Policy Research Center for Environment and Economy

ABSTRACT This study investigates how water pricing subsidy mechanisms affect the adoption of watersaving technologies in agriculture, with a focus on China. Using a dynamic decision‐making model based on Markov chains, we examine farmers' intertemporal choices under varying policy configurations. The analysis accounts for regional disparities in agricultural conditions and pricing structures. The results indicate that water pricing policies, when coupled with explicit subsidies, substantially increase the adoption of water‐saving technologies, especially in regions with severe water scarcity or high infrastructure costs. Both ex ante and ex post subsidies are found to be effective; however, ex ante subsidies yield greater adoption rates in areas with high upfront investment requirements. The findings underscore the importance of subsidy design in shaping long‐term adoption behaviour, highlighting the need for tailored pricing and subsidy policies to optimize water conservation outcomes. Policy recommendations are proposed to refine the pricing mechanism and subsidy structures, aiming to balance short‐term financial incentives with long‐term water conservation benefits.

Abstract This study investigates the atmospheric circulation anomalies and dynamic mechanisms driving drought–flood abrupt alternation (DFAA) events during the preflood season from 1979 to 2021 over South China (SC). Our results demonstrate that vertical dynamic effects are the primary drivers of these events, with distinct physical mechanisms across different stages. In drought-to-flood (DTF) events, enhanced negative (positive) zonal vorticity advection from the lower- to midtroposphere, caused by anticyclonic (cyclonic) circulation anomalies over SC during drought (flood) stages, plays a pivotal role in switching between anomalous descending and ascending motions. In contrast, in flood-to-drought (FTD) events, ascending motions during flood stages are primarily induced by zonal warm advection from the interaction between lower-level anticyclonic anomalies over the northern South China Sea and cyclonic anomalies over SC. During drought stages of the FTD events, descending motions are sustained by multiple factors: reduced positive meridional vorticity advection from the lower- to midtroposphere, upper-tropospheric cold advection by anomalous easterly winds, and lower-tropospheric cold advection linked to anomalous zonal temperature gradients—all associated with barotropic anticyclonic anomalies over SC. These insights enhance our understanding of the complex dynamics underlying DFAA events during the preflood season over SC, thereby offering potential opportunities for improved predictions of extreme drought and flood occurrences during this season. Significance Statement This study reveals the dynamic driving mechanisms of drought–flood abrupt alternation (DFAA) events during the preflood season over South China (SC), emphasizing the critical role of vertical dynamic effects. Drought-to-flood (DTF) events are primarily controlled by zonal vorticity advection, characterized by rapid transitions from anticyclonic to cyclonic conditions in the lower–midtroposphere, resulting in shifts in vertical motion. However, flood-to-drought (FTD) events are governed by warm and cold temperature advection, arising from changes between southwest moisture transport and barotropic anticyclonic dominance. These processes drive transitions between ascending and descending motions, leading to precipitation extremes. By elucidating these mechanisms, this study advances the understanding of preflood season dynamics and provides valuable insights for improving drought and flood prediction and management in SC.

Based on the Spatial Durbin Model (SDM), this study evaluates the spatial spillover effect of PM2.5 concentration in Beijing–Tianjin–Hebei (BTH) and its surrounding areas from 2000 to 2016, analyzes its main influencing factors and verifies the Environmental Kuznets Curve (EKC). In addition, Social Network Analysis (SNA) is used to measure the regional air pollution transmission network. The results are as follows: (1) A significant inverted U-shaped EKC with spatial spillover effect between the sampled 48 cities was verified. (2) Industrial structure had both local and spillover effects on air pollution with a U-shaped curve; technological progress exerted a negative spillover effect on air pollution, while traffic evidenced positive local and spillover effects; meteorological conditions showed different impacts on air pollution. (3) Heze, Tianjin, Xingtai, Shijiazhuang and Liaocheng are the top five cities in the centrality of the air pollution correlation network, indicating air pollution in these cities have significant impacts on other cities within the network; while Sanmenxia, Weihai, Yuncheng, Langfang and Zhumadian are the bottom five cities, which indicates that the air pollution of these cities has the least correlation with other cities. The policy suggestions for 48 cities involve: building up a regional joint prevention and control mechanism, enhancing the supervision of cities located in the centrality of the air pollution correlation network, accelerating high-tech and service-oriented industrialization, encouraging technological innovation in energy conservation and environmental protection and implementing vehicle regulation.

In this study, future change of El Nino-related East Asian (EA) rainfall and the diversity of this relationship are investigated on the basis of the historical and representative concentration pathway 8.5 (RCP 8.5) simulations taken from the Coupled Model Intercomparison Project phase 5 (CMIP5). By evaluating the East Asian Summer Monsoon (EASM) climatology and interannual variations in simulations contributing to CMIP5, nine models are verified to be capable of reproducing El Nino diversity and EASM simultaneously. Six of these models are selected for projecting the multi-model ensemble (MME) mean of two types of El Nino-related EA/western North Pacific (WNP) rainfall patterns and low-level atmospheric circulations under global warming, considering the realism in their simulated El Nino and EASM phenomena. It was found that, under a warmer background climate, the general patterns of anomalous circulation and rainfall will persist, but with amplification of the rainfall intensity during mature boreal winter and decaying summer for both Eastern-Pacific (EP) and Central-Pacific (CP) El Nino. Amplification of CP type-related rainfall seems to be stronger than that for EP type El Nino. Further analyses show that a moister atmosphere tends to always strengthen the rainfall variations for both El Nino flavors, regardless of how the El Nino-related circulation amplitude is modulated in various seasons. However, in boreal summer during the El Nino decaying phase, strengthened anomalous circulation also enhances the rainfall variability, with an effect comparable to the background moisture increase. Some of these atmospheric circulation changes might be associated with modified sea surface temperature anomalies (SSTA) of El Nino and its diversity, under global warming. Our results indicate the importance of better preparedness and higher resilience in the EA region to enhanced El Nino-induced hydrological variations under a warming climate.

Grazing by livestock greatly affects the soil carbon (C) cycle in grassland ecosystems. However, the effects of grazing at different intensities and durations on the dynamics of soil C in its subsoil layers are not clearly understood. Here, we compiled data from 78 sites (in total 122 published studies) to examine the effects of varying grazing intensities and durations on soil C content at different depths for grasslands in China. Our meta-analysis revealed that grazing led to an overall decrease in soil C content and productivity of above-ground vegetation (e.g., above-ground biomass and litter) but an increase in below-ground biomass. Specifically, the effects of grazing on soil C content became less negative or even positive with increasing soil depths. An increase of soil C content was consequently found under light grazing (LG), although soil C content still decreased under moderate and heavy grazing. The increase in soil C content under LG could be largely attributed to the increase of soil C content in subsoil layers (>20cm), despite that soil C content in surface soil layer (0-20cm) decreased. Moreover, the magnitude of increase in soil C content under LG in subsoil layers increased with grazing duration. A possible reason of the increase in soil C content in the subsoil layers was due to the increases in below-ground biomass. Our study highlights that LG may modify the allocation of C input and promote its accumulation in subsoil layers, thus offsetting the negative impact of grazing on surface soil C content, a finding that has significant implications for C sequestration in grasslands.