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The relationship between precipitation and cloud properties in Southwest China are investigated by using the CLARA‐A2 cloud parameters data and TRMM‐3B43 precipitation data from 1998 to 2015. Ice water path (IWP) and cloud top height (CTH) are significantly and positively correlated with precipitation in all regions, indicating that ice‐phase processes and cloud development processes are the critical processes influencing precipitation. Precipitation is also directly associated with cloud fractional coverage (CFC) due to the significant positive correlation between CFC and precipitation in all regions except the Sichuan Basin (SCB). A positive correlation between liquid water path (LWP) and precipitation is found in the Eastern Tibetan Plateau (ETP) and Yunnan‐Kweichow Plateau (YKP), but not in the Western Tibetan Plateau (WTP) and SCB. Notably, the response of precipitation to LWP is not as good as that to IWP in SCB. Precipitation is significantly negatively correlated with ice effective radius (IREF) in WTP and ETP and positively correlated with liquid effective radius (LREF) in ETP, YKP and SCB. IREF and LREF are closely related to cloud microphysical processes. Specifically, small IREF could accelerate the Bergeron process and thus increase precipitation, while large LREF is closely related to the cloud droplets coalescence process. Results indicate that the difference in precipitation between the cold and warm seasons is related to convective available potential energy (CAPE) and low troposphere relative humidity (RH). High CAPE and RH favour the precipitation occurrence in Southwest China. The influence of CAPE and RH on precipitation is more significant in the ETP than that in the WTP, owing to the orographic lifting and moisture transport from the Indian Ocean. Thermodynamic and humidity conditions have a greater impact on precipitation by influencing LREF, LWP and IWP in YKP. In SCB, precipitation shows a strong dependence on CAPE, IWP and LREF, but not on RH. [ABSTRACT FROM AUTHOR]

Aimin District, Mudanjiang, Heilongjiang, 157000, People's Republic of China, Tel +86-4536602008, Email [email protected] Background: The occurrence of necrotizing enterocolitis (NEC) is a common and severe disease of the digestive system in neonates. This study aims to assess the value of the intestinal tissue oxygen saturation (rintSO2) combined with the levels of procalcitonin (PCT) and mean platelet volume (MPV) in predicting the severity of NEC in preterm infants. Methods: This experiment was a retrospective cohort study conducted in the Department of Pediatrics, Hongqi Hospital Affiliated to Mudanjiang Medical University between January 2017 and July 2022. Premature neonates with NEC were enrolled and divided into mild-moderate NEC group and severe NEC group according to Bell's stage. The general information data, rintSO2 and blood parameters such as the white blood cell (WBC) count, platelet count (PLT), PCT, MPV, red blood cell distribution width (RDW), hemoglobin (Hb), C-reactive protein (CRP) were compared between the two groups. Results: A total of 122 patients were enrolled, including 79 mild-moderate NEC and 43 severe NEC. The rintSO2 was lower in severe group than in mild-moderate group (P = 0.042), the PCT and MPV were both higher in severe group than in mild-moderate group (P = 0.048, P = 0.049). The results of logistic regression suggested that the rintSO2 (OR = 1.491, P = 0.003), PCT (OR = 3.071, P = 0.001) and MPV (OR = 4.027, P = 0.015) were independent predictive factors for severity of NEC. The area under the curve (AUC) of the rintSO2 combined with PCT and MPV showed good diagnostic ability in the severity of NEC. Conclusion: The rintSO2 combined with PCT and MPV may be considered as the early biomarkers in the severity of NEC and could help us to diagnose the case early with early treatment with better prognosis. [ABSTRACT FROM AUTHOR]

