Annual Report

Hydrospheric Atmospheric Research Center(HyARC)
Nagoya University

2009drospheric tmosphericesearch enter(HyARC)

2009
NAGOYA
UNIVERSITY

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Contents
Foreword

2

Staff and Organization

3

Research Programme

6

Progress Reports
Projects
Division of Regional – Scale Water Cycle Processes
Laboratory of Meteorology
Laboratory for Climate System StudyLaboratory for Cloud and Precipitation Climatology

Division of Global – Scale Water Cycle Variations
Laboratory of Satellite Meteorology
Laboratory of Eco-Hydrometeorology
Laboratory of Satellite Biological Oceanography
Laboratory of Bio-Physical Oceanography

List of Publications

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8
12
12
18
22
24
24
26
28
32
34

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Foreword
The Hydrospheric Atmospheric Research Center (HyARC) at Nagoya University
was established nine years ago to promote research on the global water cycle, one ofthe primary components of the Earth system. Research on the global water cycle
requires strong and extensive collaboration among science and application communities, and hence HyARC functions as an inter-university collaborative system, inmany ways unique in the world.
HyARC has initiated numerous projects and activities. Prominent among these is
the International Project Office of the Global Energy and Water Cycle Experiment(GEWEX) Asian Monsoon Experiment (GAME), led by Prof. T. Yasunari, and its
various follow-on projects. Additional work has been supported by the following:
Grants-in-Aid for Scientific Research; Core Research for Evolutional Science andTechnology (CREST) of the Japan Science and Technology Corporation (JST); Global Environment Research Fund; Innovative Program of Climate Change Projection
for the 21st Century; and more. In addition, funding from the Ministry of Education,
Culture, Sports, Science and Technology, Japan, supported construction of a multiparameter radar system to study water circulation, and funding from the Inter-University Project supported a virtual laboratory for study of the earth's climate diagnostics.
HyARC has also collaborated with numerous institutions, such as the ResearchInstitute of Humanity and Nature (RIHN) and the National Institute of Information
and Communication Technology (NICT). As partial contribution to the UNESCO
International Hydrology Programme (IHP), HyARC has conducted training courses,
funded by the Japan Trust; this year’s course was on satellite remote sensing of atmospheric constituents.
In selecting projects and activities, HyARC considers project feasibility, significance,and collaboration requirements. We currently fund 3 research projects and 4 workshops. Although HyARC’s permanent staff numbers only 11 (4 professors, 4 associate
professors, and 3 assistant professors), we also support many postdoctoral candidates
in active research. In addition, we have accepted graduate students in the Departmentof Environmental Studies.
Nagoya University has adopted a flexible management system that emphasizes
accountability yet encourages research publications and outreach programs. Accordingly, and spurred by comments from an outside evaluation committee, we herewith
propose to establish a large-scale national/international facility, and a new organization to address its social requirements.

Uyeda Hiroshi
Director
Hydrospheric Atmospheric Research Center

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Staff and Organization
Research
Division
Board ofCouncilors

Director

Division of Regional – Scale Water Cycle Processes
Professor

UYEDA Hiroshi

YASUNARI Tetsuzo

Assoc. Professor

TSUBOKI Kazuhisa

MASUNAGA Hirohiko

Assist. Professor

SHINODA Taro

FUJINAMI Hatsuki

VL Promotion Unit
Advisory
Board

Designated
Assist. Professor

OHIGASHI Tadayasu

Division of Global – Scale Water Cycle Variations

Board onResearch
Collaboration

Professor

Assoc. Professor

NAKAMURA Kenji

ISHIZAKA JojiHIYAMA Tetsuya

MORIMOTO Akihiko

TANAKA Hiroki
Assist. Professor

MINO Yoshihisa

Technical Office (Technical Center)

MINDA Haruya

Secretary Office

IWAMOTO Keiko

KAWAKAMI Shinnosuke

Administrative Office
Administrative TANIGUCHI Tetsuya
Director
Administrative SUGIE Osamu
Vice-Director
General Affairs
SectionAccounting
Section

Supplies
SectionStudent Affairs
Section01-1.HyARC2009-E.indd 3

TAKADA Yoshimasa

KOJIMA Miki

HORINOUCHI Nobutaka

TANAKA Mihoko

NISHIKAWA Sachi

Yamada Yuichi

MIYANO Koji

MANABE Ken

TOIDA Machiko
KAWAI Akira

ONO Yoko

KONDO Kunihiro

10.10.26 6:13:47 PMAdministration
Board of Councilors
UYEDA Hiroshi: Director, Prof., Hydrospheric Atmospheric Research Center
YASUNARI Tetsuzo: Prof., Hydrospheric Atmospheric Research Center
NAKAMURA Kenji: Prof., Hydrospheric Atmospheric Research Center
ISHIZAKA Joji: Prof., Hydrospheric Atmospheric Research Center
TANAKA Kentaro: Prof., Graduate School of Science
TSUJIMOTO Tetsuro: Prof., Graduate School of Engineering
OTA Takeshi: Prof., Graduate School of Bioagricultural Sciences
KANZAWA Hiroshi: Prof., Graduate School of Environmental Studies
MATSUMI Yutaka: Prof., Solar-Terrestrial Environment Laboratory

Advisory Boardl Members from Nagoya Unisversity

YASUNARI Tetsuzo: Prof., Hydrospheric Atmospheric Research Center
NAKAMURA Kenji: Prof., Hydrospheric Atmospheric Research Center
ISHIZAKA Joji: Prof., Hydrospheric Atmospheric Research Center
TSUBOKI Kazuhisa: Assoc. Prof., Hydrospheric Atmospheric Research Center
MASUNAGA Hirohiko: Assoc. Prof., Hydrospheric Atmospheric Research Center
HIYAMA Tetsuya: Assoc. Prof., Hydrospheric Atmospheric Research Center
MORIMOTO Akihiko: Assoc. Prof., Hydrospheric Atmospheric Research Centerl 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: Prof., Integrated Research System for Sustainability Science,
The University of Tokyo
FUKUSHIMA Yoshihiro: Prof., Tottori University of Environmental Studies
YAMANAKA Manabu: Senior Scientist, Institute of Observational Research 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 Humanity and Nature
OKI Riko: Senior Researcher, Earth Observation Research Center, Japan Aerospace
Exploration Agency

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Board on Research Collaborationl Members from Nagoya University

NAKAMURA Kenji: Prof., Hydrospheric Atmospheric Research Center
ISHIZAKA Joji: Prof., Hydrospheric Atmospheric Research Center
HIYAMA Tetsuya: Assoc. Prof., Hydrospheric Atmospheric Research Centerl Members outside Nagoya University

FUJIYOSHI Yasushi: Prof., Institute of Low Temperature Science, Hokkaido
University
YAMANAKA Manabu: Senior Scientist, Institute of Observational Research for
Global Change, Japan Agency for Marine-Earth Science andTechnology
TANIGUCHI Makoto: Prof., Research Institute for Humanity and Nature
OKI Riko: Senior Researcher, Earth Observation Research Center, Japan Aerospace
Exploration Agency

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 Research Programme
Water circulation studies using new polarimetric radar
A new polarimetric (multi-parameter) radar was installed at the Hydrospheric Atmospheric Research Center (HyARC), Nagoya University, in 2007. Since installation, this equipment has been promoting new studies on clouds and precipitation, and aiding in the development of new observational and analytical techniques that are essential for studies on water
circulation. Such observational and analytical techniques, as well as data assimilation methods, are necessary for the utilization of observational data from the new radar and for amalgamation of the data with a cloud-resolving model.
This research plan aims at promoting new research on water circulation using the newpolarimetric radar as well as existing radar sets. In concrete terms, we examine and implement observational data of weather phenomena and physical processes of cloud and precipitation systems. We aim at developing new parameters for multi-parameter radar observation and data analysis and new display methods for radar data. We will develop software andoperational routines for the radar from physical and engineering viewpoints in collaboration
with researchers participating in this study project.

Diurnal processes of convection/precipitation systems in the climate
SystemDiurnal variation in convection and precipitation is a prominent meteorological feature,
particularly in the tropics/subtropics and monsoon regions. Energy, water, and momentum
exchanges through the diurnal cycle between the earth surface, atmospheric boundary layer,
and free atmosphere play a crucial role in global climate models (GCMs) and still cannot
reproduce a realistic diurnal cycle in convection/precipitation, including systematic errors in
the models.
This research plan aims to clarify the regionality and seasonality of diurnal processes
based on TRMM, other remote sensing data, and in-situ observational data from rain gauge
stations. Cloud resolving models (e.g., CReSS and WRF) and other regional models are also
used to elucidate systematic errors in the climate model due to the diurnal cycle. These studies can contribute to the ongoing international project “MAHASRI.” We aim to promote studies on the diurnal process of convection/precipitation in the climate system in Japan.
On December 19, 2007, a domestic workshop, co-hosted by MAHASRI, was held in Hakone.
Studies on the diurnal variation of cloud/precipitation systems, including the relationshipwith terrain, synoptic conditions and intraseasonal variation, were presented. These studies
covered areas from the Tibetan Plateau to the Maritime continents. In total, 14 participantspresented new scientific results and there was a lively discussion with many participants inthe workshop. Future issues on diurnal cycles were also discussed.

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10.10.26 6:13:48 PMStudy of atmospheric and oceanic climate over Okinawa Islands and its
surroundings
The National Institute of Information and Communication Technology (NICT) establishedan observation facility in Okinawa, Japan (Okinawa Subtropical Environment Remote Sensing Center). The facilities provided include a full polarimetric Doppler radar (COBRA), 400MHz wind profiler radar, Doppler sodar, disdrometers, rain gauges, and ocean radars. In 2005,
an interuniversity collaboration between NICT Okinawa and the Hydrospheric AtmosphericResearch Center at Nagoya University, Japan (HyARC) started.
The spatial and temporal variations in the Kuroshio Current around the Okinawa Islands
were studied using an ocean radar and raindrop-size-distribution characteristics were determined by COBRA polarimetric data. The studies on ocean currents and precipitation are
separate; however, if merged, the ocean–atmosphere interaction can be studied. New techniques were developed to study the atmosphere and the oceans (e.g., a flexible ocean radar
and a new acoustic speaker system for the radio acoustic sounding system (RASS). Calibration techniques of satellite measurements were also investigated.
NICT is an agency for sensor development using radiowaves, and HyARC organizes theusers for exploring deeper and wider applications. Here, the collaboration was well coordinated, and many interesting results were obtained. However, for studying the climate, full
utilization of the recorded data is not yet attained. Based on the deep understanding of sensors, a thorough analysis of the data should be conducted.

