Wind directional dependency of surface energy fluxes over north-eastern Siberia
and its implications*Yuji Kodama1, Norifumi Sato1, Hironori Yabuki2, Yoshiyuki Ishii1, Mutsumi Nomura3, Tetsuo Ohata1,2(1: Institute of Low Temperature Science, Hokkaido University, 2: Institute of Observational Research
for Global Change, JAMSTEC, 3: Field Science Center for Northern Biosphere, Hokkaido University)*Institute of Low Temperature Science, Hokkaido University, Sapporo 060-0819 JAPAN. E-mail:
kod@pop.lowtem.hokudai.ac.jp
Abstract
In order to better understand the water cycle over tundra, micro-meteorological and hydrological observations werecarried out over tundra near Tiksi, North-eastern Siberia and seasonal variations of energy budget components wereestimated for two years. As an average, net radiation was partitioned for sensible heat flux 25-30%, for latent heat flux
50-55% and for soil conductive heat flux 20%. Those ratios were changed by wind direction. The southwesterly winds
were warm and dry, made the sensible heat flux small or its direction changed towards ground surface, and thenortheasterly winds were cold, gave the sensible heat flux to the atmosphere from the tundra surface. The southwesterly
winds were associated with cyclone intrusions to this area and the northeasterly winds with anti-cyclones. Morefrequent intrusions of cyclones would decrease the sensible heat flux and increase the latent heat flux. A simple airtemperature increase experiments using a simple heat balance model showed that the sensible heat flux decreased, thelatent heat flux unchanged and conductive heat flux in soil increased.
Keyword: tundra, energy budget, wind direction, heat flux
1. Introduction
As a part of GAME-Siberia project,hydrological and meteorological observations for a basinwater/energy balance have been carried out in Siberian
tundra region near Tiksi, Sakha Republic, RussianFederation from 1997 to 2001. The tundra area has aunique water cycle due to the existence of frozen ground,
drifting snow and tundra vegetation. The frozen groundlimits the subsurface flow and the subsurface storage andits change is small. The low vegetation and strong windredistributes the snow once fallen on the ground andforms snow drifts at the leeward of ridges and thedepression.
The meltwater from the snowdrifts
becomes a resource of the summer runoff for the tundra
watershed, where liquid precipitation is small. The low
vegetation distribution, such as lichen, moss and sedge,
also play an important role in the evaporation over thetundra watershed, although the soil water content in turn
determines the vegetation distribution. The mosses andlichens do not have stomata, and behave like a sponge.
When the surface is totally wet, evaporation issubstantial, but when the surface becomes dry, theevaporation becomes small and the surface temperature
becomes high, even though a few centimeters below thesurface is very wet and cool. These energy/water fluxes
are also dependent on the atmospheric conditions. In
this paper, the annual water balance and seasonalvariation of heat balance at the tundra surface arereported, with particular emphasis on the wind direction
dependency.
2. Observation site
An experimental watershed of 5.5 km2, 7 km
south of Tiksi, Sakha Republic, Russia has been selectedfor analysis in this study (71oN, 129oE) (Fig. 1). It is atributary of the Suonannav River and the elevations
range from 40 m to 360 m m.s.l.. We have initiatedmonitoring of snowmelt and summer heat and water

Fig.1: Observation sitebalance of patch and basin scales, installation of full
meteorological station, monitoring the variation of soil
moisture, evaluating the variation of one-dimensional
vapor and energy flux, and monitoring the variation ofactive layer (thickness, temperature, moisture) over a 1
km2 grid.
The climatic data have been collected at thenearby Polyarka Hydrometeorological Station since 1932.
The climatic (30 year mean of the period from 1955 to1984) annual mean air temperature is –13.5 oC and thehighest air temperature recorded was 32.6oC and thelowest –53.6oC. The annual mean wind speed is 5.0

ms-1, with the prevailing wind direction of northeast insummer and southwest in winter. The annual mean
precipitation is 345 mm.

