scholarly journals Amplified Risk of Compound Heat Stress-Dry Spells in Urban India

2021 ◽  
Author(s):  
Poulomi Ganguli
Keyword(s):  
Heat Stress ◽  
Surface Wind ◽  
Extreme Temperature ◽  
Joint Probability ◽  
Annual Number ◽  
Dry Spells ◽  
Synoptic Wind ◽  
Dry Spell ◽  
Synoptic Conditions ◽  
Low Precipitation

Abstract Compound warm-dry spells over land, which is expected to occur more frequently and expected to cover a much larger spatial extent in a warming climate, result from the simultaneous or successive occurrence of extreme heatwaves, low precipitation, and synoptic conditions, e.g., low surface wind speeds. While changing patterns of weather and climate extremes cannot be ameliorated, effective mitigation requires an understanding of the multivariate nature of interacting drivers that influence the occurrence frequency and predictability of these extremes. However, risk assessments are often focused on univariate statistics, incorporating either extreme temperature or low precipitation; or at the most bivariate statistics considering concurrence of temperature versus precipitation, without accounting for synoptic conditions influencing their joint dependency. Based on station-based daily meteorological records from 23 urban and peri-urban locations of India, covering the 1970-2018 period, this study identifies four distinct regions that show temporal clustering of the timing of heatwaves. Further, combining joint probability distributions of interacting drivers, this analysis explored compound warm-dry potentials that result from the co-occurrence of warmer temperature, scarcer precipitation, and synoptic wind patterns. The results reveal a 50-year severe heat stress tends to be more frequent and is expected to become 5 to 17-year events at each location. Notably, considering dependence among drivers, a median 6-fold amplification (ranging from 3 to 10-fold) in compound warm-dry spell frequency is apparent relative to the expected annual number of a local 50-year severe heatwave episode, indicating warming-induced desiccation is already underway over most of the urbanized areas of the country.

scholarly journals Wind changes above warm Agulhas Current eddies

Ocean Science ◽  
2016 ◽  
Vol 12 (2) ◽  
pp. 495-506 ◽  
Author(s):  
M. Rouault ◽  
P. Verley ◽  
B. Backeberg
Keyword(s):  
Wind Speed ◽  
Large Scale ◽  
Surface Wind ◽  
Surrounding Water ◽  
Agulhas Current ◽  
Speed Increase ◽  
Wind Speeds ◽  
Warm Core ◽  
Synoptic Wind ◽  
Synoptic Conditions

Abstract. Sea surface temperature (SST) estimated from the Advanced Microwave Scanning Radiometer E onboard the Aqua satellite and altimetry-derived sea level anomalies are used south of the Agulhas Current to identify warm-core mesoscale eddies presenting a distinct SST perturbation greater than to 1 °C to the surrounding ocean. The analysis of twice daily instantaneous charts of equivalent stability-neutral wind speed estimates from the SeaWinds scatterometer onboard the QuikScat satellite collocated with SST for six identified eddies shows stronger wind speed above the warm eddies than the surrounding water in all wind directions, if averaged over the lifespan of the eddies, as was found in previous studies. However, only half of the cases showed higher wind speeds above the eddies at the instantaneous scale; 20 % of cases had incomplete data due to partial global coverage by the scatterometer for one path. For cases where the wind is stronger above warm eddies, there is no relationship between the increase in surface wind speed and the SST perturbation, but we do find a linear relationship between the decrease in wind speed from the centre to the border of the eddy downstream and the SST perturbation. SST perturbations range from 1 to 6 °C for a mean eddy SST of 15.9 °C and mean SST perturbation of 2.65 °C. The diameter of the eddies range from 100 to 250 km. Mean background wind speed is about 12 m s−1 (mostly southwesterly to northwesterly) and ranging mainly from 4 to 16 m s−1. The mean wind increase is about 15 %, which corresponds to 1.8 m s−1. A wind speed increase of 4 to 7 m s−1 above warm eddies is not uncommon. Cases where the wind did not increase above the eddies or did not decrease downstream had higher wind speeds and occurred during a cold front associated with intense cyclonic low-pressure systems, suggesting certain synoptic conditions need to be met to allow for the development of wind speed anomalies over warm-core ocean eddies. In many cases, change in wind speed above eddies was masked by a large-scale synoptic wind speed deceleration/acceleration affecting parts of the eddies.

scholarly journals An agricultural analysis of rainfall reliability for Cameroon.