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10.10.26 6:13:48 PMProgress Reports
Projects
Formation of a virtual laboratory for diagnosing the earth’s climate system
Two polarimetric radars installed in November 2007 started full-scale operation in 2009,
after about a year of preparation. In this report, HyARC VL (Virtual Laboratory) Office’s efforts in the operation and study of the polarimetric radars in 2009 are summarized.
Long-term observations at Nobi Plain were conducted in 2009. The main radar system,
which is called KIN radar, was installed on top of the HyARC building, and has worked efficiently throughout the year without encountering any serious problems. The sub-radar system,
which is called GIN radar, was operated at Gifu University from April 2009 to July 2009, andat Anjo Branch, Toyohashi Office of River Works, Ministry of Land, Infrastructure, Transport
and Tourism (MLIT), from August 2009 to January 2010. In October 2009, Typhoon 0918
passed through the radar observation areas. Two radars at HyARC and Anjo sites successfully observed strong winds and intense rainfalls at around the typhoon’s landfall.
At the Anjo site, an operational X-band polarimetric radar of MLIT has started observation since February 2010. HyARC radar observations at the same location were considered
as preliminary observations. We contributed to the study of the observational modes of operational radars at MLIT using HyARC radar’s data at the Anjo site.
To enable prompt and adequate response in case a glitch is experienced in the radar systems during the observations, we installed web cameras to remotely monitor radar conditionsin association with the HyARC Technical Office.
We created analysis programs to derive polarimetric parameters and study the structureof precipitation systems. We also discussed the Japanese names of the polarimetric parameters, because they have not yet been unified under a common language discussions of thenames can be found on the Japanese website (http://www.rain.hyarc.nagoya-u.ac.jp/MPradar/meetings/20090116.html). Some of the names we proposed after the discussion have been
adopted in the book written by Professor Fukao and Dr Hamazu in 2009 (ISBN: 9784876987887).
In addition, a report on the outline of HyARC radars and the operation from 2007 to 2009has been compiled for a planned study of HyARC in 2009.
The release of the polarimetric radar data is under preparation. All observational datafrom April 2009 has been archived. We considered data policy and data format to release thedata after 2010.

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The Innovative Program of Climate Change Projection for the 21st Century (KAKUSHIN Program)l Cloud Modeling and Typhoon Research

Cloud physics is a key process for modeling climate changes, especially for global warming. The improvement of cloud processes is necessary for accurate simulations. Cloud processes are also core processes in simulations of high-impact weather systems such as heavy
rainfalls and typhoons. The cloud modeling team has been developing a cloud-resolving model named the Cloud Resolving Storm Simulator (CReSS). The cloud microphysics and computation scheme of CReSS are improved for accurate and high-speed calculations. Convective
clouds in tropical regions and typhoons are important to our team. The CReSS model is also
coupled with global models to simulate convective regions. CReSS is used for typhoon researchthat aims at verifying typhoon simulations performed by global models and producing accurate and quantitative evaluations of typhoon effects on human society under the current
and warming climates.
Typhoons occasionally cause a severe disaster owing to heavy rainfall and strong wind.
On the other hand, they bring a large amount of water resources to the East Asian countries.
Thus, typhoon changes with global warming have a large impact on the human society. Since
typhoons are composed of intense convective clouds as well as associated stratiform clouds,
a cloud-resolving simulation is necessary for accurate prediction of their intensities. In thepresent study, we have developed a new technique to perform a parallel computation of thecloud-resolving model in an arbitrary-shaped region, which is named as the “Tiling Domain
Technique” for CReSS. Using this technique, a simulation experiment with a computational
domain along the typhoon track was performed. The figure compares the simulation resultat 312 h from the initial time (09 JST August 25, 2004) with the radar observation provided
by the Japan Meteorological Agency (JMA). The position of the typhoon center, eye wall, surrounding spiral rainband, and orographically enhanced heavy rainfall are correctly simulated. The simulation shows the sea level pressure at the typhoon center also corresponds tothe observation. The result shows that the cloud-resolving simulation enables us to predict
quantitatively the intensity of a typhoon. In collaboration with the other team of the KAKUSHIN
program, our team performed simulation experiments of typhoon under global warming andfound that very intense typhoons, which never occurred in the current climate, might occur
in future climate.
Figure (A) Simulation result of
typhoon No.18 of 2004
using CReSS with the Tiling Domain Technique at
312 h from the initial time
(09 JST August 25, 2004).
Color levels represent
rainfall intensity (mmhr−1), contours represent
sea level pressure, and arrows represent horizontal
velocity. (B) JMA radarobservation at the sametime of (A). Color levels
represent rainfall intensity(mm hr−1).

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10Solution-Oriented Research in Science and Technology (SORST)
l Satellite Monitoring of Ocean Primary Productivity

The ocean is the largest reservoir of water and carbon dioxide on Earth’s surface. Hence,
the air-sea exchange of water and carbon dioxide plays a central role in climate systems on
Earth. The air-sea exchange of heat (water) and carbon dioxide is affected by phytoplankton
because they determine the optical properties of the near-surface oceans and absorb carbon
dioxide by primary productivity. To predict climate variability accurately, quantitative knowledge of the abundance and productivity of phytoplankton on a global scale is required formechanistic understanding of their regulatory processes. In practice, this knowledge and understanding can be attained only by satellite observations, but because of difficulty in obtaining in situ data for validation, available satellite data are yet to be fully exploited.
To overcome this difficulty, we have been working to develop an in situ monitoring systemfor validation of ocean primary productivity data from satellites. The system, composed of anunderwater winch system having a profiler buoy equipped with a fast-repetition-rate fluorometer, was successfully developed with the support of Core Research for Evolutional Scienceand Technology (CREST) by the Japan Science and Technology Agency (JST). Following this,a continuation project, Satellite Monitoring of Ocean Primary Productivity (SMOPP), was approved by the JST as part of the Solution-Oriented Research in Science and Technology (SORST)
Program in 2004. The objective of the SMOPP project is to design an operational monitoring
system for ocean primary productivity on a global scale. For this purpose, we conducted routine operation of the monitoring system and obtained validated time series satellite data on
primary productivity. These data were used, in combination with other time series satellite
data on physical forcing parameters of the ocean’s surface, for process studies on the responseof ocean biology to atmospheric forcing.
FY2009 was the last year of this CREST/SORST project, and the results were discussed
twice, in our internal workshops in October and December. We hosted the International Symposium on Estimation of Ocean/Land Primary Production by Satellite in collaboration withanother SORST project (at Chiba University), to apply our results to the Global Change Observation Mission-Carbon (GCOM-C) of the Japan Aerospace Exploration Agency (JAXA).
A notable achievement of this project is that we have developed and established an in situ
monitoring system for ocean productivity (the POPPS buoy system), which was corroborated
by successful operations in both nearshore and offshore (deep water) areas. The operation in
Sagami Bay during 2007–2008 provided the first-ever long-term (year-long) continuous measurements of daily ocean productivity, demonstrating the utility of our system. The POPPS
buoy system was adopted as the main instrument for stationary observations in the western
subtropical/subarctic North Pacific, conducted under the five-year (2009–2013) research program of the Japan Agency for Marine-Earth Science and Technology (JAMSTEC). Further
development of this system in various regions would advance validation for satellite-based
productivity, and the consequent use of the validated time series satellite data would enable a
breakthrough in the study of ocean material cycling and its response to climate change. As
other deliverables, we built an online database containing our research results during thisproject; it includes enormous numbers of measurements from hydrographic observations in
Sagami Bay/Tokyo Bay as well as from POPPS buoy deployments. Measurements are also
included from our custom-made Primary Productivity Profiler in various environments (thenorthern North Pacific, East China Sea, Sea of Japan, and Arabian Sea). These data will contribute to further understanding of the natural variability of oceanic productivity.

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11Study consortium for Earth-Life Interactive System (SELIS)The Study consortiumu for Earth-Life Interactive System (SELIS) was established as a
virtual institute in Nagoya University in March 2008, to follow up the research activity of the
21st century COE Program of  “the Sun-Earth-Life Interactive System”. The member instateof SELIS are HyARC, Graduate School of Environmental Sciences (GSES), Graduate Schoolof Bio-Agricultural Sciences (GSBS) and the Solar-Terrestrial Environmental Laboratory. The
SELIS project office is located at the 5th floor of the Institute for Advanced Research Hall of
this campus, and the HyARC is managing this office as a main institute of SELIS. The main
objective of the SELIS is to promote coopearative studies and relevant capacity building for
the Earth-Life Interaction studies, and to promote collaboration with relevant national andinternational programs and projects. SELIS is also expected to contribute to research projects
proposed from Nagoya University to the Research Institute for Humanity and Nature (RIHN)
in Kyoto. In the education program, SELIS contributes to some lecture course and seminars,
e.g., “Chikyu-gaku” (Study for the Earth) at the GSES.
In academic year 2009, SELIS organized six interdisciplinary seminars. SELIS also contributes to basic environmental studies and education under the Global COE Program “FromEarth System Science to Basic and Clinical Environmental Studies (BCES)” that started inJuly 2009. The leader of GCOE-BCES Program is Prof. Tetsuzo Yasunari of HyARC. Prof.
Hisashi Sato of GCOE took over as the directorship of the SELIS office from Prof. Tetsuya
Hiyama of HyARC.

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12 Division of Regional – Scale Water Cycle Processes
Laboratory of Meteorology
Development of a hydrometeor classification method for X-band polarimetric radars
Polarimetric radars can obtain microphysical information of hydrometeors, such as shapeand canting angle, which can be used for hydrometeor classification, using horizontally andvertically polarized waves. Several studies on hydrometeor classification were conducted tounderstand severe weather mechanisms using S- or C-band polarimetric radar in Northern
America and Europe. Polarimetric radars were recently introduced in Japan, and two X-bandpolarimetric radar systems were introduced at Nagoya University in 2007. This study presents
the development of a hydrometeor classification method for X-band polarimetric radars.
The hydrometeor classification method is based on the method for S-band radars in a previous study that uses polarimetric parameters of radar reflectivity (Zh), differential reflectivity(Zdr), specific differential phase (Kdp), correlation coefficient between horizontal and verticalpolarization signals (ρ hv), and temperature. This method classifies hydrometeors into 10 categories, including rain, snowflakes, and graupel. It evaluates the probability of each type ofhydrometeor with membership functions of polarimetric parameters and temperature withfuzzy logic, and determines the dominant hydrometeor type by its highest probability.
Since Kdp depends on wavelength, the membership functions of Kdp are modified to Xband radars. The membership functions of temperature including the dependency of relative
humidity apply to melting snowflakes. The vertical profilesof temperature and relative humidity are used from groundbased and upper-air sounding observations.
We attempted to apply the classification method to asnowfall event near Nagoya City, a graupel-falling event overIshikawa Prefecture during winter, and a thunderstorm near
Nagoya City during summer. We classified snowflakes using
the method corresponding to ground-based particle observation in the snowfall event near Nagoya City. Thus, theclassification method worked successfully. In the graupelfalling event, graupel was classified near the area where theZh value was high. A well-known vertical hydrometeor distribution in cumulonimbus clouds was classified in thethunderstorm event near Nagoya City (Fig. 1): rain occurs Fig. 1 Result of hydrometeor classiin the lower level; graupel is found near the melting level;
fication applied to the RHI
and snowflakes and ice crystals are found above the graupel.
scan at 1117 JST on August 6,
As we confirmed the existence of graupel, we compared the2009, along the direction of
the thunderstorm near Nagoya
time series of lightning frequency with that of volume ofCity. The horizontal axis indithe graupel region. The lightning strikes began when thecates the distance from thevolume of graupel was the largest and continued until thepolarimetric radar at Nagoya
graupel region disappeared. This result is consistent with
University.
previous studies on lightning strikes.

Raindrop size distribution parameters estimated from polarimetric radar variables in convective
cells near Okinawa Island during Baiu period
Convective cells, whose echo-top height reaches around the melting level and develop ina stratiform zone in mesoscale convective systems (MCSs), are observed in humid environment near Okinawa Island during Baiu period. To quantitatively clarify the microphysicalcharacteristics of convective ceslls developing in humid environment, we estimated raindrop
size distribution (DSD) parameters in convective cells using parameters such as radar reflectivity (Zh) and differential reflectivity (ZDR) obtained by the C-band polarimetric radar in
Okinawa Island during Baiu period. The DSD parameters are estimated for three types of
convective cells: one developing in the stratiform zone, one developing in the convective zone,
and an isolated convective cell.

