Surface water resource attenuation attribution and patterns in Hai River Basin

From 1956 to 2016,Hai River Basin suffered the most severe surface water resource attenuation among the 10 first-class river basins in China.Based on the surface water circulation process,and evolving characteristics of precipitation and underlying surface in Hai River Basin,this study attributed the causes of surface water resource attenuation to six primary impact factors,analyzed each factor's quantitative contribution,and revealed four patterns of surface water resource attenuation in Hai River Basin.The pattern of the dominant factor:comparing the 1980–2000 period with the 1956–1979period,the variation of precipitation is the dominant factor of which contribution is 7 billion m^(3),accounting for 59%of total11.7 billion m^(3);comparing the 2001–2016 period with the 1956–1979 period,the increasing of vegetation cover in mountainous area is the dominant factor of which contribution is 2.78 billion m3,accounting for 51%of total 4.9 billion m^(3).The pattern of spatial distributions:comparing the 2001–2016 period with the 1956–1979 period,mountainous areas were more affected by increasing vegetation cover which for example contributed 42%in Luan River Basin mountainous;the plains were more impacted by farmland ridge interception which for example contributed 51%in Beisi River Basin plains.The pattern of attenuation trend:comparing the 2001–2016 period with the 1980–2000 period,surface water resources in mountainous areas continued to decline,owing to the increasing water consumption of large-scale vegetation restoration,while the influence of the underlying surface changes on surface water resources in plains areas tended to remain stable.The pattern of reversible change:among factors led to surface water resource attenuation,the human activity,including vegetation cover increase,farmland ridge interception,and urbanization expansion,contributed 36%of the attenuation,which resulted in the variation of precipitation-runoff relation.This study improved the traditional attribution classification model of climate change and human activity and analyzed the causes and contributions of water resource attenuation in Hai River Basin based on the water circulation process,which can provide scientific support for the development of water resource management in the basin.

Soot size distribution in lightly sooting premixed flames of benzene and toluene

The evolution of particle size distribution function(PSDF)of soot in premixed flames of benzene and toluene was studied on a burner stabilized stagnation(BSS)flame platform.The cold gas velocities were changed to hold the maximum flame temperatures of different flames approximately constant.The PSDFs of all the test flames exhibited a bimodal distribution,i.e.,a small-size nucleation mode and a large-size accumulation mode.It was observed that soot nucleation and particle growth in the benzene flame were stronger than those in the toluene flame at short residence times.At longer residence times,the PSDFs of the two flames were similar,and the toluene flame showed a larger particle size distribution range and a higher particle volume fraction than the benzene flame.

Spatiotemporal Variability of Surface Wind Speed during 1961-2017 in the Jing-Jin-Ji Region,China

Wind speed variations are influenced by both natural climate and human activities.It is important to understand the spatial and temporal distributions of wind speed and to analyze the cause of its changes.In this study,data from 26 meteorological stations in the Jing-Jin-Ji region of North China from 1961 to 2017 are analyzed by using the Mann-Kendall(MK)test.Over the study period,wind speed first decreased by−0.028 m s^-1 yr^-1(p<0.01)in 1961^-1991,and then increased by 0.002 m s^-1 yr^-1(p<0.05)in 1992-2017.Wind speed was the highest in spring(2.98 m s^-1),followed by winter,summer,and autumn.The largest wind speed changes for 1961-1991 and 1992-2017 occurred in winter(−0.0392 and 0.0065 m s^-1 yr^-1,respectively);these values represented 36%and 58%of the annual wind speed changes.More than 90.4%of the wind speed was concentrated in the range of 1-5 m s^-1,according to the variation in the number of days with wind speed of different grades.Specifically,the decrease in wind speed in 1961^-1991 was due to the decrease in days with wind speed of 3-5 m s^-1,while the increase in wind speed in 1992-2017 was mainly due to the increase in days with wind speed of 2-4 m s^-1.In terms of driving factors,variations in wind speed were closely correlated with temperature and atmospheric pressure,whereas elevation and underlying surface also influenced these changes.

On the Increased Precipitation Recycling by Large-Scale Irrigation over the Haihe Plain

Irrigation not only plays an important role in global food security,but it also affects aspects of the regional climate,including precipitation.In this study,we proposed a simple and convenient method to quantify the contribution of large-scale irrigation to precipitation by distinguishing the amount of evaporation generated by irrigation from local evaporation based on the precipitation recycling method.A case study was presented to show the increased precipitation recycling ratio and the contribution of irrigation to precipitation during the main irrigation period in the Haihe Plain from 1961 to 2016.We found that the average precipitation recycling rates in the Haihe Plain are 8.32%,9.74%,and 10.36%in April,May,and June,respectively.The contribution rates of irrigation to precipitation in the Haihe Plain are 3.76%,5.12%,and 2.29%in April,May,and June,respectively.The total contribution of irrigation to precipitation during the main irrigation period is 3.77 mm;the respective contributions in April,May,and June are 0.72,1.70,and 1.35 mm.The contribution of irrigation to local precipitation is relatively small as the inflow of atmospheric moisture during the irrigation period is still the main factor affecting local precipitation.Nevertheless,this part of the precipitation during the irrigation period alleviates the water shortage in the Haihe Plain to some extent.