (attenuation). The simulation indicates that the backscatter and attenuation deviations are within 10% and 2%, respectively, when the HSRL discriminator is the iodine absorption cell, and are within 3% and 1%, respectively, when the discriminator is changed to the field-widened Michelson interferometer.

A semianalytic Monte Carlo model is developed to simulate oceanic high-spectral-resolution lidar (HSRL) signals with multiple scattering. The phase function effects on oceanic HSRL retrieval are studied, e.g., the effective particulate 180° volume scattering function (VSF) and lidar attenuation coefficient that describe characteristics of backscatter and attenuation, respectively. The results demonstrate that the particulate backward and forward phase functions both have a significant influence on δ 1 , which is the relative difference between the effective and true particulate 180° VSF. The values of |δ 1 | are typically quite small for all phase functions at the water surface and increase with depth up to ~17% for the Fournier and Forand (FF) phase function but up to ~40% for the two-term Henyey-Greenstein (TTHG) phase function and ~75% for the one-term Henyey-Greenstein (OTHG) phase function. The reason that δ 1 is not zero is due to broadening of backscattering angles from 180° caused by multiple scattering and uneven backward phase function. Also, the reason that maximum TTHG and OTHG |δ 1 | are larger than FF is due to less sharply increasing feature of FF in the backward direction. In addition, the particulate forward phase functions are closely related to δ 2 , which is the relative deviation between the lidar attenuation coefficient and the sum of the absorption and backscattering coefficients. The values of δ 2 are small for all phase functions at the water surface and increase with depth up to ~12% for TTHG but up to ~26% for FF and ~31% for OTHG, due to the less peaked forward phase functions that result in more angular spread of the beam with depth and therefore result in less photons within the field of view of the lidar.

Multiple scattering is an inevitable effect in spaceborne oceanic lidar because of the large footprint size and the high optical density of seawater. The effective attenuation coefficient klidar in the oceanic lidar equation, which indicates the influence of the multiple scattering effect on the formation of lidar returns, is an important parameter in the retrieval of inherent optical properties (IOPs) of seawater. In this paper, the relationships between klidar of the spaceborne lidar signal and the IOPs of seawater are investigated by solving the radiative transfer equation with an improved semianalytic Monte Carlo model. Apart from the geometric loss factors, klidar is found to decrease exponentially with the increase of depth in homogeneous waters. klidar is given as an exponential function of depth and IOPs of seawater. The mean percentage errors between klidar calculated by the exponential function and the simulated ones in three typical stratified waters are within 0.5%, proving the effectiveness and applicability of this klidar-IOPs function. The results in this paper can help researchers have a better understanding of the multiple scattering effect of spaceborne lidar and improve the retrieval accuracy of the IOPs and the chlorophyll concentration of case 1 water from spaceborne lidar measurements.

A high-spectral-resolution lidar (HSRL) is proposed to retrieve the seawater volume scattering function at the 180° scattering angle βπ without the assumption of the lidar extinction-to-backscatter ratio. A field-widened Michelson interferometer is employed as the ultra-narrow spectral discriminator to reject particulate scattering and molecular Rayleigh scattering but transmit molecular Mandelshtam-Brillouin scattering. The theoretical framework to retrieve βπ is presented in detail based on a dual-channel HSRL configuration. Simulation on the retrieval and error estimation shows that, the proposed oceanographic HSRL based on the ship or aircraft can perform well to extract the profile of βπ and has a real potential in the oceanographic remote sensing.