sixième réunion des utilisateurs de méso-nh, toulouse, 13-14 octobre 2011

Rui Salgado 1Réunion Méso-NH Octobre 2011

l'impact de la représentation des lacs dans des simulations Meso-NH

Rui SalgadoCentro de Geofísica de Évora

Universidade de Évora

Sixième réunion des utilisateurs de Méso-NH, Toulouse, 13-14 octobre 2011


Summary

How important are the representation of lakes (NWP)

Flake: initial conditions and parameters

3D simulation Meso-NH – Surfex – FLake

Impact of the FLake on the flow over a lake (Alqueva)

THUMEX (Radiation measures)


How important is the lake representation in NWP (example)

Sensitivity of 48-hour near surface temperature forecast (LAKE – NOLAKE) - Sets of 10-day forecasts covering one full year (1988) at 50 km resolution with the operational IFS. Two experiments were performed with (LAKE) and without (NOLAKE) FLake activated.

Balsamo, G., R. Salgado, E. Dutra, S. Boussetta, T. Stockdale, M. Potes, (2011). ECMWF Tech. memo 648.

SONJJA


Impact of FLake on NWP (IFS)

Impact of 48-hour T2m forecasts (valid at 00 UTC) for LAKE compared to

NOLAKE,verified against the ECMWF T2m

analysis: Mean Absolute Error difference for JJA 2008.

Negative values indicate an improvement (MAE reduction)

A positive impact in spring and summer particularly over the North American lakes region and the European large lakes areas. In Winter, deteriorates T2m over central Canada while it improves in the eastern North America In Autumn the impact is milder, with improvement over Scandinavia Overall the impact is positive


FLake in NWP models

FLake

SurfexFlake is implemented:Regional weather forecast of

the German weather service (operational after 2010)

UK-MetOffice (Rooney et al 2010)

Swedish Meteorological and Hydrological Institute(Samuelson, 2010)

ECMWF (IFS)SURFEX

The performance of FLake was evaluated during the Lake Model Intercomparison Project (Lake-MIP, Stepanenko et al. 2010)

FLake: Fresh-water Lake model FLake (Mironov et al. 2010) Two-layer parametric representation of the evolving temperature profile integral budgets of heat and kinetic energy. The thermocline is described using the concept of self-similarity (assumed shape) of the temperature profile.


Flake: Initialization

The use of the FLake lake model inside an weather forecast system requires the knowledge of some parameters and the initial conditions of its variables.

Parameters: Depth Extinction coefficient of solar radiation in water Water surface radiative proprieties (albedos, emissivity)

Lake variables are currently not treated by the data assimilation systems.

One possible solution is to create a climate of FLake variables from off-line long periods simulations


Global lake depth data base

Lake depth is a crucial field controlling the water body thermal capacity, as demonstrated by many authors

lake depth dataprovided by Kourzeneva

et al. (2010)30sec arc resolution


Climatologies for cold start simulations

Example

Climatological lake mixed-layer temperature

(a) winter (DJF)

(b) spring (MAM)(c) summer (JJA)(d) autumn (SON)

generated by theLake-planet experience:

Off-line simulation with HTESSEL+FLake Lakes overall (lake fraction = 1 over all grid points) Forcing: ERA-Interim reanalysis 1989 – 2009 N128 resolution (~80km)


3D simulation Configuration

Avec grid-nesting(Two way)

South-East of PortugalAlqueva artificial lake

Rui Salgado 10

Réunion Méso-NH Octobre 2011

3D simulation Configuration

Simulation Period 16/July/2007, 30 hours, beginning at 18 TU

Vertical levels 45 stretched levels; 1º at 10m up to 25 km

Physical parameterizations:

Explicit clouds and precipitation Kessler warm microphysical

Boundary Layer TKE equation BL,1989

Convection Deep (model1)EDKF Shallow (all models)

Data bases for surface Ecoclimap, FAO, GTOPO30

Radiation ECMWF radiative scheme

Initial and forcing fields ECMWF analysis (6 hours)

Surface processes SURFEX with and without FLake

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3D Simulation Initial Conditions and parameters

TMNW T_BOT T_B1 H_ml H_b1 TS 289.27 285.42 282.25 4.36 0.78 298.04

15/07/2007 18:00 Alqueva field campaign Summer 2007

Lake depth: 40mExtinction coefficient: 3.5m

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improve T2m

Mean values over lake

Rui Salgado 13


improve surface fluxes

Rui Salgado 14


Effect on T2m Hu2m and wind near surface horizontal fields

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Boundary layer

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The use of the FLake lake model inside an weather forecast system requires the knowledge of some parameters and the initial conditions of its variables.

Parameters: Depth Extinction coefficient of solar radiation in water Water surface radiative proprieties (albedos,

emissivity)

Lake variables are currently not treated by the data assimilation systems.

One possible solution is to create a climate of FLake variables from off-line long periods simulations

Rui Salgado 17


THAUMEX field campaign

measurement of spectral radiative flux at several levels

estimation of the Extinction coefficient (spectral)

POI 24 August

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THAUMEX field campaign

Reflectance spectral

POI 24 August

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Conclusions

The effects of the implementation of FLake are visible on mesoscale short-range simulations:

in the case studied, the impact of T2m > 2ºC it improves the representation of surface fluxes of sensible

heat, latent heat and momentum the effects are manly concentrated over the lake The effect on the circulation is weak, but still visible

ongoing work explore THAUMEX data – obtain extinction coefficient

sixième réunion des utilisateurs de méso-nh, toulouse, 13-14 octobre 2011

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