Strong Solar Radiation Research Articles

Enhanced heating rate of black carbon above the planetary boundary layer over megacities in summertime

The fast development of a secondary aerosol layer was observed over megacities in eastern Asia during summertime. Within three hours, from midday to early afternoon, the contribution of secondary aerosols above the planetary boundary layer (PBL) increased by a factor of three to five, and the coatings on black carbon (BC) also increased and enhanced its absorption efficiency by 50%. This tended to result from the intensive actinic flux received above the PBL which promoted photochemical reactions. The absorption of BC could be further amplified by the strong reflection of solar radiation over the cloud top across the PBL. This enhanced heating effect of BC introduced by combined processes (intensive solar radiation, secondary formation and cloud reflection) may considerably increase the temperature inversion above the PBL. This mechanism should be considered when evaluating the radiative impact of BC, especially for polluted regions receiving strong solar radiation.

First Long-Term Study of Atmospheric New Particle Formation in the Suburb of Shanghai from 2015 to 2017

In this study, long-term continuous monitoring of atmospheric new particle formation was conducted from 2015 to 2017 in the Shanghai suburbs using a scanning mobility particle sizer (SMPS). Combined with meteorological parameters, gaseous pollutants, and PM2.5 chemical composition data, the characterization of new particle formation was analyzed. The results of data analysis showed there were 172 new particle formation (NPF) days in the Shanghai suburbs, accounting for 18.3% of the total effective days (942 d). Typical new particle formation days (Event) and new particle growth-shrinkage (Shrinkage) days were 150 d and 32 d, respectively. The frequency of NPF occurrence was the highest in spring and summer, followed by autumn and winter. Compared with non-new particle formation (Non-NPF) days, Event and Shrinkage days had higher temperature and wind speed, lower humidity, less rainfall, and stronger solar radiation. The ratio of Event days was the highest when the prevailing wind was southerly, southwesterly, or westerly, and when the air masses were mainly from the vegetation cover and agricultural planting areas in the Taihu Lake Basin. The prevailing wind directions for Non-NPF and Shrinkage days were northeasterly and easterly to southeasterly. On the Event days, SO2 and O3 were higher than that on the Non-NPF days, indicating gaseous sulfuric acid and photochemical reactions were key contributors to new particle formation. Higher PM10 concentration was detected on the Event days than on the Non-NPF days, which may be attributed to the photocatalytic reaction. All the pollutant concentrations were the lowest on Shrinkage days, except that of O3. The average concentrations of inorganic components of PM2.5, such as NH4+, SO42-, and NO3- were higher on Event than on Non-NPF days in fall, whereas the opposite results were observed in other seasons. The average concentration of organic carbon on Event days was higher than that on Non-NPF days in each season. The concentrations of PM2.5 components on Shrinkage days were the lowest. However, the ratio of organic carbon on Shrinkage days was higher than that on Non-NPF days in spring, summer, and winter. The higher ratio of organic carbon on the NPF days than on the Non-NPF days suggested an important role of organic matter in the formation and growth of new particles in the suburbs of Shanghai.

Demonstration of daytime wind measurement by using mobile Rayleigh Doppler Lidar incorporating cascaded Fabry-Perot etalons.

A well-designed filter assembly is incorporated to an earlier mobile Rayleigh Doppler Lidar developed at University of Science and Technology of China (USTC) for wind measurement round the clock. The filter assembly consists of two cascaded Fabry-Perot Etalons (FPEs) and a narrow-band interference filter (IF), which are optimized to filter out strong solar background radiation during daytime. The high resolution FPE is mainly used to compress the whole bandwidth of the filter assembly, whereas the low resolution FPE with relatively large free spectral range (FSR) is primarily used to block the unwanted periodic transmission peaks of high resolution FPE arising within the narrow-band IF passband. Some test experiments are carried out and demonstrate that the filter assembly have an overall peak transmission of 33.32% with a bandwidth of 2.41 pm at 355 nm. When applying it to the USTC mobile Rayleigh Doppler Lidar, the daytime background is only 3% or less than before. Consequently, the detectable altitude during daytime increases to ∼51 km with wind velocity accuracy of ±7.6 m/s.

