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Impact of Background Dynamic and Thermodynamic States on Distinctive Annual Cycle of Near-Equatorial Tropical Cyclogenesis over the Western North Pacific

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Journal of Meteorological Research 2020年第4期34卷 822-835页

作者： Liyuan DENG tim LI Key Laboratory of Meteorological Disaster Ministry of Education/Joint International Research Laboratory of Climate and Environmental Change/Collaborative Innovation Center on Forecast and Evaluation of Meteorological DisastersNanjing University of Information Science&TechnologyNanjing 210044China International Pacific Research Center and Department of Atmospheric Sciences School of Ocean and Earth Science and TechnologyUniversity of HawaiiHonoluluHI 96822USA

In a sharp contrast to tropical cyclone(TC) genesis over the main development region of the western North Pacific(WNP), near-equatorial(0°-5°N) TCs exhibit a distinctive annual cycle, peaking in boreal winter and being inactive in boreal summer. The relative roles of dynamic and thermodynamic background states on near-equatorial TCs formation were investigated based on the observational diagnosis of the genesis potential index(GPI) and high-resolution model simulations. It is found that the background vorticity makes a major contribution to the distinctive annual cycle, while mean temperature and specific humidity fields are not critical. Numerical simulations further indicate that seasonal mean cyclonic vorticity in boreal winter has three effects on TC genesis near the equator. First, the environmental cyclonic vorticity interacts with TC vortex to promote a mid-level outflow, which strengthens boundary layer friction induced ascending motion and thus condensational heating. Second, it produces an equivalent Coriolis effect(via enhanced absolute vorticity), which strengthens positive feedback between primary and secondary circulation. Third, it helps to merge small-scale vortical hot towers(VHTs) into a mesoscale core through vorticity segregation process. However, background vorticity in boreal summer has an opposite effect on TC development near the equator.

关键词： near-equatorial tropical cyclone(TC) equivalent Coriolis effect vorticity segregation

An Empirical Model of Tropical Cyclone Intensity Forecast in the Western North Pacific

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Journal of Meteorological Research 2022年第5期36卷 691-702页

作者： Chen MA tim LI Jiangsu Meteorological Observatory Jiangsu Meteorological BureauNanjing 210019China Key Laboratory of Meteorological Disaster Ministry of Education(KLME)/Joint International Research Laboratory of Climate and Environmental Change(ILCEC)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD)NanjingUniversityof Information Science&TechnologyNanjing210044China International Pacific Research Center and Department of Atmospheric Sciences School of Ocean and Earth Science and TechnologyUniversityofHawaiiHI96822USA Key Laboratory of Transportation Meteorology China Meteorological AdministrationNanjing 210019China

The relative impact of environmental parameters on tropical cyclone(TC) intensification rate(IR) was investigated through a box difference index(BDI) method, using TC best track data from Joint Typhoon Warning Center and environmental fields from the NCEP final analysis data over the western North Pacific(WNP) during 2000–*** are total 6307 TC samples with a 6-h interval, of which about 14% belong to rapid intensification(RI) category. The analysis shows that RI occurs more frequently with higher environmental sea surface temperature, higher oceanic heat content, and lower upper-tropospheric temperature. A moderate easterly shear is more favorable for TC intensification. TC intensification happens mostly equatorward of 20°N while TC weakening happens mostly when TCs are located in the northwest of the basin. Mid-tropospheric relative humidity and vertical velocity are good indicators separating the intensification and non-intensification groups. A statistical model for TC intensity prediction was constructed based on six environmental predictors, with or without initial TC intensity. Both models are skillful based on Brier skill score(BSS) relative to climatology and in comparison with other statistical models, for both a training period(2000–2018) and an independent forecast period(2019–2020).

关键词： tropical cyclone rapid intensification prediction model

Increasing Trend of Summertime Synoptic Wave Train Activity over the Western North Pacific since 1950

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Journal of Meteorological Research 2020年第5期34卷 1013-1024页

作者： Xinyi ZHOU tim LI Key Laboratory of Meteorological Disaster Ministry of Education(KLME)/Joint International Research Laboratory of Climate and Environmental Change(ILCEC)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD)Nanjing University of Information Science&TechnologyNanjing 210044China International Pacific Research Center and Department of Atmospheric Sciences School of Ocean and Earth Science and TechnologyUniversity of HawaiiHonoluluHI 96822USA

The change of summertime synoptic-scale wave train(SWT) activity over the western North Pacific(WNP) since1950 was investigated based on the NCEP–NCAR reanalysis data. It is found that the intensity of SWT has a rising trend, while its structure and phase propagation characteristics remain unchanged. Environmental factors responsible for the rising trend are investigated. By separating the whole period into three warming phases(P1: 1950–1958, P2:1978–1986, and P3: 2006–2014), we found that even though the vertical velocity shows a rising trend, the background low-level vorticity over the monsoon trough region increases from P1 to P2 but decreases from P2 to P3, and so is the low-level barotropic energy conversion(CK). Thus, just the environmental dynamic factor could not explain the continuous rising SWT trend. On the other hand, thermodynamic factor, such as the sea surface temperature(SST), moisture, and atmospheric instability, shows a clear step-by-step increasing trend. A non-dimensional synoptic activity index(SAI) that combines the dynamic and thermodynamic factors is then proposed. This index well captures the observed long-term trend of the SWT intensity.

