Method for Calculating the Amount of Accumulated Snow Transported during a Single Blizzard

Civil Engineering Research Institute for Cold Region, PWRI, JAPANhttp://www2.ceri.go.jp

Method for Calculating the Amount of Accumulated Snow Transported during

a Single Blizzard

Masaru Matsuzawa1, Yasuhiko Ito and Masayo Ueda

1 The Civil Engineering Research Institute for Cold Region, Public Works Research Institute, JAPAN

Email: [email protected]

15th International Road Weather ConferenceFebruary 5th - 7th, 2010 in Québec City, Canada


1. Introduction


Background to the study

More than 100 vehicles stalled in the Kushiro/Nemuro district on March 31 and April 2, 2008. 　

How often do such blizzards occur?

Naganuma

Kushiro/Nemuro district

Approximately 140 vehicles were trapped in accumulated snow on National Route 274 in Naganuma near Sapporo on February 23 and 24, 2008.


Purpose of the study■Indexes to represent blizzard intensity ・ Maximum amount of accumulated snow (Fukuzawa et al., 2000) ・ Frequency of blizzards (Ishimoto, 1987)There are no indexes to represent the intensity of a single blizzard.

■Purpose of the studyDevelopment of an index to represent the intensity of a single blizzard•A single blizzard was defined.•The total transport rate of blowing snow during a single blizzard were calculated for the aforementioned cases.•The probability period for replication of the total transport rate of blowing snow was found.

｝ Blizzard intensity for the year


Contents1. Introduction2. Study Method3. Results4. Improvement of the method for

estimating the maximum transport rate of blowing snow

5. Conclusion


2. Study Method


Relationship between the transport rate Relationship between the transport rate of blowing snow Q and wind velocityof blowing snow Q and wind velocity

Definition of the transport rate of blowing snow Q:Definition of the transport rate of blowing snow Q:Mass of snow blown particles that passes through a particular unit

width perpendicular to the wind direction during a fixed time [g/(ms)][g/(ms)]

Relation between the transport rate of blowing snow Q and wind Relation between the transport rate of blowing snow Q and wind velocityvelocity (Kobayashi D. (1972))

Q=0.03VQ=0.03V1133

[g/(ms)][g/(ms)] ・・・ (1)

Where, V1 is the wind velocity at a height of 1 m.


Conditions required for the occurrence of blowing snow

• Conditions required for the occurrence of blowing snow during snowfall (Takeuchi et al., 1986)

• Blizzard conditions were assumed when either set of the following criteria were satisfied:

1: An air temperature of < -2°C, a wind velocity of > 5.0 m/s and a snow depth of > 1 cm

2: An air temperature of < 0.5°C, a wind velocity of > 7.5 m/s and a snow depth of > 1 cm

: low drift snow: intermittent high drift snow: continuous high drift snow


Definition of a single blizzardConditions required for blowing snow occurrence1.1. An air temperature of < -2°C, a wind velocity of > 5.0 An air temperature of < -2°C, a wind velocity of > 5.0

m/s and a snow depth of > 1 cmm/s and a snow depth of > 1 cm2.2. An air temperature of < 0.5°C, a wind velocity of > An air temperature of < 0.5°C, a wind velocity of >

7.5 m/s and a snow depth of > 1 cm7.5 m/s and a snow depth of > 1 cm

• A blizzard was considered to have ended when the above necessary conditions for blowing snow occurrence were not satisfied for six consecutive hours.

• The period between the start and end of a blizzard was defined as a single event.


Estimation of the transport rate of blowing snow Q and probability of replication

Q=0.03VQ=0.03V1133

[g/(ms)][g/(ms)] ・・・ (1)

The total value from the beginning to the end of a blizzard. Total transport rate of a single blizzard: Qsum [kg/m]

The probability of replication was calculated using Iwai’s method on the assumption that the annual maximum values for Qsum follow the logarithmic normal distribution.

AMeDAS: Automated Meteorological Data Acquisition System


3. Results


Case of Naganuma• Total transport rate of blowing snow Qsum

Naganuma AMeDAS (wind velocity, air temperature) and Eniwa-Shimamatsu AMeDAS (snow depth) data from the 23 winters from November 1981 to April 2004 were used.The results were compared with the transport rate of blowing snow on February 23 and 24, 2008.

Sapporo

Naganuma*Qsum was converted to a volume value on the assumption that the snowcover density was 350 kg/m3.

