• Energy Research

Study region: The headwaters of Tarim River. Study focus: The Tarim River basin is the largest arid inland river basin in China and recently only Aksu, Yarkant and Hotan Rivers have natural hydraulic connections with it. With climate changing, the runoff from the headwaters of Tarim River basin has undergone obvious changes that significantly affected downstream areas. It is necessary to quantitatively attribute the impact of climate changes on runoff. However, the previous researches mostly focused on the Aksu River basin, and the attribution of runoff changes in the Yarkant and Hotan River basins was nearly blank. This paper is dedicated to reveal the dominated climate factors for the runoff changes in all the three tributaries with large glacier coverage, by combining the glacier-enhanced SWAT model with the original and detrended precipitation and temperature inputs. New hydrological insights for the region: It was recognized that the rising temperature respectively contributed 94 % and 66 % to streamflow increases in the Hotan and Aksu River basins with slower glacier shrinking during 1965−2007. Meanwhile, the increased precipitation contributed 87 % to streamflow increase in the Yarkant River basin with a larger glacier area retreating ratio. It is not as widely believed that the runoff changes in high glacierized basins are more correlated with temperature changes. The respective variation amplitude of temperature and precipitation should be concerned in every catchment.

ABSTRACT Shafeeque, M.; Shah, P.; Platt, T.; Sathyendranath, S.; Menon, N.N.; Balchand, A.N., and George, G., 2019. Effect of precipitation on Chlorophyll-a in an upwelling-dominated region along t...

The projected climate change substantially impacts agricultural productivity and global food security. The cropping system models (CSM) can help estimate the effects of the changing climate on current and future crop production. The current study evaluated the impact of a projected climate change under shared socioeconomic pathways (SSPs) scenarios (SSP2-4.5 and SSP5-8.5) on the grain yield of winter wheat in the North China Plain by adopting the CSM-DSSAT CERES-Wheat model. The model was calibrated and evaluated using observed data of winter wheat experiments from 2015 to 2017 in which nitrogen fertigation was applied to various growth stages of winter wheat. Under the near-term (2021–2040), mid-term (2041–2060), and long-term (2081–2100) SSP2-4.5 and SSP5-8.5 scenarios, the future climate projections were based on five global climate models (GCMs) of the sixth phase of the Coupled Model Intercomparison Project (CMIP6). The GCMs projected an increase in grain yield with increasing temperature and precipitation in the near-term, mid-term, and long-term projections. In the mid-term, 13% more winter wheat grain yield is predicted under 1.3 °C, and a 33 mm increase in temperature and precipitation, respectively, compared with the baseline period (1995–2014). The increasing CO2 concentration trends projected an increase in average grain yield from 4 to 6%, 4 to 14%, and 2 to 34% in the near-term, mid-term, and long-term projections, respectively, compared to the baseline. The adaptive strategies were also analyzed, including three irrigation levels (200, 260, and 320 mm), three nitrogen fertilizer rates (275, 330, and 385 kg ha−1), and four sowing times (September 13, September 23, October 3, and October 13). An adaptive strategy experiments indicated that sowing winter wheat on October 3 (traditional planting time) and applying 275 kg ha−1 nitrogen fertilizer and 260 mm irrigation water could positively affect the grain yield in the North China Plain. These findings are beneficial in decision making to adopt and implement the best management practices to mitigate future climate change impacts on wheat grain yields.