Ammonia Oxidizers in High-Elevation Rivers of the Qinghai-Tibet Plateau Display Distinctive Distribution Patterns.

Ammonia-oxidizing bacteria (AOB) and archaea (AOA) as well as comammox catalyze ammonia oxidation. The distribution and biogeography of these ammonia oxidizers might be distinctive in high-elevation rivers, which are generally characterized by low temperature and low ammonium concentration but strong solar radiation; however, these characteristics have rarely been documented. This study explored the abundance, community, and activity of ammonia oxidizers in the overlying water of five rivers in the Qinghai-Tibet Plateau (QTP). Potential nitrification rates in these rivers ranged from 5.4 to 38.4 nmol N liter-1 h-1, and they were significantly correlated with ammonium concentration rather than temperature. Comammox were found in 25 of the total 28 samples, and they outnumbered AOA in three samples. Contrary to most studied low-elevation rivers, average AOB amoA gene abundance was significantly higher than that of AOA, and AOB/AOA ratios increased with decreasing water temperature. The Simpson index of the AOA community increased with elevation (P < 0.05), and AOA and AOB communities exhibited high dissimilarities with low-elevation rivers. Cold-adapted (Nitrosospira amoA cluster 1, 33.6%) and oligotrophic (Nitrosomonas amoA cluster 6a, 31.7%) groups accounted for large proportions in the AOB community. Suspended sediment concentration exerted significant effects on ammonia oxidizer abundance (r > 0.56), and owing to their elevational variations in source and concentration, suspended sediments facilitated distance-decay patterns for AOA and AOB community similarities. This study demonstrates distinctive biogeography and distribution patterns for ammonia oxidizers in high-elevation rivers of the QTP. Extensive research should be conducted to explore the role of these microbes in the nitrogen cycle of this zone.IMPORTANCE Ammonia-oxidizing archaea (AOA) and bacteria (AOB) as well as comammox contribute to ammonia oxidation, which plays significant roles in riverine nitrogen cycle and N2O production. Source regions of numerous rivers in the world lie in high-elevation zones, but the abundance, community, and activity of ammonia oxidizers in rivers in high-elevation regions have rarely been investigated. This study revealed distinctive distribution patterns and community structures for ammonia oxidizers in five high-elevation rivers of the Qinghai-Tibet Plateau, and the individual and combined effects of low temperature, low nutrients, and strong solar radiation on ammonia oxidizers were elucidated. The findings of this study are helpful to broaden our knowledge on the biogeography and distribution pattern of ammonia oxidizers in river systems. Moreover, this study provides some implications to predict the performance of ammonia oxidizers in high-elevation rivers and its variations under global climate warming.

Numerical investigation on building envelope optimization for low-energy buildings in low latitudes of China

Different from the high latitudes (24°N-53°N) of China, the low latitudes (4°N-24°N) present large solar elevation angle and strong solar radiation throughout the year. Radiation differences in all directions are smaller than that in high latitudes, which results in the building envelope optimization (BEO) in high latitudes is not applicable to low latitudes. Therefore, for the low latitudes, this research calculated the energy-saving effect of buildings with different shape parameters and the cooling load of thermal performance of different envelope by numerical simulation. In addition, the corresponding energy-saving indexes for cooling load reduction (CLR) are presented. And the energy saving priority of building envelope is mastered by analyzing the percentage of CLR per unit volume, the roofs have the greatest energy saving potential, followed by exterior walls, sunshade and exterior windows. Furthermore, the recommended insulation thickness for the exterior walls and roofs should be 30–40 mm, and of which the CLR value of per unit external wall area can reach 8.5 W/m2. The west exterior window has greater energy saving potential than other orientations. The effect of east and west sunshade on CLR is much greater than that of south sunshade. The recommended length of the north and south shading should be 500–600 mm, in which the cooling load from shading can be reduced by 95% and 15% respectively. The results can be the basis of the design method of the BEO in low latitudes of China.

