Changes In Annual Precipitation Research Articles

Climate Change over the Mediterranean Region: Local Temperature and Precipitation Variations at Five Pilot Sites

The Mediterranean region is one of the most responsive areas to climate change and was identified as a major “hot-spot” based on global climate change analyses. This study provides insight into local climate changes in the Mediterranean region under the scope of the InTheMED project, which is part of the PRIMA programme. Precipitation and temperature were analyzed in an historical period and until the end of this century for five pilot sites, located between the two shores of the Mediterranean region. We used an ensemble of 17 Regional Climate Models, developed in the framework of the EURO-CORDEX initiative, under two Representative Concentration Pathways (RCP4.5 and RCP8.5). Over the historical period, the temperature presents upward trends, which are statistically significant for some sites, while precipitation does not show significant tendencies. These trends will be maintained in the future as predicted by the climate models projections: all models indicate a progressive and robust warming in all study areas and moderate change in total annual precipitation, but some seasonal variations are identified. Future changes in droughts events over the Mediterranean region were studied considering the maximum duration of the heat waves, their peak temperature, and the number of consecutive dry days. All pilot sites are expected to increase the maximum duration of heat waves and their peak temperature. Furthermore, the maximum number of consecutive dry days is expected to increase for most of the study areas.

A framework for drought adaption under deep uncertainties: Application of Portfolio theory (Markowitz 2.0)

Hydrological uncertainty, climate change, and water infrastructure development upstream transboundary basins may affect the safe access to water resources downstream, making socioeconomic and biophysical subsystems vulnerable. Therefore, it is vital to apply decision-making approaches to reduce vulnerability, especially in arid and semi-arid basins. This study evaluated an adaptation framework to reduce vulnerability through optimal water allocation in drought-prone areas. This framework was implemented in an area dependent on upstream transboundary water (Helmand River Basin). An integrated system dynamics model was developed using socioeconomic and biophysical factors identified by the Füssel Vulnerability Framework. The climatic variables of the basin were simulated and predicted by the output of AOGCM models. The trend of upstream annual precipitation and temperature changes during the 2021–2050 period based on the RCP4.5 emission scenario was −2% and +1.9 C compared to those in the historical period, respectively. The results indicated the drought intensification due to a 13% decrease in future runoff (2050) compared to the base period, leading to a reduction in value-added agriculture (8%) and the population (31%). Therefore, the latest version of portfolio optimization called Markowitz 2.0 was used. In order to decide on potential long-term growth versus short-term loss, an efficient frontier was formed between the expected return and the conditional value at risk (CVaR) based on the Markowitz 2.0 model. According to the model results, the development of the industrial sector as an approach with moderate (reasonable) risk could increase financial return by 43% and allocation to the environmental sector by 2.3 times. Finally, prioritizing the environmental sector was a high-risk approach with high returns that increased efficiency by 45%. The results showed that the proposed framework could help decision-makers, based on their risk-taking level, activate and develop decisions on water resource allocation and water-dependent productive sectors on the basis of efficient frontiers.

Subsurface irrigation with ceramic emitters: Evaluating soil water effects under multiple precipitation scenarios

China's Loess Plateau is the optimal and largest region of growing apple trees in the world. Subsurface irrigation with ceramic emitters (SICE) is an energy-efficient and water-saving approach for fruit trees in arid and semi-arid regions. Climate change, which is shifting annual precipitation regimes, is challenging the existing irrigation scheduling. However, little is known about how annual precipitation change affect the irrigation scheduling with SICE. Therefore, simulations with HYDRUS-2D and validation experiments in apple orchard were used to study the effects of the event- and annual-scale precipitation and ceramic hydraulic conductivity of emitter (CHC) on soil water dynamics. Results indicated that annul precipitation slightly affected the irrigation volume, however precipitation events had a significant effect on emitter discharge; the outflow was 22.7% and 49.7% lower in soil than in air with CHC of 0.017 and 0.077 m d−1. There was a significant positive correlation among CHC, irrigation volume and deep percolation. Precipitation and CHC both have a significant effect on the soil water content in apple orchards, the average SWCs of wet year were 17.8%− 24.7% higher than normal and dry year, the average SWC was 0.154 and 0.191 cm3 cm−3 with emitter hydraulic conductivities of 0.017 and 0.077 m d−1, respectively, in 2010. SICE could provide a stable soil water environment for apple trees in different precipitation years. Apple trees could be continuously irrigated by SICE until July, and irrigation could be stopped when the average SWC exceeds 0.20 cm3 cm−3 after July in Loess Plateau. This work may assist orchard managers in adapting their orchards by SICE to meet apple growth under future climate change conditions.

