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Parameterization for the Depth of the Entrainment Zone above the Convectively Mixed Layer

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Advances in atmospheric sciences 2005年第1期22卷 114-121页

作者：孙鉴泞蒋维楣陈子赟袁仁民 department of atmospheric sciences department of Earth and Space sciences

It has been noted that when the convective Richardson number Ri* is used to characterize the depth of the entrainment zone, various parameterization schemes can be obtained. This situation is often attributed to the invalidity of parcel theory. However, evidence shows that the convective Richardson number Ri* might be an improper characteristic scaling parameter for the entrainment process. An attempt to use an innovative parameter to parameterize the entrainment-zone thickness has been made in this paper. Based on the examination of the data of water-tank experiments and atmospheric measurements, it is found that the total lapse rate of potential temperature across the entrainment zone is proportional to that of the capping inversion layer. Inserting this relationship into the so-called parcel theory, it thus gives a new parameterization scheme for the depth of the entrainment zone. This scheme includes the lapse rate of the capping inversion layer that plays an important role in the entrainment process. Its physical representation is reasonable. The new scheme gives a better ordering of the data measured in both water-tank and atmosphere as compared with the traditional method using Ri*. These indicate that the parcel theory can describe the entrainment process suitably and that the new parameter is better than Ri*.

关键词： convectively mixed layer the depth of the entrainment zone capping inversion layer parameterization scheme parcel theory

New findings on the influence of El Nino events on tropical cyclone formation

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Science China Earth sciences 2024年第3期67卷 892-893页

作者： Liguang WU department of atmospheric and Oceanic sciences Institute of Atmospheric SciencesFudan UniversityShanghai 200438China

Tropical cyclones typically form over warm tropical and subtropical ocean surfaces, as their formation and intensification rely primarily on the energy provided by the ocean. Pioneering research by Gray (1968) revealed that the formation of tropical cyclones requires the sea surface temperature (SST) to be no less than 26.5℃. Consequently, SST is commonly recognized as a crucial parameter among the environmental factors influencing tropical cyclone formation(Gray, 1979;Emanuel and Nolan, 2004).

关键词： tropical cyclone ocean

Ensembles vs. information theory: supporting science underuncertainty

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Frontiers of Earth Science 2018年第4期12卷 653-660页

作者： Grey S.NEARING Hoshin V.GUPTA University of Alabama Department of Geological SciencesTuscaloosaAL 35294-1152USA University of Arizona Department of Hydrology and Atmospheric SciencesTucsonAZ 85721-0158USA

Multi-model ensembles are one of the most common ways to deal with epistemic uncertainty in hydrology. This is a problem because there is no known way to sample models such that the resulting ensemble admits a measure that has any systematic (i.e., asymptotic, bounded, or consistent) relationship with uncertainty. Multi-model ensembles are effectively sensitivity analyses and cannot – even partially – quantify uncertainty. One consequence of this is that multi-model approaches cannot support a consistent scientific method – in particular, multi-model approaches yield unbounded errors in inference. In contrast, information theory supports a coherent hypothesis test that is robust to (i.e., bounded under) arbitrary epistemic uncertainty. This paper may be understood as advocating a procedure for hypothesis testing that does not require quantifying uncertainty, but is coherent and reliable (i.e., bounded) in the presence of arbitrary (unknown and unknowable) uncertainty. We conclude by offering some suggestions about how this proposed philosophy of science suggests new ways to conceptualize and construct simulation models of complex, dynamical systems.

关键词： information theory multi-model ensembles Bayesian methods uncertainty quantification hypothesis testing

Simulated effects of interactions between ocean acidification,marine organism calcification, and organic carbon export on ocean carbon and oxygen cycles

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Science China Earth sciences 2018年第6期61卷 804-822页

作者： Han ZHANG Long CAO department of atmospheric sciences School of Earth Sciences Zhejiang University