(1)
(2)
(3)
(4)

W/m2

Daily Heat Balance, Tiksi, 1998

HsLEG

Rn

6/24

7/14

8/3

8/23

Rn0-50-100100%

9/12Fig. 2: Daily heat balance in 1998.
arbitrary surface temperature is given, then the transfercoefficient is calculated, and the surface temperature isobtained iteratively by Newton-Lappson method.
Using the newly obtained surface temperature, newtransfer coefficient is calculated again and the same
method is repeated until the surface temperature does notchange. When the surface temperature is obtained, theheat balance components are calculated.
The results of the daily values of the heatbalance components for 1998 are shown in Fig.2. The
similar result was obtained for 1999. The net radiation
has a maximum in the end of June and then gradually

80%
60%
40%
20%

Average

Sep-1

G

Aug-3

Aug-2

LEAug-1

Hs

Jul-3

Jul-2

Jul-1

0%
Jun-3

S￬ and S￪ are the incoming and outgoing short wave
radiation, respectively, L ￬ the incoming long wave
radiation, σ the Stefan-Boltzman constant, Ts thesurface temperature, Hs the sensible heat flux, lE thelatent heat flux, G the heat flux in soil, ρthe density ofair, Cp the specific heat capacity of air, D the turbulent
transfer coefficient, Ta the air temperature, β theevaporation efficiency, LV the latent heat of vaporization,ea the vapor pressure of air, ess the saturation vapor
pressure at the surface temperature Ts, P the barometricpressure, K the heat conductivity of soil and Tz the soil
temperature at the depth of z. The turbulent transfer
coefficient D is changeable with the stability of theatmosphere as shown by Thom (1975). The heat
conductivity of soil is changed linearly with the soil
moisture at the depth of 0.05m. To solve Eq. 1, first an

250
200
150
100
50
0-50-100-150
6/4G50

Jun-2

Hs=ρCpD(Ta-Ts)
LE=0.622βρLVD(ea-ess)/P
G=K(Ts-Tz)/z=0LE

100

Ratios to net radiation

S￬-S￪+L￬-σTs4+Hs+lE+G=0

Hs150

W/m2

3. Heat balance
Micro-meteorological observations have been
carried out in the flat plain of the tundra region (Fig.1)
using 10 m tower as well as soil temperature and watercontents in the active layer.
In order to estimate the heat balancecomponents, heat balance equation (Eq.1) was solved forthe surface temperature, Ts, by iteration.

Heat Balance, Tiksi, 1998

Fig. 3: 10 day mean heat balance components and theratios to the net radiation for 1998.
decreased. The heat flux in soil is the smallest in thecomponents and does not change much. The sensible
heat flux is large in the end of June but doe not show aclear seasonal variation, but sometimes show positivevalues. This coincides with the large latent flux.
These are all connected to a wind direction, which will
be discussed later. The 10 day mean heat balancecomponents and their ratio to the net radiation for theperiod from June 10 to September 10 in 1998 are shownin Fig. 3. The net radiation was the largest in the end ofJune for the both year. The latent heat flux is larger
than the sensible heat flux most of the periods. The
heat flux in soil is smallest among the components anddecreasing gradually towards fall.
When the sensible heat flux is positive(towards ground), the latent heat flux usually becomeslarge. Net radiation is partitioned to sensible, latent andsoil conductive heat fluxes.
The ratios of thesecomponents to the net radiation are shown in the secondand forth figure in Fig. 3. The mean ratios are 25-30%
for sensible heat flux, 50-55% for latent heat flux and20% for soil conductive heat flux.

4. Wind direction dependency
We have seen that the positive value (towards ground)of sensible heat flux and large latent heat flux at the sametime. This is closely connected to the wind direction.
Fig. 4 shows the wind directional dependency of heatbalance and meteorological components in 1998. From
the top, frequency of wind direction, ratio of net
radiation, ratio of sensible heat flux, ratio of latent heatflux, ratio of soil conductive heat flux, average airtemperature and average vapor deficit. The “ratio”
means the ratio of total heat flux in the specific winddirection to the total heat flux for all wind direction.