Separating anthropogenic and climate contributions to streamflow variations in Rietspruit sub-basin, South Africa

Human activities and climate change continue to alter streamflow in many river basins. In this study, the influence of human activities and climate variability on streamflow changes in the Rietspruit sub-basin (RSB), South Africa, were investigated using precipitation, potential evapotranspiration, and discharge data for the period 1986 to 2018. Trends in the hydrometeorological variables were assessed using the Mann-Kendall test while the change point in the annual streamflow data was identified using the Pettitt test and the double mass curve technique. Results revealed no statistically significant change in annual precipitation, whereas annual streamflow showed a significant increasing trend while potential evapotranspiration showed a decreasing trend. It was identified that the change point occurred around 1999, thereby dividing the streamflow data into the pre-change (1986–1999) period with comparatively low urban cover (8.3%), and the post-change period (2000–2018) with urban land covering 16.6% of the study area. The results demonstrate that from 1986 to 2018, the elasticity of streamflow with respect to precipitation and potential evapotranspiration was 0.26 and −2.01, respectively. This implies that streamflow in the study area is more sensitive to potential evapotranspiration than precipitation. Nonetheless, changes in land use/land cover, particularly the urban settlement which increased by 101% between 1986 and 2018, were more influential than climate variability for the significant increase in streamflow in the RSB. The results provide necessary information for water resource management, land use planning and ecosystem development in the near future. This study emphasizes the necessity of addressing nonlinear and dynamic hydrological processes as a result of human impact and climate associated changes.

Multiscale variability of China’s historical flood/drought index and precipitation teleconnections with ENSO using wavelet analyses

Studies of the low-frequency variabilities of key climate variables are often handicapped by the limited length of available instrumental observations. To tackle this, the use of a set of historical flood/drought index (FDI) spanning from AD 1470 to 2000 for 120 sites in China has been made to investigate the multiscale temporal variability of annual precipitation by applying wavelet methods. The analyses reveal oscillating components of the FDI time series from the decadal to multi-decadal, and to the quasi-centennial range, as well as in the interannual range. Furthermore, the relationships of the FDI with the dominant mode of oscillations in the coupled ocean–atmosphere system, i.e., the El Niño-Southern Oscillation (ENSO) index, on a range of time scales have been probed by cross wavelet transform and wavelet coherence methods. Statistically significant coherence between FDI and ENSO index time series has been found for regions in eastern China south of the Yangtze River (inclusive) at the decadal to multi-decadal time scale (10- to 50-yr) after 1750, as well as for north China on the 10- to 30-year range in the eighteenth century. The FDI is less coherent with the ENSO index for other regions of China. The results of the present study may add to our understanding of the connections between long-term changes of annual precipitation and large-scale oscillations in the coupled ocean–atmosphere system, and provide a scientific basis for developing policies to adapt to future changes in water abundance.

Holocene climate background for lake evolution in the Badain Jaran Desert of northwestern China revealed by proxies from calcareous root tubes

AbstractIt has been unclear whether Holocene lake evolution in the Badain Jaran Desert of northwestern China, an area in which lakes are mainly recharged by groundwater, responded to climate change. In this study, we analyzed the Mg/Ca ratio and phytolith assemblages from 10 Holocene calcareous root tube samples from the desert to reconstruct changes in effective moisture and mean annual precipitation (MAP) at the millennial scale during the Holocene and to explore the factors affecting lake evolution. Our results revealed that the effective moisture at 7000–5000 cal yr BP was higher than that of 5000–2000 cal yr BP. Similarly, the MAP was higher at 7000–5000 cal yr BP (175 ± 37 to 205 ± 37 mm) than at 5000–2000 cal yr BP (145 ± 37 to 165 ± 39 mm). The expansion of the lakes during the Early Holocene would have resulted from the input of groundwater from the meltwater in the recharge area. High lake levels in the Middle Holocene corresponded to increased monsoonal precipitation and groundwater recharge. The gradual decline of lake levels in the Late Holocene indicated a relatively arid climate with decreased monsoonal precipitation and groundwater recharge.

