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Zhang F.,Chinese Academy of Meteorological Sciences | Zhang F.,Shanghai Typhoon Institute of China Meteorological Administration | Shen Z.,Shanghai Climate Center | Li J.,University of Victoria | And 2 more authors.
Journal of the Atmospheric Sciences | Year: 2013

Although single-layer solutions have been obtained for the δ-four-stream discrete ordinates method (DOM) in radiative transfer, a four-stream doubling-adding method (4DA) is lacking, which enables us to calculate the radiative transfer through a vertically inhomogeneous atmosphere with multiple layers. In this work, based on the Chandrasekhar invariance principle, an analytical method of δ-4DA is proposed. When applying δ-4DA to an idealized medium with specified optical properties, the reflection, transmission, and absorption are the same if the medium is treated as either a single layer or dividing it into multiple layers. This indicates that δ-4DA is able to solve the multilayer connection properly in a radiative transfer process. In addition, the δ-4DA method has been systematically compared with the δ-two-stream doubling-adding method (δ-2DA) in the solar spectrum. For a realistic atmospheric profile with gaseous transmission considered, it is found that the accuracy of δ-4DA is superior to that of δ-2DA in most of cases, especially for the cloudy sky. The relative errors of δ-4DA are generally less than 1% in both the heating rate and flux, while the relative errors of δ-2DA can be as high as 6%. © 2013 American Meteorological Society.


Lei X.-T.,Shanghai Typhoon Institute and Laboratory of Typhoon Forecast Technique | Tang J.,Shanghai Typhoon Institute and Laboratory of Typhoon Forecast Technique | Xu X.-L.,Shanghai Typhoon Institute and Laboratory of Typhoon Forecast Technique | Zhan R.-F.,Shanghai Typhoon Institute and Laboratory of Typhoon Forecast Technique | And 3 more authors.
Journal of Tropical Meteorology | Year: 2012

Intensity variation of tropical cyclones (TC s), especially that of coastal or landfalling TC s, is of great concern in current research. Most of the research papers, however, focus on intensification processes of TC s; only a few discuss decay processes in the lifetime of a TC. In the daily weather operation related to TC s, it is challenging when a TC weakens and/or disappears suddenly, because it brings more difficulties than the forecast of intensifying TC s does. Overestimation of a decaying landfalling TC would lead to over-preparation of defensive measures and result in "crying wolf" mentality with adverse effects. This study summarized physical mechanisms that dominate the decaying process of TC s and listed several possible dynamical factors: Reduced level of air temperature, too large or too small speed, contraction of TC size amplification of TC's core, and lightning number in a TC.


Yu H.,Shanghai Typhoon Institute and Laboratory of Typhoon Forecast Technique | Lu Y.,Shanghai Typhoon Institute and Laboratory of Typhoon Forecast Technique | Lu Y.,Chinese Academy of Meteorological Sciences | Chen P.-Y.,Shanghai Typhoon Institute and Laboratory of Typhoon Forecast Technique | Zhou W.-C.,Wuxi Environmental science and Engineering Research Center
Journal of Tropical Meteorology | Year: 2012

Analyzed in this paper are the 20-yr (1991-2010) tropical cyclone (TC) intensity from three forecast centers in the Western North Pacific, i.e. China Meteorological Administration (CMA), Japan Meteorological Agency (JMA), and Joint Typhoon Warning Center (JTWC) of the United States. Results show that there is more or less discrepancy in the intensity change of a TC among different datasets. The maximum discrepancy reaches 22 hPa/6h (42 hPa/6h, 33 hPa/6h) between CMA and JMA (CMA and JTWC, JMA and JTWC). Special attention is paid to the records for abrupt intensity change, which is currently a difficult issue for forecasters globally. It is found that an abrupt intensity change process recorded by one dataset can have, in some extreme cases, intensity change in another dataset varying from 0 to ≥ 10 hPa/6h with the same sign or the opposite sign. In a total of 2511 cases experiencing rapid intensity change, only 14% have consensus among all the three datasets and 25 % have agreement between two of the three datasets. In spite of such a significant uncertainty, the three datasets agree on the general statistical characteristics of abrupt intensity change, including regional and seasonal distribution, the relationship with initial intensity and TC moving speed, and persistence features. Notable disagreement is on very strong systems (SuperTY) and TC s moving very fast.


