Water and energy budget over the Mediterranean Sea, East-West differences(M-Atlas)AOSC 658NMartina RickoDec 5, 2007

Introduction:Many studies have been focused over the Mediterranean area:

Present and past precipitation and temperature variability, large scale dynamics and trends in the Mediterranean (Xoplaki, et al 2004), -- Mediterranean summer air temperature variability and its connection to the large scale atmospheric circulation and SSTs (Xoplaki, et al 2003)Mediterranean climate variability (Lionello, et al 2006)The energy and water budgets of the Mediterranean Sea (Pinardi and Masetti 2000)River discharge into the Mediterranean Sea: Climatology and aspects of the observed variability (Struglia, et al 2004)Ocean processes in climate dynamics: global and Mediterranean examples (Malanotte-Rizzoli, 1994)Influenced by teleconnections with some major climate variability modes:- - Correlation between ENSO and Western Mediterranean precipitation with opposite signs in autumn and in spring and varying at the multidecadal time scale (Rodo et al, 1997; Mariotti et al, 2002; Park, 2004; Brnnimann et al, 2007, ).- - Mechanism involving partly the atmospheric bridge between tropical Pacific and Atlantic, the perturbation of the Atlantic Walker and Hadley circulation and the propagation of the signal through stationary Rossby waves and transient eddies (Rodo, 2001; Cassou, 2001; Mariotti et al, 2005, ).-- Correlation between NAO and Mediterranean precipitation with negative (positive) anomalies for positive (negative) phase of the oscillation (Hurrell et al, 2003).-- Mechanism involving the northward (southward) shift of the storm track during the positive (negative) phases of the oscillation (Hurrell et al, 2003).--Correlation between the semi-permanent subsidence structure over the Eastern Mediterranean and the onset of the Asian Monsoon. Mechanism involving a Rossby wave propagating northwestward from the monsoon region (Rodwell and Hoskins, 1996; Ziv et al, 2004; ).-- Correlation between hot summers in the Mediterranean and the monsoon regime over West Africa. Mechanism involving moisture transport and meridional thermal contrast (Rowell, 2003;)

Questions/Objectives:Documenting the components of the hydrological cycle over the Mediterranean (P, E, E-P, SST, S, etc.)

Estimation and understanding of the interannual variability

The Variations of the components (time series of anomalies, annual cycles)

Detection of the trends

East/West Mediterranean Basin differences

Evaporation-Salinity connection over the East Mediterranean

Data:GPCP: 1979-2004, monthly, (2.5x2.5), 1 levelCMAP2:1979-2006, monthly, (2.5x2.5), 1 levelCRU: 1979-2001, monthly, (0.5x0.5), 1 levelERA40: 1958-2001, monthly, (2.5x2.5), 23 levelsOAFlux (Objectively Analyzed Air-Sea Fluxes for the Global Oceans): 1981-2002, monthly, (1x1), 1 levelQuikScat: 1999-2006, monthly, (1x1), 1 levelISCCP radiation: 1984-2004, monthly, (2.5x2.5), 1 levelGRDC (Global Runoff Data Center, UNH): Climatology (1807-1991)HadSST: 1901-2003, monthly, (1x1), 1 levelReynolds SST: 1981-2005, monthly, (1x1), 1 levelMedAtlas: Climatology (2002), (0.2x0.2), 25 levelsLevitus94: Climatology (1994), (1x1), 19 levelsWOA05: Climatology (2005), (1x1), 24 levelsSODA1.4.2: 1958-2001, monthly, (0.5x0.5), 40 levels

new GODAS! New River discharge data NCAR (Trenberth, Dai), monthly

Climatological mean precipitation and evaporation from ERA40 (1979-1999). Amplitude and phase (1st harmonic), contours are mean annual cycle in mm/day.

Climatological mean Hadley SST and Medatlas Salinity. Amplitude and phase (1st harmonic), contours are mean annual cycle in deg C.

Clim: Precipitation (mm/day) ERA40 (58-01)

P over the sea: Direct measurements: complex and rare Use of reanalysis helps No validation and/or low resolution data over sea Strong variability

Clim: Evaporation (mm/day) ERA40 (58-01) E over the sea: Leading term of the water budget variability Very few measurements Low resolution and low quality of the current database Problem with physical parametrizations: low confidence in the reanalysis estimations

Clim: E-P (mm/day) ERA40 (58-01) Motivations for E-P Climate Change: Strong impact of the climate change on E-P-R (E increases, P and R decrease) large uncertainties (Somot et al, 2006) E-P-R is a key term of the Medit. Slow water cycle it drives the dense water formation process

Brown=divergence, green=convergenceClim: Vertically integrated Moisture Flux (1000-300 hPa) ERA40 (58-01) Atmospheric humidity convergence:Difficult to compute (non-linearity, non conservative in reanalysis, high temporal and spatial variability, complex Med catchment limit)External influences: NAO, African and Indian monsoonImpact of the air-sea coupling

Clim: Runoff GRDC (58-01) River runoff fluxes:Large uncertainties in the modelsLocal and global impact on the Med sea hydrologyTotal runoff (mm/mo)

Clim: MSLP (hPa) ERA40 and QuikScat sfc winds (m/s) - More northward westerlies during summer, descending branch of the Hadley circulation the influence of the westerlies over Med during winter

Clim SST and S MedAtlas sfc level

ISCCP (84-04) Net SW radiation (W/m2)

ISCCP (84-04) Net radiation=SWd-SWu+LWd-LWu (W/m2)Positive radiation budget low albedo of the sea

Why do we need air-sea heat fluxes?

