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JMSJ, 2013, Vol. 91, No. 6 (December)

Articles

Noda et al. (2013)

Noda, A. T., K. Nakamura, T. Iwasaki, and M. Satoh, 2013: A numerical study of a stratocumulus-topped boundary layer: Relations of decaying clouds with a stability parameter across inversion. J. Meteor. Soc. Japan, 91, 727-746.
http://dx.doi.org/10.2151/jmsj.2013-601   Graphical Abstract

Highlights:

• The mechanisms underlying a quasi-linear relation between liquid water path (LWP) and the so-called Randall's stability parameter, k (Fig. 1), are investigated, focusing on the transient phase in large-eddy simulations of marine stratocumulus clouds.
• The gradual development of an interfacial layer due to mixing of cold humid air below a cloud top and warmer dry air above it, acts to reduce the negative buoyancy of the mixture of the two air masses. Negative buoyancy reduces faster with k. The system reaches quasi-equilibrium by balancing buoyancy generation and dissipation of turbulent kinetic energy over a time scale of about 2 hr, which corresponds to a few turnover times of boundary-layer eddies.
• The mixing fraction (i.e., the fractional volume of boundary-layer air) reaches a value of about 0.1, corresponding to the maximum available negative buoyancy due to mixing. This shows a possible positive feedback between turbulence and evaporatively generated negative buoyancy (Fig. 2).

Ishizaka et al. (2013)

Ishizaka, M., H. Motoyoshi, S. Nakai, T. Shiina, T. Kumakura, and K. Muramoto, 2013: A new method for identifying the main type of solid hydrometeors contributing to snowfall from measured size–fall speed relationship. J. Meteor. Soc. Japan, 91, 747–762.
http://dx.doi.org/10.2151/jmsj.2013-602   Graphical Abstract

Highlights:

• To evaluate the contribution of measured particles to precipitation, the mass flux, defined as the product of mass and fall speed, was introduced. And the mass flux of a hydrometeor with size d and fall speed ν is estimated from the empirical size-mass and size–fall speed relationships, resulting in the mass flux table or the mass flux chart (Fig. 1 left).
• Furthermore, we introduced the center of mass flux distribution in the size–fall speed coordinates, CMF (the averages of size and fall speed weighted by the mass flux), derived from the number of measured particles and their estimated mass flux, which can acquire with appropriate apparatus such as an optical disdrometer (Fig. 1 right).
• The CMF locations varied in the size–fall speed coordinates according to the dominant hydrometeors, reflecting slight differences in both size and snow type (Fig. 2). Accordingly we can quantitatively identify the main type of precipitation particles mainly contributing to a targeted snowfall from the location of the CMF (New Method).

Lim et al. (2013)

Lim, S., D. Moisseev, V. Chandrasekar, and D. R. Lee, 2013: Classification and quantification of snow based on spatial variability of radar reflectivity. J. Meteor. Soc. Japan, 91, 763-774.
http://dx.doi.org/10.2151/jmsj.2013-603   Graphical Abstract

Highlights:

• The proposed classification methodology divides snow particle types into crystals, aggregates, rimed snow and high density snow (graupel). Differently from other classification schemes presented in literature, the method uses spatial continuity of the radar reflectivity field as well as reflectivity observations.
• The method uses snow type identification to guide the choice of the particular parameters of power law relations of equivalent radar reflectivity factor-liquid equivalent snow rate. This technique can reduce variation of quantitative snowfall estimation due to difference in physical properties of snow particles (Fig. 1).

Ito et al. (2013)

Ito, T., and H. Kanehisa, 2013: Analytical solutions of vortex Rossby waves in a discrete barotropic model. J. Meteor. Soc. Japan, 91, 775-788.
http://dx.doi.org/10.2151/jmsj.2013-604   Graphical Abstract

Highlights:

• The initial value problem of vortex Rossby waves (VRWs) is analytically solved in a linearized barotropic system on an ƒ plane. The basic axisymmetric vorticity q is assumed to be piecewise uniform in the radial direction (see Fig.1).
• For a basic vorticity q with an annular vorticity ring ( r₁ < r < r₂ in Figs.1,2), and if the radial distribution of q satisfies a certain additional condition (the Fjørtoft condition), the solution with azimuthal wave number |m|≠1 exponentially or linearly grows in time as a result of the interaction of counterpropagating VRWs at the edges of the ring (see Fig.2).
• Although the solution with |m|=1 cannot exponentially grow for any q, it can grow as a linear function of time. This linear growth may be regarded as a result of the resonance between two internal modes of the system.