This study analyzed the macro- and microphysical response characteristics of a typical multicell hailstorm after seeding on 27 April 2019 in Weining, China, using X-band dual-polarization radar (YLD1-D) data. An improved X-pol hydrometeor identification algorithm was employed for hydrometeor identification. According to the diffusion of the seeding agents, the seeded hailstorm was graded into three study regions, and the evolution of the seeded hailstorm was divided into four periods. The response characteristics of the seeded hailstorm in each region and period were compared and analyzed. The results show that 1) macroscopically, the decrease in the reflectivity and the height of strong echo mainly occurred in the seeded period, whereas the decrease in the echo top and the height of the storm was mainly in the postseeded period; the echo height variation of the unseeded hailstorm is obviously different from that of the seeded hailstorm; and 2) from the microscopic perspective, the decrease in low-density graupel and supercooled water and the increase in ice crystals and aggregates in the seeded region mainly occurred in the seeded period, which was consistent with the time required for the "benefit competition" after the silver iodide completed nucleation. When compared with the seeded region, the hydrometeors in the unseeded region had an opposite trend (or an in-phase trend with an obviously lower changing rate), which further indicated the impact of the artificial ice nuclei on microphysical processes in the seeded region. For hailstorms with a high content of supercooled droplets and graupel, the key mechanisms of hail suppression are "cloud water glaciation," "beneficial competition," and "early rainout." [ABSTRACT FROM AUTHOR]

The effect of aerosol on liquid cloud microphysical properties over the Tibetan Plateau (TP) during the warm season is investigated by using aerosol index (AI) and cloud property parameters data. Distinct differences in aerosol effect on liquid cloud microphysical properties have been found between the northern Tibetan Plateau (NTP) and southernTibetan Plateau (STP). The composite liquid cloud droplet effective radius liquid cloud droplet effective radius (LREF) anomalies for positive AI events are positive in the NTP and negative in the STP. In both NTP and STP, when the AI anomalies are positive, the LREF anomalies are also positive, which suggests that the increased aerosol loading reduces the solar radiation reaching the ground and thus enhances the atmospheric stability, which reduces the cloud base height and makes the liquid cloud area thicker, which gives cloud droplets more space to grow by collision‐coalescence. This indicates that the aerosol radiative effect is not likely the reason causing the distinct differences of aerosol effects on liquid cloud properties between NTP and STP. Further analysis shows that in the STP, the LREF first increases and then decreases with the increase of AI, while in the NTP, the LREF always increases with the increase of AI, suggesting a spatial difference in aerosol microphysical effect. In the STP, the influence of aerosol on liquid clouds is mainly dependent on liquid water path and convective available potential energy, while in the NTP, the influence of aerosol on liquid cloud is more likely related to large aerosol particles. Plain Language Summary: This study shows that the influence of aerosols on liquid clouds over the Tibetan Plateau (TP) in the warm season is different between the southern Tibetan Plateau (STP) and northern Tibetan Plateau (NTP). Aerosol influences the microphysics of liquid cloud over the TP through its radiative and microphysical effects. Aerosols show the uniform radiative effect over the STP and NTP, more aerosols reduce the solar radiation reaching the ground, resulting in a lower cloud base and then more space for cloud droplets to grow. Over the STP, the liquid cloud droplet effective radius (LREF) increases first and then decreases with the increase of aerosol; over the NTP, the LREF increases with the increase of aerosols, which reflects the different microphysical effects of aerosols under different meteorological conditions and aerosol types. Key Points: The effect of aerosol on liquid cloud is spatially disparate between the southernTibetan Plateau (STP) and northern Tibetan Plateau (NTP)Positive relationship between the aerosol index (AI) and the liquid cloud droplet effective radius liquid cloud droplet effective radius (LREF) is shown in both STP and NTPLREF first increases and then decreases in the STP while always increases in the NTP with the increasing of AI [ABSTRACT FROM AUTHOR]