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13
To estimate DSD parameters, their relationship with polarimetric radar variables are usedin this study. The median volume diameter (D0) is estimated by the D0-ZDR relationship given
by Bringi et al. (2006) as follows:
D0 = 4.27ξdr − 3.71;mm

for ξdr < 1.3

D0 = 0.733ξdr − 0.909;mmfo
or ξdr > 1.3,

(1)
(2)

where, ZDR = 10log10ξdr.
Figure 2a shows the scatter plot between D0 and ξdr derived from ground-based DSDs with
Eqs. (1) and (2). Although the number of samples for ξdr > 1.3 is not enough in this case, theD0-ZDR relationship corresponds to the ground-based observation for ξdr < 1.3. The normalized intercept parameter (Nw) that is related to the number concentration of raindrops isestimated using Zh and D0 for greater than 3 mm h−1 in rainfall rate as follows (Fig. 1b):Nw
= 4.1 × 10 −2 D0 6.93 ;Zhmm 7 .

(3)

Figure 3 shows the relationships of D0 and Nw with Zh obtained in three types of convective cells. For the convective cell in the stratiform zone in the mature stage, the estimatedmean D0 is approximately 1.2 mm with Zh of 40–45 dBZ; the estimated mean log10Nw ranges
from 32,000 to 100,000 mm−1 m−3. For the convective cell in the convective zone in the mature
stage, the estimated mean D0 is approximately 2 mm with Zh of 40–45 dBZ; the estimatedmean log10Nw range is
1,000–10,000 mm−1 m−3.
For the isolated convective cell in the mature
stage, D0 is also approximately 2 mm with Zh of
40–45 dBZ; the estimated mean log10Nw range
is also 1,000–10,000
mm−1 m−3. This indicatesthat a high number concentration of small raindrops contributes tolarge Zh for the convective cell in the stratiform
zone, whereas a low
number concentrationof large raindrops contributes to large Zh for
Fig. 3 (a) Relationship between radar-estimated mean D0 and Zhthat in the convective
for every 5 dBZ and (b) relazone and isolated cell.
tionship between radar-estiThe characteristics ofmated mean log10Nw and Zh
the estimated D0 and Nw
forevery 5 dBZ for convective
for three types of concells in their mature stages.
vective cells in the maFig. 2 Scatter plots (dots) and relaThe relationships are indicatedture stage using the potions (solid lines) for (a) D0
as (c) for the stratiform zone,
larimetric radar are also
versus ξdr and (b) “Zh/Nw” ver(n) for the convective zone,
applied for those in othsus D0 derived from groundand (△) for the isolated coner stages.
based DSDs (1 min. integravective cell. The mean valuestion) with rainfall rate greaterthan 3 mm h−1. The D0-ξdr relation shown by a solid line in(a) is given by Bringi et al.
(2006).

01-1.HyARC2009-E.indd 13

were calculated from the plan
position indicator (PPI) dataobtained between 0.5 km and3.0 km above sea level foreach convective cell.

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14Polarimetric radar observation of snow clouds in Hokuriku
In winter season, cold air outbreaks occur from the Eurasian continent in association
with the evolution and passage of cyclones. Snow clouds with strong updrafts cover the Sea
of Japan; organized snow clouds form convective systems, which cause heavy snowfall andhigh winds. Many studies have been conducted to clarify their structure and generation/evolution mechanisms. Previous Doppler radar observations examined the airflow structures inclouds. However, there are few studies associated with the distribution and evolution of precipitation particles in snow clouds. A polarimetric radar enables us to obtain informationsuch as shape, size, number density, and attitude of precipitation particles. In order to clarify distribution and evolution of precipitation particles in snow clouds, we performed polarimetric radar observation from December 2008 to February 2009 at Oshimizu of Ishikawa
Prefecture in Hokuriku, Japan.
During the observation period, strong cold air outbreaks occurred five times. The radar
was operated almost continuously during these events. From January 25 to 27, 2009, a stationary snowband formed along the San-in-Hokuriku coast that caused intense snowfall withfrequent lightning. We analyzed polarimetric parameters to show the characteristics of precipitation particles during this event. Radar reflectivity (Zh) reached 35–40 dBZ near thelanding portion (Fig. 4), which suggests frequent intensifications of snow clouds. The frequency of polarimetric parameters is examined in a 10-km square area (white square in Fig.
4) in which the two-day average Zh was the greatest in the entire radar range. The following
frequencies are calculated using the polar-coordinate data obtained by PPI scans. Correlation
coefficient (ρ hv) is more than 0.97 at 99% grids; thus, no wet solid particles, such as wet snow
and wet graupel, exist near the observation range. As a result, we thereafter considered only
dry snow and dry graupel as precipitation particle types. A previous study showed that thethreshold of Zh was 33 dBZ to distinguish the predominant particles in the volume between
dry snow and dry graupel. The ratio whose Zh was larger than 33 dBZ was 11% in these twodays. Negative specific differential phase (KDP) increases in the area whose Zh is larger than
30 dBZ (Fig. 5). This result indicates that the ratio of conical graupel, which falls at the vertically oriented attitude, increases.
The polarimetric radar observation in Hokuriku shows a potential to obtain detailed information about solid precipitation particles. To clarify the difference in cloud precipitation mechanisms, further observation should be performed in other locations. In addition, quantitative
precipitation estimation of each precipitation type remains to be an important problem.

Fig. 4 Time-averaged reflectivity pattern in
the radar observation range at 1.9 degree elevation angle from 03 JST on
January 25, 2009 to 30 JST on January
27, 2009. The white square shows theregion in which frequency of polarimetric parameters is examined.

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Fig.5

Frequency of specific differential phase(KDP) in the snowfall enhancement region:(a) for grids whose Zh is less than 30 dBZ
and (b) for grids equal to or larger than 30
dBZ.

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15Formation and maintenance mechanisms of a stationary snowband along the Hokuriku Coastin prevailing westerly
During the cold-air outbreak, a stationary snowband is occasionally observed over the Sea
of Japan along the San-in-Hokuriku coast, which brings heavy snowfall near the coastal areaof Hokuriku District, accompanied with a southerly offshore wind. A convergence zone thatcauses the formation of the snowband is observed between the southerly and westerly environmental flow. However, the mechanisms that form the southerly offshore wind are not clear.
This study examines the formation mechanism of the southerly offshore wind using a Doppler
radar and the Cloud Resolving Storm Simulator (CReSS).
Eight cases of stationary snowband formation along the San-in-Hokuriku coast were foundin the six winter seasons from December 2003 to March 2009. Strong westerly or west-southwesterly prevailed in the lower atmosphere in all cases. This wind field was different from theordinal northwesterly monsoon.
We performed numerical simulations using the CReSS for the stationary snowband thatdeveloped from January 24 to 26, 2009. The simulation well reproduced the precipitation
amount and location of the snowband in comparison with the Japan Meteorological Agency(JMA) radar observation (not shown). A convergence zone between the environmental westerly over the Sea of Japan and southerly offshore wind near the San-in-Hokuriku coast wasformed in the lower atmosphere. The convergence generated and maintained the stationary
snowband along the San-in-Hokuriku coast.
To clarify the cause of the development of southerly offshore wind, sensitivity experiments
to remove the land topography, to change roughness over the land surface to that over the sea
surface, and to change thermal properties over the land surface to those over the sea surface,were performed. Since the southerly offshore wind was not reproduced in the experiment tochange thermal properties, it was mainly formed by the effect of thermal contrast between
the land and sea. Figure 6 shows the result of the back-trajectory analysis on the sensitivity
experiment with flat terrain. The time series of forces along the southerly offshore wind show
the cause of development. The northward component of the pressure gradient force increases as the air parcels approach the convergence zone along the trajectories over the land (Fig.
7). As the air parcel approaches the Hokuriku area, the southerly wind and northward pressure gradient force increase. This increase is caused by a mesoscale high over the JapaneseIslands generated by the land-sea thermal contrast. The northward pressure gradient force
accelerates the air parcels toward the north.

Fig. 6 Back-trajectory analysis on the result of sensitivity experiment with flat terrain. Tracks from 02 JSTJanuary 25, 2009 show a course of 12 h.

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Fig. 7 Time series of velocity (solid line) and geostrophic component (dashed line) of an air
parcel that begins at the south side of theconvergence zone. The upper and middle
panels show the zonal and meridional components, respectively. The lower panel showstime series of wind direction (solid line) andheight (dashed line) of the air parcel.

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16
Evaluation of the snow/graupel ratio of the simulation results using the CReSS based on groundbased observation
To evaluate cold rain processes, such as the conversion process from snow to graupel, in the CReSS,
we compared the snow/graupel ratio at the groundsimulated by the CReSS with the results obtainedby the ground-based particle observation system ofKanazawa University.
The ground-based particle observation systemtakes a picture of each solid particle, digitizes it by
an image processing technique, and archives theshape, diameter, and falling speed of each particle.
The number concentration of particles is also archived. The complexity, which is the ratio of lengthof the circumference to that of minimum area, andnumber of holes are utilized to evaluate whether theparticle is a snowflake or graupel. The total volume
of snowflakes and graupel is calculated as the sumof particle volumes achieved by rotating particle Fig. 8 Time series of accumulated volume ofsnowfall (black bar) and graupel-fallarea. The total volume is gathered every minute.
(gray bar) at each minute obtained from
We performed daily simulations over almost thethe ground-based particle observation
entire Sea of Japan with a horizontal grid resolution
systemat Kanazawa University (upperof 5 km and near Ishikawa Prefecture with 1 km
panel)and that obtained from thefrom December 24, 2008 to April 7, 2009, using theCReSS with 1-km horizontal grid resoCReSS. The snowfall and graupel-fall amounts oblution (lower panel).
tained from the simulation at the grid of Kanazawa
University (136.71E, 36.55N) were compared withthose obtained from the ground-based particle observation system. The evaluation of volume ratio
between snowfall and graupel-fall was conductedduring the four days (January 13, 15, and 24, andFebruary 16, 2009) when the particle observation
system was operated.
Figure 8 shows the time series of the accumulated volume of snowfall and graupel-fall at eachminute obtained from the ground-based particle
observation system at Kanazawa University and thedata obtained from the CReSS with a 1-km horizontal grid resolution. Precipitation amounts of snowfall
and graupel-fall directly correspond to the volumeof each particle by assuming unit area. Spontaneous
increases of accumulated volumes of snowfall andgraupel-fall appear in the ground-based observation, Fig. 9 Scatter plot of the ratio of graupel-fall tototal precipitation (snowfall plus graupeland correspond to the passage of precipitation cells.
fall amount) between the observation in
Although both snowfall and graupel-fall are foundthe horizontal axis and simulation in thein the ground-based particle observation, almost all
vertical axis. Each plot indicates accuprecipitation is caused by graupel-fall in the simulamulated values every hour during Januarytion. Figure 9 shows a scatter plot of the ratio of13, 15, and 24, and February 16, 2009,
graupel-fall to the total precipitation between thewhen the particle observation system wasobservation and simulation every hour of the fouroperated.
day period. As plots are mainly located in the upperleft side, the simulation results overestimate the graupel-fall ratio compared with the observation. This result indicates the tendency to excessively generate graupel in the cold rain parameterization used in the CReSS.

