Robust drying and wetting trends found in regions over China based on Köppen climate classifications

Chen, Tiexi; Zhang, Huixian; Xing, Chen; Hagan, Daniel Fiifi Tawia; Wang, Guojie; Gao, Zhiqiu; Shi, Tingting

doi:10.1002/2016jd026168

Cited by 49 publications

(43 citation statements)

References 56 publications

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“…Over China, these hotspots were found over regions that were partly wet and partly dry. China is characterized by several climate zones based on the Koppen Geiger climate classifications [21]. This makes it a very suitable regional test bed to fairly assess the performance of these model products without the added noise of the global scale.…”

Section: Introductionmentioning

confidence: 99%

An Evaluation of Soil Moisture Anomalies from Global Model-Based Datasets over the People’s Republic of China

Hagan

Parinussa

Wang

et al. 2019

Water

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Soil moisture is an important factor in land-atmosphere interactions and other land processes. Improved estimates from climate models have, in the last two decades, become an important alternate source of information. In this study, we extend the evaluation of soil moisture anomalies of different generations of three families of model datasets (the European Center for Medium-Range Weather Forecasts’ (ECMWF) reanalysis, the Modern Era Retrospective Analysis for Research and Applications of NASA, and the Global Land Data Assimilation System of theNational Oceanic and Atmospheric Administration (NOAA)) in recent studies to the People’s Republic of China. Two validation techniques, namely, root-mean-square error (RMSE) from triple collocation analysis (TCA) and correlations (R) with ground observations, were used. The study confirmed the results of previous studies that focused on other regions and showed that the newer generations of each modeling family generally had better skill than the older generations with higher correlations and lower RMSEs. A cross-validation of the results from the two techniques for the newer products showed that the higher correlations and lower RMSEs from the TCA were found over regions with moderate vegetation cover, while regions with less vegetation cover had lower correlations and larger RMSEs (ECMWF (R: −0.93), NASA (R: −0.73), and NOAA (R: −0.61)), indicating that these two techniques complement each other to fairly validate the products.

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Section: Introductionmentioning

confidence: 99%

An Evaluation of Soil Moisture Anomalies from Global Model-Based Datasets over the People’s Republic of China

Hagan

Parinussa

Wang

et al. 2019

Water

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“…In this study, the drying and wetting trends of the drylands of China and its three sub-regions, i.e., semi-arid, east arid and west arid areas, were investigated by means of nine dryness indicators, including two precipitation indicators as CMA_P and CRU_P, and seven statistical and physical drought indices as SPEI_01, SPEI_06, SPEI-12, PDSI and sc_PDSI, as well as two soil moisture indicators, i.e., root zone soil moisture (Root_sm) and surface soil moisture (Surf_sm), during 1982-2012. These dryness indicators were selected based on Chen's hypothesis that robust conclusions can be obtained by using multiple and sophisticated indices at the regional scales [14]. On the whole, the drylands show a pattern of wetting in the west and drying in the east.…”

Section: Discussionmentioning

confidence: 99%

Drying and Wetting Trends and Vegetation Covariations in the Drylands of China

Liang

Chen

Dolman

et al. 2020

Water

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The semi-arid and arid drylands of China, which are located in the inland region of Eurasia, have experienced rapid climate change. Some regions in particular, have shown upward trends in the observational records of precipitation. However, there is more to drying and wetting than just changes in precipitation which still have large uncertainties. Coherent results, however, can be obtained, at the regional scale, with the use of multiple indices as shown in the recent literature. We divided the drylands of China into three sub-regions, i.e., a semi-arid (SA), an eastern-arid (EA) and a western-arid (WA) region. Precipitation from the China Meteorological Administration (CMA) and Climatic Research Unit (CRU), statistical and physical drought indices, including the Standardized Precipitation Evapotranspiration Index (SPEI), the Palmer Drought Severity Index (PDSI), self-calibrating PDSI (sc_PDSI), Root zone soil moisture (Root_sm) and Surface soil moisture (Surf_sm) from Global Land Evaporation Amsterdam Model (GLEAM), and Normalized Difference Vegetation Index (NDVI) were used to identify temporal and spatial patterns in drying and wetting. Data were selected from 1982–2012, in line with the availability of the remotely sensed vegetation data. Results show that the drylands of China exhibits a pattern of wetting in the west and drying in the east. The semi-arid region in the east is becoming drier and the drought area is increasing, with the values of CMA_P, CRU_P, PDSI, sc_PDSI, SPEI-01,SPEI-06, SPEI-12, Root_sm, Surf_sm at −1.064 mm yr−1, −0.834 mm yr−1, −0.050 yr−1 (p < 0.1), −0.174 yr−1 (p < 0.1), −0.014 yr−1, −0.06, −0.021 (p < 0.1), −0.257×10−3 m3 m−3 yr−1, −0.024×10−3 m3 m−3 yr−1, respectively. The arid region generally exhibits a wetting trend, while the area in drought declines only in the western arid region, but not in the eastern arid part. In the semi-arid region, growing season (May to September) NDVI is significantly correlated (p < 0.1) with eight out of nine indicators. We show in this study that the semi-arid region needs more study to protect the vegetation ecosystem and the water resources.

