2012

Contents

Foreword

2

Staff and Organization

3

Research Programme

6

Progress Reports
Division of Regional – Scale Water Cycle Processes

8

Laboratory for Cloud and Precipitation Climatology

8

Division of Global – Scale Water Cycle Variations

10

Laboratory of Satellite Meteorology

10

Laboratory of Satellite Biological Oceanography

12

Laboratory of Bio-Physical Oceanography

16

List of Publications

18

Foreword

HyARC functions as an inter-university collaborative system, which is in many ways
unique in the world. To ensure its research activity, HyARC was accredited as a Joint
Usage/Research Center in April 2010 by the Ministry of Education, Culture, Sports, Science,
and Technology, Japan. The University Project supported a virtual laboratory for diagnosing theearth’s climate system. HyARC has also collaborated with numerous institutions such as the
Research Institute of Humanity and Nature (RIHN) and the National Institute of Information andCommunication Technology (NICT). In the university, HyARC supports the Study Consortiumfor Earth-Life Interactive System (SELIS) which is a cross-cutting virtual organization in
Nagoya University.
As shown in this report, research activity at HyARC is maintained at high level, andmany good results have been published. Three new big project proposals have been accepted:
Development of a coupled ocean-atmosphere non-hydrostatic model for typhoon research,Eco-climate system in Northeastern Eurasia and Southeast Asian tropics: impacts of global
climate change, and Development of a method to comprehend and predict wind conditions
required for offshore wind-power generation. The first one is an extension of the typhoon
simulation in the future global warming era. The second one is also related to the interaction
between forest and climate. The third one is a study on the potential of off-shore wind power
generation. Related to the third one, a new endowed research division “Management of Offshore
Wind Power” will start at the beginning of the next fiscal year. This new division could be oneof the trials to contribute to society with scientific results in HyARC.
While selecting projects and activities, HyARC considers the project’s feasibility, its
significance, and the collaboration requirements. Although HyARC has only 10 permanent staff
members (four professors, three associate professors, and three assistant professors), it supports
many postdoctoral candidates in active research. In addition, HyARC has accepted graduate
students in the Department of Environmental Studies. Three students got doctorate titles and six
students got masters titles. As part of the UNESCO International Hydrology Program (IHP),HyARC has hosted training courses supported by the Japan Trust Fund with a theme of“Precipitation measurement from space and its applications”.

Nakamura Kenji
Director
Hydrospheric Atmospheric Research Center2

Staff and Organization
Research
Division
Board ofCouncilors
Director

Advisory
Board
Board onResearch
Collaboration

Division of Regional-Scale Water Cycle Processes
0Professor

0UYEDA Hiroshi

0Assoc. Professor

0MASUNAGA Hirohiko

0Assist. Professor

0SHINODA Taro

0Designated0Professor

0YASUNARI Tetsuzo

0TSUBOKI Kazuhisa

VL Promotion Unit
0Designated Assist.
0OHIGASHI Tadayasu
0Professor
Division of Global-Scale Water Cycle Variations
0Professor

0NAKAMURA Kenji

0ISHIZAKA Joji

0Assoc. Professor

0KUMAGAI Tomo’omi

0MORIMOTO Akihiko

0Assist. Professor

0MINO Yoshihisa

0FUJINAMI Hatsuki

0Technical Office
0MINDA Haruya0(Technical Center)

0KYUSHIMA Moeto

0Secretary Office

0UTA Ayumi

Administrative Office
0Administrative
0Director

0NAGAO yoshinori

0Administrative
0Vice-Director

0TAKATSUKA Toshio
0General Affairs
0Section
0Accounting Section
0Research Promotion
0Section
0Supplies Section
0Student Affairs
0Section3

Administration
Board of Councilors
NAKAMURA Kenji: Director, Prof., Hydrospheric Atmospheric Research Center, Nagoya University
UYEDA Hiroshi: Prof., Hydrospheric Atmospheric Research Center, Nagoya University
TSUBOKI Kazuhisa: Prof., Hydrospheric Atmospheric Research Center, Nagoya University
ISHIZAKA Joji: Prof., Hydrospheric Atmospheric Research Center, Nagoya University
TANAKA Kentaro: Prof., Graduate School of Science, Nagoya University
TSUJIMOTO Tetsuro: Prof., Graduate School of Engineering, Nagoya University
TAKENAKA Chisato: Prof., Graduate School of Bioagricultural Sciences, Nagoya University
KANZAWA Hiroshi: Prof., Graduate School of Environmental Studies, Nagoya University
MATSUMI Yutaka: Prof., Solar-Terrestrial Environment Laboratory, Nagoya University

Advisory Board●Members from Nagoya University
UYEDA Hiroshi: Prof., Hydrospheric Atmospheric Research Center, Nagoya University
TSUBOKI Kazuhisa: Prof., Hydrospheric Atmospheric Research Center, Nagoya University
ISHIZAKA Joji: Prof., Hydrospheric Atmospheric Research Center, Nagoya University
MASUNAGA Hirohiko: Assoc. Prof., Hydrospheric Atmospheric Research Center, Nagoya University
KUMAGAI Tomo’omi: Assoc. Prof., Hydrospheric Atmospheric Research Center, Nagoya University
MORIMOTO Akihiko: Assoc. Prof., Hydrospheric Atmospheric Research Center, Nagoya University●Members outside Nagoya University
FUJIYOSHI Yasushi: Prof., Institute of Low Temperature Science, Hokkaido University
HANAWA Kimio: Prof., Graduate School of Science, Tohoku University
SUMI Akimasa: Vice President, National Institute for Environmental Studies
FUKUSHIMA Yoshihiro: Designated Prof., Tottori University of Environmental Studies
YAMANAKA Manabu: Principal Scientist, Research Institute for Global Change, Japan Agency for
Marine-Earth Science and Technology
YAMANOUCHI Takashi: Prof., National Institute of Polar Research
TANIGUCHI Makoto: Prof., Research Institute for Humanityand Nature
OKI Riko: Senior Researcher, Earth Observation Research Center, Japan Aerospace Exploration Agency