The atmosphere interacts with the ocean through the exchange of heat, fresh water, and momentum at the air-sea interface. The air-sea heat exchange includes a number of processes: solar radiation, longwave radiation, sensible heat transfer by conduction and convection, and latent heat release by evaporation of sea surface water. The amount of heat exchange resulting from these radiative and turbulent heat transfer processes is called air-sea heat flux.

ERA40 clim (79-01)OAFlux clim (81-02)

OAFlux clim (81-02)ERA40 clim (79-01)

The water budgetTerms of the Mediterranean Water Budget:Atmosphere-land-hydrology-sea interactionLocal cycle under global influence (atmosphere, ocean)Non regular Mediterranean river catchment

Solar and latent heat fluxes are dominantWeak net heat fluxSignificant seasonal variabilitiesWater budgetHeat budgetImportant E values (leading term of the buoyancy), poorly known!Large seasonal variability of E; long term trend???Great differences due to the source data, to their resolution, to their variabilityHymex Wokshop, Tolouse, 2007, January, 9-11th, G. Caniaux, L. Prieur, H. Giordani

Med. Atmospheric water budgetP+MFD=E

Era40 79-01 (m2/s2)/100 QuikScat 00-06wind (m/s)

0m5 m

P (1979-2001), 4 seasons of seasonally-averaged time seriesr(cmap/era)=0.961r(gpcp/era)=0.967 r(cmap/gpcp)=0.996r(cmap/era)=0.881r(gpcp/era)=0.864r(cmap/gpcp)=0.972r(cmap/era)=0.940r(gpcp/era)=0.915 r(cmap/gpcp)=0.973r(cmap/era)=0.944r(gpcp/era)=0.916r(cmap/gpcp)=0.973r(95%sl) = 0.43

E (1979-2001), 4 seasons of seasonally-averaged time seriesr(oaflux/era)=0.923r(oaflux/era)=0.763r(oaflux/era)=0.849r(oaflux/era)=0.918r(95%sl) = 0.43

E-P (1981-2001), 4 seasons of seasonally-averaged time seriesr(oaf-cmap/era)=0.841r(oaf-gpcp/era)=0.843 r(oaf-cmap/oaf-gpcp)=0.981r(oaf-cmap/era)=0.916r(oaf-gpcp/era)=0.932r(oaf-cmap/oaf-gpcp)=0.997r(oaf-cmap/era)=0.785r(oaf-gpcp/era)=0.798r(oaf-cmap/oaf-gpcp)=0.989r(oaf-cmap/era)=0.704r(oaf-gpcp/era)=0.716r(oaf-cmap/oaf-gpcp)=0.990r(95%sl) = 0.43

Hadley SST (1901-2003), seasonally-averaged time series SODA S (1979-2001), seasonally-averaged time series, 5m

Hadley SST (1901-2003), 4 seasons of seasonally-averaged time series

S (1979-2001), 4 seasons of seasonally-averaged time series

DJF Trends

MAM Trends

JJA Trends

SON Trends

E / W Med!!!!Atmospheric water balance!

Spatial correlations between GPCP precipitation and local Hadley SST (1979-99) - based on monthly data (Lag referred to SST) R(95%sl) = 0.25

Spatial correlations between GPCP precipitation and local SODA Salinity (1979-01) - based on monthly data (Lag referred to S)R(95%sl) = 0.24

Spatial correlations between GPCP precipitation and local SODA Salinity (1979-01) - based on monthly data (Lag=-1 referred to S)R(95%sl) = 0.24Lag = -1S FMA with P MAMS MJJ with P JJAS ASO with P SON

Spatial correlations between OAFlux evaporation and local SODA Salinity (1981-01) - based on monthly data (Lag referred to S)R(95%sl) = 0.25

Negative corr b/w SST and P => atmosphere is forcing ocean!PSE, SSTE Med (JJA, SON)W Med E Med (DJF, MAM)Positive corr b/w SST and P => ocean is forcing atmosphere!

Contributions/Conclusions:Comprehensive view of hydrological components over the Med (new data)The connection between the anomalies - an evolution of the anomalies in last decades shows strong signal of recent climate change!East/West Mediterranean basin differences - understanding the mechanisms of the hydrological components (ocean-atmosphere interaction) and ocean thermohaline circulationThe role of salinity has been neglected until recently (the historical lack of observations and predictive skill enabled by wind forcing and subsurface temperature observations)The relative importance of SSS in the context of understanding the mechanismsThe impact of the Mediterranean ocean-atmosphere coupling is dominant at the regional scale and significant at the global scale. Mediterranean Sea is an important point of interest (local, regional, global), with a teleconnection with the general atmospheric circulation

The first preliminary results a comparison of new available data, a new method of analyzing anomalies, trends and differences in the east/west Mediterranean with the mechanism explanations!