scholarly journals The trend towards a warmer and wetter climate observed in arid and semi-arid areas of northwest China from 1959 to 2019

2021 ◽  
Author(s):  
Shijun Zheng ◽  
Bing Zhang ◽  
Dailiang Peng ◽  
Le Yu ◽  
Binbin Lin ◽  
...  
Keyword(s):  
Potential Evapotranspiration ◽  
Meteorological Data ◽  
Growing Season ◽  
Northwest China ◽  
Temporal Variations ◽  
Climate Trends ◽  
Average Temperature ◽  
Temperature And Precipitation ◽  
Bare Land ◽  
Spatial Differences

Abstract The observed trend towards a warmer and wetter climate in northwest China is a controversial issue lacking sufficient scientific research. Based on monthly meteorological data from 201 weather stations in northwest China and surrounding regions from 1959 to 2019, we calculated potential evapotranspiration using Penman-Monteith (PM) equation. By analyzing the spatial–temporal variations in temperature and precipitation and by studying changing drought trends, we systematically explored the climate trends in northwest China over the past 60 years. Our findings include: (1) From 1959 to 2019, during the growing season, there was a significant upward trend in temperature across northwest China. The most obvious trend, ranged between 0.4–0.6℃ per decade, was observed in northern Qinghai and northeastern Xinjiang. On a per-month basis, the average temperature increased in all months, with April showing a maximum rate of 0.41℃ per decade. (2) The amount of precipitation in the growing season increased in most regions, especially in western Xinjiang and Qinghai. The areas of reduced precipitation were mainly concentrated in the south of Gansu and Ningxia, the west of Shaanxi and the northeast of Xinjiang. The average precipitation also increased in all months, with June showing a maximum change rate of 1.8mm per decade. (3) There were obvious spatial differences in the climate trends in northwest China with the warming shifting from areas of bare land to grassland and the trend towards increased rainfall shifting from grassland to bare land. These effects were most obvious in Xinjiang’s Tarim Basin. (4) From 1959 to 2019, the degree of drought in northwest China significantly decreased in most areas. The areas where drought decreased and precipitation increased were fairly consistent, which produced a strong spatial correlation between them.

scholarly journals Summer drought in Switzerland 1981‒2020: Events, trends and drivers

2021 ◽  
Author(s):  
Simon C. Scherrer ◽  
Christoph Spirig ◽  
Martin Hirschi ◽  
Felix Maurer ◽  
Sven Kotlarski
Keyword(s):  
Regional Climate Model ◽  
Soil Water ◽  
Climate Model ◽  
Potential Evapotranspiration ◽  
Meteorological Data ◽  
Regional Climate ◽  
Reanalysis Data ◽  
Summer Drought ◽  
Temperature And Precipitation ◽  
Temperature Scaling

<p>The Alpine region has recently experienced several dry summers with negative impacts on the economy, society and ecology. Here, soil water, evapotranspiration and meteorological data from several observational and model-based data sources is used to assess events, trends and drivers of summer drought in Switzerland in the period 1981‒2020. 2003 and 2018 are identified as the driest summers followed by somewhat weaker drought conditions in 2020, 2015 and 2011. We find clear evidence for an increasing summer drying in Switzerland. The observed climatic water balance (-39.2 mm/decade) and 0-1 m soil water from reanalysis (ERA5-Land: -4.7 mm/decade; ERA5: -7.2 mm/decade) show a clear tendency towards summer drying with decreasing trends in most months. Increasing evapotranspiration (potential evapotranspiration: +21.0 mm/decade; ERA5-Land actual evapotranspiration: +15.1 mm/decade) is identified as important driver which scales excellently (+4 to +7%/K) with the observed strong warming of about 2°C. An insignificant decrease in precipitation further enhanced the tendency towards drier conditions. Most simulations of the EURO-CORDEX regional climate model ensemble underestimate the changes in summer drying. They underestimate both, the observed recent summer warming and the small decrease in precipitation. The changes in temperature and precipitation are negatively correlated, i.e. simulations with stronger warming tend to show (weak) decreases in precipitation. However, most simulations and the reanalysis overestimate the correlation between temperature and precipitation and the precipitation-temperature scaling on the interannual time scale. Our results emphasize that the analysis of the regional summer drought evolution and its drivers remains challenging especially with regional climate model data but considerable uncertainties also exist in reanalysis data sets.</p>

scholarly journals CLASSIFICAÇÃO CLIMÁTICA PARA OS MUNICÍPIOS DE BOTUCATU E SÃO MANUEL, SP