4

Board on Research Collaboration●Members from Nagoya University
UYEDA Hiroshi: Prof., Hydrospheric Atmospheric Research Center, Nagoya University
ISHIZAKA Joji: Prof., Hydrospheric Atmospheric Research Center, Nagoya University
MASUNAGA Hirohiko: Assoc. Prof., Hydrospheric Atmospheric Research Center, Nagoya University●Members outside Nagoya University
FUJIYOSHI Yasushi: Prof., Institute of Low Temperature Science, Hokkaido University
YAMANAKA Manabu: Principal Scientist, Research Institute for Global Change, Japan Agency for
Marine-Earth Science and Technology
TANIGUCHI Makoto: Prof., Research Institute for Humanityand Nature
OKI Riko: Senior Researcher, Earth Observation Research Center, Japan Aerospace Exploration Agency

5Research Program
Development of remote sensing technology for atmosphere and ocean
observations
The Okinawa Subtropical Environment Remote-Sensing Center, an observation facility in Okinawa,
Japan, was established by the National Institute of Information and Communication Technology (NICT).
These facilities offer the use of full polarimetric Doppler radar (COBRA), 400 MHz wind profiler radar,
Doppler sodar, disdrometers, rain gauges, and ocean radars. In 2005, an interuniversity collaboration wasformed between NICT, Okinawa, and the Hydrospheric Atmospheric Research Center at Nagoya
University, Japan (HyARC). Based on the results of collaboration studies, last fiscal year, the project has
re-started with a new title as "Development of remote sensing technology for atmosphere and ocean
observations" recognizing the demand of new techniques for the atmosphere and ocean remote sensing.
The Japan Aerospace Exploration Agency (JAXA) has developed a new dual Ka-band radar system
for ground validation of the Global Precipitation Measuring Mission (GPM). As one of the atmosphereobservations, rain observation experiment with this radar was conducted in NICT Okinawa withcollaboration of JAXA, and the data were analyzed. For the ocean observation, preliminary study of a
new flexible ocean radar idea has been developed. The new radar may be used for the Tsushima Current
observation.

Research on Coast Circulation, Biological Production and Material Transportwith Remote Sensing
Coastal area is between land and open ocean, and high biological production, active circulation andmaterial transport are maintained by freshwater input with materials from land, including human origin,and by physical variations affected by topography. Because it is difficult to access to oceanic area, unlike
on land, observation by remote sensing is very important. However, satellite sensors covering andresolving typical time and spatial scales in coastal area are limited, and remote sensing of coastal area is
not fully operational because many technical problems still remain.
Scientists in Hydrospheric-Atmospheric Research Center have conducted research on developmentof remote sensing data and analysis of the data in coastal area, such as development of verification
system of primary production, estimation and behavior of chlorophyll and suspended maters in East
China Sea, red tide in Japanese coastal area, circulation in the East China Sea using sea surface
topography and HF radar data. Japan Aerospace Exploration Agency (JAXA) is proposing new ocean
color and sea surface topography sensors, and it is expecting that activities of remote sensing user
community for coastal environment will be expanded.
Research program, “Research on Coast Circulation, Biological Production and Material Transportwith Remote Sensing”, has been started from 2011, and five collaborative research programs were
accepted and conducted following for 2012.
- Standard products of ocean color sensor, MODIS, for remote sensing reflectance and chlorophyll-awere verified in Biwa Lake.
- Use of S-GLI, which is the coming ocean color sensor, of JAXA was discussed. Atmosphericcorrection and in-water algorithm for Ise Bay was developed.
6

- 9th Korea-Japan Workshop on Ocean Color Remote Sensing was held with 6th Program of the East
Asian Cooperative Experiments (PEACE) Ocean Science workshop. Collaboration of research ofocean color and oceanography of east Asian marginal seas was discussed with researchers from Japan,
Korea, Taiwan, Russia, and Malaysia.
- Sea surface height was measured directly between Fukuoka and Busan by Interference Real-Time
Kinematic GPS on a ferryboat, and short term variation with 20-30km eddy shape probably caused bytide was observed.
- Horizontally two dimensional high resolution tidal model for East Asian marginal sea was developed,
and accuracy of semi-diurnal cycle variation was improved with data assimilation.

7

Division of Regional – Scale Water Cycle Processes
Laboratory for Cloud and Precipitation Climatology
A Satellite Study of Tropical Moist Convection and Environmental Variability:
A Moisture and Thermal Budget Analysis
The thermodynamic variability associated with moist convection over tropical oceans is analyzed bymaking use of a variety of satellite sensors including radars (TRMM PR and CloudSat CPR), an infraredand microwave sounder unit (Aqua AIRS/AMSU suite), and microwave radiometer (Aqua AMSR-E) andscatterometer (QuikSCAT SeaWinds) aboard different platforms. Satellite measurements of atmosphericparameters including air temperature, water vapor, cumulus cloud cover, and surface wind arecomposited with respect to the temporal lead or lag from TRMM detected convection to obtainstatistically continuous time series on hourly to daily time scales. AIRS observed temperature andhumidity profiles, representing cloud-cleared sounding, are combined with semi-theoretical estimates of
in-cloud temperature and humidity to construct the large-scale mean field. Those measurements areingested to the moisture and thermal budget equations integrated vertically over each layer separated bycloud base. This strategy makes it possible to evaluate the free-tropospheric (FT) convergence ofmoisture and dry static energy and their vertical flux at cloud base from satellite observations alone. The
main findings include: 1) Vertical moisture transport at cloud base is the dominant source of FT
moistening prior to isolated cumulus development while overwhelmed by horizontal moisture
convergence for highly organized systems (Fig. 1); 2) FT diabatic heating is largely offset on an
instantaneous basis; and 3) FT moistening by convective eddies amounts to a half of the total cloud-basemoisture flux in the background state, while large-scale mean updrafts modulate the variability ofcloud-base flux when highly organized systems develop (Fig. 2). The known correlation between
congestus clouds and FT moisture before deep convection may be accounted for by large-scale mean
moisture updraft rather than congestus eddy moistening.

