Climatic Factors for Limiting Northward Distribution of Eight Temperate Tree Species in Eastern North America

Eight temperate deciduous tree species, Acer rubrum L., A. saccharinum L., A. saccharum Marsh., Belluta alleghaniensis Britton., Fraxinus nigra Marsh., Quercus rubra L., Titia americana L., and Ulmus americana L. in eastern North America, were selected to explore relationship between the northward distribution of temperate tree species and climatic factors. For each species, more than 30 sites at their north limits of distribution were obtained from their distribution maps, and 11 climatic indices at the north limits were computed. The standardized standard deviation (SD) method, which compares the magnitude of variance of climatic indices, was used to detect which climatic parameter was the most important for explaining northward distribution of these species. We presume that the climatic parameter that has the smallest variance at the north limit would be assigned as the dominant climatic factor for limiting the distribution of this species. The results derived from the standardized SD method indicated that the SD value of warmth index (WI) and/or annual biotemperature (ABT) were the smallest among the 11 climatic indices. Since both WI and ABT represent growing season temperature, it suggested that growing season temperature was the most important climatic factor for explaining the northward distribution of these temperate tree species. The relationships between several climatic indices, WI, coldness index (CI), annual precipitation (AP), annual range of temperature (ART) and humid/arid index were also analyzed. As a result, at the north limits of all these species, both WI and CI decreased with an increase of AP, and CI increased with an increase of ART. Besides growing season temperature, precipitation and climatic continentality also have influence on the northward distribution of the temperate trees in eastern North America.

The Northward Shift of Climatic Belts in China During the Last 50 Years and the Corresponding Seasonal Responses

Along the meridian of 105°E, the Chinese region are divided into two parts, east and west. The results show that in the east part of China the temperate extratropical belt, the warm extratropical belt, and the northern subtropical belt shift northward significantly, whereas the middle subtropical belt and the southern subtropical belt have less or no change. As for the northern subtropical belt, the maximal northward shift can reach 3.7 degrees of latitude. As for the warm extratropical belt, along the meridian of 120°-125°E, the maximal northward shift can reach 3-4 degrees. In the west part of China, each climatic belt changes little. Only in the Xinjiang area are the significant northward shifts. Correspondingly, it is found that in the last 50 years the traditional seasons have changed. For Beijing, Hailar, and Lanzhou, in general, summer becomes longer and winter shorter over the last 50 years. Summer begins early and ends late with respect to early 1950s. Contrary to the summer, winter begins late and ends early with respect to early 1950s. Furthermore, spring and autumn have changed over the last 50 years: with respect to early 1950s spring begins early and autumn begins late.

The two annual northward jumps of the West Pacific Subtropical High and their relationship with summer rainfall in Eastern China under global warming

The two northward jumps of summer West Pacific Subtropical High （WPSH） are defined based on the pentad-scale ridge data of the WPSH ridge in 1951 to 2012. The times of the northward jumps are found to have obvious inter-annual and decadal characteristics, i.e., the occurrence of the first northward jump of WPSH shows a ＂consistently early-consistently late＂ decadal pattern, with the transition around 1980; the occurrence of the second northward jump of WPSH shows a ＂consistently late-consistently early-consistently late＂ decadal pattern, with the transitions about 1955 and 1978, respec- tively, which is consistent with global warming. In the meantime, the times of the two northward jumps not only have a good correspondence to the beginning and ending dates of the rainy season, but also greatly influence the position of the main rain belt in Eastern China. When the first northward jump occurs early, the main rain belt is located from just north of 30~ N to the south of North China, while the opposite situation appears when the first jump occurs late. When the second jump occurs early, more rain falls over North China and South China, but less falls in the Yangtze River region, while the opposite situation appears when the second jump occurs late. In the four cases when abnormalities occur in the same year as early or late northward jumps, the position of the main rain belt can be considered as a superposition of isolated abnormal effects of the two northward jumps. Moreover, the prophase and synchronous forces of the sea surface temperature in the Pacific has great influence on the times of the northward jumps, and the driving forces of the two jumps differ.