关键词： global warming synoptic wave train barotropic energy conversion(CK) atmospheric instability parameter synoptic activity index(SAI)

Sensitivity of the Size of a TC to Sea Surface Temperatures in Its Outer Region

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Journal of Meteorological Research 2023年第6期37卷 829-840页

作者： Mingyu BI tim LI Key Laboratory of Meteorological Disaster Ministry of Education(KLME)/Joint International Research Laboratory of Climate and Environmental Change(ILCEC)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD)Nanjing University of Information Science&TechnologyNanjing210044China Key Laboratory for Typhoon Monitoring&Forecasting of Zhejiang Province Wenzhou325000China International Pacific Research Center and Department of Atmospheric Sciences University of Hawaii at ManoaHonoluluHawaii96822USA

We investigated the sensitivity of the size of a tropical cyclone(TC) to warming or cooling sea surface temperatures(SST) in its outer region by simulating the SST beyond a radius of 200 km from the TC *** experiments showed that an increased SST outside the core region of the TC had a negative effect on its *** in the outer region contributed to the local enhancement of the latent heat flux from sea surface,which promoted the development of small-scale convection and warmed the lower and *** warming altered the local pressure gradient force in the upper and lower troposphere in such a way that it weakened the secondary circulation of the TC and led to suppression of the spiral rainbands outside the *** analysis showed that the outward-propagating rainband structure favored an increase in the size of the *** diabatic heat released by the rainbands induced an inflow at lower levels,facilitating expansion of the *** greater the distance of the rainbands from the center of the TC,given the same amplitude of diabatic heating,the stronger the forced inflow,resulting in a faster increase in the size of the TC.

关键词： tropical cyclones(TCs) size rainbands sea surface temperature(SST)

Physical Processes Responsible for the Interannual Variability of Sea Ice Concentration in Arctic in Boreal Autumn since 1979

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Journal of Meteorological Research 2017年第3期31卷 468-475页

作者： Lei ZHANG tim LI Climate Dynamics Research Center and Earth System Modeling Center International Laboratory on Climate and Environment ChangeNanjing University of Information Science & Technology Department of Atmospheric Sciences University of Hawaii

Arctic sea ice concentration （ASIC） in boreal autumn exhibits prominent interannual variability since 1979. The physical mechanism responsible for the year-to-year variation of ASIC is investigated through observational data analyses and idealized numerical modeling. It is found that the ASIC interannual variability is closely associated with the anomalous meridional circulations over the Northern Hemisphere, which is further linked with the tropical sea surface temperature （SST） forcing. A tropics-wide SST cooling anomaly leads to an enhanced meridional SST gradi- ent to the north of the equator in boreal summer, generating strengthened and northward shifting Hadley circulation over the Northern Hemisphere. Consequently, the meridional circulations are enhanced and pushed poleward, lead- ing to an enhanced descending motion at the North Pole, surrounded by an ascending motion anomaly; the surface outflow turns into easterly anomalies, opposing the mean-state winds. As a result, positive cloudiness and weakened surface wind speed emerge, which reduce ASIC through changes in the surface latent heat flux and the downward longwave radiation.

关键词： Arctic sea ice variability interannual variability tropical forcing meridional circulations

An Improved Method for Defining Short-Term Climate Anomalies

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Journal of Meteorological Research 2021年第6期35卷 1012-1022页

作者： Xuan CHEN tim LI Key Laboratory of Meteorological Disaster Ministry of Education(KLME)/Joint International Research Laboratory of Climate and Environment Change(ILCEC)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD)Nanjing University of Information Science&TechnologyNanjing 210044China International Pacific Research Center and Department of Atmospheric Sciences School of Ocean and Earth Science and TechnologyUniversity of Hawaii atManoaHonoluluHI 96822USA

A conventional method to define short-term climate anomalies for atmospheric and oceanic variables,recommended by the World Meteorological Organization(WMO),is the departure from a 30-yr climatological mean in the preceding three *** a method,however,introduces spurious errors such as sudden jumps and artificial trends.A new method,named a trend correctional method,is introduced to eliminate the *** demonstrate the capability of this new method,we examine a set of idealized cases first by superposing a"true"interannual or interdecadal signal onto a linear or a nonlinear *** to the conventional method,the trend correctional method is able to retain,to a large extent,the"true"anomaly ***,we examined real-time *** anomaly time series derived based on the trend correctional method show a better agreement with the observed anomaly *** rootmean-square error is greatly improved,comparing to that calculated based on the conventional ***,the results from both the idealized and real cases demonstrate that the new method has a clear advantage to the conventional method in deriving true climate anomalies,in particular under the ongoing global warming circumstance.

