scholarly journals Historical trends and variability of temperature extremes in two climate vulnerable regions of Bangladesh

2018 ◽  
Vol 16 (2) ◽  
pp. 283-292
Author(s):  
Khalid Mahmud ◽  
Susmita Saha ◽  
Tanvir Ahmad ◽  
Ummay Saima Satu
Keyword(s):  
Kendall Test ◽  
Daily Maximum ◽  
Temperature Extremes ◽  
Upward Trend ◽  
Historical Trends ◽  
Rate Of Increase ◽  
Hot Days ◽  
Increasing Trend ◽  
Decadal Variations ◽  
Cold Extremes

Research on temperature extremes deserves more importance because it reacts sensitively to climate change. As elsewhere across the world, Bangladesh has already become a victim of temperature extremes. Hence, this study was conducted to assess the trends and variability of 11 temperature-related extreme indices based on daily maximum (TX) and daily minimum (TN) temperature recorded at Rajshahi and Barisal over the period 1976–2015. The indices were calculated on annual basis and their average annual and decadal trends were evaluated by non-parametric Mann-Kendall test and Sen’s slope estimate. Significant (p ≤ 0.01) upward trend was observed in some of the hot extremes, such as SU35: number of days with TX > 35°C and TR25: number of days with TN > 25°C, indicating that the number of days and nights with extreme hot temperature are increasing in both sites. Significant decreasing rate (-0.308 day/year) of SU25: number of days with TX > 25°C and increasing rate (1.00 day/year) of SU35 demonstrate that moderate hot days are converting to extreme hot days at Rajshahi. All cold indices showed significant (p ≤ 0.05) variations at Rajshahi implying that cold extremes are becoming severe in this area. Significant rising trend of diurnal temperature range (DTR) indicated the higher rate of increase in TX than in TN at Rajshahi. The increasing trend of all hot indices at Barisal, close to the coast, reveals more warming in hot extremes. However, no significant trends of cold indices were observed at Barisal. Significant average decadal variations of temperature indices were only observed for hot index TNx: annual maximum TN (0.372 °C/decade) and cold index CD25: number of days with TX < 25°C (4.70 days/decade) at Rajshahi and hot index SU35 (5.650 days/decade) at Barisal. So, the relatively dry western region of the country is vulnerable to both hot and cold extremes, whereas coastal area is susceptible to only hot extremes.J. Bangladesh Agril. Univ. 16(2): 283-292, August 2018

scholarly journals Recent trends in daily temperature extremes over northeastern Spain (1960–2006)

2011 ◽  
Vol 11 (9) ◽  
pp. 2583-2603 ◽  
Author(s):  
A. El Kenawy ◽  
J. I. López-Moreno ◽  
S. M. Vicente-Serrano
Keyword(s):  
Land Use Planning ◽  
Crop Yields ◽  
Extreme Temperature ◽  
Daily Temperature ◽  
Maximum Temperature ◽  
Daily Maximum ◽  
Temperature Extremes ◽  
Growing Season Length ◽  
Cold Extremes

Abstract. Spatial and temporal characteristics of extreme temperature events in northeastern Spain have been investigated. The analysis is based on long-term, high-quality, and homogenous daily maximum and minimum temperature of 128 observatories spanning the period from 1960 to 2006. A total of 21 indices were used to assess changes in both the cold and hot tails of the daily temperature distributions. The presence of trends in temperature extremes was assessed by means of the Mann-Kendall test. However, the autocorrelation function (ACF) and a bootstrap methodology were used to account for the influence of serial correlation and cross-correlation on the trend assessment. In general, the observed changes are more prevalent in hot extremes than in cold extremes. This finding can largely be linked to the increase found in the mean maximum temperature during the last few decades. The results indicate a significant increase in the frequency and intensity of most of the hot temperature extremes. An increase in warm nights (TN90p: 3.3 days decade−1), warm days (TX90p: 2.7 days decade−1), tropical nights (TR20: 0.6 days decade−1) and the annual high maximum temperature (TXx: 0.27 °C decade−1) was detected in the 47-yr period. In contrast, most of the indices related to cold temperature extremes (e.g. cold days (TX10p), cold nights (TN10p), very cold days (TN1p), and frost days (FD0)) demonstrated a decreasing but statistically insignificant trend. Although there is no evidence of a long-term trend in cold extremes, significant interdecadal variations were noted. Almost no significant trends in temperature variability indices (e.g. diurnal temperature range (DTR) and growing season length (GSL)) are detected. Spatially, the coastal areas along the Mediterranean Sea and the Cantabrian Sea experienced stronger warming compared with mainland areas. Given that only few earlier studies analyzed observed changes in temperature extremes at fine spatial resolution across the Iberian Peninsula, the results of this work can improve our understanding of climatology of temperature extremes. Also, these findings can have different hydrological, ecological and agricultural implications (e.g. crop yields, energy consumption, land use planning and water resources management).

