Masanori Niwano

Seasonal and QBO variations of ascent rate in the tropical lower stratosphere as inferred from UARS HALOE trace gas data

� 0.2 mm s � 1 in the 20–60 hPa layer. The latitudinal structure is characterized by an early appearance of a subtropical summer maximum of the ascent rate and by double peaks at 10–15� N and S during the northern winter season. The QBO component of the ascent rate shows tropically confined anomalies with a rapid downward propagation, but mass attenuation anomalies estimated from the ascent rate show a much slower downward propagation. The descent anomalies exhibit a well-structured and equatorially symmetric variation, while the ascent anomalies have a tendency to propagate latitudinally. This might be connected with the phase dependency of the QBO acceleration. An examination of the phase and amplitude of the ascent rate and temperature for both the seasonal and QBO components emphasizes that the radiative damping timescale is considerably long (40–100 days) below 40 hPa. INDEX TERMS: 0341 Atmospheric Composition and Structure: Middle atmosphere—constituent transport and chemistry (3334); 3334 Meteorology and Atmospheric Dynamics: Middle atmosphere dynamics (0341, 0342); 3319 Meteorology and Atmospheric Dynamics: General circulation; KEYWORDS: mean meridional circulation, transport, water vapor

Quasi‐biennial oscillation in vertical velocity inferred from trace gas data in the equatorial lower stratosphere

Vertical velocity variations associated with the quasi-biennial oscillation (QBO) in the equatorial lower stratosphere are investigated with the Halogen Occultation Experiment (HALOE) data from 1993 to 1998. The vertical velocity is inferred from ascent rates of an annual cycle in total water ([H2O] + 2[CH4]) profiles around the 20–60 hPa layer over the equator. The zonally averaged ascent rates of total water anomalies exhibit QBO-related variations with anomalies of 0.10–0.15 mm s−1 between 20 and 40 hPa at the equator, whereas there scarcely exists an annual cycle in the ascent rates. The QBO variation of the ascent rates shows that its positive anomalies precede negative anomalies of temperature and ozone variations by about 2–3 months at the equator and 30–60 hPa. This phase relationship is in conflict with former results from several two-dimensional model studies, which have reported that vertical velocity variations are almost out of phase with temperature anomalies preceding ozone anomalies by a few months. It is supposed that these differences could be caused by the observed large tendency of temperature anomalies, which is related to the observed rapid acceleration of the QBO westerly. An estimate of vertical advection of zonal momentum expected from the ascent rates suggests that the asymmetric acceleration of the zonal wind QBO can be explained by the QBO-induced vertical velocity being asymmetric between the easterly and the westerly shear zones.

Chemical Modelling with CHASER and WRF/Chem in Japan

In this paper results of studies with WRF/Chem and CHASER models are presented. The CHemical Atmospheric general circulation model for Study of Atmospheric Environment and Radiative forcing (CHASER) is a global chemical transport model (cf. Sudo et al. J Geophys Res 107(D21):4339, 2002a; Sudo et al. J Geophys Res 107(D21), 4586, 2002b; Takigawa et al., J Geophys Res 110, 2005). The gaseous and aerosol chemistry module is implemented in the CHASER in an on-line mode. CHASER is based on CCSR/FRCGC/NIES AGCM 5.7b, and the meteorology and radiation can be simulated in CHASER itself. The radiative feedback through the distribution of chemical species is taken into account. Daily forecasts have been available on internet since 1 January 2002. This forecasting system was developed for the use of daily flight planning for the Pacific Exploration of Asian Continental Emission (PEACE)-A (January 2002) and PEACE-B (April–May 2002) campaigns. A regional-scale chemical weather forecasting system based on WRF/Chem has been also developed. The lateral boundary for chemical species is taken from the 3-hourly output of CHASER. The modelled surface ozone was compared with the ground-based observations.

Development of a Quasi-Real-Time Forecasting System over Tokyo

We present an evaluation of the distribution of ozone over Kanto region, calculated by using a one-way nested global/regional air quality forecasting (AQF) system. This AQF system consists of the global chemistry-transport model (CTM) part and the regional CTM part. The global CTM part is based on CHASER, and the regional CTM part is based on WRF/Chem. An experimental phase of this model system began operation in July 2006 and has been providing 15-hour forecasts of the distribution of ozone concentrations over Kanto region four times in a day. The time-evolution and horizontal distribution of chemical species calculated by this AQF system were compared to ground-based observations.

A Regional Air Quality Model over the Kanto Region of Japan: The Effect of the Physics Parameterization on the Meteorological and Chemical Fields

The effects of physics parameterization on meteorological and chemical fields were examined over the Kanto region of Japan using an air quality (AQ) model, which consists of two chemistry transport models: the global model CHASER and the regional model WRF/Chem. For hindcast experiments without a chemical module for June-July in 2005 and 2006, two non-local planetary boundary layer (PBL) schemes (Yonsei University YSU and NCEP GFS) showed a deeper PBL height and a stronger sea-breeze related with warmer surface temperature than for the observation and the local PBL scheme (Mellor-Yamada level 2.5). Two experiments with a chemical module for July–August in 2005 clarified that NCEP GFS scheme transported O3 plumes to higher altitudes above 2 km and also produced a higher concentration near the surface than for Mellor-Yamada scheme.