This study investigates the potential impacts of future climate change on crop water requirements (CWR) in different climatic zones of Pakistan and the subsequent implications for agricultural water demand and supply. Using the latest CMIP6 climate projections, we focused on Rabi and Kharif crop seasons, which are crucial for the growth of major crops in Pakistan. An empirical climate-crop and a hydrological model based on the Budyko theory were modified and forced to project future CWR changes and the potential widening of the water demand-supply gap until 2,100. Our results indicate a significant rise in mean annual CWR across all zones and emissions scenarios, with increasing rates at 2.30–2.57 mm/yr under SSP585 and 1.0–1.26 mm/yr under SSP245. Both Rabi and Kharif seasons show rising CWR, notably more under SSP585 (Kharif: 8%–14%, Rabi: 12%–15%) than SSP245 (Kharif: 4%–7%, Rabi: 6%–8%). The demand-supply gap is expected to grow notably, with arid and semi-arid zones being the most affected. Compared to 2015–2025, by 2091–2,100, the gap increased by 7%–15% (SSP245) and 15%–28% (SSP585) for Kharif and 7%–13% (SSP245) and 13%–32% (SSP585) for Rabi. To address these challenges, we recommend strategies like enhancing irrigation efficiency, adjusting crop patterns, and developing heat-resilient crops. Our insights aim to inform policy decisions on agriculture and water management in Pakistan under future climate change.

The Hindukush-Karakoram-Himalaya (HKH) mountain ranges are the sources of Asia's most important river systems, which provide fresh water to 1.4 billion inhabitants in the region. Environmental and socioeconomic conditions are affected in many ways by climate change. Globally, climate change has received widespread attention, especially regarding seasonal and annual temperatures. Snow cover is vulnerable to climate warming, particularly temperature variations. By employing Moderate Resolution Imaging Spectroradiometer (MODIS) datasets and observed data, this study investigated the seasonal and interannual variability using snow cover, vegetation and land surface temperature (LST), and their spatial and temporal trend on different elevations from 2001 to 2020 in these variables in Gilgit Baltistan (GB), northern Pakistan. The study region was categorized into five elevation zones extending from  7000 masl. Non-parametric Mann-Kendall trend tests and Sen's slope estimates indicate snow cover increases throughout the winter, but decreases significantly between June and July. In contrast, GB has an overall increasing annual LST trend. Pearson correlation coefficient (PCC) reveals a significant positive relationship between vegetation and LST (PCC = 0.73) and a significant negative relationship between LST and snow cover (PCC = - 0.74), and vegetation and snow cover (PCC = - 0.78). Observed temperature data and MODIS LST have a coefficient of determination greater than 0.59. Snow cover decreases at 3000-2000 masl elevations while increases at higher 5000 masl elevations.The vegetation in low and mid-elevation < 4000 masl zones decreases significantly annually. The temperature shows a sharply increasing trend at lower 2000-3000 masl elevations in the autumn, indicating the shifting of the winter seasons at this elevation zone. These findings better explain the spatiotemporal variations in snow cover, vegetation, and LST at various elevation zones and the interactions between these parameters at various elevations across the HKH region.

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.

Vegetation phenology is highly sensitive to climate change and has a crucial effect on the carbon balance. Prior studies have mainly investigated the effects of mean temperature and precipitation on phenology. The asymmetric and opposing response of phenology to daytime and night-time temperature remains largely unknown. Using the satellite phenology derived from GIMMS NDVI3g datasets dating back to the 1980s, we show that significantly advanced start of the season (SOS), delayed end of the season (EOS) and prolonged length of growing season (LEN) (P < 0.05) has been taking place in the Yellow River Basin in China. The extension of LEN was more attributed to the advance of SOS than a delayed EOS. The daytime Tmax and night-time Tmin had opposite effects on the timing of SOS, MOS, and EOS in 63.1%,40.0%, and 53.5% of the pixels of the study area, respectively. If higher Tmax leads to an earlier or later transition date, an increase in Tmin systematically leads to an opposite effect. These opposite effects were obvious in SOS of 70.5%, 66.2%, and 70.6% of shrubland, grassland, and crop fields, respectively. For EOS, the opposing effects accounting for 58.2%,60.2%, and 54.5% of forest land, shrubland, and grassland, respectively. These results reveal different impacts of climate change on the daytime and night-time carbon cycle in terrestrial ecosystems, and such impacts vary with the land surface type. Knowledge of these opposing responses of phenology to daytime and night-time warming may help to understand the feedback of terrestrial ecosystem structure and function to climate change, thus to improve the existing terrestrial ecosystem carbon cycle model, which is of great significance for climate change and ecology research.

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.