Irriga ◽  
2009 ◽  
Vol 14 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Antonio Ribeiro da Cunha ◽  
Dinival Martins
Keyword(s):  
Air Temperature ◽  
Potential Evapotranspiration ◽  
Sao Paulo ◽  
São Paulo ◽  
Humid Climate ◽  
Average Temperature ◽  
Temperature And Precipitation ◽  
Hot Climate ◽  
Climatic Classification ◽  
Humidity Index

CLASSIFICAÇÃO CLIMÁTICA PARA OS MUNICÍPIOS DE BOTUCATU E SÃO MANUEL, SP  Antonio Ribeiro da Cunha; Dinival Martins1 Departamento Recursos Naturais - Ciências Ambientais, Faculdade de Ciências Agronômicas, Universidade Estadual Paulista, Botucatu, SP, [email protected]  1 RESUMO A classificação climática procura definir os limites geográficos dos diferentes tipos de clima que ocorrem em todo mundo, sendo considerado um estudo básico para áreas afins. Este trabalho teve como objetivo classificar climaticamente os municípios Botucatu (Fazenda Experimental do Lageado) e de São Manuel (Fazenda Experimental de São Manuel) ambas da Faculdade de Ciências Agronômicas – UNESP, Campus de Botucatu, SP. Para tanto, utilizou-se das metodologias de Köppen e de Thornthwaite em dados normais de temperatura do ar e precipitação pluviométrica no período de 36 anos (1971 a2006). Os municípios de Botucatu e de São Manuel tiveram a mesma classificação climática pelo método de Köppen, como sendo Cfa, clima temperado quente (mesotérmico) úmido, e a temperatura média do mês mais quente é superior a 22 ºC. Pela classificação de Thornthwaite houve uma pequena diferença em função do índice de umidade, caracterizando como B2rB’3a’ (clima úmido com pequena deficiência hídrica - abril, julho e agosto, mesotérmico, com evapotranspiração potencial anual de 945,15 mm e concentração da evapotranspiração potencial no verão igual a 33%) o município de Botucatu, e como B1rB’3a’ (clima úmido com pequena deficiência hídrica - abril, julho e agosto, mesotérmico, com evapotranspiração potencial anual de994,21 mm e concentração da evapotranspiração potencial no verão igual a 33%) o município de São Manuel. UNITERMOS: temperatura do ar, precipitação, evapotranspiração, método de Köppen, método de Thornthwaite.  CUNHA, A. R.; MARTINS, D. CLIMATIC CLASSIFICATION FOR THE DISTRICTS OF BOTUCATU AND SÃO MANUEL, SP  2 ABSTRACT Climatic classification defines the geographical limits of different climate types all over the world, and it is considered essential to study similar areas. This work updates the climatic classification of the municipal districts of Botucatu and of São Manuel, State of Sao Paulo, where the experimental farms of the Schools of Agronomical Sciences - UNESP, Campus of Botucatu, State of São Paulo, are located. Köppen’s and Thornthwaite’s methods were used for the air temperature and precipitation data in a 36-year period (from 1971 to 2006). For both municipal districts of Botucatu and São Manuel, the climate was characterized as being Cfa, hot climate with rains in the summer and drought in the winter, and the average temperature in the hottest month is above 22 ºC. According to Thornthwaite’s classification, there was a small difference due to the humidity index, characterized as B2rB'3a' (humid climate with small hydro deficiency - April, July and August, with annual potential evapotranspiration of 945.15 mm and concentration of the potential evapotranspiration in the summer of 33%) in the district of Botucatu, and as B1rB'3a' (humid climate with small hidric deficiency - April, July and August, with annual potential evapotranspiration of994.21 mm and concentration of the potential evapotranspiration in the summer of 33%)in  the district of São Manuel.  KEY WORDS: air temperature, precipitation, evapotranspiration, Köppen method, Thornthwaite method.

scholarly journals Attribution of growing season evapotranspiration variability considering snowmelt and vegetation changes in the arid alpine basins

2021 ◽  
Vol 25 (6) ◽  
pp. 3455-3469
Author(s):  
Tingting Ning ◽  
Zhi Li ◽  
Qi Feng ◽  
Zongxing Li ◽  
Yanyan Qin
Keyword(s):  
Potential Evapotranspiration ◽  
Water Storage ◽  
Growing Season ◽  
Northwest China ◽  
Qilian Mountains ◽  
Vegetation Changes ◽  
Total Water ◽  
Relative Contribution ◽  
Temporal Variance ◽  
The Qilian Mountains

