Changes in Future Seasonal Total Precipitation

This tool is excerpted from Chesapeake Bay Watershed Climate Impacts Summary and Outlook for Spring 2019.

Key Findings

  • All future time periods and emissions scenarios show increases in seasonal total precipitation in the winter, spring and summer across the Chesapeake Bay watershed.
  • Winter precipitation could increase by 1.2 inches in the Chesapeake Bay Watershed by the end of the century. Combined with projected changes in spring precipitation, heightened winter precipitation could lead to more dramatic spring flooding as snow melts and spring precipitation increase simultaneously.
  • Variability in future precipitation projections across the CMIP5 model ensemble is generally much greater than the average projected change, which is a limitation of model results.

How To Use the Tool

Selecting future time periods and emissions scenarios:
Use the slider to adjust the future time period used to calculate the projected change in precipitation. For each time period, the user can also select a future greenhouse gas emissions scenario under Future Emissions Scenario by selecting Moderate Emissions future, Representative Concentration Pathway (RCP) 4.51, or a High Emissions future, RCP 8.5.2

Filtering by geography:
Using the dropdown menu, select a geographic level—the entire watershed, state, county or municipality. A list of states, counties or municipalities will appear, and individual locations can then be selected.

Technical Notes

LOCA or Localized Constructed Analogs is a downscaled climate data product available at 1/16thdegree (6 km) resolution over the continental United States. LOCA datasets include the 32 climate models available in the CMIP5 archive, for two future greenhouse gas concentration trajectories – RCP 4.5 and RCP8.5. For this study, we utilized LOCA data over the Chesapeake Bay watershed from 1976-2095. Access LOCA datasets and learn more about the methodology.

Seasonal total precipitation was determined for each season by summing all daily precipitation events that occurred for each three-month season. We calculated seasonal total precipitation for each season for each year and the averaged values for each season across 30-year periods – 1976-2005, 2006-2035, 2036-2065, 2066-2095 for LOCA data for both RCP 4.5 and RCP 8.5 and 1976-2005, 2006-2017 for ChesWx data. To average across climate models for each grid cell in the LOCA dataset, we employed a weighted average provided by the Northeast Regional Climate Center. Both LOCA and ChesWx datasets were masked to the boundaries of the Chesapeake Bay watershed before calculating seasonal precipitation values and the spatial resolution of each dataset was preserved. Winter is defined as December, January and February. Spring is defined as March, April and May. Summer is defined as June, July and August. Fall is defined as September, October and November.


  1. More information on RCP 4.5 can be found in: Thomson, A.M., Calvin, K.V., Smith, S.J. et al. Climatic Change (2011) 109: 77. Return to text ⤴

  2. More information on RCP 8.5 can be found in: Riahi, K., Rao, S., Krey, V. et al. Climatic Change (2011) 109: 33. Return to text ⤴

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