• Energy Research

Here, we provided a comprehensive analysis of long-term drought and climate extreme patterns in the agro ecological zones (AEZs) of Pakistan during 1980–2019. Drought trends were investigated using the standardized precipitation evapotranspiration index (SPEI) at various timescales (SPEI-1, SPEI-3, SPEI-6, and SPEI-12). The results showed that droughts (seasonal and annual) were more persistent and severe in the southern, southwestern, southeastern, and central parts of the region. Drought exacerbated with slopes of −0.02, −0.07, −0.08, −0.01, and −0.02 per year. Drought prevailed in all AEZs in the spring season. The majority of AEZs in Pakistan’s southern, middle, and southwestern regions had experienced substantial warming. The mean annual temperature minimum (Tmin) increased faster than the mean annual temperature maximum (Tmax) in all zones. Precipitation decreased in the southern, northern, central, and southwestern parts of the region. Principal component analysis (PCA) revealed a robust increase in temperature extremes with a variance of 76% and a decrease in precipitation extremes with a variance of 91% in the region. Temperature and precipitation extremes indices had a strong Pearson correlation with drought events. Higher temperatures resulted in extreme drought (dry conditions), while higher precipitation levels resulted in wetting conditions (no drought) in different AEZs. In most AEZs, drought occurrences were more responsive to precipitation. The current findings are helpful for climate mitigation strategies and specific zonal efforts are needed to alleviate the environmental and societal impacts of drought.

AbstractQuantifying water-saving potential (WSP) is crucial for sustainable water resource management in canal command areas and river basins. Previous studies have partially or fully ignored the importance of groundwater in WSP assessments, particularly in irrigated areas. This study is aimed at quantifying WSP in the Lower Chenab Canal (LCC) command area of the Indus River Basin, Pakistan, under various scenarios of future climate change and groundwater recharge. These quantifications are conducted using an empirical model based on the Budyko theory. The model was forced using observed, remote sensing, and CMIP6 future climate data for two Shared Socioeconomic Pathways (SSP245 and SSP585) and their ensembles (cold-dry, cold-wet, warm-dry, and warm-wet) for possible futures. The results showed that the average WSP in the LCC command area was 466 ± 48 mm/year during the historical period (2001–2020). The WSP is projected to decrease by – 68 ± 3% under the warm-dry ensemble scenario (SSP245 and SSP585) and – 48 ± 13% under the ensembled cold-wet scenario by 2100. The results also demonstrated that WSP could be increased by up to 70 ± 9% by artificially recharging 20% of the abstracted groundwater per year in the LCC command area by the late twenty-first century. Our findings highlight the importance of adopting artificial groundwater recharge to enhance the WSP and sustainably manage water resources in the LCC command area. Policymakers should consider these findings when deciding on water resource management in the Indus River Basin.

The impacts of climate on spatiotemporal variations of eco-physiological and bio-physical factors have been widely explored in previous research, especially in dry areas. However, the understanding of gross primary productivity (GPP) variations and its interactions with climate in humid and semi-humid areas remains unclear. Based on hyperspectral satellite remotely sensed vegetation phenology processes and related indices and the re-analysed climate datasets, we investigated the seasonal and inter-annual variability of GPP by using different light-use efficiency (LUE) models including the Carnegie-Ames-Stanford Approaches (CASA) model, vegetation photosynthesis models (VPMChl and VPMCanopy) and Moderate Resolution Imaging Spectroradiometer (MODIS) GPP products (MOD17A2H) during 2001–2020 over the Great Lakes region of Sub-Saharan Africa (GLR-SSA). The models’ validation against the in situ GPP-based upscaled observations (GPP-EC) indicated that these three models can explain 82%, 79% and 80% of GPP variations with root mean square error (RMSE) values of 5.7, 8.82 and 10.12 g C·m−2·yr−1, respectively. The spatiotemporal variations of GPP showed that the GLR-SSA experienced: (i) high GPP values during December-May; (ii) high annual GPP increase during 2002–2003, 2011–2013 and 2015–2016 and annual decreasing with a marked alternation in other years; (iii) evergreen broadleaf forests having the highest GPP values while grasslands and croplands showing lower GPP values. The spatial correlation between GPP and climate factors indicated 60% relative correlation between precipitation and GPP and 65% correction between surface air temperature and GPP. The results also showed high GPP values under wet conditions (in rainy seasons and humid areas) that significantly fell by the rise of dry conditions (in long dry season and arid areas). Therefore, these results showed that climate factors have potential impact on GPP variability in this region. However, these findings may provide a better understanding of climate implications on GPP variability in the GLR-SSA and other tropical climate zones.