Fig. 1 ： Free-tropospheric (FT) moisture budget: FT
horizontal moisture convergence (solid), vertical
moisture flux at cloud base (dotted), and FT moisturetendency (shaded).

Fig. 2 ： Sub-cloudlayer (SC) moisture budget:
large-scale mean moisture updraft at cloud base(solid), eddy moisture updraft at cloud base(dotted), and SC moisture tendency (shaded).

Reference: Masunaga, H., 2013: A Satellite Study of Tropical Moist Convection and Environmental
Variability: A Moisture and Thermal Budget Analysis, J. Atmos. Sci., in press.
8

A Satellite Study of the Relationship between Sea Surface Temperature and Column Water
Vapor over Tropical and Subtropical Oceans
The known characteristics of the relationship between sea surface temperature (SST) and column
water vapor (CWV) are reevaluated with recent satellite observations over tropical and subtropicaloceans. Satellite data acquired by the Aqua AMSR-E, AIRS/ AMSU suite, the TRMM PR, and the
QuikSCAT SeaWinds are analyzed together for 7 years from October 2002 to September 2009. CWV isdecomposed into surface relative humidity (RH0), presumably coupled closely to SST, and the water
vapor scale height (Hv) as an index of vertical moisture gradient between the boundary layer and the freetroposphere. Surface relative humidity is climatologically homogeneous across tropical and subtropicaloceans, while the dependence of CWV on SST varies from one region to another (Fig. 3). SST mainly
accounts for the variation of CWV with the water vapor scale height, which is virtually invariant oversubtropical oceans. On the other hand, over tropical oceans, the variability of CWV is explained not only
by SST but also by a systematic change of the water vapor scale height. The regional contrast between
tropical and subtropical oceans is discussed in the context of the regional moisture budget including
vertical moisture transport through convection.

Fig. 3：a) The joint probability density function of SST and CWV (solid line) and RH 0×Hv predicted theoretically (m;dash line). Contour interval is 0.1 %. Thick line shows the maximum occurrence for each SST. b) As a), but SST andsurface water vapor density (ρv,s) and predicted RH0 (%).

Reference: Kanemaru, K. and H. Masunaga, 2013: A Satellite Study of the Relationshipbetween Sea Surface Temperature and Column Water Vapor over Tropical and Subtropical
Oceans, J. Climate, in press.

9Division of Global – Scale Water Cycle Variations
Laboratory of Satellite Meteorology
Dual Ka-band radar experiment for GPM DPR algorithm development
A dual Ka-band radar system has been developed by the Japan Aerospace Exploration Agency(JAXA) for the GPM DPR algorithm development. The dual Ka-radar system which consists of two
identical Ka-band radars can measure both the specific attenuation (k) and the equivalent radarreflectivity (Ze) at Ka-band. Those parameters are important particularly for snow measurement.
Observations using the dual Ka-radar system were performed in Okinawa Island, in Tsukuba, overthe slope of Mt. Fuji, and in Nagaoka, Japan during JFY2011. Along with the data analysis, newobservation at Sapporo aiming to the snow measurement has started in 2012.
The main results are the k-Ze relationships.
For the rain, reasonable k-Ze relationship has
been obtained. The feasibility of total attenuation
in melting layer has been studied. Different k-Ze
relationships have been obtained in snow
observations. Figure 1 shows two examples of
the k-Ze relationships obtained in the experimentin Nagaoka. One is for rain and the other is forwet snow. Compared with rain, wet snow shows
large specific attenuation. Using the difference inradar echoes due to the path length difference
between vertical and slant paths, total
attenuation in the melting layer can be estimated.
The result shows that estimated attenuation is
twice or three times larger of theground-measured rain rates.
Fig. 1 ： k-Ze relationship obtained in snow
observation at Nagaoka. Circle: wet snow, andtriangle: dry snow.

