Hydroclimatology and Climate Variability

by

Natalie Teale

• LAST REVIEWED: 15 January 2020
• LAST MODIFIED: 15 January 2020
• DOI: 10.1093/obo/9780199874002-0216

Introduction

The field of hydroclimatology was developed to synthesize many separate but related topics describing the storage and flux of water between and within the atmosphere and the land surface. By synthesizing these topics, including precipitation, evaporation, water vapor, streamflow, and soil moisture, among others, their interactions with each other and their effects on the earth surface can be assessed better across time and space. Hydroclimatology therefore can be defined as the interdisciplinary study of cyclical, multidirectional interactions between the climate system and the hydrologic cycle on a variety of spatial and temporal scales. Much of the research in the field of hydroclimatology is rooted in the identification of the baseline conditions of these interactions and deviations from those conditions. Because the movement, storage, and phase change of water between and within the terrestrial and atmospheric systems is closely linked to energy budgets, the components of hydroclimatology are sensitive to climate variability. This sensitivity to climate and weather patterns is particularly important because of the plethora of hydroclimatic feedbacks that have been modeled and observed. For example, there are notable feedbacks between water vapor and temperature, soil moisture and precipitation, and snow cover and air temperature, among others. Hydroclimatology as a subfield of climatology is well situated to investigate these feedbacks, as some involve interactions between multiple components in the atmosphere and land surface. The sensitivity of hydroclimatological interactions to climate variability is also important in a climate change context. Many studies demonstrate the intensification of the water cycle associated with a warmer atmosphere, resulting in changes in precipitation regimes, flood magnitude and frequency, and drought persistence and intensity, among others. These extreme events can be damaging and costly, and their impacts can be far reaching across human and environmental spheres. Hydroclimatology in this context is well situated within the discipline of physical geography. This article provides a general overview to the field of hydroclimatology, followed by sections addressing several individual components of hydroclimatology. The article concludes with a selection of papers investigating regional hydroclimatologies.

General Overview

Several sources exist in the literature introducing hydroclimatology. Mather 1991 outlines the history of the field of hydroclimatology as it developed in the 20th century. Of particular note from this account is the key role the concept potential evapotranspiration played in synthesizing many hydrological, climatological, meteorological, and biogeophysical components into the field of hydroclimatology. Shelton 2009 serves as the main textbook on hydroclimatology. This textbook outlines many key components of the field, including data and methods. Shelton 2009 also details the climate energy budget, an understanding of which is crucial for understanding and appreciating hydroclimatology. Houser 2017 provides a brief overview of hydroclimatology, highlighting the intersection of all the environmental spheres in the discipline. Many introductory sources approach hydroclimatology through the lens of climate variability and anthropogenic climate change. Allen and Ingram 2002 discusses likely changes in the hydrologic cycle in a warmer climate. Huntington 2006 reviews the literature on changes in many components of hydroclimatology to ascertain a strengthening of the hydrologic cycle. Held and Soden 2006 also discuss changes in the hydrological cycle, focusing on atmospheric hydroclimatological and hydrometeorological variables. The future of hydroclimatological research given these changes is discussed in Hirschboeck 2009. Finally, much of the research conducted in hydroclimatology and climate variability deals with climate extremes. A conceptual framework for why changes in the extremes are particularly noteworthy in a climate-change context is supplied in Trenberth 1999. Hao, et al. 2018 discusses how the impacts of extreme hydroclimatic events are intensified when these events occur simultaneously or in near succession. Changes in the hydroclimatological, multidirectional fluxes of moisture through the earth system are reviewed robustly in prominent reports listed in the separate Oxford Bibliographies article Climatology. Because hydroclimatology overlaps and synergizes with many disciplines such as climatology, meteorology, hydrology, physical geography, water resources, and earth systems, credible hydroclimatological research can be found in journals in each of these fields. Many of the resources useful to hydroclimatologists, including software and data access, are also listed and discussed in sections of the separate Oxford Bibliographies article Climatology. These resources can be used to investigate many feedbacks in hydroclimatology as well as the impacts of changes in hydroclimatological elements. Additionally, because hydroclimatology bridges the gap between hydrology and climatology, an understanding of hydroclimatology may be enriched by the separate Oxford Bibliographies articles Hydrology, and Climatology, particularly through the textbooks listed in these separate articles.