scholarly journals Trends in Mediterranean gridded temperature extremes and large-scale circulation influences

2011 ◽  
Vol 11 (8) ◽  
pp. 2199-2214 ◽  
Author(s):  
D. Efthymiadis ◽  
C. M. Goodess ◽  
P. D. Jones
Keyword(s):  
Large Scale ◽  
Eastern Mediterranean ◽  
Temperature Extremes ◽  
Global Trends ◽  
Atmospheric Circulation Patterns ◽  
Circulation Patterns ◽  
Rate Of Increase ◽  
The Mediterranean ◽  
Large Scale Atmospheric Circulation ◽  
Cold Extremes

Abstract. Two recently-available daily gridded datasets are used to investigate trends in Mediterranean temperature extremes since the mid-20th century. The underlying trends are found to be generally consistent with global trends of temperature and their extremes: cold extremes decrease and warm/hot extremes increase. This consistency is better manifested in the western part of the Mediterranean where changes are most pronounced since the mid-1970s. In the eastern part, a cooling is observed, with a near reversal in the last two decades. This inter-basin discrepancy is clearer in winter, while in summer changes are more uniform and the west-east difference is restricted to the rate of increase of warm/hot extremes, which is higher in central and eastern parts of the Mediterranean over recent decades. Linear regression and correlation analysis reveals some influence of major large-scale atmospheric circulation patterns on the occurrence of these extremes – both in terms of trend and interannual variability. These relationships are not, however, able to account for the most striking features of the observations – in particular the intensification of the increasing trend in warm/hot extremes, which is most evident over the last 15–20 yr in the Central and Eastern Mediterranean.

Spatiotemporal Evolution of the Drought and Flood in Northeast China

2014 ◽  
Vol 1010-1012 ◽  
pp. 1075-1083 ◽  
Author(s):  
Ru Huang ◽  
Deng Hua Yan
Keyword(s):  
Northeast China ◽  
Linear Regression Analysis ◽  
Kendall Test ◽  
Monthly Precipitation ◽  
Upward Trend ◽  
Spatiotemporal Evolution ◽  
Drought And Flood ◽  
Increasing Trend ◽  
Change Trend ◽  
Monthly Precipitation Data

In order to reduce the losses of drought and flood disasters, the spatiotemporal characteristics and evolution of drought and flood in Northeast China were analyzed by Z index based on the monthly precipitation data of 111 meteorological stations during 1961-2013.The Mann–Kendall test and linear regression analysis were used to analyze the change trend of drought and flood. The main conclusions are as follows: (1) Affected by the monsoon climate, flood is concentrated in summer extensively and frequently in Northeast China, while drought is concentrated in winter. (2) Drought mainly occurs in January, February, March, November and December concentrated in east and southeast of Northeast China. Flood is found in May to September. Especially The highest frequency of flood is observed in July (up to 84.9%), next is August with 69.8%, and followed by June with 48.7%. (3)7 months in a year (March-June and October-December ) show wetting trend over Northeast China , while 3 months (July-September) are observed drying trends. Significant upward trend of wet conditions occur in March and December; while significant trends towards drier conditions occur in September. (4) Drought areas dominate the Northeast China in January, February, March, November and December with a decreasing trend. Flood areas dominate the Northeast China from May to September. Extensive flood is most likely occurred in July. Flood area in May and June show an increasing trend, while a decreasing trend is from July to September.

scholarly journals Variations of precipitable water vapor from 2012 to 2019 over the Philippines using radiosondes