Abstract. Previous studies have successfully applied variance decomposition frameworks based on the Budyko equations to determine the relative contribution of variability in precipitation, potential evapotranspiration (E0), and total water storage changes (ΔS) to evapotranspiration variance (σET2) on different timescales; however, the effects of snowmelt (Qm) and vegetation (M) changes have not been incorporated into this framework in snow-dependent basins. Taking the arid alpine basins in the Qilian Mountains in northwest China as the study area, we extended the Budyko framework to decompose the growing season σET2 into the temporal variance and covariance of rainfall (R), E0, ΔS,Qm, and M. The results indicate that the incorporation of Qm could improve the performance of the Budyko framework on a monthly scale; σET2 was primarily controlled by the R variance with a mean contribution of 63 %, followed by the coupled R and M (24.3 %) and then the coupled R and E0 (14.1 %). The effects of M variance or Qm variance cannot be ignored because they contribute 4.3 % and 1.8 % of σET2, respectively. By contrast, the interaction of some coupled factors adversely affected σET2, and the out-of-phase seasonality between R and Qm had the largest effect (−7.6 %). Our methodology and these findings are helpful for quantitatively assessing and understanding hydrological responses to climate and vegetation changes in snow-dependent regions on a finer timescale.

scholarly journals Water table fluctuation and its effects on vegetation in a semiarid environment

2011 ◽  
Vol 8 (2) ◽  
pp. 3271-3304 ◽  
Author(s):  
L. Duan ◽  
T. Liu ◽  
X. Wang ◽  
Y. Luo ◽  
W. Wang ◽  
...  
Keyword(s):  
Water Table ◽  
Vegetation Index ◽  
Potential Evapotranspiration ◽  
Meteorological Data ◽  
Depth Map ◽  
Northern China ◽  
Temporal Variations ◽  
Water Table Fluctuation ◽  
Semiarid Environment ◽  
Spatio Temporal

Abstract. A good understanding of water table fluctuation effects on vegetation is crucial for sustaining fragile hydrology and ecology of semiarid areas such as the Horqin Sandy Land (HSL) in northern China, but such understanding is not well documented in literature. The objectives of this study were to examine spatio-temporal variations of water table and their effects on vegetation in a semiarid environment. A 9.71 km2 area within the HSL was chosen and well-instrumented to continuously measure hydrometeorologic parameters (e.g., water table). The area comprises of meadow lands and sandy dunes as well as transitional zones in between. In addition to those measured data, this study also used Landsat TM and MODIS imageries and meteorological data at a station near the study area. The spatio-temporal variations were examined using visual plots and contour maps, while the effects on vegetation were determined by overlaying a water table depth map with a vegetation index map derived from the MODIS imageries. The results indicated that water table was mainly dependent on local topography, localized geological settings, and human activities (e.g., reclamation). At annual and monthly scales, water table was mainly a function of precipitation and potential evapotranspiration. A region within the study area where depth to water table was smaller tended to have better (i.e., more dense and productive) vegetation cover. Further, the results revealed that water table fluctuation was more sensitive for vegetations in the meadow lands than in the transitional zones, but it was least sensitive for vegetations in the sandy dunes.

scholarly journals Attribution of growing season evapotranspiration variability considering snowmelt and vegetation changes in the arid alpine basins

2020 ◽  
Author(s):  
Tingting Ning ◽  
Zhi Li ◽  
Qi Feng ◽  
Zongxing Li ◽  
Yanyan Qin
Keyword(s):  
Potential Evapotranspiration ◽  
Water Storage ◽  
Growing Season ◽  
Northwest China ◽  
Qilian Mountains ◽  
Vegetation Changes ◽  
Total Water ◽  
Relative Contribution ◽  
Temporal Variance ◽  
The Qilian Mountains

