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JMSJ, 2016, Vol. 94, No. 1 (February)

Articles

Ichimaru et al. (2016)

Ichimaru, T., S. Noguchi, T. Hirooka, and H. Mukougawa, 2016: Predictability changes of stratospheric circulations in northern hemisphere winter. J. Meteor. Soc. Japan, 94, 7-24.
https://doi.org/10.2151/jmsj.2016-001  Graphical Abstract

Highlights:

• Practical predictability of the stratospheric circulation in the boreal winters during 2001-2006 is examined using the archive of the JMA 1-month ensemble forecasts based on the Root-Mean-Square Error (RMSE) and Anomaly Correlation (AC) for the 10-hPa geopotential height.
• The predictable period of the stratospheric circulation is estimated at about 10 days, and it exhibits large variability in comparison with that of the troposphere, which is associated with the large variation of the stratospheric planetary wave activity. The predictable period estimated by the RMSE during the undisturbed phase when the planetary wave has small amplitude is much larger than that during the disturbed phase. However, the predictable period estimated by the AC is comparable for both phases. Thus, the horizontal pattern of the stratospheric circulation is less predictable even though the forecast error is quite small (Figure 1).

Saito et al. (2016)

Saito, I., and K. Ishioka, 2016: On a quasi-invariant associated with the emergence of anisotropy in two-dimensional turbulence on a rotating sphere. J. Meteor. Soc. Japan, 94, 25-39.
https://doi.org/10.2151/jmsj.2016-002  Graphical Abstract

Highlights:

• A quasi-invariant for the vorticity equation on a rotating sphere is obtained by a minimization process.
• The distribution of the weighting coefficient for the quasi-invariant has airfoil-shaped contours (Fig. 1, solid curves), with which the anisotropic energy transfer that favors zonally elongated structures can be explained.
• Freely-evolving turbulence experiments confirm that the quasi-invariant is conserved well when the nonlinearity of the system is sufficiently weak.
• When the quasi-invariant is conserved well, energy is transferred in the wavenumber space apparently along the airfoil-shaped contours of the weighting coefficient for the quasi-invariant (Fig. 1).

Zhan et al. (2016)

Zhan, Y., G. Ren, and Y. Ren, 2016: Start and end dates of rainy season and their temporal change in recent decades over East Asia. J. Meteor. Soc. Japan, 94, 41-53.
https://doi.org/10.2151/jmsj.2016-003  Graphical Abstract

Highlights:

• Climatological feature and long-term change of start and end dates of rainy season over East Asia are examined. A standard of 4mm/day precipitation in a pentad (climatology) or consecutive pentads (climate change) is applied to define the rainy season.
• Start and end dates of rainy season in the region as a whole insignificantly advanced, and the duration insignificantly increased from 1951 to 2009.
• The rainy season began earlier in China but later in Korea and Japan, and withdrew earlier at latitudes north of 35°N and southwest China, but delayed in the Yangtze–Huaihe River Basins. The duration slightly reduced in Russian Far East and in northern and western China, and significantly decreased on the Korean Peninsula and southern Hokkaido Islands, but it obviously increased in the Yangtze–Huaihe River Basins.

Coronel et al. (2016)

Coronel, R., M. Sawada, and T. Iwasaki, 2016: Impacts of surface drag coefficient and vertical mixing schemes on the structure and energetics of Tropical Cyclone Megi (2010) during intensification. J. Meteor. Soc. Japan, 94, 55-73.
https://doi.org/10.2151/jmsj.2016-004  Graphical Abstract

Highlights:

• Using the MRI/JMA nonhydrostatic model with Deardorff (DF) PBL parameterization, tropical cyclone (TC) Megi (2010) is studied as it intensifies over the ocean.
• At 2-km resolution, the DF scheme simulates more accurate results with deeper central pressure, and shallower maximum winds and inflow layer than the Mellor-Yamada-Nakanishi-Niino scheme.
• Increasing the surface friction with surface drag yields a weaker small TC whereas enhancing the frictional eddy-stress with MYNN scheme simulates a weaker large TC.
• The impact of the friction-induced structural change on the energetics of TC Megi is dual: it enhances the dynamical energy conversion but also amplifies energy loss.

Gao et al. (2016)

Gao, Y., Y. Chen, L. Zhang, and T. Peng, 2016: Radar-rainfall estimation from S-band radar and its impact on the runoff simulation of a heavy rainfall event in the Huaihe River Basin. J. Meteor. Soc. Japan, 94, 75-89.
https://doi.org/10.2151/jmsj.2016-005  Graphical Abstract

Highlights:

• The main purpose of this study is to integrate a rainfall estimate by the China New Generation Weather Radar S-band radar (CINRAD-SB) into the Hydrologic Engineering Center’s Hydrologic Modeling System (HEC-HMS) and analyze the CINRAD-SB rainfall estimation and its impact on the runoff simulation of this type of rare flood event in a region with complex terrain.
• For the CINRAD-SB rainfall estimation four methods are considered: (1) Z=300R1.4 (Z: radar reflectivity, R: rainfall intensity); (2) a rainfall estimation error adjustment by using a Kalman Filter (KF); (3) Optimal Interpolation (OI); and (4) the Union method, which is composed of KF and OI. The relative bias values of the four methods vary with different rainfall intensity, those of the Union method vary the least among the four methods (Fig. 4).
• Runoff simulations based on radar-rainfall could reproduce similar overall patterns to the observed streamflow. The peak discharge contains obvious improvements – for instance, the skill score is 0.6 – in model runs with forcing that is provided by the Union method vs. rain gauge data (Fig. 8).

Patra et al. (2016)

Patra, P. K., T. Saeki, E. J. Dlugokencky, K. Ishijima, T. Umezawa, A. Ito, S. Aoki, S. Morimoto, E. A. Kort, A. Crotwell, K. Ravi Kumar, and T. Nakazawa, 2016: Regional methane emission estimation based on observed atmospheric concentrations (2002–2012). J. Meteor. Soc. Japan, 94, 91-113.
https://doi.org/10.2151/jmsj.2016-006  Graphical Abstract

Highlights:

• Methane (CH₄) participated prominently in global warming and air pollution chemistry over the past one century. However, anthropogenic emission inventories of CH₄ suffer from large uncertainties, due to the lack of country-specific sectorial emission factors, timing of new technology implementation and the underlying statistics, especially for the developing countries.
• We have developed a new inverse modeling system for estimating CH₄ emissions from 53 regions of global land for the period of 2002-2012, using the JAMSTEC’s atmospheric chemistry-transport model (ACTM) and observations of atmospheric CH₄ at 39 sites (Fig. 1).
• Our results suggest that CH₄ emission level and the rate of emission increase have very likely been overestimated for the East Asia region by the inventory estimates. The rate of CH₄ emission increase in the tropics is found to be in good agreement with that obtained from the inventory estimates, and can be attributed mainly to an increase in livestock population (Fig. 2).