Land use changes and their impacts on extreme events By Millán M. Millán Conference: Land as a Resource, Brussels 19 June 2014
Atlantic Fronts 20% Decreasing Summer Storms 15% Decreasing Gone Mediterranean Cyclogenesis 65% Increasing and more torrential
Back trajectories (V b ) of the airmasses that fed torrential rains in Germany and the Czech Republic on 11-13 August 2002. (Uwe Ulbrich et al. Weather, 58, 434-443, 2003)
Large scale (weak) subsidence, the non precipitated water vapour and pollutants are advected out of the region To 12+ km Storm: OPEN (i.e., monsoon type) CIRCULATION Air at 315 K & 21 g(h 2 O)/kg(air) 26º C (299 K) 14g (H 2 O)/kg(air) 60 to 100 km Injection To 5+ km Air at 315 K & 20 g(h 2 O)/kg(air) No-storm: CLOSED (i.e., vertical Type) RE-CIRCULATION Return flows under strong (meso-scale) compensatory Subsidence lead to layer formation over the sea 2000 m Strongly confined surface flows 250 m deep 26º C (299 K) 14g (H 2 O)/kg(air)
G LAND-USE & SURFACE CHANGES Alter the MOISTURE, HEAT, & pollutants added to seabreezes * EVAPORATION FROM SEA + Pollution Effects (e.g., nucleation) Loss of summer storms. Drought increases over coastal mountains and other inland areas Cloud Condensation Level rises above coastal mountains Non-precipitated H 2 O vapour & pollutants (O 3 ) follow the return flows aloft, and pile up in a system of layers, 4.5 to 5.5 km deep, over the sea
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4 Average surface pressure for Europe in July hpa 3,5 3 WMB EMB 2,5 2 1,5 1 1-ene 28-mar 23-jun 18-sep 14-dic Total Precipitable Water Column cm
G LAND-USE & SURFACE CHANGES Alter the MOISTURE, HEAT, & pollutants added to seabreezes * EVAPORATION FROM SEA + Pollution Effects (e.g., nucleation) Loss of summer storms. Drought increases over coastal mountains and other inland areas Cloud Condensation Level rises above coastal mountains Combined greenhouse heating additionally increases the Sea Surface Temperature by the end of summer Non-precipitated H 2 O vapour & pollutants (O 3 ) follow the return flows aloft, and pile up in a system of layers, 4.5 to 5.5 km deep, over the sea
DAY 10:30 & NIGHT 22:30
Sea Surface Temperature SST (August 2003)
G LAND-USE & SURFACE CHANGES Alter the MOISTURE, HEAT, & pollutants added to seabreezes * EVAPORATION FROM SEA + Pollution Effects (e.g., nucleation) Loss of summer storms. Drought increases over coastal mountains and other inland areas Cloud Condensation Level rises above coastal mountains Torrential rains over areas surrounding the Mediterranean increase in autumnwinter-spring Combined greenhouse heating additionally increases the Sea Surface Temperature by the end of summer Non-precipitated H 2 O vapour & pollutants (O 3 ) follow the return flows aloft, and pile up in a system of layers, 4.5 to 5.5 km deep, over the sea
G LAND-USE & SURFACE CHANGES Alter the MOISTURE, HEAT, & pollutants added to seabreezes * EVAPORATION FROM SEA + Pollution Effects (e.g., nucleation) Mud floods Augmented soil erosion Loss of summer storms. Drought increases over coastal mountains and other inland areas Cloud Condensation Level rises above coastal mountains Torrential rains over areas surrounding the Mediterranean increase in autumnwinter-spring Combined greenhouse heating additionally increases the Sea Surface Temperature by the end of summer Non-precipitated H 2 O vapour & pollutants (O 3 ) follow the return flows aloft, and pile up in a system of layers, 4.5 to 5.5 km deep, over the sea Aged airmass advected to other regions, in part (daily), or in toto (every 3 to 10 days)
Average water vapour column over the Western Mediterranean Basin in August 2002. The monthly average is equivalent to a 3-to-4 day accumulation cycle. Back trajectories (type V b ) for the 11-13 August 2002 event. From EC Project MICE (Modelling the Impact of Extreme Events, 2001-2003).