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“…Other studies investigate wet and dry hydrological extremes using indices such as the PDSI (Briffa et al, 2009;Chen et al, 2017;Dai et al, 2004;Kangas and Brown, 2007;Palmer, 1965;Wang et al, 2014), SPI (Bordi et al, 2009;Domínguez-Castro et al, 2018;García-Valdecasas Ojeda et al, 2017;Kangas and Brown, 2007;Martin, 2018;McKee T.B., Doesken N.J., 1995;McKee et al, 1993;Sun et al, 2016;Tošić and Unkašević, 2014; or Standardized Precipitation Evapotranspiration Index (SPEI) (Chen et al, 2017;Domínguez-Castro et al, 2018;García-Valdecasas Ojeda et al, 2017;Sun et al, 2016;Vicente-Serrano et al, 2010;.…”

Section: Hydrological Extremes and Modes Of Climate Variability 241mentioning

confidence: 99%

“…The PDSI and SPEI were also used to quantify wet and dry trends in six regions over China, differentiated by Köppen climate zones (Chen et al, 2017;Rubel and Kottek, 2010). They found that for both wet and dry trends these indices agree in five out of six regions and the increasing dryness occurred in the humid and arid transition region of China.…”

Section: Hydrological Extremes and Modes Of Climate Variability 241mentioning

confidence: 99%

Concurrent Hydroclimatic Hazards from Catchment to Global Scales

Luca¹

2020

Preprint

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Interactions between multiple hazards can cause socio-economic damages that exceed those expected by the individual hazard components. Over the past decade, the multi-hazards paradigm has emerged to the extent that the Sendai Framework for Disaster Risk Reduction 2015-2030 advocated a multi-hazard approach. This thesis examines three types of concurrent hydroclimatic hazards that can occur at catchment to global scales. The first multi-hazard is the link between multi-basin flooding (MBF) and extra-tropical cyclones (ETCs) over Great Britain during the period 1975-2014. Results show that during the most geographically widespread MBF episode, up to 108 river catchments (or ~46% of the study area) recorded a peak flow annual maximum within a 16-day window. Most extreme MBF episodes were linked to cyclonic Lamb Weather Types (LWTs), atmospheric rivers and very severe gales. These episodes were associated with significant socio-economic impacts due to widespread flooding. The second hazard was observed (1971-2000) and projected (2011-2100) LWTs, whose seasonal frequency and persistence are associated with multi-hazards over the British Isles. Daily sea-level-pressure data from two reanalyses products, one subjective weather pattern catalogue and an ensemble of 10 Atmosphere-Ocean General Circulation Models (AOGCMs) were used to compute LWTs. Results showed that the AOGCMs are overall able to reproduce historical weather pattern persistence, which, along with annual frequency, is projected to significantly increase anticyclonic and decrease cyclonic LWTs, in summer and autumn respectively. This implies a higher risk of drought, heatwaves and air pollution events in summer but reduced likelihood of flooding and severe gales in autumn by the end of the 21st century. By 2100, the AOGCMs suggest an increased risk of concurrent flood-wind hazards during winter. In summer, the strength of the nocturnal Urban Heat Island (UHI) of London is expected to intensify by the end of the century, contributing to higher chances of combined heatwave-air pollution events. The third type of multi-hazard investigated was the spatio-temporal concurrence of global wet and dry hydrological extremes, during the 1950-2014 period. The analysis was conducted using the monthly self-calibrated Palmer Drought Severity Index based on the Penman-Monteith model (sc_PDSI_pm). Results showed that the land area impacted by extreme dry and wet-dry events significantly increased over the observational period. The most geographically widespread wet-dry event covered a total area of 21 million km2 (or 14% of the global land area) with documented flood and drought impacts over diverse regions. Two new metrics were developed to provide more insight into the combined wet and dry hazards: the wet-dry (WD) ratio and the extreme transitions (ET) time interval. The former quantifies the predominance of wet or dry extremes over a given area, whereas the ET measures the average separation time between the opposite extremes (i.e. between wet to dry or dry to wet transitions). The WD-ratio reveals a predominance of wet over dry extremes in the USA, northern and southern south America, northern Europe, north Africa, western China and most of Australia. The ET median for wet to dry is ~27 months, and 21 months for dry to wet. Global correlations between wet-dry hydrological extremes and El Niño Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO) and American Multidecadal Oscillation (AMO) were also investigated. ENSO and PDO showed similar correlation patterns, with the former significantly impacting a larger area. On the other hand, the AMO showed an almost inverse spatial correlation pattern, with an overall larger area impacted. The findings presented in this thesis could be informative for emergency responders and relief agencies, disaster risk reduction practitioners, and (re)insurance companies. For instance, multi-basin flooding co-occurring with ETCs could overwhelm emergency response that depends on support from neighbouring regions that are similarly affected. Economic damages could exceed those insured by households and businesses. Projected rises in nocturnal UHI intensity in London could exacerbate heat-stress and, when combined with episodes of poor air quality, increase the likelihood of health problems amongst vulnerable groups. Furthermore, concurrent wet and dry hydrological extremes could be significant for organizations with global assets or sensitive supply chains, and the hydropower, agricultural and transport sectors. Global maps generated of major wet-dry events and the WD-ratio could also be integrated into a seasonal forecasting product, to help stakeholders in hedging the risk. Key opportunities for further research on multi-hazards are future hydroclimatic projections in the light of anthropogenic climate change and the application of new statistical techniques that could help in discerning the driving physical processes.

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Robust drying and wetting trends found in regions over China based on Köppen climate classifications

Cited by 49 publications

References 56 publications

An Evaluation of Soil Moisture Anomalies from Global Model-Based Datasets over the People’s Republic of China

An Evaluation of Soil Moisture Anomalies from Global Model-Based Datasets over the People’s Republic of China

Drying and Wetting Trends and Vegetation Covariations in the Drylands of China

Concurrent Hydroclimatic Hazards from Catchment to Global Scales

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