Temporal and spatial variations of annual precipitation and meteorological drought in China during 1951-2018

Exploring the temporal and spatial variations of precipitation and drought is an important topic in hydro-logy. Based on the precipitation data of 619 meteorological stations in China from 1951 to 2018, we used anomaly percentage method and Morlet wavelet analysis to analyze the temporal and spatial variations of annual precipitation and drought. The results showed that annual precipitation in China showed a stepwise decreasing trend from southeast to northwest during the study period, and that the intensity of annual precipitation change was on the contrary. The precipitation near the boundary of the second and third steps showed a downward trend, and the abrupt change of precipitation occurred mainly in the 1960s and 1970s. The rest region was on the rise, with substantial changes in the 1990s. The main period of precipitation was short in the regions with temperate continental climate and temperate monsoon climate. From 1960s to 2010s, the area of arid land in China had decreased, while that of the semi-arid area and semi-humid area had increased gradually, especially in the recent decade. An aridity boundary was found between 30° N and 40° N, with drought frequency in its north being much more than the south. On the whole, the frequency and scope of drought events showed a decreasing trend and its interdecadal shift direction was from the central part of northwest China to the southern part of North China and then to the northern part of North China.

Interactive Effects on Habitat Quality Using InVEST and GeoDetector Models in Wenzhou, China

Global urbanisation has accelerated in recent years, especially in rapidly growing coastal cities, and the destruction of habitat and natural resources has intensified. Although much attention has been paid to the study of habitat quality, there are still gaps in our understanding of the factors that influence it and their interactions. In this study, the InVEST habitat quality evaluation model and the GeoDetector model were used to construct a framework for analysing the dynamic changes in habitat quality and their influencing factors from 1992 to 2015. Wenzhou City, Zhejiang Province, China, was selected as the study area. The new framework extends studies on habitat quality change to annual analysis and reduces the lag between the actual change and the mapping time. The interactions between natural and anthropogenic factors are explored, and the effects of different types of land use conversion on habitat quality are further discussed. The results show that: (1) During the study period, cultivated and construction land areas in Wenzhou City increased the most, and forest land area decreased the most. (2) Habitat quality in Wenzhou City was generally good during the study period, but it showed a declining trend from year to year, and the distribution of habitat quality decreased from west to east. (3) The interactions between land use change and annual precipitation change and those between land use change and population density change have the most significant impact on habitat quality. The conversion of forest land to cultivated land, conversion of water area to cultivated land, and conversion of forest land to building land have the greatest impact on habitat quality. The results of the study can provide recommendations for ecological restoration, optimal integration of protected areas, and provide a reference for the healthy and sustainable development of coastal regions.

Projections of surface air temperature and precipitation in the 21st century in the Qilian Mountains, Northwest China, using REMO in the CORDEX

