Faculty Profiles - MASUNAGA, Hirohiko

Papers - MASUNAGA, Hirohiko

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The Tropical Convective Evolution in Different Rain Types over the West and East Pacific Reviewed

Chen, YC; Masunaga, H

SOLA Vol. 20 page： 392 - 399 2024.12

When, Where and to What Extent Do Temperature Perturbations Near Tropical Deep Convection Follow Convective Quasi Equilibrium? Reviewed International coauthorship

Li, YX; Masunaga, H; Takahashi, H; Yu, JY

GEOPHYSICAL RESEARCH LETTERS Vol. 51 ( 11 ) 2024.6

Long-term relationships between summer clouds and aerosols over mid-high latitudes of the Northern Hemisphere Reviewed

Watari, A; Iizuka, Y; Fujita, K; Masunaga, H; Kawamoto, K

SCIENTIFIC REPORTS Vol. 14 ( 1 ) 2024.4

The Energetics of the Lagrangian Evolution of Tropical Convective Systems Reviewed International coauthorship International journal

Masunaga, H; Takahashib, H

JOURNAL OF THE ATMOSPHERIC SCIENCES Vol. 81 ( 4 ) page： 783 - 799 2024.4

Investigating Convective Processes Underlying ENSO: New Insights Into the Fixed Anvil Temperature Hypothesis Reviewed International coauthorship International journal

Takahashi, H; Luo, ZJ; Masunaga, H; Storer, R; Noda, AT

GEOPHYSICAL RESEARCH LETTERS Vol. 51 ( 6 ) 2024.3

The Edge Intensification of Eastern Pacific ITCZ Convection Reviewed

Masunaga Hirohiko

JOURNAL OF CLIMATE Vol. 36 ( 11 ) page： 3469 - 3480 2023.6

Process-Level Assessment of the Iris Effect Over Tropical Oceans Reviewed

Ito Masato, Masunaga Hirohiko

GEOPHYSICAL RESEARCH LETTERS Vol. 49 ( 7 ) 2022.4

Characterizing Ice-Scattering Homogeneity in TRMM Microwave Imagers and Its Influence on Oceanic Rain-Rate Estimation Bias of TRMM Precipitation Radar Reviewed International coauthorship International journal

Sekaranom Andung Bayu, Nurjani Emilya, Wibowo Sandy Budi, Masunaga Hirohiko

ATMOSPHERE Vol. 12 ( 11 ) 2021.11

Refinement of Surface Precipitation Estimates for the Dual-frequency Precipitation Radar on the GPM Core Observatory Using Near-Nadir Measurements Reviewed International journal

Hirose Masafumi, Shige Shoichi, Kubota Takuji, Furuzawa Fumie A., Minda Haruya, Masunaga Hirohiko

JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN Vol. 99 ( 5 ) page： 1231 - 1252 2021.10

Transient Aggregation of Convection: Observed Behavior and Underlying Processes Reviewed International coauthorship

JOURNAL OF CLIMATE Vol. 34 ( 5 ) page： 1685 - 1700 2021.3

Detection and Tracking of Tropical Convective Storms Based on Globally Gridded Precipitation Measurements: Algorithm and Survey over the Tropics Reviewed International coauthorship

Takahashi Hanii, Lebsock Matthew, Luo Zhengzhao Johnny, Masunaga Hirohiko, Wang Cindy

JOURNAL OF APPLIED METEOROLOGY AND CLIMATOLOGY Vol. 60 ( 3 ) page： 403 - 421 2021.3

A Satellite-Based Estimate of Convective Vertical Velocity and Convective Mass Flux: Global Survey and Comparison With Radar Wind Profiler Observations Reviewed International coauthorship

Jeyaratnam Jeyavinoth, Luo Zhengzhao Johnny, Giangrande Scott E., Wang Die, Masunaga Hirohiko

GEOPHYSICAL RESEARCH LETTERS Vol. 48 ( 1 ) 2021.1

Refinement of surface precipitation estimates for the Dual-frequency Precipitation Radar on the GPM Core Observatory using near-nadir measurments Reviewed

Hirose, M., S. Shige, T. Kubota, F. A. Furuzawa, H. Minda, and H. Masunaga

Journal of the Meteorological Society of Japan Vol. 99 page： 1231 - 1252 2021

A Mechanism for the Maintenance of Sharp Tropical Margins Reviewed International coauthorship

Masunaga Hirohiko, Mapes Brian E.

JOURNAL OF THE ATMOSPHERIC SCIENCES Vol. 77 ( 4 ) page： 1181 - 1197 2020.4

Inter-product biases in global precipitation extremes Reviewed International coauthorship

Masunaga, H., M. Schröder, F. A. Furuzawa, C. Kummerow, E. Rustemeier, and U. Schneider

Environmental Research Letters Vol. 14 page： 125016 2019.12

Vertical Modes and Effective Stability of Quasi-2-Day Waves Reviewed

Sumi Yukari, Masunaga Hirohiko

JOURNAL OF THE ATMOSPHERIC SCIENCES Vol. 76 ( 7 ) page： 2005 - 2022 2019.7

Origins of Heavy Precipitation Biases in the TRMM PR and TMI Products Assessed with CloudSat and Reanalysis Data Reviewed International coauthorship

Sekaranom Andung Bayu, Masunaga Hirohiko

JOURNAL OF APPLIED METEOROLOGY AND CLIMATOLOGY Vol. 58 ( 1 ) page： 37-54 2019.1

Radiative Invigoration of Tropical Convection by Preceding Cirrus Clouds Reviewed International coauthorship

Masunaga Hirohiko, Bony Sandrine

JOURNAL OF THE ATMOSPHERIC SCIENCES Vol. 75 ( 4 ) page： 1327-1342 2018.4

The Meandering Margin of the Meteorological Moist Tropics Reviewed International coauthorship

Mapes Brian E., Chung Eui Seok, Hannah Walter M., Masunaga Hirohiko, Wimmers Anthony J., Velden Christopher S.

GEOPHYSICAL RESEARCH LETTERS Vol. 45 ( 2 ) page： 1177-1184 2018.1

New Observational Metrics of Convective Self-Aggregation: Methodology and a Case Study Reviewed

Kadoya Toshiki, Masunaga Hirohiko

JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN Vol. 96 ( 6 ) page： 535-548 2018

Global precipitation measurements for validating climate models Reviewed International coauthorship

Tapiador F. J., Navarro A., Levizzani V., Garcia-Ortega E., Huffman G. J., Kidd C., Kucera P. A., Kummerow C. D., Masunaga H., Petersen W. A., Roca R., Sanchez J. -L., Tao W. -K., Turk F. J.

