The accuracy of cosmic ray observations by the Large High Altitude Air Shower Observatory Wide Field-of-View Cherenkov/Fluorescence Telescope Array (LHAASO-WFCTA) is influenced by variations in aerosols in the atmosphere. The solar photometer (CE318-T) is extensively utilized within the Aerosol Robotic Network as a highly precise and reliable instrument for aerosol measurements. With this CE318-T 23, 254 sets of valid data samples over 394 days from October 2020 to October 2022 at the LHAASO site were obtained. Data analysis revealed that the baseline Aerosol Optical Depth (AOD) and Ångström Exponent (AE) at 440–870 nm (AE440–870nm) of the aerosols were calculated to be 0.03 and 1.07, respectively, suggesting that the LHAASO site is among the most pristine regions on Earth. The seasonality of the mean AOD is in the order of spring > summer > autumn = winter. The monthly average maximum of AOD440nm occurred in April (0.11 ± 0.05) and the minimum was in December (0.03 ± 0.01). The monthly average of AE440–870nm exhibited slight variations. The seasonal characterization of aerosol types indicated that background aerosol predominated in autumn and winter, which is the optimal period for the absolute calibration of the WFCTA. Additionally, the diurnal daytime variations of AOD and AE across the four seasons are presented. Our analysis also indicates that the potential origins of aerosol over the LHAASO in four seasons were different and the atmospheric aerosols with higher AOD probably originate mainly from Northern Myanmar and Northeast India regions. These results are presented for the first time, providing a detailed analysis of aerosol seasonality and origins, which have not been thoroughly documented before in this region, also enriching the valuable materials on aerosol observation in the Hengduan Mountains and Tibetan Plateau.

The microphysical properties of supercooled liquid droplets (SLDs) and ice particles of stratiform mixed-phase clouds over Eastern China are characterized using carefully post-processed airborne data. The majority of sampled clouds were precipitating with ice particles and were frequently mixed with SLDs at cold temperature. While the concentration of large ice crystal (> 600 mu m in diameter, the same below) was low (up to 3 L-1), the concentration of smaller ice particle (> 50 mu m) was high (up to 300 L-1). Such particles with high concentration cannot be a result of the recirculation of pre-existing aged ice and thus secondary ice production (SIP) was likely occurring over the stratiform clouds at temperatures between-16.9 degrees C and-6.4 degrees C. The statistical analyses show that concentrations of tiny, hexagonal and irregular ice crystals were significantly greater in updraft than those in downdraft regions, suggesting that updrafts not only provide a favorable environment for the growth of cloud particles, but also promote the multiplication of the above young-age small ice (50-100 mu m) where SIP is commonly occurring. Since the criteria for the other SIP mechanisms are difficult to meet for this light-riming stratiform without deep convections, this analysis indicates that shattering during droplet freezing might thus be an important SIP source at temperatures between-15 degrees C and-9 degrees C. This study should provide a precise opportunity for parameterizations of mixed-phase stratiform clouds associated with the SIP processes and effects of updraft and temperature.

A ground-based lidar is a powerful tool for studying the vertical structure and optical properties of clouds. A layer detection algorithm is important to determine the presence and spatial position of clouds from vast lidar signals. However, current detection algorithms for ground-based lidar still involve substantial missing and false detections for tenuous layers and layer edges. Here, a joint multiscale cloud layer detection algorithm is proposed. The algorithm can effectively capture the tenuous layers and layer edges by using joint multiscale detection methods based on a trend function and the Bernoulli distribution assumption. Results show that the proposed algorithm detects 10.45% more cloud layers than the official cloud product of Micro Pulse Lidar Network (MPLNET) does. Specifically, 7.93% and 12.57% more cloud layers are detected at daytime and nighttime, respectively. The evaluation based on depolarization properties proves that the additional cloud layers detected by the joint multiscale algorithm are reliable. These additional detected clouds have important implications for cloud climatology and climate change research. The new algorithm remarkably enhances the cloud detection capability of ground-based lidar and potentially be widely used by the community.