This paper discusses the temporal and spatial distribution characteristics of cloud-to-ground (CG) lightning activity over the Qinghai-Tibetan Plateau (QTP) from 2009 to 2018 and their dependence on meteorological factors. It is found that (1) the number of CG flashes fluctuates, reaches a maximum in 2014, and then gradually decreases. The main active period of CG lightning is from June to September each year, after which it decreases rapidly. CG lightning is mainly distributed in the valley areas at around 4800 m above sea level at Lhasa, Nagqu, and Chamdo, and there are differences in the characteristics of CG activity in these three areas. The peak of daily CG lightning occurs at 1000 UTC, and the lowest value is at 0400 UTC. The distribution of CG lightning in all seasons has obvious differences in peak time and the proportion of positive CG (+CG) lightning, with the ratio of +CG lightning to total CG lightning flashes in spring and autumn exceeding 50%. (2) The ratio of +CG lightning to total CG lightning flashes over the QTP is influenced by a combination of thermodynamic and microphysical factors. Over the QTP, greater vertical wind shear leads to the movement of upper positive charges and promotes the occurrence of +CG lightning. Also, the higher total column liquid water content implies higher cloud water content in the warm-cloud region, and the higher cloud-base height implies a thicker warm-cloud region, which is not conducive to the occurrence of +CG lightning. (3) During high-value years (in this study, 2010, 2012, 2014, and 2016), the midlatitude (30°N–60°N) high pressure is strong and the plateau is situated at the intersection of the East Asian and South Asian monsoons and the cold air from the northwest, which strengthens the water vapor convergence and increases the frequency of thunderstorms. When the plateau is under the control of the southerly monsoon from June to September every year, its atmosphere is full of water vapor and lightning activity is accordingly high, with the proportion of +CG lightning being about 10%. Meanwhile, in the remaining months, when controlled by the westerly wind belt, the plateau's water vapor condition is poor, the level of lightning activity weakens, and the proportion of +CG lightning gradually increases to more than 50%. [ABSTRACT FROM AUTHOR]

Lightning matters to human life and natural fires so much that monitoring and predicting lightning are highly important. A simple proxy for climatic cloud‐to‐ground (CG) density is evaluated defined as the product of convective available potential energy (CAPE) and precipitation rate using data from 2005 to 2017 in Sichuan of Southwest China. CAPE times precipitation rate (CP) relates the monthly distribution and magnitude of negative lightning in the basin region more closely, while CP describes the monthly distribution and magnitude of positive lightning in the plateau region more appropriately. Except for individual years, the annual variation trend and magnitude of CP and positive and negative lightning are relatively consistent in the basin region, while the description of the annual variation trend and magnitude of lightning by CP in the plateau region is insufficient, especially for negative lightning. CP represents the high‐value areas of the positive and negative lightning in the basin and southern Sichuan reasonably, but misses the lightning belt in the plateau region. In general, the performance of CP for lightning in the basin is superior to that in the plateau, this may be caused by two factors, one is the particularity and complexity of lightning in the plateau resulted from special topographic and meteorological conditions, the other one is the limitation of CP caused by the fact that CP does not take into account other environmental factors contributing to lightning. The ability of this simple proxy to describe CG lightning in Sichuan is limited by vertical wind shear in the middle and lower troposphere, zero degree height, and liquid water path, mainly because the proxy does not have the ability to generalize these factors that play a key role in lightning activity. [ABSTRACT FROM AUTHOR]

The basic characteristics of cloud water, precipitation, and the dependence of precipitation efficiency (PE) on the influencing factors over the Tibetan Plateau (TP) are investigated. Results found that the liquid water path shows a significant downward trend in winter over the TP, and the ice water path shows a significant upward trend in the pre‐monsoon and winter seasons and a significant downward trend in the monsoon season in the western TP from 1998 to 2015. In the eastern TP, the precipitation in the monsoon season also shows a significant downward trend, which may be related to the weakening of the South Asian monsoon. Results have determined that precipitation depends more on the ice water cloud than on the liquid water cloud over the TP. Moreover, the convective available potential energy (CAPE) and the low‐tropospheric relative humidity (RH) are two environmental factors that have a prominent influence on the PE. During the monsoon season, higher CAPE and RH were conducive to a larger PE over the TP. The results suggest that the CAPE has a positive effect on the PE, which means that the PE is directly dependent on the convective precipitation, mainly due to the frequent convective activity and dominant convective precipitation over the TP. [ABSTRACT FROM AUTHOR]

The effects of thermodynamic and moisture factors on cloud-to-ground (CG) lightning polarity in the warm season were discussed. Small convective available potential energy (CAPE) represents relatively shallow convection, which is beneficial to the generation of positive lightning. Large vertical wind shear results in the displacement of upper-level positive ice crystals and promotes the initiation of +CG lightning from positive ice crystals. The dry low- to midlevel troposphere and the high cloud base in the plateau region favor +CG lightning, while the strong thermodynamic conditions in the basin region offset the influence of these moisture factors. In the plateau region, due to the limited cloud thickness, high total column liquid water may mean high cloud water content in the warm cloud region rather than high liquid water content in the mixed-phase region, which is unfavorable for the middle-level positive graupel and thus is unfavorable for the initiation of +CG lightning. In the basin region, the cloud thickness is relatively thicker, the high total column liquid water means that the liquid water content in the warm cloud and the mixed-phase region is both high, which is conducive to the middle-level positive graupel and the +CG lightning. [ABSTRACT FROM AUTHOR]