ATMOSPHERIC RESEARCH Vol. 197 page： 1 - 20 2017.11

Implications of Warm Rain in Shallow Cumulus and Congestus Clouds for Large-Scale Circulations Reviewed International coauthorship

Nuijens Louise, Emanuel Kerry, Masunaga Hirohiko, L'Ecuyer Tristan

SURVEYS IN GEOPHYSICS Vol. 38 ( 6 ) page： 1257-1282 2017.11

Observing Convective Aggregation Reviewed International coauthorship

Holloway Christopher E., Wing Allison A., Bony Sandrine, Muller Caroline, Masunaga Hirohiko, L'Ecuyer Tristan S., Turner David D., Zuidema Paquita

SURVEYS IN GEOPHYSICS Vol. 38 ( 6 ) page： 1199-1236 2017.11

Comparison of TRMM-Derived Rainfall Products for General and Extreme Rains over the Maritime Continent Reviewed

Sekaranom Andung Bayu, Masunaga Hirohiko

JOURNAL OF APPLIED METEOROLOGY AND CLIMATOLOGY Vol. 56 ( 7 ) page： 1867-1881 2017.7

Revisiting the iris effect of tropical cirrus clouds with TRMM and A-Train satellite data Reviewed International coauthorship

Choi Yong-Sang, Kim WonMoo, Yeh Sang-Wook, Masunaga Hirohiko, Kwon Min-Jae, Jo Hyun-Su, Huang Lei

JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES Vol. 122 ( 11 ) page： 5917-5931 2017.6

A toy model of tropical convection with a moisture storage closure Reviewed

Masunaga Hirohiko, Sumi Yukari

JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS Vol. 9 ( 1 ) page： 647-667 2017.3

Relationship between the direction of diurnal rainfall migration and the ambient wind over the Southern Sumatra Island Reviewed

Yanase A., Yasunaga K., Masunaga H.

EARTH AND SPACE SCIENCE Vol. 4 ( 3 ) page： 117-127 2017.3

Convective and large-scale mass flux profiles over tropical oceans determined from synergistic analysis of a suite of satellite observations Reviewed

Masunaga, H., and Z. J. Luo

J. Geophys. Res. Atmos Vol. 121 2016

A Moist Static Energy Budget Analysis of Quasi 2-day Wave Using Satelite and Reanalsyis Data Reviewed

Sumi, Y. and H. Masunaga

Vol. 73 page： 743-759 2016

Assessment of a Satellite-based Atmospheric Budget Analysis Method with CINDY2011/DYNAMO/AMIE and TOGA COARE Sounding Array Data Reviewed

Masunaga, H.

J. Meteor. Soc. Japan Vol. 93A page： 21-40 2015

Early evaluation of Ku- and Ka-band sensitivities for the Global Precipitation Measurement (GPM) Dual-frequency Precipitation Radar (DPR) Reviewed

Toyoshima, K., H. Masunaga, and F. A. Furuzawa

SOLA Vol. 11 page： 14-17 2015

Assessment of the consistency among global microwave land surface emissivity products Reviewed

Norouzi,H., M. Temimi, C. Prigent, J. Turk, R. Khanbilvardi, Y. Tian, F. A. Furuzawa, and H. Masunaga

Atmos. Meas. Tech. Vol. 8 page： 1197-1205 2015

Free-tropospheric moisture convergence and tropical convective regimes Reviewed

Masunaga, H.

Geophys. Res. Lett. Vol. 41 page： 8611-8618 2014.12

A mechanism of tropical convection inferred from observed variability in the moist static energy budget Reviewed

Masunaga, H., and Tristan S. L'Ecuyer

J. Atmos. Sci. Vol. 71 page： 3747-3766 2014

The potential roles of background surface wind in the SST variability associated with intraseasonal oscillations Reviewed

Kanemaru, K. and H. Masunaga

J. Climate Vol. 27 page： 7053-7068 2014

Quantifying uncertainties in land surface microwave emissivity retrievals Reviewed

Tian, Y., C. Peters-Lidard , K. W. Harrison, C. Prigent, H. Norouzi, F. Aires, S.-A. Boukabara, F. A. Furuzawa, and H. Masunaga

IEEE Trans. Geosci. Remote Sens. Vol. 52 page： 829-840 2014

A satellite study of tropical moist convection and environmental variability: A moisture and thermal budget analysis Reviewed

Masunaga, H.

J. Atmos. Sci. Vol. 70 page： 2443-2466 2013

A satellite study of the relationship between sea surface temperature and column water vapor over tropical and subtropical oceans Reviewed

Kanemaru, K. and H. Masunaga

J. Climate Vol. 26 page： 4204-4218 2013

An evaluation of microwave land surface emissivities over the continental United States to benefit GPM-era precipitation algorithms Reviewed

Ferraro, R., C. Peters-Lidard , C. Hernandez, F. J. Turk, F. Aires, C. Prigent, X. Lin, S.-A. Boukabara, F. Furuzawa, K. Gopalan, K. Harrison, F. Karbou, L. Li, C. Li, H. Masunaga, L. Moy, S. Ringerud, G. Skofronik-Jackson, Y. Tian, and N.-Y. Wang

IEEE Trans. Geosci. Remote Sens. Vol. 51 page： 378-398 2013

Aerosol effects on cumulus congestus population over the tropical Pacific: A cloud-resolving modeling study Reviewed

Li, X., W.-K. Tao, H. Masunaga, G. Gu, and X. Zeng

J. Meteor. Soc. Japan Vol. 91 page： 817-833 2013

Analysis of cloud properties associated with tropical convection in climate models and satellite data Reviewed

Ichikawa, H., H. Masunaga, Y. Tsushima, and H. Kanzawa

Journal of the Meteorological Society of Japan Vol. 90 page： 629-646 2012

Short-term versus climatological relationship between precipitation and tropospheric humidity Reviewed

Hirohiko Masunaga

Journal of Climate Vol. 25 page： 7983-7990 2012

Reproducibility by climate models of cloud radiative forcing associated with tropical convection Reviewed

Ichikawa, H., H. Masunaga, Y. Tsushima, and H. Kanzawa

Journal of Climate Vol. 25 page： 1247-1262 2012

A satellite study of the atmospheric forcing and response to moist convection over tropical and subtropical oceans Reviewed