G LAND-USE & SURFACE CHANGES Alter the MOISTURE, HEAT, & pollutants added to seabreezes * EVAPORATION FROM SEA + Pollution Effects (e.g., nucleation) Mud floods Augmented soil erosion Loss of summer storms. Drought increases over coastal mountains and other inland areas Cloud Condensation Level rises above coastal mountains (+?) Perturbation to the NAO (North Atlantic Oscillation) Torrential rains over areas surrounding the Mediterranean increase in autumnwinter-spring Combined greenhouse heating additionally increases the Sea Surface Temperature by the end of summer Non-precipitated H 2 O vapour & pollutants (O 3 ) follow the return flows aloft, and pile up in a system of layers, 4.5 to 5.5 km deep, over the sea Increased salty outflow to Atlantic Changes the evaporation precipitation balance in the western basin. Salinity increases in the Mediterranean Sea Aged airmass advected to other regions, in part (daily), or in toto (every 3 to 10 days) European route-v b tracks Summer floods in Central Europe: 1997, 2002, 2005,...
Nature, vol 437/27, October 2005 Inventing an Icon: Hans Joachim Schellnhuber s map of global tipping points in climate change
British Isles & NW Europe: floods in summer; drier cold winters (snow ) G LAND-USE & SURFACE CHANGES Alter the MOISTURE, HEAT, & pollutants added to seabreezes * EVAPORATION FROM SEA + Pollution Effects (e.g., nucleation) Summer drought followed by winter floods in (Atlantic) Southwestern Europe & Northern Africa Mud floods Augmented soil erosion Loss of summer storms. Drought increases over coastal mountains and other inland areas Cloud Condensation Level rises above coastal mountains (+?) Perturbation to the NAO (North Atlantic Oscillation) Torrential rains over areas surrounding the Mediterranean increase in autumnwinter-spring Combined greenhouse heating additionally increases the Sea Surface Temperature by the end of summer Non-precipitated H 2 O vapour & pollutants (O 3 ) follow the return flows aloft, and pile up in a system of layers, 4.5 to 5.5 km deep, over the sea Increased salty outflow to Atlantic Changes the evaporation precipitation balance in the western basin. Salinity increases in the Mediterranean Sea Aged airmass advected to other regions, in part (daily), or in toto (every 3 to 10 days) Perturbations (?) to extra-tropical depressions & hurricanes, in the Western Atlantic South- Eastern USA Condensation nuclei transported across Atlantic to Caribbean Heterogeneous reactions in shallow clouds: sulphatation and nitrification of Saharan dust African routes: central and/or Southern Atlas (with vertical recirculations) European route-v b tracks Summer floods in Central Europe: 1997, 2002, 2005,...
SUMMARY I In Europe, there are two different hydrological regimes corresponding to the Atlantic and the Mediterranean Catchment Basins On the Atlantic side, from 100% to 80% of precipitation originates from water evaporated in the ocean. Land-use (soil-vegetation-atmosphere) plays a role in the inland propagation of the frontal systems. On the Mediterranean side, from 80% to 100% of precipitation is from water RECYCLED within the Mediterranean Basin itself. Here, soil and vegetation provide a fundamental water pumping mechanism to maintain the stability of the precipitation and the hydrological cycles. Drought and torrential rains in the Mediterranean are the result of a series of concatenated meteorological processes initiated by land use changes at the local scale. The effects of local land-use changes are cumulative, and their perturbations can propagate up to the regional-and-continental scales through the development of WATER VAPOUR ACCUMULATION MODES over the inland seas.
SUMMARY II These processes can lead to intense precipitation events and summer floods along the European Continental-water Divide and other parts of the Mediterranean Catchment Basin, including the islands. Moreover, through the intensification of the Atlantic-Mediterranean Salinity Valve at Gibraltar, the North Atlantic Oscillation can be perturbed and affect precipitation on the European Atlantic side. Therefore, the perturbations initiated by land-use changes at the local level in the Mediterranean may propagate their effects, and produce extreme events, in other parts of Europe. SOLUTIONS There are solutions for recovering the hydrological system, e.g., cultivating summer storms, which can be economically attractive and help to create jobs. But they require a fundamental knowledge of the mechanisms involved, and very, very well-coordinated remedial actions from the local-to-regional scales.
MANY THANKS FOR YOUR ATTENTION!