No abstract

Nicotinamide N-methyltransferase (NNMT) was recently identified as one clear cell renal cell carcinoma (ccRCC)-associated gene by analyzing full-length complementary DNA-enriched libraries of ccRCC tissues. The aim of this study is to investigate the potential role of NNMT in cellular invasion. A strong NNMT expression is accompanied with a high invasive activity in ccRCC cell lines, and small interfering RNA-mediated NNMT knockdown effectively suppressed the invasive capacity of ccRCC cells, whereas NNMT overexpression markedly enhanced that of human embryonic kidney 293 (HEK293) cells. A positive correlation between the expression of NNMT and matrix metallopeptidase (MMP)-2 was found in ccRCC cell lines and clinical tissues. The treatment of blocking antibody or inhibitor specific to MMP-2 significantly suppressed NNMT-dependent cellular invasion in HEK293 cells. Furthermore, SP-1-binding region of MMP-2 promoter was found to be essential in NNMT-induced MMP-2 expression. The specific inhibitors of PI3K/Akt signaling markedly decreased the binding of SP1 to MMP-2 promoter as shown by chromatin immunoprecipitation assay. We also demonstrated that PI3K/Akt pathway plays a role in NNMT-dependent cellular invasion and MMP-2 activation. Moreover, short hairpin RNA-mediated knockdown of NNMT expression efficiently inhibited the growth and metastasis of ccRCC cells in non-obese diabetic severe combined immunodeficiency mice. Taken together, the present study suggests that NNMT has a crucial role in cellular invasion via activating PI3K/Akt/SP1/MMP-2 pathway in ccRCC.

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Typhoon Morakot struck Taiwan during 6-9 August 2009, and it produced the highest rainfall (approaching 3000 mm) and caused the worst damage in the past 50 yr. Typhoon-monsoon flow interactions with mesoscale convection, the water vapor supply by the monsoon flow, and the slow moving speed of the storm are the main reasons for the record-breaking precipitation. Analysis of the typhoon track reveals that the steering flow, although indeed slow, still exceeded the typhoon moving speed by approximately 5 km h~'(l km h~' = 0.28 m s~') during the postlandfall period on 8 August, when the rainfall was the heaviest. The CloudResolving Storm Simulator (CReSS) is used to study the dynamics of the slow storm motion toward the northnorthwest upon leaving Taiwan. The control simulations with 3-km grid size compare favorably with the observations, including the track, slow speed, asymmetric precipitation pattern, mesoscale convection, and rainfall distribution over Taiwan. Sensitivity tests with reduced moisture content reveal that not only did the model rainfall decrease but also the typhoon translation speed increased. Specifically, the simulations consistently show a discernible impact on storm motion by as much as 50%, as the storms with full moisture move slower(~5 km h~'). while those with limited moisture (s25%) move faster (-10 km h"'). Thus, in addition to a weak steering flow, the prolonged asymmetric precipitation in Typhoon Morakot also contributed to its very slow motion upon leaving Taiwan, and both lengthened the heavy-rainfall period and increased the total rainfall amount. The implications of a realistic representation of cloud microphysics from the standpoint of tropical cyclone track forecasts are also briefly discussed.

The present study investigates the characteristics of low-level jets (LLJs) (≥12.5 m s−1) below 600 hPa over northern Taiwan in the mei-yu season and their relationship to heavy rainfall events (≥50 mm in 24 h) through the use of 12-h sounding data, weather maps at 850 and 700 hPa, and hourly rainfall data at six surface stations during the period of May–June 1985–94. All LLJs are classified based on their height, appearance (single jet or double jet), and movement (migratory and nonmigratory). The frequency, vertical structure, and spatial and temporal distribution of LLJs relative to the onset of heavy precipitation are discussed. Results on the general characteristics of LLJs suggest that they occurred about 15% of the time in northern Taiwan, with a top speed below 40 m s−1. The level of maximum wind appeared mostly between 850 and 700 hPa, with highest frequency at 825–850 hPa. A single jet was observed more often (76%) than a double jet (24%), while in the latter case a barrier jet usually existed at 900–925 hPa as the lower branch. Migratory and nonmigratory LLJs each constituted about half of all cases, and there existed no apparent relationship between their appearance and movement. Migratory LLJs tended to be larger in size, stronger over a thicker layer, more persistent, and were much more closely linked to heavy rainfall than nonmigratory jets. They often formed over southern China between 20° and 30°N and moved toward Taiwan presumably along with the mei-yu frontal system. Before and near the onset of the more severe heavy rain events (≥100 mm in 24 h) in northern Taiwan, there was a 94% chance that an LLJ would be present over an adjacent region at 850 hPa, and 88% at 700 hPa, in agreement with earlier studies. Occurrence frequencies of LLJs for less severe events (50–100 mm in 24 h) were considerably lower, and the difference in accumulative rainfall amount was seemingly also affected by the morphology of the LLJs, including their strength, depth, elevation of maximum wind, persistence, proximity to northern Taiwan, source region of moisture, and their relative timing of arrival before rainfall. During the data period, about 40% of all migratory LLJs at 850 or 700 hPa passing over northern Taiwan were associated with heavy rainfall within the next 24 h. The figure, however, was much lower compared to earlier studies, and some possible reasons are offered to account for this deficit.

