DIFFERENCES AMONG DIFFERENT DATABASES IN THE NUMBER OF TROPICAL CYCLONES FORMING OVER THE WESTERN NORTH PACIFIC

As shown in comparisons of the characteristics of inter-annual and inter-decadal variability and periodical changes in the number of tropical cyclones forming over the western North Pacific by three major forecast centers, i.e. China Meteorological Administration (CMA), Regional Specialized Meteorological Center of Tokyo (JMA) and Joint Typhoon Warning Center (JTWC) of Guam, there are the following important points. (1) Climatology of tropical cyclone (TC) or typhoon (TC on the intensity of TS or stronger) shows some difference in tropical cyclone frequency among the centers, which is more notable with TC than with typhoon. Both of them are more at the database of CMA than at those of the other two centers. (2) The difference is too significant to ignore in the inter-annual variability of tropical cyclone frequency between CMA and JTWC, which mainly results from the obvious difference in the inter-annual variability of the number of generated tropical depression (TD) between the two databases. The difference is small in the inter-annual variability of TS formations among all the three databases, and consistence is good between JMA and CMA or JTWC. (3) Though differences are not significant in the periodical variation of TC formations between CMA and JTWC, they are markedly apart in the inter-decadal variability, which is mainly shown by an anti-phase during the 1990s. (4) Non-homogeneity may exist around the late stage of the 1960s in the data of tropical cyclone frequency.

Analysis method on shoot precision of weapon in small-sample case

Because of limits of cost, in general, the test data of weapons are shortness. It is always an important topic that to gain scientific results of weapon performance analyses in small-sample case. Based on the analysis of distribution function characteristics and grey mathematics, a weighting grey method in small-sample case is presented. According to the analysis of test data of a weapon, it is proved that the method is a good method to deal with data in the small-sample case and has a high value in the analysis of weapon performance.

POSSIBLE INFLUENCE OF FEBRUARY-APRIL ARCTIC OSCILLATION ON THE ITCZ ACTIVITY OF WESTERN-CENTRAL PACIFIC

The daily patterns and activity of Intertropical Convergence Zone(ITCZ) in the Western-Central Pacific Ocean are analyzed using NOAA interpolated Outgoing Longwave Radiation dataset during the period from 1979 to 2008, and the relationships between ITCZ patterns and Arctic Oscillation(AO) is investigated in this paper. In accordance with the central activity region the daily ITCZ can be divided into six patterns—north, south, equator, double, full and weak pattern, respectively. The statistic result shows that the north(accounting for 30.98% of the total observations), south(31.11%) and weak(24.05%) ITCZ patterns are the most active daily patterns within a 30-year period, while the other three ITCZ patterns occur infrequently. Results show that the February-April AO index has a significant positive(negative) correlation with the frequency of the north(weak) ITCZ pattern from March-May to August-October, with the strongest correlation in April-June(March-May). At the same time, the lower tropospheric atmosphere circulation(850-hPa wind field) and SST anomalies corresponding to the AO change significantly in the tropical Pacific. When AO is in the positive phase, there is an anomalous westerly from the equator to 15°N and warmer SST in the critical north ITCZ active region, while there is an anomalous easterly and insignificant change of SST from the equator to 15°S. The wind and SST anomalies share the same characteristics of the equatorial asymmetry and thus enlarge the gradient between the south and north of equator, which would help reinforce convection in the north of equator and result in more frequent occurrence of the northern type of ITCZ.