Study of the life cycle of tropical cloud and precipitation systems using MTSAT-1R and
TRMM data
Observation data from the Multi-functional Transport Satellite (MTSAT)-1R and the TropicalRainfall Measuring Mission (TRMM) satellite are analyzed to show statistical view of the cloud life
cycle, including the change of vertical structure of rainfall, over the Maritime Continent and a part of thetropical western Pacific. The analysis focuses on the isolated cold cloud systems, which can beconsidered as fundamental self-organized cloud systems. After identifying temporally connected isolated
cold cloud systems by a cloud tracking procedure, spatiotemporally synchronized TRMM observations
with the cloud systems were searched and various statistics were computed.
Long-lived systems show similar evolution with mesoscale convective systems (MCS), that is, theecho top develops followed by the maximum of cloud and rain areas with decrease of the fraction of
convective rain. The short-lived systems show generally weak rainrates and do not have the expansion ofcloud and rain areas. The precipitation radar (PR) onboard TRMM detects different evolution from thatof the microwave radiometer.
Vertical profiles of the latent heat release reflect the evolution of the precipitation systems.
Convective systems show heating in all layers, but the stratiform systems show heating only in upper
layers. The height of the maximum heating moves upward from about 4 km to 8 km as the precipitation
system evolves. The stratiform system does not show significant change of heating profile, but the area
fraction stratiform rain increases resulting in the total heating profile changes.
10Precipitation characteristics in mountainous region
Precipitation characteristics and circulation, specifically focusing on its relationship with elevation,
are examined over mountainous regions utilizing the Tropical Rainfall Measuring Mission (TRMM)
Precipitation Radar (PR) data, the Japanese 25-year reanalysis (JRA-25), and the Global 30 Arc-Second
Elevation Data Set (GTOPO30). The rainfall-elevation relationship in the central Himalayan region forpre-monsoon and monsoon seasons is analyzed using the 11-year (1998-2008) TRMM PR data of spatial
resolution 0.1 x 0.1 degrees. Variability of precipitation characteristics is also studied for Himalayan
active and break periods. The TRMM product 3B42 is used for identification of active and break periods.
The results indicate a large-scale relationship between rainfall and elevation during both seasons. The
investigation reveals a relatively large amount of rainfall over higher elevations during pre-monsoon
season. During summer monsoon, there appear well-known double peaks of rainfall over the southernslope of the Himalayas. The first peak appears along the Sub-Himalayas, while the second one appears
along the Lesser Himalayas. The former rainfall peak is attributed to fewer heavy rainfall events, and thelatter to frequent but weak rainfall (Fig. 2). It
is suggested that the atmosphere isinsufficiently moist to trigger convections
during the pre-monsoon season, andsufficiently moist during summer monsoon
season.
The
convections
overthe
Sub-Himalayas may moisten the middle layer,
and the water vapor in the atmospherecondenses due to forced lifting along theslope forming the second peak rain band.
Total rain amount is primarily determined by
the frequency of rain. The rain-conditioned
rain rate along the slope monotonicallydecreases with elevation. This shows that the
precipitation occurs due to forced lifting. In
addition, the results show that seasonal
Fig. 2：Precipitation characteristics with ground elevation.
Rectangle: March - May, triangle: June - August。(a): meanvariation of rainfall is rather similar to therain rate, (b): rain frequency, and (c): rain conditioned rain
variation of rainfall characteristics observed
rate.
during active and break periods.

Dry air intrusion in Okinawa area
The Okinawa Islands locates in the subtropics, and sometimes disturbances by westerly waves cause
dry air intrusions. Radiosonde observation data at Okinawa in August 2002 and June 2004 are analyzed
to investigate dry air intrusions. Data also used are sounding data, JRA-25 and ERA-Interim reanalysis
datasets, GMS-5 andGOES-9 geosynchronous meteorological satellite datasets, and Hysplit Trajectory
Model data.
The dry air is produced by extratropical disturbances, and is transported to the Okinawa area.
Subsidence at Okinawa is weak and is not the primary cause of the dry air. Results of a global
non-hydrostatic numerical model (NICAM) are analyzed, and it is found that the Okinawa cases arerather rare cases in which north wind due to westerly waves causes the dry intrusion.

11

Laboratory of Satellite Biological Oceanography
Differences in phytoplankton light absorption between the Tsushima Strait and East China
Sea: Possible influence of Changjiang Discharge
Phytoplankton light absorption is a major factor in determining the optical properties of waters, andit has been widely investigated in the oceanic and coastal regions in the past few decades. The East China
Sea (ECS) receives enormous amounts of freshwater containing very high concentrations of nitrogenfrom Changjiang River in summer. Waters from the ECS as well as the Kuroshio form waters in the
Tsushima Strait (TS). It is suggested that freshwater significantly change optical properties of the area,
while its impact on phytoplankton light absorption is rarely known.
We hypothesize that the Changjiang freshwater may cause distinct phytoplankton absorption in the
ECS. To verify this hypothesis, the variability in phytoplankton absorption of surface and subsurface
chlorophyll a maximum (SCM) samples were analyzed in the TS and ECS, and the differences among
these regions were characterized. Furthermore, to understand the variations and differences ofphytoplankton absorption, changes in the phytoplankton size structure derived from HPLC pigments data,
packaging effect and pigment composition were studied.
The total chlorophyll a (Tchla) specific absorption coefficient (a*ph(λ)) at 440 nm of TS waters
varied inversely with Tchla (P < 0.01, R2 = 0.708) (Fig. 1 (a)). Meanwhile, the fitted power law function
was comparable with that obtained in the global ocean by Bricaud et al. (1995). However, the ECS
waters showed a weak correlation between a*ph(440) and Tchla. The packaging effect index Qa*(440)revealed quite similar variations as the a*ph(440) (Fig. 1 (b)); meanwhile, absorption of all pigments also
showed small but significant changes (data not shown), which confirmed that the packaging effect is the
predominant factor in determination of a*ph(λ).

**

Fig. 1：Variations of a ph(440) (a) and Qa (440) (b) as a function of Tchla in the Tsushima Strait (TS) and East China
Sea (ECS). TS_S, TS_SCM, ECS_S and ECS_SCM represent the TS surface, TS SCM, ECS surface and ECS SCM,
respectively. Black and gray lines indicate fitting functions in the TS and ECS, respectively. Black dashed line
corresponds to the regression of Bricaud et al. (1995).

It is well known that packaging effect is high for large cell but low for small cell. Based on this, thephytoplankton size-fractions could qualitatively explain the variations of Qa*(440) (Fig. 2). The TSwaters showed typical characteristics of the global ocean that pico-plankton was dominant at low Tchla,
nano-plankton at medium Tchla, and micro-plankton at high Tchla, which was highly consistent withthose observed by in the global ocean. Such characteristics, however, could not be found in the ECS.
These results suggested that the algorithms for size-fractions estimation based on the relationship12between Tchla and size-fraction proposed for the global ocean, could be adaptable in the TS but not in
the ECS.
In conclusion, probably due to the influence of Changjiang freshwater, variations in phytoplankton
size structure and pigment composition were different between TS and ECS waters, in turn, thesedifferences might cause significantly different phytoplankton absorption. These findings caution against
us that we should pay more attention to the applications of the general parameterizations for the global
ocean, such as relationships between a*ph(λ) and Tchla affected by phytoplankton size structure as well as
the algorithms proposed based on the relationships, in the coastal waters where is significantly influenced
by freshwater discharge.

