Diurnal Distribution Research Articles

2 Vegetation characteristics and diurnal periods influenced the landscape-use pattern of goats and sheep in woodlands

Abstract Woodlands dominates the landcover in the Southeast and offer great opportunities for expanding small-ruminant grazing. However, unmanaged understory shrubs grown beyond animals’ access minimizes the utilization of such vegetation. Managing the understory shrubs and non-target trees to lower heights may increase animals’ access to woodland vegetation and alter the landscape-use patterns of animals. The study objective was to determine the effect of vegetation height on the behavior and distribution of Kiko wethers and Katahdin rams in woodlands. The study was conducted in six woodland plots (0.4-ha each) containing southern pine and hardwood trees and numerous understory vegetation. The non-pine species were either cut to one of the heights from the ground level (0 m, 0.91 m, 1.52 m) or left uncut (control). Once the cut vegetation grew back and attained the full canopy, Kiko wethers (8, 48–50 months old, 72.8 ± 2.29 kg live weight) and Katahdin rams (5, 29–32 months old, 95.5 ± 4.31 kg live weight) were rotationally stocked in separate plots (3 plots each species), and their diurnal (dawn-dusk) behaviors and distribution patterns monitored when they were in each plot during the summer of 2018. Data were analyzed in Kruskal-Wallis rank sum test in R. Both wethers and rams visited the control treatment the least, rams grazed mostly in areas with short vegetation (0 m), and wethers visited more to areas with higher vegetation (1.52 m) than rams for feeding (P < 0.001), which was predominant during the post-midday period (3:00-dusk) (P < 0.0001). Browsing was the dominant feeding behavior of wethers (39% browsing vs. 4% grazing), while rams’ feeding behavior was dominated with grazing (24% grazing vs. 12% browsing). Lying was the dominant diurnal behavior of both wethers (46%) and rams (35%), and predominant during the midday period (11 a.m.-3:00 p.m.) (P < 0.05). Vegetation heights and diurnal period highly influenced animals’ behavior.

Numerical evaluation of urban green space scenarios effects on gaseous air pollutants in Tehran Metropolis based on WRF-Chem model

Although positive environmental aspects of increasing urban vegetative spaces are undeniable, using predefined or unmanaged long-term green programs may cause undesirable and unexpected impacts on the air quality in megacities. In this study, the mitigation potential of three green spaces development scenarios (expansion of surface vegetative area, Green Roof development and combination of surface and roof greenery) on three gaseous air pollutants (O3, SO2 and NO2) concentrations in Tehran Metropolis in an early summertime period is analyzed using coupled Weather Research and Forecasting model with chemistry (WRF/Chem), single-layer urban canopy model (SLUCM) and biogenic emission from Model of Emissions of Gases and Aerosols from Nature (MEGAN). Current results indicate that general patterns of diurnal distribution of SO2 and NO2 are totally controlled by the location of anthropogenic sources of pollutants in the south and the city center, beside the prevailing wind field over the city of Tehran. Ozone distribution follows the diurnal advection from the northern and eastern sub-urban areas and distribution of primary pollutants such as NO2. By conducting green scenarios, reduction in the wind speed, variations in pollutants dry deposition velocities which are directly affected by the boundary layer and surface properties, and pollutants deposition fluxes are observed. Alterations in deposition fluxes are not uniform across the city area and clearly conform to changes in pollutants concentrations. In addition, the shallower (deeper) boundary layer height and the buoyancy forcing due to the reduction (increase) in near-surface air temperature cause less (more) vertical mass transport during the day (night), which in both situations could have negative impacts on the air quality since under lower wind speed condition and less convective upward transfer, polluted air near the surface can be trapped. The defined scenarios have shown different impacts over the city of Tehran with the complex urban morphology so, suggestion of the most efficient summertime green policy with the minimum negative feedbacks is not conceivable.