Qilian Mountains (QM) is an important ecological security barrier in China and has been significantly affected by climate change, it is therefore of great importance and necessity to project its future climate change using high-resolution climate models because of mountainous areas in the QM and relatively few targeted simulation analyses. In this study, we used the simulations of the regional climate model REMO with 25 km spatial resolution, driven by three different global climate models (MPI-ESM-MR, NorESM1-M, and HadGEM2-ES), to evaluate how annual and seasonal mean surface air temperature and precipitation in the QM are likely to change for three future periods (2011–2040, 2041–2070, and 2071–2100) under two representative concentration pathways (RCP2.6 and RCP8.5). The REMO model, shows noticeable cold and wet biases compared to observations for the reference period (1971–2000) and air temperature simulation outperforms precipitation simulation. The REMO simulations exhibit a warm and wet centre around lake, indicating that the simulation are likely influenced by lake. Projections under RCP2.6 show regional warming reaching 1.74 °C during 2011–2100, characterized by an initial increase and a decrease afterwards. Under RCP8.5, air temperatures increase monotonously from 2011 to 2100, with a warming magnitude of 5.36 °C for 2071–2100 relative to 1971–2000. The overall change in regional-average annual precipitation is not evident during 2011–2100, with some increases or decreases in certain time periods. In the 2071–2100 both the strongest warming and precipitation increase are projected to occur in winter under both scenarios, while precipitation in summer and autumn is projected to decrease in the east of the QM for the three future periods. The results suggest that the QM is likely to experience drought conditions in warm seasons in the future, which could impact agricultural and livestock production.

Discrepancies in changes in precipitation characteristics over the contiguous United States based on six daily gridded precipitation datasets

Variability and spatiotemporal changes in precipitation characteristics can have profound socioenvironmental impacts. Several studies have shown that the frequency and/or magnitude of precipitation events have changed over the contiguous United States (CONUS) in the past decades. Most previous studies used only one precipitation dataset and only investigated mean or extreme precipitation. Here, using 6 gridded daily precipitation datasets, we show that there are substantial discrepancies in the changes in characteristics of both extreme and non-extreme precipitation events from 1983 to 2017. Our results highlight that using a single record to study precipitation changes can potentially lead to biased results. Using different datasets enables examining the overall agreements and discrepancies in precipitation characteristics. For example, we show that almost all datasets agree that some areas show statistically significant changes in the annual precipitation maxima; however, the locations and signs of changes are not consistent across datasets. There is a relative agreement between datasets on changes in the total annual precipitation. When examining other percentiles of the precipitation distribution, including non-extreme values, however, we find widespread discrepancies among different precipitation products (e.g., what part of the precipitation distribution is changing). In fact, depending on the source of data, there exist opposing trends and patterns of change in precipitation characteristics. This highlights the need to further investigate non-extreme precipitation events to unravel potential non-extreme but “unexpected” or “unusual” patterns. Finally, we argue that protocols for data selection are needed to address the issue of inter-data variability and to ensure reliability of statistical analysis.

Water Limitation in Forest Soils Regulates the Increase in Weathering Rates under Climate Change

Climate change is generally expected to have a positive effect on weathering rates, due to the strong temperature dependence of the weathering process. Important feedback mechanisms such as changes in soil moisture, tree growth and organic matter decomposition can affect the response of weathering rates to climate change. In this study, the dynamic forest ecosystem model ForSAFE, with mechanistic descriptions of tree growth, organic matter decomposition, weathering, hydrology and ion exchange processes, is used to investigate the effects of future climate scenarios on base cation weathering rates. In total, 544 productive coniferous forest sites from the Swedish National Forest Inventory are modelled, and differences in weathering responses to changes in climate from two Global Climate Models are investigated. The study shows that weathering rates at the simulated sites are likely to increase, but not to the extent predicted by a direct response to elevated air temperatures. Besides the result that increases in soil temperatures are less evident than those in air temperature, the study shows that soil moisture availability has a strong potential to limit the expected response to increased temperature. While changes in annual precipitation may not indicate further risk for more severe water deficits, seasonal differences show a clear difference between winters and summers. Taking into account the seasonal variation, the study shows that reduced soil water availability in the summer seasons will strongly limit the expected gain in weathering associated with higher temperatures.