Hirohiko Masunaga

Journal of the Atmospheric Sciences Vol. 69 page： 150-167 2012

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Satellite data are analyzed to explore the thermodynamic evolution of tropical and subtropical atmospheres
prior and subsequent to moist convection in order to offer an observational test bed for convective adjustment,
which is central to the quasi-equilibrium hypothesis. Tropical Rainfall Measuring Mission (TRMM)
and Aqua satellite measurements are projected onto a composite temporal sequence over an hourly to daily
time scale by exploiting the temporal gap between the local satellite overpasses, which changes from one day
to another. The atmospheric forcing and response to convection are investigated separately for deep convective
and congestus clouds. In the deep tropics, systematic moisture transport from the atmospheric
boundary layer (ABL) to the free troposphere is evident in association with deep convection. The quick ABL
ventilation suggests a swift convective adjustment but is preceded by a steady buildup ofABLmoisture, which
does not imply continuous adjustment to equilibrium. The evolution of convective available potential energy
(CAPE) is controlled not only by the ABL moisture but also largely by a coincident ABL cooling linked with
a bipolar anomaly of tropospheric temperature. The ABL moisture and temperature effects together lead to
a rapid drop of CAPE for 12 h preceding convection, followed by a restoring phase that emerges as the cool
anomaly recovers for a day or two. When moist convection is brought by congestus clouds with no deep
convection nearby, CAPE gently increases over a period of 1-2 days until congestus occurs and then declines
as slowly, suggestive of no efficient convective adjustment. The subtropical atmosphere shows no sign of
convective adjustment whether or not vigorous convection is present.

Equatorial asymmetry of the east Pacific ITCZ: Observational constraints on the underlying processes Reviewed

Masunaga, H. and T. S. L'Ecuyer

J. Climate Vol. 24 page： 1784-1800 2011.3

Satellite Data Simulator Unit (SDSU): A multi-sensor, multi-spectral satellite simulator package Reviewed

Masunaga, H., T. Matsui, W.-K. Tao, A. Y. Hou, C. D. Kummerow, T. Nakajima, P. Bauer, W. S. Olson, M. Sekiguchi, and T. Y. Nakajima

Bull. Amer. Meteorol. Soc. Vol. 91 page： 1625-1632 2010.12

Improving a spectral bin microphysical scheme using TRMM satellite observations Reviewed

Li, X., W.-K. Tao, T. Matsui, C. Liu, and H. Masunaga

Quart. J. Roy. Meteor. Soc. Vol. 136 page： 382-399 2010

Language：English Publishing type：Research paper (scientific journal)

TRMM-observed mature-stage squall lines during late spring and early summer
in the central USA over a 9-year period are compiled and compared with a case
simulation by the Goddard Cumulus Ensemble (GCE) model with a spectral bin
microphysical scheme. During the quasi-steady state of the simulation, a forward
radiative transfer model calculates TRMM Precipitation Radar (PR) reflectivity
and 85 GHz brightness temperatures from simulated particle size distributions.
Comparisons between model and TRMM observations using radar Contoured
Frequency with Altitude Diagrams (CFADs) and 85 GHz brightness temperature
probability density distributions are performed, in addition to CFADs from a surface
C-band radar for the same case. Radar CFADs comparisons reveal that the model
overestimates sizes of snow/aggregates in the stratiform region.
Three sets of sensitivity tests are carried out in order to improve the simulated
radar reflectivity profiles: increase of aggregates' density and terminal fall velocity;
changing temperature dependency of collection efficiency between ice-phase
particles, particularly those of the plate-type; and adding a break-up scheme for
large aggregates. While all three approaches mitigate the discrepancies, changing
collection efficiency produces the best match in magnitudes and characteristics
of radar CFADs. In addition, interactions between ice- and water-phase particles
also need to be adjusted in order to have good comparisons in both radar CFADs
and 85 GHz brightness temperature distributions. This study shows that long-term
satellite observations, especially those with multiple sensors, can be very useful in
constraining model microphysics.

The southeast Pacific warm band and double ITCZ Reviewed

Masunaga, H. and T. S. L'Ecuyer

J. Climate Vol. 23 page： 1189-1208 2010

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

The east Pacific double intertropical convergence zone (ITCZ) in austral fall is investigated with particular
focus on the growing processes of its Southern Hemisphere branch. Satellite measurements from the Tropical
Rainfall Measuring Mission (TRMM) and Quick Scatterometer (QuikSCAT) are analyzed to derive 8-yr
climatology from 2000 to 2007. The earliest sign of the south ITCZ emerges in sea surface temperature (SST)
by January, followed by the gradual development of surface convergence and water vapor. The shallow
cumulus population starts growing to form the south ITCZ in February, a month earlier than vigorous deep
convection is organized into the south ITCZ. The key factors that give rise to the initial SST enhancement or
the southeast Pacific warm band are diagnosed by simple experiments. The experiments are designed to
calculate SST, making use of an ocean mixed layer ``model'' forced by surface heat fluxes, all of which are
derived from satellite observations. It is found that the shortwave flux absorbed into the ocean mixed layer is
the primary driver of the southeast Pacific warm band. The warm band does not develop in boreal fall because
the shortwave flux is seasonally so small that it is overwhelmed by other negative fluxes, including the latent
heat and longwave fluxes. Clouds offset the net radiative flux by 10–15 W m22, which is large enough for the
warm band to develop in boreal fall if it were not for clouds reflecting shortwave radiation. Interannual
variability of the double ITCZ is also discussed in brief.

A 9-season TRMM observation of the Austral Summer MJO and Low-frequency Equatorial Waves Reviewed

Masunaga, H.

J. Meteor. Soc. Japan Vol. 87A page： 295-315 2009

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

A long-term observation from the Tropical Rainfall Measuring Mission (TRMM) is analyzed to investigate the Madden-Julian Oscillation (MJO), Kelvin wave, and equatorial Rossby (ER) wave in austral summer seasons. TRMM Precipitation Radar (PR) and Visible/Infrared Scanner (VIRS) measurements are jointly used to clarify convective progression associated with individual modes of the tropical oscillations. Variability in the dynamic and thermodynamic environment involving sea surface temperature (SST), column relative humidity (CRH), and moisture convergence is also examined. A sea surface warming is found to precede the peak MJO convection by ∼ 10 days, while a prior SST increase is not as evident for the Kelvin and ER waves. Moisture convergence and CRH exhibit a horseshoe-like pattern in the composite MJO map, constituted of a pair of off-equatorial maxima and a weak equatorial peak. The Kelvin wave has a moist anomaly on the equator leading the convective peak as theoretically expected, while the moist anomaly also extends poleward without being accompanied by moisture convergence. Moisture convergence leads CRH by a day or two for the Kelvin and ER waves. Moisture convergence is, in contrast, virtually concurrent with CRH for the MJO. The correlation between CRH and deep stratiform coverage is diverse among the three modes of the tropical oscillations. Shallow cumulus and cumulus congestus lead the MJO convective peak by ∼ 1 day, followed by lingering non-precipitating high clouds. ER wave convection is led by moisture convergence but lagged by CRH. The convective progression appears not to proceed in a monotonic way for the ER wave.
A possible mechanism to explain MJO propagation is discussed as suggested by a synthesis of the present findings. The Kelvin wave guides the eastward migration of MJO convection onset over the Indian Ocean. The role of the Kelvin wave in MJO propagation diminishes as the MJO enters the west Pacific with the convective are

