Water Budgets

In order to fully understand long-term climate changes, analyses of observed and model-simulated climate changes, especially aspects related to the global hydrological cycle should be given due dilligence. Such aspects include: changes in atmospheric and near-surface water vapor, humidity, cloudiness, precipitation amount, frequency, intensity and diurnal cycle, evaporation, soil moisture, drought, runoff, streamflow, and continental freshwater discharge.

Associated Images:

Hydrologic Cycle

The hydrological cycle. Estimates of the main water reservoirs, given in plain font in 103 km3, and the flow of moisture through the system, given in slant font (103 km3 yr-1, equivalent to Eg (1018 g) yr-1 . - From Trenberth et al., 2007


Stream Flow

Adapted time series of 20°N to 20°S ERBS non-scanner wide-field-of-view broadband short- wave, longwave, and net radiation anomalies from 1985 to 1999 [Wielicki et al., 2002a, 2002b] where the anomalies are defined with respect to the 1985 to 1989 period with Edition 3_Rev 1 data [Wong et al., 2006]. - From Trenberth and Dai, 2007.


Pinatubo effects

Time series of the annual water year (Oct. to Sep.); note slight offset of points plotted vs. tick marks indicating January continental freshwater discharge and land precipitation (from Figure 1) for the 1985 to 1999 period. The period clearly influenced by the Mount Pinatubo eruption is indicated by grey shading. - From Trenberth and Dai, 2007


Budget Trends

Basin-averaged trends in the water and energy budget components for the Mississippi River basin: M is the long-term (1948–2004) annual (water year) mean (in mm for water components and W m 2 for energy components) and b is the annual linear trend during 1948–2004 (in mm century 1 for water components and W m 2 century 1 for energy components, proportional to arrow shaft width). Note that the downward arrow means that the flux increases the trend of dW/dt or G. - From Qian et al., 2007.


Global map of water budget trends

Linear trends from 1948-2004 in annual (water year) runoff trend inferred from the discharge. - Adapated from Dai et al., 2009.


PDSI information maps and timeseries

Map and trends of PDSI. Adapted from Dai et al., 2004 and 2007 IPCC.

Relevant Publications:

  • Dai, A., J. Wang, P.W. Thorne, D.E. Parker, L. Haimberger, and X.L. Wang, 2010: A new approach to homogenize daily radiosonde humidity data. J. Climate, submitted.
  • Dai, A., 2010: Drought under global warming: A review. Wiley Interdisciplinary Reviews: Climate Change, in revision.
  • Trenberth, K. E., 2010: Changes in precipitation with climate change. Climate Research, submitted.
  • Sun, Y., Y. Ding, and A. Dai, 2010: Changing links between South Asian summer monsoon circulation and tropospheric land-sea thermal contrasts under a warming scenario. Geophys. Res. Lett., 37, L02704, doi:10.1029/2009GL041662.
  • Li, H., A. Dai, T. Zhou, and J. Lu, 2010: Response of East Asian summer monsoon to historical SST and atmospheric forcing during 1950-2000. Climate Dynamics, 34, 501-514. doi:10.1007/s00382-008-0482-7.
  • Dai, A., T. Qian, K. E. Trenberth, and J. D Milliman, 2009: Changes in continental freshwater discharge from 1948-2004. J. Climate, 22, 2773–2791.
  • Qian, T., A. Dai, and K. E. Trenberth, 2007: Hydroclimatic trends in the Mississippi river basin from 1948 to 2004. J. Climate, 20, 4599-4614.
  • Sun, Y., S. Solomon, A. Dai, and R. Portmann, 2007: How often will it rain? J. Climate, 20, 4801-4818.
  • Trenberth, K. E. and A. Dai, 2007: Effects of Mount Pinatubo volcanic eruption on the hydrological cycle as an analog of geoengineering. Geophys. Res. Lett., 34, L15702, doi:10.1029/2007GL030524.
  • Trenberth, K. E., L. Smith, T. Qian, A. Dai and J. Fasullo, 2007: Estimates of the global water budget and its annual cycle using observational and model data. J. Hydrometeor, 8, 758-769.
  • Qian, T., A. Dai, K. E. Trenberth, and K. W. Oleson, 2006: Simulation of global land surface conditions from 1948-2004. Part I: Forcing data and evaluation. J. Hydrometeorology, 7, 953-975.
  • Dai, A., 2006: Recent climatology, variability and trends in global surface humidity. J. Climate, 19, 3589–3606.
  • Dai, A., T. R. Karl, B. Sun, and K. E. Trenberth, 2006: Recent trends in cloudiness over the United States: A tale of monitoring inadequacies. Bull. Am. Met. Soc., 87, 597-606.
  • Su, F., J. C. Adam, K. E. Trenberth, D. P. Lettenmaier, 2006: Evaluation of surface water fluxes of the pan-Arctic land region with a land surface model and ERA-40 reanalysis. J. Geophys. Res., 111, D05 110, doi:10.1029/2005JD006387.
  • Dai, A., K. E. Trenberth, and T. Qian, 2004: A global data set of Palmer Drought Severity Index for 1870-2002: Relationship with soil moisture and effects of surface warming. J. Hydrometeorology, 5, 1117-1130.
  • Trenberth, K. E., A. Dai, R. M. Rasmussen, and D. B. Parsons, 2003: The changing character of precipitation. Bull. Am. Met. Soc., 84, 1205-1217.
  • Dai, A. and K.E. Trenberth, 2002: Estimates of Freshwater Discharge from Continents: Latitudinal and Seasonal Variations. J. Hydro., 3, 660-687.
  • Dai, A., T.M.L. Wigley, B.A. Boville, J.T. Kiehl, and L.E. Buja, 2001: Climates of the 20th and 21st centuries simulated by the NCAR Climate System Model. J. Climate, 14, 485-519
  • Dai, A., 2000: .Global precipitation and thunderstorm frequencies. Part I: Seasonal and interannual variations. J. Climate, 14, 1092-1111.
  • Dai, A., 2000: .Global precipitation and thunderstorm frequencies. Part II: Diurnal variations. J. Climate, 14, 1112-1128, 2001.