the climate change connection: forced and natural · dryland areas based on observational data. a...
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Sustainability of Engineered Rivers in Arid Lands, 2014
Gerald R. NorthDepartment of Atmospheric Sciences
Texas A&M [email protected]
Welcome to Texas!
The Climate Change Connection:
Forced and Natural
New York Times, Jan 6, 2014
To help the Colorado, federal authorities this year will for the first time reduce the water flow into Lake Mead, the nation’s largest reservoir, created by Hoover Dam.
New York Times, Jan 6, 2014
Not a surprise to this audience:
Anthropogenic Global Warming is Real and it is Serious
Water Availability may be the most Serious Consequence
Ten Year Climatology from Tropical Rainfall Measuring Mission (TRMM)
Climate Change: The arid
subtropics will expand
Hadley Cells will expand, storm belts recede
IPCC #5 (2013) future Climate Change
Note the funny but useful scale of the contours
Closer look at Precipitation
Present Drylands:
Dry subhumidSemiaridAridHyper-arid
Climatology 1961-1990
Feng & Fu, 2013
Temporal variations in areal coverage of global drylandsfor (a) the total and individual components of (b) dry subhumid, (c) semiarid, (d) arid, and (e) hyper-arid regions, in units of 106 km2. Thick black (blue) lines are the ensemble average of the 27 models from historical/RCP8.5 (RCP4.5) simulations. Dotted lineshows the climatology of 1961–1990. The grey shading denotes one standard deviation of the 27 models from historical/RCP8.5 simulations. Red lines are for dryland areas based on observational data. A 15 yr running smoothing was applied to emphasize the climatechange.
Feng & Fu, 2013
Temporal variations of annual mean (a) surface air temperature, (b) precipitation, and (c) PET, averaged over land between 60 N and 60 S, and (d) total area of global drylands. Thick black (blue) lines are the ensemble average of the 27 models from historical/RCP8.5 (RCP4.5) simulations. Dotted line shows the climatologyof 1961–1990. The grey shading denotes one standard deviationof the 27 models from historical/RCP8.5 simulations. In (a) and(b), the observations from CPC (UD) data are shown as red (green dashed) lines. In (c) and (d), the observational results from combinations of UD or CPC, with 20CR or GLDAS indicate that the temperature and precipitation are from UD or CPC, and the solarradiation, humid and wind speed are from the 20th century Feng & Fu, 2013
(a) Projected changes in coverage to drier types for 2071–2100 under scenario RCP8.5 relative to 1961–1990, based on the ensemble average of the 27 models.
Feng & Fu, 2013
[email protected] Expand!
Projected changes in coverage to wetter types for 2071–2100 under scenario RCP8.5 relative to 1961–1990, based on the ensemble average of the 27 models
Feng & Fu, 2013
projected area changes to drier types where more than 80% of the 27 models agree on the sign.
Feng & Fu, 2013
Projected changes in (a) surface air temperature (C), (b) PET (%), (c) precipitation (%), and (d) P / PET for 2071–2100 relative to 1961–1990 under scenario RCP85 from 27 climate models. Grid points are stippled where more than 80% of these models agree on the sign.
Feng & Fu, [email protected]
Feng & Fu, [email protected]
Feng & Fu, [email protected]
Feng & Fu, [email protected]
Feng & Fu, [email protected]
Contributions of (a) precipitation and (b) PET to (c) projected changes in P / PET for 2071–2100 relative to 1961–1990 under scenario RCP85 from 27 climate models. Grid points are stippledwhere more than 80% of these models agree on the sign.
Feng & Fu, [email protected]
Feng & Fu, [email protected]
Feng & Fu, [email protected]
Feng & Fu, [email protected]
Another Concern:
Do the Eastward Winds Weaken in the midlatitude storm belts? And what does that mean about orographicrainfall?
Trends in streamflow timing and volume in the Pacific Northwest United States have been attributed to increased temperatures, because trends in precipitation at lower-elevation stations were negligible. We demonstrate that observed streamflow declines are probably associated with declines in mountain precipitation, revealing previously unexplored differential trends. Lower-troposphere winter (November to March) westerlies are strongly correlated with high-elevation precipitation but weakly correlated with low-elevation precipitation. Decreases in lower-tropospheric winter westerlies across the region from 1950 to 2012 are hypothesized to have reduced orographic precipitation enhancement, yielding differential trends in precipitationacross elevations and contributing to the decline in annual streamflow. Climate projections show weakened lower-troposphere zonal flow across the region under enhanced greenhouse forcing, highlighting an additional stressor that is relevant for climate change impacts on hydrology.
