Journal of the Meteorological Society of Japan, Vol. 89A, pp. 291--298, 2011.

291

DOI:10.2151/jmsj.2011-A19

NOTES AND CORRESPONDENCE
Numerical Study of the Impacts of Land Use/Cover Changes Between 1700 and 1850
on the Seasonal Hydroclimate in Monsoon Asia

Ryoji YAMASHIMA
Department of Geography, Tokyo Metropolitan University, Hachioji, Japan

Kumiko TAKATA
Research Institute for Global Change (RIGC),
Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokohama, Japan

Jun MATSUMOTO
Department of Geography, Tokyo Metropolitan University, Hachioji, Japan
Research Institute for Global Change (RIGC),
Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japanand
Tetsuzo YASUNARI
Research Institute for Global Change (RIGC),
Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokohama, Japan
Hydrospheric Atmosphere Research Center, Nagoya University, Nagoya, Japan(Manuscript received 31 May 2010, in ﬁnal form 12 September 2010)

Abstract
This study investigated the impacts of historical land use/cover changes (LUCC), from forest to cultivated land,on the seasonal cycle of the hydroclimate over the Indian subcontinent and southern China. The mechanism of these
impacts was studied by conducting numerical experiments using an atmospheric general circulation model
MIROC3.2 coupled with the land surface scheme MATSIRO and historical global land use/cover changes between
1700 and 1850. A previous study found a decrease in summer (JJA) precipitation over the Indian subcontinent andsouthern China induced by extended cultivation between 1700 and 1850. We further found that evapotranspiration in
the Indian subcontinent notably decreased, particularly in the spring, while that in southern China discernibly decreased throughout the year. The di¤erence in the changes in evapotranspiration in the spring over both regions could
be explained by the amount of precipitation during the dry season. In the Indian subcontinent, the marked decreasein evapotranspiration in May due to LUCC caused the decrease in precipitation during the same season. However,in southern China, the decrease of precipitation from March to April was contributed rather by the decrease ofwater vapor ﬂux convergence due to atmospheric circulation changes than by the decrease of evapotranspiration.
Corresponding author: Ryoji Yamashima, Tokyo Metropolitan Universigy, 1-1, Minami-Osawa, Hachioji,
192-0397, Japan.
E-mail: r.yamashima@gmail.com
6 2011, Meteorological Society of Japan

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1. Introduction
Vegetation plays an important role in the landatmosphere interaction, by impacting the energy
and water balances at the earth’s surface. In thepast, numerical experiments were conducted assuming virtual land use/cover changes (hereafter
LUCC; e.g., total deforestation of tropical rainforests over a tropical region) to evaluate the potential
impact of vegetation changes on the local or global
climate (e.g., Henderson-Sellers et al. 1993; McGufﬁe et al. 1995; Mabuchi et al. 2005). The impact ofanthropogenic LUCC on climate was recently examined using current and natural vegetation datasets (e.g., Chase et al. 2000; Fu 2003). These studies
were analyzed for a speciﬁc season (i.e., JJA or
DJF) or for a speciﬁc month (i.e., July or January).
Voldoire and Royer (2004) evaluated the detailsof the impact of deforestation in Africa and the
Amazon regions on their regional climates, using ageneral circulation model (GCM) with virtual deforestation. They found that deforestation in thesouthern Amazon and Africa caused the soil moisture to decrease throughout the year, and the soil
evaporation to increase during the rainy season
and decrease during the dry season. Findell et al.
(2007) focused on the impact of anthropogenic
LUCC on climate, using a GCM with current andnatural vegetation datasets. They showed that soil
moisture and latent heat ﬂux in northern India decreased during the rainy season and was unchanged
during the dry season.
Takata et al. (2009) investigated the impact
of LUCC from forest to cultivated land between
1700 and 1850 on the Asian summer monsoon.
They conducted GCM experiments using historicalglobal land use/cover data reconstructed for thelast 300 years, and they reported that extended cultivation from 1700 to 1850 signiﬁcantly decreased
precipitation during JJA over the Indian subcontinent (hereafter IND region) and southeastern China(hereafter SCH region). This result was consistent
with the monsoon rainfall trend during this period
derived from the Himalayan ice core (Duan et al.
2004). However, they discussed the impact on the
Asian summer monsoon rainfall only during JJA.
The impacts of LUCC on the seasonal changesof precipitation and evapotranspiration over the
Indian and China regions have been examined by
Zhao et al. (2001) using GCM with natural andcurrent vegetation datasets. They showed that precipitation decreased throughout the year over bothVol. 89A