Sowing Dates have Different Effects on Spikelet Formation among Different Photoperiod‐Sensitive Rice Genotypes

The photoperiod sensitivity of rice (Oryza sativa L.) cultivars plays an important role in rice growth and yield formation. To ascertain the different effects of sowing dates on spikelet formation for different photoperiod‐sensitive genotypes, 10 sowing dates were selected to assess differences in spikelet differentiation and degeneration for photoperiod‐sensitive cultivars yongyou 538 (YY538) and xiushui134 (XS134) and photoperiod‐insensitive cultivar chujing27 (CJ27). The yield of the cultivars differed significantly among different sowing dates and was primarily influenced by the spikelet number per panicle. With different sowing dates, shorter daylengths, and increasing temperatures significantly shortened the duration from sowing to heading for YY538 and XS134, while that of CJ27 was less changed and influenced by the average temperature. Rice growth duration was the primary factor limiting dry matter accumulation (DMA), which was correlated with the number of differentiated spikelets (NDS) and the proportion of degenerated spikelets (PGS) in photoperiod‐sensitive varieties. High temperature weather with a relatively large temperature gap and strong solar radiation promoted spikelet differentiation in all three cultivars. Extremely high and low temperatures aggravated spikelet degeneration, but YY538 and XS134 were not exposed to low temperatures because their duration of growth was shortened to a greater extent than that of CJ27 with late sowing dates. Under different sowing dates, the NDS and PGS were evaluated by partial least squares regression (PLSR) with DMA, rice growth duration, temperature, and solar radiation. These results provide a reference for sowing date adjustment with climate changes in different regions.Core Ideas Rice yield with different sowing dates was determined by spikelet number. Rice growth duration was the primary factor affecting dry matter accumulation. High temperature and more dry weight increased spikelet differentiation. Sowing photoperiod‐sensitive cultivars at a late date avoided chilling injury. Spikelet formation can be predicted by partial least squares regression with sowing dates.

Influence of planning decisions on the local climate of residential building of the Krasnodar region and the Primorsk region

Introduction: the article presents the examples of architectural and planning solutions on optimization of courtyard spaces in the southern regions of the Russian Federation, their protection from strong wind, insufficient airing, overheating and solar radiation, as well as anthropogenic and natural ones. In modern Russian construction, insufficient attention is paid to natural and climatic effects. Typical residential housing is used in all regions of the country. The main reason is the lack of regulatory documents for each region, which has its characteristics (presence of water bodies, terrain features, a wind rose, etc.). This problem dictates the need to structure the vital natural and climatic factors which affect the yard territory microclimate. Based on this, compensatory effective improvement methods and solutions that can balance the adverse effect of natural and climatic conditions and create the parameters and norms of architectural and urban planning design are presented.&#x0D; &#x0D; &#x0D; Materials and methods: the article analyzed the following information: standards, guidelines, design and regulatory documents in the field of construction and design, published data, and materials of domestic and foreign scientific research on this subject. Methods of scientific research are based on the use of factor and comparative analyses and the theory of constraints.&#x0D; &#x0D; &#x0D; Results: the article as formed the architectural and planning proposals on the residential area climate-based development.&#x0D; &#x0D; &#x0D; Conclusions: a planning structure based on local natural and climatic consideration (terrain features, the wind rose, etc.) and application of effective methods of territory protection from excessive solar radiation and adverse winds can form a favorable microclimate of a residential building for human comfort habitation. Correct assessment of the climatic features allows making bioclimatic protection economically sound and efficient in terms of energy consumption as well as defining favorable architectural and planning solutions.

Revealing Urban Morphology and Outdoor Comfort through Genetic Algorithm-Driven Urban Block Design in Dry and Hot Regions of China

In areas with a dry and hot climate, factors such as strong solar radiation, high temperature, low humidity, dazzling light, and dust storms can tremendously reduce people’s thermal comfort. Therefore, researchers are paying more attention to outdoor thermal comfort in urban environments as part of urban design. This study proposed an automatic workflow to optimize urban spatial forms with the aim of improvement of outdoor thermal comfort conditions, characterized by the universal thermal climate index (UTCI). A city with a dry and hot climate—Kashgar, China—is further selected as an actual case study of an urban block and Rhino &amp; Grasshopper is the platform used to conduct simulation and optimization process with the genetic algorithm. Results showed that in summer, the proposed method can reduce the averaged UTCI from 31.17 to 27.43 °C, a decrease of about 3.74 °C, and reduce mean radiation temperature (MRT) from 43.94 to 41.29 °C, a decrease of about 2.65 °C.