Fig. 2：Variations of Tchla size-fractions of micro-, nano- and pico-phytoplankton as a function of Tchla for watersfrom the Tsushima Strait (TS) (a) and East China Sea (ECS) (b). TS_S, TS_SCM, ECS_S and ECS_SCM represent
the TS surface, TS SCM, ECS surface and ECS SCM, respectively. Lines represent the 5-point running average.

Verification and correction of data of satellite ocean color sensors SeaWiFS and MODIS
for long-term analysis of chlorophyll-a in Ise Bay.
Environment of Ise Bay, an inner bay with large volume of freshwater input, became worse since
1970s, and many red tides and anoxic condition has been observed. Recently, nutrient supply was
reduced to improve the conditions; however, anoxic water is still observed. Furthermore, decrease offisheries catch has been worried because of the oligotrophication and climate change. In order tomonitor the change of the ecosystem, it is expected to use satellite remote sensing technology to observe
phytoplankton biomass, chlorophyll-a (Chl-a). However, abundant suspended and dissolved color
materials and smog may influence to the accuracy of the data. It is also pointed out that the one satellite
cannot monitor for a long time. In this study, accuracy and continuation of Chl-a data of Ise Bay from13

satellite ocean color sensors, SeaWiFS and MODIS/Aqua, was verified, and the satellite Chl-a data was
improved.
Chl-a from SeaWiFS and MODIS showed significant positive correlation with in situ data but
overestimated about 2-fold. The overestimation was large (3.5-fold) when remote sensing reflectance at
412nm (Rr412) was negative. Error of MODIS Rrs was small and large at 547 and 412 nm,
respectively. The error of atmospheric correction was large in spring, and Kosa may be one of thecauses. Chl-a estimated from in situ Rrs was closer to in situ Chl-a than satellite Chl-a; however, it wasoverestimated 2-fold and underestimated 1/2-fold at less and greater than 4 mg m-3 of Chl-a, respectively.
These results suggested that the error of satellite Chl-a data in Ise Bay was caused by both atmosphericcorrection, specifically at short wavelength, and in-water algorithm. On the other hand, MODIS Chl-a
was larger than SeaWiFS Chl-a for more than 3 mg m-3. The difference between the sensors caused by
the difference of wavelength of Rrs used for the in-water algorithm of Chl-a estimation.
From those results, negative Rrs412 was set to zero with fixed Rrs547 or Rw555 with small error,
across the line between Rrs412 to Rrs547 or Rrs555. Furthermore, Rrs ratio between the different
sensors were corrected by regression, and anther regression model was made between the Rrs ratio and insitu Chl-a. The overestimation of satellite Chl-a was corrected to make accurate and consistent data of
the sensors.

Fig. 3：MODIS Rrs412 (a), NASA standard Chl-a (b), and corrected Chl-a (c) on April 29, 2004. SeaWiFS Rrs412 (d),NASA standard Chl-a (e), and corrected Chl-a (f). Difference between MODIS and SeaWiFS for standard Chl-a (g)and corrected Chl-a (h).

Seasonal variations in nitrogen isotopic ratio of the sinking particles in the Western North
Pacific Subtropical Gyre
A part of the particles produced in the upper ocean by phytoplankton is vertically carried to the deep
layer via sinking. This process plays a major role in CO2 sequestration to the deep sea, is known as the14

biological pump. In the subtropical regions that cover 60 percent of the entire oceans, the primary
productivity is mainly limited by a supply of nutrients. Then the stable nitrogen isotopic signal ( 15N) of
particulate organic matter can provide insights into factors controlling the efficiency of biological pumpin the subtropics since it reflects the trophic condition when the organic matter was formed. Here, we
discuss a time-series change in trophic condition at the upper layer of the western north subtropical
Pacific by analyzing 15N of the sinking particles collected by the moored sediment traps deployed at 200
and 500 m depth of the station S1 (30°N, 145°E) during February 2010 to July 2011.
The 15N value is similar among particles from 200 and 500 m depth, with the average of 4.2 permil
for the experimental period. 15N signal marked a minimum (2.3 permil) during February to March andgradually increased to ~6 permil in Jun (Fig. 4), suggested that nutrients supplied due to winter mixing
were gradually consumed by phytoplankton during spring. In July, 15N showed a decline to around 4~5
permil and became stable subsequently, implying that nutrients newly supplied into the euphotic zone insummer. As this process of nitrogen supply, two possibilities are considered: the first is due to a
disturbance of upper waters by episodic, cyclonic eddies and the second is a biological fixation of N 2.
Another observations on the hydrographic cruise during October 2010 provided the vertical distributionof 15N of nitrate with relatively low values in upper layer (Fig. 5), which suggests that an atmospheric N2
fixed might contribute to new N input. Also this presumption can account for the fact that the averaged
15
N of particles was lower than that of nitrate (5~6 permil) in deep sea (Fig. 5). The summer 15N declines
were found in 2010 and 2011, suggesting that such new N inputs to the ecosystem in the upper layer may
occur every summer and sustain productivity and organic carbon flux in the oligotrophic subtropical
Pacific.
15

Fig.4：Temporal changes in N of sinking
particles at the depth of 200 m (open circle)
and 500 m (filled circle) of the station S1, andthe satellite-derived sea surface temperature(SST: dashed line) that was 13 days-moving
15
averaged. Triangles indicate the data for Nof particles collected by the short-term,
shallow-layers (100-200 m) sediment traps.

Fig.5 ： Vertical distributions of nitrate concentrations (open15
diamond) and N (filled diamond) at the station S1 during October2010 (Abe and Kaiser, unpublished data).

