Variations of precipitation characteristics during the period 1960–2014 in the Source Region of the Yellow River,China

Precipitation, a natural feature of weather systems in the Earth, is vitally important for the environment of any region. Under global climate change condition, the characteristics of precipitation have changed as a consequence of enhanced global hydrological cycle. The source region of the Yellow River（SRYR）, locating within the Qinghai-Tibet Plateau, is sensitive to the global climate change due to its complex orography and fragile ecosystem. To understand the precipitation characteristics and its impacts on the environment in the region, we studied the characteristics of rainy days and precipitation amount of different precipitation classes, such as light（0–5 and 5–10 mm）, moderate（10–15, 15–20 and 20–25 mm） and heavy（≥25 mm） rains by analyzing the precipitation data of typical meteorological stations in the SRYR during the period 1961–2014, as well as the trends of persistent rainfall events and drought events. Results showed that annual average precipitation in this area had a non-significant（P〉0.05） increasing trend, and 82.5% of the precipitation occurred from May to September. Rainy days of the 0–5 mm precipitation class significantly decreased, whereas the rainy days of 5–10, 10–15, and 20–25 mm precipitation classes increased and that of ≥25 mm precipitation class decreased insignificantly. The persistent rainfall events of 1-or 2-day and more than 2-day showed an increasing trend, with the 1-or 2-day events being more frequent. Meanwhile, the number of short drought periods（≤10 days） increased while long drought periods（〉10 days） decreased. Since the 0–5 mm precipitation class had a huge impact on the grasslands productivity; the 5–10, 10–15, and 20–25 mm precipitation classes had positive effects on vegetation which rely on the deep soil water through moving nutrients and water into the root zone of these vegetation or through the plant-microbe interactions; the ≥25 mm precipitation class contributed to the floods; and more persistent rainfall events and fewer long drought events inferred positive effects on agriculture. Thus, these results indicate grassland degradation, less risk of floods, and the upgrading impact of climate change on agriculture. This study may provide scientific knowledge for policymakers to sustain the eco-environmental resources in the SYSR.

Effect of Precipitation Characteristics on Spatial and Temporal Variations of Landslide in Kermanshah Province in Iran

Landslide can be defined as the mass movement of sloping slopes under the influence of mass gravity and its stimuli such as earthquakes,floods and flood plains.This phenomenon is one of the natural hazards that every year causes a lot of financial and financial losses in mountainous,rain-fed and seismic areas.Detection of time and the magnitude of landslides are necessary to understand the causes of landslide and to warn potential hazards.In this research,the amount of landslide displacement in Kermanshah province was evaluated by the characteristics of rainfall.To this end,a network of fixed points in and out of the slipping mass of 20 points was created to monitor the amount of displacement on different slip load users and the amount of displacement of each point in 5 time intervals using the Global Positioning System for two-dimensional GPS measurement.The results of the 511-day follow-up showed that the total horizontal displacement of the moving points in the 5 intervals measured at 1658 mm has a monthly displacement rate of 112 mm.Also,the total vertical displacement of moving points at the same time is 899 mm,with a monthly movement rate of 71 mm.Then,precipitation variances such as rainfall,rainfall,precipitation duration,maximum rainfall intensity in the intervals of 10,20,30 and 60 minutes and the average rainfall intensity were calculated and extracted for each of the 5 time periods.The drawing of the vectors of points on the topographic map of the area indicated that the direction of mass movement is in the direction of elevation gradient of the region.The results showed that only the precipitation severity with the landslide had a good correlation.The landslide movement had the highest correlation with average rainfall intensity(R=0.85)and with maximum 30 minutes rainfall(R=0.67),respectively,and other rainfall characteristics like amount,duration,and type of rainfall had not significantly correlated with movement of landslides.