An MJO simulated by the NICAM at 14-km and 7-km resolutions Reviewed

Liu, P., M. Satoh, B. Wang, H. Fudeyasu, T. Nasuno, T. Li, H. Miura, H. Taniguchi, H. Masunaga, X. Fu, and H. Annamalai

Mon. Wea. Rev. Vol. 137 page： 3254-3268 2009

Language：English Publishing type：Research paper (scientific journal)

This study discloses detailed Madden–Julian oscillation (MJO) characteristics in the two 30-day integrations
of the global cloud-system-resolving Nonhydrostatic Icosahedral Atmospheric Model (NICAM) using the allseason
real-time multivariateMJO index ofWheeler and Hendon. The model anomaly is derived by excluding
the observed climatology because the simulation is sufficiently realistic.Results showthat theMJOhas a realistic
evolution in amplitude pattern, geographical locations, eastward propagation, and baroclinic- and westwardtilted
structures. In the central IndianOcean, convection develops with the low-level easterlywind anomaly then
matures where the low-level easterly and westerly anomalies meet. Anomalous moisture tilts slightly with
height. In contrast, over the western Pacific, the convection grows with a low-level westerly anomaly.Moisture
fluctuations, leading convection in eastward propagation, tilt clearly westward with height. The frictional
moisture convergence mechanism operates to maintain the MJO. Such success can be attributed to the explicit
representation of the interactions between convection and large-scale circulations. The simulated event, however,
grows faster in phases 2 and 3, and peaks with 30%higher amplitude than that observed, although the 7-km
version shows slight improvement. The fast-growth phases are induced by the fast-growing low-level convergence
in the IndianOcean and the strongly biased ITCZ in the west Pacific when themodel undergoes a spinup.
The simulated OLR has a substantial bias in the tropics. Possible solutions to the deficiencies are discussed.
1. Introduction
The Madden–Julian oscillation (MJO; Madden and
Julian 1971, 1972, 1994) dominates tropospheric variability
in the tropics on time scales of 30–60 days. The
oscillation influences weather and climate variability
substantially in both the tropics (e.g., Yasunari 1979;
Hendon and Liebmann 1990; Lawrence and Webster
2002) and

Evaluation of Precipitation and High-level Cloud Areas Associated with Large-scale Circulation over the Tropical Pacific in the CMIP3 Models Reviewed

Ichikawa, H., H. Masunaga, and H. Kanzawa

J. Meteor. Soc. Japan Vol. 87 page： 771-789 2009

Language：English Publishing type：Research paper (scientific journal)

Precipitation and high-level cloud (HLC) areas in association with the large-scale circulation over the tropical
Pacific are analyzed for simulations of nineteen Coupled Model Intercomparison Project Phase 3 (CMIP3) models
with observations for 16 years of 1984–1999. The distribution of rainfall and HLC areas are composited around
the geographical center of tropospheric upper-level (200 hPa) divergence (DIV) along Intertropical Convergence
Zone (ITCZ) using monthly anomaly data. Datasets with a finer temporal sampling than monthly means were
not available for the present purposes. The most notable feature is that the horizontal spread of enhanced circulation
and the related rainfall and HLC areas are all underestimated around the DIV center in the models compared
to the observation. Particularly, the underestimation is pronounced in HLC, presumably owing to di‰culties
in the physical processes relevant to the spatial distribution of HLC area. In general, a model with a higher
correlation between the large-scale circulation field and rainfall tends to have a wider spread of HLC area around
the DIV center.

A Joint Satellite and Global Cloud-Resolving Model Analysis of a Madden-Jullian Oscillation Event: Model Diagnosis Reviewed

Masunaga, H., M. Satoh, and H. Miura

J. Geophys. Res. Vol. 113 ( D17210 ) page： doi:10.1029/2008JD009986 2008.9

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

In this study, a methodology to diagnose a global cloud-resolving model (GCRM) is explored on the basis of a joint analysis with satellite measurements. The Madden-Julian Oscillation experiment carried out with the Nonhydrostatic Icosahedral Atmospheric Model (NICAM) is used as the test bed. The NICAM output is compared with Tropical Rainfall Measuring Mission (TRMM) and CloudSat measurements in terms of composite analysis, contoured frequency by altitude diagrams (CFADs), and the joint histogram of cloud top and precipitation top heights. It is found in the composite diagram that the GCRM reproduces a slow, eastward migration of a convective envelope well comparable
to the satellite measurement. The GCRM CFAD qualitatively reproduces TRMM and CloudSat CFADs, except that the GCRM tends to overly produce snow in deep convection. The joint histograms reveal that, while the overproduction of snow is evident, NICAM-simulated snow is incapable of producing 94-GHz radar echoes higher than 5 dBZ. This deficiency can be mitigated by a modification to microphysical parameterization in the way that a proportion of small particles is enhanced in the snow mass spectrum.

*Seasonality and Regionality of the Madden-Julian Oscillation, Kelvin Wave, and Equatorial Rossby Wave. Reviewed

Masunaga, H.

J. Atmos. Sci. Vol. 64 page： 4400-4416 2007.12

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

The Madden–Julian oscillation (MJO), Kelvin wave, and equatorial Rossby (ER) wave—collectively
called intraseasonal oscillations (ISOs)—are investigated using a 25-yr record of outgoing longwave radiation
(OLR) measurements as well as the associated dynamical fields. The ISO modes are detected by
applying bandpass filters to the OLR data in the frequency–wavenumber space. An automated wavetracking
algorithm is applied to each ISO mode so that convection centers accompanied with the ISOs are
traced in space and time in an objective fashion. The identified paths of the individual ISO modes are first
examined and found strongly modulated regionally and seasonally. The dynamical structure is composited
with respect to the convection centers of each ISO mode. A baroclinic mode of the combined Rossby and
Kelvin structure is prominent for the MJO, consistent with existing work. The Kelvin wave exhibits a
low-level wind field resembling the shallow-water solution, while a slight lead of low-level convergence over
convection suggests the impact of frictional boundary layer convergence on Kelvin wave dynamics. A lagged
composite analysis reveals that the MJO is accompanied with a Kelvin wave approaching from the west
preceding the MJO convective maximum in austral summer. MJO activity then peaks as the Kelvin and ER
waves constructively interfere to enhance off-equatorial boundary layer convergence. The MJO leaves a
Kelvin wave emanating to the east once the peak phase is passed. The approaching Kelvin wave prior to the
development of MJO convection is absent in boreal summer and fall. The composite ER wave, loosely
concentrated around the MJO, is nearly stationary throughout. A possible scenario to physically translate
the observed result is also discussed.