Abstract. Previous studies have successfully applied variance decomposition frameworks based on the Budyko equations to determine the relative contribution of variability in precipitation, potential evapotranspiration (E0), and total water storage changes (∆S) to evapotranspiration variance (σ2ET) on different time-scales; however, the effects of snowmelt (Qm) and vegetation (M) changes have not been incorporated into this framework in snow-dependent basins. Taking the arid alpine basins in the Qilian Mountains in northwest China as the study area, we extended the Budyko framework to decompose the growing season σ2ET into the temporal variance and covariance of rainfall (R), E0, ∆S, Qm, and M. The results indicate that the incorporation of Qm could improve the performance of the Budyko framework on a monthly scale; σ2ET was primarily controlled by the R variance with a mean contribution of 63 %, followed by the coupled R and M (24.3 %) and then the coupled R and E0 (14.1 %). The effects of M variance or Qm variance cannot be ignored because they contribute to 4.3 % and 1.8 % of σ2ET, respectively. By contrast, the interaction of some coupled factors adversely affected σ2ET, and the out-of-phase seasonality between R and Qm had the largest effect (−7.6 %). Our methodology and these findings are helpful for quantitatively assessing and understanding hydrological responses to climate and vegetation changes in snow-dependent regions on a finer time-scale.

scholarly journals Characterizing Meteorological Scenarios Favorable for Septoria tritici Infections in Wheat and Estimation of Latent Periods

Plant Disease ◽  
2007 ◽  
Vol 91 (11) ◽  
pp. 1445-1449 ◽  
Author(s):  
Matthias Henze ◽  
Marco Beyer ◽  
Holger Klink ◽  
Joseph-Alexander Verreet
Keyword(s):  
Latent Period ◽  
Meteorological Data ◽  
Natural Infection ◽  
Hierarchical Cluster ◽  
Septoria Tritici ◽  
Leaf Wetness ◽  
Infection Period ◽  
Average Temperature ◽  
Temperature And Precipitation ◽  
Coefficients Of Variation

Septoria tritici epidemics were monitored on winter wheat cv. Ritmo between 1995 and 2003 at 8 to 11 locations per year in Northern Germany (area between 53.70 and 54.38°N latitude and 8.83 and 10.88°E longitude) by counting the number of pycnidia on the leaves of plants obtained from plots under natural infection. Furthermore, meteorological data (leaf wetness, temperature, and precipitation) were recorded within the same period at the same locations. Groups of similar meteorological events were identified by hierarchical cluster analysis. The temporal distance of those clusters from the point of time when an increase of more than 70 S. tritici pycnidia was observed per leaf within 1 week was calculated for all epidemiological case studies and meteorological clusters. A cluster with average temperature = 13.62 ± 2.30°C, leaf wetness = 92.39 ± 4.15%, and precipitation = 0.04 ± 0.10 mm per day was consistently observed at 20.35 ± 4.15 days before epidemic outbreaks. This estimate of a latent period was significantly affected by geographic latitude, average temperature during infection, average temperature during the latent period, year, and precipitation, but not by leaf layer and longitude. On average, an increase in temperature during the infection period by 1°C decreased latent periods by 0.95 day. Latent periods were decreased by 0.2 day upon an increase of the average temperature by 1°C during the latent period. Average latent periods decreased by 1.7 days per degree of north latitude. Latent period estimates had lower coefficients of variation than temperature sums accumulated over latent periods. The usefulness of the approach described above for general epidemiology and for increasing fungicide efficacy by improving the timing of applications is discussed.

scholarly journals Irrigation Influencing Farmers’ Perceptions of Temperature and Precipitation: A Comparative Study of Two Regions of the Tibetan Plateau

2020 ◽  
Vol 12 (19) ◽  
pp. 8164
Author(s):  
Tao Wang ◽  
Jianzhong Yan ◽  
Xian Cheng ◽  
Yi Yu
Keyword(s):  
Climate Change ◽  
Tibetan Plateau ◽  
Yellow River ◽  
Meteorological Data ◽  
Warming Trend ◽  
Vulnerable Groups ◽  
The Tibetan Plateau ◽  
Climate Trends ◽  
Temperature And Precipitation ◽  
The Government

Farmers are among the most vulnerable groups that need to adapt to climate change. Correct perception is a prerequisite for farmers to adopt adaptation strategies, which plays a crucial guiding role in the development of adaptation plans and the improvement of the security of livelihoods. This study aimed to compare farmers’ perceptions of temperature and precipitation change with meteorological data in two regions of the Tibetan Plateau, analyzed how irrigation affects farmers’ perceptions. Data were obtained from local meteorological stations and household questionnaires (N = 1005). The study found that, since 1987, the climate warming trend was significant (p < 0.01), and the temperature increase was faster in winter. Precipitation had no significant change trend, but the seasonal variations indicated that the precipitation concentration period moved forward in the Pumqu River Basin and was delayed a month in the Yellow River-Huangshui River valley. The farmers’ perception of temperature change was consistent with meteorological data, but there was an obvious difference in precipitation perception between the two regions. We noticed that irrigation facilities played a mediating role on precipitation perception and farmers having access to irrigation facilities were more likely to perceive increased precipitation. Finally, this study suggested that meteorological data and farmers’ perceptions should be integrated when developing policies, rather than just considering actual climate trends. Simultaneously, while strengthening irrigation investment, the government should also pay attention to publicizing the consequences of climate change and improving farmers’ abilities of risk perception.