1979 ◽  
Vol 27 (1) ◽  
pp. 67-78
Author(s):  
H.J.W. Mutsaers
Keyword(s):  
Joint Probability ◽  
Frequency Of Occurrence ◽  
Confidence Limits ◽  
Rainfall Distribution ◽  
Northern Area ◽  
Normalizing Transformation ◽  
Rainfall Total ◽  
Dry Spells ◽  
Dry Spell ◽  
Semi Arid

An improvement of Manning's analysis of rainfall reliability is presented. Confidence limits of 20-day rainfall totals are calculated with a simple normalizing transformation. Rainfall distribution within a 20-day period is assessed by simply counting the frequency of occurrence of dry spells exceeding 10 days duration. The joint probability of deficient 20-day rainfall total and dry spell occurrence is estimated. The analysis is applied to two practical examples in Cameroon, including the semi-arid northern area. ADDITIONAL ABSTRACT: An improvement of Manning's analysis of rainfall reliability is presented. Confidence limits of 20-day rainfall totals were calculated with a simple normalizing transformation. Rainfall distribution within a 20-day period was assessed by simply counting the frequency of occurrence of dry spells exceeding 10 days duration. The joint probability of deficient 20-day rainfall total and dry spell occurrence was estimated. The analysis was applied to 2 practical examples in Cameroon. (Abstract retrieved from CAB Abstracts by CABI’s permission)

scholarly journals Scale invariant events and dry spells for medium-resolution local rain data

2014 ◽  
Vol 21 (2) ◽  
pp. 555-567 ◽  
Author(s):  
A. Deluca ◽  
Á. Corral
Keyword(s):  
Finite Size ◽  
Mediterranean Coast ◽  
Rain Event ◽  
Scale Invariant ◽  
Scaling Properties ◽  
Medium Resolution ◽  
Dry Spells ◽  
Dry Spell ◽  
Rain Events ◽  
Rain Data

Abstract. We analyze distributions of rain-event sizes, rain-event durations, and dry-spell durations for data obtained from a network of 20 rain gauges scattered in a region of the northwestern Mediterranean coast. While power-law distributions model the dry-spell durations with a common exponent 1.50 ± 0.05, density analysis is inconclusive for event sizes and event durations, due to finite size effects. However, we present alternative evidence of the existence of scale invariance in these distributions by means of different data collapses of the distributions. These results demonstrate that scaling properties of rain events and dry spells can also be observed for medium-resolution rain data.

scholarly journals Spatial and Temporal Analysis of Dry and Wet Spells in Upper Awash River Basin, Ethiopia

Water ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 3051
Author(s):  
Girma Berhe Adane ◽  
Birtukan Abebe Hirpa ◽  
Chul-Hee Lim ◽  
Woo-Kyun Lee
Keyword(s):  
River Basin ◽  
Management Practices ◽  
Markov Chain Model ◽  
Temporal Analysis ◽  
Chain Model ◽  
Rainfall Analysis ◽  
Dry Spells ◽  
Dry Spell ◽  
Awash River Basin ◽  
Wet Spells

This study aimed to analyze the probability of the occurrence of dry/wet spell rainfall using the Markov chain model in the Upper Awash River Basin, Ethiopia. The rainfall analysis was conducted in the short rainy (Belg) and long rainy (Kiremt) seasons on a dekadal (10–day) scale over a 30-year period. In the Belg season, continuous, three-dekad dry spells were prevalent at all stations. Persistent dry spells might result in meteorological, hydrological, and socio-economic drought (in that order) and merge with the Kiremt season. The consecutive wet dekads of the Kiremt season indicate a higher probability of wet dekads at all stations, except Metehara. This station experienced a short duration (dekads 20–23) of wet spells, in which precipitation is more than 50% likely. Nevertheless, surplus rainwater may be recorded at Debrezeit and Wonji only in the Kiremt season because of a higher probability of wet spells in most dekads (dekads 19–24). At these stations, rainfall can be harvested for better water management practices to supply irrigation during the dry season, to conserve moisture, and to reduce erosion. This reduces the vulnerability of the farmers around the river basin, particularly in areas where dry spell dekads are dominant.

scholarly journals The potential value of seasonal forecasts in a changing climate in southern Africa