Aging precipitation characteristics and tensile properties of Al-Zn-Mg-Cu alloys with different additional Zn contents

The increase in zinc content in Al-Zn-Mg-Cu alloys provides an effective method to enhance the strength.Transmission electron microscopy(TEM)and tensile test were employed to analyze the microstructure and tensile properties,respectively,of Al-9.3 Zn-2.0 Mg-1.8 Cu alloy(9.3 Zn alloy)and Al-9.8 Zn-2.0 Mg-1.8 Cu alloy(9.8 Zn alloy)with single-and double-stage aging states.The results showed that the two alloys possessed a closed strength under single-stage peak-aging treatment.As for double-stage aging treatment,9.8 Zn alloy had a higher strength values than 9.3 Zn alloy under the same aging regimes.With the second step aging time prolonging,the strength gap was extended.The main precipitates for the two alloys with single-stage peak-aging state were GP zones andη’phase,while there were a majority ofη’phases andηphases for the two alloys under typical double-stage over-aging state.Under double-stage overaging state,the proportion of precipitate with large size for9.3 Zn alloy was larger than that for 9.8 Zn alloy.Besides,a more obvious trend was revealed for the double-stage overaging state.The gap of strength between the two alloys was explained by the difference of precipitation characteristics via interaction mechanism between precipitates and dislocations.

Typhoon Hato's precipitation characteristics based on PERSIANN

Heavy precipitation induced by typhoons is the main driver of catastrophic flooding,and studying precipitation patterns is important for flood forecasting and early warning.Studying the space-time characteristics of heavy precipitation induced by typhoons requires a large range of observation data that cannot be obtained by ground-based rain gauge networks.Satellite-based estimation provides large domains of precipitation with high space-time resolution,facilitating the analysis of heavy precipitation patterns induced by typhoons.In this study,Precipitation Estimation from Remotely Sensed Information Using Artificial Neural Networks(PERSIANN)satellite data were used to study the temporal and spatial features of precipitation induced by Typhoon Hato,which was the strongest typhoon of 2017 to make landfall in China.The results show that rainfall on the land lasted for six days from the typhoon making landfall to disappearing,reaching the maximum when the typhoon made landfall.Hato produced extremely high accumulated rainfall in South China,almost 300 mm in Guangdong Province and Guangxi Zhuang Autonomous Region and 260 mm in Hainan Province.The rainfall process was separated into three stages and rainfall was the focus in the second stage(5 h before making landfall to 35 h after making landfall).

Some Annual Variation Characteristics for the Northern Hemispheric Monthly Mean Precipitation Fields

By the utilization of monthly precipitation data from all stations in the Northern Hemisphere annexed to the 'World Survey of climatology, Vol. 1-15', the distributions of the maximum precipitation months (MPM), the annual relative precipitation (ARP) and the monthly relative precipitation (percent of annual) in January and July are respectively mapped. Moreover the distributions of intermonthly relative precipitation variabilities from January to December are plotted as well. From these figures, the precipitation in the Northern Hemisphere may be classified into three types(continental, oceanic and transitional types) and 17 regions. The precipitation regime may also be divided into two patterns, the global and regional patterns. The global pattern consists of planetary front system and ITCZ and its inter-monthly variation shows the north-and-south shift of the rain belt; the regional pattern consists of the sea-land monsoon and plateau monsoon regime, in which the inter-monthly variation of rain belt shows a east-and-wcst shift.

Spatio-Temporal Change of Atmospheric Precipitation on Territory of North-West of Ukraine

The direction of the trend of precipitation over time is an important characteristic for both theoretical and practical use.The presented study is devoted to the analysis of changes in the territory of the trend of precipitation over the year over time.At the present stage of climate change in the north-west of Ukraine,there is a general tendency to increase rainfall over the year.This trend is not the same across the territory and depends on the height and latitude of the area.The amount of precipitation varies both in space and in time,however,the distribution of the characteristics of the rains themselves(intensity,duration and others)continue to remain similar throughout the territory.The revealed features of changes in the amount of precipitation in space and time can be useful in studying the unevenness of wetting,forecasting floods,changes in erosion activity,etc.