Precipitation and soil pH drive the soil microbial spatial patterns in the Robinia pseudoacacia forests at the regional scale

Soil microbial spatial variation across forest types would obscure the huge impact of tree species on microbial community structure and function, and the underlying mechanisms of spatial pattern in the same tree forests was poorly described. We investigated the spatial variation and drivers of microbial communities in the topsoil (0–20 cm) of Robinia pseudoacacia forests at the regional scale on the Loess Plateau. Soil bacterial and fungal communities showed a significant distance decay pattern, and fungi exhibited a more apparent spatial pattern than bacteria. Microbial diversity (Shannon-Wiener and Chao1 indexes) and the relative abundance of Actinobacteria, Gemmatimonadetes, Nitrospirae, Latescibacteria, Verrucomicrobia, Rozellomycota significantly differed among regions. Community dissimilarities of bacterial and fungal indicator species were sensitive to changes in mean annual temperature (MAT) and mean annual precipitation (MAP), respectively. However, the first axis of nonmetric multidimensional scaling (nMDS1) of soil bacterial and fungal communities were respectively associated with soil pH and MAP. The proportion of positive links of co-occurrence networks between microorganisms increased with the decrease in MAP, suggesting that the decrease in precipitation increases species coexistence. Soil bacterial and fungal community assemblies were both dominated by stochastic processes and were well predicted by the neutral community model. The effects of soil properties were larger on bacteria than fungi, and soil properties respectively explained 54.54% and 37.29% of the total variation in the bacterial and fungal community compositions. The major drivers of community dissimilarity varied between bacteria and fungi, indicating that bacterial community was mainly drove by soil pH, NH4+ and geographic distance and fungal community was mainly drove by MAP, pH and geographic distance. Our observations suggested that soil bacterial and fungal communities exhibited distance decay pattern in the Robinia pseudoacacia forests at the regional scale, and this pattern was primarily driven by soil pH and MAP.

Spatial and temporal variations in fractional vegetation cover and its driving factors in the Hulun Lake region

Climate change and human activities are critical to fractional vegetation cover (FVC). However, until now, their combined effects on FVC have not been well quantified. In this paper we analyze the temporal and spatial variations in the fractional vegetation cover in the Hulun Lake region from 1986 to 2017 and its response to changes in climate parameters and human activities; additionally, the impact of changes in climate parameters and human activities on FVC are discussed. The results showed that according to the Mann-Kendall (M−K) trend test analysis, 65.01% of the FVC in the Hulun Lake region decreased to varying degrees, of which 24.55% showed a significant decrease and only 8.61% increased significantly. Based on the M−K mutation test analysis of FVC and analysis of driving factors from 1986 to 2017, 1999 was the time point at which abrupt changes in FVC, annual precipitation and moisture index occurred in the Hulun Lake region, and water was an important factor affecting FVC. The regression analysis of FVC and the driving factors from 1986 to 2017 showed that the moisture index and the number of livestock could not be eliminated from the regression equation. Additionally, there was a significant correlation between the FVC and the climate livestock index (P < 0.001). Linear regression model constructed by FVC and climatic livestock index: y = 23.016ln(x)-31.454 (R2 = 0.5941), FVC increased with the increase of climatic livestock index.

Assessing Changes in 21st Century Mean and Extreme Climate of the Sacramento–San Joaquin Delta in California

This work aims to assess potential changes in the mean and extreme precipitation and temperature across the Sacramento–San Joaquin Delta (Delta) in California in the 21st century. The study employs operative climate model projections from the Coupled Model Inter-comparison Project Phase 5 (CMIP5). Specifically, 64 individual downscaled daily projections (1/16 degree, approximately 6 by 6 km) on precipitation and temperature from 32 Global Circulation Models (GCMs) under two emission scenarios (RCP 4.5 and RCP 8.5) from 2020–2099 are utilized for the analysis. The results indicate increasing warming (in mean, minimum, and maximum temperature) further into the future under both emission scenarios. Warming also exhibits a strong seasonality, with winters expecting lower and summers expecting higher increases in temperature. In contrast, for mean annual total precipitation, there is no consistent wetter or drier signal. On average, the changes in annual total precipitation are minimal. However, dry season precipitation is projected to decline. The study also shows that the number of wet days is projected to decrease while the number of very wet (daily precipitation over 10 mm) and extremely wet (daily precipitation over 20 mm) days is projected to increase. Moreover, the study illustrates that only about half of the changes in total annual precipitation are projected to come from changes in the wettest 10% of wet days. In contrast, a majority of changes in variance of the annual precipitation comes from changes in variance of the wettest 10% of the wet days. This suggests that fluctuations in large storms are projected to dictate the variability of precipitation in the Delta. Additionally, a general upward trend in dry conditions measured by the Standardized Precipitation-Evapotranspiration Index is expected during the projection period. The trending signal is stronger at multi-year temporal scales (one to four years) and under the higher emission scenario. These change patterns are generally similar across three sub-regions of the Delta (i.e., North, South, and West), even though some changes in the South Delta are the most pronounced. This study further discusses challenges posed by these changes to the Delta’s water supply and ecosystems, along with the Delta’s resiliency and potential ways to address these challenges.