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17Simulation of tornado-scale vortices occurring in winter cold-air outbreak over the Sea of Japan
Tornado-scale intense vortices, including tornadoes and waterspouts, called “Tatsumaki”
in Japanese, occur below intense convective clouds. Two major types of tornado-genesis are
known: a supercell type and a non-supercell type along a meso-front. Niino et al. (1997) showedthat a majority of tornadoes occurs in coastal regions of Japan and about 12% of tornadoes
are associated with the winter monsoon. When a cold-air outbreak occurs over the Sea ofJapan, shallow convective clouds develop and are usually ordinary cells with a short lifetime.
Since the Tatsumaki in the winter monsoon occurs over the sea and its life time is short with
their small scale, there are almost no reports about the Tatsumaki in the coastal regions of
the Sea of Japan except Kobayashi et al. (2007). They observed Tatsumaki in the coastal region
using a Doppler radar and photographs, and showed its horizontal scale of 150 m at a heightof the cloud base.
On December 25, 2005, a train accident caused by a strong gust wind occurred in the
coastal region, and five people were killed. The Tatsumaki is the most probable phenomenonof wind gust associated with a snowstorm. A high-resolution numerical simulation is a possible approach to clarify the characteristics and structure of the Tatsumaki in a snowstorm.
Since the horizontal scale of the Tatsumaki is as large as 100 m, a very high resolution ofseveral tens of meters is necessary, and the computation is very large. A huge parallel computer named the Earth Simulator makes large simulations of the Tatsumaki possible.
In our study, an one-way triple-nesting technique was used for the high-resolution simulation of intense vortices of the Tatsumaki with three different horizontal resolutions of 2000
m, 250 m, and 50 m, respectively. The initial and boundary conditions were provided by theforecast model output data of the JMA, and the initial time was 00 UTC, December 25, 2005.
The domains are shown in Fig. 10. The simulation of 50 m resolution was performed for 2.5
h. A cold-air outbreak occurred over the Sea of Japan, and the front of the cold air pushed
the warm and moist southwesterly wind toward the southeast. A large number of shallow
convective clouds with intense vortices of both positive and negative vorticity developed in
the cold air of the winter monsoon. A typical vortex with positive vorticity is shown in Fig.
11. Both vortices have an absolute vorticity of about 0.3 s−1, maximum wind speed of about
30 m s−1, and horizontal scale of about 200 m. This is close to the scale of the winter tornado
observed by Kobayashi et al. (2007). The velocity field of both vortices is balanced with thepressure field, that is, the cyclostrophic balance.

Fig. 10 Computational domains for the triple-nested
simulation experiments. The outermost, middle, and innermost regions are those of 2000
m, 250 m, and 50 m resolution simulations,
respectively. Shadings indicate rainfall intensity obtained from the 2000 m resolution
simulation.

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Fig. 11 An example of a typical vortex with positive
vorticity. Thick and thin contours indicate
vorticity and wind speed at the surface, respectively. The arrows indicate horizontal
wind vectors at the surface.

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18Laboratory for Climate System Study
Changes in the Asian monsoon climate during 1700–1850 induced by preindustrial cultivation
Monsoon is generated from a thermal contrast between land and ocean. Thus, the land’s
surface condition is an important factor in determining its climate. Monsoon Asia, where >50%of the world population is concentrated, has experienced large land cover/use changes due toagricultural development, particularly during the 18th and 19th centuries. In India and China
between 1700 and 1850, extension of cultivation and habitation activities decreased the percentage of forested area from 40–50% to 5–10% of the entire territories between 1700 and 1850.
Changing the land cover/use from forest to croplands can affect the global and regional climate
through changes in the energy and water balance at the earth’s surface. Among the various
effects of vegetation change, 2 factors have been shown to have a major influence on the energy and water balance: (i) an increase in surface albedo leading to a reduction in solar energy absorption at the surface and (ii) a decrease in surface roughness, resulting in low-level
wind speed intensification. As a consequence, the partitioning of turbulent heat fluxes into its
sensible and latent heat fluxes would subsequently affect the planetary boundary layer anddeep cumulus convection and, hence, the large-scale atmospheric phenomena.
We examined the actual impacts of land cover/use changes using a global historical vegetation
map reconstructed for the last 300 years. In thefirst half of the period, from 1700 to 1850, intensive
cultivation activities continually occurred over the
Indian subcontinent and over eastern China in Asia
(shaded areas in Fig. 1). Croplands in India havecontinued to increase since the 17th century whenthe British East India Company embarked on thecolonial management in the Mughal Empire. Croplands expanded explosively in China in the 1700s
in response to the introduction of new crops (e.g., Fig. 1. Land cover/use changes between 1700
and 1850 (gray shades) and 850-hPa windcorn, sweet potato, peanut) and to the rapid inin June–August (streamlines with colors
crease in population under the favorable economin meterss–1) in the 1850 experiment
ic policies of the Qing Dynasty. We considered that
(Takata et al., 2009)
the difference between the climatic realizations of
the 2 periods, in the 1700s and in the 1850s, might represent the long-term changes that occurred in those 150 years, and we examined the impacts of the reconstructed historical land
cover/use changes between those 2 periods. Consequently, we conducted 2 time-slice numerical experiments for the periods represented by 1700 and 1850, using the historical vegetation maps of 1700 and 1850 as the lower boundary conditions for an atmospheric generalcirculation model (AGCM), considering the changes in physical and physiological parametersof vegetation. Both equilibrium experiments were repeatedly forced by identical climatological annual cycles of the present-day monthly distributions of sea surface temperature(SST) and sea ice. The averaged states of summer (June, July, and August) we recomputedfor the equilibrated results. These were compared for examining the impact of the land cover/use changes on the Asian summer monsoons between the 2 periods (Takata et al., 2009).

Changes in Wind Field and Surface Energy–Water Balance Between 1700 and 1850.
In the western Indian subcontinent and in southeastern China, the summer monsoonal
wind blows from the ocean to the land in the lower troposphere (streamlines in Fig.1). Because
winds usually decelerate over land because of the large surface roughness, atmospheric moisture convergence and, hence, precipitation are large in those regions. Most of the agricultural cultivation during 1700–1850 occurred on forest, causing the surface roughness to de-

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19crease because of the reductions in vegetation height and leaf amount[specified as leaf areaindex (LAI)]. As a result, the surface wind troposphere as seen in the changes in 850-hPa windfield (arrows in Fig. 2A), which resulted in a reduction in the moisture convergence and theprecipitation in the western Indian subcontinent (hereafter the IND region) and in southeastern China (hereafter the SCH region) (Fig. 2B). The reduction in precipitation reduced thesurface soil moisture and, hence, the local evaporation and moist convection, creating a
positive feedback to further precipitation reduction. A vegetation change from forest to cropland resulted in an increase in the surface albedo (colors in Fig. 2C) due to the decrease in
LAI and the increase in leaf reflectivity. However,effects of the increase in surface albedo were overshadowed by a decrease in clouds in the IND andSCH regions associated with the significant decrease in precipitation. As a result, net shortwave
radiation (i.e., absorbed at the surface) was increased, and the decrease in soil moisture wasfurther enhanced in those regions (contours in Fig.
2C). On the other hand, net short-wave radiation
was decreased in the middle of eastern China(hereafter the ECH region) because of the increasein surface albedo. The decrease in net short-wave
radiation caused a decrease in surface temperaturebut only in part of the ECH region where surface
soil moisture was not decreased).These decreases
would have less effect on precipitation change.

Changes in Atmospheric Water Balance.
Our results suggest that the atmospheric waterbalance in those regions reflects whether surface
roughness reduction and albedo increase had a majorrole in the summer climate change. In the IND
and SCH regions, the ratio of moisture convergenceto the source of precipitation was high. In thoseregions, the moisture convergence changed considerably due to a combined effect of the decreased
surface roughness and the decreased soil moisture.
However, in the ECH region, dependence on theFig.3. June–August mean changes in the 200-hPa
wind field (streamlines)and geopotential
height (colors, in meters) between 1700
and 1850. Thick gray lines represent thosein which the differences are statisticallysignificantat the 95% confidence level(Takata et al. 2009).

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Fig.2. June–August mean changes between 1700
and 1850. (A) Surfacewind speed (colors,in m s–1) and 850-hPa wind (vectors, withunit vector 2 ms–1). (B) Precipitation (colors, in mm day–1) and vertically integrated
vapor flux(vectors, with unit vector 7 – 10kg m–1 s–1). (C) Surface albedo (colors, unitof legends is nondimensional) and net
short-wave radiation absorbed at the surface (downward positive; contours, withlabels in Wm–2). Shaded regions are similar to those where the differences in surface
wind speed, precipitation, or surface albedo are statistically significant at the 95%
confidence level (Takata et al. 2009).

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20moisture convergence was low, and precipitation changed little. Thus, the albedo effect, in termsof reducing net short-wave radiation (contours in Fig. 2C), was more apparent in this area.
The changes in precipitable water for the June–August mean were very small and negligible in each region and each time period (less than a few millimeters. Month-1). As a resultof the overall changes in precipitation and atmospheric heating induced by agricultural development particularly in south and southeast Asia, the Tibetan anticyclone in the upper troposphere weakened in 1850 (Fig. 3) The weakening of the Asian summer monsoon by cultivation
was also interpreted by using a regional climate model. The North Pacific high weakened in
1850, which was associated with the weakened Tibetan anticyclone. This weakening of theNorth Pacific high resulted in the slight increases in moisture convergence and precipitationin the ECH region, in contrast to the decreases in those in the IND and SCH regions
reference: Takata, K., K. Saitoh and T. Yasunari (2009): Changes in the Asian monsoon climate during
1700–1850 induced by preindustrial cultivation. Proc. Nat. Acad. Sci. U.S.A., doi:10.1073/pnas.
0807346106

Fig.4. Geographic features in and around Bangladesh. Closed circles denote the locations of
the 25 rain-gauge stations used in this study.

Fig.5. (a) The 20-summer ensemble spectrum of rainfall time series from 15 May to 15 September(124 days) over Bangladesh. . (b) Interannual
variation of the ABDR spectrum from 1981 to
2000.

Intraseasonal oscillation of rainfall and its effect on interannual variability over Bangladesh
during boreal summer
The Intraseasonal oscillation (ISO) of rainfall during the summer monsoon season (June–
August) and its possible effect on the IAV of total summer monsoon rainfall over Bangladesh
were examined using daily rainfall data from 25 rain-gauge stations for 20 years (1981–2000)(Fig. 4). The rain-gauge data for each of the 25 stations were simply averaged for each day

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21(defined as the ‘all Bangladesh daily rainfall’ and abbreviated as ABDR). The space–timestructures of atmospheric circulation and large-scale convection fields related to the ISO andthe IAV of the ABDR were also investigated using Japanese 25-year reanalysis (JRA25) andinterpolated OLR data. The analysis using multiyear rain-gauge data from a dense observation
network revealed robust and characteristic features of the ISO climatology in Bangladesh.
An ISO of 7–25 days (submonthly scale) appears in the ABDR time series in almost all of
the 20 years (1981–2000) (Fig. 5). The variance shows a large IAV. In contrast, the activity of
30–60-day ISO is weak and spectral peaks occasionally appear in this period range. The 7–25day filtered ABDR variance is always very large compared with the 30–60-day variance (Fig.
6). Thus, submonthly scale ISO can be regarded as a dominant intraseasonal mode of rainfall
fluctuation over Bangladesh during the summer monsoon season.
The time evolution of atmospheric circulation and convention anomalies associated with
submonthly scale ABDR ISO reveals that the changes in atmospheric circulation over the Bayof Bengal are associated with the so-called synoptic-scale 10–20-day ISO that originates aroundthe western Pacific and then moves westward to India. In the peak active phase, active convection anomalies appear over northeastern India, all of Bangladesh, and western Myanmar,
whereas suppressed convection anomalies occur over the southern Bay of Bengal, accompanied by a cyclonic anomaly from northeastern India to northwestern Myanmar, centered on
northern Bangladesh, and an anticyclonic circulation anomaly over the central Bay of Bengal(Fig. 7). Note that despite the continuous westward migration of convection and circulation
anomalies over the Bay of Bengal, the convection anomalies and cyclonic anomalies overBangladesh remain in almost the same location from the initiation to termination of the active ISO phase.
The spatial patterns of atmospheric circulation and convection associated with the ISO
and the IAV are quite similar to each other around the monsoon trough, especially from
northeastern India to Bangladesh. Climatologically, Bangladesh is one of the most predominant areas of submonthly scale ISO; however, 30–60-day ISO is not prominent. These characteristic features probably allow the submonthly scale ISO to modulate the total seasonalrainfall and the spatial patterns of circulation and convection over and near Bangladesh.
reference: Fujinami et al. 2010: Characteristic intraseasonal oscillation of rainfall and its effect oninterannual variability over Bangladesh during boreal summer, Int. J. Climatol., in press)

Fig.6. Interannual variations of total ABDR and intraseasonal ADBR variances on intraseasonal
timescales and 3- to 6-day ABDR variance forJune–August.