Near-Earth asteroids spectroscopic survey atIsaac NewtonTelescope

Context.The population of near-Earth asteroids (NEAs) shows a large variety of objects in terms of physical and dynamical properties. They are subject to planetary encounters and to strong solar wind and radiation effects. Their study is also motivated by practical reasons regarding space exploration and long-term probability of impact with the Earth.Aims.We aim to spectrally characterize a significant sample of NEAs with sizes in the range of ~0.25–5.5 km (categorized as large), and search for connections between their spectral types and the orbital parameters.Methods.Optical spectra of NEAs were obtained using theIsaac NewtonTelescope (INT) equipped with the IDS spectrograph. These observations are analyzed using taxonomic classification and by comparison with laboratory spectra of meteorites.Results.A total number of 76 NEAs were observed. We spectrally classified 44 of them as Q/S-complex, 16 as B/C-complex, eight as V-types, and another eight belong to the remaining taxonomic classes. Our sample contains 27 asteroids categorized as potentially hazardous and 31 possible targets for space missions including (459872) 2014 EK24, (436724) 2011 UW158, and (67367) 2000 LY27. The spectral data corresponding to (276049) 2002 CE26 and (385186) 1994 AW1 shows the 0.7μm feature which indicates the presence of hydrated minerals on their surface. We report that Q-types have the lowest perihelia (a median value and absolute deviation of 0.797 ± 0.244 AU) and are systematically larger than the S-type asteroids observed in our sample. We explain these observational evidences by thermal fatigue fragmentation as the main process for the rejuvenation of NEA surfaces.Conclusions.In general terms, the taxonomic distribution of our sample is similar to the previous studies and matches the broad groups of the inner main belt asteroids. Nevertheless, we found a wide diversity of spectra compared to the standard taxonomic types.

RadioAstron orbit determination and evaluation of its results using correlation of space-VLBI observations

A crucial part of a space mission for very-long baseline interferometery (VLBI), which is the technique capable of providing the highest resolution images in astronomy, is orbit determination of the mission’s space radio telescope(s). In order to successfully detect interference fringes that result from correlation of the signals recorded by a ground-based and a space-borne radio telescope, the propagation delays experienced in the near-Earth space by radio waves emitted by the source and the relativity effects on each telescope’s clock need to be evaluated, which requires accurate knowledge of position and velocity of the space radio telescope. In this paper we describe our approach to orbit determination (OD) of the RadioAstron spacecraft of the RadioAstron space-VLBI mission. Determining RadioAstron’s orbit is complicated due to several factors: strong solar radiation pressure, a highly eccentric orbit, and frequent orbit perturbations caused by the attitude control system. We show that in order to maintain the OD accuracy required for processing space-VLBI observations at cm-wavelengths it is required to take into account the additional data on thruster firings, reaction wheel rotation rates, and attitude of the spacecraft. We also investigate into using the unique orbit data available only for a space-VLBI spacecraft, i.e. the residual delays and delay rates that result from VLBI data processing, as a means to evaluate the achieved OD accuracy. We present the results of the first experience of OD accuracy evaluation of this kind, using more than 5000 residual values obtained as a result of space-VLBI observations performed over 7 years of the RadioAstron mission operations.

Modeling experiments on seasonal lake ice mass and energy balance in the Qinghai–Tibet Plateau: a case study