Special Electromagnetic Interference in the Ionosphere Directly Correlated With Power System

Power line emissions and harmonic radiations have been recognized as a kind of electromagnetic interference to the near-Earth space environment. This study demonstrates their direct dependence on the terrestrial power system used. By examining electric field data obtained by the satellite DEMETER, we observed several typical 50-, 60-, and 180-Hz emissions above Japan originating from a 50-Hz/60-Hz hybrid power system over two consecutive days. We analyzed all the emission events of 50 Hz and its harmonic frequencies detected as DEMETER flew over China. In 2009, the number of power line harmonic radiation (PLHR) events suddenly increased when multiple ultra-high-voltage transmission lines were built and put into operation. Based on the seasonal and diurnal distribution of the observed events, we conclude that PLHR is closely related to power consumption as we observe that it is mainly distributed above highly populated places and as such the radiation may originate from the low-voltage power distribution network. The magnitude and frequency of electrical currents flowing through transmission lines during both regular and faulty operation that can generate emissions reaching the ionosphere are analyzed for different voltage classes.

Scale-free and characteristic time in urban soundscape

In this work we study the statistic of the nocturnal and diurnal urban soundscape. Our focus is on the temporal distribution of the quiet-times (background noise) and sound-times (noise bursts) in audio recordings. We analyzed one hour samples uninterruptedly of urban environment soundscape for ten days and nights. The histogram for the nocturnal quiet-time follows a power-law like scale-free distribution spanning three orders of magnitude, from 0.03s to 30s, with exponent α=1.65±0.03. The diurnal histogram distributions of the quiet-times reveals a power-law with the same exponent value, but the statistic distribution, in this case, shows an overlap of an additional urban acoustic phenomenon corresponding to time duration above 1s. On the other side, the sound-times, both diurnal and nocturnal, follow a log-normal distribution with mean value around 0.1s, which characterizes a typical temporal characteristic-scale for the duration of sounds in the urban soundscape. We discuss, in the paper, the coexistence between the scale-free distribution of silences and the typical time scale of sounds.

Performance of S-CO2 Brayton Cycle and Organic Rankine Cycle (ORC) Combined System Considering the Diurnal Distribution of Solar Radiation

This paper researches the performance of a novel supercritical carbon dioxide (S-CO2) Brayton cycle and organic Rankine cycle (ORC) combined system with a theoretical solar radiation diurnal distribution. The new system supplies all solar energy to a S-CO2 Brayton cycle heater, where heat releasing from the S-CO2 cooler is stored in the thermal storage system which is supplied to the ORC. Therefore, solar energy is kept at a high temperature, while at the same time the thermal storage system temperature is low. This paper builds a simple solar radiation diurnal distribution model. The maximum continuous working time, mass of thermal storage material, and parameter variations of the two cycles are simulated with the solar radiation diurnal distribution model. 10 organic fluids and 5 representative thermal storage materials are compared in this paper, with the mass and volume of these materials being shown. The longer the continuous working time is, the lower the system thermal efficiency is. The maximum continuous working time can reach 19.1 hours if the system provides a constant power output. At the same time, the system efficiency can be kept above 38% for most fluids.

Characterization of nighttime formation of particulate organic nitrates based on high-resolution aerosol mass spectrometry in an urban atmosphere in China

Abstract. Organic nitrates are important atmospheric species that significantly affect the cycling of NOx and ozone production. However, characterization of particulate organic nitrates and their sources in polluted atmosphere is a big challenge and has not been comprehensively studied in Asia. In this study, an aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) was deployed at an urban site in China from 2015 to 2016 to characterize particulate organic nitrates in total nitrates with a high time resolution. Based on the cross-validation of two different data processing methods, organic nitrates were effectively quantified to contribute a notable fraction of organic aerosol (OA), namely 9 %–21 % in spring, 11 %–25 % in summer, and 9 %–20 % in autumn, while contributing a very small fraction in winter. The good correlation between organic nitrates and fresh secondary organic aerosol (SOA) at night, as well as the diurnal trend of size distribution of organic nitrates, indicated a key role of nighttime local secondary formation of organic nitrates. Furthermore, theoretical calculations of nighttime SOA production of NO3 reactions with volatile organic compounds (VOCs) measured during the spring campaign were performed, resulting in three biogenic VOCs (α-pinene, limonene, and camphene) and one anthropogenic VOC (styrene) identified as the possible key VOC precursors to particulate organic nitrates. The comparison with similar studies in the literature implied that nighttime particulate organic nitrate formation is highly relevant to NOx levels. This study proposes that unlike the documented cases in the United States and Europe, modeling nighttime particulate organic nitrate formation in China should incorporate not only biogenic VOCs but also anthropogenic VOCs for urban air pollution, which needs the support of relevant smog chamber studies in the future.