Raindrop Size Distribution Parameters Retrieved from Xinfeng C-Band Polarimetric Radar Observations

The objective of this research was to acquire a raindrop size distribution(DSDs)retrieved from C-band polarimetric radar observations scheme for the first time in south China.An observation period of the precipitation process was selected,and the shape-slope(μ-Λ)relationship of this region was statistically analyzed using the raindrop sample observations from the two-dimensional video disdrometer(2DVD)at Xinfeng Station,Guangdong Province.Simulated data of the C-band polarimetric radar reflectivity ZHHand differential reflectivity ZDRwere obtained through scattering simulation.The simulation data were combined with DSD fitting to determine the ZDR-Λand log10(ZHH/N0)-Λrelationships.Using Xinfeng C-band polarimetric radar observations ZDRand ZHH,the raindrop Gamma size distribution parametersμ,Λ,and N0were retrieved.A scheme for using C-band polarimetric radar to retrieve the DSDs was developed.This research revealed that during precipitation process,the DSDs obtained using the C-band polarimetric radar retrieval scheme are similar to the 2DVD observations,the precipitation characteristics of rainfall intensity(R),mass-weighted mean diameter(Dm)and intercept parameter(Nw)with time obtained by radar retrieval are basically consistent with the observational results of the 2DVD.This scheme establishes the relationship between the observations of the C-band polarimetric radar and the physical quantities of the numerical model.This method not only can test the prediction of the model data assimilation system on the convective scale and determine error sources,but also can improve the microphysical precipitation processes analysis and radar quantitative precipitation estimation.The present research will facilitate radar data assimilation in the future.

Cross-sectional rainfall observation on the central-western Tibetan Plateau in the warm season:System design and preliminary results

The central and western Tibetan Plateau(CWTP)is characterized by harsh environment and strong interactions among the spheres of earth as well as significant changes in climate and water cycles over the past four decades.The lack of precipitation observations is a bottleneck for the study of land surface processes in this region.Over the past six years,we have designed and established two observation transects across the south-north and the west-east in this region to obtain hourly rainfall data during the warm season(May-September).The south-north transect extends from Yadong Valley on the southern slope of the Himalayas to Shuanghu County in the hinterland of the plateau,with a total of 31stations;the west-east transect extends from Shiquanhe in the west to Naqu in the central TP,with a total of 22 stations.The observation dataset has been applied to clarify the spatiotemporal characteristics of precipitation in the CWTP,to evaluate the quality of typical gridded precipitation products,to support the development of regional climate models,and to reveal the processes of summertime lake-air interactions.The observation dataset has been released in the National Tibetan Plateau Data Center.

Characterization of( Nb,Ti,Mo) C Precipitates in an Ultrahigh Strength Martensitic Steel

A study on ultrahigh strength steel plate subjected to novel thermo-mechanical control process was presented. The mechanical properties examination showed that the investigated steel exhibited excellent combination of ultra-high strength（ 2 200 MPa） and toughness（ 26 J）. The microstructure of the experimental steel was observed by scanning electron microscope and transmission electron microscope. Desired martensitic lath with width of about 180- 250 nm was obtained. Nanostructured carbide precipitates with sizes of 20-50 nm,which contained Nb,Ti and Mo,were observed in the lath martensitic microstructure,and confirmed to be MC-type carbides with B1 structure by means of selected area electron diffraction.The compositional characteristics revealed by energy dispersive X-ray spectrometer mapping implied that the carbide forming elements Nb,Ti and Mo distributed in the precipitates evenly. Three-dimensional atom probe tomography reconstruction further indicated that Mo incorporated into the precipitates without enrichment in the carbide-matrix interface and probably substituted for Nb and Ti to form the（ Nb,Ti,Mo） C carbides.