The joint effects of aerosol, thermodynamic, and cloud-related factors on cloud-to-ground lightning in Sichuan were investigated by a comprehensive analysis of ground-based measurements made from 2005 to 2017 in combination with reanalysis data. Data include aerosol optical depth, cloud-to-ground (CG) lightning density, convective available potential energy (CAPE), mid-level relative humidity, lower- to mid-tropospheric vertical wind shear, cloud-base height, total column liquid water (TCLW), and total column ice water (TCIW). Results show that CG lightning density and aerosols are positively correlated in the plateau region and negatively correlated in the basin region. Sulfate aerosols are found to be more strongly associated with lightning than total aerosols, so this study focuses on the role of sulfate aerosols in lightning activity. In the plateau region, the lower aerosol concentration stimulates lightning activity through microphysical effects. Increasing the aerosol loading decreases the cloud droplet size, reducing the cloud droplet collision–coalescence efficiency and inhibiting the warm-rain process. More small cloud droplets are transported above the freezing level to participate in the freezing process, forming more ice particles and releasing more latent heat during the freezing process. Thus, an increase in the aerosol loading increases CAPE, TCLW, and TCIW, stimulating CG lightning in the plateau region. In the basin region, by contrast, the higher concentration of aerosols inhibits lightning activity through the radiative effect. An increase in the aerosol loading reduces the amount of solar radiation reaching the ground, thereby lowering the CAPE. The intensity of convection decreases, resulting in less supercooled water being transported to the freezing level and fewer ice particles forming, thereby increasing the total liquid water content. Thus, an increase in the aerosol loading suppresses the intensity of convective activity and CG lightning in the basin region. [ABSTRACT FROM AUTHOR]

Utilizing routine hourly meteorological data of Xinjin Airport and daily average PM2.5 concentration data for Chengdu, winter visibility characteristics at Xinjin Airport between 2013 and 2017 and their relationship with meteorological conditions and particulate matter were analyzed. Between 2013 and 2017, the average winter visibility in Xinjin Airport was lowest in January, followed by that in December. The occurrence frequency of haze days in winter was much higher than that of nonhaze (clean) days, being 90.2% and 9.8%, respectively. These were mainly mild haze days, with an occurrence frequency of 44.4%, while severe haze days occurred the least, with a frequency of 7.7%. The linear and nonlinear relationships between winter visibility, meteorological factors, and PM2.5 were measured using daily data in winter from 2013 to 2016. The linear correlation between PM2.5 concentration and visibility was the most evident, followed by that of relative humidity. Visibility had a higher nonlinear correlation with PM2.5 concentration, relative humidity, and dew point depression. When relative humidity was between 70% and 80%, the negative correlation between visibility and PM2.5 concentration was the most significant and could be described by a power function. The multivariate linear regression equation of PM2.5 concentration and relative humidity could account for 65.9% of the variation in winter visibility, and the multivariate nonlinear regression equation of PM2.5 concentration, relative humidity, and wind speed could account for 68.1% of the variation in winter visibility. These two equations reasonably represented the variation in winter visibility in 2017. [ABSTRACT FROM AUTHOR]