During the morning hours on 23 May 2002, a convective line associated with a mei-yu front brought heavy rainfall along the coast of central Taiwan under favorable synoptic conditions of warm air advection and large convective available potential energy (CAPE) of over 3000 m 2 s Ϫ2 . Doppler radar observations indicated that deep convection was organized into a linear shape with a northeast-southwest orientation along the front about 70 km offshore from Taiwan over the northern Taiwan Strait. The system then moved toward Taiwan at a slow speed of about 4 m s Ϫ1 . In the present study, the effects of Taiwan topography on this convective line and subsequent rainfall distribution were investigated through numerical modeling using the Nagoya University Cloud-Resolving Storm Simulator (CReSS) at a 2-km horizontal grid size. Experiments with different terrain heights of Taiwan, including full terrain (FTRN), half terrain (HTRN), and no terrain (NTRN), were performed. The control run using full-terrain and cold rain explicit microphysics realistically reproduced the evolution of the convective line and the associated weather with many fine details.Two low-level convergence zones were found to be crucial in the development of this convective line and the subsequent rainfall distribution over Taiwan. The first was along the mei-yu front and forced mainly by the front, but was terrain enhanced off the northwestern coast of Taiwan due to the blocking of air on the windward side of the Central Mountain Range (CMR). After formation, convective cells along this zone propagated southeastward and produced rainfall over the northwestern coast. As the front moved closer to Taiwan, a second arc-shaped convergence zone with a nearly north-south orientation along about 120°E formed ahead of the front between the prevailing flow and near-surface offshore flow induced by the blocking. This second zone was terrain induced, and convection initiated near its northern end was found to be responsible for the rainfall maximum observed near the coast of central Taiwan. Its intensity and position were highly sensitive to terrain height. In the HTRN run where the terrain was reduced by half, a weaker zone closer to the CMR (by about 50 km) was produced, and the rain fell mostly over the windward slope of the terrain instead of over the coastal plain. When the terrain was removed in the NTRN run, no such zone with the correct orientation formed. It was also found that the frontal movement near northern Taiwan was slightly delayed with the presence of terrain, and this affected the timing and distribution of local rainfall during the later stages of this event.

[1] Typhoon Fanapi (2010) traveled westward across the Central Mountain Range of Taiwan on 19 September and its rainfall shifted from a symmetric to an asymmetric pattern with convection mostly to the south and southeast. Meanwhile, the storm slowed down from 22 to 14 km h À1 for 12 h upon leaving Taiwan, and led to heavy rainfall (>800 mm) and serious flooding over the low-lying southwestern plains. Through simulation and sensitivity tests using the Cloud-Resolving Storm Simulator at 3 km grid size, this study shows that the sudden and temporary speed reduction was caused by the asymmetric latent heating (LH), not the environmental flow. Specifically, over a 9 h period, the model storm moved westward at 16 km h À1 in the control run, but increasingly faster and more toward the northwest when the moisture (and thus the LH effect and its asymmetry) is gradually reduced. Steering flow analysis and estimation using model results suggest an eastward motion vector of about 8 km h À1 , consistent with the observation, is produced by the asymmetric LH effect, when the effects from the vertical wind shear and beta-drift are both taken into account. This result is further supported by the diagnosis on storm motion based on potential vorticity tendency. Although important, such feedback to typhoon track from rainfall asymmetry that is induced by the blocking effect of topography have not been reported or studied.

The present study has used the Geostationary Meteorological Satellite (GMS) IR brightness temperature observations to investigate the regional and intraseasonal variability of east Asian warm-season cloud/precipitation episodes (in distance–time space) due to land–sea contrast and latitudinal effects. The data period was May–August 1998–2001, and harmonic analysis was employed as the major tool for analysis. The full domain of study (20°–40°N, 95°–145°E) was divided into northern and southern zones, and into eastern and western sectors, and statistics of episodes in each subregion were derived and compared. For latitudinal effects, episodes were found to be significantly larger in span and duration in northern (30°–40°N) than in southern (20°–30°N) zones. In the northern zone, the propagation characteristics were also stronger and remain evident even in midsummer, while episodes south of 30°N reversed in direction and traveled westward in July and August. For land–sea contrast, the May–August transition over land (western sector, 95°–120°E) was mainly characterized by an increase in diurnal activities, while that over ocean (eastern sector, 120°–145°E) was characterized by decreased overall activities instead. Over the land itself, significant regional variability also existed, with strongest diurnal signals over the eastern Tibetan Plateau near 100°E, and increased diurnal activities over mountain areas in southeastern China since June. Between the two bands, near 107°E, semidiurnal signals were relatively strong and became dominant in June. This double-peaked structure in the diurnal cycle resulted from overlying signals of convection propagating eastward off the plateau with those induced locally in late afternoon, and the phenomenon was more evident in May–June. Over the ocean, on the other hand, both diurnal and semidiurnal waves had small amplitudes, and the regional variability was much weaker. For intraseasonal transition, the number of large episodes was reduced from May through July, as was mean propagation speed. In August, however, some larger events started to reappear over east Asia.