DSWS2017, Tsukuba Oct. 2-4, 2017

Past simulation and future projectionof snowfall over mountainous areas incentral Japan
Outlines
1. Introduction
2. Simulation of recent mountainous snow cover
3. Future projections in snowfall in Japan
4. Next step and Summary

Hiroaki Kawase (Meteorological Research Institute, Japan)
Hidetaka Sasaki, Akihiko Murata, Masaya Nosaka, Izuru Takayabu (MRI),
Takahiro Sasai, Takeshi Yamazaki (Tohoku Univ.),
and Akira Yamazaki (JAMSTEC)Mechanism of large
snowfalls in Japan

coldand dryWarm SST↓
humid air mass

From JMA web site

Northwesterlysnowfall
Siberia

Sea of Japan

Sea of Japan
side

JAPAN
Pacific Oceanside

Colder air from Siberia and warmer SST result in more developedsnow clouds and heavier snowfall

1

Niigata prefecture, Feb, 20062

Introduction
 Heavy snowfall and large amount of snow cover causes
avalanches, traffic accident, and isolation of small town.
[Kawashima et al., 2015]

 Large snow cover over the mountainous areas is, on theother hand, important for water resources and winter sports.
 There is few observations over high mountainous areas.
Understanding of mountainous snow cover is insufficient.
 Due to global warming, total snowfall and maximum snow
depth will widely decrease in the future, while in colder
regions, snow cover could increase because of moistening.

[Brown and Mote 2009; JMA 2013; Kawase et al. 2015]

 It is still unclear if extremely heavy snowfall will increase[O'Gorman 2014; Lute et al. 2005]
or decrease due to global.
3

Introduction
 Heavy snowfall and large amount of snow cover causes
avalanches, traffic accident, and isolation of small town.
[Kawashima et al., 2015]

 Large snow cover over the mountainous areas is, on theother hand, important for water resources and winter sports.
 There is few observations over mountainous areas.
Understanding of mountainous snow cover is insufficient.
 Due to global warming, total snowfall and maximum snow
Topics of my presentation are
depth will widely decrease in the future, while in colder
1. Snowsnow
covercoversimulations
in recent
16 years
over theregions,
could increase
becauseof moistening.

[BrownMote 2009;
JMA 2013; Kawase et al. 2015]
Japanese Northern Alpsin andcentralJapan

 It is still unclear if extremely heavy snowfall will increase
2. Future changes in heavy snowfall[O'Gormanin Japan
2014; Lute et al. 2005]
or decrease due to global.
3

Research field and observation

Japanese Northern Alps

- Tateyama Kurobe Alpine route Target
TsukubaTokyo
Time lapse
cameraTateyama Kurobe Alpine route
Bijyodaira(977m)
Midagahara

Museum(470m)（1,930m）

Murododaira(2,450m)

Daikandai（1,470m）

2km

Google Map -©2014 Google4

Experimental design

NHRCM (Non-hydrostatic Regional Climate Model)[Sasaki et al., 2008]

Boundary Condition： JRA-55 (55 years Japan Re-Analysis data)
Grid spacing： 20km -> 5km -> 2km
Land surface： MJ-SiB
Boundary layer： Improved Mellor-Yamada Level3 (MYNN)
Microphysics：Bulk-type cloud microphysics [Murakami et al., 1994]
Cumulus convection: Kain-Fritsch (5km and 20km)[Kain and Fritsch, 1993]

Target period： Sep. 15 – Jul 15, 2000 - 2016
* Spin-up duration: Sep. 15 - Sep. 30
5Simulation of snow depth in 2014/15
Snow depth (cm)2014/15
winterbar: Observation
Bijyodaira BlackRed thick line: Nearest gridAltitude: 977m

Red thin lines: Near grids

Nearest grid： 879m
Near grid 1：936m
Near grid 2：1,036m
Near grid 3：691m
Near grid 4：966m

Daikandai

Midagahara

Nearest: 1,295m
Near grid1：1,202m
Near grid2：1,263m
Near grid3：1,021m
Near grid4：1,591m

Nearest：1858m
Near grid1：1618m
Near grid2：1856m
Near grid3：1591m
Near grid4：2133m

Altitude：1,470m

Oct Nov Dec Jan Feb Mar Apr May Jun

Snow depth (cm)Snow depth (cm)Oct Nov Dec Jan Feb Mar Apr May Jun

Altitude：1,930m

overestimatedOct Nov Dec Jan Feb Mar Apr May Jun

6Snow depth (cm)Seasonal variation of snow depth during 16 years
Bijyodaira（about 1,000m）－2014/15－2015/16－average－other year

Snow depth (cm)Oct Nov Dec Jan Feb Mar Apr May Jun

Murododaira（about 2,500m）

What happened inMarch, 2016?