Les mesures strictes de confinement ont non seulement contribué à freiner la propagation de l'infection à COVID-19, mais ont également amélioré les conditions environnementales dans le monde entier. L'objectif principal de la présente étude était d'étudier les co-bénéfices du confinement de la COVID-19 sur l'atmosphère et le système écologique aquatique dans le cadre d'activités anthropiques restreintes en Asie du Sud. Les données de télédétection (a) des émissions de NO2 de l'instrument de surveillance de l'ozone (OMI), (b) de la profondeur optique des aérosols (AOD) du spectroradiomètre d'imagerie à résolution modérée (MODIS) et (c) de la chlorophylle (Chl-a) et des données de turbidité de MODIS-Aqua Level-3 au cours de janvier-octobre (2020) ont été analysées pour évaluer les changements dans la pollution de l'air et de l'eau par rapport aux cinq dernières années (2015–2019). Les interactions entre la pollution de l'air et de l'eau ont également été étudiées en utilisant le ruissellement terrestre et les précipitations en 2019 et 2020 à une échelle mensuelle pour enquêter sur les événements anormaux, qui pourraient affecter la charge d'azote dans les régions côtières. Les résultats ont révélé une baisse considérable de la pollution de l'air et de l'eau (réduction de 30 à 40 % des émissions de NO2, de 45 % de l'AOD, de 50 % de la concentration de chl-a sur les côtes et de 29 % de la turbidité) en Asie du Sud. Le taux de réduction des émissions de NO2 a été le plus élevé à Lahore (32 %), New Delhi (31 %), Ahmadabad (29 %), Karachi (26 %), Hyderabad (24 %) et Chennai (17 %) pendant la période de confinement strict d'avril à juin 2020. Une corrélation positive entre l'AOD et les émissions de NO2 (0,23-0,50) implique qu'une diminution de l'AOD est attribuée à une réduction du NO2. Il a été observé que pendant le confinement strict, la turbidité a diminué de 29 %, 11 %, 16 % et 17 % le long des régions côtières de Karachi, Mumbai, Calcutta et Dhaka, respectivement, tandis qu'une augmentation de 5 à 6 % de la turbidité a été observée sur les Madras au cours de la même période. Les résultats soulignent l'importance de la réduction des émissions d'azote en raison de l'arrêt de la consommation de combustibles fossiles et de leurs relations avec la réduction de la pollution de l'air et de l'eau. Il est conclu que l'environnement atmosphérique et hydrosphérique peut être amélioré en mettant en œuvre des restrictions intelligentes sur la consommation de combustibles fossiles avec un effet minimum sur la socio-économie dans la région. Des contraintes intelligentes sur l'utilisation des combustibles fossiles sont recommandées pour contrôler la pollution de l'air et de l'eau même après la reprise des activités sociales et économiques. Las estrictas medidas de confinamiento no solo contribuyeron a frenar la propagación de la infección por COVID-19, sino que también mejoraron las condiciones ambientales en todo el mundo. El objetivo principal del estudio actual fue investigar los beneficios colaterales del confinamiento por COVID-19 en la atmósfera y el sistema ecológico acuático bajo actividades antropogénicas restringidas en el sur de Asia. Los datos de teledetección (a) emisiones de NO2 del Instrumento de Monitoreo de Ozono (OMI), (b) Profundidad Óptica de Aerosol (AOD) del Espectrorradiómetro de Imágenes de Resolución Moderada (MODIS) y (c) clorofila (Chl-a) y datos de turbidez de MODIS-Aqua Nivel-3 durante enero-octubre (2020) se analizaron para evaluar los cambios en la contaminación del aire y el agua en comparación con los últimos cinco años (2015–2019). Las interacciones entre la contaminación del aire y del agua también se investigaron utilizando la escorrentía y las precipitaciones terrestres en 2019 y 2020 a escala mensual para investigar los eventos anómalos, que podrían afectar la carga de N en las regiones costeras. Los