2014 ◽  
Vol 18 (4) ◽  
pp. 1525-1538 ◽  
Author(s):  
H. C. Winsemius ◽  
E. Dutra ◽  
F. A. Engelbrecht ◽  
E. Archer Van Garderen ◽  
F. Wetterhall ◽  
...  
Keyword(s):  
Climate Change ◽  
Heat Stress ◽  
Southern Africa ◽  
Weather Conditions ◽  
Stress Conditions ◽  
Mitigation Measures ◽  
Seasonal Forecasts ◽  
Weather Forecasts ◽  
Dry Spells ◽  
The Future

Abstract. Subsistence farming in southern Africa is vulnerable to extreme weather conditions. The yield of rain-fed agriculture depends largely on rainfall-related factors such as total seasonal rainfall, anomalous onsets and lengths of the rainy season and the frequency of occurrence of dry spells. Livestock, in turn, may be seriously impacted by climatic stress with, for example, exceptionally hot days, affecting condition, reproduction, vulnerability to pests and pathogens and, ultimately, morbidity and mortality. Climate change may affect the frequency and severity of extreme weather conditions, impacting on the success of subsistence farming. A potentially interesting adaptation measure comprises the timely forecasting and warning of such extreme events, combined with mitigation measures that allow farmers to prepare for the event occurring. This paper investigates how the frequency of extreme events may change in the future due to climate change over southern Africa and, in more detail, the Limpopo Basin using a set of climate change projections from several regional climate model downscalings based on an extreme climate scenario. Furthermore, the paper assesses the predictability of these indicators by seasonal meteorological forecasts of the European Centre for Medium-Range Weather Forecasts (ECMWF) seasonal forecasting system. The focus is on the frequency of dry spells as well as the frequency of heat stress conditions expressed in the temperature heat index. In areas where their frequency of occurrence increases in the future and predictability is found, seasonal forecasts will gain importance in the future, as they can more often lead to informed decision-making to implement mitigation measures. The multi-model climate projections suggest that the frequency of dry spells is not likely to increase substantially, whereas there is a clear and coherent signal among the models of an increase in the frequency of heat stress conditions by the end of the century. The skill analysis of the seasonal forecast system demonstrates that there is a potential to adapt to this change by utilizing the weather forecasts, given that both indicators can be skilfully predicted for the December–February season, at least 2 months ahead of the wet season. This is particularly the case for predicting above-normal and below-normal conditions. The frequency of heat stress conditions shows better predictability than the frequency of dry spells. Although results are promising for end users on the ground, forecasts alone are insufficient to ensure appropriate response. Sufficient support for appropriate measures must be in place, and forecasts must be communicated in a context-specific, accessible and understandable format.

scholarly journals The Soil Moisture during Dry Spells Model and Its Verification

Resources ◽  
2020 ◽  
Vol 9 (7) ◽  
pp. 85
Author(s):  
Małgorzata Biniak-Pieróg ◽  
Mieczysław Chalfen ◽  
Andrzej Żyromski ◽  
Andrzej Doroszewski ◽  
Tomasz Jóźwicki
Keyword(s):  
Soil Moisture ◽  
Least Squares Method ◽  
Soil Depth ◽  
Soil Layer ◽  
Atmospheric Precipitation ◽  
Soil Surface ◽  
Model Verification ◽  
Individual Measurement ◽  
Dry Spells ◽  
Dry Spell

The objective of this study was the development and verification of a model of soil moisture decrease during dry spells—SMDS. The analyses were based on diurnal information of the occurrence of atmospheric precipitation and diurnal values of soil moisture under a bare soil surface, covering the period of 2003–2019, from May until October. A decreasing exponential trend was used for the description of the rate of moisture decrease in six layers of the soil profile during dry spells. The least squares method was used to determine, for each dry spell and soil depth, the value of exponent α , which described the rate of soil moisture decrease. Data from the years 2003–2015 were used for the identification of parameter α of the model for each of the layers separately, while data from 2016–2019 were used for model verification. The mean relative error between moisture values measured in 2016–2019 and the calculated values was 3.8%, and accepted as sufficiently accurate. It was found that the error of model fitting decreased with soil layer depth, from 8.1% for the surface layer to 1.0% for the deepest layer, while increasing with the duration of the dry spell at the rate of 0.5%/day. The universality of the model was also confirmed by verification made with the use of the results of soil moisture measurements conducted in the years 2009–2019 at two other independent locations. However, it should be emphasized that in the case of the surface horizon of soil, for which the process of soil drying is a function of factors occurring in the atmosphere, the developed model may have limited application and the obtained results may be affected by greater errors. The adoption of calculated values of coefficient α as characteristic for the individual measurement depths allowed calculation of the predicted values of moisture as a function of the duration of a dry spell, relative to the initial moisture level adopted as 100%. The exponential form of the trend of soil moisture changes in time adopted for the analysis also allowed calculation of the duration of a hypothetical dry spell t, after which soil moisture at a given depth drops from the known initial moisture θ0 to the predicted moisture θ. This is an important finding from the perspective of land use.