*The Madden-Julian Oscillation Recorded in Early Observations from the Tropical Rainfall Measuring Mission (TRMM). Reviewed

Masunaga, H., T. S. L'Ecuyer, and C. D. Kummerow

J. Atmos. Sci. Vol. 63 page： 2777-2794 2006.11

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

A satellite data analysis is performed to explore the Madden–Julian oscillation (MJO) focusing on the
potential roles of the equatorial Rossby (ER) and Kelvin waves. Measurements from the Tropical Rainfall
Measuring Mission (TRMM) Precipitation Radar (PR) and Visible/Infrared Scanner (VIRS) are analyzed
in the frequency–wavenumber domain to identify and ultimately filter primary low-frequency modes in the
Tropics. The space–time spectrum of deep-storm fraction estimated by PR and VIRS exhibits notable
Kelvin wave signals at wavenumbers 5–8, a distinct MJO peak at wavenumbers 1–7 and periods of about 40
days, and a signal corresponding to the ER wave. These modes are separately filtered to study the individual
modes and possible relationship among them in the time–longitude space. In 10 cases analyzed here, an
MJO event is often collocated with a group of consecutive Kelvin waves as well as an intruding ER wave
accompanied with the occasional onset of a stationary convective phase. The spatial and temporal relationship
between the MJO and Kelvin wave is clearly visible in a lag composite diagram, while the ubiquity
of the ER wave leads to a less pronounced relation between the MJO and ER wave. A case study based on
the Geostationary Meteorological Satellite (GMS) imagery together with associated dynamic field captures
the substructure of the planetary-scale waves. A cross-correlation analysis confirms the MJO-related cycle
that involves surface and atmospheric parameters such as sea surface temperature, water vapor, low clouds,
shallow convection, and near-surface wind as proposed in past studies. The findings suggest the possibility
that a sequence of convective events coupled with the linear waves may play a critical role in MJO
propagation. An intraseasonal radiative–hydrological cycle inherent in the local thermodynamic conditions
could be also a potential factor responsible for the MJO by loosely modula

Observations of Tropical Precipitating Clouds Ranging from Shallow to Deep Convective Systems. Reviewed

Masunaga, H., and C. D. Kummerow

Geophys. Res. Lett. Vol. 33 ( L16805 ) page： doi:10.1029/2006GL026547 2006.8

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Regional and temporal variability in a broad spectrum
of tropical precipitation systems is investigated in
conjunction with the large-scale environment. The
analysis utilizes four storm categories (Shallow, Cumulus
Congestus, Deep Stratiform, and Deep Convective)
determined from Tropical Rainfall Measuring Mission
(TRMM) measurements. Deep Stratiform and Deep
Convective systems are found to be clearly correlated
with large-scale circulation deduced from a reanalysis data
set, and are modulated by a distinct seasonal cycle over
land. The Shallow category is practically the only
component of tropical oceanic rainfall for cold sea
surfaces, while it gives way to deeper systems as SST
exceeds 28–29C. The cloud horizontal scale of organized
rainfall systems tends to be increasingly extensive relative
to the raining portion as the system becomes larger. The
present results are discussed in light of existing relevant
studies.

Satellite-based Assessment of Marine Low Cloud Variability Associated with Aerosol, Atmospheric Stability, and the Diurnal Cycles. Reviewed

Matsui, T., H. Masunaga, R. A. Pielke Sr., S. M. Kreidenweis, W.-K. Tao, M. Chin, and Y. J. Kaufman

J. Geophys. Res. Vol. 111 ( D17204 ) page： doi:10.1029/2005JD006097 2006

Language：English Publishing type：Research paper (scientific journal)

This study examines variability in marine low cloud properties derived from
semiglobal observations by the Tropical Rainfall Measuring Mission (TRMM) satellite, as
linked to the aerosol index (AI) and lower-tropospheric stability (LTS). AI is derived from
the Moderate Resolution Imaging Spectroradiometer (Terra MODIS) sensor and the
Goddard Chemistry Aerosol Radiation and Transportation (GOCART) model and is used
to represent column-integrated aerosol concentrations. LTS is derived from the NCEP/
NCAR reanalysis and represents the background thermodynamic environment in which
the clouds form. Global statistics reveal that cloud droplet size tends to be smallest in
polluted (high-AI) and strong inversion (high-LTS) environments. Statistical
quantification shows that cloud droplet size is better correlated with AI than it is with LTS.
Simultaneously, the cloud liquid water path (CLWP) tends to decrease as AI increases.
This correlation does not support the hypothesis or assumption that constant or increased
CLWP is associated with high aerosol concentrations. Global variability in corrected
cloud albedo (CCA), the product of cloud optical depth and cloud fraction, is very well
explained by LTS, while both AI and LTS are needed to explain local variability in
CCA. Most of the local correlations between AI and cloud properties are similar to the
results from the global statistics, while weak anomalous aerosol-cloud correlations
appear locally in the regions where simultaneous high (low) AI and low (high) LTS
compensate each other. Daytime diurnal cycles explain additional variability in cloud
properties. CCA has the largest diurnal cycle in high-LTS regions. Cloud droplet size and
CLWP have weak diurnal cycles that differ between clean and polluted environments.
The combined results suggest that investigations of marine low cloud radiative forcing and
its relationship to hypothesized aerosol indirect effects must consider the combined
effects of a

Variability in the Characteristics of Precipitation Systems in the Tropical Pacific.Part II: Implications for Atmospheric Heating Reviewed

TRISTAN S. L'ECUYER, HIROHIKO MASUNAGA, AND CHRISTIAN D. KUMMEROW

J. Cliamte Vol. 19 page： 1388-1406 2006

Language：English Publishing type：Research paper (scientific journal)

