Land surface vegetation dynamics are strongly affected by drought. Thus, understanding the responses of vegetation to drought can inform measures to increase biome stability. In this study, the ...normalized difference vegetation index (NDVI) and the Palmer drought severity index (PDSI) were utilized to investigate the relationship between vegetation activity and drought across different drought regions and ecological community types from 1982 to 2015. Our results showed that the highest correlation between monthly NDVI and PDSI at different timescales (1–36 months) indicated the degree of drought impact on vegetation. There were diverse responses of vegetation to drought according to the drought features and climatic environment. The northern grassland, cropland, and desert ecosystems were strongly impacted by drought. These vegetation ecosystems had a low sensitivity to drought in southern China. Drought had the strongest impact on grassland in summer, which is the high frequency drought season. The most susceptible ecosystem types to drought were those with homogenous vegetation, especially under long-term drought conditions (such as the Inner Mongolia Plateau dominated by grassland). Under global warming, drought with high-temperature characteristics is expected to become more frequent and severe. Such drought could threaten the survival of plateau grassland, arid plain grassland, and rain-fed cropland, as high temperatures accelerate evaporation, leading to water deficit. However, moist forests showed little threat under normal drought. We suggest that future research should focus on vegetation activity in northern and southwestern China, where the vegetation shows the greatest sensitivity to drought.
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•Low vegetation coverage levels were sensitive to drought.•Vegetation was more sensitive to drought in arid areas than in humid areas.•Drought resistance was associated with vegetation diversity and characteristics.•Climatic factors, human activities, and groundwater impacted vegetation response to drought.•Grassland and desert vegetation types were most vulnerable to drought.
China has increased its vegetation coverage and enhanced its terrestrial carbon sink through ecological restoration since the end of the 20th century. However, the temporal variation in vegetation ...carbon sequestration remains unclear, and the relative effects of climate change and ecological restoration efforts are under debate. By integrating remote sensing and machine learning with a modelling approach, we explored the biological and physical pathways by which both climate change and human activities (e.g., ecological restoration, cropland expansion, and urbanization) have altered Chinese terrestrial ecosystem structures and functions, including vegetation cover, surface heat fluxes, water flux, and vegetation carbon sequestration (defined by gross and net primary production, GPP and NPP). Our study indicated that during 2001–2018, GPP in China increased significantly at a rate of 49.1–53.1 TgC/yr2, and the climatic and anthropogenic contributions to GPP gains were comparable (48%–56% and 44%–52%, respectively). Spatially, afforestation was the dominant mechanism behind forest cover expansions in the farming‐pastoral ecotone in northern China, on the Loess Plateau and in the southwest karst region, whereas climate change promoted vegetation cover in most parts of southeastern China. At the same time, the increasing trend in NPP (22.4–24.9 TgC/yr2) during 2001–2018 was highly attributed to human activities (71%–81%), particularly in southern, eastern, and northeastern China. Both GPP and NPP showed accelerated increases after 2010 because the anthropogenic NPP gains during 2001–2010 were generally offset by the climate‐induced NPP losses in southern China. However, after 2010, the climatic influence reversed, thus highlighting the vegetation carbon sequestration that occurs with ecological restoration.
By incorporating multiple remote sensing data into carbon models, this study calculated vegetation carbon uptake (i.e., gross primary production, GPP and net primary production, NPP) in China during 2001–2018. Moreover, we separated the climatic and anthropogenic impacts on vegetation cover and vegetation carbon uptake changes by using a new method. Finally, we also explored the biological or physiological pathways by which climate change and human activities, mainly the ecological restoration efforts, led to the carbon uptake change and other ecosystem changes in China in recent years.