Climate change, macroeconomic sensitivity and the response of remittances to the North African countries: a panel VAR analyse

ABSTRACT This article aims to empirically analyse the role of remittances in alleviating the real GDP oscillations induced by the meteorological variability detected by the average annual changes in precipitation and temperature in the North African countries between 1980 and 2016. We use a vector autoregressive model on panel data (PVAR) in order to allow endogenous interactions between the model variables and to circumvent the problem of a small series size by combining the spatial and temporal dimensions. Our results aim to show on the one hand the negative impact of interannual meteorological variability on real GDP per capita. A slight decrease in the latter but it remains statistically significant by 0.2% and 0.13% during the shocks of precipitation and temperature respectively. This is mainly due to the stability of the climate in the region during the last decades. On the other hand, remittances make a contribution of around 3.7% to fluctuations in GDP. These remittances can be used as a cushion on the macroeconomic stability of countries adversely affected by weather conditions. They are characterized by contracyclical patterns which increase adaptability and resistance to hazards. Therefore, the future policies need to be more rigorously focused on adaptation policies and investing in green technologies that mitigate the negative consequences of annual weather and long-term climate change. These measures will contribute to the achievement of Sustainable Development Goals (SDGs).

Palaeoenvironmental reconstruction for the Permian (lower Gondwana) succession of the Godavari Valley Coalfield in southern India based on a combined palynofacies, carbon isotope, and biomarker study

The study presents integrated palynofacies, organic carbon isotope, and biomarker data to reconstruct palaeoenviromental setting for the Permian sediments (borehole MGK-6) of the Kachinapalli block of the Godavari Valley Coalfield, southern India. The palynofacies data reveal three distinct palynofacies (A–C) as follows. Palynofacies A is dominated by abundant arborescent vegetation (glossopterids and conifers) along with structured organic matter, suggesting freshwater forest swamps in proximal settings. Palynofacies B is dominated by abundant degraded organic matter and amorphous organic matter, suggesting lakeshore/flooded palaeomires in slightly dismal settings. It has a high water level in the hinterland, which enables bacterial degradation of organic matter and establishes low-oxygenation conditions within the water column. These conditions would have provided grounds for the accumulation of either degraded or amorphous organic matter. Palynofacies C is dominated by the abundance of charcoal/opaque phytoclasts, indicating prolonged transportation or post-depositional alteration, suggesting a highly-oxidizing condition in distal settings. The bulk organic δ13C range (−25.1‰ to −20.9‰) in the borehole MGK-6 is in close agreement with the global Permian records. This study also shows a weak but statistically significant correlation with the major forms of palynofacies A and C. The interlinked behaviour of bulk organic δ13C and palynofacies suggests that the changes in palaeobiogeography/palaeodepositional settings were most likely driven by the change in mean annual precipitation. The biomarker study shows the presence of n-alkane from C15 to C31 with unimodal and bimodal distribution patterns, revealing the source materials as vascular plants and microbially-altered organic matter. The combined palynofacies, organic carbon isotope, and biomarker data provide vital clue to salient findings for the development of environmental conditions of Godavari Valley Coalfield during lower Gondwana sedimentation.