This paper explores changes in the principal components of observed energy budgets across the tropical
Pacific in response to the strong 1998 El Niño event. Multisensor observations from the Tropical Rainfall
Measuring Mission (TRMM) Microwave Imager (TMI), Visible and Infrared Scanner (VIRS), and precipitation
radar (PR) instruments aboard TRMM are used to quantify changes in radiative and latent
heating in the east and west Pacific in response to the different phases of the El Niño–Southern Oscillation.
In periods of normal east–west SST gradients there is substantial heating in the west Pacific and cooling in
the east, implying strong eastward atmospheric energy transport. During the active phase of the El Niño,
both the east and west Pacific tend toward local radiative–convective equilibrium resulting in their temporary
energetic decoupling. It is further demonstrated that the response of these regions to ENSO-induced
SST variability is directly related to changes in the characteristics of clouds and precipitation in each region.
Through quantitative analysis of the radiative and latent heating properties of shallow, midlevel, and deep
precipitation events and an equivalent set of nonprecipitating cloud systems, times of reduced atmospheric
heating are found to be associated with a shift toward shallow and midlevel precipitation systems and
associated low-level cloudiness. The precipitation from such systems is typically less intense, and they do not
trap outgoing longwave radiation as efficiently as their deeper counterparts, resulting in reduced radiative
and latent heating of the atmosphere. The results also suggest that the net effect of precipitating systems on
top-of-the-atmosphere (TOA) fluxes and the efficiency with which they heat the atmosphere and cool the
surface exhibit strong dependence on their surroundings. The sensitivity of cloud radiative impacts to the
atmospheric and surface properties

*Variability in the Characteristics of Precipitation Systems in the Tropical Pacific. Part I. Spatial Structure. Reviewed

Masunaga, H., T. S. L'Ecuyer, and C. D. Kummerow

J. Climate Vol. 18 page： 823-840 2005

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Regional and temporal variability in the vertical and horizontal characteristics of tropical precipitating
clouds are investigated using the Precipitation Radar (PR) and the Visible and Infrared Scanner (VIRS) on
board the Tropical Rainfall Measuring Mission (TRMM) satellite. The present study focuses on the three
oceanic regions (west, central, and east Pacific) together with two continental regions for comparison and
the two separate time periods (February 1998 and February 2000) under different phases of the El Niño–
Southern Oscillation (ENSO) in order to examine regional and ENSO-related variations. The height
spectrums of storms are investigated in terms of radar echo-top height and infrared brightness temperature.
The variability in the spectrum clearly correlates with the large-scale circulation and its ENSO-related
change. On the basis of the height spectrum, storm systems are classified into the four categories of shallow,
cumulus congestus, deep stratiform, and deep convective. The deep stratiform and deep convective categories,
both of which have very cold cloud tops, are differentiated by radar echo-top heights so that deep
convective systems are accompanied with an appreciable amount of large frozen particles aloft. While
shallow events are dominant in the probability of occurrence over relatively cold oceans, deep convective
systems take their place for warmer sea surface temperatures (SSTs). The turnover occurs at the SST
threshold of 28°–29°C for all the oceanic regions and years investigated except the west Pacific in 2000, for
which deep convective systems prevail over the entire range of SST. Rain correlation-scale length (RCSL)
and cloud correlation-scale length (CCSL) are introduced as statistical indicators of the horizontal scale of
storms. While the RCSL is 8–18 km for shallow- and cumulus congestus–type clouds without significant
regional and temporal variations, the RCSL and CCSL associate

*Combined Radar and Radiometer Analysis of Precipitation Profiles for a Parametric Retrieval Algorithm. Reviewed

Masunaga, H. and C. D. Kummerow

J. Atmos. Oceanic Tech. Vol. 22 page： 909-929 2005

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

A methodology to analyze precipitation profiles using the Tropical Rainfall Measuring Mission (TRMM)
Microwave Imager (TMI) and precipitation radar (PR) is proposed. Rainfall profiles are retrieved from PR
measurements, defined as the best-fit solution selected from precalculated profiles by cloud-resolving
models (CRMs), under explicitly defined assumptions of drop size distribution (DSD) and ice hydrometeor
models. The PR path-integrated attenuation (PIA), where available, is further used to adjust DSD in a
manner that is similar to the PR operational algorithm. Combined with the TMI-retrieved nonraining
geophysical parameters, the three-dimensional structure of the geophysical parameters is obtained across
the satellite-observed domains. Microwave brightness temperatures are then computed for a comparison
with TMI observations to examine if the radar-retrieved rainfall is consistent in the radiometric measurement
space. The inconsistency in microwave brightness temperatures is reduced by iterating the retrieval
procedure with updated assumptions of the DSD and ice-density models. The proposed methodology is
expected to refine the a priori rain profile database and error models for use by parametric passive
microwave algorithms, aimed at the Global Precipitation Measurement (GPM) mission, as well as a future
TRMM algorithms.

Impact of aerosols and atmospheric thermodynamics on cloudproperties within the climate system Reviewed

Toshihisa Matsui, Hirohiko Masunaga, and Roger A. Pielke Sr.

Geophys. Res. Lett. Vol. 31 ( L06109 ) page： doi:10.1029/2003GL019287 2004

Language：English Publishing type：Research paper (scientific journal)

A combination of cloud-top and columnar droplet sizes
derived from the multi Tropical Rainfall Measurement
Mission (TRMM) sensors reveals the sensitivity of the
aerosols effect on cloud-precipitation processes due to
environmental vertical thermodynamic structure. First, the
magnitude of aerosol indirect effect could be larger with
the analysis of columnar droplet sizes than that derived from
the cloud-top droplet sizes since column-droplet size can
account for the broader droplet spectra in the cloud layers.
Second, a combination of cloud-top and columnar droplet
sizes reveals that the warm rain process is prevented
regardless of the aerosols concentration under high static
stability such as when a strong temperature inversion exists,
while a high aerosol concentration suppresses the warm rain
formulation under low static stability.

