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: [email protected], Web: http://www.ph.unito.it/cassardo/
Summary
 1. General description of the LSPM
 2. Simulations during the 2003 summer
 3. Simulations over the Asian monsoon in
Korea
2
1. General description of the model
3
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
4
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
5
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
6
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 multilayer soil or lake
7
Hydrological processes
The hydrological processes:
• Snow accumulation and melt
• Rainfall,
interception,
infiltration and runoff
• Soil hydrology, including water
transfer in a multi-layer soil
8
THE RADIATIVE BALANCE
The radiative fluxes include absorption,
transmittance of solar radiation and absorption
longwave radiation. They are critical for the
balance.
The surface energy balance, expressed in W/m2,
reflection and
and emission of
surface energy
is:
Rn = H + vE + Qg + Ph
9
The hydrological balance
In the mesoscale modeling the local balance is important 
storage of water into terrain
The hydrological balance is given by:
Storage of water into terrain
Runoff (excess of water infiltration into soil)
Evapotranspiration
Precipitation reaching soil
p = E + r + S
10
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
11
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 z0w+d and the
atmosphere at height zatm is partitioned into vegetation and ground
fluxes as
 atmC p (eatm  es )
E  
  v Ev  1   v Eg

r0 w
E g  
E v  
E
 atm C p [e s  e * (Tg )]

 atm C p

r ' 0 w  rsrf
[e s  e * (Tv )][ f wet (
LS
L
)  (1  f wet )(
)]
rb
rb  rs
Eg
Ev
L and S are the leaf and stem area indices. rb is the average leaf boundary
layer resistance (sm-1) and r’0h is the aerodynamic resistance (sm-1)
between the ground (z’0h) and d+z0h. rs is the stomatal resistance (sm-1).
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2. Simulations during the 2003 summer
13
L’anomalia 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 3-6°C,
con
il
massimo
sulla
Francia
e
sulla regione alpina
Paragonata con la
statistica
del
periodo
1961-90,
quest’anomalia
corrisponde a 5
14
America
Atlantico
Europa
Asia
È stata un’anomalia solo europea!!!
Diagrammi di Hovmoller dell’anomalia termica a 850 hPa rispetto al periodo (1972–2001) delle
analisi ERA-40 mediate sul rettangolo 35°N–60°N nel mese di agosto. Isolinee ogni 2°C. Sono
evidenziate le regioni con anomalie superiori a |4°C|
15
La stazione di Torino
•
•
Negli ultimi 200 anni si sono verificati almeno una dozzina di anomalie
(rispetto al periodo 1961-90) dell’ordine di 2°C
Nell’estate 2003, l’anomalia è stata 5.3 °C
6.0
Torino temperature anomalies (°C)
5.0
4.0
3.0
2.0
1.0
0.0
-1.0
-2.0
-3.0
Years
17
5
17 3
6
17 3
7
17 3
8
17 3
9
18 3
0
18 3
1
18 3
2
18 3
3
18 3
4
18 3
5
18 3
6
18 3
7
18 3
8
18 3
9
19 3
0
19 3
1
19 3
2
19 3
3
19 3
4
19 3
5
19 3
6
19 3
7
19 3
8
19 3
9
20 3
03
-4.0
16
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,
nell’estate 2003 è stata circa 50 W/m2 superiore alla norma
• La radiazione netta è stata circa 25 W/m2 superiore alla norma

Energy balance
300
GR
NR
HA
FA
QF+QG
250
W/m2
200
150

100
50

0
-50
1999
2000
2001
2002
years
2003
2004
Il flusso di calore
latente è stato
inferiore
alla
norma a luglio,
quasi normale negli
altri mesi
Il
flusso
ariavegetazionesuolo
è
stato
normale
Il flusso di calore
sensibile è stato
45
W/m2
superiore
alla
norma
17
Andamenti di alcune grandezze
Radiazione solare (Wm2)
Precipitazione cumulata (mm)
Flusso di calore sensibile (Wm2)
Flusso di calore latente (W/m2)
18
Andamenti di alcune grandezze
Rateo di evaporazione (mm)
Temperatura del primo strato di suolo (°C)
Conclusioni
Umidità del primo strato di suolo
• Riscaldamento prodotto da due cause:
• Moti
subsidenti
(riscaldamento
adiabatico)
• Suolo troppo secco per consentire
un’adeguata evapotraspirazione  solo
flusso di calore
sensibile 
surriscaldamento (effetto quantificato in
2°C circa su Torino, e non presente sul
Piemonte orientale)
19
3. Simulations over the Asian monsoon
in Korea
20
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 > 32°C
with dew-points > 24°C
• 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)
21
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
22
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
23
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
24
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
25
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
26
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