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1

Comparison of different ensemble precipitation forecast system evaluation, integration and hydrological applications

Tang Yehai, Wu Qiang, Soomro Shan-e-hyder, Li Xiang, Sun Yue, Hu Caihong

Acta Geophysica

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2023

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Vol. 71, no. 1

405--421

EN

The examination and integration of numerical forecast products are essential for using and developing numerical forecasts and hydrological forecasts. In this paper, the control forecast products from 2010 to 2014 of four model data (China Meteorological Administration (CMA), the National Centers for Environmental Prediction (NCEP), the European Centre for Medium-Range Weather Forecasts (ECMWF), and the United Kingdom Meteorological Office (UKMO)) from The Interactive Grand Global Ensemble (TIGGE) data center were evaluated comprehensively. On this basis, a study of runoff forecasting based on multi-model (multiple regression (MR), random forest (RF), and convolutional neural network-gradient boosting decision tree (CNN-GBDT)) precipitation integration is carried out. The results show that the CMA model performs the worst, while the other models have their advantages and disadvantages in different evaluation indexes. Compared with the single-index optimal model, CMA model had a higher root-mean-square error (RMSE) of 18.4%, and a lower determination coefficient (R2 ) of 14.7%, respectively. The integration of multiple numerical forecast information is better than that of a single model, and CNN-GBDT method is superior to the multiple regression method and random forest method in improving the precision of rainfall forecast. Compared with the original model, the RMSE decreases by 13.1 ~27.9%, PO decreases to 0.538 at heavy rainfall, and the R2 increases by 4~15.2%, but the degree of improvement decreases gradually with the increase in rainfall order. The method of multi-model ensemble rainfall forecasting based on a machine learning model is feasible and can improve the accuracy of short-term rainfall forecasting. The runoff forecast based on multi-model precipitation integration has been improved, and NSE increases from 0.88 to 0.935, but there is still great uncertainty about food peaks during the food season.

2

Identify runoff generation patterns of check dams and terraces and the efects on runoff: a case study

Chen Youqian, Jian Shengqi, Wu Qiang, Hu Caihong, Soomro Shan-e-hyder

Acta Geophysica

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2022

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Vol. 70, no 2

819--832

EN

Over the past 50 years, China has implemented a series of ecological construction projects in the Loess Plateau that have significantly decreased the runoff and sediment from the Yellow River, and it plays an important role in check dams and terraced fields. In this study, the hydrological characteristics of check dams and terraces are used to distinguish their runoff generation pattern. Combined with different runoff generation patterns, runoff generation models were built, and quantitative analysis was conducted on the runoff reduction situation of check dams and terraced fields. Chenggou River Basin, in the Loess Plateau Zhuli River System's second tributary, was selected as an example for analyzing quantitatively the influence of check dam and terraced fields on the runoff production process. Twenty-nine rainfall-food events from 2013 to 2017 were used to evaluate the effect of the runoff generation model, and the results showed that the built model could well simulate the runoff generation in the basin with many check dams and terraces in which runoff relative error of the model was less than 10%. The effect of check dams and terraces on runoff was studied by setting different scenarios. The results show that the dam system can intercept over 50% of the runoff yield of the basin. Terraced fields can enhance the water storage capacity of the basin and reduce the runoff of the basin, and intercept over 10% of the runoff yield of the basin.

3

Changes in carbon storage of Masson Pine Forests along a latitudinal gradient with different stand structures in Southern China

Wu Qiang, Ma Hengyun, Peng Yuanying, Yan Wende, Pan Deng

Polish Journal of Ecology

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2021

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Vol. 69, nr 3-4

137--155

EN

The spatial patterns of carbon pool in landscape vary greatly with variation of forest structures and climate conditions. In this field study, the carbon storage in overstory, understory, litter layer of plants and soil carbon in forests was investigated in 26-28 year-old Masson pine (Pinus massoniana) pure and mixed forests along a latitudinal gradient (20–30 °N) crossing Hunan and Guangxi provinces of China, during the period of May 2015–August 2017. We found that the total carbon storage in Masson pine forests ranged 88.92–149.41 Mg/ha, of which 54.03% occurred in aboveground compound and 45.97% occurred belowground. The overall total carbon storage distribution was 34.62–68.72 Mg/ha, 3.82–10.19 Mg/ha, 2.37–3.96 Mg/ha, and 6.06–12.08 Mg/ha in stems, branches, leaves, and roots, respectively. The carbon storage in the overstory of forest stands and forest soils significantly decreased with increasing latitude, while the carbon storage in the understory and litter of the forest stands significantly increased as the latitude increased. The overall carbon storage significantly decreases by 8.26 Mg/ha in Masson pine forests as the latitude increased by one degree. The carbon storage increased by 8.43% in Masson pine mixed forests compared to the pure forest stands after the transformation from the pure forest stands into the mixed forest stands ∼ 15 years later. The results of changes in carbon storage in the studied forests with the latitudinal gradient could be attributed to variations in hydrothermal conditions with changing latitudes. The forest structure with different tree species composition was another important factor regulating carbon storage in forest ecosystems at the same latitude. The results provided a scientific basis for better understanding of latitudinal variation and spatial distribution of carbon storage in Masson pine forest stands with optimal forest stand structures in subtropical region of China.

4

Study on separation of fine-particle ilmenite and mechanism using flocculation flotation with sodium oleate and polyacrylamide

Peng Yang, Xiao Junhui, Deng Bing, Wang Zhen, Liu Nengyun, Yang Daoguang, Ding Wei, Chen Tao, Wu Qiang

Physicochemical Problems of Mineral Processing

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2020

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Vol. 56, iss. 1

161--172

EN

In this paper, sodium oleate, polyacrylamide, soluble starch and sodium carboxymethyl cellulose were used as flocculants to study the flocculation and sedimentation behavior of microfine ilmenite. Sedimentation test shows that sodium oleate and polyacrylamide have good flocculation effect on ultrafine ilmenite. The flocculation rate of ilmenite can be further improved by the combination of sodium oleate and polyacrylamide. It was found that both flocculants could generate chemical adsorption with ilmenite surface, and they all react with Fe3+ on ilmenite surface. However, sodium oleate reacts with Fe3+ to form a water-insoluble iron oleate precipitate which coats the surface of the ilmenite and hinders the action of polyacrylamide and the remaining Fe3+. This problem can be avoided by adding polyacrylamide followed by sodium oleate, and the flotation recovery can be increased significantly.