Physical Properties of Maritime Low Clouds as Retrieved by Combined Use of TRMM Microwave Imager and Visible/Infrared Scanner. Algorithm. Reviewed

Masunaga, H., T. Y. Nakajima, T. Nakajima, M. Kachi, R. Oki, and S. Kuroda

J. Geophys. Res. Vol. 107 ( D10 ) page： doi:10.1029/2001JD000743 2002

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Satellite remote sensing studies on the microphysical and optical properties of clouds have
constructed an active research field in the last decades. Clouds are observed over a wide spectral
range from the visible/infrared to the microwave, and either shortwave or microwave measurement
is used to evaluate the liquid water path (LWP). On the other hand, to date, there have been few
cloud studies based on combined measurement by a visible/infrared imager and a microwave
radiometer aboard the same platform. In this paper a physical inversion algorithm for the combined
use of visible/infrared and microwave sensors is proposed to retrieve the cloud physical quantities
such as LWP and the effective droplet radius, each of which is determined in two different ways.
The current version of the algorithm has been developed for application to the Tropical Rainfall
Measurement Mission (TRMM) sensors, i.e., Visible and Infrared Scanner (VIRS) and TRMM
Microwave Imager (TMI). The cloud top temperature obtained from the VIRS analysis is used as an
input to the TMI analysis to reduce uncertainties in estimation of LWP. Total errors in LWP are
estimated to range from 11 to 30 g /m2. In the algorithm the beam-filling efficiency of clouds for
TMI footprints is corrected by the cloud fraction evaluated from the VIRS measurements. For
application, global analysis is performed with 3-monthly data from January to March 2000. The
scatter diagram of the shortwave-retrieved LWP (LWPshrt) versus the microwave-retrieved LWP
(LWPmicr) shows characteristic trends for both precipitating and nonprecipitating clouds. Vertical
inhomogeneity of the cloud droplet size accounts for small excess of LWPshrt over LWPmicr for
nonprecipitating clouds, while precipitating clouds produce LWPmicr larger than LWPshrt, owing to
the presence of raindrops. These tendencies are reinforced by examination of the global
distributions of the shortwave-retrieved droplet radius Re (NV) and the microwa

Comparison of Rainfall Products Derived from TRMM Microwave Imager and Precipitation Radar. Reviewed

Masunaga, H., T. Iguchi, R. Oki, and M. Kachi

J. Applied Meteor. Vol. 41 page： 849-862 2002

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Satellite remote sensing is an indispensable means of measuring and monitoring precipitation on a global scale.
The Tropical Rainfall Measuring Mission (TRMM) is continuing to make significant progress in helping the global
features of precipitation to be understood, particularly with the help of a pair of spaceborne microwave sensors,
the TRMM Microwave Imager (TMI) and precipitation radar (PR). The TRMM version-5 standard products,
however, are known to have a systematic inconsistency in mean monthly rainfall. To clarify the origin of this
inconsistency, the authors investigate the zonal mean precipitation and the regional trends in the hydrometeor
profiles in terms of the precipitation water content (PWC) and the precipitation water path (PWP) derived from
the TMI profiling algorithm (2A12) and the PR profile (2A25). An excess of PR over TMI in near-surface PWC
is identified in the midlatitudes (especially in winter), whereas PWP exhibits a striking excess of TMI over PR
around the tropical rainfall maximum. It is shown that these inconsistencies arise from TMI underestimating the
near-surface PWC in midlatitude winter and PR underestimating PWP in the Tropics. This conclusion is supported
by the contoured-frequency-by-altitude diagrams as a function of PWC. Correlations between rain rate and PWC/
PWP indicate that the TMI profiling algorithm tends to provide a larger rain rate than the PR profile under a given
PWC or PWP, which exaggerates the excess by TMI and cancels the excess by PR through the conversion from
precipitation water to rain rate. As a consequence, the disagreement in the rainfall products between TMI and PR
is a combined result of the intrinsic bias originating from the different physical principles between TMI and PR
measurements and the purely algorithmic bias inherent in the conversion from precipitation water to rain rate.

Physical Properties of Maritime Low Clouds as Retrieved by Combined Use of TRMM Microwave Imager and Visible/Infrared Scanner. II. Climatology of Warm Clouds and Rain. Reviewed

Masunaga, H., T. Y. Nakajima, T. Nakajima, M. Kachi, and K. Suzuki

J. Geophys. Res Vol. 107 ( D19 ) page： doi:10.1029/2001JD001269 2002

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

In this paper, we investigate characteristics of low clouds and warm-rain production in
terms of droplet growth based on the effective droplet radii retrieved by a combined use of
visible, infrared, and microwave satellite remote sensing. We propose to categorize low
clouds into the following groups: (1) nondrizzling, nonraining clouds; (2) nonraining
clouds with drizzling near the cloud top; (3) raining clouds; and (4) clouds with no clear
interpretation in terms of the effective radii derived using two different schemes. This
categorization is supported by examination of the correlation between static stability and
the retrieved results in the three ``precipitating regions'' (the Middle Pacific, South Pacific
Convergence Zone [SPCZ], and Intertropical Convergence Zone [ITCZ] cumulus regions)
and in the four ``nonprecipitating regions'' (the Californian, Peruvian, Namibian, and
eastern Asian stratus regions). The rain rate derived by Precipitation Radar (PR) provides
global characteristics consistent with our results. Californian and Peruvian stratus clouds
are found to frequently have the drizzle mode near the cloud top, whereas Namibian strati
have fewer chances to drizzle. The drizzle mode almost completely disappears in the
eastern Asian region in the winter. The cloud–aerosol interaction is a promising candidate
for suppressing the drizzle mode formation in nonprecipitating clouds.

The Effective Cloud Fraction of Broken Clouds Obtained by Multi-stream Radiative Transfer. I. Longwave Radiation Reviewed

Masunaga, H. and T. Nakajima

J. Atmos. Sci. Vol. 58 page： 2455-2467 2001

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

The influence of broken clouds on radiative flux has provided a major source of uncertainty in radiative
transfer models of the atmosphere because plane-parallel approximations are assumed in most of the current
atmospheric models, where horizontal inhomogeneity cannot be adequately taken into account. In this paper,
effects by cloud inhomogeneity on longwave radiation fields are investigated, using a simple model of a cloud
array that consists of identical cuboids following some past studies. In contrast to past work that adopted simplified
formulations of radiative transfer, multistream radiative transfer is considered to obtain the exact solutions of
radiative flux, which enable us to consider semitransparent clouds as well as optically thick clouds in desirable
accuracy. Applicability to semitransparent clouds is important because cirrus clouds, which are considered to
play significant roles for longwave radiation, are often semitransparent to infrared radiation.
The computational results show that the empirical formula previously derived by Harshvardhan and Weinman
systematically underestimates the effective cloud fraction. An alternative formula is proposed for the effective
cloud fraction to supply a better fit to the exact solution of radiative flux. Furthermore, new formulas are derived
to approximate the exact solutions including the dependence on the optical thickness of clouds. They are useful
to convert plane-parallel flux to 3D flux passing through broken clouds, either for optically thick or thin clouds.

A Radiation Hydrodynamic Model for Protostellar Collapse II. The Second Collapse and The Birth of a Protostar. Reviewed

Masunaga, H. and Inutsuka, S.