Temporal–spatial distributions of water use and productivity of maize in China

2018 ◽  
Vol 156 (4) ◽  
pp. 528-536 ◽  
Author(s):  
X. C. Cao ◽  
R. Shu ◽  
D. Chen ◽  
X. P. Guo ◽  
W. G. Wang
Keyword(s):  
Water Use ◽  
Yellow River ◽  
Northwest China ◽  
Green Water ◽  
Least Squares Regression ◽  
Maize Production ◽  
Agricultural Water Management ◽  
Average Temperature ◽  
Temperature And Precipitation ◽  
Plsr Model

AbstractThe present study aim to explore temporal–spatial patterns of water use (WU) efficiency and its influencing factors of maize production in China during 1998–2010. WU and productivity (WP) were quantified by taking irrigation loss into account and the links between WP and nine selected indicators were revealed by the partial least squares regression (PLSR) model. Results showed that national WU and WP in maize production were 138.56 cubic gigametres (Gm3; 0.755 green and 0.245 blue) and 1.079 kg/m3, respectively. WP was enhanced in the present study due to an increase in irrigated crop yield. Provinces located in the middle–lower part of the Yellow River had high proportions of green water and WP, while high proportions of irrigation water and low WP were found in Northwest China. The dosage of pesticides per unit area, relative humidity, average temperature and precipitation were the dominant factors that affected WP. However, the relationships between WP and solar radiation, fertilizer, agricultural machinery power, irrigation proportion and irrigated efficiency were not significant. Findings of the present research may also provide a reference for regional agricultural water management.

scholarly journals Vegetation Phenology in the Qilian Mountains and Its Response to Temperature from 1982 to 2014

2021 ◽  
Vol 13 (2) ◽  
pp. 286
Author(s):  
Cancan Qiao ◽  
Shi Shen ◽  
Changxiu Cheng ◽  
Junxu Wu ◽  
Duo Jia ◽  
...  
Keyword(s):  
Climate Change ◽  
Regional Scale ◽  
Growing Season ◽  
Qilian Mountains ◽  
Annual Average ◽  
Temperature And Precipitation ◽  
Spatial And Temporal Heterogeneity ◽  
Spatial Differences ◽  
The Qilian Mountains ◽  
Response To Temperature

The vulnerability of vegetation ecosystems and hydrological systems in high-altitude areas makes their phenology more sensitive and their response to climate change more intense. The Qilian Mountains, an important geographic unit located in the northeastern Tibetan Plateau (TP), has experienced the more significant increases in temperature and precipitation in the past few decades than most areas of the TP. However, under such intense climate change, the temporal and spatial differences in phenology in the Qilian Mountains are not clear. This study explored the spatial and temporal heterogeneity of phenology in the Qilian Mountains from 1982 to 2014 and its response to three temperature indicators, including the mean daily temperature (Tmean), mean daily daytime temperature (Tmax), and mean daily nighttime temperature (Tmin). The results showed that (1) as the altitude rose from southeast to northwest, the multiyear mean of the start of the growing season (SOS) was gradually delayed mainly from 120 to 190 days, the multiyear mean of the end of the growing season (EOS) as a whole was advanced (from 290 to 260 days), and the multiyear mean of the length of the growing season (LGS) was gradually shortened (from 150 to 80 days). (2) In general, there was an advanced trend in the annual average SOS (0.2 days per decade), a delayed trend in the annual average EOS (0.15 days per decade), and an extended trend in the annual average LGS (0.36 days per decade) over the study period. However, there has been no significant phenological trend in recent years, especially for the SOS after 2000 and the EOS and LGS after 2003. (3) Higher preseason temperatures led to an advanced SOS and a delayed EOS at the regional scale. Moreover, the SOS and EOS were more triggered by Tmax than Tmin and Tmean. The LGS was significantly positively correlated with annual mean temperature (r = −0.82, p < 0.01).

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