regions. They also showed that latent heat ﬂux
decreased during MAM and increased during theother seasons over the Indian region, while it decreased throughout the year over the China region.
However, they did not reveal the mechanism bywhich LUCC impacts precipitation and latent heat
ﬂux. Thus, in the Indian and China regions, the impact and its underlying mechanism of LUCC on
the seasonal change of the local climate have notyet been examined in detail. Therefore, this study
examined the changes in the seasonal cycle of thehydroclimate due to historical LUCC between
1700 and 1850 over the IND and SCH regions andtheir mechanisms, analyzing experiments data similar to Takata et al. (2009). These regions corresponded to the areas investigated by Takata et al.
(2009), who found that precipitation in JJA wassigniﬁcantly decreased. Thus, this study is a followup of Takata et al. (2009) focused on the impactof historical LUCC on the seasonal cycle of thehydroclimate.
2. Experimental design
We conducted two equilibrium experiments inagreement with Takata et al. (2009), 1700VEG
and 1850VEG. These experiments used an atmospheric general circulation model coupled with theland surface scheme MATSIRO (Takata et al.
2003). The model is the atmospheric portion of
MIROC3.2 (K-1 Model Developers, 2004). The
LAI (Leaf Area Index) datasets and the global
distribution of vegetation type in 1700 and 1850
(derived from Hirabayashi et al. 2005) were usedas boundary conditions in each equilibrium experiment (Fig. 1). The LUCC from 1700 to 1850 that
resulted in cultivated land mainly occurred in India,
central China, and Europe (Fig. 1). Other boundary conditions, such as the sea surface temperatureand sea ice, were ﬁxed at the observed monthly
mean averaged from 1981 to 2000, and CO2 was
ﬁxed at 345 ppm, which was its climatologicalvalue in the 1980s. Each experiment was conducted
for 50 years. By analyzing the di¤erence between
1700VEG and 1850VEG, we examined the monthly
mean results for the latter 40-year mean to examine
the e¤ect of extended cultivation between 1700 and1850 on seasonal changes in the hydroclimate.
3. Results
3.1 Common changes
In general, changes in the LAI due to LUCC affect the near surface wind speed and the heat/waterFebruary 2011

R. YAMASHIMA et al.

293

Table 1. Annual mean wind speed at 10 m [m s1 ;vabs10] and LAI [nondimensional].
IND

SCH

1850VEG 1700VEG 1850VEG 1700VEG

Fig. 1. The global distribution of a) the vegetation type in 1700, and b) the change
in vegetation type between 1700 and 1850
(shades). The index numbers in a) are: 0—
ocean; 1—ice sheet; 2—broadleaf evergreen forest; 3—broadleaf deciduous forest& woodland; 4—mixed coniferous &broadleaf deciduous forest & woodland;
5—coniferous forest & woodland; 6—highlatitude deciduous forest & woodland; 7—
wooded C4 grassland; 8—shrubs & bareground; 9—tundra; 10—cropland; and11—desert.