2021 ◽  
Vol 880 (1) ◽  
pp. 012001
Author(s):  
Y Rivera ◽  
K C Capacete ◽  
S K Rodriguez ◽  
A R David ◽  
E Macalalad
Keyword(s):  
Water Vapor ◽  
Precipitable Water ◽  
Kendall Test ◽  
The Philippines ◽  
Precipitable Water Vapor ◽  
Radiosonde Data ◽  
Upward Trend ◽  
Annual Periodicity ◽  
Increasing Trend ◽  
Moderate Positive Correlation

Abstract Precipitable Water Vapor (PWV) refers to the content of water vapor in the atmosphere which is significant in observing climate changes. The trends and variations of precipitable water vapor in Laoag, Legazpi, Mactan, and Puerto Princesa from 2012-2019, are presented through the use of radiosonde data derived from the database of the Integrated Global Radiosonde Archives (IGRA). These data were analyzed for possible patterns through a time series of its daily, monthly, and annual mean, together with a Lomb-Scargle periodogram, and Mann-Kendall test. The results observed varying trends and variability. Legazpi and Puerto Princesa with a minimum value of 20 mm, observed a gradual downward trend of PWV. Laoag and Mactan detected an upward trend of PWV with a minimum of 10 mm and 20 mm, respectively. It also showed an annual and bi-annual periodicity of PWV. Furthermore, all cities detected an increase of PWV during the wet months of May to September, while the dry months of October to April with slight variations over 8 years. In terms of seasonality, only Laoag observed a slightly different dry season, with January, February, and March experiencing around 5 mm less in monthly PWV variation compared to the other cities. The correlation of surface temperature and relative humidity of PWV observed an overall increasing trend while showing a general moderate positive correlation. This study can be used for future references for meteorologists for upcoming forecasting on the likelihood of different weather phenomena in the Philippines.

scholarly journals Attribution of Recent Trends in Temperature Extremes over China: Role of Changes in Anthropogenic Aerosol Emissions over Asia

2019 ◽  
Vol 32 (21) ◽  
pp. 7539-7560 ◽  
Author(s):  
Wei Chen ◽  
Buwen Dong ◽  
Laura Wilcox ◽  
Feifei Luo ◽  
Nick Dunstone ◽  
...  
Keyword(s):  
Longwave Radiation ◽  
Northern China ◽  
Ocean Model ◽  
Shortwave Radiation ◽  
Temperature Extremes ◽  
Historical Trends ◽  
Anthropogenic Aerosol ◽  
Clear Sky ◽  
Emission Changes ◽  
Cold Extremes

ABSTRACT Observations indicate large changes in temperature extremes over China during the last four decades, exhibiting as significant increases in the amplitude and frequency of hot extremes and decreases in the amplitude and frequency of cold extremes. An ensemble of transient experiments with the fully coupled atmosphere–ocean model HadGEM3-GC2, including both anthropogenic forcing and natural forcing, successfully reproduces the spatial pattern and magnitude of observed historical trends in both hot and cold extremes. The model-simulated trends in temperature extremes primarily come from the positive trends in clear-sky longwave radiation, which is mainly due to the increases in greenhouse gases (GHGs). An ensemble of sensitivity experiments with Asian anthropogenic aerosol (AA) emissions fixed at their 1970s levels tends to overestimate the trends in temperature extremes, indicating that local AA emission changes have moderated the trends in these temperature extremes over China. The recent increases in Asian AA drive cooling trends over China by inducing negative clear-sky shortwave radiation directly through the aerosol–radiation interaction, which partly offsets the strong warming effect by GHG changes. The cooling trends induced by Asian AA changes are weaker over northern China during summer, which is due to the warming effect by the positive shortwave cloud radiative effect through the AA-induced atmosphere–cloud feedback. This accounts for the observed north–south gradients of the historical trends in some temperature extremes over China, highlighting the importance of local Asian AA emission changes on spatial heterogeneity of trends in temperature extremes.

scholarly journals Increase of Extreme Drought over Ethiopia under Climate Warming

2019 ◽  
Vol 2019 ◽  
pp. 1-18 ◽  
Author(s):  
Asaminew Teshome ◽  
Jie Zhang
Keyword(s):  
Heavy Precipitation ◽  
Extreme Drought ◽  
Precipitation Extremes ◽  
Maximum Temperature ◽  
Daily Minimum Temperature ◽  
Daily Maximum ◽  
Temperature Extremes ◽  
Temperature And Precipitation ◽  
Increasing Trend ◽  
Annual Total