The characteristics of cloud droplet size distributions and statistical relations of the relative dispersion (ε) with the vertical velocity (w) and with the interstitial aerosol concentration (Nia) are investigated for ubiquitous supercooled shallow stratocumulus observed over the Southern Ocean (SO) using aircraft measurements obtained during the Southern Ocean Cloud Radiation Aerosol Transport Experimental Study. Distinct vertical variations have been found using 36 non‐precipitating cloud profiles. The cloud droplet effective radius (re) increases nearly monotonically from 5.3 ± 1.9 μm at cloud base to 9.4 ± 2.2 μm at cloud top. The ε decreases rapidly from cloud base (0.42 ± 0.13) and then remains relatively constant in the upper cloud layer (0.27 ± 0.09). This study also shows robust dependence of ε on both Nia and w. The ε increases (decreases) with increasing Nia (w) at a 95% confidence level when values of w (low Nia) are restricted to a small range. The important roles of aerosols and dynamics on ε are demonstrated and are crucial to estimating aerosol indirect radiative forcing, especially for pristine SO regions where models almost universally underestimate reflected radiation.

Although great progress has been made in the study of aerosol-cloud interactions (ACIs), representation of ACI is still the largest uncertainty in current weather and climate models. In this study, the ACI over the North China Plain and north of the Yangtze Plain is investigated using multi-source data including satellite, ground-based, reanalysis, and fusion data. The effects of aerosol characteristics (PM2.5, PM10, and PM2.5/PM10 ratio), atmospheric conditions including liquid water path (LWP) and lower tropospheric stability (LTS), and drizzle on ACI are analyzed. Results suggest that both aerosol characteristics and atmospheric conditions can affect cloud effective radius (re), but drizzle in clouds plays a decisive role on ACI. In the case of fixed LTS and LWP, the average cloud droplet re increases first and then fluctuates for all clouds examined with the increase of PM2.5 concentration. The PM2.5 concentration corresponding to the turning point of re increases with the increasing LWP due to the increased chance of collision and coalescence. In contrast, the average cloud droplet re and PM2.5 concentration show a negative correlation for clouds without drizzle, which is mainly caused by competition of water vapor. The quantitative ACI results show that the values of the aerosol first indirect effect are negative for most cases when considering all clouds examined, but positive when only considering clouds without drizzle.

Abstract Cloud plays essential roles to Earth's energy balance and hydrological cycle. Its characteristics could be modified by human activities through cloud seeding. However, there is long‐lasting debate whether the cloud seeding can modify the clouds to introduce or change precipitation effectively, due to the challenge that the effect of cloud seeding is difficult to be evaluated. Using the data from a cloud seeding experiment, this study investigates the differences of cloud properties between before and after the cloud seeding for a supercooled liquid cloud. It shows that before the cloud seeding, the clouds are supercooled liquid phase clouds. After cloud seeding, the observations from both the cloud particle images and cloud particle size distributions indicate the occurrence of large ice crystal particles and the broadening of particle size distribution. Thus, much larger and much more ice crystal particles occurred after the cloud seeding, which could further grow into precipitation particles through collision‐coalescence process. Satellite image further shows the formation of precipitation clearly after the cloud seeding experiment. This study suggests that cloud seeding can work efficiently for supercooled liquid clouds.

计算了6个不同高度和不同结构体系的超高层建筑模型的竖向自振周期和竖向地震响应;分析了超高层建筑竖向构件和水平构件的竖向地震动响应特征.研究发现,超高层建筑水平自振周期远大于场地特征周期,而竖向自振周期则与场地特征周期接近,竖向振动响应得到放大.根据设计反应谱,对于各种抗震设防烈度,结构总竖向地震作用标准值FEvk都至少是结构总水平地震作用标准值FEk的2.44倍.进而提出描述超高层建筑受到竖向地震全过程的4个概化模型,并指出规范简化算法的局限性.提出竖向地震作用对P-△效应与P-δ效应的放大主要体现在P值增大,使得“重力二阶效应”变成“重力与竖向地震响应共同作用下的二阶效应”.采用时程分析法研究了水平构件振动加速度响应,提出二次振动和竖向构件错动对水平构件振动响应有显著影响.分析了采用振型分解法计算超高层建筑竖向地震响应时质量参与系数偏低的原因,并指出当结构高度超过某一数值时,竖向地震作用下的结构第一阶振型会从竖向振动转变为水平摆动.