transport between the ground surface and theatmosphere. After extended cultivation from 1700
to 1850 in the IND (75–80 E, 20–22 N) and SCH(106–114 E, 22–28 N) regions, annual LAI values
decreased by 50% and 54%, respectively, and theannual mean wind speed at 10 m increased byapproximately 3.5 m s1 and 4 m s1 , respectively(Table 1).
3.2 Changes in the Indian Subcontinent
The upper bars of Fig. 2a indicate the seasonalvariation of monthly precipitation in the IND region for each experiment. Rainy (over 2 mm day1
precipitation) and dry (under 2 mm day1 precipitation) seasons were reproduced in both experi-

vabs10

4.13

0.64

4.65

0.38

LAI

1.10

2.20

1.29

2.81

ments in this study. After extended cultivation, themonthly precipitation decreased in all months except for February and November. In particular,
this decrease was greater than 1.2 mm day1 in
JJA and October, and greater than 0.8 mm day1
in May. The decrease in JJA was similar to that
discussed in detail by Takata et al. (2009).
We examined each component of evapotranspiration (hereafter EFLUX) in detail (Fig. 2a, lowerbars). EFLUX is equal to the sum of transpiration (hereafter ETFLUX), interception evaporation(hereafter EIFLUX), soil evaporation (hereafter
EBFLUX), and sublimation, although sublimation
was negligible for the region discussed in this study.
ETFLUX and EIFLUX decreased throughout theyear after extended cultivation. In particular, theEIFLUX decrease was over 0.5 mm day1 during
JJA. It is noted that the decrease in EIFLUX was
greatest during the rainy season, while the decreasein ETFLUX was greatest during the dry season. In
contrast, EBFLUX decreased only during MAM
and increased in the other months. As a result, theincrease of EBFLUX partly compensated for thedecrease of EIFLUX and ETFLUX in all months
except for MAM. All evapotranspiration components decreased in 1850 compared to 1700 during
MAM. Examining the sum of these components,
the total EFLUX decreased in most of the months,
although it slightly increased in October. In particular, it markedly decreased by at least 1 mm day1
between the months of March and June; fromMarch to June the di¤erence between 1700 and1850 was double the di¤erence in other months.
This large decrease in June was mostly due tothe decrease of EIFLUX, although EBFLUX increased.
To explain the di¤erences in the response of
EBFLUX during MAM and the other months dueto the historical LUCC, we examined the surface
soil moisture (volumetric water content). Figure 3ashows the seasonal variation of the surface soil
moisture in the IND region for each experiment asfollows: 1) soil moisture accumulated by precipita-

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Journal of the Meteorological Society of Japan

Vol. 89A

Fig. 2. The seasonal variation of evapotranspiration (below; mm day1 ) and precipitation (above; mm day1 ;PRCP). Evapotranspiration is represented by the sum of evaporation from the ground (EBFLUX), transpiration (ETFLUX), and interception evaporation (EIFLUX). The left (right) side vertical bar indicates
1700VEG (1850VEG) for each month. The left (right) side scale corresponds to evapotranspiration (precipitation). a) Indian Subcontinent (75–80 E, 20–22 N), b) South China (106–114 E, 22–28 N).

tion during JJAS (rainy season), 2) soil moisturegradually decreased by evapotranspiration during
the dry season, 3) soil moisture became a minimumin May (immediately prior to rainy season). The
amount of soil moisture throughout the year was
decreased after the period of extended cultivation.
This decrease was particularly noticeable during
the dry season. During MAM, the soil moisture decrease was less than 0.15 m 3 m3 due to extended
cultivation.
In general, the increase in EBFLUX was induced
by LUCC from forest to cultivated land, because

decrease in the LAI induced exposure of the groundsurface and a decrease in surface roughness, hence
an increase in the near surface wind speed. However, the very low soil moisture during MAM induced a decrease in EBFLUX in those months.
During MAM, the largest ratio of decrease in themonthly precipitation occurred in May. To examine the relationship between this precipitation andthe EFLUX decrease in May, we analyzed the total
atmospheric water budget as:
DPW ¼ W þ E  P