Comparison on aerosol physicochemical properties of sea and land along the coast of Bohai, China

The Bohai Sea is one of four major sea areas adjacent to China, air pollution is becoming an issue along the Bohai coast owing to rapid industrialization and urbanization. To analyze the sea–land interaction and its influence on regional particulate pollution, a comparison of sea and land aerosol physicochemical properties was carried out using observations and numerical simulation. Three observation sites, an ocean site on the Bohai Sea, a coastal station in the Tanggu district, and an inland station in Tianjin City were established. The movements and interactions of pollutants between land and sea were determined, and it was found that the convergence of sea–land breezes produced an ascending motion, which served to concentrate pollutants, with the polluted central body of air extending upward to a height of 200 m. The proportion of fine particle aerosols was greater in Bohai than at the inland site, although aerosol pollution levels over land were higher than those over ocean. The annual average aerosol optical depths, at the Bohai and inland sites were 0.74 and 0.82, and the annual average wavelength indices were 0.97 and 0.90, respectively. The spatial distribution of PM2.5 concentration was characterized as inland > Bohai > coastal zone, which reflected local emissions, the special terrain and meteorological conditions of the coastal zone. Higher concentrations of EC, SO42−, Mg, Al, V, and Cr at Bohai, compared to the other sites, might have been due to ship emissions on the Bohai Sea, while industrial development could explain why the maximum concentrations of Fe and NO3− were observed at the coastal site. In addition, the diurnal distribution of SO42− exhibited a trend opposite to that for humidity, both at the Bohai and coastal sites, which indicated that, in addition to secondary transformation under high humidity conditions, sulfate emission sources were located locally.

Spatial and Temporal Features in Diurnal Distributions of Strong Earthquakes at the Garm Research Area

The spatial pattern of diurnal variations in the temporal sequence of relatively strong earthquakes in the Garm Research Area in Tajikistan for 1955–1991 has been investigated. The earthquakes that occurred in the daytime and at night, as well as the value characterizing their difference, have been mapped separately. The differences in diurnal seismicity variations in a few local zones have been discussed. Compact areas with major daytime seismic events presumably related to quarry explosions have been identified. They are located far beyond the Garm Research Area at a considerable distance from the network of seismic stations. The sources of man-induced seismic events have not been found within the Garm Research Area. The identified large connected areas combine the cells dominated either by day or night earthquakes.

Diurnal behavior of Kiko wethers in southern-pine silvopastures planted with warm-season forages

Goats are the common grazing livestock integrated into the silvopasture system. Previous grazing studies with goats in southern-pine silvopastures showed significant debarking of pine trees during the cool-season grazing period. However, goats’ behavior in this system during the warm-season grazing period has not been previously reported. The objective of the study was to determine the diurnal behavior and distribution pattern of Kiko wethers in southern-pine silvopastures planted with warm-season forages. The study was conducted at the Atkins Agroforestry Research and Demonstration Site, Tuskegee University, Tuskegee, Alabama, USA. The study site consisted of three silvopasture plots (0.4-ha each) comprising 12-year-old longleaf (Pinus palustris Mill.) and loblolly (Pinus taeda L.) pines, with a tree density of 402 trees ha−1 (loblolly: longleaf ratio – 1.27). Study plots were divided into three zones, and three different warm-season forages were grown in these zones. Forage samples were collected and analyzed for productivity and quality. Ten Kiko wethers (2.75–2.90-year-old, 62.9 ± 1.56 kg BW) were rotationally stocked in the study plots, and their diurnal behavior and distribution pattern studied when they were in each study plot. Data were analyzed using Kruskal–Wallis rank-sum test in R-package. Grazing was the predominant diurnal behavior (46%) shown by Kiko wethers followed by staying in shelters (22%) and lying (17%). Wethers did not show any pine debarking behavior. Wethers spent predominant diurnal time in Zone 3 (42%) planted with sericea lespedeza (Lespedeza cuneata (Dum. Cours.) G. Don) that had the highest quality forages followed by Zone 1 (31%) planted with bahiagrass (Paspalum notatum Flueggé). Kiko wethers could be safe to stock in southern-pine silvopastures containing 12-year-old trees during the warm-season grazing period.