scholarly journals Downscaling summer rainfall in the UK from North Atlantic ocean temperatures

2001 ◽  
Vol 5 (2) ◽  
pp. 245-257 ◽  
Author(s):  
R. L. Wilby
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Summer Rainfall ◽  
Model Parameters ◽  
Rainfall Forecasting ◽  
Dry Spells ◽  
Dry Spell ◽  
The Uk ◽  
Sst Anomalies

Abstract. Annual series of three stochastic rainfall model parameters — the seasonal wet day amount (or intensity), the conditional dry–day probability (or dry–spell persistence), and the conditional wet-day probability (or wet-spell persistence) — were examined using daily rainfall records for ten UK stations for the period 1901–1995. The purpose was first, to determine the extent to which these indices of summer (June–August) rainfall were correlated with empirical orthogonal functions (EOFs) of summer North Atlantic sea surface temperature (SST) anomalies: second, to evaluate the skill of EOFs of preceding winter (December–February) SSTs for summer rainfall forecasting and downscaling.Correlation analyses suggest that observed increases in summer dry-spell persistence since the 1970s coincided with positive SST anomalies in the North Atlantic. In contrast, wet-spell persistence and intensities were relatively weakly correlated with the same patterns, implying that the use of SSTs is justifiable for conditioning occurrence but not intensity parameters. Furthermore, the correlation strengths were greater for EOFs of SSTs than those reported for area-average SST anomalies, indicating that the pattern of SST anomalies conveys important information about seasonal rainfall anomalies across the UK. When EOFs of winter SSTs were used to forecast summer rainfall in Cambridge, the skill was once again greater for dry-spells than either wet-spells or intensities. However, even for dry–spells, the correlation with observations — whilst statistically significant — was still rather modest (r<0.4). Nonetheless, the results are comparable to previous investigations of summer rainfall across Europe, and suggest that forecasting skill (across the UK) originates from the predictability of the rainfall occurrence process. Keywords: North Atlantic, ocean temperatures, downscaling, rainfall, forecasting, UK

scholarly journals Traumatic and Nontraumatic Driving Accidents Due to Dry Spells in Northern Iran: A Time Series Analysis

2018 ◽  
Vol 10 (4) ◽  
pp. 723-730
Author(s):  
Enayatollah Homaie Rad ◽  
Shahrokh Yousefzadeh-Chabok ◽  
Zahra Mohtasham-Amiri ◽  
Naeima Khodadadi-Hasankiadeh ◽  
Ali Davoudi-Kiakalayeh ◽  
...  
Keyword(s):  
Time Series ◽  
Traffic Accidents ◽  
Road Traffic ◽  
Road Traffic Accidents ◽  
Road Accidents ◽  
Dry Period ◽  
The Caspian Sea ◽  
Northern Iran ◽  
Dry Spells ◽  
Dry Spell

Abstract Driving in rain is very dangerous, and drivers seem not to drive properly whenever it rains. In such situations, the risk of driving increases on rainy days, especially after a prolonged dry period. This would be a problem for drivers steering on slippery roads. In this study, the effect of dry spells on road traffic accidents and resulting mortality in Rasht, Iran, located in the southern margin of the Caspian Sea, in a 3-yr period from 21 March 2014 to 19 March 2017 was examined using time series patterns. The results of the study showed that the first day after a dry spell had the greatest impact on road accidents and resulting injuries and deaths. It was also found that with increased length of a dry spell, the risk of accidents and related deaths and injuries rises.

scholarly journals Spatial Heterogeneity and Complexity of the Impact of Extreme Climate on Vegetation in China