ð1ÞFebruary 2011

R. YAMASHIMA et al.

295

Fig. 3. The seasonal variation of surface soil moisture (0–5 cm) [m 3 m 3 ]. a) Indian Subcontinent (75–80 E, 20–22 N), b) South China (106–114 E, 22–28 N).
Table 2. The total atmospheric water budget over the Indian subcontinent during May, and over South China during
March and April. PRCP, EVAP, W.V.Flux, and DPW indicate the precipitation [mm], evapotranspiration [mm],water vapor ﬂux convergence [mm], and the time rate of change of precipitable water [mm], respectively. DIFF indicates 1850VEG minus 1700VEG.
IND in May

SCH during Mar–Apr.

1700VEG

1850VEG

DIFF

1700VEG

1850VEG

DIFF

PRCP

63.2

39.3

23.9

219.3

155.9

63.4

EVAP

80.5

50.4

30.1

196.3

176.4

19.9

W.V.Flux

11.6

8.56

3.04

39.7

6.06

45.76

DPW

5.7

2.54

3.16

16.7

14.442.26

where DPW is the rate of change of precipitablewater, W is the water vapor ﬂux convergence, E isthe evapotranspiration, and P is the precipitation.
An analysis of the total atmospheric water budget
in May showed that the decrease in precipitation
was mostly due to the decrease in EFLUX (Table2). During this season, EFLUX strongly inﬂuences
precipitation because monsoon activity is weak.
Also, water vapor ﬂuxes diverged over the IND region in both experiments. Therefore, the decreasein EFLUX induced by LUCC might dominantlya¤ect the decrease in precipitation. In contrast, thereduced monthly precipitation in October was instead due to the decrease of water vapor ﬂux convergence (not shown).
3.3 Changes in South China
Rainy and dry seasons were also recognizable
in the SCH region (Fig. 2b, upper bars). The rainyseason (monthly precipitation above 2 mm day1 )296

Journal of the Meteorological Society of Japanoccurred from March to October in both experiments. After the period of extended cultivation,
there was reduced precipitation throughout theyear, in addition to the decrease during JJA as
mentioned by Takata et al. (2009). In particular,
the precipitation decrease was over 0.8 mm day1from March to April and from June to July.
As before, we analyzed each component of
EFLUX in the SCH region (Fig. 2b, lower bars).
ETFLUX and EIFLUX decreased throughout theyear, similarly to the IND region. However, EBFLUX increased throughout the year in the SCH
region, which is in contrast to the marked decreaseduring MAM in the IND region. The net changes
in EFLUX were to decrease throughout the year,
from 0.1 to 0.5 mm day1 .
There were little seasonal changes in the soil
moisture, and soil was wet throughout the year inboth experiments (Fig. 3b) due to the relatively
large water supplies from precipitation. The minimum value in soil moisture after extended cultivation was over 0.3 m 3 m3 and was much greaterthan that in the IND region, although soil moisturedecreased throughout the year.
Although a marked decrease of EFLUX in
MAM was not recognized, there was a decrease inmonthly precipitation in March and April that exceeded 1 mm day1 (Fig. 2b, upper bars). From
the atmospheric water budget in March and April,
it was found that the decrease in precipitation was
due to the decrease in water vapor ﬂux convergence
instead of a decrease in EFLUX (Table 2). Thismight have been caused by a pre-monsoon condition in the SCH region. According to Matsumoto(1997), the summer rainy season begins in theinland region of Indochina and extends to South
China in late April to early May; this is caused by
pre-monsoon rainfall under the mid-latitude westerly wind regime. However, the summer monsoon
season begins in south India in late May to early
June, due to the enhancement of convective activity. Thus, precipitation over the SCH region in thespring is inﬂuenced by broad-scale atmospheric circulation. The historical LUCC remotely caused an
anticyclone in March over the mid-China region,and in April over the Sea of Japan, Japan, andwestern Paciﬁc regions (not shown). Therefore, thedecrease in precipitation between March and April
over the SCH region was induced by a decrease inwater vapor ﬂux convergence with the change ofthe broad-scale wind system over China. However,
the mechanism underlying the impact of LUCC on