Tibetan Plateau vortices (TPVs) are important rainfall producers generated over the Tibetan Plateau (TP), which can move off the TP under certain conditions. The TPVs greatly affect both local and ...downstream rainfall, but the characteristics of TPV precipitation are not yet fully understood. Accordingly, the climatic characteristics of TPV precipitation during May–August of 1998–2018 are explored in this work from multiple aspects, based on observational TPV and precipitation data sets. Generally, maximums of precipitation amount are observed over the eastern TP and in Sichuan Basin, and the TPVs contribute more than 40% of the precipitation in certain areas within the TP. For the TPVs located over the TP, the precipitation is distributed zonally with a relatively small intensity; for the TPVs beyond the TP, the associated precipitation is distributed in the southwest–northeast direction with a larger intensity. TPVs tend to be responsible for intense rainfall, that is, heavy and torrential rainfalls, and are suggested to be the major intense rainfall producers at certain stations over and downstream from the TP. Meanwhile, TPV precipitation exhibit distinctive features in separate month, for example, TPV precipitation account for the largest percentage of the total precipitation in June and the smallest in August; more than half, even 75% of the torrential rain days downstream from the TP in Sichuan Basin and the regions around 35°N in central and eastern China in May, and in the regions over the TP and its eastern flank in June, July and August are attributed to TPVs.
Climatic characteristics of the Tibetan Plateau vortex (TPV) precipitation during May–August of 1998–2018 are explored, based on the observational TPV and precipitation data sets, from the aspects of TPV precipitation amount (PA), ratio of TPV precipitation to total precipitation (R‐PA), distribution of TPV precipitation in TPVs‐centred coordinates, number of TPVs‐associated rain days at a specific precipitation intensity level (PDAY), and ratio of PDAY to the total rain days at the corresponding precipitation intensity level (R‐PDAY). Besides, distinctive features of TPV precipitation in different months are revealed in addition to the general characteristics of TPV precipitation. Figure shows locations of TPVs at each time during May–August of 1998–2018. The colour of spot denotes the number of TPVs appearing at the same location, and the shading indicates the topography of TP, where a darker colour corresponds to a higher elevation.
Previous studies have often used the 500 hPa geopotential height to define indices of the western Pacific subtropical high (WPSH). However, some studies reported that global warming caused a ...significant increase in geopotential height, particularly at the middle and lower latitudes, leading artificial results about long-term trend of the WPSH. To avoid the spurious signals resulting from global warming, this study first redefines the area, intensity, westward ridge point and ridge line indices of the WPSH by adopting the stream function
R
of horizontal circulation in the three-pattern decomposition of global atmospheric circulation (3P-DGAC). Subsequently, the climatic characteristics of the WPSH in summer are investigated by applying the new indices based on four reanalysis datasets. The results show that the circulation features of the WPSH could be revealed by the stream function
R
in 3P-DGAC. Moreover, the rain belt over East Asia is located at the northwest periphery of the zero-value isoline of the stream function
R
. We conclude that the climatological average WPSH is contracted and retreated eastward during 1979–2018 relative to 1948–1978. Nevertheless, by analyzing interdecadal changes of the time series of the new indices during 1948–2018, we find that area and intensity indices decrease with time before the end of 1970s and increase slightly with time after the end of 1970s, the western ridge point index moves eastward with time before the end of the 1970s and moves westward slightly with time after the end of 1970s, as well as there is no obvious interdecadal variations in the ridge line index. Because of the evident dynamical meaning, the stream function
R
in 3P-DGAC can be used as an objective indicator to describe the interdecadal variation of the WPSH under global warming.
Based on the hourly precipitation data at 124 stations from 1977 to 2017, the basic climatological characteristics of night rainfall rate, frequency and intensity in Yunnan province are analyzed by ...using the statistical methods such as time and space averaging. The results show that: (1) Night rain accounts for a large proportion of daily precipitation in Yunnan, which can exceed 50% in most areas for all seasons, and has significant regional differences. The annual variation of night rainfall rate has a complex and special three-peak pattern. (2) The annual frequency of night rain in Yunnan is more in the east and west than in the middle, which mainly comes from the contribution of the typical high frequency area of night rain in the east and west of Yunnan in spring and winter. In winter and spring, the high frequency area of night rain in eastern and western Yunnan is affected by the southwesterly wind system, Kunming quasi-stationary front and Yunnan topography. (3) The northern and southern margins of Yu
•A classification model of ALS is developed to perform pattern analysis.•Dynamic mechanism of ALS in China was discussed.•3 Driving forces of ALS are characterized with spatial heterogeneity.