Sasaki et al. (2013)

Sakai, T., T. Nagai, N. Orikasa, Y. Zaizen, K. Yamashita, Y. Mano, and M. Murakami, 2013: Aerosol characterization by dual-wavelength polarization lidar measurements over Kochi, Japan during the warm seasons of 2008 to 2010. J. Meteor. Soc. Japan, 91, 789-800.
http://dx.do5org/10.2151/jmsj.2013-605   Graphical Abstract

Highlights:

• The particle backscattering coefficient at 532 nm correlated well with the number concentration of aerosols with diameter exceeding 0.3 m (correlation coefficient = 0.89).
• The depolarization ratio (δ) was high (20%) and the backscatter wavelength exponent (å) was low (<0.5) between altitudes of 4 and 6 km, and they were low (δ = 2.5%) and moderate (å = 0.7) between 0.5 and 1.0 km, suggesting the presence of supermicrometer-sized, non-spherical particles in the upper altitude range and a predominance of submicrometer-sized particles and/or spherical particles in the lower altitude range. These values were consistent with aircraft measurements, indicating the presence of supermicrometer-sized mineral particles in the upper altitude range and a predominance of submicrometer-sized sulfates and supermicrometer-sized sea-salt droplets at lower altitude.
• Our results demonstrate the utility of lidar data for aerosol characterization, although further improvement of CCN characterization by lidar is necessary.

Li et al. (2013)

Li, X., and X. Shen, 2013: Rain microphysical budget in the tropical deep convective regime: A 2-d cloud-resolving modeling study. J. Meteor. Soc. Japan, 91, 801-815.
http://dx.do5org/10.2151/jmsj.2013-606   Graphical Abstract

Highlights:

• Over 67% of total rainfall is associated with net rain source in which collection of cloud water by rain is larger than melting of precipitation ice to rain in the presence of upward motions throughout the troposphere.
• Over 26% of total rainfall is related to downward motions in the lower troposphere that leads to melting of precipitation ice as a major term in production of precipitation.
• About 15% of total rainfall corresponds to dynamic hydrometeor advection only.

Li et al. (2013)

Li, X., W.-K. Tao, H. Masunaga, G. Gu, and X. Zeng, 2013: Aerosol effects on cumulus congestus population over the tropical Pacific: A cloud-resolving modeling study. J. Meteor. Soc. Japan, 91, 817-833.
http://dx.doi.org/10.2151/jmsj.2013-607   Graphical Abstract

Highlights:

• A cloud-resolving model with spectral bin microphysical scheme shows that low aerosol concentration in background marine condition during TOGA-COARE experiment is conducive to the formation of cumulus congestus.
• Over the tropical oceans, where the low-level water vapor is abundant, the CAPE is relatively low, and a ubiquitous weak stable level exists near 0°C level, the small differences in latent heat release caused by aerosol-cloud-precipitation interactions can result in cloud population shift from congestus dominant to deep convection dominant.
• Considering the importance of congestus in tropical dynamics and MJO lifecycle, we proposed a hypothesis that aerosol-cloud-precipitation interactions in an ultra-clean marine environment may serve as an important damping mechanism for tropical convection.

Ren et al. (2013)

Ren, H.-L., F.-F. Jin, M. Stuecker, and R. Xie, 2013: ENSO regime change since the late 1970s as manifested by two types of ENSO. J. Meteor. Soc. Japan, 91, 835–842.
http://dx.doi.org/10.2151/jmsj.2013-608   Graphical Abstract

Highlights:

• This study aimed to develop a deep understanding of the ENSO regime change in the late 1970s by linking new observational evidence with previous studies, not only regarding the change in ENSO properties, but also the change in ENSO types (or ENSO mode stability).
• The ENSO regime change is predominantly manifested by the two types of ENSO: The dramatic changes of the CT ENSO properties such as amplitude, dominant ENSO period, and SST anomaly propagation characteristics (Fig. 1), and the frequent occurrence of the WP ENSO events.
• Observations strongly suggest that the WP and CT ENSO are independent quasi-biennial and quasi-quadrennial modes, respectively, of the tropical Pacific climate variability, and also suggest that these two ENSO modes have coexisted actively since the late 1970s when either El Niño or La Niña can be separated into the two modes (Fig. 2).