Recent heat waves have been a matter of serious concern for India because of potential impacts on agriculture, food security, and socioeconomic progress. This study examines the trends and variability in frequency, duration, and intensity of hot episodes during three time periods (1951–2013, 1981–2013 and 1998–2013) by defining heat waves based on the percentile of maximum, minimum, and mean temperatures. The study also explores heat waves and their relationships with hydroclimatic variables, such as rainfall, terrestrial water storage, Palmer drought severity index, and sea surface temperature. Results reveal that the number, frequency, and duration of daytime heat waves increased considerably during the post‐1980 dry and hot phase over a large area. The densely populated and agriculturally dominated northern half of India stands out as a key region where the nighttime heat wave metrics reflected the most pronounced amplifications. Despite the recent warming hiatus in India and other parts of the world, we find that both daytime and nighttime extreme measures have undergone substantial changes during or in the year following a dry year since 2002, with the probability distribution functions manifesting a hotter‐than‐normal climate during 1998–2013. This study shows that a few months preceding the 2010 record‐breaking heat wave in Russia, India experienced the largest hot episode in the country's history. Interestingly, both these mega events are comparable in terms of their evolution and amplification. These findings emphasize the importance of planning for strategies in the context of the rising cooccurrence of dry and hot events.

No abstract

Remote sensing techniques are becoming powerful tools for efficient management of irrigation systems in large irrigated areas. The objectives of management of irrigation systems, although they vary widely, may be defined as high crop productivity per unit land per unit applied water with equity in distribution. Some of the key elements of irrigation system management are: (i) performance monitoring and evaluation, (ii) diagnostic appraisal, (iii) action research, and (iv) farmers' participation. The objective of this paper is to present the state of the art on applications of satellite remote sensing that support management of irrigation systems and to identify emerging approaches that focus on future directions of research which may pave the way to operationalise the remote sensing techniques in practice. Firstly, a brief review on different approaches being utilized for management of irrigation systems is dealt with. Subsequently, the present status of remote sensing applications in irrigated agriculture is reviewed. The paper also presents future perspectives of remote sensing applications in determining hydrological variables and quantifying irrigation system performance indicators for better management of water use in irrigated agriculture. Copyright © 2002 John Wiley & Sons, Ltd.KEY WORDS: remote sensing; irrigation system management; performance monitoring; large irrigated commands; spatial hydrological modelling RÉ SUMÉ Les techniques de télédétection deviennent des outils puissants pour la gestion efficace des systèmes d'irrigation dans de grands périmètres irrigués. Les objectifs de la gestion des systèmes d'irrigation, bien que très variés, peuvent être définis en tant que productivité par hectare et par unité d'eau appliquée avec l'équité de la distribution. Certains des éléments principaux de la gestion de systèmes d'irrigation sont (i) la surveillance et l'évaluation de la performance, (ii) le diagnostique, (iii) la recherche active, et (iv) la participation des agriculteurs. L'objectif de cet article est de présenter la situation actuelle des applications de la télédétection par satellite appliquée aux systèmes d'irrigation et d'identifier les directions futures de la recherche pour préparer le terrain pour les techniques de télédétection dans la pratique. Premièrement, une brève revue des différentes approches utilisées pour la gestion des systèmes d'irrigation est traitée comme prétexte. La suite présente le statut actuel des applications de télédétection dans l'agriculture irriguée. La communication présente également quelques perspectives futures des applications de télédé-tection pour la détermination des variables hydrologiques et pour mesurer les indicateurs de performance des systèmes d'irrigation.

No abstract