Abstract: Concentrations of both nitrogen oxides (NO x =NO+NO2) observed at a station at high altitude (Puy de Dome (PDD), 1465 m) have been analyzed in relation with the cloud-to-ground (CG) lightning activity provided by the detection network Météorage. A first analysis of the time series of both types of data issued for 4 months of the 2003 summer shows a good correspondence between high values of NO x and stormy conditions in the area. During this 4-month period, NO x values exceeding 100 μg m−3 have been observed on 7 days and all of these days correspond to lightning activity in a 200×200 km2 area around PDD. Thirty-three days of the period experience lightning activity in this area, and only 14 of these days (42%) correspond to NO x peak values exceeding 50 μg m−3. The presence of lightning activity is a necessary condition to have very large peak values of NO x at PDD, but this condition is not sufficient. Two days showed NO x exceeding 300 μg m−3 which represents a value between 176 and 270 ppbv according to the respective proportion of NO2 and NO. Six days are analyzed in detail, using other information about the convective system and the wind conditions. The data of urban stations close to PDD have also been considered in the analysis for evaluating the possible transport by a plume from a city area. These days include the higher NO x cases, cases with high lightning activity, and cases with remote lightning activity. On each of these days, the location of the CG flashes, the time delays between lightning activity and NO x increase, and the air flow seem consistent with an interpretation of NO x produced by lightning. The higher values of NO x correspond with close and stationary thunderstorms which produced large proportions of positive CG flashes with low wind conditions. However, the characteristic increase seems to depend on several parameters of the CG flashes: their rate, location, and polarity. By comparing with the values given by other authors for aircraft measurements at altitude, our observations indicate that large quantities of NO x could be produced by the CG flash processes. [Copyright &y& Elsevier]

Currently, high-resolution severe storm observations obtained by vehicle-mounted mobile X-band dual-polarization radar (X-pol) are widely used in severe storm structure and dynamics studies; however, the identification of hailstones based on X-pol is still rare, leading to the limited application of X-pol in identifying hydrometeors in the microphysical processes of severe storms. Based on previous works, this study constructs an improved X-pol hydrometeor identification (HID) method for hailstorms; the hydrometeor categories include a rain-hail mixtures (RH) category indicating hailstones are melting or experiencing wet growth, and the correlation coefficient between horizontally and vertically polarized echoes (ρ HV) is used to locate the local mixed phase region in storms to avoid misclassifications of hydrometeors resulted by environmental temperature in this local mixed phase region. The improved HID method can see liquid water information above the melting layer; it provides a possibility to observe the microphysical process of hailstones wet growth above the melting layer. Furthermore, this improved HID method was utilized to study the high spatiotemporal resolution data collected by the Institute of Atmospheric Physics of Chinese Academy of Sciences (IAP) X-pol for one summer hailstorm over northern China. The results indicate that the identified RH is consistent with the surface hail record of National weather observatory of China Meteorological Administration (CMA), the specific differential phase (K DP) column is more sensitive than the differential reflectivity (Z DR) column for indicating the updraft zone movement, and we considered that the relative position between the key area of hail (KAH, where above the Z DR column, Z DR ~ −2 to 0 dB, Z H ~ ≥ 50 dB Z) and the updraft zone (indicated by the Z DR , K DP column) will determine the evolution of hail. Furthermore, high-density graupels (HDGs) in the upper layer of the KAH may be the source of RH embryos, and these HDGs collect liquid droplets from the liquid water-rich (LWR) area located behind the KAH to form a large number of RH in the lower layer of the KAH. These characteristics are important for hailstone forecasting and warnings. • Constructing an improved X-band dual-polarization radar (X-pol) hydrometeor identification (HID) method for hailstorms. • This improved method showed its superiority in observing liquid water information above the melting layer within storms. • The results reveal how the polarization parameters of X-pol indicate the generation and extinction of hail. [ABSTRACT FROM AUTHOR]

Sulfur dioxide (SO 2 ), nitrogen dioxide (NO 2 ), and ozone (O 3 ) are important atmospheric pollutants that affect air quality. The long-term variations of SO 2 and NO 2 in 2008-2018 and O 3 in 2015-2018 in the relatively less populated ecological and economic zones of Western Sichuan Plateau, Southwest China were analyzed. In 2008-2018, the variations in SO 2 and NO 2 in the ecological zone were not significant, but Ganzi showed a slight upward trend. SO 2 decreased significantly in the economic zone, especially in Panzhihua, where NO 2 changes were not obvious. From 2015 to 2018, the concentration of O 3 in the ecological zone increased significantly, while the economic zone showed a downward trend. The rising trend of the concentration ratio of SO 2 to NO 2 in the ecological zone and the declining trend in the economic zone indicate that the energy consumption structure of these two zones is quite different. The lower correlation coefficients between NO 2 and O 3 in the Western Sichuan Plateau imply that the variations of O 3 are mainly affected by the regional background. The effects of meteorological factors on SO 2 , NO 2 , and O 3 were more obvious in the economic zone where there are high anthropometric emissions.