Vol. 89A

broad-scale atmospheric circulation would be explained in further studies.
4. Discussion
This study investigated the impact of historical
LUCC between 1700 and 1850 on the seasonal cycle of the hydroclimate over the IND and SCH
regions, in addition to its underlying mechanism.
We found a reduction in precipitation and evapotranspiration almost throughout the year in these
two regions. In particular, EFLUX notably decreased during MAM in the IND region, but notin the SCH region. This marked decrease in the
IND region was due to the decrease in EBFLUX.
The decrease of EBFLUX during MAM in the
IND region is explained by the small amount of
rainfall during the dry season, as follows. LUCC
causes EBFLUX to increase from June to February, which led to a decrease in soil moisture duringthat same period. Moreover, there was little watersupply to the ground (i.e., rainfall amount) during
the dry season. Then, as the soil moisture during
MAM was very low, the e¤ect of soil moisturestress on EBFLUX overcame the e¤ect of the LAI
decrease, which usually acts to increase EBFLUX.
Consequently, during MAM, the decrease in EBFLUX was induced by the very low amount of soil
moisture.
However, a marked decrease of EFLUX during
MAM did not appear in the SCH region. Thatwas because the soil remained wet after extended
cultivation due to the relatively large amount of
rainfall during the dry season, compared with theamount of rainfall in the IND region.
The di¤erence in the rainfall amounts during thedry season between the two regions may be causedby the di¤erences in the located climate zone andthe onset date. The IND and SCH regions are located in the Indian summer monsoon (ISM) andthe East Asian summer monsoon (EASM), respectively. The ISM is a tropical monsoon, while the
EASM is a subtropical monsoon (Wang and Lin
Ho 2002). Moreover, the monsoon onset date over
the SCH region is earlier than that over the IND
region, as mentioned in Section 3.3. Consequently,
there is less rainfall during the dry season in the
IND region than there is in the SCH region, leading to an apparent decrease in soil moisture and
EFLUX during MAM caused by LUCC in the
IND region.
The mechanism underlying the impact of LUCC
on EFLUX during the dry season agreed with