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Fig.7. Composite differences of (a) OLR (shadings),
925-hPa streamfunction, and vertically integrated moisture flux vectors between peak
active and break phases of 7- to 25-day rainfall variation over Bangladesh.

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22Laboratory for Cloud and Precipitation Climatology
Development and Improvement of the Satellite Data Simulator Unit (SDSU)
The Satellite Data Simulator Unit (SDSU) is a Fortran package used to compute synthetic satellite data from user-provided geophysical parameters such as cloud-resolving model (CRM) output. As shown in Fig. 1, the SDSU is designed to simulate microwave brightness
temperature, radar reflectivity, and visible/infrared radiance measured by satellite instruments.
The SDSU package also includes a beam convolution routine to adjust the spatial resolutionof the CRM to the footprint size of satellite sensors and a Mie lookup table generator to improve computational efficiency.
A primary application of the SDSU is to diagnose the performance of CRMs by comparing
CRM-simulated and satellite-observed radiance.  Model evaluation studies using a satellite
simulator have advantages over using a more traditional approach, based on satellite retrievals such as surface rain rate. As depicted in Fig. 2, a satellite retrieval algorithm is an “inversion model” that inverts satellite measurements to find the input of the radiative transfer
problem under several assumptions to characterize underlying uncertainties. In contrast, theSDSU operating as a “forward model” requires no inversion model to be invoked, and is immune to errors arising from satellite retrievals.
The SDSU version 2 (SDSU-v2), the upgraded version of the SDSU as of 2009, includes a
new user interface to explicitly characterize the particle size distribution (PSD) model foreach hydrometeor species simulated. An adequate characterization of the PSD models is
crucial because some satellite sensors, in particular radars, are sensitive to hydrometeor
particle size. The SDSU PSD library not only provides pre-installed PSD templates containing
conventional microphysical models such as exponential and gamma PSDs, but also enables
users to build their own PSD models. The SDSU-v2 can possibly support arbitrary single- anddouble-moment bulk microphysics schemes. As of March 2010, the SDSU-v2 has more than
40 registered users including many from overseas.

Fig.1. SDSU flow chart.

Fig.2. Schematic contrasting a satellite simulator and a satellite retrieval algorithm.

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10.10.26 6:14:26 PM23Climate Model Reproducibility of Cloud Radiative Forcing Associated with Tropical Convection
Development of clouds in response to deep convection largely dominates the Earth’s radiation budget over the tropics and subtropics. However, it is difficult for climate models to
precisely simulate clouds and their impacts on the radiation budget, leading to a large uncertainty in future climate projection. Evaluating the model reproducibility of the cloud radiative
forcing (CRF) using observations as the reference is indispensable for further improvementof the climate models. In this study, the CRF simulated by a group of climate models thatwere included in the International Panel for Climate Change (IPCC) Assessment Report 4(AR4) is evaluated by focusing on areas with sea surface temperatures (SSTs) higher than
27°C, where deep convection is particularly active. Climate regimes having different dynamical environments are separated in terms of large-scale ascent at the middle troposphere (500hPa) or ω 500, which is used as a proxy for large-scale atmospheric circulation.
The probability distribution function of ω 500 (Fig. 3) illustrates that strong ascent andweak subsidence dominate the areas with SSTs higher than 27°C. Interestingly, the ratio ofshortwave cloud forcing (SWCF) to longwave cloud forcing (LWCF), denoted by N, remains
approximately constant in the observation regardless of the ambient large-scale field. On theother hand, the models demonstrate that N increases as the large-scale ascent weakens andeventually turns into subsidence, and thus largely overestimates the observation. The model’s
incapability to properly simulate the LWCF sensitivity to SST is considered as one of thecauses for this overestimation. It is indicated that climate models generally suffer from systematic bias over areas where moist convection is activated by a local thermodynamic regulation against a dynamic forcing unfavorable for convection.

Fig.3. (a) Probability distribution function of ω 500, (b) N at 500 hPa level, (c) LWCF at 500 hPa,and (d) SWCF at 500 hPa. Thick solid, thick dashed, and thin lines indicate the observation, model ensemble mean, and individual models, respectively.

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24 Division of Global – Scale Water Cycle Variations
Loboratory of Satellite Meteorology
Diurnal variations in summer monsoon precipitation during active and break periods overcentral India and the southern Himalayan foothills
Diurnal variations in summer precipitation overcentral India and the southern Himalayan foothills
are investigated using Tropical Rainfall Measuring
Mission (TRMM) data from July to August since 1998
through 2007. TRMM Precipitation Radar (PR) andLightning Imaging Sensor (LIS) data are used tofurther investigate the characteristics of the precipitation. Based on rainfall characteristics in central
India, daily TRMM/3B42 (gridded rain data) data
are used to determine active (wet) and break (dry)periods. Diurnal variations in rain rate, rain frequency, conditional rain rate, storm height, and occurrence of convective rain are analyzed using
TRMM-PR data (0.1° × 0.1° resolution). Diurnal
variations in total lightning flashes are analyzed usFig. 1. Diurnal variation in (a) rain fraction, (b)ing TRMM-LIS data.
conditional rain rate, (c) rain frequency,
The precipitation over central India in the active(d) occurrence of convective rainfall, (e)periods is characterized by heavy and frequent rainstorm height, and (f) total flash per mean
rain rate during wet periods (solid line)
fall with a secondary morning peak. The precipitationand dry periods (broken line) over central
in the break periods is characterized by a strong diIndia during the summer.
urnal variation with isolated convective rain (Fig. 1).
Higher temperatures were observed during the dry periods as compared to that during the wet
periods. Similar characteristics were observed over the southern Himalayan foothills.

Study of the precipitation characteristics using meteorological data at the Amazonia Institute
before World War II
Amazonia plays an important role in global hydrological circulation. It constitutes one-thirdof the largest area of tropical rain forests left on the Earth. Amazonia includes the Amazon Riversystem; the largest river system on Earth, which carries approximately 20% of all the freshwaterthat is discharged into the oceans. Before World War II, only a few meteorological observation
stations existed. Thus, it is difficult to study the past climates of Amazonia. Before World War II(1931 to 1941), Japanese immigrants in Amazonia recorded meteorological data at the Amazonia
Institute. Data recorded from this station are analyzed and discussed here. The data clearly outline
the differences between the wet and dry seasons. Temperature varies with the rainfall; lower temperatures were recorded during the rainy season as compared to that during the dry season. A
diurnal temperature variation is observed with temperatures being the highest during daytime andlower in the mornings and evenings. The recorded surface wind data also indicate a diurnal
variation. The diurnal variation is not seen in the eye observation data for moving direction ofclouds. This suggests that the diurnal wind variation exists only in the surface winds. Although
there is little precipitation, the frequency of thunder normalized to the amount of precipitation ishigh in the dry season.
The rainfall distribution maps obtained from TRMM are used to investigate the seasonal movement of the precipitation area. This movement is found to be consistent with the data obtained
from the Amazonia Institute as well as the other station. The TRMM data also indicate that the
Amazon River affects the diurnal variation of rain. A reason for this could be the river breeze
generated due to the land–river thermal contrast.

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25Fig. 2. Monthly mean temperature (red) andamount of rainfall (blue) for 1931–1939.

Fig. 3. Wind direction frequency (days) for 1932–
1939.

Planning of field experiments conducted for the development of the Global Precipitation Mission dual-frequency precipitation radar algorithm using a dual Ka-radar system
Field experiments conducted for the development of the Global Precipitation Mission (GPM)
dual-frequency precipitation radar (DPR) algorithm using a dual Ka-radar system are described
below. The parameters that are to be measured in the ground experiments depend on the DPR algorithm. For liquid precipitation, raindrop-size distribution is the primary parameter to be measured.
For the dry snow, another parameter of the snow particle density should be measured. For the wetsnow or melting layer region, other parameters such as the melting ratio should be measured.
The dual Ka-band radar system, which is being developed by the Japan Aerospace Exploration
Agency (JAXA), will be a powerful tool to measure the parameters or their proxies required todevelop the DPR algorithm. The dual Ka-radar system can measure both the specific attenuationand the equivalent radar reflectivity at Ka-band. The basic idea is the retrieval of specific attenuation using the symmetrical appearance of rain attenuation in two radars in the same radio pathbut with the opposite (face to face) direction. Using the dual Ka-radar system along with other
instruments (e.g., a polarimetric precipitation radar , a windprofiler radar, and ground-based rainmeasurement systems), the uncertainties of the parameters required in the DPR algorithm can be
reduced. The verification of the improvement of rain-retrieval data using the DPR algorithm isalso included as an objective. The experimental plan was investigated as a collaboration study with
JAXA. The planned field experiments include: (1) the polarimetric Doppler radar observations at
the Okinawa Subtropical Environment Remote Sensing Center, the National Institute of Information and Communications Technology (NICT), (2) snow observations at the Snow and Ice ResearchCenter, National Research Institute for Earth Science and Disaster Prevention in Nagaoka, (3)observations at Kanazawa University, and (4) observations with Hokkaido University in Sapporo
City. The experiments also include a melting layer measurement at the slope of Mt. Fuji.

Interpreting space-borne radar observations of shallow convection using a rain-cell model
Observations of shallow, isolated convection obtained from the PR aboard the TRMM satellite
were compared to simulations obtained from a rain-cell model to examine the effects of the subresolution scale convection on the space-borne radar observations.
High-resolution observations of shallow, isolated convection from the PR agreed reasonably
well with the data generated by an idealized model. A large sample of shallow, isolated convection
was obtained from the PR data over the central Pacific Intertropical Convergence Zone. The PR
field-of-view (FOV) was modeled by a bivariate Gaussian distribution, and the sub-resolution scalerain cells were assumed to be circular and having a constant radar reflectivity (dBZ) value. Cell
diameter and cell depth were related by assuming an aspect ratio of 2 (diameter/depth). The average cell dBZ was assumed to be 32 with a standard deviation of 2 dBZ. The comparison of observed
and simulated probability distributions of dBZ was favorable, suggesting that the outlined exploratory approach could be useful for estimating the rainfall rate retrieval errors caused by the nonlinearities between the radar reflectivity and the rainfall rate and partially filled FOVs.