■ Snow survey (Toyama Univ.)● Snow survey (TateCal Museum)

Oct Nov Dec Jan Feb Mar Apr May Jun

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Synoptic conditions in Feb. and Mar., 2016
Sea level pressure

Eddy heat flux at 850hPa (v’T’)

Feb.

Mar.

 Extremely small amount of March snowfall over high mountains

8

Synoptic conditions in Feb. and Mar., 2016
Sea level pressure

Eddy heat flux at 850hPa (v’T’)

Feb.

This small amount of snow cover was caused bynatural variability, not global warming.
To evaluate snow cover changes due to global warming,
ensemble regional climate projections were analyzed.
Mar.

 Extremely small amount of March snowfall over high mountains9Large ensemble climate simulations
Database for Policy Decision making forFuture climate change (d4PDF)

SOUSEI■ Global climate experiments （MRI-AGCM3） 60km
○ Historical experiments (61yrs, 100 member) [6100yrs]
SST: COBE-SST2 1950～2011 (with 100 initial perturbations)○ Future experiments (61yrs, 90 member) [5490 yrs]

SST: Historical SST plus 6 SST anomalies of CMIP5 CGCMs between past andfuture climate assuming 4 K warming (around 2080-2099)■ Regional climate experiments （NHRCM） 20km
Initial and lateral boundary conditions: MRI-AGCM○ Historical experiments (61 years, 50 member)48 members○ Future experiments (61 years, 90 member)48 members

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Future changes in extremely heavy daily snowfall
Total snowfall changes

Decrease

Heavy daily snowfall changes(occurring every 10 years)

Increase!

Remarkable increase in daily snowfall
around Central Japan, Hokkaido, andeastern parts of Asian continent.

11Why increase? Composites of top 50 heavy snowfall events

Precipitation(snowfall+rainfall) and surface wind
Historical experiments
Paektu Mountain

Future exp. – Historical exp.
Precipitation(2744m)Increaseconvergencezone(JPCZ)

×- Increased precipitation around JPCZ.
- Intensification of JPCZ
X : Location of Tsunan station

JPCZ: Japan sea Polar air mass Convergence Zone

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Why increase? Composites of top 50 heavy snowfall events

Precipitation(snowfall+rainfall) and surface wind
Mean vertical wind anddifferences

Future exp. – Historical exp.
Precipitation

Increase

Enhancement of JPCZ

- Increased precipitation around JPCZ.
- Intensification of JPCZ(convergence)13

Why increase? Composites of top 50 heavy snowfall events

Precipitation(snowfall+rainfall) and surface wind
Mean vertical wind anddifferences

Future exp. – Historical exp.
snowfallDecreaseIncrease

Enhancement of JPCZ

- Decrease in snowfall over low elevation.
- Increase in snowfall over high elevation.

(convergence)13

Next Step: Higher resolution ensemble simulations
20-km NHRCM (d4PDF)
5-km NHRCM

Tokyo

Tokyo

20-kmNHRCM (d4PDF)
downscaling
5-kmNHRCM (372 years)

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Next Step: Higher resolution ensemble simulations

Classification of top 30 heavy daily snowfall events
Cold air outbreak pattern
H

highFrequency(%)

Extratropical cyclone patternlow
5-km NHRCM shows a clear boundary of synoptic patterns causing
extremely heavy daily snowfall. （clearer than all snowfall event）

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Next Step: Higher resolution ensemble simulations

Classification of top 30 heavy daily snowfall events
Cold air outbreak pattern
HFrequency(%)

Extratropical cyclone patternhighlow
Future climate projections with 5-km NHRCM can evaluate
5-km NHRCM shows a clear boundary of synoptic patterns
future changes
in heavy
snowfall in each pressure pattern.
causing heavy
daily snowfall.

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Summary- Snow covers are well simulated by 2-km NHRCM aroundJapanese northern Alps. The extremely small amount of snow
in 2016 was caused by the weak cold air outbreak and inactive
extratropical cyclone in March.
- Due to global warming, total winter snowfall will decrease,
while extremely heavy daily snowfall occurring once every ten
years could increase on the mountainous areas in central Japan.
- The composite analysis indicates that the Japan sea Polar air
mass Convergence Zone (JPCZ) could be enhanced due toglobal warming, bringing an increase in heavy snowfall overthe mountainous areas in central Japan.
- Higher resolution simulations with 5-km grid spacing resolves
Japan’s complex mountains, showing a clear regional boundaryof synoptic patterns causing heavy daily snowfall.
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(Elevation: 2400m)

雪の大谷 19m
2017.4.23

Thank you