Artificial soil erosion caused by engineering practices is becoming increasingly severe worldwide. However, little is known about the change of soil structure of new reconstructed purple soil after erosion in the hilly areas of Southwest China. This study aims to analyze the effects of erosion on the soil particle-size distribution (PSD) and aggregate stability of new reconstructed purple soil in the overland flow under different flow discharges, slope lengths, and slope positions. A series of field scouring experiments was conducted. Flow discharges of 5, 15, and 30 L/min were applied in the new reconstructed purple soil plots with different slope lengths (5, 10, 20, 30, 40, and 50 m). Sediment samples were collected in 550-mL bottles. Soil sampling was conducted from the 0–10-cm layers before and after the field scouring experiments. In the laboratory, the pipette method was used to measure the soil PSD and microaggregates. The macroaggregates were determined by the dry and wet sieving method. Silt particles were eroded most at 30 L/min, by 2.11%. The average maximal reduction rate of the mean weight diameter of soil aggregates (MWD) was 20.23% at 15 L/min. Clay loss was maximal at 1.04%, and the average maximal increasing rate of the > 0.25 mm percentage of aggregate disruption (PAD0.25) was 0.86% at 5 L/min. The silt and MWD maximally decreased by 7.72% and 1.86%, and the maximal sand and PAD0.25 increased by 16.70% and 25.18%, which were all observed in the 10-m plot. The percentage of soil aggregates destroyed by the change in the MWD was − 14.32% on the upslope. Silt sediment showed an increasing rate of 6.36% and microaggregate destruction showed a decreasing rate of 13.00% on the middle slope. Microaggregates and clay particles were mainly deposited on the lower slope and the reduction rates of the silt and sand content were smaller than those on the middle slope. The effects of erosion on the soil PSD and aggregate stability of new reconstructed purple soil in the overland flow under different flow discharges, slope lengths, and slope positions were obviously different. Soil and water conservation measures should be effectively implemented on the upper slope and a slope length of 10-m soil. The soil PSD and MWD could be used as parameters for prediction of soil erosion on new reconstructed purple soil.

The relationship between aerosol optical depth (AOD) and PM2.5 is often investigated in order to obtain surface PM2.5 from satellite observation of AOD with a broad area coverage. However, various factors could affect the AOD-PM2.5 regressions. Using both ground and satellite observations in Beijing from 2011 to 2015, this study analyzes the influential factors including the aerosol type, relative humidity (RH), planetary boundary layer height (PBLH), wind speed and direction, and the vertical structure of aerosol distribution. The ratio of PM2.(5) to AOD, which is defined as eta, and the square of their correlation coefficient (R-2) have been examined. It shows that eta varies from 54.32 to 183.14, 87.32 to 104.79, 95.13 to 163.52, and 1.23 to 235.08 mu g m(-3) with aerosol type in spring, summer, fall, and winter, respectively. eta is smaller for scattering-dominant aerosols than for absorbing-dominant aerosols, and smaller for coarse-mode aerosols than for fine-mode aerosols. Both RH and PBLH affect the eta value significantly. The higher the RH, the smaller the eta, and the higher the PBLH, the smaller the eta. For AOD and PM2.5 data with the correction of RH and PBLH compared to those without, R-2 of monthly averaged PM2.5 and AOD at 14.00 LT increases from 0.63 to 0.76, and R-2 of multi-year averaged PM2.5 and AOD by time of day increases from 0.01 to 0.93, 0.24 to 0.84, 0.85 to 0.91, and 0.84 to 0.93 in four seasons respectively. Wind direction is a key factor for the transport and spatial-temporal distribution of aerosols originated from different sources with distinctive physicochemical characteristics. Similar to the variation in AOD and PM2.5, eta also decreases with the increasing surface wind speed, indicating that the contribution of surface PM2.5 concentrations to AOD decreases with surface wind speed. The vertical structure of aerosol exhibits a remarkable change with seasons, with most particles concentrated within about 500 m in summer and within 150 m in winter. Compared to the AOD of the whole atmosphere, AOD below 500 m has a better correlation with PM2.5, for which R-2 is 0.77. This study suggests that all the above influential factors should be considered when we investigate the AOD-PM2.5 relationships.