• Allen, M. R., and W. J. Ingram. “Constraints on Future Changes in Climate and the Hydrologic Cycle.” Nature 419 (September 2002): 224–232.

  DOI: 10.1038/nature01092

  This review article argues that while weather can be difficult to predict on short timescales, the climate response to increasing concentrations of greenhouse gases on longer timescales may be simpler to predict. This paper also discusses how changes in the hydrologic cycle will be more difficult to quantify than changes in global-mean temperature. This is due to fewer observations as well as challenges in understanding the physical constraints of the hydrologic cycle.

• Hao, Z., V. P. Singh, and F. Hao. “Compound Extremes in Hydroclimatology: A Review.” Water (Switzerland) 10.6 (2018): 16–21.

  DOI: 10.3390/w10060718

  This paper acknowledges the impact of extreme hydroclimatic events and investigates the increased impact of these extreme events occurring simultaneously or sequentially (i.e., compound events) through a variety of methods.

• Held, I. M., and B. J. Soden. “Robust Responses of the Hydrological Cycle to Global Warming.” Journal of Climate 19 (2006): 5686–5699.

  DOI: 10.1175/JCLI3990.1

  This paper discusses the changes reported consistently across models in the AR4 of the IPCC, including column-integrated water vapor, convective mass fluxes, horizontal moisture transport, evaporation minus precipitation patterns, and horizontal sensible heat transport.

• Hirschboeck, K. K. “Future Hydroclimatology and the Research Challenges of a Post-Stationary World.” Journal of Contemporary Water Research & Education 142.1 (2009): 4–9.

  DOI: 10.1111/j.1936-704x.2009.00045.x

  This paper responds to a statement that hydroclimatological regimes are moving beyond stationary distributions, offering several questions framing aspects of hydroclimatological research in a “post-stationary world” and reviewing methods for operating in a framework different from historical research.

• Houser, P. “Hydroclimatology and Hydrometeorology.” In The International Encyclopedia of Geography. (2017).

  DOI: 10.1002/9781118786352.wbieg0966

  This encyclopedia entry introduces hydroclimatology from a hydrologic balance perspective before describing components of the hydroclimate system from an environmental spheres approach, discussing the independent and interactive roles of the atmosphere, hydrosphere, cryosphere, lithosphere, biosphere, and anthroposphere in hydroclimatology. The article lists challenges associated with water and how they can be addressed through hydroclimatological research.

• Huntington, T. G. “Evidence for Intensification of the Global Water Cycle: Review and Synthesis.” Journal of Hydrology 319.1–4 (2006): 83–95.

  DOI: 10.1016/j.jhydrol.2005.07.003

  This paper reviews the literature on several hydroclimatic components, including precipitation, runoff, water vapor, soil moisture, glacial mass, evaporation, evapotranspiration, and phenology to assess the strengthening of the hydrologic cycle.

• Mather, J. R. “A History of Hydroclimatology.” Physical Geography 12.3 (1991): 260–273.

  DOI: 10.1080/02723646.1991.10642432

  This account of the development and evolution of hydroclimatology traces the roots of the discipline from the ancient Greeks to the Renaissance to modern scholars. This paper notes the significance of Thornthwaite’s potential evapotranspiration theory in 20th century, which tied together many basic hydroclimatic elements into one concept.

• Shelton, M. L. Hydroclimatology: Perspectives and Applications. Cambridge, UK: Cambridge University Press, 2009.

  This textbook provides an overview of the climate system with water as a “unifying concept.” In addition to the concepts it puts forward, this text also presents methods for measuring hydroclimatic elements and working with hydroclimatic data, from in situ measurements to remote sensing. This book is appropriate for advanced undergraduate and graduate students specializing in climatology and/or hydrology. This is the primary textbook for hydroclimatology.

• Trenberth, K. E. “Conceptual Framework for Changes of Extremes of the Hydrological Cycles With Climate Change.” Climatic Change 42.1 (1999): 327–339.

  DOI: 10.1023/A:1005488920935

  Presents a conceptual framework for how the hydrological cycle is impacted by an increase in greenhouse gas concentrations, linking several hydroclimatic elements from increased downwelling infrared radiation to atmospheric moisture to streamflow. This paper focuses on hydrological extremes, particularly extreme precipitation.