Land–atmosphere–ocean coupling associated with the Tibetan Plateau and its climate impacts

Weak monsoon signals detected in growth chronologies of lake fish on the Qinghai-Tibetan Plateau

Understanding the variation in fish growth responses to climate change across regions is essential for predicting fish population dynamics and relevant ecological consequences on a large scale. Despite the demonstrated sensitivity of fish growth responses to climate change on the Qinghai-Tibetan Plateau (QTP), the geographical variations in these responses remain unclear. This study analyzed the growth responses of schizothoracine fish to environmental variables in four geographically distinct QTP lakes (Qinghai Lake, Yamdrok Lake, Pangong Tso, and Co Nag) using otolith biochronologies and hierarchical mixed-effects modeling and quantified the relative contributions of intrinsic and extrinsic factors to fish growth variations. Overall, we found that the optimal model accounted for 82% of the annual growth variability. Age variables were the intrinsic factors primarily influencing fish growth (significant and negative, accounting for 92% of the explained variability), followed by the influence of extrinsic environmental factors at the local (i.e., air temperature and precipitation, significant and positive, 5%), global (i.e., sea surface temperature [SST], significant and negative, 2%), and regional (i.e., monsoon intensity, nonsignificant and negative, 0.4%) scales. At the lake level, the influences of environmental factors on fish growth aligned with overall results but showed varied contributions. Therefore, local factors primarily influence fish growth responses, emphasizing that geographical variations in fish responses to climate change should be accounted for in relevant population predictions. This study provides valuable insights into the complex interactions between fish growth and multi-scale environmental changes and offers scientific support for ecosystem management under climate change on the QTP.

Tipping point-induced abrupt shifts in East Asian hydroclimate since the Last Glacial Maximum

Multiple tipping points in the Earth system could be triggered when global warming exceeds specific thresholds. However, the degree of their impact on the East Asian hydroclimate remains uncertain due to the lack of quantitative rainfall records. Here we present an ensemble reconstruction of East Asian summer monsoon (EASM) rainfall since the Last Glacial Maximum (LGM) using nine statistical and machine learning methods based on multi-proxy records from a maar lake in southern China. Our results define five tipping points in the EASM rainfall since the LGM, which are characterized by abrupt and irreversible regime shifts with a median amplitude of 387 ± 73 mm (24 ± 5 %). Combined with multi-model simulations and existing records, we attribute these tipping points to cascades of abrupt shifts in the Atlantic meridional overturning circulation (AMOC) and Saharan vegetation. Our findings underscore the nonlinear behavior of the EASM and its coupling with other tipping elements.

Resonance between projected Tibetan Plateau surface darkening and Arctic climate change

The Tibetan Plateau (TP) exerts a profound influence on global climate over million-year timescales due to its past uplift. However, whether the ongoing climate changes over the TP, particularly the persistent reduction in its local albedo (referred to as "TP surface darkening"), can exert global impacts remains elusive. In this study, a state-of-the-art coupled land-atmosphere global climate model has been employed to scrutinize the impact of TP darkening on polar climate changes. Results indicate that the projected TP darkening has the potential to generate a stationary Rossby wave train, thereby modulating the atmospheric circulation in the high-latitudes of the Northern Hemisphere and instigating a dipole-like surface air temperature anomaly pattern around the Arctic region. An additional experiment suggests that the projected Arctic warming may in return warm the TP, thus forming a bi-directional linkage between these two climate systems. Given their association with vast ice reservoirs, the elucidation of this mechanism in our study is crucial in advancing our comprehension of Earth system climate projections.

Regional and tele-connected impacts of the Tibetan Plateau surface darkening

Despite knowledge of the presence of the Tibetan Plateau (TP) in reorganizing large-scale atmospheric circulation, it remains unclear how surface albedo darkening over TP will impact local glaciers and remote Asian monsoon systems. Here, we use a coupled land-atmosphere global climate model and a glacier model to address these questions. Under a high-emission scenario, TP surface albedo darkening will increase local temperature by 0.24 K by the end of this century. This warming will strengthen the elevated heat pump of TP, increasing South Asian monsoon precipitation while exacerbating the current "South Flood-North Drought" pattern over East Asia. The albedo darkening-induced climate change also leads to an accompanying TP glacier volume loss of 6.9%, which further increases to 25.2% at the equilibrium, with a notable loss in western TP. Our findings emphasize the importance of land-surface change responses in projecting future water resource availability, with important implications for water management policies.

