L.S.P.M. Land Surface Process Model, Cassardo et al 1995

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Processi di interazione nello strato limite
superficiale l'esempio dell'estate 2003 e
l'esempio del monsone asiatico
Prof. Claudio Cassardo Department of General
Physics University of Torino, Italy E-mail
cassardo_at_ph.unito.it, Web http//www.ph.unito.it/
?cassardo/
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Summary

• 1. General description of the LSPM
• 2. Simulations during the 2003 summer
• 3. Simulations over the Asian monsoon in Korea

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1. General description of the model
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The LSPM (Land Surface Process Model)
The LSPM is a 1D model which calculates energy,
momentum and water exchanges between atmosphere
and land The processes in LSPM are described in
terms of physical fluxes and hydrological state
of the land
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LSPM structure

• Three main zones atmosphere, vegetation and soil
• Canopy is considered as an uniform layer
  (big-leaf approximation)
• All variables are calculated as weighted averages
  between atmospheric, canopy and snow components
• Turbulent fluxes are calculated by using the
  analogue electric scheme
• Soil temperature and moisture are calculated
  using multi-layer schemes
• User can select a variable number of soil layers
• LSPM can evaluate the thermal and hydrological
  budget in soil, canopy, snow and in atmosphere

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LSPM parameters

• In the atmospheric layer, all variables are
  calculated as weighted averages between
  atmospheric and canopy components
• Canopy is characterised by
• vegetation cover, height, leaf area index (LAI),
  albedo, minimum stomatal resistance, leaf
  dimension, emissivity and root depth
• Soil temperature and moisture are calculated
  using multi-layer schemes, whose main parameters
  are
• thermal conductivity, hydraulic conductivity,
  soil porosity, permanent wilting point, dry
  volumetric heat capacity, soil surface albedo and
  emissivity

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Physical processes

• The physical processes
• Radiative fluxes
• Momentum flux
• Sensible and latent heat fluxes
• Partitioning of latent heat into canopy
  evaporation, soil evaporation and transpiration
• Heat transfer in a multi-layer soil or lake

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Hydrological processes

• The hydrological processes
• Snow accumulation and melt
• Rainfall, interception, infiltration and runoff
• Soil hydrology, including water transfer in a
  multi-layer soil

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THE RADIATIVE BALANCE
The radiative fluxes include absorption,
reflection and transmittance of solar radiation
and absorption and emission of longwave
radiation. They are critical for the surface
energy balance. The surface energy balance,
expressed in W/m2, is
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The hydrological balance
In the mesoscale modeling the local balance is
important ? storage of water into terrain The
hydrological balance is given by
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The turbulent heat fluxes in the surface layer
A flux Fx of the generic variable x in the
surface layer can be described by the
flux-gradient equation
The coefficient Kx represents the ability of the
process in the transfer of the variable x
The above equation can be integrated. The flux Fx
can be considered constant in the surface layer.
The result is an equation similar to the Ohm law
gradient Flux -------------
resistance
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Latent Heat flux for Vegetated Surface

• In the more complicated case of a vegetated
  surface, ?E is partitioned into vegetation and
  ground fluxes that depend on vegetation qv and
  ground qg humidities or partial vapour pressures
• Assuming that the canopy has negligible capacity
  to store water vapour, the latent heat flux ?E
  between the surface at height z0wd and the
  atmosphere at height zatm is partitioned into
  vegetation and ground fluxes as

L and S are the leaf and stem area indices. rb
is the average leaf boundary layer resistance
(sm-1) and r0h is the aerodynamic resistance
(sm-1) between the ground (z0h) and dz0h. rs is
the stomatal resistance (sm-1).
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2. Simulations during the 2003 summer
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Lanomalia di temperatura
Giugno, luglio ed agosto 2003 sono stati i mesi
più caldi mai registrati in Europa
centroccidentale sono stati stabiliti in molti
paesi (Portogallo, Germania, Svizzera,
Gran-Bretagna) i record nazionali di temperatura
massima e in molte stazioni quelli di temperatura
massima giornaliera estiva

• I valori rientrano nel range 3-6C, con il
  massimo sulla Francia e sulla regione alpina
• Paragonata con la statistica del periodo 1961-90,
  questanomalia corrisponde a 5s

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È stata unanomalia solo europea!!!