Abstract. The lake-rich Qinghai–Tibet Plateau (QTP) has significant impacts on regional and global water cycles and monsoon systems through heat and water vapor exchange. The lake–atmosphere interactions have been quantified over open-water periods, yet little is known about the lake ice thermodynamics and heat and mass balance during the ice-covered season due to a lack of field data. In this study, a high-resolution thermodynamic ice model was applied in experiments of lake ice evolution and energy balance of a shallow lake in the QTP. Basal growth and melt dominated the seasonal evolution of lake ice, but surface sublimation was also crucial for ice loss, accounting for up to 40 % of the maximum ice thickness. Sublimation was also responsible for 41 % of the lake water loss during the ice-covered period. Simulation results matched the observations well with respect to ice mass balance components, ice thickness, and ice temperature. Strong solar radiation, negative air temperature, low air moisture, and prevailing strong winds were the major driving forces controlling the seasonal ice mass balance. The energy balance was estimated at the ice surface and bottom, and within the ice interior and under-ice water. Particularly, almost all heat fluxes showed significant diurnal variations including incoming, absorbed, and penetrated solar radiation, long-wave radiation, turbulent air–ice heat fluxes, and basal ice–water heat fluxes. The calculated ice surface temperature indicated that the atmospheric boundary layer stratification was consistently stable or neutral throughout the ice-covered period. The turbulent air–ice heat fluxes and the net heat gain by the lake were much lower than those during the open-water period.

The energy mechanism controlling the continuous development of a super-thick atmospheric convective boundary layer during continuous summer sunny periods in an arid area

In the arid regions of the world, due to the specific climatic and environmental background, a super-thick convective boundary layer (SCBL) often develops on sunny days in summer, whereas such phenomena rarely occur in other areas. This special boundary layer structure has an important synoptic and climatic significance, but there have been few studies of its development mechanism in arid areas, which greatly restricts the parametric improvement of the SCBL and our understanding of the interaction between weather and climate processes. This study was conducted in Dunhuang, which is located in the hinterland of northwest China. Based on data obtained from land-air interaction experiments and long-term operational sounding observations in this region, the energy mechanism controlling the development of the CBL and the developmental process of the SCBL were systematically analyzed. In arid northwest China, it is possible that the thickness of the CBL can extend to over 3 km for most of the year, except winter. Even in the early summer, when there is little rain and strong solar radiation, the thickness of the CBL may reach an extreme state of 5.4 km. The thickness of the CBL at this time is higher than that observed in midsummer, when there is slightly more precipitation in this area. This is basically consistent with the extreme thickness of the CBL recently discovered in the Sahara Desert in Africa. In the general mechanism that controls the development of the CBL, there is a close relationship between the development of the CBL and the sensible heat flux of the surface. However, the correlation between the thickness of the CBL and the surface sensible heat flux at the same time is not strong, whereas the correlation between the thickness of the CBL and the cumulative surface sensible heat flux is very strong. This indicates that the development of the CBL is the result of the continuous accumulation of the sensible heat flux on the surface, which is consistent with the energy mechanism controlling the CBL. Although the development of the CBL is closely related to the cumulative heating effect of the daytime surface sensible heat flux, the CBL would still continue to increase even if the integral value of the daytime surface sensible heat flux remained unchanged or even weakened during the continuous clear sky period. The energy provided through sensible heat does not fully explain the energy required to develop the CBL. This is mainly because the deep near-neutral residual layer (RL) background plays an important role in the development of the SCBL. The entrainment energy from the deep RL to the CBL is the key energy supply for the continuous development of the CBL. The sum of the entrainment energy and surface sensible heat energy coincides with the energy absorbed by the development of the SCBL. The reason for the occurrence of an SCBL in arid areas is not only the strong sensible heating in summer but also the persistent clear skies in such areas. In each continuous clear sky period, the positive feedback mechanism between the CBL and the RL will become operational. Under this mechanism, the daily maximum thickness of the CBL and the thickness of the RL will increase continuously. The thickness of the SCBL is generally over 3 km, although depths of over 5 km can develop through a cyclic growth mechanism during periods of strong surface heating. Otherwise, the thickness of the CBL can only reach 2–3 km in summer, and it is unlikely that an SCBL will develop. Strong sensible heating is the key trigger of the positive feedback cycle growth mechanism between the CBL and the RL, which explains why the SCBL phenomenon can only occur in dry areas, with intense surface heating in summer.