关键词： long-term trend climate anomaly definition trend correctional method

Conservation and behavior of Africa＇s ＂Big Five＂

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Current Zoology 2014年第4期60卷 486-499页

作者： tim CARO Jason RIGGIO Department of Wildlife Fish and Conservation Biology University of California Davis CA 95616 USA

We examine the conservation status of Africa＇s ＂Big Five＂： lion, leopard, buffalo, black and white rhinoceros and elephant, and the role of behavioral knowledge in their conservation. Efforts to conserve these flagship species consist of in situ conservation, captive breeding and reintroductions. With a few exceptions, we find limited evidence that knowledge of behavior informs conservation programs targeted at these species. For management in the wild, knowledge of infanticide and ranging can provide guidelines for realistic hunting quotas and corridors between protected areas, respectively. For ex situ and reintroduction programs, behavioral knowledge is chiefly focused on improved animal husbandry. Despite a formidable understanding of these species＇ behavior, the practicalities of using such knowledge may be diminished because exploitation of these species is so forceful and the bulk of efforts aimed at conserving these species （and indeed most other African species） are primarily in situ where behaviorally driven interventions are limited. Our comparative findings suggest that behavior has been of rather narrow use in the conservation of these flagship species [Current Zoology 60 （4）： 486--499, 2014].

关键词： African elephant Black rhinoceros Buffalo Flagship species Leopard Lion White rhinoceros

Novel insights in phosphodiesterase 4 subtype inhibition to target neuroinflammation and stimulate remyelination

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Neural Regeneration Research 2024年第3期19卷 493-494页

作者： Melissa Schepers tim Vanmierlo Department of Neuroscience Biomedical Research InstituteFaculty of Medicine and Life SciencesHasselt UniversityHasseltBelgium Department of Psychiatry and Neuropsychology School for Mental Health and NeuroscienceMaastricht UniversityMaastrichtNetherlands University MS Center(UMSC)Hasselt-Pelt HasseltBelgium

In neurodegenerative and classically demyelinating disorders such as multiple sclerosis(MS),spinal cord injury(SCI),stroke,and Charcot-Marie-Tooth disease,glial functioning is compromised and nervous tissue integrity is ***,primary neurodegenerative disorders such as Alzheimer’s disease,amyotrophic lateral sclerosis(ALS),and Parkinson’s disease(PD)are increasingly linked to impaired oligodendroglia functioning upon *** to the destructive micro-environment created by nervous tissue damage,the progressive cellular loss in these disorders,and the amitotic nature of neurons,spontaneous endogenous repair process are limited in ***,there is a medical need for efficient therapeutic strategies capable of supporting neuro-reparative processes to occur,likely supported by improved oligodendroglia cell functioning.

关键词： impaired inflammation Marie

A Special MJO Event with a Double Kelvin Wave Structure

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Journal of Meteorological Research 2017年第2期31卷 295-308页

作者： Lili ZHU tim LI Key Laboratory of Meteorological Disaster Ministry of Education/Joint International Research Laboratory of Climate and Environmental Change/Collaborative Innovation Center on Forecast and Evaluation of Meteorological DisastersNanjing University of Information Science &Technology International Pacific Research Center and Department of Atmospheric Sciences University of Hawaii at Manoa

The second Madden–Julian Oscillation（MJO）event during the field campaign of the Dynamics of the MJO/Cooperative Indian Ocean Experiment on Intraseasonal Variability in the Year 2011（DYNAMO/CINDY2011）exhibi ted an unusual double rainband *** a wavenumber-frequency spectral filtering method,we unveil that this double rainband structure arises primarily from the Kelvin wave *** zonal phase speed of the double rainbands is about 7.9 degree per day in the equatorial Indian Ocean,being in the range of convectively coupled Kelvin wave phase *** convection and circulation anomalies associated with the Kelvin wave component are characterized by two anomalous convective cells,with low-level westerly（easterly）and high（low）pressure anomalies to the west（east）of the convective centers,and opposite wind and pressure anomalies in the upper *** a zonal wind–pressure phase relationship is consistent with the equatorial free-wave *** the freeatmospheric circulation was dominated by the first baroclinic mode vertical structure,moisture and vertical motion in the boundary layer led the *** convection and circulation structures derived based on the conventional MJO filter show a different *** example,the phase speed is slower（about 5.9 degree per day）,and there were no double convective *** suggests that MJO generally involves multi-scales and it is incomplete to extract its signals by using the conventional filtering technique.

关键词： Madden–Julian Oscillation(MJO) double Kelvin wave structure Wheeler–Kiladis space–time spectra evolution characteristics