Jun1
Jul2
Aug3

Jun2
Jul3
Sep1

Jun3
Aug1All

Jul1
Aug23020100Ratio (%)

N

80
60
40
200-20

E

SE

SSW

W

NW

Net Radiation, Tiksi, 1998

NNE

ESESSW

W

NW

W

NW

W

NW

W

NW

100
0-100

NNE

ESES

SW

0-50Ratio (%)

Ratio (%)

-200

Lat e n t He at Flu x, Tiksi, 1 9 9 810050100500-50NNE

temperature(℃)

SE

S

SW

Heat Flux in Soil, Tiksi, 1998

NNE

E

SES

SW

Air Temperature (4m), Tiksi, 1998

3020100NhPaE

NE

E

SE

S

SW

W

NW

SW

W

NW

Vapor Deficit, Tiksi, 1998

25
20
15
1050N

NE

E

SE

S

3 0 0 .0
2 0 0 .0
1 0 0 .00 .0
NNE

E

SE

S

S W W NW

Fig.5: The ratio of evapotranspiration and the diffusion
resistances for each wind direction

Sensible Heat Flux, Tiksi, 1998

200Ratio (%)

NE

Resistance (sm-1)

Frequency (%)

Wind Rose, Tiksi, 1998
40

Win d dir e c t io n an d e vapo tr an spir at io n ,r e sistan c erarirc
5 0 0 .0
4 0 0 .0

Fig. 4: Wind directional dependency of heat balance andmeteorological components.
The most frequent wind direction is east and northeast,
which are the same as the climatic prevailing winddirection of Poliarka Hydro-meteorological station insummer. Easterly and northeasterly winds are onshore
winds, and oppositely southwesterly and westerly winds
are offshore winds. The sensible heat flux is large andpositive for onshore wind but mostly small or negativefor offshore wind. This is obvious for the most of theperiods, especially in the end of July (Jul3). The latentand soil conductive heat fluxes do not clearly depend on
the wind direction.
For the offshore wind, airtemperature is high and the vapor deficit is large,
whereas onshore wind is cold and has smaller vapor
deficit. The wind direction dependency of the heatbalance components was also found in Alaska andNorthern Canada (Yoshimoto et al. 1996, Rouse et al.
1987, Rouse 1984).
In order to discuss the effect of the differencein microclimate on the vegetation activity and the energy
partition, diffusion resistance to vapor transfer for eachwind direction was calculated in daytime between 0900
and 1500, local time, and shown in Fig. 5, where ra is theaerodynamic resistance, ri the isothermal (orclimatological) resistance and rc the canopy resistance.
The equations for the resistances are written in, forexample, Harazono et al. (1998). The aerodynamic
resistance ra did not show strongly the wind directional
dependency. This is mainly due to the wind speed: themean wind speed for the each wind direction did notshow preference in wind direction. The climatologicalresistance, ri, which is the ratio of the water vapor deficit
and the available energy at the canopy, showed larger
values for southerly, southwesterly and westerly winds.
This is due to the large water vapor deficit for thesoutherly and westerly air mass (see the bottom figure inFig. 4). The canopy resistance, rc, which is a functionof ri and Bowen ratio, showed the larger values for thewest and southwest wind directions as well as the eastand northeast wind directions. This is quite different
from the result of Harazono et al. (1998) in Northern
Alaska, where canopy resistance as well as the other tworesistances showed small for onshore winds and large foroffshore winds. The large rc for the offshore winds inthis study are mainly due to the large water vapor deficitof the westerly and southwesterly air masses. The large
rc also for the onshore wind could be explained by thelow temperature of the air mass: low air temperature
gives large sensible heat flux towards atmosphere andlarge Bowen ratio. Although the water vapor deficit issmall for this onshore wind, the large Bowen ratio, whichmight be the results of dryness of the ground surface,gives the large rc.
Figures 6 show the examples of the synoptic
weather conditions for the case of north-easterly wind(left) and south-westerly wind at Tiksi. Most of thesouth-westerly winds associate with the cyclone