• Diagrammi di Hovmoller dellanomalia termica a
  850 hPa rispetto al periodo (19722001) delle
  analisi ERA-40 mediate sul rettangolo 35N60N
  nel mese di agosto. Isolinee ogni 2C. Sono
  evidenziate le regioni con anomalie superiori a
  4C

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La stazione di Torino

• Negli ultimi 200 anni si sono verificati almeno
  una dozzina di anomalie (rispetto al periodo
  1961-90) dellordine di 2C
• Nellestate 2003, lanomalia è stata 5.3 C

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Bilancio energetico a Torino

• Simulazione eseguita con LSPM sul periodo
  1999-2003 su due stazioni Torino ed Alessandria
• A Torino la radiazione globale, molto alta nel
  periodo marzo-settembre, nellestate 2003 è stata
  circa 50 W/m2 superiore alla norma
• La radiazione netta è stata circa 25 W/m2
  superiore alla norma

• Il flusso di calore latente è stato inferiore
  alla norma a luglio, quasi normale negli altri
  mesi
• Il flusso aria-vegetazione-suolo è stato normale
• Il flusso di calore sensibile è stato 45 W/m2
  superiore alla norma

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Andamenti di alcune grandezze
Radiazione solare (Wm2)
Precipitazione cumulata (mm)
Flusso di calore sensibile (Wm2)
Flusso di calore latente (W/m2)
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Andamenti di alcune grandezze
Rateo di evaporazione (mm)
Temperatura del primo strato di suolo (C)

• Conclusioni
• Riscaldamento prodotto da due cause
• Moti subsidenti (riscaldamento adiabatico)
• Suolo troppo secco per consentire unadeguata
  evapotraspirazione ? solo flusso di calore
  sensibile ? surriscaldamento (effetto
  quantificato in 2C circa su Torino, e non
  presente sul Piemonte orientale)

Umidità del primo strato di suolo
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3. Simulations over the Asian monsoon in Korea
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The East Asian monsoon

• The East Asian monsoon, known as jangma ( )
  in Korea and bai-u or shurin in Japan, is
  characterized by southwesterly winds in late June
  to water the Korean peninsula and Japan, leading
  to reliable precipitation spikes in July and
  August, and daytime T gt 32C with dew-points gt
  24C
• Over Japan and Korea, the monsoon boundary
  typically has the form of a quasi-stationary
  front separating cooler air mass associated with
  the Okhotsk High (to the North) from hot, humid
  air mass associated with subtropical ridge (to
  the South)

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Description of the experiment

• Source data 900 stations from Korean
  Meteorological Administration (KMA)
• Input data temperature, pressure and humidity,
  wind speed, precipitation, solar radiation

• Period 2005 summer
• This period has been selected as the rainy season
  has been relatively intense if compared with
  other seasons

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Sensible heat flux (Wm-2)

• SHF is larger in the urban area of Seoul and over
  the great island of Jeju and in the extreme
  south-west
• Generally SHF is also larger in the other areas
  with less rainfall
• The absolute values in July are about half than
  those in June, and in August even smaller ?
  evapotranspiration still requires most of net
  radiation

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Latent heat flux (Wm-2)

• LHF is larger in the areas showing an elevate
  rainfall (west Korea) and also in correspondence
  of the maxima of net radiation, and low in the
  Seoul urban area
• August LHF values are larger than July ones
• Large LHF large evapotranspiration ? lower soil
  moisture

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Surface soil moisture

• The surface soil moisture (expressed as fraction
  of the porosity) is larger in the western part of
  the peninsula, and appears to be not too much
  correlated with the precipitation
• The central and south-eastern area have smaller
  soil moistures, due to the strong evaporation but
  also to lower precipitation
• The north-western area has a surface soil
  moisture close to the field capacity during all
  summer months

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Conclusions and perspectives

• The spatial distribution of variables shows that
  the mountainous areas, which get the maxima of
  precipitation, have a very strong
  evapotranspiration which consumes efficiently the
  soil moisture
• The urban and suburban area of Seoul shows lower
  values of soil moisture and evapotranspiration,
  and higher values of sensible heat flux and soil
  temperature (with respect to neighbouring areas)
• The south-eastern areas, in which precipitation
  is lower, are the warmer areas of Korea
• A future analysis could be the validation of LSPM
  over the main climatic Korean areas by comparing
  some variables calculated by the model with
  observations

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