The ...healthy functioning of arable landscape ecosystems depends on their functional structure and productivity. In view of current global climate change and constant population mobility, the global agricultural industry has to address the effects of such factors on the functional structure of arable lands. In our research on these issues, we combined information on land use/cover changes with several other datasets. These include meteorological data from 1 823 national and local meteorological stations, agrometeorological disasters from 430 national monitoring stations, and population surveys covering 9 856 townships. Our findings indicate that the arable landscape system in China shows an overall trend of fragmentation, with the extent of the core arable land decreasing by 10 336.06km2. This trend is affected minimally by climate differences and population changes in traditional agricultural regions. However, in eastern and western China, the trend is affected significantly by the rate of population aging, the population migration rate, and the agricultural labor scale. Urban land expansion plays a key role in changing the arable landscape system. Rapid urbanization in the form of an integral transition from arable land to construction, which is represented by large-scale increase in construction land area, is the core dynamic mechanism of landscape structure change of arable landscape systems in China.
Based on the daily rainfall data of 34 observational stations in Chongqing from 1971 to 2015, the climatological characteristics and changes of rainstorm days, intensity and contribution rate in ...Chongqing in recent 45 years are analyzed by using statistical diagnosis methods such as linear trend analysis, Mann-Kendall test and wavelet analysis. The results show that in the past 45 years, the geographical distribution of annual average rainstorm days in Chongqing shows a decreasing trend from mountain to plain. The maximum appears in the eastern part of Chongqing, and the two centers are located in Kaizhou (5.0 d) and Youyang (3.9 d), respectively. The minimum values appeared in Shizhu, Jiangjin and Qijiang (2.2 d). The variational trend of rainstorm days in Chongqing is not obvious, but it has obvious interannual and interdecadal variation. The annual average and summer rainstorm intensity are increasing in Chongqing. The contribution rate of annual and summer rainstorm in Chongqing increased significantly.
In this paper we study the climate change characteristics of rainstorm and risk assessment of rainstorm rainfall in Jinshan of Shanghai in recent 60 years with the daily rain data at Jinshan ...meteorological station from 1959 to 2016 by the methods of abrupt change test, morlet wavelet and so on. The results are as follows. (1) The rainstorm days had been increasing and rainstorm intensity had been increasing indistinctively in Jinshan in recent 60 years. The mutation of rainstorm days from low to high occurred in 1988. The first date of rainstorm had tended to occur early in the recent 60 years. Jinshan had been into the early occurrence stage of rainstorm since 1990s. The last date of rainstorm had tended to occur lately since the 21st century. (2) The risk probability and disaster intensity were the highest for typhoon rainstorm, followed by low pressure rainstorm. The high risk levels of warm sector rainstorm, stationary front rainstorm, low pressure rainstorm and typhoon rainstorm were 50-75 mm, 50-75 mm, 50-90 mm and 50-100 mm, respectively. The corresponding risk probabilities were 28.4%-100%, 28.9%-100%, 32.3%-100% and 33.6%-100%, respectively.
La isla de calor urbana (ICU) se define como la diferencia térmica entre la ciudad y la zona rural. Este fenómeno debido a su importancia se estudia a nivel global, sin embargo en ciudades andinas es ...limitado su estudio, en donde la geografía condiciona la interpretación de la ICU. En Cuenca la zona urbana está a menor altitud que la zona rural, de tal manera que intensifica el calor urbano. En este sentido, este artículo analiza el calor urbano del cantón Cuenca en períodos extremos definidos como época húmeda y seca entre los años 2015 a 2017 en base de información de la red de estaciones del cantón Cuenca con datos de parámetros climáticos como temperatura, precipitación y humedad relativa. Después se generan mapas de calor con los datos de 10 estaciones urbanas y rurales con rango altitudinal de 2.400 hasta 2.800 m s.n.m. Finalmente se identifica la ICU por períodos y sus diferencias respecto a la estación rural más fría. Los resultados muestran una ICU promedio de 3 ºC en el centro urbano para el período húmedo y seco de 2015 a 2017.
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