Astrophys. J. Vol. 531 page： 350-365 2000

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

carry out radiation hydrodynamic calculations to study physical processes in the formation of a 1
M protostar. Following our previous work, calculations pursue the whole evolution from the beginning _
of the Ðrst collapse to the end of the main accretion phase. The adiabatic core formed after the initial
collapse (i.e., the Ðrst core) experiences further gravitational collapse triggered by dissociation of molecular
hydrogen, which leads to the formation of the second core, i.e., the birth of a protostar. The protostar
grows in mass as accreting the infalling material from the circumstellar envelope, while the protostar
keeps its radius at D4 R during the main accretion phase. These typical features in the evolution are in _
good agreement with previous studies. We consider two dierent initial conditions for the density distribution
: homogeneous and hydrostatic cloud cores with the same central density of 1.415]10~19 g
cm~3 . The homogeneous core has the total mass of 1 M while the hydrostatic core has 3.852 For _ M_.
the initially homogeneous model, the accretion luminosity rapidly rises to the maximum value of 25 L _
just after the birth of a protostar, and declines gradually as the mass accretion rate decreases. In contrast,
the luminosity increases monotonically with time for the initially hydrostatic model. This dierence
arises because the mass accretion rate varies depending on the inward acceleration at the initial stage,
which aects the luminosity curve. A less massive hydrostatic core would possess the similar properties
in the luminosity curve to the 3.852 M case, because a hydrostatic cloud core with mass lower than _
3.852 M can be shown to provide a smaller mass accretion rate after the birth of a protostar and a _
more gradual rise in the luminosity curve. Our numerical code is designed to provide the evolution of
the spectral energy distribution (SED) along with the dynamical evolution in our spherically sym

Infall Signatures in Molecular Line Spectra of Protostellar Envelopes. Reviewed

Masunaga, H. and Inutsuka, S.

Astrophys. J. Vol. 536 page： 406-415 2000

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

A double-peaked proÐle with a stronger blue peak in a molecular line spectrum is considered strong
evidence for the infall motion in the gas envelope surrounding a protostar. Some past studies performed
model calculations for reproducing observed spectral proÐles using simpliÐed dynamical models such as
isothermal similarity solutions. However, validity of the similarity solutions for spectral line synthesis
should be examined in comparison with more realistic dynamical models.
In this paper we carry out theoretical modeling of molecular line spectra, adopting a spherically symmetric
radiation hydrodynamical model for protostar formation taken from a recent work by the
authors. This study concentrates on how infall motions could account for the asymmetric line proÐles
observed toward protostellar sources. We do not explicitly consider the eects of rotation and outÑows
on the generation of line proÐles. In our numerical code for the non-LTE line transfer, the level populations
are fully consistent with the radiation Ðeld under an arbitrary physical structure in spherical symmetry,
and hence, reliable spectral synthesis has been enabled and compared to the LTE, large velocity
gradient (or Sobolev), and microturbulence approximations.
Contrary to the remarks by Zhou, we do not Ðnd an overestimation of line widths, although the
dynamical evolution resembles the Larson-Penston solution rather than the expansion-wave solution.
Furthermore, the infall motion produces wings extending to v\^2 km s~1 in line spectra, in contrast
to previous works where wings could not be produced by infall models. These results imply that simpli-
Ðed infall models, such as the isothermal similarity solutions adopted by previous authors, are not
always suitable to the detailed modeling of line spectra.

Does "t @ 1" Terminate the Isothermal Evolution of Collapsing Clouds? Reviewed

Masunaga, H. and Inutsuka, S.

Astrophys. J. Vol. 510 page： 822-827 1999

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

We examine when gravitationally collapsing clouds terminate their isothermal evolution. According to
our previous work, the condition with which isothermality is broken down is classiÐed into three cases,
i.e., when (1) the compressional heating rate overtakes the thermal cooling rate, (2) the optical depth for
thermal radiation reaches unity, or (3) the compressional heating rate becomes comparable with the
energy transport rate because of radiative diusion. In the present paper this classiÐcation is extended to
dmiseoontrhseietirgemesnawelrieatvhl ovwluahltuiiocehns otchef eatssheeesciwonnhitdeiiantlioccnalsoseuad1retoesrma3tpiseiÐsreasdtau.triFesÐoTeridnp,itlaaanundsdibcloaepseavca2iltuyheasis,onfaonTdisniigtwnaeinÐddceatine,cremw. eiWneÐentdehmethpcahrtiatsitcihzaeel
that the condition of qB1 ÏÏ never terminates isothermality, but nonisothermal evolutions begin either
earlier or later depending on the initial temperature and opacity. This result contrasts with the conventional
idea that opaqueness breaks isothermality. On the basis of the critical density discussed above, the
minimum Jeans mass for fragmentation, MF, is reconsidered. In contrast to the results by previous
authors that MF is insensitive to Tinit and i, we Ðnd that MF can be substantially larger than the typical
value of D10~2 M depending on and i. In particular, increases with decreasing metallicity, _ Tinit MF
MFPi~1, for low-metal clouds. A cloud with i\10~4 cm2 g~1 and Tinit\10 K yields MF\3.7 M_.
Finally, our critical densities would be helpful for hydrodynamic simulations that are intended to simply
handle the hardening of the equation of state.

A Radiation Hydrodynamic Model for Protostellar Collapse I. The First Collapse. Reviewed

Masunaga, H., Miyama, S.M., and Inutsuka, S.

Astrophys. J. Vol. 495 page： 346-369 1998

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Dynamical collapse of a molecular cloud core and the formation of a star are investigated by performing
radiation hydrodynamic calculations in spherical symmetry. The angle-dependent and
frequency-dependent radiative transfer equation is solved without any di†usion approximations, and the
evolution of the spectral energy distribution (SED) is examined.
In the present paper, as the Ðrst step in a series of our work, evolutions before hydrogen molecules
begin to dissociate (the so-called Ðrst collapse) are examined for di†erent masses and initial temperatures
of the parent cloud cores and for di†erent opacities. Numerical results for a typical case [Tinit\10 K
and iP(10 K)D0.01 cm2 g~1] show that the radius and mass of the Ðrst core are D5 AU and D0.05
M respectively. These values are independent both of the mass of the parent cloud core and of the _,
initial density proÐle. The analytical expressions for the radius, mass, and accretion luminosity of the
Ðrst core are also obtained. The SED contains only cold components of a few times 10 K throughout
the Ðrst collapse phase, because the opaque envelope veils the Ðrst core from observers. We suggest that
the molecular cloud cores with luminosities higher than D0.1 L should contain young protostars deep _
in the center, even if they show no evidence for the existence of central stars in near-infrared and optical
observations.

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