Projected shifts in K&amp;ouml;ppen climate zones over China and its national ecological security shelter zones

<p indent="0mm">Based on a set of five regional climate model 21st century climate change simulations, this study assesses future changes in Köppen-Trewartha climate types in China and its five national ecological security shelter zones. The regional climate model, the Abdus Salam International Centre for Theoretical Physics (ICTP) regional climate model RegCM4, is driven by five different global climate models, CSIRO-Mk3-6-0, EC-EARTH, HadGEM2-ES, MPI-ESM-MR and NorESM1-M, at a grid spacing of <sc>25 km</sc> under the representative concentration pathway RCP4.5. These global climate models were selected because of their high horizontal resolution and their good performance in reproducing temperature and precipitation over China. The model configuration used was customized for better performance over China. Bias correction was applied to the simulated temperature and precipitation before calculating the climate types. By the end of the 21st century (2069–2098), the annual mean temperature over China is projected to increase by 2.4°C relatives to the present day (1981–2010) annual mean temperature, with the greatest warming (&gt; <sc>2.8°C)</sc> occurring in the Three Rivers Headwaters region. The annual mean precipitation change shows a general increase in most parts of China, except for a slight decrease (&lt; 7%) in southwestern China. The increase is more pronounced over northwestern China. The distribution of climate types was well reproduced by the simulations. A subtropical humid (Cr) climate mainly covers the regions south of the Yangtze River over eastern China. Southwestern China is dominated by a subtropical winter dry (Cw) climate. The Tibetan Plateau is mostly described as tundra (FT) and arid (type B) climate. Dry arid (BW) and semiarid (BS) climates cover most of the northern regions of 35°N except over northeastern China, where temperate continental (Dc) and subarctic continental (Ec) climates exist. Compared to the present-day climates, a change of 22% in the climate types is projected to occur over the whole Chinese territory by the end of the 21st century. The changes are most significant over the Tibetan Plateau and along the climate transition zone of the Qinling Mountains-Huaihe River over China, with a dominant retreat of FT due to the profound warming and an expansion of BS and Cw being projected for the former, and a replacement of temperature oceanic (Do) by Cw being projected for the latter. Over northeastern China, the main projected change in the climate types is the replacement of Ec by Dc. Tropical wet-dry (Aw) climates will occur over all of Hainan Island. The analysis showed that most changes in climate types are driven by temperature rather than precipitation. For the national shelter zones, climate types will change by 24% over all the areas. Profound changes of ~40% will occur in the shelter zones of the Qinghai-Tibet Plateau and the Sichuan-Yunnan-Loess Plateau, followed by those in the northeastern forest. More specifically, over the Qinghai-Tibet Plateau, the replacement of FT by subarctic oceanic (Eo), BS, Ec, and Dc climates is projected to occur. While FT (62%) and BS (26%) dominate this region currently day, BS (38%) and FT (24%) will account for a greater proportion of the region by the end of the 21st century. The change in climate types on the Sichuan-Yunnan-Loess Plateau is characterized by the expansion of Cw and BS and a loss of FT. Replacement of Ec by Dc is projected in the northeastern forest shelter zone, indicating a major retreat of subarctic coniferous forest there. Greater ecological vulnerability and risks in the future under climate change are expected in the zones. Generally, the changes are in good agreement among the individual simulations, indicating a small uncertainty in the projections.

Remotely sensed assessment of increasing chronic and episodic drought effects on a Costa Rican tropical dry forest

AbstractTropical dry forests (TDFs) have experienced pronounced droughts and increased temperatures for the last century. To assess whether these climatic shifts have influenced dry forest vegetation and ecosystem functioning, we integrated ground observations from a Costa Rican long‐term forest dynamics monitoring plot with remotely sensed measures of forest productivity and canopy functioning from a diverse set of satellite data. Previously reported long‐term climate data (1921–1997) show a reduction in annual rainfall, but since 1980 there has been no directional change in mean annual precipitation. However, the 2015 El Niño Southern Oscillation (ENSO)‐induced drought was unprecedented. Temperatures have increased by 1.1°C since 1931. However, the Landsat wet season (1987–2017) Enhanced Vegetation Index (EVI) (canopy greenness) and the dry season (1985–2017) fraction of non‐photosynthetic canopy cover all indicate that TDFs have become more deciduous but also more productive during the wet season. These changes are consistent with a shift in the functional composition observed in the long‐term plot as more drought‐deciduous tree species have increased in abundance. Nonetheless, more continuous 16‐d MODIS (the Moderate Resolution Imaging Spectroradiometer) measures of the EVI over the past 17 yr (2001–2017) showed no change in the total annual forest productivity. Further, while the 2015 ENSO event temporarily reduced forest EVI, it did not cause a longer‐term impact on forest productivity. Instead, high spatial resolution Worldview‐2 satellite imagery showed that forest phenology shifted in the subsequent years even though the region returned to normal precipitation. Our results indicate that while the species composition of TDFs may be sensitive to the long‐term trend of gradually increasing temperatures and aridity, the annual forest functioning has so far been resilient to long‐term drying and a large episodic extreme drought event. This study demonstrates the feasibility of synthesizing satellite images of different characteristics to study the vegetation dynamics of a long‐term forest dynamics plot. Our synoptically sensed results show that the longer‐term changing climate has been and is currently shifting the ecological functioning, and also provide a baseline to assess the impacts of an extreme drought year on TDFs.