Period Qsum [m3/m]*Feb. 12 – 18, 1991 8.6March 8 – 9, 2003 5.0Feb. 23 – 24, 2008 4.6


Case of NaganumaProbability period for replication of the blizzard in February 2008:Approx. 10 years

1

10

100

1000

1.0 10.0 100.0 Pro

babi

lity

perio

d of

repl

icat

ion

(yrs

)

Transport rate of blowing snow (m3/m)

February 23 – 24, 2008, 4.6 m3/m

Case of the Kushiro/Nemuro districtAttoko AMeDAS (wind velocity, air temperature and snow depth) Data from the 18 winters from November 1986 and April 2004 were used.The probability period for replication of Qsum between March 31 and April 2, 2008 was more than 1,000 years.

Sapporo

Attoko

1

10

100

1000

0.1 1.0 10.0

Pro

babi

lity

perio

d of

repl

icat

ion(

yrs)

Transport rate of blowing snow (m3/m)

March 31 – Apr. 2, 2008, 4.4 m3/m


4. Improvements of the method for estimating the maximum transport

rate of blowing snow


Problem

•The 10-year probability of replication seemed too large for Naganuma, which experienced a severe blizzard in February 2008.

•Weather conditions in February 1991, March 2003 and February 2008 were reviewed.


Weather conditions during blizzardsFebruary 15 – 18, 1991

-20

-15

-10

-5

0

5

02468

101214161820

1:00

7:00

13:0

0

19:0

0

1:00

7:00

13:0

0

19:0

0

1:00

7:00

13:0

0

19:0

0

1:00

7:00

13:0

0

19:0

0

Tem

pera

ture

(C)

Suns

hine

Dur

ation

(h)

Prec

ipita

tion

(mm

) W

ind

Spee

d (m

/s)

Precipitation (mm) Sunshine Duration (h)

Wind Speed (m/sec) Temperature ( C゚)


Weather conditions during blizzards

March 7 – 10, 2003

-20

-15

-10

-5

0

5

02468

101214161820

1:00

7:00

13:0

0

19:0

0

1:00

7:00

13:0

0

19:0

0

1:00

7:00

13:0

0

19:0

0

1:00

7:00

13:0

0

19:0

0

Tem

pera

ture

(C)

Suns

hine

Dur

ation

(h)

Prec

ipita

tion

(mm

) W

ind

Spee

d (m

/s)



There was an almost total lack of precipitation.


Weather conditions during blizzards

February 21 – 24, 2008

-20

-15

-10

-5

0

5

02468

101214161820

1:00

7:00

13:0

0

19:0

0

1:00

7:00

13:0

0

19:0

0

1:00

7:00

13:0

0

19:0

0

1:00

7:00

13:0

0

19:0

0

Tem

pera

ture

(C)

Suns

hine

Dur

ation

(h)

Prec

ipita

tion

(mm

) W

ind

Spee

d (m

/s)




Improvement of the method for estimating the total transport rate of blowing snow Qsum

• Blizzards are unlikely to occur when there is no fresh snow on the surface. There may be some overestimation regarding the transport rate of blowing snow when there is no snowfall.

• The total snowfall over a distance of 300 m on the windward side from 24 hours before the onset to the end of the blizzard was considered the maximum amount for Qsum.

• This value was defined as the maximum possible transport rate of blowing snow Qmax.

The total transport rate of blowing snow Qsum was calculated again on the assumption that:

Qmax ＝ 300 x total snowfall Qsum≦Qmax


0

1

2

3

4

5

6

7

8

9

10

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2008

Max

imum

val

ue o

f the

tot

al a

mou

nt o

f bl

owin

g sn

ow (m

3 /m

)

Annual maximum values for the total amount of blowing snow Qsum

Qsum in March 2003 became smaller.Qsum in February 1991 ＞ Qsum in February 2008

Before Improvement


4. Conclusion


Conclusion• The probability period was approximately 10 years for Qsum in Naganuma

on February 23 and 24, 2008, and more than 1,000 years for that in Attoko on March 31 and April 2, 2008.

• The calculation method for the total transfer rate of blowing snow was corrected. The results indicated that the probability period of replication for the blizzard in Naganuma in February 2008 was approximately 30 years.

• Qsum was still lower in February 2008 than that in February 1991 in Naganuma.

We intend to conduct a more detailed examination of this calculation method for the transfer rate of blowing snow in the future.


Thank you for your attention!

Documents

Method for Calculating the Amount of Accumulated Snow Transported during a Single Blizzard