Impact of global warming on regional cycling of mercury and persistent organic pollutants on the Tibetan Plateau: current progress and future prospects

Global warming profoundly affects not only mountainous and polar environments, but also the global and regional cycling of pollutants. Mercury (Hg) and persistent organic pollutants (POPs) have global transport capacity and are regulated by the Minamata Convention and Stockholm Convention, respectively. Since the beginning of this century, understanding of the origin and fate of Hg and POPs on the Tibetan Plateau (TP, also known as the third pole) has been deepening. In this paper, the existing literature is reviewed to comprehensively understand the atmospheric transport, atmospheric deposition, cumulative transformation and accumulation of Hg and POPs on the TP region under the background of global warming. The biogeochemical cycle of both Hg and POPs has the following environmental characteristics: (1) the Indian summer monsoon and westerly winds carry Hg and POPs inland to the TP; (2) the cold trapping effect causes Hg and POPs to be deposited on the TP by dry and wet deposition, making glaciers, permafrost, and snow the key sinks of Hg and POPs; (3) Hg and POPs can subsequently be released due to the melting of glaciers and permafrost; (4) bioaccumulation and biomagnification of Hg and POPs have been examined in the aquatic food chain; (5) ice cores and lake cores preserve the impacts of both regional emissions and glacial melting on Hg and POP migration. This implies that comprehensive models will be needed to evaluate the fate and toxicity of Hg and POPs on larger spatial and longer temporal scales to forecast their projected tendencies under diverse climate scenarios. Future policies and regulations should address the disrupted repercussions of inclusive CC such as weather extremes, floods and storms, and soil sustainable desertification on the fate of Hg and POPs. The present findings advocate the strengthening of the cross-national programs aimed at the elimination of Hg and POPs in polar (Arctic, Antarctic and TP) and certain mountainous (the Himalaya, Rocky Mountains, and Alps) ecosystems for better understanding the impacts of global warming on the accumulation of Hg/POPs in cold and remote areas.

Thunderstorm Activity over the Qinghai–Tibet Plateau Indicated by the Combined Data of the FY-2E Geostationary Satellite and WWLLN

Thunderstorm activity over the Qinghai–Tibet Plateau (QTP) has important climatic effects and disaster impacts. Using the thunderstorm feature dataset (TFD) established based on the black body temperature (TBB) and cloud classification (CLC) products of the Fengyun-2E (FY-2E) geostationary satellite, as well as the lightning data of the World Wide Lightning Location Network (WWLLN), the temporal and spatial distributions and some cloud properties of the thunderstorms over the QTP were analyzed. Approximately 93.9% and 82.7% of thunderstorms over the QTP occur from May to September and from 12 to 21 o’clock local time, and the corresponding peaks are in August and at 14:00, respectively. There are three centers featuring frequent thunderstorms in the southeast, south-central, and southwest regions of the QTP. The average thunderstorm cloud area (the region with TBB ≤ −32 °C) is 1.8 × 104 km2. Approximately 32.9% of thunderstorms have strong convective cells (SCCs) composed of areas with TBB ≤ −52 °C. The average number and area ratio of SCCs are 3.6 and 25.4%, respectively, and their spatial distribution is given. The average cloud area and the number and area ratio of SCCs of extreme-lightning thunderstorms (thunderstorms with the top 10% of lightning numbers) are approximately 30.0, 3.9, and 1.5 times those of normal thunderstorms. The spatial distribution of the thunderstorm activity is quite different from that of lightning activity given by the Lightning Imaging Sensor (LIS) and Optical Transient Detector (OTD) over the northeastern and southwestern QTP, which may mean that the convection intensity, cloud structure, and charge structure of the thunderstorms over the QTP are different between different regions and seasons.

Remote Sensing-Detected Changes in Precipitation over the Source Region of Three Rivers in the Recent Two Decades

The source region of three rivers (SRTR) is an important water conservation area, also known as the Water Tower of Asia. Precipitation is one of the most important factors affecting the ecological system and water resources over the SRTR. However, the characteristics and mechanism of its change at different time scales are still uncertain. Using the GSMaP remote sensing products and ERA5 reanalysis data, this study analyzes the spatial and temporal variability of precipitation and water vapor transport in the SRTR over the past two decades. The annual precipitation slightly reduces in the north and west and slightly increases in the east and south parts of the SRTR. The spring, autumn and winter dominate the decrease in precipitation in most areas of the SRTR, while the summer contributes the most increases. In contrast with the 2000s, the afternoon precipitation slightly reduced in the 2010s, while the nighttime precipitation increases significantly. The changes in nighttime precipitation, especially its intensity, associated with the water vapor transport contribute to the changes in precipitation over the SRTR.

