Some of the biggest and most pressing scientific challenges that emerged during the later part of last century are related to improving our understanding and prediction of anthropogenic or natural climate change, and its impact on climate-sensitive natural resources, such as water, that are essential for the well-being of mankind. Since the water, energy and carbon cycles in the Earth’s climate system are strongly coupled, it is generally agreed that a key to addressing the problem is to enhance our physical knowledge and understanding of the water and energy cycle of the climate system. The Global Energy and Water Cycle Experiment (GEWEX) was thus initiated by the World Climate Research Programme (WCRP) to observe, understand and model the water and energy cycle in the climate system. The goal of the GEWEX is to reproduce and predict, by means of suitable models, the variations of the global hydrological regime, its impact on atmospheric and surface dynamics, and variations in regional hydrological processes and water resources and their response to changes in the environment. There are critical scientific objectives that must be met to attain this goal. One of these is concerned with the characterization of water and energy fluxes over land areas to provide benchmark values for the present climate. In the GEWEX science plan, this pressing task is to be addressed in the so called Water and Energy Budget Study (WEBS) that is first being carried out for the individual river basins selected for the GEWEX Continental Scale Experiments (CSEs), and then collectively under the co-ordination of the GEWEX Hydrometeorology Panel (GHP).
WEBS in GEWEX CSEs differ from previous water and energy budget studies (e.g. Trenberth et al., 2001; Roads et al., 2002, among many others) mainly in the use of various observational, (re-)analysis and model data to arrive at quasi-independent estimates of a more-or-less common set of water and energy budget variables that characterize the regional water and energy cycle of the respective CSE regions. In synthesizing the WEBS results, we would like to assess our ability to (i) develop observations of basic climate variables; (ii) to simulate those observations with current models; and (iii) to develop budgets from observations, models and blended datasets such as reanalysis data. We would also want to clarify levels of uncertainty, as well as their sources, in these budgets and to recommend future research and data collections to address the problems.
The Mackenzie GEWEX Study (MAGS) is one of the CSEs selected by GEWEX to improve our understanding and modeling of the water and energy cycle in high-latitude continental regions. The Mackenzie River is one of the major river systems of the world. The Mackenzie River Basin (MRB) stretches over 15 degrees of latitude and covers about 1.8 million km2 or about 20% of the total Canadian land mass. MAGS seeks to understand and quantify the key processes that affect the water and energy cycle of the MRB, validate coupled atmospheric-hydrological-land surface models that, on monthly and longer time scales, will replicate the transport of moisture into and through the MRB and into the Arctic Ocean, and understand the changing climate system of a northern region (Stewart et al. 1998).
The purpose of MAGS WEBS is to meet the basic MAGS objective of developing state-of-the-art estimates of the water and energy budgets for the MRB. Different observed, remotely-sensed, (re-)analyzed and modeled data were utilized to obtain independent estimates of the budgets. In this preliminary effort, we will focus on basin scale vertically-integrated atmospheric and surface water and energy budgets for the period 1997-2002 (the MAGS project itself spans from 1996-2005). Comparisons of the present results to previous budget estimates will be made where possible. The credibility of current models and data assimilation systems in representing the components of the water and energy cycle of this northern and data-spare region will also be assessed.
The CDROM contains background information on the physical characteristics of the MRB, descriptions of the source datasets and methodology used in the study, as well as a comprehensive compilation of the budget results. Apart from providing an up-to-date climatology of the water and energy budgets for the basin, these results will also serve as baseline budgets for gauging future progresses in their assessments for this high-latitude continental region. Discussions of the budget results will also be presented although more thorough discussions of the results can be found in Szeto et al. (2006a) and Szeto (2006a,b,c).