Geochemical characteristics of Holocene loess-paleosol sequences in central Chinese Loess Plateau and their implications for East Asian monsoon evolution

The geochemical composition and magnetic susceptibility (MS) of three sections (Weinan, Jingchuan and Jingbian) in the central Chinese Loess Plateau, located along a north-south climate gradient, were analyzed at high resolution in order to reconstruct changes in weathering intensity and hence Asian monsoon evolution during the Holocene. The results show distinct differences in element composition between the loess and paleosol layer, as well as spatial differences which reflect changes in mean annual temperature and annual precipitation along the climatic gradient. The measured major element compositions, combined with the results of previous research, indicate that the provenance of the Holocene loess-paleosol sequences in the central Chinese Loess Plateau was constant over time and space. The degree of chemical weathering in the study area is relatively weak and at an intermediate weathering stage. Based on a magnetic susceptibility age model, the East Asian summer monsoon changes recorded by the loess-paleosol sequences show a distinct two-stage pattern of evolution, with a gradual increase during 13.1–8.5 ka and a gradual decrease thereafter. Comparison of the results with climate records from elsewhere indicates that the East Asian monsoon evolution was mainly controlled by changes in Northern Hemisphere summer insolation and ice sheets.

Uncertainties and their interaction in flood hazard assessment with climate change

Abstract. The assessment of future impacts of climate change is associated with a cascade of uncertainty linked to the modelling chain employed in assessing local-scale changes. Understanding and quantifying this cascade is essential for developing effective adaptation actions. We evaluate and quantify uncertainties in future flood quantiles associated with climate change for four catchments, incorporating within our modelling chain uncertainties associated with 12 global climate models contained in the Coupled Model Intercomparison Project Phase 6, five different bias correction approaches, hydrological model parameter uncertainty and the use of three different extreme value distributions for flood frequency analysis. Results indicate increased flood hazard in all catchments for different Shared Socioeconomic Pathways (SSPs), with changes in flooding consistent with changes in annual maximum precipitation. We use additive chains and analysis of variance (ANOVA) to quantify and decompose uncertainties and their interactions in estimating selected flood quantiles for each catchment. We find that not only do the contributions of different sources of uncertainty vary by catchment, but that the dominant sources of uncertainty can be very different on a catchment-by-catchment basis. While uncertainties in future projections are widely assumed to be dominated by the ensemble of climate models used, we find that in one of our catchments uncertainties associated with bias correction methods dominate, while in another the uncertainty associated with the use of different extreme value distributions outweighs the uncertainty associated with the ensemble of climate models. These findings highlight the inability to generalise a priori about the importance of different components of the cascade of uncertainty in future flood hazard at the catchment scale. Moreover, we find that the interaction of components of the modelling chain employed are substantial (&gt; 20 % of overall uncertainty in two catchments). While our sample is small, there is evidence that the dominant components of the cascade of uncertainty may be linked to catchment characteristics and rainfall–runoff processes. Future work that seeks to further explore the characteristics of the uncertainty cascade as they relate to catchment characteristics may provide insight into a priori identifying the key components of modelling chains to be targeted in climate change impact assessments.