DOAS analysis and data screeningIn the DOAS analysis, the slant column densities (SCDs) of the trace gases (TGs) are retrieved from the off-axis spectra using a zenith measurement from the same elevation sequence as the Fraunhofer reference spectrum (FRS).As the latter also contains (usually small) absorptions features, the resulting SCD actually represents the differences between the SCDs of the measured spectrum and the FRS.This difference is usually referred to as the differential SCD (dSCD).The use of a FRS from the same elevation sequence can minimise any effects caused by changes of the properties of the instrument (relevant for long term analyses) and the stratospheric absorptions (relevant for measurements at high solar zenith angle (SZA)).The effect of rotational Raman scattering is considered by including a Ring spectrum (Shefov 1959;Grainger and Ring, 1962;Chance and Spurr, 1997;Solomon et al., 1987;Wagner et al., 2009) computed by the DOASIS software (Kraus, 2006, using a routine from Bussemer 1993).To account for the different wavelength dependencies of the filling-in in clear and cloudy skies, an additional Ring spectrum as described in Wagner et al. ( 2009) is also included.For the retrieval of O 4 and NO 2 , the wavelength range of 351 to 390 nm is selected, covering two O 4 absorption bands and several NO 2 absorption bands.A 3 rd order polynomial is used.Besides the NO 2 cross section at the temperature of 294 K, another cross section at 220 K is also included in the fit to account for the temperature dependence of the NO 2 absorptions.The detailed DOAS settings for the retrieval are listed in Table 1 of the main manuscript.In Fig. S1a andb, the O 4 and NO 2 dSCDs from all measurements are plotted against SZA.NO 2 and O 4 dSCDs show an obvious systematic increase or decrease, respectively, for SZA larger than 75°.For NO 2 this behaviour can be explained by the larger differences of the stratospheric light paths between the measurement and the FRS for large SZA.The opposite dependencies in the morning and evening

The accumulation of space debris is expected to present an increasing threat to orbital aerostat. To develop and use space resource continually and in security the detecting technology for space debris has to be improved. The paper firstly introduces the concept of space debris and their common detection means, and then introduces the application of lidar in detecting the space debris. Comparing with conventional optical observation systems lidar adopts active detecting mode, without the limitation of illumination and with a long detecting distance. It also can measure range and speed of targets. Comparing with microwave radar the beam of lidar is narrow and it has great orientation precision and resolving power. To satisfy detecting small-sized debris in long distance and big area the paper proposes the composite method to detect the space debris which uses millimeter wave radar and optic equipment. It firstly uses millimeter wave with long distance and big view field to confirm the position of debris in long distance. And then it uses optical system with high resolving and anti-jamming power for accurate orientation and identification. It also measure the distance, angle and speed exactly of debris. The study in theory indicates this composite method can complete the detecting and orientation and achieve the distance, angle and speed of the space debris more than 10cm range beyond 150km.

When laser ranger is transported or used in field operations, the transmitting axis, receiving axis and aiming axis may be not parallel. The nonparallelism of the three-light-axis will affect the range-measuring ability or make laser ranger not be operated exactly. So testing and adjusting the three-light-axis parallelity in the production and maintenance of laser ranger is important to ensure using laser ranger reliably. The paper proposes a new measurement method using digital image processing based on the comparison of some common measurement methods for the three-light-axis parallelity.It uses large aperture off-axis paraboloid reflector to get the images of laser spot and white light cross line, and then process the images on LabVIEW platform. The center of white light cross line can be achieved by the matching arithmetic in LABVIEW DLL. And the center of laser spot can be achieved by gradation transformation, binarization and area filter in turn. The software system can set CCD, detect the off-axis paraboloid reflector, measure the parallelity of transmitting axis and aiming axis and control the attenuation device. The hardware system selects SAA7111A, a programmable vedio decoding chip, to perform A/D conversion. FIFO (first-in first-out) is selected as buffer. USB bus is used to transmit data to PC.The three-light-axis parallelity can be achieved according to the position bias between them. The device based on this method has been already used. The application proves this method has high precision, speediness and automatization