Recurrent extreme drought and flood in Ethiopia lead to more economic loss. This study examines change and trends of 21 climate extremes of temperature and precipitation over Ethiopia by using indices from the World Meteorological Organization (WMO) Expert Team on Climate Change Detection and Indices (ETCCDI). The analysis was based on the records of observed meteorological data and the future projected from the CMIP5 model under RCP 4.5 and RCP 8.5 scenarios. The results of the seasonal standardized rainfall anomaly and EOF analysis show a decreasing rainfall in JJAS season and significant variability in the FMAM season. The first mode of EOF in FMAM shows that 49.6% was mostly negative with a high amount of variability. The observed precipitation extreme of annual total precipitation (PRCPTOT), consecutive wet days (CWD), and the number of heavy precipitation days (R10) show a decreasing trend, and consecutive dry days (CDD) shows an increasing trend. Additionally, temperature extremes like tropical nights (TR20) and daily maximum and minimum temperatures show a significantly increasing trend. The projected precipitation extremes of CWD, PRCPTOT, very wet day annual total (R95p), and the number of heavy precipitation days (R10) show a decreasing trend. CDD shows longer periods of dryness and a substantial increase which is conducive to the increase of drought. The projected temperature extremes of the warm spell duration indicator (WSDI), daily maximum temperature (TXx) and daily minimum temperature (TNx), summer days (SU25), and tropical nights (TR20) show an increasing trend, while the diurnal temperature range shows a decreasing trend. The projected changes in temperature and precipitation extremes are likely to have significant negative impacts on various socioeconomic activities over Ethiopia. These results highlight the need for planning and developing effective adaptation strategies for disaster prevention.

scholarly journals Assessment of temporal trend of COVID-19 outbreak in India

2020 ◽  
Author(s):  
Amitesh Gupta ◽  
Biswajeet Pradhan
Keyword(s):  
Abrupt Change ◽  
Temporal Trend ◽  
Transmission Rate ◽  
Fold Increase ◽  
Kendall Test ◽  
High Rate ◽  
Pettitt Test ◽  
Rate Of Increase ◽  
Entire Country ◽  
Increasing Trend

The COVID-19 pandemic has outspread obstreperously in India. Within a period of 95 days, from March 02 to June 04, India surpassed 2 lakh in count of infected cases. Approximately 3 out of each 1000 people in India has been tested till date and 53 per 1000 tests results positively infected. During the first week of March, only 14 out of each 1000 tests were resulting as positively infected and it has been extended at a rate of 71/1000 tests in the first week of June, which may indicate a sign of community spread of this disease. Mann-Kendall test denotes that the count of daily confirmed cases is significantly increasing with estimated Sen’s slope of ~ 76 persons/day in entire country. This trend has escalated from ~ 5 persons/day in March to ~ 249 persons/day in the very first week of June. Among major affected cities, Mumbai and Delhi are noted with extremely high rate of increase. In the 3 out of 5 megacities in India: Delhi, Mumbai, and Chennai, the count of daily transmission have reached beyond of 1200 after the third week of May which indicate that the allowance to the migrants might make an easy-way of coronavirus transmission. Additionally, Pettitt test indicates an abrupt change in increasing trend over entire country on April 17, 2020. The nationwide transmission rate was ~ 22 persons/day before April 17 and afterward it amplified to ~ 174 persons/day. Moreover, all the major affected cities also registered multi-fold increase in transmission rate after the evaluated change point over that city; explicitly, this increment was more than 20 times over Pune, Chennai and Ahmedabad. Therefore, the nationwide imposed lockdown in India might have very less impact on flattening the curve of daily confirmed case.

scholarly journals Vegetation Change and Its Response to Climate Extremes in the Arid Region of Northwest China

2021 ◽  
Vol 13 (7) ◽  
pp. 1230
Author(s):  
Simeng Wang ◽  
Qihang Liu ◽  
Chang Huang
Keyword(s):  
Arid Region ◽  
Vegetation Change ◽  
Vegetation Index ◽  
Pearson Correlation ◽  
Time Lag ◽  
Climate Extremes ◽  
Northwest China ◽  
Precipitation Extremes ◽  
Temperature Extremes ◽  
Increasing Trend