Geographical Distribution of Thundersnow Events and Their Properties From GPM Ku‐Band Radar

AbstractSix‐years (2010–2015) of snow lightning characteristics and climatology, including seasonal, diurnal, and surface temperature distribution, are generated. The World Wide Lightning Location Network (WWLLN) and the National Lightning Detection Network lightning observations are collocated with Modern‐Era Retrospective Analysis for Research and Application (MERRA‐2) temperatures. Cold season lightning events are identified as lightning with the MERRA‐2 two‐meter surface temperature colder than 0 °C and then further classified as snow lightning or thundersnow, when the entire vertical temperature profile is below 2 °C, and as freezing rain lightning when there is a temperature warmer than 2 °C somewhere in the column above the freezing surface. The statistics of snow lightning events from WWLLN and National Lightning Detection Network are well matched and are consistent with the climatology of thundersnow days reported at ground‐based stations over the United States. Using 4 years of observations from the Global Precipitation Measuring Mission Ku band radar, 443 Thunder Snow Features (TSFs) are defined, having a contiguous area of nonzero near surface snow precipitation derived from the Ku band radar and MERRA‐2 data, along with collocated WWLLN lightning flashes. The majority (about 394) are found over high mountainous regions such the Himalayas, Tibet, the Andes, and the Zagros mountain regions. Low‐elevation TSFs (45) are observed over the continental and coastal regions. Though only a small number of TSFs are identified with 4 years of Global Precipitation Mission data, most TSFs have maximum radar reflectivity above 30 dBZ at temperature colder than −10 °C, which indicates the importance of the noninductive charging process in these events.

Analysis of spatial and temporal distribution patterns of temperatures in urban and rural areas: Making urban environmental climate maps for supporting urban environmental planning and management in Hiroshima

Urban planning incorporating mitigation of the urban warming which is due to urban heat island phenomena and climate change is needed. However, such planning is not realized. That is apparently because the urban climate phenomenon is difficult to understand for stakeholders: citizens, planners, architects, specialists, and so on. Urban Environmental Climate Maps (UECMs) are therefore proposed as one of the decision support tools for the urban warming mitigation. Accordingly, the authors intend to produce UECMs in Hiroshima as the final goal of this study. Therefore, for the production of UECMs, this study aims to analyze the relationship between spatial temperature distribution and the comprehensive factors using observed data and numerical simulation results and perform climate zoning based on these results in Hiroshima. This study progressed via the following steps: 1) classifying Hiroshima area into the plain area and the mountain area; 2) analysis on the causes of temperature distribution based on observed data in the plain area; 3) analysis on the effect of sea breeze on summer diurnal temperature distribution patterns; 4) analysis on the causes of temperature distributions based on observed data in the mountain area; and 5) urban climate zoning and construction of UECMs.

Confinement influenced the diurnal behavior of Katahdin rams and Kiko wethers in southern-pine silvopastures

Previous studies with Kiko wethers rotationally stocked in southern-pine silvopastures showed a significant debarking of 10-11-year-old pine trees during winter and spring. There is a need to identify suitable animals and management strategies to protect trees in silvopastures. The objective of the study was to determine the effect of confinement on diurnal behavior and distribution pattern of Katahdin rams and Kiko wethers cograzing in southern-pine silvopastures during the cool-season grazing period. Diurnal behavior and distribution pattern of Kiko wethers (n = 6; 61.5 ± 1.58 kg live weight) and Katahdin rams (n = 6; 72.7 ± 4.80 kg live weight) were monitored in two sets of studies: (1) animals were rotationally stocked in three silvopasture plots with confinement (plot-gate closed), and (2) the same study was repeated with non-confinement (plot-gate open), allowing access to wooded area and open space located outside the silvopasture plots. Rams did not debark pine trees irrespective of confinement. They spent less time (17%) grazing (p < 0.05) and stayed out of the silvopasture plots for a significant period (42%) with non-confinement. Wethers showed some debarking (2%) of pine trees with confinement, but none without confinement. With non-confinement, wethers’ grazing time decreased (53%) (p < 0.0001), browsing time increased (48×) (p < 0.0001), and distribution outside the silvopasture plots remained significant (73%). Katahdin rams were found safe to use in southern-pine silvopastures consisting of 12-year-old longleaf and loblolly pine trees; however, non-confinement would be necessary while using Kiko wethers to safeguard young southern-pine trees in small silvopasture plots containing similar understory vegetation during the cool-season grazing period.