HL

Fig.6:
Synoptic
atmosphericconditionsfor
north-easterlies (left) and south-westerlies (right).
Contour lines show the isobars, thin arrows winddirection and speed and colored contours air temperature.
Thick arrow indicates the location of Tiksi.
intrusion from southwest, and the north-easterly winds
with the anti-cyclones. Further analysis showed thewind direction change in Tiksi is not strongly influenced
by land-see breeze.
According to the global change scenario(IPCC,1996), the air temperature at the Arctic area will
increase by 3-4 ℃ with an increase in atmosphericgreenhouse gas concentrations. If the warmer and drier
air mass would be coming from west and southwest more
frequently by global warming, the tundra surface would
become drier and the surface air temperature would
further become higher, giving a positive feedback. If
the temperature difference between continent and Arctic
Ocean would become larger by the global warming, theopposite trend could be found. If global warming
would make the continent warmer but would not warm
the ocean surface relatively, giving a larger temperature
difference between the continent and the ocean, theonshore winds would be more frequent and the tundra
surface would be colder, resulting in a negative feedbackeffect. However, further study is warranted.
Fig. 7 shows the results of the warming
simulations by simply adding –2oC, -1oC, 0oC, +1oC, and+2oC to the air temperature and recalculate the surface
heat balance equation (1) by iteration as mentioned
above. The ordinate in Fig.7 shows the anomaly offluxes from those of the zero-warming situation
normalized by the mean fluxes. When the warming
increases, the sensible heat flux decreases, soil
conductive heat flux increases and the latent andradiative heat fluxes do not change much. The increaseof air temperature decreases the temperature difference
between air and land surfaces, on which net radiation
absorbed is not much changed. This is the reason thesensible heat flux decreases by the warming. Since therelative humidity is not changed, the increase in air
temperature keeps the air moister, therefore the latent
heat fluxes is not changed by warming. The soil
conductive heat flux is increased by the warming. Thismeans the warming of the ground temperature andeventually increasing of the active layer thickness.
5. Summery
We have studied the summer heat balance fora tundra watershed near Tiksi, Sakha Republic, Russia.
Strong wind direction dependency on sensible heat
fluxes were observed: southerly and southwesterly winds

Fig. 7: The results of in the cases of the simply changing
the air temperature.
increasing the are warm and dry, giving sensible heat
flux towards the ground surface and the larger latent heat
flux, easterly and northeasterly winds are cold andsmaller vapor deficit, giving a large sensible flux to theatmosphere from the tundra surface. Those winddirections were caused the by the synoptic atmosphericconditions, not by the local wind like sea-land breezes.
Global warming due to green house effect gas increase is
expected in these tundra area, however, further studies iswarranted to determine future tundra conditions.
Acknowledgments
The data used in this paper was obtained by
the GAME-Siberia project supported by the Ministry ofEducation, Science, Sports and Culture of Japan and theFrontier Research System for Global Change.
References
HarazonoY., Yoshimoto, M., Mano, M., Vourlitis, G.L.
and Oechel, W.C. 1998 Characteristics of energy
and water budgets over wet sedge and tussock
tundra ecosystems at North Slope in Alaska.
Hydrol. Process. 12, 2163-2183.
IPCC, 1996, ‘Climate Change 1995’ Houghton, J.T.,
MeiraFelho, L.G., Callander, B.A., Harris, N.,
Kattenburg, A. and Maskell, K. (eds.). Cambridge
University Press, Cambridge. 572pp.
Kane, D.L., Gieck, R.E. and Hinzman, L.D. 1990.
Evapotranspiration from a small Alaskan Arcticwatershed. Nordic Hydrology, 21, 253-272.
Rouse, W.H., Hardhill, S.G. and Lafleur, P.M., 1987.
The energy balance in the coastal environment ofJames Bay and Hudson Bay during the growing
season. J. of Climatol., 7, 165-179.
Rouse, W.R. 1984 Microclimate at Arctic tree line 3. The
effects of regional advection on the surface energybalance of upland tundra. Water Resour. Res. ,20(1), 74-78.
Thom, A.S., 1975. Momentum, mass and heat exchangeof plant communities. Vegetation and Atmosphere,4, Monteith, J.L. (Ed.), Principles, Academic Press,London, 57-109.
Yoshimoto, M., Harazono, Y., Miyata, A. and Oechel,W.C. 1996. Micrometeorology and heat budget over
the Arctic tundra at Barrow, Alaska in the summerof 1993. J. Agric. Meteorol., 52(1), 11-20.