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 Web:

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

3 1. General description of the model

4 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 The LSPM (Land Surface Process Model)

5 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

6 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

7 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 Physical processes

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

9 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/m 2, is: THE RADIATIVE BALANCE Sensible heat flux R n = H + v E + Q g + P h Latent heat flux Soil-atmosphere heat flux Photosynthesis heat Net radiation

10 The hydrological balance In the mesoscale modeling the local balance is important storage of water into terrain The hydrological balance is given by: Precipitation reaching soil Evapotranspiration Runoff (excess of water infiltration into soil) Storage of water into terrain p = E + r + S

11 The turbulent heat fluxes in the surface layer A flux F of the generic variable in the surface layer can be described by the flux-gradient equation: The coefficient K represents the ability of the process in the transfer of the variable The above equation can be integrated. The flux F can be considered constant in the surface layer. The result is an equation similar to the Ohm law: gradient Flux = resistance

12 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 q v and ground q g 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 z 0w +d and the atmosphere at height z atm is partitioned into vegetation and ground fluxes as L and S are the leaf and stem area indices. r b 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+z 0h. r s is the stomatal resistance (sm -1 ). E EgEg EvEv

13 2. Simulations during the 2003 summer

14 Lanomalia di temperatura I valori rientrano nel range 3-6°C, con il massimo sulla Francia e sulla regione alpina Paragonata con la statistica del periodo , questanomalia corrisponde a 5 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

15 America Atlantico Europa Asia È stata unanomalia solo europea!!! Diagrammi di Hovmoller dellanomalia 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|

16 La stazione di Torino Negli ultimi 200 anni si sono verificati almeno una dozzina di anomalie (rispetto al periodo ) dellordine di 2°C Nellestate 2003, lanomalia è stata 5.3 °C

17 Bilancio energetico a Torino Simulazione eseguita con LSPM sul periodo su due stazioni: Torino ed Alessandria A Torino la radiazione globale, molto alta nel periodo marzo-settembre, nellestate 2003 è stata circa 50 W/m 2 superiore alla norma La radiazione netta è stata circa 25 W/m 2 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/m 2 superiore alla norma

18 Andamenti di alcune grandezze Radiazione solare (Wm 2 ) Precipitazione cumulata (mm) Flusso di calore sensibile (Wm 2 ) Flusso di calore latente (W/m 2 )

19 Andamenti di alcune grandezze Rateo di evaporazione (mm) Temperatura del primo strato di suolo (°C) Umidità del primo strato di suolo 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 2°C circa su Torino, e non presente sul Piemonte orientale)

20 3. Simulations over the Asian monsoon in Korea

21 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)

22 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

23 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

24 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

25 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

26 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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