15

Loboratory of Bio-Physical Oceanography
Variability in Kuroshio axis in the northeast Taiwan
The Kuroshio flows northward east of Taiwan, then turns to northeastward along shelf sloop in thenortheast of Taiwan, and enters into the East China Sea. Since the Kuroshio variations in the northeast of
Taiwan strongly relate to water mass formation in the shelf, variation in volume transport of the
Tsushima Warm Current, and nutrients supply from Open Ocean to the shelf, many oceanographers haveconducted research. Although it is difficult to capture the spatially and temporally variation of Kuroshio
based on observation, most of researches were carried out by mooring at a few points, snapshothydrographic observations, and numerical studies. In the present study, we analyzed the long-term sea
surface current data with spatial resolution of 7 km and temporal resolution of 30 min. measured by theLong Range Ocean Radar (LROR) which was installed at Yonaguni and Ishigaki Islands in 2001 by
NICT.
In order to derive currents of the Kuroshio from LROR data, tidal currents and wind-driven current
were removed. The data were daily averaged and were applied 5 days running mean. We made theKuroshio axis dataset from the processed current data based on method of Ambe et al. (2004).
Figure 1a shows frequency distribution of the Kuroshio axis position at 10 sections that wascalculated from all data for 8 years. It is found that highest frequencies appear near shelf edge and theKuroshio flows along the shelf sloop with the characteristics of geostrophic current. However, relatively
high frequencies were seen in the shelf. This fact suggests that the Kuroshio moves to the shelf frequently.
Frequency distribution in summer and winter are shown in Fig. 1a, b. The Kuroshio in summer flowed
northeastward stably along the shelf edge as reported by previous studies. On the other hand, according
to the previous studies the Kuroshio in winter flows on the shelf. However our result indicated that highfrequency of the Kuroshio axis position was not only along the shelf edge but also in the shelf. Namely, it
was found that there were 2 modes of the Kuroshio axis position in winter. We analyzed time series of
the Kuroshio axis position in winter. Although previous studies suggested that the Kuroshio in wintershifts to the north due to northeast monsoon or sea surface cooling, we could not recognize such therelations between the Kuroshio axis variation and the factors.

Fig. 1：Frequency distribution of the Kuroshio axis position (a) for 8 years, (b) in summer (July – August),
and (c) in winter (December – February).

Investigation of air-sea flux and its variation over the Kuroshio Extension region
The Kuroshio Extension region (KE), where is characterized by active air-sea interactions, is one of
key regions for better understanding of climate around Japan. Thus, the investigation of air-sea flux andits variation over the KE is an important issue. Recently, many in-situ observations have been conductedin the KE region along with interests of many researchers. This study analyzes a set of in-situ observation
data of air-sea flux obtained from the JKEO buoy for air-sea interaction studies. The data set has very16

high-temporal resolution (10 minutes interval)
Fig. 2 ： Composite
and it is expected to better understand oftime series of upward
high-frequency variation of air-sea flux. Firstly,
air-sea net heat flux
for two wind regimes:
we investigated the most dominant air-sea heat
northerly (black) andflux variability that has time scales of several
southerly (gray).
days. As a result, that variations wereaccompanied with changes in wind direction
because of passages of atmospheric disturbances.
Moreover, the contrastive characteristics in the air-sea heat flux variability between the two winddirection regimes were quantitatively clarified (see Fig.2).

Interannual variation in the third branch of the Tsushima Warm Current path(a)(b)
In order to investigate the Tsushima Warm Current (TWC)
paths, we used satellite altimeter and Argos buoy trajectory data tocreate monthly average sea surface dynamical height (SSDH) andcurrent field data which has a higher spatial-temporal resolution
compared to the ship observed data. We focused on the variation of
the third branch of the TWC (TBTWC) which flows along the east
coast of Korea to the northward. We recognized that TBTWC has
not only seasonal variation but also has a large interannual
variation especially in summer (Fig. 3).
Fig. 3：TBTWC path pattern in
Mode2(9.5%)
To examine the interannual variation of the TBTWC, we
summer:(a) offshore pattern, July 2000,
applied the empirical orthogonal function (EOF) analysis to the(b) northward pattern, July 2009.
SSDH data. The result shows the first EOF mode explains 11 % of
the total variance and has a pattern of current speed variation. In this pattern, the turning point of the
TBTWC is constantly around 38˚N. On the other hand, the second EOF mode explains 10 % of the total
variance and indicates a large variation pattern of the turning point of the TBTWC (Fig. 4).
We made interannual variation data by reconstructing of the second EOF mode (hereafter EOF
monthly data). Then we compared the EOF monthly data to net heat flux over the Japan Sea in winter(average from January to March). As a result, the EOF monthly data in winter or in April through July
have high correlation (over 0.6) with the winter net heat flux. Therefore, it is suggested that when winternet heat flux is large (small) over the Japan Sea, TBTWC become offshore (northward) current pathpattern.
(a)(b)

Fig. 4：Second EOF mode: (a) spatial structure of second
EOF mode, (b)temporal variation of second EOF mode.
(Unit: m)

17

List of Publications*:Staffs, students and research fellows in the HyARC.
1.

Akter, N. and K. Tsuboki*
Numerical simulation of Cyclone Sidr using a cloud-resolving model: Characteristics and formation
process of an outer rainband. Monthly Weather Review, 140(3), 789-810, doi:10.1175/2011MWR3643.1,
2012.

2.

Fukutomi, Y., K. Masuda and T. Yasunari*
Spatiotemporal structures of the intraseasonal oscillations of precipitation over northern Eurasia during
summer. International Journal of Climatology, 32(5), 710-726, doi:10.1002/joc.2293, 2012.

3.