Shu S.-J.,Nanjing University | Xu Y.,Nanjing University | Song J.-J.,Nanjing University | Yu Z.-F.,Shanghai Typhoon Institute and Laboratory of Typhoon Forecast Technique
Journal of Tropical Meteorology | Year: 2012

In order to provide an operational reference for tropical cyclone precipitation forecast, this study investigates the spatial distributions of precipitation associated with landfalling tropical cyclones (TCs) affecting China using Geostationary Meteorological Satellite 5 (GMS5)-TBB dataset. All named TCs formed over the western North Pacific that made direct landfall over China during the period 2001-2009 are included in this study. Based on the GMS5-TBB data, this paper reveals that in general there are four types of distribution of precipitation related to landfalling TCs affecting China. (a) the South-West Type in which there is a precipitation maximum to the southwestern quadrant of TC; (b) the Symmetrical South Type in which the rainfall is more pronounced to the south side of TC in the inner core while there is a symmetrical rainfall distribution in the outer band region; (c) the South Type, in which the rainfall maxima is more pronounced to the south of TC; and (d) the North Type, in which the rainfall maxima is more pronounced to the north of TC. Analyses of the relationship between precipitation distributions and intensity of landfalling TCs show that for intensifying TCs, both the maximum and the coverage area of the precipitation in TCs increase with the increase of TC intensity over northern Jiangsu province and southern Taiwan Strait, while decreasing over Beibu Gulf and the sea area of Changjiang River estuary. For all TCs, the center of the torrential rain in TC shifts toward the TC center as the intensity of TC increases. This finding is consistent with many previous studies. The possible influences of storm motion and vertical wind shear on the observed precipitation asymmetries are also examined. Results show that the environmental vertical wind shear is an important factor contributing to the large downshear rainfall asymmetry, especially when a TC makes landfall on the south and east China coasts. These results are also consistent with previous observational and numerical studies.


Wang Q.,Ocean University of China | Wang Q.,Shanghai Typhoon Institute and Laboratory of Typhoon Forecast Technique | Li Q.,Shanghai Typhoon Institute and Laboratory of Typhoon Forecast Technique | Fu G.,Ocean University of China
Weather and Forecasting | Year: 2012

Four methods for determining the extratropical transition (ET) onset and completion times of Typhoons Mindulle (2004) and Yagi (2006) were compared using four numerically analyzed datasets. The open-wave and scalar frontogenesis parameter methods failed to smoothly and consistently determine the ET completion from the four data sources, because some dependent factors associated with these two methods significantly impacted the results. Although the cyclone phase space technique succeeded in determining the ET onset and completion times, the ET onset and completion times of Yagi identified by this method exhibited a large distinction across the datasets, agreeing with prior studies. The isentropic potential vorticity method was also able to identify the ET onset times of both Mindulle and Yagi using all the datasets, whereas theET onset time of Yagi determined by such a method differed markedly from that by the cyclone phase space technique, which may create forecast uncertainty. © 2012 American Meteorological Society.


Li Q.,Chinese Academy of Meteorological Sciences | Li Q.,Shanghai Typhoon Institute and Laboratory of Typhoon Forecast Technique | Wang Y.,University of Hawaii at Manoa | Duan Y.,Chinese Academy of Meteorological Sciences
Journal of the Atmospheric Sciences | Year: 2014

The effects of diabatic heating and cooling in the rapid filamentation zone (RFZ), within which inner rainbands are often active, on tropical cyclone (TC) structure and intensity are investigated based on idealized numerical experiments using a cloud-resolving TC model (TCM4). The results show that removal of heating (cooling) in the RFZ would reduce (increase) the TC intensity. Diabatic heating in the RFZ plays an important role in increasing the inner-core size whereas diabatic cooling tends to limit the inner-core size increase or even reduce the inner-core size of a TC. Removal of both diabatic heating and cooling in the RFZ greatly suppresses the activity of inner rainbands but leads to the quasi-periodic development of a convective ring immediately outside of the inner core. A similar convective ring also develops in an experiment with the removal of diabatic heating only in the RFZ. With diabatic cooling removed only in the RFZ, an annularhurricane-like structure arises with the outer rainbands largely suppressed. © 2014 American Meteorological Society.


Yang Q.-Z.,Shanghai Typhoon Institute and Laboratory of Typhoon Forecast Technique | Xu M.,Shanghai Typhoon Institute and Laboratory of Typhoon Forecast Technique
Journal of Tropical Meteorology | Year: 2010

Hazard factors, hazard-bear1ing objects, disaster-developing environment, and disaster-preventing capability play key roles in the formation of Tropical Cyclone (TC) disasters. Of all of these, the most important is the intensity of hazard factors (risk sources). In this study, this intensity is uniformly defined by the probability of hazard factors; then a relationship is established between disaster risk intensity and hazard factors. The exceedance probability of various hazard factors, including frequency and timing, scope of wind and rain, and maximum wind and rain of impacting TC cases, are calculated using data from TCs that impacted Shanghai from 1959-2006. The relationship between disaster situation and risk probability of hazard factors is analyzed, and the indices and model of TC disaster assessment are established based on the results. The process maximum wind speed and maximum daily precipitation are very important in TC-related disaster formation in Shanghai. The results of disaster indices coordinate with the results of the assessment model, and both can show the extent of probability of a TC disaster. Tests using TC data in 2007 and 2008 show that disasters caused by TC Krosa (0716) would be more serious than those by TC Wipha (0713), and that TC Fung Wong (0808) would have a weak impact. Real-life situations validate these results.

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