The climatology of severe convective storms in Tehran

The severe convective storm (SCS) events that affect Tehran during spring and early summer have potential to cause devastating effects. To study SCSs in Tehran, a climatological analysis is carried out using surface data of Tehran's Mehrabad station from 1961 to 2015 and the NCEP/NCAR reanalysis data to compute the large-scale and the local stability indices. Based on the maximum wind speed, the events are classified into three categories consisting of convective storm (CS), severe convective storm (SCS) and extremely severe convective storm (ESCS).The annual frequency of occurrence of all three categories exhibit decreasing trends during the period of study. Late spring and early summer (April to June) are the favorite times for the SCS and ESCS, and the whole spring is for CS events. In diurnal distribution, for the CS and SCS, the peak occurs at 12–15 UTC. Generally, in response to diurnal surface heating, CS events tend to develop during early- and mid-afternoon, and SCS events during late afternoon. For the months of April to June, while the large-scale stability indices point to a positive trend, no clear trend can be inferred from the examination of local stability indices. While a partial explanation for the decreasing trend of the ESCS is provided based on the large-scale stability indices and the negative trend in the frequency of simultaneous occurrence of the local stability indices, it is likely that the decreasing trends observed for the convective storms are also due to the local urban effects.

A New Solar Radiation Model for a Power System Reliability Study

The dwindling number of conventional power resources and its environmental impact has motivated a transition to renewable energy sources, such as solar power. Evaluating the reliability of solar power integration into power networks can help decision makers gauge the feasibility of their solar power projects. However, the stochastic and non-stationary nature of solar radiation is difficult to be modeled and can even hinder an accurate evaluation of reliability. A good solar model for accurately assessing solar-power-integrated systems should be able to retain the original statistical properties of the sampled solar radiation data. Therefore, this paper aims to develop a new robust and easy-to-use methodology for simulating solar radiation. The proposed model was compared with four other models, including the clearness index, auto-regressive moving average, and two probability-distribution-based models. Five statistical tests, namely, F-test, diurnal distributions, partial auto-correlation function (PACF), mean, and standard deviation, were performed for the comparison. The comparison results indicate that the proposed method effectively retains the statistical properties of the original data and outperforms all other models in the tests. Therefore, the proposed model can be used for assessing solar-power-integrated power systems.

Prediction of Symmetrical and Asymmetrical of Diurnal Global Solar Irradiance Distribution—New Approach

A simple formula to predict the received global solar irradiance q(t), W/m2 for clear days is suggested on pure theoretical basis. It is expressed in terms of the length of the local day time td which is well defined in literatures on meteorological basis. The introduced distribution is also a function of the maximum value of the daily received irradiance qmax. which in turn is expressed in term of the solar constant. This renders the trial to be a closed system. Thus the obtained distribution is not a semi empirical one. Both cases of symmetrical and asymmetrical distributions for q(t) are considered. For its simplicity it can be easily integrated along the length of the day to get the daily totals of solar energy received by unit horizontal area. This is important for practical applications. Comparison between computed according to the present model and published experimental meteorological data in Barcelona (Spain), Hong Kong (China), Jeddah and Makkah (Saudi Arabia) is given as illustrative examples. Better fitting relative to the published trials for the same locations are obtained. The introduced model itself gives good fitting for the intermediate intervals points of the local day time which is the more effective region. The estimated relative error is 12% for Hong Kong, and it is 7% for Barcelona, Jeddah and Makah.

宁夏日光温室光照强度日变化分布研究

宁夏日光温室光照强度日变化分布研究

PSV-4 Confinement Influenced the Diurnal Behavior and Distribution Pattern of Katahdin Rams and Kiko Wethers in Southern-pine Silvopastures.

PSV-4 Confinement Influenced the Diurnal Behavior and Distribution Pattern of Katahdin Rams and Kiko Wethers in Southern-pine Silvopastures.

