Tao L.,Nanjing University of Information Science and Technology |
Wu L.,Nanjing University of Information Science and Technology |
Wang Y.,University of Hawaii at Manoa |
Yang J.,Key Laboratory of Meteorological Disaster Preventing and Reducing in Ningxia
Journal of the Meteorological Society of Japan | Year: 2012
In this study, we have investigated contributions of tropical Indian Ocean (IO) sea surface temperature (SST) warming and El Nĩno-Southern Oscillation (ENSO) to the interannual variability of tropical cyclone (TC) genesis frequency over the western North Pacific (WNP) between 1948 and 2010 and the involved physical mechanisms. Both ENSO and tropical IO Basin Mode (IOBM) warming are found to play important roles in modulating the WNP TC genesis frequency, but their effects are significantly different. The time series of seasonal empirical orthogonal function of tropical IO and tropical Pacific SST with trend and multi decadal variability removed are defined as the IOBM index and ENSO index, respectively. The results show that the IO warming year is usually the El Nĩno decaying year. The number of total TCs, especially weak TCs, decreases during the tropical IO warming year when an anomalous anticyclonic circulation is observed over the tropical Northwest Pacific off the equator. On the other hand, the number of intense TCs increases in the El Nĩno developing year because of the eastward shifts of both the western Pacific monsoon trough and the cyclonic shear of the equatorial westerlies, and thus the eastward shift of the main TC genesis region. It is also found that the relationship between ENSO and the frequency of intense TCs has a decadal variation. During 1968-1987, the number of intense TCs was not related to ENSO with a correlation coefficient of only 0.19, while the correlation coefficient is 0.63 and 0.73 during 1948-1967 and 1988-2007, respectively. The extent to which the WNP anomalous anticyclone is forced by IO warming is investigated by using the global climate model (European Centre Hamburg Model, ECHAM) with imposed SST anomalies over the tropical IO. The results suggest that the WNP anomalous anticyclone that develops from June to September results mainly from the northward shift of the tropical IO warming from boreal spring to boreal summer. © 2012, Meteorological Society of Japan.
Hu H.,Nanjing University |
Hong X.,Nanjing University |
Hong X.,CAS Qingdao Institute of Oceanology |
Hong X.,University of Chinese Academy of Sciences |
And 5 more authors.
Chinese Journal of Oceanology and Limnology | Year: 2013
This paper attempts to analyze in detail the remote influence of the Indian Ocean Basin warming on the Northwest Pacific (NWP) during the year of decaying El Niño. Observation data and the Fast Ocean-Atmosphere coupled Model 1.5 were used to investigate the triggering conditions under which the remote influence is formed between the positive sea surface temperature (SST) anomaly in the North Indian Ocean and the Anomalous Northwest Pacific anticyclone (ANWPA). Our research show that it is only when there is a contributory background wind field over the Indian Ocean, i.e., when the Indian Summer Monsoon (ISM) reaches its peak, that the warmer SST anomaly in the North Indian Ocean incites significant easterly wind anomalies in the lower atmosphere of the Indo-West tropical Pacific. This then produces the remote influence on the ANWPA. Therefore, the SST anomaly in the North Indian Ocean might interfere with the prediction of the East Asia Summer Monsoon in the year of decaying El Niño. Both the sustaining effect of local negative SST anomalies in the NWP, and the remote effect of positive SST anomalies in the North Indian Ocean on the ANWPA, should be considered in further research. © 2013 Chinese Society for Oceanology and Limnology, Science Press and Springer-Verlag Berlin Heidelberg.
Zhang Z.,Key Laboratory of Meteorological Disaster Preventing and Reducing in Ningxia |
Chen Y.,Key Laboratory of Meteorological Disaster Preventing and Reducing in Ningxia |
Zhou H.,Key Laboratory of Meteorological Disaster Preventing and Reducing in Ningxia
Journal of Natural Disasters | Year: 2014
Based on the daily maximum temperature data of 81 stations in summer half year in Hetao and its vicinity during 1961 to 2010, this paper calculated the threshold value of extreme high temperature for different stations, and analyzed their spatiotemporal distribution and change trend. The results show that, the threshold value is high in southeast and northwest and low in southwest of Hetao. The consistent and contrary anomaly distribution was the main spatial model of the extreme high temperature frequency. The spatial model in Hetao and its vicinity can be divided into three areas; north of Hetao area, southeast and southwest of the Hetao area. The extreme high temperature frequency displays remarkable increasing tendency in north and southwest of the Hetao area, and displays obvious decreasing tendency in southeast of the Hetao area. The inter-Annual changes of the extreme high temperature frequency in north and southwest of Hetao areas are close. The extreme high temperature frequency is on the lower side during 1961 - 1990, and on the higher side during 1991 -2010, and it is contrary in southeast of the Hetao area. The frequency has an obvious fluctuating period of 10 - 14 years in north and southwest of the Hetao area. The extreme high temperature frequency in summer half year is positively correlated with the average temperature in same period.