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26Laboratory of Eco-Hydrometeorology
Estimation of ecosystem respiration over a paddy field using storage change in CO2 density inthe nocturnal boundary layer
Accurate estimation of terrestrial ecosystem respiration is crucial for developing regionalto global-scale carbon-budget databases. This study evaluates nighttime ecosystem respiration
under low-turbulence conditions in a paddy field in China during the 2004 growing season.
Data from turbulent flux with storage change in CO2 density, and alternatively from CO2
concentration profiles measured from the surface to a height of 32 m, were investigated andcompared (Fig. 1). Conditions were separated into windy and calm according to where theyfell with respect to friction velocity (u*) threshold. On calm nights, the vertical gradient of
CO2 concentration is higher near the canopy level and decreases with height. No differences
are detected in the quantity or seasonality of nighttime ecosystem respiration (Re) between
values observed by eddy covariance and values calculated under calm conditions. Underestimation of nighttime Re values is low, even under calm conditions. Under stable conditions,nighttime CO2 flux is small, perhaps mainly because CO2 is stored in air below the sensor
height; similarly, CO2 drainage loss is small, perhaps because advection is small. The additionof measurement-height storage change in CO2 density helps reduce underestimation of nighttime Re values, so u* filtering and elimination of low-turbulence data are not required for a
paddy ecosystem. In contrast, under low-turbulence conditions, nighttime flux can be calculated from concentration profiles, but actual measurement of the height of the nocturnal
boundary layer is very important. To fill gaps in nighttime CO2 flux data for a paddy ecosystem,
development of multiple regression functions based on the crop-biomass/leaf-area index inassociation with field water status is preferable to development of just a single regressionfunction based on air/soil temperature.

Fig.1. Nighttime CO2 density and friction velocity (u*) for (a) windy, (b) intermittent,and (c) calm nights; the symbols represent the following: —, 3.5 m height; •,12.2 m height, and ◊, 32 m height.

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27
Estimation of regional CH4 flux over a paddy field using storage change in CH4 density in thenocturnal boundary layerThis study observes the nighttime inversion layer over a paddy field in summer and evaluates methods for estimating regional methane flux over such a field. On July 13, July 16, andAugust 4, 2009, we performed tethered-balloon observations of nighttime inversion layers
over a paddy field in Tsukuba, Ibaraki, Japan. Analysis of vertical profiles for CH4, CO2, potential temperature, relative humidity, wind direction, and wind speed from the surface toheights of several hundred meters revealed the presence of nighttime inversion layers (Fig.
2). A previous method for evaluating regional CH4 flux using chambers (the so-called chamber
method) proved insufficient, hence we tried a method using a time series of CH4 profiles beneath the nighttime inversion height, hereafter called the inversion-layer storage method(ILSM). For comparison, we also obtained regionally measured CH4 and CO2 fluxes evaluated by the gradient method (GM) and the eddy covariance method (ECM) from the National Institute for Agro-Environmental Sciences (NIAES). Comparison of the various methods indicates that CH4 fluxes obtained by ILSM (0.41 ± 2.78 µg · CH4 m−2 s−1) are in good
agreement with those obtained by GM (0.55 ± 0.45 µg · CH4 m−2 s−1). Additionally, CO2 fluxes
obtained by ILSM (510 ± 176 µg · CO2 m−2 s−1) are overestimated compared with those obtainedby ECM (122 ± 43 µg · CO2 m−2 s−1), but agree within an order of magnitude. Thus we suggestthat the ILSM method is suitable for estimating regional CH4 flux.

Fig.2. Time–height sections for CO2 (upper figure) and CH4 (lower figure) concentration
observed from 21:00 JST of 4 August to 06:00 JST of 5 August, 2009. Boxes in thesefigures indicate target duration and height range used for ILSM.

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28Laboratory of Satellite Biological Oceanography
Comparison of Primary Production Measured by Carbon and Fluorescence Methods in Ariake Sound
Primary production (PP) in the ocean is usually
measured by the rate of assimilation of carbon isotopes(14C or 13C) into particulate matter from bicarbonate
ions. However, it is difficult to obtain large data sets
because data collection is time consuming. Their accuracy is also questionable because bottle incubationis required for the measurements. A recently developed
method of measurement is the use of the fast repetition
rate fluorometer (FRRF). This is a simpler and quicker
method of measuring PP, and measurements can betaken continuously with deployment of the equipmentfrom vessel and with settling at a moored site. Those
methods (rate of carbon isotopes assimilation and
FRRF) are fundamentally different; the former measures net PP during incubation, and the latter measures Fig. 1. Comparison of carbon and fluorescencemethods for measuring PP at various
instantaneous gross PP. This study compared the results
depths measured by (a) integrating timefrom both methods in Ariake Sound, Japan, with large
series of FRRF measurements, (b) impletidal amplitude, for understanding the similarities andmenting incubation chlorophyll-a todifferences between the methods.
calculate PP from FRRF, (c) implementPP measurements taken by one-hour incubation
ing incubation chlorophyll-a and lightusing the carbon method were similar to those meaconditions to calculate PP from FRRF,
and (d) same as (c) excluding the nearsured by FRRF, except for those measured at the sursurface samples.
face. However, those measured by 24-hour incubationdiffered significantly from the time-integrated FRRF
measurements taken several times daily (Fig. 1). This may be because the samples analyzed
using the carbon method were taken at dawn and incubated with the light condition at thattime; whereas the fluorescence method measured PP at a stationary location with large fluctuations of phytoplankton abundance (chlorophyll-a) and the light conditions. Using the relationship between light and PP per chlorophyll-a obtained by FRRF with chlorophyll-a concentration and light condition during incubation, the daily PP values measured by carbon
and fluorescence methods were similar, except for the surface values (Fig. 1). This indicatesthat water mass movement by tidal motion may be the cause of the discrepancy. It was also
possible to calculate the daily PP using a single FRRF cast data around noon, the period withhighest light intensity, with the relationship between light and PP per chlorophyll-a.
There are still some uncertainties about the surface area values, which may include errors
in both carbon and FRRF methods, and about the difference of net and gross PP. However, the
FRRF method can be used to obtain PP data easily, and when combined with satellite data, it isexpected to estimate accurately the PP of marine environment, including that of coastal areas.

Ten-Year Seasonal and Interannual Variability of Satellite Chlorophyll-a in the East China Sea
Recently, environmental changes, such as frequent occurrence of red tide events and giant
jellyfish blooms, have been reported in the East China Sea. It has been also suggested that theThree-Gorge Dam (one of the world’s largest dams) on the Changjiang River influences the marine ecosystem of the East China Sea. Remote sensing data accumulated over the last 10 years
may be able to detect interannual changes in the abundance of phytoplankton (chlorophyll-a),
the major primary producer of marine ecosystem. However, the accuracy of chlorophyll-a datameasured by a satellite (satellite chlorophyll-a) is known to be poor in this region, and one of
the reasons is the presence of high suspended matter. Seasonal and interannual variability ofstandard satellite chlorophyll-a products in the East China Sea and the Yellow Sea were studied
in this study with taking into account the possible error of the satellite chlorophyll-a.

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29
Data indicate that the satellite chlorophyll-a data
averaged over 10 years was high over the nearshore
areas of the East China Sea, the Yellow Sea, and theBohei Sea; and low over the open ocean (Fig. 2). Highsatellite chlorophyll-a region was also observed in the
middle of the East China Sea, from the mouth of the
Changjiang River to the east. This high satellite chlorophyll-a area corresponded to the shallow area extended
eastward during winter; however it did not follow thebottom topography, during the summer months when
the discharge from the Changjiang River was at a maximum. Indicator of suspended matter, normalized waterleaving radiance of 555 nm (nLw555), was high in thenearshore area and high satellite chlorophyll-a area atthe east of Changjiang mouth during winter (Fig. 2).  It
was suggested that satellite chlorophyll-a was overestimated in the high nLw555 area, the nearshore area andthe east of Changjiang mouth during winter. On theother hand, during summer in the middle of the East
China Sea, satellite chlorophyll-a and nLw555 were highand low, respectively. The high satellite chlorophyll-a
was caused by the increase of chlorophyll-a with relation
Fig. 2. Distribution of 10-year averaged
to the Changjiang River discharge.
monthly satellite chlorophyll-a (upper)
A seasonal maximum of satellite chlorophyll-a wasand nLw555 (lower). White lines inobserved from March to April south of the East China
dicate bathymetry at 50 m intervals.
Sea to the Yellow Sea. This may correspond to thespring bloom of phytoplankton that is typically seen in the coastal temporal area (Fig. 3). Satellite chlorophyll-a data from the mouth of the Changjiang to the Tsushima Strait showed another peak in summer, thus indicating the influence of summer discharge from the ChangjiangRiver. This peak shifted from the mouth of the Changjiang in June–July to the east of Cheju
Island in August–September with a decrease in its magnitude. The summer peak of satellite
chlorophyll-a showed that interannual variability correlated to that of the summer dischargeof the Changjiang River, with a 0–2 month’s time lag (Fig. 4). In the Yellow Sea, the relationshipbetween the Changjiang River discharge and satellite chlorophyll-a was not clear, and satellite
Fig. 3. Seasonal variation of 10year averaged surface
chlorophyll-a (open) andnLw555 (closed) in eacharea shown in the upper
map.

Fig. 4. Scatter plot of monthly chlorophyll-a
from June to September and theChangjiang River discharge with a
0–2 month’s time lag for areas 1 (a),3 (b), 4 (c), 5 (d), 11 (e), and 14 (f).
Time lag indicates the month of satellite chlorophyll-a following the monthof the Changjiang River discharge.

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30
chlorophyll-a gradually increased over the 10 years.
It was apparent that there is a strong relationship between phytoplankton abundance andthe Changjiang River discharge in the middle of the East China Sea, and that this discharge
is the major factor controlling primary production. This indicates that primary productionin the East China Sea will change radically if there is a significant change in the ChangjiangRiver discharge caused by a climatic change and/or other human activities. It also indicatesthat the East China Sea is directly influenced by the discharge of the Changjiang River, where
the Yellow Sea may be more influenced by eutrophication of the Changjiang River and otherrivers in the surrounding area. Both quality and quantity of the river water should be important as the freshwater influence to the marine environment.

Influence of Water Mixing on Phytoplankton Pigment Composition in Ariake Sound
It is known that phytoplankton can produce photoprotective and light-harvesting pigments
under strong and weak light, respectively. However, light environment of phytoplankton in thefield varies with vertical water movement. When the mixed layer is shallower as compared to theeuphotic zone, the average light received by surface phytoplankton is high. Under these conditions, phytoplanktons produce photoprotective pigments and not light-harvesting pigments. In
Ariake Sound, the sediment resuspended by strong tidal mixing causes shallow euphotic zone.
Under this condition, it is expected that the response of phytoplankton under large light variation
is easily observed. Thus, a difference in phytoplankton pigments was observed during the spring
and the neap tides in winter with euphotic zone and light diffuse attenuation coefficient.
The observation was conducted by T/V Kakuyo-Maru of Nagasaki University on December
11–12 (spring tide) and December 17–18 (neap tide), 2008. Vertical density distributions wereobserved by a thermo-salinometer and the depth of the mixed layer (Zmix) was estimated. The
light attenuation coefficient (kd) was estimated from the vertical distribution of photosynthetically active radiation. The average relative radiation ( I mix ) was calculated using the following equation;
I mix = 100 ×

k×Z

1 – e mix.
k × Z mix

Chlorophyll-a, which is the basic pigment for photosynthesis is known to increase under low light conditions, light-harvesting accessory pigments (fucoxanthin and peridin), and photo-protected pigments(diadinoxanthin and diatoxanthin) were measured
by high-performance liquid chromatography.
The mixed layer was deeper and the light attenuation coefficient was larger during the springtide as compared with the neap tide (Fig. 5). Thismay be due to strong tidal currents made the deeper mixed layers and more resuspension of the bottom sediments during the spring tides. Thus, from Fig. 5. Scatter plot of mixed layer depth (Zmix)
versus light attenuation coefficient (Kd) for
the spring to the neap tides, the mixed layer became
samples obtained during spring (square)shallower, the attenuation coefficient decreased,
and neap (circle) tides. Contour lines
and the average light intensity increased.
show averaged relative light intensity inOn the other hand, the chlorophyll-a concentrathe euphotic zone ( I mix ). Crosses indicatetion was low in the spring tide and increased in thethe means and standard deviations of theneap tide. The fraction of light-harvesting accessquares and circles. Open and closed
sory pigments (fucoxanthin and peridinin) per
symbols indicate the ratio of (diadinoxanchlorophyll-a was nearly constant, although thatthin + diatoxanthin)/Chlorophyll-a [(DD+ DT)/Chl-a] < 0.15 and > 0.15, respecof photo-protective pigments per chlorophyll-a intively. Mean value of (DD + DT)/Chlorocreased from the spring to the neap tides.
phyll-a is 0.15.
These results indicate that a decrease in themixed layer and attenuation coefficient caused increase of the average light intensity for
phytoplankton from the neap to the spring tide, and that phytoplankton responded to increase
photo-protective pigments per chlorophyll-a to acclimatize to the strong light environment.