Diurnal distribution of carbohydrates and fat affects substrate oxidation and adipokine secretion in humans

A diet in which fat is mainly eaten in the morning and carbohydrates mainly in the evening (compared with the reverse order) was recently shown to worsen glycemic control in people with prediabetes. We investigated the effects of these dietary patterns on energy metabolism, and on the daily profiles of circulating lipids, adipokines, and inflammatory markers. In a randomized controlled crossover trial, 29 nonobese men (with normal glucose tolerance, n=18; or impaired fasting glucose/glucose tolerance, n=11) underwent 2 isocaloric 4-wk diets: 1) carbohydrate-rich meals until 1330 and fat-rich meals between 1630 and 2200 (HC/HF); or 2) the inverse sequence of meals (HF/HC). During a 12-h clinical investigation day after each intervention period, 2 meal tolerance tests were performed, at 0900 and 1540, respectively. Substrate oxidation and concentrations of circulating lipids, adipokines, and cytokines were assessed pre- and postprandially. The postprandial inflammatory response in leukocytes was analyzed ex vivo. Fasting carbohydrate oxidation decreased (P=0.004) and lipid oxidation increased (P=0.012) after the HC/HF diet. Fasting concentrations of blood markers did not differ between diets. The diets modulated the daily profiles of carbohydrate oxidation, lipid oxidation, and β-hydroxybutyrate, although the average daily values of these parameters showed no difference between the diets, and no interaction between diet and glucose tolerance status. Diurnal patterns of triglycerides, low-density lipoprotein cholesterol, leptin, visfatin, and of LPS-induced cytokine secretion in blood leukocytes were also modulated by the diets. Average daily concentrations of leptin (P=0.017) and visfatin (P=0.041) were lower on the HF/HC diet than on the HC/HF diet. Diurnal distribution of carbohydrates and fat affects the daily profiles of substrate oxidation, circulating lipids, and cytokine secretion, and alters the average daily concentrations of adipokine secretion in nonobese nondiabetic humans. The study was registered at clinicaltrials.gov as NCT02487576.

Aerobiology of Cupressaceae in Porto city, Portugal

In the last years, pollen-related respiratory allergies have increased worldwide. In the case of Cupressaceae pollen, allergy symptoms appearing during the winter are often confused with generic respiratory diseases such as the common cold, influenza syndrome, among others. The aim of our study was to monitor the atmospheric of Cupressaceae pollen in the city of Porto, investigate its diurnal variation, as well as find the meteorological factors influencing its atmospheric concentration. Airborne pollen sampling was performed using a 7-day Hirst-type volumetric spore trap for 5 years (2013–2017). Cupressaceae main pollen season, interannual and diurnal variations, as well as correlations with the meteorological parameters were determined. During the study period, 2015 was the year that registered the highest annual pollen concentration, while 2016 presented the lowest. Cupressaceae pollen season occurred during the winter, being February the month with the highest concentration. The diurnal distribution pattern presents a well-defined peak concentration in the morning hours (9 a.m.–12 a.m.), which decays abruptly in the early afternoon. Finally, airborne pollen concentration and meteorological factors presented significant correlations, with temperature being the most influent variable.

Spatiotemporal characteristics of precipitation diurnal variations in Chongqing with complex terrain

Using the hourly precipitation data observed at 34 gauge stations in Chongqing during 1991–2012, the spatial and temporal characteristics of the precipitation amount (PA), precipitation intensity (PI), precipitation frequency (PF), and their diurnal cycles are analyzed. Results show that the PA increased from the western to eastern Chongqing in spring and autumn. The summer precipitation was dominant throughout the year, and the PA in the basin was larger than in the eastern and middle mountainous area, which was different from in spring and autumn. The nocturnal precipitation had a quasi-stationary feature. The diurnal peaks of the PA/PI/PF mainly appeared from midnight to early morning. The amplitude of the PF was significantly greater than that of the PI and thus determined the characteristics of diurnal variation of the PA. In terms of the distribution of peak time of precipitation, this study reveals a time lag indicating the peak time was later in the northeast than in the southwest Chongqing. The complex terrain played an important role in the difference of diurnal cycle of precipitation in different areas. The stations in the southwest Chongqing are largely located in the Sichuan Basin, while the stations in the eastern and middle Chongqing are located in the mountainous area surrounding the basin. By selecting 16 representative stations in two types of terrain for analysis, it is shown in the study that the amplitude of diurnal precipitation at the stations in higher terrain was weaker. Moreover, investigating the interval of precipitation associated with the diurnal distribution of lightning reveals that the enhancement of precipitation in the mountainous area in the afternoon was mainly caused by the short-time strong rainfall resulting from the convection.