Hirose, M., S. Shimizu, R. Oki, T. Iguchi, D. A. Short and K. Nakamura*
Incidence-angle dependency of TRMM PR rain estimates. Journal of Atmospheric and Oceanic
Technology, 29(2), 192–206, doi:10.1175/JTECH-D-11-00067.1, 2012.

4.

Ichikawa, H., H. Masunaga*, Y. Tsushima and H. Kanzawa
Reproducibility by climate models of cloud radiative forcing associated with tropical convection. Journalof Climate, 25(4), 1247–1262, doi:10.1175/JCLI-D-11-00114.1, 2012.

5.

Ichikawa, H., H. Masunaga*, Y. Tsushima and H. Kanzawa
Analysis of cloud properties associated with tropical convection in climate models and satellite data.
Journal of the Meteorological Society of Japan, 90(5), 629-646, doi:10.2151/jmsj.2012-504, 2012.

6.

Igarashi, Y.*, N. Tanaka, K. Tanaka, T. Yoshifuji, C. Sato, C. Tantasirin, and M. Suzuki
Seasonality of water and carbon dioxide exchanges at a teak plantation in northern Thailand.
Ecohydrology, 6(1), 125–133. DOI:10.1002/eco.284, 2012.

7.

Imaoka, K.* and K. Nakamura*
Statistical analysis of the life cycle of isolated tropical cold cloud systems using MTSAT-1R and TRMM
data. Monthly Weather Review, 140(11), 3552–3572, doi:10.1175/MWR-D-11-00364. 1, 2012.

8.

Jang, M., D.-I. Lee, C.-H. You, D.-S. Kim, M. Maki, J.-H. Jeong and H. Uyeda*
Quantitative precipitation estimates from radar reflectivity corrected by the SMA method. AtmosphericResearch, 104-105, 111-118, doi:10.1016/j.atmosres.2011.08.004, 2012.

9.

Jang, S.-M., J.-Y. Gu, D.-I. Lee, J.-H. Jeong, S.-H. Park and H. Uyeda*
An analysis of precipitation systems developed near Jeju Island in Korea during the summer monsoon,
2006. Journal of the Korean Earth Science Society, 33(5), 377-394, 2012.

10. Kajikawa, Y.*, T. Yasunari*, S. Yoshida and H. Fujinami*
Advanced Asian summer monsoon onset in recent decades. Geophysical Research Letters, 39(3), L03803,
doi:10.1029/2011GL050540, 2012.
11. Kumagai, T.* and A. Porporato
Strategies of a Bornean tropical rainforest water use as a function of rainfall regime: isohydric or
anisohydric? Plant, Cell & Environment, 35(1), 61-71, doi:10.1111/j.1365-3040.2011.02428.x, 2012.
12. Kumagai, T.* and A. Porporato
Drought-induced mortality of a Bornean tropical rainforest amplified by climate change. Journal ofGeophysical Research Biogeosciences, 117, G2, G02032, doi:10.1029/2011JG001835, 2012.
13. Kumagai, T.* and T. Kume
Influences of diurnal rainfall cycle on CO2 exchange over Bornean tropical rainforests. EcologicalModelling, 246, 91-98, doi:10.1016/j.ecolmodel.2012.07.014, 2012.

18

14. Lee, K.-O.*, H. Uyeda*, S. Shimizu and D.-I. Lee
Dual-Doppler radar analysis of the enhancement of a precipitation system on the northern side of Mt.
Halla,

Jeju

Island,

Korea

on

6

July

2007.

AtmosphericResearch,118,

133–152,

doi:10.1016/j.atmosres.2012.06.017, 2012.
15. Li, W., T. Hiyama, and N. Kobayashi*
Seasonal variations of the surface fluxes and surface parameters over the loess plateau in China,
Atmospheric and Climate Sciences, 2013, 3, 111-120, doi:10.4236/acs. 2013.31013, 2012.
16. Liu, C., Q. Wang, Y. Yang, K. Wang, Z. Ouyang, Y. Li, A. Lei and T. Yasunari*
Recent trends of nitrogen flow of typical agro-ecosystems in China–major problems and potential
solutions. Journal of the Science of Food and Agriculture, 92(5), 1046-1053, doi:10.1002/jsfa.4725,
2012.
17. Liu, Y., T. Hiyama, T. Yasunari*, and H. Tanaka
A nonparametric approach to estimating terrestrial evaporation: Validation in eddy covariance sites.
Agricultural and Forest Meteorology, Volume 157, 15 May 2012, Pages 49-59, 2012.
18. Maejima, Y.* and K. Iga
The time evolution of meso-scale disturbances in the atmosphere caused by frontal instability.
Theoretical and Applied Mechanics Japan, 60, 183-191, 2012.
19. Masunaga, H.*
A satellite study of the atmospheric forcing and response to moist convection over tropical andsubtropical oceans. Journal of the Atmospheric Sciences, 69(1), 150-167, doi:10.1175/JAS-D-11-016.1,
2012.
20. Masunaga, H.*
Short-term versus climatological relationship between precipitation and tropospheric humidity. Journal of
Climate, 25(22), 7983–7990, doi:10.1175/JCLI-D-12-00037.1, 2012.
21. Moon, J.-H., N. Hirose and A. Morimoto*Green's function approach for calibrating tides in a circulation model for the East Asian marginal seas.
Journal of Oceanography, 68(2), 345-354, doi:10.1007/s10872-011-0097-1, 2012.
22. Morimoto, A.*, A. Watanabe, G. Onitsuka, T. Takikawa, M. Moku and T. Yanagi
Interannual variations in material transport through the eastern channel of the Tsushima/Korea Straits.
Progress in Oceanography, 105, 38–46, doi:10.1016/j.pocean.2012.04.011, 2012.
23. Morotomi, K., T. Shinoda*, Y. Shusse, T. Kouketsu*, T. Ohigashi*, K. Tsuboki*, H. Uyeda* and I.
Tamagawa
Maintenance mechanisms of a precipitation band formed along the Ibuki-Suzuka Mountains on
September 2-3, 2008. Journal of the Meteorological Society of Japan, 90(5), 737-753,
doi:10.2151/jmsj.2012-511, 2012.
24. Nomura, M. and K. Tsuboki*
Numerical study of precipitation intensification and ice-phase microphysical processes in typhoon spiralband. Journal of the Meteorological Society of Japan, 90(5), 685-699, doi:10.2151/jmsj.2012-508, 2012.
25. Nomura, M., K. Tsuboki* and T. Shinoda*
Impact of sedimentation of cloud ice on cloud-top height and precipitation intensity of precipitation
systems simulated by a cloud-resolving model. Journal of the Meteorological Society of Japan, 90(5),791-806, doi:10.2151/jmsj.2012-514, 2012.