Preparation of the plasma electrolytic oxidation coating on Mg[sbnd]Li alloy and its thermal control performance

When the spacecraft runs in orbit, wild temperature swings always affect the inner instruments under strong solar radiation. Therefore, the MgLi alloy is not suitable as aerospace pace materials before modified with thermal control coating. In this work, the plasma electrolytic oxidation (PEO) was employed to prepare thermal control coatings on MgLi alloys with various Li contents (4 wt% and 9 wt%) in silicate-based systems. The effects of Li content and electrolyte composition on the coating formation and thermal control performance of PEO coating were studied by various methods. The results show that all of PEO coatings were main composed of crystalline MgO and Mg2SiO4. With the increases of electrolyte concentration, the obtained coating had large thickness and roughness, which improved the emissivity and solar absorptance. A possible influence mechanism of the spark discharges on the surface morphologies of PEO coatings were proposed: the dominant spark discharges on Mg4Li were from the excitation of Na ions, inducing relatively more electrolyte compositions to form the coating (particle-clusters); The dominant discharges on Mg9Li were from the excitation of Na ions and Li ions, facilitating relatively more alloy ingredients to make up the coating (protuberances). When prepared in the electrolyte with high concentration, the Mg4Li coating possessed more nano-particles clusters, and Mg9Li coating possessed more protuberances, which endowed the Mg4Li coating with lower solar absorptance and the Mg9Li coating with higher emissivity.Besides, the Mg9Li coating prepared in the electrolyte containing 20 g/L sodium silicate, 2.0 g/L NaF and 2.0 g/L NaOH had the optimal thermal control performance.

Aircraft measurement campaign on summer cloud microphysical properties over the Tibetan Plateau

We reported the first aircraft campaign on summer cloud microphysical properties conducted in July of 2014 over the Tibetan Plateau during the third Tibetan Plateau Atmospheric Sciences Experiment (TIPEX-III), and demonstrated that the summer clouds over the Tibetan Plateau were primarily characterized as mixed-phase cumulus clouds induced by strong solar radiation heating. Moreover, the characteristic number concentration of cloud droplets (2~50 μm in diameter) in developing cumuli was around 10 cm−3, which was about 1~2 orders of magnitudes lower than other continent and ocean regions, and that for large drops (>50 μm in diameter) was around 10−3 cm−3, which was also lower than other regions. The droplet spectrum distributions (DSDs) of cloud drops were much wider than other regions, indicating that the cumulus clouds over the plateau could form precipitation easier than that in other regions. Ice microphysics was characterized as very active glaciation and riming processes with high supercooled water content, which caused the formation of high concentration of graupel particles in clouds. The findings of this study suggest that these unique cloud microphysical properties formed by the high topography and clean environment of the Tibetan Plateau could induce higher precipitation efficiency when airflow passed over the plateau, so that the plateau could act as a regional “water tower”.

Chemistry of new particle growth during springtime in the Seoul metropolitan area, Korea

New particle formation and growth events (NPEs) were frequently observed (17 out of 60 days) during April 14 to June 15, 2016 in the Seoul metropolitan area (SMA). In this study, we investigated the chemical mechanisms of new particle growth based on measurements conducted using an aerodyne high resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and a scanning mobility particle sizer (SMPS). Both instruments were deployed as a part of the KORUS-AQ campaign (Korea-US Air Quality study). NPEs usually started around noon time between ∼11:00 and 14:00 with the appearance of an ultrafine mode peaking between ∼20 and 30 nm (in mobility diameter, Dm, measured by the SMPS operating in the range 18–947 nm) followed by the growth of this modal diameter to 50–100 nm during the next ∼6–18 h. The growth rate of NPEs during the study was on average 4.48 ± 1.39 nm/h. Comparing to the non-NPE days in SMA, NPEs occurred under the conditions of lower concentration of preexisting particles, higher ozone (48 vs 30 ppb), stronger solar radiation (2.53 vs1.20 MJ/m2), and drier air (34 vs 65%). The HR-ToF-AMS size-resolved aerosol composition measurements show that LV-OOA (low volatility oxidized organic aerosol) and sulfate were major contributors to the growth of new particles at the initial stage of NPE which mostly occurred during daytime and that the later growth which extended into nighttime was mainly contributed by semi-volatile condensable species such as nitrate and SV-OOA (semi-volatile oxygenated organic aerosol). Generally new particles grew to a modal size of ∼80 nm (12 out of 17 NPEs) over the course of an event, however, particles could grow to larger than 100 nm when nitrate concentration was high whereas particle growth was limited to ∼ 50 nm when nitrate, SV-OOA or sulfate were low.

