This book is a collection of seven in-depth and detailed research papers authored by Dr. Raman K Attri between 1996 to 2005. The book presents early-career scientific work by the author as a scientist at a research organization. The book provides the conceptual background and key electronics and mechanical design principles used in designing sensors and instrumentation systems to measure snow hydrological parameters. The systems discussed in this book can be used to measure snow depth, layer temperature, temperature distribution profile, surface porosity, etc. The snow parameters measured from instruments and sensors discussed in this book are integrated into larger systems and are used in computer-driven models for snow avalanche predictions. The book presents the design challenges and design methods from electronics and instrumentation design point of view. While the book provides essential understanding of analog electronics design and associated mechanical design for snow hydrological sensors, the book also presents the background theoretical and mathematical models from snow hydrology physics that governs this electronics design. The first research paper discusses the design control techniques used to the design a remote surface detector to detect objects with porous, uneven, irregular surfaces like snow using ultrasonic beams. The second research paper describes signal processing techniques and electronics design approaches to design a snow depth sensor with improved sensitivity and directional response using Ultrasonic Pulse-Transit Method. The third research paper explains theoretical and mathematical model that governs the physical, mechanical, and electronics design to implement the theory of Arrayed Ultrasonic transducers to shape up the directional response and beam width of an ultrasonic beam to improve the chances of receiving sufficient reflection from the non-smooth, highly porous, uneven, non-planar, irregular snow surface. The fourth paper presents the design considerations and performance characteristics of Snow Temperature Profile Sensing System used to measure the temperature gradient and temperature distributions within and outside the snowpack at different depths. The fifth research paper focuses on describing the design of Snow Temperature Profile Sensing System in details and discusses the theoretical and mathematical model that outline important temperature parameters. Then the paper describes how the system is implemented to record or measure those parameters. The sixth paper presents the design considerations, constraints and design techniques used to use RTD temperature sensors for snow temperature measurement applications. The paper also presents the performance evaluation and suitability of such sensors. The seventh paper focuses design techniques for front-end analog signal conditioning module and the design challenges faced when interfacing analog unit to a data acquisition system. The eighth paper describes the design of snow air temperature sensing probe and methods to ensure that it measures true air temperature over a snow cover and is not influenced by solar radiations and winds. The book may be read as an applied text-book in conjunction with standard electronics and instrumentation design textbooks. The book will guide students on how to apply basic principles of instrumentation systems design, integrate concepts of physical sciences and measurement sciences for the field applications.

In recent years, much concern has been expressed on the deleterious effects that anthropogenic emissions of acidic pollutants have on ecosystems of both industrialized countries and remote areas of the world. In many of these regions, seasonal snowcover is a major factor in the transfer of atmospheric pollutants, either to terrestrial and aquatic ecosystems or to the more permanent reservoirs of glaciers and ice sheets. The recognition of the role that seasonal snowcovers can thus play in the chemical dynamics of whole ecosystems was recently echoed by the Committee on Glaciology of the National Research Council (National Academy of Sciences, National Academy of Engineering and the Institute of Medicine) which recommended that studies on "Impurities in the snowpack, their discharge into runoff, and management of the problem" be rated at the highest prority level (ref. a). It is in this context that the Advanced Research Institute (ASI) brought together scientists active in the fields of snow physics, snow chemistry and snow hydrology. The programme was structured so as to facilitate the exchange of information and ideas on the theories for the chemical evolution of seasonal snowcovers and snowmelt and on the impact of the chemical composition of the meltwaters on the different components of hydrological systems. As a consequence the ASI also attracted participants from potential users of the information that was disseminated; these were particularly concerned with the effects of snowmelt and snowcover on terrestrial biota and those of lakes and streams.

Modeling of the rainfall-runoff process is of both scientific and practical significance. Many of the currently used mathematical models of hydrologic systems were developed a genera tion ago. Much of the effort since then has focused on refining these models rather than on developing new models based on improved scientific understanding. In the past few years, however, a renewed effort has been made to improve both our fundamental understanding of hydrologic processes and to exploit technological advances in computing and remote sensing. It is against this background that the NATO Advanced Study Institute on Recent Advances in the Modeling of Hydrologic Systems was organized. The idea for holding a NATO ASI on this topic grew out of an informal discussion between one of the co-directors and Professor Francisco Nunes-Correia at a previous NATO ASI held at Tucson, Arizona in 1985. The Special Program Panel on Global Transport Mechanisms in the Geo-Sciences of the NATO Scientific Affairs Division agreed to sponsor the ASI and an organizing committee was formed. The committee comprised the co directors, Professor David S. Bowles (U.S.A.) and Professor P. Enda O'Connell (U.K.), and Professor Francisco Nunes-Correia (Portugal), Dr. Donn G. DeCoursey (U.S.A.), and Professor Ezio Todini (Italy).