19

26. Sato, T., T. Oda, Y. Igarashi*, M. Suzuki, and Y. Uchiyama
Circumferential sap flow variation in the trunks of Japanese cedar and cypress trees growing on a steep
slope. Hydrological Research Letters, 6, 104-108. DOI: 10.3178/ hrl. 6. 104, 2012.
27. Shrestha, D.*, P. Singh and K. Nakamura*
Spatiotemporal variation of rainfall over the central Himalayan region revealed by TRMM Precipitation
Radar. Journal of Geophysical Research, 117, D22, D22106, doi:10.1029/2012JD018140, 2012.
28. Son, Y. B., W. D. Gardner, M. J. Richardson, J. Ishizaka*, J.-H. Ryu, S.-H. Kim and S. H. Lee
Tracing offshore low-salinity plumes in the Northeastern Gulf of Mexico during the summer season byuseofmultispectral

remote-sensing

data.

Journalof

Oceanography,

68(5),

743-760,

doi:10.1007/s10872-012-0131-y, 2012.
29. Sun, W.-Y., O. M. Sun and K. Tsuboki*
A modified atmospheric non-hydrostatic model on low aspect ratio grids. Tellus, 64A, 17516,
doi:10.3402/tellusa.v64i0.17516, 2012.
30. Suzuki, K., K. Shimizu, T. Ohigashi*, K. Tsuboki*, S. Oishi, S. Kawamura, K. Nakagawa, K. Yamaguchi
and E. Nakakita
Development of a new videosonde observation system for in-situ precipitation particle measurements.
Scientific Online Letters on the Atmosphere (SOLA), 8, 1-4, doi:10.2151/sola.2012-001, 2012.
31. Takahashi, D., A. Morimoto*, T. Nakamura, T. Hosaka, Y. Mino, V. H. Dang and T. Saino
Short-term flow and water temperature fluctuations in Sagami Bay, Japan, associated with variations of
the Kuroshio during the non-large-meander path. Progress in Oceanography, 105, 47–60,
doi:10.1016/j.pocean.2012.04.012, 2012.
32. Takikawa, T., G. Onitsuka, K. Fukudome, J.-H. Yoon and A. Morimoto*
Seasonal variation of counterclockwise eddies downstream of the Tsushima Islands. Progress in
Oceanography, 105, 30–37, doi:10.1016/j.pocean.2012.04.006, 2012.
33. Tanaka, K., H.-J. Kim, K. Saito, H. G. Takahashi, M. Watanabe, T. Yokohata, M. Kimoto, K. Takata andT. Yasunari*
How have both cultivation and warming influenced annual global isoprene and monoterpene emissions
since

the

preindustrial

era?

Atmospheric

ChemistryandPhysics,

12(20),

9703-9718,

doi:10.5194/acp-12-9703-2012, 2012.
34. Tripathy, S. C.*, J. Ishizaka*, E. Siswanto, T. Shibata and Y. Mino*
Modification of the vertically generalized production model for the turbid waters of Ariake Bay,
southwestern Japan. Estuarine, Coastal and Shelf Science, 97, 66-77, doi:10.1016/j.ecss.2011.11.025,
2012.
35. Wang, C.-C., H.-C. Kuo, Y.-H. Chen, H.-L. Huang, C.-H. Chung and K. Tsuboki*
Effects of asymmetric latent heating on typhoon movement crossing Taiwan: The case of Morakot (2009)
withextremerainfall.

Journalofthe

Atmospheric

Sciences,69(11),

3172–3196,

doi:10.1175/JAS-D-11-0346.1, 2012.
36. Xue, B.-L., H. Komatsu, T. Kumagai*, A. Kotani, K. Otsuki and T. Ohta
Interannual variation of evapotranspiration in an eastern Siberian larch forest. Hydrological Processes,
26(15), 2360-2368, doi:10.1002/hyp.9195, 2012.
37. Yamaguchi, H., H.-C. Kim, Y. B. Son, S. W. Kim, K. Okamura, Y. Kiyomoto and J. Ishizaka*
Seasonal and summer interannual variations of SeaWiFS chlorophyll a in the Yellow Sea and East China
Sea. Progress in Oceanography, 105, 22-29, doi:10.1016/j.pocean.2012.04.004, 2012.

20

38. Yanase, W., M. Satoh, H. Taniguchi and H. Fujinami*
Seasonal and intraseasonal modulation of tropical cyclogenesis environment over the Bay of Bengal
duringtheextendedsummermonsoon.

doi:10.1175/JCLI-D-11-00208.1, 2012.

21

Journalof

Climate,25(8),

2914–2930,

Hydrospheric Atmospheric Research Center (HyARC)
Nagoya University
Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan

Office:Telephone: +81-52-789-3466
Facsimile: +81-52-788-6206
Home Page: http://www.hyarc.nagoya-u.ac.jp

The 2012 Annual Report was published November
2013 by the Hydrospheric Atmospheric Research Center(HyARC) Nagoya University.