2021 ◽  
Vol 13 (10) ◽  
pp. 5748
Author(s):  
Shuang Li ◽  
Feili Wei ◽  
Zheng Wang ◽  
Jiashu Shen ◽  
Ze Liang ◽  
...  
Keyword(s):  
Extreme Precipitation ◽  
Vegetation Index ◽  
Precipitation Amount ◽  
Extreme Temperature ◽  
Climate Indices ◽  
Natural Ecosystems ◽  
Extreme Climate ◽  
Dry Spell ◽  
Compound Type ◽  
The Impact

The impact of extreme climate on natural ecosystems and socioeconomic systems is more serious than that of the climate’s mean state. Based on the data of 1698 meteorological stations in China from 2001 to 2018, this study calculated the 27 extreme climate indices of the Expert Team on Climate Change Detection and Indices (ETCCDI). Through correlation analysis and collinearity diagnostics, we selected two representative extreme temperature indices and three extreme precipitation indices. The spatial scale of the impact of extreme climate on Normalized Difference Vegetation Index (NDVI) in China during the growing season from 2001 to 2018 was quantitatively analyzed, and the complexity of the dominant factors in different regions was discussed via clustering analysis. The research results show that extreme climate indices have a scale effect on vegetation. There are spatial heterogeneities in the impacts of different extreme climate indices on vegetation, and these impacts varied between the local, regional and national scales. The relationship between the maximum length of a dry spell (CDD) and NDVI was the most spatially nonstationary, and mostly occurred on the local scale, while the effect of annual total precipitation when the daily precipitation amount was more than the 95th percentile (R95pTOT) showed the greatest spatial stability, and mainly manifested at the national scale. Under the current extreme climate conditions, extreme precipitation promotes vegetation growth, while the influence of extreme temperature is more complicated. As regards intensity and range, the impact of extreme climate on NDVI in China over the past 18 years can be categorized into five types: the humidity-promoting type, the cold-promoting and drought-inhibiting compound type, the drought-inhibiting type, the heat-promoting and drought-inhibiting compound type, and the heat-promoting and humidity-promoting compound type. Drought is the greatest threat to vegetation associated with extreme climate in China.

scholarly journals Implementation and comparison of a suite of heat stress metrics within the Community Land Model version 4.5

2015 ◽  
Vol 8 (2) ◽  
pp. 151-170 ◽  
Author(s):  
J. R. Buzan ◽  
K. Oleson ◽  
M. Huber
Keyword(s):  
Heat Stress ◽  
Land Surface ◽  
Climate Models ◽  
Extreme Temperature ◽  
Industrial Applications ◽  
Weather Data ◽  
Data Sets ◽  
Thermodynamic Quantities ◽  
Community Land Model ◽  
Common Framework

Abstract. We implement and analyze 13 different metrics (4 moist thermodynamic quantities and 9 heat stress metrics) in the Community Land Model (CLM4.5), the land surface component of the Community Earth System Model (CESM). We call these routines the HumanIndexMod. We limit the algorithms of the HumanIndexMod to meteorological inputs of temperature, moisture, and pressure for their calculation. All metrics assume no direct sunlight exposure. The goal of this project is to implement a common framework for calculating operationally used heat stress metrics, in climate models, offline output, and locally sourced weather data sets, with the intent that the HumanIndexMod may be used with the broadest of applications. The thermodynamic quantities use the latest, most accurate and efficient algorithms available, which in turn are used as inputs to the heat stress metrics. There are three advantages of adding these metrics to CLM4.5: (1) improved moist thermodynamic quantities; (2) quantifying heat stress in every available environment within CLM4.5; and (3) these metrics may be used with human, animal, and industrial applications. We demonstrate the capabilities of the HumanIndexMod in a default configuration simulation using CLM4.5. We output 4× daily temporal resolution globally. We show that the advantage of implementing these routines into CLM4.5 is capturing the nonlinearity of the covariation of temperature and moisture conditions. For example, we show that there are systematic biases of up to 1.5 °C between monthly and ±0.5 °C between 4× daily offline calculations and the online instantaneous calculation, respectively. Additionally, we show that the differences between an inaccurate wet bulb calculation and the improved wet bulb calculation are ±1.5 °C. These differences are important due to human responses to heat stress being nonlinear. Furthermore, we show heat stress has unique regional characteristics. Some metrics have a strong dependency on regionally extreme moisture, while others have a strong dependency on regionally extreme temperature.

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