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31
Seasonal Variations in Primary Productivity, Particle Flux, and Air-Sea CO2 Flux in the Sagami Bay
A part of the particles produced in the upper ocean by phytoplankton is vertically carried
to the deep layer. This process plays a major role in CO2 sequestration to the deep ocean andis known as the biological pump. To examine the factors controlling the variability in thestrength of the biological pump in Sagami Bay, we have analyzed the quantity and quality ofthe sinking particles collected by a moored sediment trap (at a depth of 150 m). These samples
were collected over a period of one week, beginning in January 2001. Here we report the results of the data collected from November 2007 to December 2008, when the POPPS (Project on Ocean
Productivity Profiling System) buoy system provides productivity data from the same region, anddiscuss seasonal variations in primary productivity and particle flux.
The net primary productivity (NPP) was low in winter (200–400 mg C m–2 d–1), and increased from spring to a maximal value during August/September (>1200 mg C m–2 d–1) (Fig.
6). Following this, the particulate organic carbon flux at a depth of 150 m (POC flux150 m)
exhibited an increase from spring to summer, with a maximum during September/October(>70 mg C m–2 d–1), which lagged the peak of NPP by about a month (Fig. 6).
The δ 15N signal of trapped particles marked a minimum(~1.4 permil) in late February and gradually increased to a
maximum (9.8 permil) in May (Fig. 6), suggesting that nutrients supplied due to winter mixing were gradually consumed by phytoplankton during spring. In early June, δ 15N
showed a steep decline (~7 permil) and remained stable atthese levels. This implies that seasonal fresh-water discharge
and/or episodic, cyclonic eddies deliver nutrient-rich waters
into the euphotic zone (EZ), which would sustain higher
NPP and POC flux150 m during summer.
During the entire period, the averaged NPP and POC
flux150 m were 579.2 mg C m–2 d–1 and 40.0 mg C m–2 d–1,
respectively. Another observations using short-term (2–4days) multi-layer sediment traps showed a sharp drop-off
of POC flux with depth at shallower levels. This demonstrated a vertical flux ratio (POC flux150 m/POC flux50 m) of
0.28. With this value, an annual averaged POC flux50 m of
142.9 mg C m–2 d–1 and an export ratio at 50 m (=POC flux50
m/NPP) of 0.25 were estimated. Given a mean EZ of 50 min the Sagami Bay, this export ratio would correspond to
the f-ratio. That is, in terms of nitrogen, 25% of the annual
production is fueled by nitrogenous nutrients supplied fromoutside the EZ, known as new production.
Since the δ 13C of suspended POC within the EZ of Sagami Bay was strongly correlated with pCO2 in the surface
waters, it is possible to apply this empirical regression toδ 13C of trapped particles (Fig. 6). Then, changes in the surface oceanic pCO2 were reconstructed and the air-sea CO2
flux was estimated during the observation period. The averaged CO2 flux was −72.9 mg C m–2 d–1, suggesting that the
Sagami Bay acts as a sink for atmospheric CO2. Higher CO2
absorption (<−100 mg C m–2 d–1) occurred during March/
July and October/November (Fig. 6). Using the annual averFig. 6. Temporal changes in (a) NPP,age of the air-sea CO2 flux, 55% of the CO2 absorption was(b) downward POC flux at a
explained by POC flux150 m, indicating that more than half
depth of 150 m, (c) five-weekof the absorbed CO2 was transported to the deep sea as
running mean for NPP (dottedsinking POC. This conclusion emphasizes the importanceline) and POC flux (solid line),of the biological pump in the absorption of CO2 in Sagami(d) δ 15N and δ 13C of trappedBay.
organic matter, and (e) air-sea
CO2 flux in central Sagami
Bay.

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32Laboratory of Bio-Physical Oceanography
Interannual variation in nutrient transport through the Tsushima Strait
The Tsushima Warm Current carries large amounts of freshwater and nutrients from theEast China Sea (ECS) to the Japan Sea (JS). The water quality and discharge rates of the
Changjiang change rapidly. It is hypothesized that changes in the marine environment of the
ECS may influence that in the JS. In order to investigate this, we studied the seasonal andinterannual variations in the nutrient transport through the Tsushima Strait (TS). Since longterm nutrient data are limited, we derived empirical equations using in-site dissolved inorganic nitrogen (DIN) and water temperature data from the TS. These equations were formulated using 22 times hydrographic observations from 2005 to 2008. Applying the empiricalequations to water temperature data taken in June, August, and October from 1971 to 2000 in
the TS, we estimated the DIN concentration and the DIN transports through both the eastern(ECTS) and western (WCTS) channels of the TS. The results indicated that the 30-year averages of DIN transport through the ECTS in June, August, and October were 2.09 kmol/s, 3.55
kmol/s, and 4.10 kmol/s, respectively. The 30-year averages of DIN transport through the WCTS
in June, August, and October were 7.40 kmol/s, 9.64 kmol/s, and 13.39 kmol/s, respectively.
Interannual variations in the DIN transport through the ECTS and WCTS in August wereconsiderably large (Fig. 1), because there is a large year to year variation in the DIN concentration or water temperature in the lower
layer of the TS. Comparing the variationsin DIN transport to the salinity distribution in the TS revealed that salinity in thesurface layer of the WCTS in June, August, and October and of the ECTS in
August tends to be lower when DIN concentrations are higher than average value.
This suggests that a relationship between
the occurrence of low temperature water Fig.1. Interannual variation in DIN transport through TS in
August from 1971 to 2000. The right and left verticalin the bottom layer in the TS and theaxes indicate DIN transport through the WCTS andfreshwater inflow from the ECS into theECTS, respectively.
surface layer in the TS.

Improved current velocity calculation algorithm for Long Range Ocean Radar
The National Institute of Information and Communications (NICT) has established thelong range ocean radar (LROR) system at Ishigaki and Yonaguni Islands in the Yaeyama archipelago, Japan. Since 2001, high temporal and spatial resolution measurements of sea-surface currents (SSC) around Yaeyama Islands have been conducted using LROR. According todesign specifications, the LROR can measure SSC over an area of 200 km from the radar site;
however data calculated by the present algorithm covered approximately only 120 km fromthe radar site. The SSC is calculated from Doppler spectral data (SP data) of the LROR.
Analysis of the SP data reveals that SSC data can be obtained in situations where present algorithm shows no data or unrealistic SSC. Using this SP data, we improved current velocity
calculation algorithm, and then reprocessed SP data from 2004 to 2007.
To calculate the SSC, the primary peak, which is the frequency with the largest spectralenergy, must be determined. Parameters for detecting the primary peak were derived by trial
and error using SP data of August 2004. FORTRAN was used to prepare data processing tools.
Using this new algorithm, the SP data from 2004 to 2007 were reprocessed and both SSC
data sets (those calculated by the previous and newly derived algorithms) were compared. The
spatial distribution of the SSC data acquired are similar, but the root mean square (RMS) of

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33
the SSC on the continental shelf processed by the newly developed algorithm is much smaller
than that processed by the previous algorithm (Fig. 2). This result suggests improved accuracy of the data acquired father from radar site.

Fig.2. (a) RMS of SSC processed by the previous algorithm, (b) RMS of SSC processedby the present algorithm. The contour
lines indicate bottom topography.

Seasonal variation in the Kuroshio northeast of Taiwan
The velocity and axial position of the Kuroshio northeast of Taiwan varies at intervals thatcan be greater than 30 days. However, there is limited knowledge about the seasonal variation
because of description and discussion using short-term and discontinuous data in the previous
study. The Kuroshio has been monitored since 2001 to the present day using the LROR provided by the NICT. The LROR has provided surface current data with high spatial and temporal resolution. This study investigates the seasonal variation of the velocity and axial positionof the Kuroshio using the LROR surface current data.
The Kuroshio has stable northeastward currents with speeds greater than 50 cm s–1 andflow fluctuations with magnitudes of approximately 40 cm s–1 along its axis (Fig. 3a). The
seasonal variations in the maximum northeastward current and axial position are shown in
Fig. 3b (line AB). Here, the maximum northeastward current is defined as the maximum current speed of the northeastward current on line AB. The axial position is defined as the distancefrom point A to the location of the maximum northeastward current on line AB. The seasonalvariation in the maximum northeastward current consists of long- and short-term seasonalvariations. The long-term seasonal variation had winter minimum (~65 cm s–1 in January),summer maximum (~115 cm s–1 in July), and a periodicity of approximately 1 year. The shortterm seasonal variation was predominant during April to November and characterized by amaximum in July and minimums in May and October. The Kuroshio axis moved northwestward
from its mean position (solid square in Fig. 3b) within a range of about 20 km. The seasonality of the Kuroshio’s axis movement was not clear (Fig. 3b). In addition, the long- and shortterm seasonal variations were closely related to the seasonal variations of the meridional
component of wind stress around the ECS and of the Sverdrup transport over the area fromthe ECS to north of the Philippine Basin, respectively. This suggests that the seasonal variationin velocity of the Kuroshio occurs in response to wind forcing not over the North Pacific Ocean
but over the local areas from the ECS to the north of the Philippine Basin.

Fig.3. (a) Mean surface current during the period from 2002 to 2006. (b) Seasonal variations in the
maximum northeastward current (solid line) and axial position of the Kuroshio (solid diamond)on line AB. The shaded area in (a) represents currents with speeds greater than 50 cm s–1. The
solid triangle and square in (b) represent the maximum northeastward current and the axial position of the Kuroshio in the mean surface current field in (a), respectively.

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34 List of Publications* : Staffs, students and research fellows in the HyARC.
01.

Abe, O., S. Agata, M. Morimoto, M. Abe, K. Yoshimura, T. Hiyama* and N. Yoshida
A 6.5-year continuous record of sea surface salinity and seawater isotopic composition at Harborof Ishigaki island, southwest Japan. Isotopes in Environmental and Health Studies, 45, 247-258,
2009.

02.

Endoh, T., T. Matsuno, Y. Yoshikawa, Y. Tatsuyama and J. Ishizaka*
Observations of wind-driven deepening of the surface mixing layer in the Tsushima Strait. Journal of Oceangraphy, 65, 273-279, 2009.

03.

Friedrichs, M.A.M., M.-E. Carr, R.T. Barber, M. Scardi, D. Antoine, R.A. Armstrong, I. Asanuma,
M.J. Behrenfeld, E.T. Buitenhuis, F. Chai, J.R. Christian, A.M. Ciotti, S.C. Doney, M. Dowell, J.
Dunne, B. Gentili, W. Gregg, N. Hoepffner, J. Ishizaka*, T. Kameda, I. Lima, J. Marra, F. Melin,
J.K. Moore, A. Morel, R.T. O’Malley, J. O’Reilly, V.S. Saba, M. Schmeltz, T.J. Smyth, J. Tjiputra,
K. Waters, T.K. Westberry and A. Winguth
Assessing the uncertainties of model estimates of primary productivity in the tropical Pacific
Ocean. Journal of Marine Systems, 76, 113-133, 2009.