resultados revelaron una caída considerable en la contaminación del aire y el agua (reducción del 30–40% en las emisiones de NO2, 45% en AOD, disminución del 50% en la concentración costera de Chl-a y disminución del 29% en la turbidez) en el sur de Asia. La tasa de reducción de las emisiones de NO2 fue la más alta para Lahore (32%), Nueva Delhi (31%), Ahmadabad (29%), Karachi (26%), Hyderabad (24%) y Chennai (17%) durante el estricto período de confinamiento de abril a junio de 2020. Una correlación positiva entre AOD y las emisiones de NO2 (0.23-0.50) implica que una disminución en AOD se atribuye a una reducción en NO2. Se observó que durante el confinamiento estricto, la turbidez ha disminuido en un 29%, 11%, 16% y 17% a lo largo de las regiones costeras de Karachi, Mumbai, Calcuta y Dhaka, respectivamente, mientras que se observó un aumento del 5–6% en la turbidez en Madras durante el mismo período. Los hallazgos enfatizan la importancia de reducir las emisiones de N debido a la interrupción del consumo de combustibles fósiles y sus relaciones con la reducción de la contaminación del aire y el agua. Se concluye que el ambiente atmosférico e hidrosférico puede mejorarse mediante la implementación de restricciones inteligentes en el consumo de combustibles fósiles con un efecto mínimo en la socioeconómica de la región. Se recomiendan restricciones inteligentes en el uso de combustibles fósiles para controlar la contaminación del aire y del agua incluso después de que las actividades sociales y económicas reanuden el escenario habitual. The strict lockdown measures not only contributed to curbing the spread of COVID-19 infection, but also improved the environmental conditions worldwide. The main goal of the current study was to investigate the co-benefits of COVID-19 lockdown on the atmosphere and aquatic ecological system under restricted anthropogenic activities in South Asia. The remote sensing data (a) NO2 emissions from the Ozone Monitoring Instrument (OMI), (b) Aerosol Optical Depth (AOD) from the Moderate Resolution Imaging Spectroradiometer (MODIS), and (c) chlorophyll (Chl-a) and turbidity data from MODIS-Aqua Level-3 during Jan–Oct (2020) were analyzed to assess the changes in air and water pollution compared to the last five years (2015–2019). The interactions between the air and water pollution were also investigated using overland runoff and precipitation in 2019 and 2020 at a monthly scale to investigate the anomalous events, which could affect the N loading to coastal regions. The results revealed a considerable drop in the air and water pollution (30–40% reduction in NO2 emissions, 45% in AOD, 50% decline in coastal Chl-a concentration, and 29% decline in turbidity) over South Asia. The rate of reduction in NO2 emissions was found the highest for Lahore (32%), New Delhi (31%), Ahmadabad (29%), Karachi (26%), Hyderabad (24%), and Chennai (17%) during the strict lockdown period from Apr–Jun, 2020. A positive correlation between AOD and NO2 emissions (0.23–0.50) implies that a decrease in AOD is attributed to a reduction in NO2. It was observed that during strict lockdown, the turbidity has decreased by 29%, 11%, 16%, and 17% along the coastal regions of Karachi, Mumbai, Calcutta, and Dhaka, respectively, while a 5–6% increase in turbidity was seen over the Madras during the same period. The findings stress the importance of reduced N emissions due to halted fossil fuel consumption and their relationships with the reduced air and water pollution. It is concluded that the atmospheric and hydrospheric environment can be improved by implementing smart restrictions on fossil fuel consumption with a minimum effect on socioeconomics in the region. Smart constraints on fossil fuel usage are recommended to control air and water pollution even after the social and economic activities resume business-as-usual