Elucidating cloud vertical structures based on three-year Ka-band cloud radar observations from Beijing, China

Elucidating the vertical structures of clouds is key to reducing the uncertainty in cloud-induced climate forcing; however, we do not yet know explicitly about the cloud structures that form over Beijing, China, and how they vary. In this paper, we document vertically resolved cloud structures and their climatological variation based on three-year (1 January 2015 to 31 December 2017) ground-based Ka-band (35 GHz) millimeter-wave cloud radar (MMCR) measurements. Cloud top height (CTH) and radar reflectivity are higher in summer and autumn than in spring and winter. We verified the MMCR measurements of the CTH and cloud base height (CBH) independently based on observations from the Himawari-8 and CL51 ceilometer at the same station, respectively. The CTH decreased as the thickness of the cloud layer increased. This may have been due to the mechanism used to determine the CTH, which was based on data from the satellite infrared channel. There were two peaks in the CBH distribution, located at 0–1 km and 5–6 km, whereas the frequency of the CTH peaked at an altitude of 9–10 km, between 1200 and 1800 LST. Precipitating clouds tended to be located at lower altitudes and exhibited stronger radar reflectivities than non-precipitating clouds. The cloud frequency tended to peak in autumn and reached a minimum in winter. In terms of the seasonality of clouds at various levels, middle- and high-level clouds were dominant over Beijing, with high and low (precipitating) clouds concentrated between May and October. Mid-altitude clouds occurred more frequently in winter and spring. CTH peaked in summer due to the strong solar radiation received by the surface. In contrast, minimum CBH occurred in winter. The cloud heights were higher and radar reflectivities larger than reported in previous studies. These results are correlated with urban warming effects. Understanding the properties of clouds will not only be of benefit to researchers carrying out cloud forcing studies, but will also provide key validation data for climate model simulations.

Acute effects of UVB radiation on the survival, growth, development, and reproduction of Daphniopsis tibetana Sars (Crustacea: Cladocera).

Daphniopsis tibetana Sars lives in elevation, usually with strong solar UV radiation. We speculate that UV may have an effect on the ecology and evolutionary biology of this species. However, the regulatory effect and mechanism of UV on D. tibetana have not been studied previously. Here, our results showed that UVB could act as a positive factor in the relative body lengths, reproductive parameters, and population growth parameters of D. tibetana when UVB radiation is 20-170mJcm-2, compared with the control group. Strikingly, these parameters were highest at 120mJcm-2. To explore the mechanism underlying the UVB irradiation effects, we conducted a transcriptome analysis using the Trinity platform. The results indicated that differentially regulated genes were mostly enriched in lipid transport and lipid localization by Gene Ontology (GO) enrichment analysis of 146 differentially expressed genes (83 upregulated and 63 downregulated). This is the first study of UVB radiation of D. tibetana to reveal genes that may have crucial roles in survival, growth, and reproduction and could be candidates for future functional studies. Additionally, the study could supply a substantial resource for investigating and elucidating lipids that could play important roles in a physiological context.

Experimental Study on Performance Test of Serpentine Flat Plate Collector with Different Pipe Parameters and A New Phase Change Collector

Abstract In this paper, the thermal performance of serpentine pipe flat plate collectors with different pipe diameters and pipe spacings was tested by experiments. On this basis, two phase change materials with high melting point (70 °C) and low melting point (15 °C) were laid on the upper and lower parts of the pipeline to enhance the frost resistance and high temperature resistance of the collector. The experimental results show that under strong solar radiation conditions, high-melting phase change materials can absorb a lot of heat when the water temperature of the collector is high, thereby slowing down the water temperature rise and avoiding overheating, and when the collector is cooled, phase change can be effectively utilized to slows down the rate of temperature drop of the collector, so as to achieve reasonable utilization of the overheating of the collector; in the low temperature environment, the low melting point phase change material can significantly reduce the cooling of the collector and improve the frost resistance of the collector. The placement of the two kinds of different melting point phase change materials was investigated, and the results show that the low-melting phase change material under the pipe is more conducive to the collector antifreezing. However, for the hot regions, the high-melting phase change material placed at the top of the pipe is more conducive to preventing overheating.