Ocean acidification caused by oceanic uptake of anthropogenic carbon dioxide(CO_2) tends to suppress the calcification of some marine organisms. This reduced calcification then enhances surface ocean alkalinity and increases oceanic CO_2 uptake, a process that is termed calcification feedback. On the other hand, decreased calcification also reduces the export flux of calcium carbonate(Ca CO_3), potentially reducing Ca CO_3-bound organic carbon export flux and CO_2 uptake, a process that is termed ballast feedback. In this study, we incorporate a range of different parameterizations of the links between organic carbon export, calcification, and ocean acidification into an Earth system model, in order to quantify the long-term effects on oceanic CO_2 uptake that result from calcification and ballast feedbacks. We utilize an intensive CO_2 emission scenario to drive the model in which an estimated fossil fuel resource of 5000 Pg C is burnt out over the course of just a few centuries. Simulated results show that, in the absence of both calcification and ballast feedbacks, by year 3500, accumulated oceanic CO_2 uptake is2041 Pg C. Inclusion of calcification feedback alone increases the simulated uptake by 629 Pg C(31%), while the inclusion of both calcification and ballast feedbacks increase simulated uptake by 449–498 Pg C(22–24%), depending on the parameter values used in the ballast feedback scheme. These results indicate that ballast effect counteracts calcification effect in oceanic CO_2 uptake. Ballast effect causes more organic carbon to accumulate and decompose in the upper ocean, which in turn leads to decreased oxygen concentration in the upper ocean and increased oxygen at depths. By year 2600, the inclusion of ballast effect would decrease oxygen concentration by 11% at depth of ca. 200 m in tropics. Our study highlights the potentially critical effects of interactions between ocean acidification, marine organism calcification, and Ca CO3-bound organic carbon

关键词： Ocean carbon cycle Ocean acidification Carbon cycle modeling Carbon cycle-climate feedback

Simulated effect of sunshade solar geoengineering on the global carbon cycle

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Science China Earth sciences 2018年第9期61卷 1306-1315页

作者： Jiu JIANG Han ZHANG Long CAO department of atmospheric sciences School of Earth Sciences Zhejiang University

Solar geoengineering has been proposed as a potential mechanism to counteract global wanning. Here we use the University of Victoria Earth System Model （UVic） to simulate the effect of idealized sunshade geoengineering on the global carbon cycle. We conduct two simulations. The first is the A2 simulation, where the model is driven by prescribed emission scenario based on the SRES A2 COz emission pathway. The second is the solar geoengineering simulation in which the model is driven by the A2 CO2 emission scenario combined with sunshade solar geoengineering. In the model, solar geoengineering is represented by a spatially uniform reduction in solar insolation that is implemented at year 2020 to offset CO2-induced global mean surface temperature change. Our results show that solar geoengineering increases global carbon uptake relative to A2, in particular CO2 uptake by the terrestrial biosphere. The increase in land carbon uptake is mainly associated with increased net primary production （NPP） in the tropics in the geoengineering simulation, which prevents excess warming in tropics. By year 2100, solar geoengineering decreases A2-simulated atmospheric CO2 by 110 ppm （12%） and causes a 60% （251 Pg C） increase in land carbon accumulation compared to A2. Solar geoengineering also prevents the reduction in ocean oxygen concentration caused by increased ocean temperatures and decreased ocean ventilation, but reduces global ocean NPE Our results suggest that to fully access the climate effect of solar geoengineering, the response of the global carbon cycle should be taken into account.

关键词： Solar geoengineering Carbon cycle Climate change Ocean biogeochemistry

Environmental and tectonic significance of Late Permian reefs in the Linxi and adjacent areas in Inner Mongolia of China

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Science China Earth sciences 2016年第7期59卷 1463-1476页

作者： TIAN Shu Gang ZHANG Yong Sheng GONG Yue Xuan LI Zi Shun GAO Lian Da ZHAI Da Xing ZHU Chang Wei Institute of Geology Chinese Academy of Geological Sciences Institute of Mineral Resources Chinese Academy of Geological Sciences department of Science and Technology Chinese Academy of Geological Sciences

Many plateau-edge reefs and reef mounds of the Late Permian have been discovered in Linxi County and adjacent areas of Inner Mongolia, China. These reefs verify that the Hinggan-Inner Mongolia Area was an open and unobstructed sea-trough in Late Permian. Facies and sequences of reef strata in Member 4 and Member 5 of the Linxi Formation were studied for information to reconstruct the closing process of the Linxi-Jiutai chasm in the sea-trough, i.e., to constrain subsidence, uplift, and final closing. Ages of the reef-bearing strata have been determined to be late and end of Late Permian, based on ranges or abundances of diverse fossils. Six reef-building organic assemblages were distinguished, representing different ecologic conditions, according to morphological functions and paleoecological adaptations of organisms including primarily sponges, bryozoans, and calcareous algae. Two types of shelf slopes, the gentle slope and the steep slope, have been interpreted for Member 4 and Member 5 of the Linxi Formation, based on the assemblages. The locations of outcrops, and types of these reefs delineate the north margin of Sino-Korea Platform, and define uplift and final closing of the Linxi-Jiutai chasm at the end of Late Permian.