scenario. لم تساهم إجراءات الإغلاق الصارمة في الحد من انتشار عدوى COVID -19 فحسب، بل أدت أيضًا إلى تحسين الظروف البيئية في جميع أنحاء العالم. كان الهدف الرئيسي من الدراسة الحالية هو التحقيق في الفوائد المشتركة لإغلاق COVID -19 على الغلاف الجوي والنظام البيئي المائي في ظل الأنشطة البشرية المقيدة في جنوب آسيا. تم تحليل بيانات الاستشعار عن بعد (أ) انبعاثات ثاني أكسيد النيتروجين من جهاز مراقبة الأوزون (OMI)، (ب) العمق البصري للهباء الجوي (AOD) من مقياس الطيف التصويري متوسط الدقة (MODIS)، و (ج) بيانات الكلوروفيل (Chl - a) والتعكر من MODIS - Aqua Level -3 خلال الفترة من يناير إلى أكتوبر (2020) لتقييم التغيرات في تلوث الهواء والماء مقارنة بالسنوات الخمس الماضية (2015–2019). كما تم التحقيق في التفاعلات بين تلوث الهواء والمياه باستخدام الجريان السطحي وهطول الأمطار في عامي 2019 و 2020 على نطاق شهري للتحقيق في الأحداث الشاذة، والتي يمكن أن تؤثر على تحميل N إلى المناطق الساحلية. كشفت النتائج عن انخفاض كبير في تلوث الهواء والماء (انخفاض بنسبة 30-40 ٪ في انبعاثات ثاني أكسيد النيتروجين، و 45 ٪ في AOD، وانخفاض بنسبة 50 ٪ في تركيز Chl - a الساحلي، وانخفاض بنسبة 29 ٪ في التعكر) فوق جنوب آسيا. وجد أن معدل الانخفاض في انبعاثات ثاني أكسيد النيتروجين هو الأعلى في لاهور (32 ٪) ونيودلهي (31 ٪) وأحمد أباد (29 ٪) وكراتشي (26 ٪) وحيدر أباد (24 ٪) وتشيناي (17 ٪) خلال فترة الإغلاق الصارمة من أبريل إلى يونيو 2020. تشير العلاقة الإيجابية بين انبعاثات أكسيد النيتروجين وثاني أكسيد النيتروجين (0.23-0.50) إلى أن انخفاض أكسيد النيتروجين يعزى إلى انخفاض ثاني أكسيد النيتروجين. لوحظ أنه خلال الإغلاق الصارم، انخفض التعكر بنسبة 29 ٪ و 11 ٪ و 16 ٪ و 17 ٪ على طول المناطق الساحلية في كراتشي ومومباي وكلكتا ودكا، على التوالي، في حين لوحظت زيادة بنسبة 5-6 ٪ في التعكر فوق مدراس خلال نفس الفترة. وتشدد النتائج على أهمية خفض انبعاثات النيتروجين بسبب وقف استهلاك الوقود الأحفوري وعلاقاتها بانخفاض تلوث الهواء والماء. وخلص إلى أنه يمكن تحسين البيئة الجوية والمائية من خلال تنفيذ قيود ذكية على استهلاك الوقود الأحفوري بأقل تأثير على الاقتصاد الاجتماعي في المنطقة. يوصى بالقيود الذكية على استخدام الوقود الأحفوري للسيطرة على تلوث الهواء والماء حتى بعد استئناف الأنشطة الاجتماعية والاقتصادية لسيناريو العمل كالمعتاد.

This study investigates the relative role of land surface schemes (LSS) in the Weather Research and Forecasting (WRF) model, Version 4, to simulate the heat wave events in Karachi, Pakistan during 16–23 May 2018. The efficiency of the WRF model was evaluated in forecasting heat wave events over Karachi using the three different LSS, namely NOAH, NOAH-MP, and RUC. In addition to this we have used the longwave (RRTM) and shortwave (Dudhia) in all schemes. Three simulating setups were designed with a combination of shortwave, longwave, and LSS: E1 (Dudhia, RRTM, and Noah), E2 (Dudhia, RRTM, and Noah-MP), and E3 (Dudhia, RRTM, and RUC). All setups were carried out with a finer resolution of 1 km × 1 km. Findings of current study depicted that E2 produces a more realistic simulation of daily maximum temperature T(max) at 2 m, sensible heat (SH), and latent heat (LH) because it has higher R2 and lower errors (BIAS, RMSE, MAE) compared to other schemes. Consequently, Noah-MP (LSS) accurately estimates T(max) and land surface heat fluxes (SH&LH) because uses multiple physics options for land atmosphere interaction processes. According to statistical analyses, E2 setup outperforms other setups in term of T(max) and (LH&SH) forecasting with the higher Nash-Sutcliffe efficiency (NSE) agreement is 0.84 (0.89). This research emphasizes that the selection of LSS is of vital importance in the best simulation of T(max) and SH (LH) over Karachi. Further, it is resulted that the SH flux is taking a higher part to trigger the heat wave event intensity during May 2018 due to dense urban canopy and less vegetated area. El Niño-Southern Oscillation (ENSO) event played role to prolong and strengthen the heat wave period by effecting the Indian Ocean Dipole (IOD) through walker circulation extension.