Analysis of the ozone reduction event over the southern tip of South America in November 2009

Akiyoshi, Hideharu*; Kadowaki, Masanao; Nakamura, Haruna*; Sugita, Takafumi*; Hirooka, Toshihiko*; Harada, Yayoi*; Mizuno, Akira*

Journal of Geophysical Research; Atmospheres, 123(22), p.12523 - 12542, 2018/11

AA2018-0443.pdf:12.61MB

https://doi.org/10.1029/2017JD028096

A reduction of the total ozone over the southern tip of South America lasting 3 weeks occurred in November 2009. Analyses of the ERA-Interim reanalysis data and the total ozone observed by the Ozone Monitoring Instrument indicate that the total ozone reduction event was caused by a migration of the polar vortex toward the South American continent at the time of the vortex breakup. The vortex migration is associated with an enhanced wave flux from the troposphere at 120-150W and 50-60S to the west of the South American continent to the stratosphere over the southern part of the continent, which led to a large negative geopotential height anomaly in the lower stratosphere. In November, a blocking event was diagnosed from the 500-hPa geopotential height over the west of the South American continent. These results suggest a relation between the long-lasting reduction of the total ozone over the southern tip of South America and the blocking phenomenon in the troposphere of the Southern Hemisphere through wave propagation from the blocking region in 2009. Analysis of the total ozone anomaly for 50-60S and 65-75W over the southern tip of South America in November for 1979-2015 indicates that the negative ozone anomaly in November 2009 was one of the largest anomalies in this 37-year period and was associated with the large negative geopotential height anomaly in the lower stratosphere. Analyses of dynamical fields were also conducted for other years with large geopotential height anomalies.

Magnetic property of neptunyl (+2) complex NpO(CHO)(CHN)

Nakamura, Akio; Nakada, Masami; Nakamoto, Tadahiro*; Kitazawa, Takafumi*; Takeda, Masuo*

Journal of Magnetism and Magnetic Materials, 310(2, Part2), p.1447 - 1449, 2007/03

Magnetic property of a nitrogen (N)-coordinated neptunyl (+2) (Np(VI)) complex. 1 NpO(acac)(py) (acac=CHO, py=CHN) was studied by DC magnetization (M) measurements. While previous Np Mssbauer data of 1 exhibited para magnetic-relaxation spectra similar to other oxo-neptunyls (+1,+2), the DC- data have revealed many strikingly different features of 1 from the latter: first, its reciprocal susceptibility () vs. (K) plots showed a peculiar strongly field ()-dependent nonparamagnetic behavior, which suggests the presence of small ferromagnetic component with 300 K. In addition, its low-temperature isothermal exhibited anomalous relaxation behavior involving initial over-responsive change and subs equent drift back to its "equilibrium" value (). Moreover, such showed strong perturbation effect from the SQUID- measurement itself. Such novel magnetic features suggest the presence of a largely metastable fluctuating magnetic (spin plus orbital) state in 1 as a collective body of individual Ising-type neptunyl (O=Np=O) molecular magnets.