04.

Fukutomi, Y. and T. Yasunari*
Cross-equatorial Influences of Submonthly scale Southerly surges over the eastern Indian Ocean
during Southern Hemisphere winter. Journal of Geophysical Research, 114, D20119, 15,
2009.

05.

Geng, B., H. Yamada, K.K. Reddy, H. Uyeda* and Y. Fujiyoshi
Mesoscale Development and Along-Frontal Variation of a Meiyu/Baiu Front and Precipita­­tion Observed in the Downstream Region of the Yangtze River. Journal of the Meteorol­ogi­cal Society ofJapan, 87(3), 423-457, 2009.

06.

Fujinami, H.* and T. Yasunari*
The effects of midlatitude waves over and around the Tibetan Plateau on submonthly variabilityof the East Asian summer monsoon. Monthly Weather Review, 137, 2286-2304, doi: 10.1175/
2009MWR2826.1. 2009.

07.

Hirose, M., R. Oki, D.A. Short* and K. Nakamura*
Regional characteristics of scale-based precipitation systems from 10-year TRMM PR data. Journalof the Meteorological Society of Japan, 87A, 353-368, 2009.

08.

Ichikawa, H.*, H. Masunaga* and H. Kanzawa
Evaluation of Precipitation and High-level Cloud Areas Associated with Large-scale Circulation
over the Tropical Pacific in the CMIP3 Models. Journal of the Meteorological Society of Japan,
87(4), 771-789, 2009.

09.

Ishida, H., Y.W. Watanabe, J. Ishizaka*, T. Nakano, N. Nagai, Y. Watanabe, A. Shimamoto, N.
Maeda and M. Magi
Possibility of recent changes in vertical distribution and size composition of chlorophyll-a in thewestern North Pacific region. Journal Oceanography, 65, 179-186, 2009.

10.

Ishizaka, J.*
Ocean Color Research for Global Imager (GLI) on Advanced Earth Observation Satellite-II (AD-

11.

12.

13.

01-1.HyARC2009-E.indd 34

EOS-II). Journal of Remote Sensing Society of Japan, 29, 74-79, 2009.
Jianqing, Xu, S. Yu, J. Liu, S. Haginoya, Y. Ishigooka, T. Kuwagata, M. Hara and T. Yasunari*
The implication of heat and water balance change in a Lake Basin on the Tibetan Plateau. Hydrological Research Letters, 3.1-5. doi: 10.3178/HRL.3.1, 2009.
Kim, H.-C., H. Yamaguchi*, S. Yoo, J. Zhu, K. Okamura, Y. Kiyomoto, K. Tanaka, S.-W. Kim, T.
Park, I.S. Oh and J. Ishizaka*
Distribution of Changjiang Diluted Water detected by satellite chlorophyll-a and its interannual
variation during 1998–2007. Journal of Oceanography, 65, 129-135, 2009.
Liu, P., M. Satoh, B. Wang, H. Fudeyasu, T. Nasuno, T. Li, H. Miura, H. Taniguchi, H. Masunaga*,
X. Fu and H. Annamalai
An MJO simulated by the NICAM at 14-km and 7-km resolutions. Monthly Weather Review, 137,

10.10.26 6:14:50 PM

35
14.

15.

16.

17.

18.

19.

20.

21.

22.

23.

24.

25.

26.

27.

28.

29.

01-1.HyARC2009-E.indd 35

3254-3268, 2009.
Liu, P., Y. Kajikawa*, B. Wang, A. Kitoh, T. Yasunari*, T. Li, H. Annamalai, X. Fu, K. Kikuchi, R.
Mizuta, K. Rajendran, D.E. Waliser and D. Kim
Tropical Intraseasonal Variability in the MRI-20km 60L AGCM. Journal of Climate, 22, 2006-2022,
2009.
Masunaga, H.*
A 9-season TRMM observation of the Austral Summer MJO and Low-frequency Equatorial Waves.
Journal of Meteorological Society of Japan, 87A, 295-315, 2009.
Matsui, T., X. Zeng, W.-K. Tao, H. Masunaga*, W.S. Olson and S. Lang
Evaluation of Long-term Cloud-resolving Model Simulations Using Satellite Radiance Ob­
servations and Multi-frequency Satellite Simulators. Journal Atmospheric and Oceanic Technology, 26, 1261-1274, 2009.
Morimoto, A.*
Evaluation of Tidal Error in Altimetry Data in the Asian Marginal Seas. Journal of Ocea­nography,
65(4), 477-485, 2009.
Morimoto, A.*, S. Kojima, S. Jan and D. Takahashi*
Movement of the Kuroshio axis to the northeast shelf of Taiwan during typhoon events. Estuarine,
Coastal and Shelf Science, 82(3), 547-552, 2009.
Morimoto, A.*, T. Takikawa, G. Onitsuka, A. Watanabe, M. Moku and T. Yanagi
Seasonal Variation of Horizontal Material Transport through the Eastern Channel of the Tsushima Straits. Journal of Oceanography, 65(1), 61-71, 2009.
Morimoto, A.*, Y. Isoda, T. Tameishi and S. Moriwaki
Seasonal variation in Tsushima Warm Current paths over the shelf off the San’in coast, Japan.
Continental Shelf Research, 29(11-12), 1437-1447, 2009.
Nakajima, T., H. Murakami, M. Hori, T.Y. Nakajima, H. Yamamoto, J. Ishizaka*, R. Takeishi, T.
Aoki, T. Takamura, M. Kuji, D.D. Nguyen, A. Ono, S. Fukuda and K. Muramatsu
Overview and Science Highlights of the ADEOS-II/GLI Project. The Remote Sensing Society ofJapan, 29, 11-28, 2009.
Nakajima, T.Y., H. Masunaga* and T. Nakajima
Near-global Scale Retrievals of the Cloud Optical and Microphysical Properties from the MidoriII GLI and AMSR Data. The Remote Sensing Society of Japan, 29, 29-39, 2009.
Nishikawa, M.*, T. Hiyama*, K. Tsuboki* and Y. Fukushima
Numerical Simulations of Local Circulation and Cumulus Generation over the Loess Plateau,
China. Journal of Applied Meteorology and Climatology, 48, 849-862, 2009.
Ohigashi, T*. and G.W.K. Moore
Fine structure of a Greenland reverse tip jet: A numerical simulation. Tellus, 61A, 512- 526,
2009.
Onitsuka, G., A. Morimoto*, T. Takikawa, A. Watanabe, M. Moku, Y. Yoshikawa and T. Yanagi
Enhanced chlorophyll associated with island-induced cyclonic eddies in the eastern channel of
the Tsushima Straits. Estuarine, Coastal and Shelf Science, 81(3), 401-408, 2009.
Oouchi, K.A., T. Noda, M. Satoh, B. Wang, S.P. Xie, H.G. Takahashi and T. Yasunari*
Asian summer monsoon simulated by a global cloud-system-resolving model: diurnal Intra-seasonal Variability. Geophysical Research Letters, 36. L11815. doi: 10.1029/ 2009­­GL038271. 2009.
Padhakrishna, B., T. Narayana Rao, D. Narayana Rao, N. Prabhakara Rao, K. Nakamura* andAshok Kumar
SharmaSpatial and seasonal variability of raindrop size distributions in southesast India. Journalof Geophysical Research, 114, D04203, doi: 10.1029/2008JD011226, 2009.
Rao, D.N., M.V. Ratnam, S. Mehta, D. Nath, S. Ghouse Basha, V.V.M. Jagannadha Rao, B.V.
Krishna Murthy, T. Tsuda and K. Nakamura*
Validation of the COSMIC radio occultation data over Gadangi (13.48N, 79.2E): A tropical region.
Terrestrial Atmospheric and Oceanic Science. 20(1), 59-70, doi: 10: 3319/TAO2008.01.23.01(F3C),
2009.
Shinoda, T.*, A. Higuchi, K. Tsuboki*, T. Hiyama*, H. Tanaka*, S. Endo*, H. Minda*, H. Uyeda*
and K. Nakamura*

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36
30.

31.

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33.

34.

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36.

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39.

01-1.HyARC2009-E.indd 36

Structure of convective circulation in the atmospheric boundary layer over the north­western
Pacific Ocean under a subtropical high. Journal of the Meteorological Society of Japan, 87(6), 979996, 2009.
Shinoda, T.*, T. Amano, H. Uyeda*, K. Tsuboki* and H. Minda*
Structure of line-shaped convective systems obliquely training to the Baiu front ob­served aroundthe Southwest Islands of Japan. Journal of the Meteorological Society of Japan, 87(4), 739-745,
2009.
Short, D.A.*, M. Hirose and K. Nakmaura*
An interpretation of TRMM radar observations of shallow convection with a rain cell model.
Journal of the Meteorological Society of Japan, 87A, 53-66, 2009.
Shusse, Y.*, K. Nakagawa, N. Takahashi, S. Satoh and T. Iguchi
Characteristics of polarimetric radar variables in three types of rainfalls in a Baiu front event
over the East China Sea. Journal of the Meteorological Society of Japan, 87(5), 865-875, 2009.
Singh, P.* and K. Nakamura*
Diurnal variation in summer precipitation over the central Tibetan Plateau. Journal of Geophysical Research, 114, D20107, doi: 10.1029/2009JD011788, 2009.
Siswanto, E.*, A. Morimoto* and S. Kojima
Enhancement of phytoplankton primary productivity in the southern East China Sea following
episodic typhoon passage. Geophysical Research Letters, 36, L11603, 2009.
Takahashi, D.*, X. Guo, A. Morimoto* and S. Kojima
Biweekly periodic variation of the Kuroshio axis northeast of Taiwan as revealed by ocean highfrequency radar. Continental Shelf Research, 29(15), 1896-1907, 2009.
Takata, K., K. Saito and T. Yasunari*
Changes in the Asian monsoon climate during 1700–1850 induced by pre-industrial cultiva­tion.
Proceedings of the National Academy of Sciences of the United States of Ameirica, doi: 10.1073/
pnas.0807346106, 2009.
Prasanna, V. and T. Yasunari*Time-space characteristics of seasonal and intrannual variations of atmospheric water balanceover south Asia. Journal of the Meteorological Society of Japan, 87(2), 263-287. 2009.
You, C.-H., D.-I. Lee, S.-M. Jang, H. Uyeda*, T. Shinoda* and F. Kobayashi
Characteristics of Rainfall Systems Accompanied with Changma Front at Chufado in Korea.
Asia-Pacific Journal of Atmospheric Sciences, 46(1), 41-51, 2009.
Morimoto, A.*
Horizontal and Vertical Nutrients transport in the Eastern Channel of the Tsushima Strait, Monitoring and prediction of marine and atmospheric environmental change in the East Asia, Ed. T.
Yanagi, TERAPUB, 171-194, 2010.

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Hydrospheric Atmospheric Research Center (HyARC)
Nagoya University
Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
Office:Telephone: +81-52-789-3466
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Home Page: http://www.hyarc.nagoya-u.ac.jp/english/index.html

The 2009 Annual Report was published October 2010 by
the Hydrospheric Atmospheric Research Center (HyARC) Nagoya University. Copies of this report are available from theoffice of the Center.

Printed by Nagoya University COOP

Annual Report

Hydrospheric Atmospheric Research Center(HyARC)
Nagoya University

2010