Abstract:
Correlation of 1982–2012 November to March HCN (circles) and SNOTEL (squares) precipitation with November to March u700 zonal winds over 42.5° to 47.5°N and 115° to 130°W. Three longitudinal transects (lower panels) show examples of the pattern of correlations with elevation. The larger symbols indicate statistical significance (P < 10%).
Westerly winds are correlated with Precipitation
Data suggest that zonal wind speed is decreasing in the US NW.
Upper-quartile (green), lower-quartile (red), and mean (black) trends in November to March u700 zonal winds averaged over 42.5° to 47.5°N and 115° to 130°W. Only the mean and lower quartile trends are significant (P = 0.03 and 0.02, respectively). Also shown with a diamond and bar centered on 1981 are the unconditional quartiles. CMIP5 projections for future wind speeds were calculated from modeled changes between 1950-2005 and 2071-2100 added to the observed 1950–2005 mean (blue bar on right). Estimates for each model are shown as black dots on the right. The mean projection is shown with a black bar.
Natural Climate Variability due toENSO, North Atlantic Oscillation(NAO), PDO, etc.
Many of these affect the rivers we are considering.
ENSO(El Nino/Southern Oscillation)
ENSO Teleconnections: NH Winter, SH Summer halves
ENSO Teleconnections: NH Summer, SH Winter halves
North Atlantic Oscillation (NAO):
https://climatedataguide.ucar.edu/climate-data/hurrell-north-atlantic-oscillation-nao-index-station-based
Middle East precipitation with selected Turkish temperature (23 small dark circles) and precipitation stations (27 large white circles); stations with less than 30 years of data or any incomplete DJFM series were omitted (Baker et al., 1995). Tigris and Euphrates River streamflow measurement stations in Keban, Turkey and Baghdad, Iraq are depicted with star symbols (Vorosmartyet al., 1996) (Cullen & deMenocal, Int. J. Climatology, 20, 853-863, 2000)
Tigris/Euphrates: Example of NAO interaction
Cullen & deMenocal, 2000
(a) The North Atlantic Oscillation sea level pressure index (NAO SLP, 1864–1995) defined by Hurrell(1995); (b) spatial correlation between the NAOSLP index and mean winter (DJFM) station temperature; and (c) spatial correlation between theNAOSLP index and mean winter station precipitation
Winter Temperature and Precipitation are Correlated with the NAO index.
Tigris/Euphrates example
Monthly Euphrates River streamflow (solid line) measured at Keban, Turkey (35-year mean). Monthly averages for the three lowest NAO years (1940, 1963 and 1969; dashed line with filled circles, 2s S.D. shown), and monthly averages of the threehighest years (1945, 1949 and 1961; dashed line with triangles, 2s S.D. shown)
Cullen & deMenocal, 2000Tigris/Euphrates example
Evidence of impacts from rising temperature on inflows to the Murray-Darling BasinWenju Cai and Tim Cowan
GEOPHYSICAL RESEARCH LETTERS, VOL. 35, L07701, doi:10.1029/2008GL033390, 2008
Two known large-scale climate drivers affecting rainfall variability over the MDB are the Indian Ocean Dipole (IOD) [Saji et al., 1999; Cai et al., 2005] and El Nin ̃o -Southern Oscillation (ENSO) [Nicholls et al., 1996]. The impact of ENSO occurs mainly in JJA and SON with anomalously low rainfall over the MDB during an El Nin ̃o event; the IOD mainly influences SON rainfall such that when the sea surface temperature (SST) in the eastern pole is anomalously low, MDB rainfall decreases. A correlation of SSTs and MDB rainfall with inflow for each season (not shown) clearly shows these influences.
Global Warming Signal
ENSO Connections:
Pacific Decadal Oscillation (PDO)
Mantua & Hare, 2002: The PDO, J. Oceanog.
Mantua & Hare, 2002: The PDO, J. Oceanog.
Summary• Global Warming increases T & PET everywhere
•Drylands: expect increase 10% globally• GW also causes expansion of the Hadley Cells
•With consequences for subtropics, midlatitudes•Storm belts tend to move polewards
• Are the Eastward Mid-Latitude winds weakening?•With consequences for Western Slope Rainfall
• Natural variability in the form of NAO, ENSO, PDO play significant roles in stream flows
• Monsoons are tricky, but some indications are good for tropical and subtropical lands