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Tom Pugh

Thomas Pugh

Senior lecturer

Tom Pugh

Reconciling precipitation with runoff : Observed hydrological change in the midlatitudes

Author

  • Joe M. Osborne
  • F. Hugo Lambert
  • Margriet Groenendijk
  • Anna B. Harper
  • Charles D. Koven
  • Benjamin Poulter
  • Thomas A.M. Pugh
  • Stephen Sitch
  • Benjamin D. Stocker
  • Andy Wiltshire
  • Sönke Zaehle
Show all

Summary, in English

Century-long observed gridded land precipitation datasets are a cornerstone of hydrometeorological research. But recent work has suggested that observed Northern Hemisphere midlatitude (NHML) land mean precipitation does not show evidence of an expected negative response to mid-twentieth-century aerosol forcing. Utilizing observed river discharges, the observed runoff is calculated and compared with observed land precipitation. The results show a near-zero twentieth-century trend in observed NHML land mean runoff, in contrast to the significant positive trend in observed NHML land mean precipitation. However, precipitation and runoff share common interannual and decadal variability. An obvious split, or breakpoint, is found in the NHML land mean runoff-precipitation relationship in the 1930s. Using runoff simulated by six land surface models (LSMs), which are driven by the observed precipitation dataset, such breakpoints are absent. These findings support previous hypotheses that inhomogeneities exist in the early-twentieth-century NHML land mean precipitation record. Adjusting the observed precipitation record according to the observed runoff record largely accounts for the departure of the observed precipitation response from that predicted given the real-world aerosol forcing estimate, more than halving the discrepancy from about 6 to around 2 W m-2. Consideration of complementary observed runoff adds support to the suggestion that NHML-wide early-twentieth-century precipitation observations are unsuitable for climate change studies. The agreement between precipitation and runoff over Europe, however, is excellent, supporting the use of whole-twentieth-century observed precipitation datasets here.

Publishing year

2015

Language

English

Pages

2403-2420

Publication/Series

Journal of Hydrometeorology

Volume

16

Issue

6

Document type

Journal article

Publisher

American Meteorological Society

Topic

  • Environmental Sciences

Keywords

  • Atm/Ocean Structure/ Phenomena
  • Changepoint analysis
  • Climate variability
  • Geographic location/entity
  • Land surface
  • Land surface model
  • Mathematical and statistical techniques
  • Models and modeling
  • Precipitation
  • Runoff
  • Variability

Status

Published

ISBN/ISSN/Other

  • ISSN: 1525-755X