February 2011

R. YAMASHIMA et al.

that reported by Voldire and Royer (2004). They
showed that, in the south Amazon and Africa regions, the Soil Wetness Index (SWI) during the dry
season was close to zero after deforestation, which
limited the soil evaporation increase. However, an
increase in soil evaporation during the wet season
compensated for the decrease in evapotranspiration. Thus, their result is consistent with ours.
Lee et al. (2009) showed that the increase of theNormalized Di¤erence Vegetation Index (NDVI)
over the Indian subcontinent in May was signiﬁcantly correlated to the decrease in Indian summer
monsoon rainfall in July, for the period of 1982–
2003. They explained that a reduced July surface
temperature caused by increased vegetation leads
to a reduced land-sea thermal contrast, therefore
causing the monsoon circulation to weaken. Our result showing that a decrease in LAI over the Indian
subcontinent led to a weakened summer monsoon
appears to contradict their result. However, theyexamined an increase in NDVI induced by anincrease in irrigation during 1982–2003. Thus, thechanges in surface roughness in their study were
not so large as in this study, where the historicalland use change from forest to cropland was speciﬁed. In addition, their study covered a time scale oftwo decades, versus 150 years in our study. Therefore, their study was dominated by changes in thesurface heat balance, resulting in a di¤erent response for the monsoon precipitation and circulation.
The coupling strength between the soil moistureand precipitation was examined by Koster et al.
(2004), who conducted several boreal summer (JJA)
simulations. They concluded that ‘‘hot spots,’’
where the coupling strength between soil moistureand precipitation was strong, were located in transition zones between wet and dry climate. This was
because evaporation was suitably high but still sensitive to soil moisture in those locations, and theatmosphere was amenable to the generation of precipitation.
The present study showed that soil moisture,
evapotranspiration, and precipitation notably decreased during MAM due to LUCC in the IND
region; these results agreed with one of the ‘‘hot
spots’’ indicated in Koster et al. (2004). Voldire
and Royer (2004) also showed that soil moistureand soil evaporation notably decreased during thedry season due to deforestation in an African region, which is another ‘‘hot spot.’’ Moreover,Zhao et al. (2001) showed that over India (at a297‘‘hot spot’’), latent heat ﬂux signiﬁcantly decreased
during MAM due to LUCC, while it increased during other seasons. Thus, their results agreed withours only during MAM. This disagreement in the
results for all seasons except MAM was because
the maximum decrease in LAI was much smallerin their study (0.13) than in ours (about 1.0). Findell et al. (2007) showed a decrease in latent heatﬂux during the wet season over northern India (notat a ‘‘hot spot’’) due to LUCC, also in agreementwith our study. However, they showed no change
during the dry season, as the ground was almost
completely dried out. These previous studies implied that the impact of LUCC on the hydroclimate(i.e., changes in soil moisture, soil evaporation, andprecipitation) during the dry season is greatest at
the ‘‘hot spots’’ indicated by Koster et al. (2004).
5. Concluding remarks
This study investigated the impacts and mechanisms of how LUCC, from forest to cultivatedland occurring between 1700 and 1850, a¤ected theseasonal cycle of the hydroclimate over the IND
and SCH regions. Takata et al. (2009) showed thatthe historical LUCC between 1700 and 1850 caused
a reduction in summer (JJA) precipitation overthese regions, with the decrease consistent with themonsoon rainfall trend obtained from proxy data.
The present study further found that in the IND region, EFLUX decreased during most months in theyear, in particularly during MAM after extended
cultivation. However, in the SCH region, EFLUX
discernibly decreased throughout the year. The
varying impacts of LUCC on EFLUX during
MAM between the IND and SCH regions could
be explained by the di¤erent responses of EBFLUX
induced by the unequal rainfall amounts during thedry season in the two regions. Namely, the LAI
decrease due to LUCC would generally cause an increase in EBFLUX; however, the very low rainfall
throughout the dry season in the IND region induced very low soil moisture and hence a reduction
in EBFLUX. In contrast, the precipitation fromMarch to April in the SCH region decreased by
1 mm day1 due to a decrease in water vapor ﬂux
convergence, although EFLUX did not notably
decrease during the same period. This is because
the precipitation in the spring over the SCH region
from March to April is inﬂuenced by broad-scaleatmospheric circulation, i.e., the westerly wind regime.
Consequently, it has been shown that the de-Journal of the Meteorological Society of Japan298

creases in precipitation, evapotranspiration, andsoil moisture were induced throughout the year by
the historical LUCC, and that they were remarkable in the spring in the IND region where there isa strong contrast between the dry and wet seasons.
The regions with (without) such a strong coupling
between precipitation and soil moisture agreed (didnot agree) with the ‘‘hot spots’’ of strong landatmosphere coupling (Koster et al. 2004). These‘‘hot spots’’ have appeared in the transition zones
between wet and dry climates, both in this study
using the historical LUCC and in previous studies
using an extreme LUCC. This implies that the impact of LUCC on the hydroclimate is high at the‘‘hot spots’’. The impact of the historical LUCC between 1700 and 1850, and the associated changes inthe surface energy/water balance and precipitationon the seasonal cycle of the Asian monsoon (including atmospheric circulation) will be discussed
in another paper.
Acknowledgments
This work was partly supported by the Global
Environment Research Fund (B-061 and A-0902)
of the Ministry of the Environment, Japan. We
would like to thank two anonymous reviewers fortheir valuable comments on the manuscript.
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