关键词： Reefs Facies sequence Paleoecology Late Permian Inner Mongolia

Mesoscale Modeling Study of Severe Convection over Complex Terrain

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Advances in atmospheric sciences 2016年第11期33卷 1259-1270页

作者： Ying ZHANG Zhiyong MENG Peijun ZHU Tao SU Guoqing ZHAI department of atmospheric sciences School of Earth SciencesZhejiang University department of atmospheric and Oceanic sciences School of PhysicsPeking University

Short squall lines that occurred over Lishui, southwestern Zhejiang Province, China, on 5 July 2012, were investigated using the WRF model based on 1°× 1° gridded NCEP Final Operational Global Analysis data. The results from the numerical simulations were particularly satisfactory in the simulated radar echo, which realistically reproduced the generation and development of the convective cells during the period of severe convection. The initiation of this severe convective case was mainly associated with the uplift effect of mesoscale mountains, topographic convergence, sufficient water vapor, and enhanced low-level southeasterly wind from the East China Sea. An obvious wind velocity gradient occurred between the Donggong Mountains and the southeast coastline, which easily enabled wind convergence on the windward slope of the Donggong Mountains; both strong mid–low-level southwesterly wind and low-level southeasterly wind enhanced vertical shear over the mountains to form instability; and a vertical coupling relation between the divergence on the upper-left side of the Donggong Mountains and the convergence on the lower-left side caused the convection to develop rapidly. The convergence centers of surface streams occurred over the mountain terrain and updrafts easily broke through the lifting condensation level（LCL） because of the strong wind convergence and topographic lift, which led to water vapor condensation above the LCL and the generation of the initial convective cloud. The centers of surface convergence continually created new convective cells that moved with the southwest wind and combined along the Donggong Mountains, eventually forming a short squall line that caused severe convective weather.

关键词： convective convection divergence mesoscale mountains instability southwestern terrain moved uplift

Experiment on Dust Flux During Duststorm Periods over Desert Area

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Acta meteorologica Sinica 2008年第2期22卷 239-247页

作者：张宏升朱好彭艳康凌陈家宜 Soon-Ung PARK Center of Sino-Korcan atmospheric sciences Department of Atmospheric SciencesPeking University Center of Sino-Korean atmospheric sciences Department of Atmospheric SciencesPeking University Center of Sino-Korean atmospheric sciences Department of Atmospheric SciencesSeoul National UniversitySeoul 151-742Korea

The present study investigates the characteristics of turbulent transfer and the conditions for dust emission and transport using the dust concentration and micrometeorological data obtained during dust events occurring in the spring of 2004 over the Hunshandake desert area. The turbulent exchange coefficients and turbulent fluxes of momentum and heat are calculated. The relationships between dust flux, friction velocity, and wind speed are also explored. The results show that thermal turbulence is dominant during daytime of non-dusty days. The dynamic turbulence increases obviously and the sensible heat flux reduces by different degrees during dust events. There is an efficient downward transfer of momentum before duststorm occurrence, and both the dynamic turbulence and the thermal turbulence are important in the surface layer. The dynamic turbulence even exceeds the thermal turbulence during severe duststorm events. The values of dust flux vary in the range of -5 5, -30 30, and -200-300 μg m^-2 s^-1 during non-dusty days, blowing dust, and duststorm events, respectively. A slight upward transport of dust is observed during non-dusty days. The dust flux gradually varies from positive to negative during duststorm periods, which indicates the time evolution of dust events from dust rising to stably suspending and then deposition. The dust flux is found to be proportional to u＊^3. The threshold values of wind speed and friction velocity are about 6 and 0.4 m s^-1, respectively.

关键词： turbulent transfer dust flux threshold friction velocity dust event Hunshandake desert area

Relationship between the Circumglobal Teleconnection and Silk Road Pattern over Eurasian continent

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Science Bulletin 2019年第6期64卷 374-376页

作者： Fuli Zhou Renhe Zhang Jinping Han Chinese Academy of Meteorological sciences University of Chinese Academy of sciences department of atmospheric and Oceanic sciences & Institute of atmospheric sciences Fudan University

During boreal summer, two remarkable upper-level wave trains over Eurasia were documented in literature, i.e., Circumglobal Teleconnection (CGT) and Silk Road Pattern (SRP). They are widely discussed because of their influences throughout the entire midlatitude Eurasia. SRP was defined by 200 hPa meridional winds [1]. Enomoto et al.[2] found that the wave train influenced the climate variation over Japan when they detected the mechanism of Bonin High, and then named it as "Silk Road Pattern". SRP has 3 prominent action centers, which are located in west-central Asia, Mongolia and the Far East, respectively [3].

关键词： During boreal summer remarkable upper-level located in west-central Asia