Impact of deep basin terrain on PM2.5 distribution and its seasonality over the Sichuan Basin, Southwest China

The terrain effect on atmospheric environment is poorly understood in particular for the polluted region with underlying complex topography. Therefore, this study targeted the Sichuan Basin (SCB), a deep basin with severe PM_2.5 pollution enclosed by the eastern Tibetan Plateau (TP), Yunnan-Guizhou Plateaus (YGP) and mountains over Southwest China, and we investigated the terrain effect on seasonal PM_2.5 distribution and the meteorological mechanism based on the WRF-Chem simulation with stuffing the basin topography. It is characterized that the three-dimensional distribution of topography-induced PM_2.5 concentrations over the SCB with the seasonal shift of regional PM_2.5 averages from approximately 30 μg m^-3 in summer to 90 μg m^-3 in winter at surface layer and from summertime 10 μg m^-3 to wintertime 30 μg m^-3 in the lower free troposphere. Such basin-forced PM_2.5 changes presented the vertically monotonical declines concentrated within the lower troposphere below 3.6 km in spring, 2.3 km in summer, 2.6 km in autumn and 4.8 km in winter. Impacts of deep basin aggravated PM_2.5 accumulation within the SCB and transport toward the surrounding plateaus contributing approximately 50-90% to PM_2.5 levels over the regions of eastern TP and northern YGP. In the SCB, atmospheric thermal structure in the lower troposphere could build a vertical convergence layer between the boundary layer and free troposphere, acting as a lid inhibiting air diffusion, which was regulated by the terrain effects on interactions of westerlies and Asian monsoons, especially the wintertime strong warm lid deteriorating air pollution in the SCB. Furthermore, warm and humid air conditions within the basin prompted sulfur oxidation ratio by +0.02 and nitrogen oxidation ratio by +0.22 effectively producing the secondary PM_2.5 in atmospheric environment.

Convective Entrainment Rate over the Tibetan Plateau and Its Adjacent Regions in the Boreal Summer Using SNPP-VIIRS

The entrainment rate (λ) is difficult to estimate, and its uncertainties cause a significant error in convection parameterization and precipitation simulation, especially over the Tibetan Plateau, where observations are scarce. The λ over the Tibetan Plateau, and its adjacent regions, is estimated for the first time using five-year satellite data and a reanalysis dataset. The λ and cloud base environmental relative humidity (RH) decrease with an increase in terrain height. Quantitatively, the correlation between λ and RH changes from positive at low terrain heights to negative at high terrain heights, and the underlying mechanisms are here interpreted. When the terrain height is below 1 km, large RH decreases the difference in moist static energy (MSE) between the clouds and the environment and increases λ. When the terrain height is above 1 km, the correlation between λ and RH is related to the difference between MSE turning point and cloud base, because of decreases in specific humidity near the surface with increasing terrain height. These results enhance the theoretical understanding of the factors affecting λ and pave the way for improving the parameterization of λ.

Spatio-Temporal Variations of Water Vapor Budget over the Tibetan Plateau in Summer and Its Relationship with the Indo-Pacific Warm Pool

The water vapor budget (WVB) over the Tibetan Plateau (TP) is closely related to the large-scale atmospheric moisture transportation of the surrounding mainland and oceans, especially for the Indo-Pacific warm pool (IPWP). However, the procession linkage between the WVBs over the TP and its inner basins and IPWP has not been sufficiently elucidated. In this study, the relationship between the summer WVB over the TP and the IPWP was quantitatively investigated using reanalysis datasets and satellite-observed sea surface temperature (SST). The results show that: (1) the mean total summer vapor budget (WVBt) over the TP in the period of 1979–2018 was 72.5 × 106 kg s−1. Additionally, for the 13 basins within the TP, the summer WVB has decreased from southeast to northwest; the Yarlung Zangbo River Basin had the highest WVB (33.7%), followed by the Upper Yangtze River Basin, Ganges River Basin and Qiangtang Plateau. (2) For the past several decades, the WVBt over the TP has experienced an increasing trend (3.81 × 106 kg s−1 decade−1), although the southern boundary budget (WVBs) contributed the most and is most closely related with the WVBt, while the eastern boundary budget (WVBe) experienced a decreasing trend (4.21 × 106 kg s−1 decade−1) which was almost equal to the interdecadal variations of the WVBt. (3) For the IPWP, we defined a new warm pool index of surface latent heat flux (WPI-slhf), and found that an increasing WPI-slhf would cause an anticyclone anomaly in the equatorial western Indian Ocean (near 70° E), resulting in the increased advent of water vapor to the TP. (4) On the interdecadal scale, the correlation coefficients of the variation of the summer WVBt over the TP with the WPI-slhf and Indian Ocean Dipole (IOD) signal were 0.86 and 0.85, respectively (significant at the 0.05% level). Therefore, the warming and the increasing slhf of the IPWP would significantly contribute to the increasing WVB of the TP in recent decades.