Changes in climate extremes have a profound impact on vegetation growth. In this study, we employed the Moderate Resolution Imaging Spectroradiometer (MODIS) and a recently published climate extremes dataset (HadEX3) to study the temporal and spatial evolution of vegetation cover, and its responses to climate extremes in the arid region of northwest China (ARNC). Mann-Kendall test, Anomaly analysis, Pearson correlation analysis, Time lag cross-correlation method, and Least absolute shrinkage and selection operator logistic regression (Lasso) were conducted to quantitatively analyze the response characteristics between Normalized Difference Vegetation Index (NDVI) and climate extremes from 2000 to 2018. The results showed that: (1) The vegetation in the ARNC had a fluctuating upward trend, with vegetation significantly increasing in Xinjiang Tianshan, Altai Mountain, and Tarim Basin, and decreasing in the central inland desert. (2) Temperature extremes showed an increasing trend, with extremely high-temperature events increasing and extremely low-temperature events decreasing. Precipitation extremes events also exhibited a slightly increasing trend. (3) NDVI was overall positively correlated with the climate extremes indices (CEIs), although both positive and negative correlations spatially coexisted. (4) The responses of NDVI and climate extremes showed time lag effects and spatial differences in the growing period. (5) Precipitation extremes were closely related to NDVI than temperature extremes according to Lasso modeling results. This study provides a reference for understanding vegetation variations and their response to climate extremes in arid regions.

scholarly journals Effects of Cropland Expansion on Temperature Extremes in Western India from 1982 to 2015

Land ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 489
Author(s):  
Jinxiu Liu ◽  
Weihao Shen ◽  
Yaqian He
Keyword(s):  
Land Use ◽  
Heat Flux ◽  
Land Cover ◽  
Minimum Temperature ◽  
Negative Impact ◽  
Maximum Temperature ◽  
Daily Minimum Temperature ◽  
Daily Maximum ◽  
Temperature Extremes ◽  
Western India

India has experienced extensive land cover and land use change (LCLUC). However, there is still limited empirical research regarding the impact of LCLUC on climate extremes in India. Here, we applied statistical methods to assess how cropland expansion has influenced temperature extremes in India from 1982 to 2015 using a new land cover and land use dataset and ECMWF Reanalysis V5 (ERA5) climate data. Our results show that during the last 34 years, croplands in western India increased by ~33.7 percentage points. This cropland expansion shows a significantly negative impact on the maxima of daily maximum temperature (TXx), while its impacts on the maxima of daily minimum temperature and the minima of daily maximum and minimum temperature are limited. It is estimated that if cropland expansion had not taken place in western India over the 1982 to 2015 period, TXx would likely have increased by 0.74 (±0.64) °C. The negative impact of croplands on reducing the TXx extreme is likely due to evaporative cooling from intensified evapotranspiration associated with croplands, resulting in increased latent heat flux and decreased sensible heat flux. This study underscores the important influences of cropland expansion on temperature extremes and can be applicable to other geographic regions experiencing LCLUC.

scholarly journals Observed Trends in Indices of Daily Temperature Extremes in South America 1960–2000

2005 ◽  
Vol 18 (23) ◽  
pp. 5011-5023 ◽  
Author(s):  
L. A. Vincent ◽  
T. C. Peterson ◽  
V. R. Barros ◽  
M. B. Marino ◽  
M. Rusticucci ◽  
...  
Keyword(s):  
Climate Change ◽  
South America ◽  
Climate Extremes ◽  
Daily Temperature ◽  
Maximum Temperature ◽  
Daily Minimum Temperature ◽  
Daily Maximum Temperature ◽  
Daily Maximum ◽  
Temperature Extremes ◽  
Increasing Trends

Abstract A workshop on enhancing climate change indices in South America was held in Maceió, Brazil, in August 2004. Scientists from eight southern countries brought daily climatological data from their region for a meticulous assessment of data quality and homogeneity, and for the preparation of climate change indices that can be used for analyses of changes in climate extremes. This study presents an examination of the trends over 1960–2000 in the indices of daily temperature extremes. The results indicate no consistent changes in the indices based on daily maximum temperature while significant trends were found in the indices based on daily minimum temperature. Significant increasing trends in the percentage of warm nights and decreasing trends in the percentage of cold nights were observed at many stations. It seems that this warming is mostly due to more warm nights and fewer cold nights during the summer (December–February) and fall (March–May). The stations with significant trends appear to be located closer to the west and east coasts of South America.

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