Temperature and Circulation Dynamics in a Small and Shallow Lake: Effects of Weak Stratification and Littoral Submerged Macrophytes

In this paper, the effects of littoral submerged macrophytes on weak stratification conditions in a small and shallow lake are investigated. Diverse submerged macrophytes occupying a large portion of the littoral zone act as resistance to water motions and affect lake hydrodynamics. Strong solar radiation and mild wind forcing typically occurring during the summer season result in weak stratification characterized by a diurnal cycle with a temperature differential of 1–3 °C. Temperature and circulation dynamics of a small and shallow lake are depicted by extensive field measurements and a three-dimensional non-hydrostatic model with a generic length scale (GLS) approach for the turbulence closure and drag forces induced by macrophytes. Results show that the effects of macrophytes on velocity profiles are apparent. In the pelagic area, the circulation patterns with and without macrophytes are similar. The velocity profile is generally characterized by a two-layer structure with the maximum velocity at both the water surface and the mid-depth. In contrast, inside the littoral zone, the mean flow is retarded by macrophytes and the velocity profile is changed to only one maximum velocity at the surface with a steeper decrease until 2.0 m depth and another slight decrease to the lake bottom. From the whole lake perspective, littoral macrophytes dampen the horizontal water temperature difference between the upwind side and download side of the lake. Macrophytes promote a stronger temperature stratification by retarding mean flows and reducing vertical mixing. Overall, this study shows that the temperature structures and circulation patterns under weak stratification conditions in a small and shallow lake are strongly affected by littoral vegetation.

Impact of Meteorological Factors on the Ozone Pollution in Hong Kong

Based on ozone monitoring and meteorological data from 2000 to 2015 in Hong Kong, the characteristics of ozone pollution and the influence of meteorological factors on the ozone pollution were analyzed. The results show that:① A seasonal variation of the ozone concentration in Hong Kong is notable:autumn > spring > winter > summer. Days of ozone exceeding the standard value are concentrated in summer and autumn and rarely occur in winter and spring. ② The annual mean ozone concentration of the maximum daily 8-h average (MDA8) in Hong Kong increases from 2000 to 2015, with an average growth rate of 0.77 μg·(m3·a)-1. The 90th percentile concentration of the ozone MDA8 also increases, with an average rate of 1.49 μg·(m3·a)-1. ③ Higher temperatures are necessary for ozone pollution in Hong Kong. The higher the temperature is, the more ozone pollution likely occurs. ④ In most cases, the ozone concentration is negatively correlated with the relative humidity. The higher the relative humidity is, the lower are the ozone and 90th percentile concentrations in Hong Kong. ⑤ When ozone pollution occurs in Hong Kong, prevailing winds tend to shift from northerly or easterly to westerly. In addition, with the increase of the wind speed, the average ozone concentration changes little, but the 90th percentile ozone concentration significantly decreases. ⑥ Precipitation and cloud cover are important factors affecting the ozone concentration. Weather conditions without or with little rain for many consecutive days are necessary for the occurrence of ozone pollution events. However, with the increase of the cloud cover, the average ozone and 90th percentile concentrations continue to decrease. ⑦ In the case of a total solar radiation ≤ 20 MJ·m-2 or sunshine duration ≤ 10 h, the ozone concentration is positively correlated with the solar radiation and sunshine duration. However, in the case of intense solar radiation (total solar radiation>20 MJ·m-2 or duration of sunshine>10 h), the ozone concentrations decrease with increasing solar radiation or duration because strong solar radiation often occurs in the background of sunny weather after rain. At the same time, southerly winds from the sea often prevail, making it difficult for ozone pollution to occur in Hong Kong. ⑧ Ozone excess days in Hong Kong are often accompanied by changes of a series of meteorological conditions including less rain on sunny days, stronger radiation, higher boundary layer height, lower relative humidity, smaller wind speeds, and higher temperatures. The end of the pollution process is accompanied by the opposite weather changes.