eurasia institute of earth sciences istanbul technical university

Eurasia Institute of Earth SciencesIstanbul Technical University


Effect of snow on weather/climateSNOW

Increase in ALBEDO (UP TO 85%)

Decrease in THERMAL CONDUCTIVITY

Decrease in TEMPERATURE

Retards MELTING IN SPRING Higher WINTER SOIL

TEMPERATURES

Decrease in GROUND HEAT LOSS

Total Winter Energy Exchange is a complex balance between these

two competing processes

•"© Copyright 2002 Jian Shuo Wang. All right reserved." •http://www.wangjianshuo.com/personal/places/daocheng

Relation between Tibetan Plateau snowand East Asian summer monsoon:Preliminary results from a RCM

experiment



Snow in Tibetan Plateau in 1998

3.2 The anomalously more snow over the Tibetan Plateau

In winter the Tibetan Plateau is a heat sink while in summer the Tibetan Plateau acts as a heat source. This seasonal variation of the heating effect of Tibetan Plateau plays an important role in the intensity and progress of East Asian monsoon. The snow cover was anomalously extensive over the Tibetan Plateau last winter and this spring. This caused a slow progress of East Asian monsoon and a weak summer monsoon by reducing the heating over the Plateau. Correspondingly, the subtropical high over the western Pacific is intensive, but is located to the south of its normal position. The main rain belt in China shifted to the south so that more rainfall occurred over the Yangtze River valley. However, the snow-climate feedback is of much uncertainty, partly due to the lack of reliable snow data. Yong Luo and Ning Zeng UCLA TROPICAL METEOROLOGY NEWSLETTER No.26 (October 13,1998)

H

A


Experiment

Ensemble simulation initialized with 1998 snow cover/depth

ECMWF dynamicdownscaling with2.5-day e-foldingtime

Ensemble simulation initialized with climatological snowcover/depth

TEST AREA


Biosphere-Atmosphere Transfer Scheme

Regional Climate Model

The Regional Climate Model (IPRC-RegCM, Wang et al., 2002) was developed at the IPRC primarily to study the dynamics of A-AMS at high resolution.The model that has 28 levels uses hydrostatic primitive equations and it’s physics include:

E-ε (Turbulent Kinetic Energy and its dissipation) closure scheme

A modified Monin-Obukhov scheme for the surface flux calculations at the ocean surface

Explicit treatment of mixed-ice phase cloud microphysics

A frictionally-induced dissipative heating

An advanced radiation scheme (Edward and Slingo, 1996)

A mass flux cumulus parameterization scheme (Tiedtke, 1989; Nordeng, 1995)

An advanced Land Surface Model (BATS, Dickinson et al., 1993) together with high resolution vegetation data from the USGS and soil classification data from the USDA


Difference (CLI-98) in Modeled Snow

MAY

AUG

JJA


Changes (CLI-98) in Heat Fluxes (JJA)

LATENT HEAT FLUX SENSIBLE HEAT FLUX


Changes (CLI-98) in Surf. Temperature (JJA)

DAILY MINIMUM TEMPERATURE DAILY MAXIMUM TEMPERATURE


Changes (CLI-98) Air Temperature (JJA)

500 MB

300 MB

700 MB


Changes (CLI-98) in Spec. Humidity (JJA)

500 MB

300 MB

700 MB


Changes in large scale circulation (JJA)

500 MB

300 MB

700 MB


Changes in Geopotential Height (JJA)

500 MB

300 MB

700 MB


Changes in Vertical Velocity (JJA)

500 MB

300 MB

700 MB


Changes in Rainfall and Surface Runoff (JJA)

TOTAL RAINFALL

SURFACE RUNOFF


Results

The modeling experiment showed that switching to climatological snow cover/depth in TP from anomalously extensive snow cover/depth in 1998 had significant effects on the EASM circulation and its rainfall.

This increases sensible heat flux and surface air temperature significantly at around the western edges of TP where difference is substantial between climatological snow and 1998 snow.

Significant, coherent changes in air temperature are also observed at different levels, especially higher levels, over eastern and northern China.

Large-scale circulation is significantly strengthened at higher levels over northern China and weakened at higher levels over southeastern flank of TP and southern China.

Significant, coherent increases in geopotential height are also observed at higher levels over eastern and northern China.

Rainfall and runoff are increased at around Yangtze River Basin but reduced southward.


Simulation of snow cover in Turkey

using a regional climate

model

MODIS Jan 20, 2004


RegCM3

Dynamics: 1. MM5 Hydrostatic Dynamics (Grell et al. 1994); 2. Non-hydrostatic (Bi)

Radiation: CCM3 (Kiehl 1996) Large-Scale Clouds & Precipitaion: SUBEX (Pal et al 2000) Cumulus convection: 1. Grell (1993); 2. Anthes-Kuo (1977); 3.

Emanuel (1991) Tracers/Aerosols: Qian et al (2001) Boundary Layer: Holtslag (1990) Land Surface: 1. BATS (Dickinson et al. 1986);

2. Subgrid BATS (Giorgi et al 2003) Ocean Fluxes: 1. Zeng et al (1998; 2. BATS Parallel Code (Ye & Bi)


Experimental Design

LambertLambertConformalConformal

GLCCGLCCVegetationVegetation

NCEP/NCAR NCEP/NCAR Reanalysis Reanalysis Initial and Initial and Boundary Boundary ConditionsConditions

NOAA OISea Surface

Temperatures

USGSUSGSTopographyTopography


Experimental Design


Interpolation of satellite data to model grids

Daily 1024x1024 NH snow cover (2000 - present) http://www.cpc.ncep.noaa.gov/data/daily_snow/

National Weather Service, Climate Prediction Center


Satellite vs. Simulation

• Nov: 0.42• Dec: 0.50• Jan: 0.48• Feb: 0.56• Mar: 0.51

• Nov: 0.71• Dec: 0.78• Jan: 0.72• Feb: 0.78• Mar: 0.73

Satellite

Model

Feb 1, 2002


13 NOV 1995

27 OCT 1995

6 NOV 1995

The heavy snows came at the peak of the trekking season and resulted in dozens of deaths due to avalanches and exposure.

13 NOV 1995

On November 10-11 the central and eastern Himalayas were hit by an extremely unusual storm which dropped up to 2 meters of snow in the mountains at a time of year when clear skies and mild temperatures are typical.The storm also covered substantial portions of the Tibetan Plateau with snow.

Source: http://www.geo.cornell.edu/grads/duncan/snowstorm/

eurasia institute of earth sciences istanbul technical university

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