Two Northward Jumps of the Summertime Western Pacific Subtropical High and Their Associations with the Tropical SST Anomalies

Based on the pentad mean ridgeline index of the western Pacific subtropical high (WPSH), the authors identified the two northward jumps of the WPSH from 1979 to 2008 and revealed their associations with the tropical SST anomalies. The authors show that the northward jumps, especially the second jump, exhibited remarkable interannual variability. In addition, the authors find that the two northward jumps were mutually independent and were influenced by the SST anomalies in the different regions of the tropical Pacific. The first jump was positively correlated with the SST anomalies in the tropical central Pacific from the preceding winter to June. In contrast, the second jump was positively related to ENSO in the preceding winter, but this correlation tended to weaken with the decay of ENSO and disappeared in July. Instead, a positive correlation was found in the Indian Ocean. We therefore suggest that ENSO plays an indirect role in the second jump through the capacitor effect of the Indian Ocean.

Northward Shift in Landfall Locations of Tropical Cyclones over the Western North Pacific during the Last Four Decades

This study analyzes landfall locations of tropical cyclones(TCs)over the western North Pacific during 1979–2018.Results demonstrate that the landfall locations of TCs over this region have shifted northward during the last four decades,primarily due to the shift of landfalling TC tracks,with the decreasing/increasing proportion of westward/northward TC tracks.In particular,the northward shift of the landfalling TCs was not related to their formation locations,which have not markedly changed,whereas"no-landed"TCs have significantly shifted northward.TC movement was significantly and positively correlated to the zonal component of the steering flow,while the correlation between TC movement and the meridional component of the steering flow was relatively unobvious.The westward steering flow in the tropical central Pacific that occurred around the formation and early development of the westward TCs was significantly weakened,which was unfavorable for their westward movement,thereby,causing the higher proportions of northward moving tracks.This weakened westward flow was related to the northward shift of the subtropical high ridge,which was caused by significant weakening of the southern part of the subtropical high.The vertical wind shear,sea surface temperature,and convective available potential energy also showed that the northern region of the western North Pacific became more favorable for TC development,whereas the upper divergence,low-layer relative vorticity,and accumulated water vapor content were not obviously related to the northward shift of TCs.

Intensified Eastward and Northward Propagation of Tropical Intraseasonal Oscillation over the Equatorial Indian Ocean in a Global Warming Scenario

Northward propagation in summer and eastward propagation in winter are two distinguished features of tropical intraseasonal oscillation （TISO） over the equatorial Indian Ocean. According to numerical modeling results, under a global warming scenario, both propagations were intensified. The enhanced northward propagation in summer can be attributed to the enhanced atmosphere-ocean interaction and the strengthened mean southerly wind; and the intensified eastward propagation in winter is associated with the enhanced convection-wind coupling process and the strengthened equatorial Kevin wave. Future changes of TISO propagations need to be explored in more climate models.

Impacts of Two Types of Northward Jumps of the East Asian Upper-tropospheric Jet Stream in Midsummer on Rainfall in Eastern China

The East Asian upper-tropospheric jet stream （EAJS） typically jumps north of 45~N in midsummer. These annual northward jumps are mostly classified into two dominant types： the first type corresponds to the enhanced westerly to the north of the EAJS＇s axis （type A）, while the second type is related to the weakened westerly within the EAJS＇s axis （type B）. In this study, the impacts of these two types of northward jumps on rainfall in eastern China are investigated. Our results show that rainfall significantly increases in northern Northeast China and decreases in the Yellow River-Huaihe River valleys, as well as in North China, during the type A jump. As a result of the type B jump, rainfall is enhanced in North China and suppressed in the Yangtze River valley. The changes in rainfall in eastern China during these two types of northward jumps are mainly caused by the northward shifts of the ascending air flow that is directly related to the EAJS. Concurrent with the type A （B） jump, the EAJS-related ascending branch moves from the Yangtze-Huai River valley to northern Northeast （North） China when the EAJS＇s axis jumps from 40~N to 55~N （50~N）. Meanwhile, the type A jump also strengthens the Northeast Asian low in the lower troposphere, leading to more moisture transport to northern Northeast China. The type B jump, however, induces a northwestward extension of the lower-tropospheric western North Pacific subtropical high and more moisture transport to North China.

Upper layer waters and their northward extension from Prydz Bay in summer

In this paper, CTD observational data obtained during the 15th Chinese National Antarctic Research Expedition (CHINARE-15) in the Southern Ocean are used to analyse and study water mass distribution in the Prydz Bay and its adjacent seas. The area, depth, and the thermohaline characteristics are identified for the Prydz Bay summer coastal surface water, the Prydz Bay winter water, the Prydz Bay shelf water, and the circumpolar deep water. Based on the above discussion, the northward extention of the Prydz Bay shelf water are found. Then the thermodynamic and the dynamic characteristics are further discussed, dealing with the inversion layer depth of the water temperature, the locations of the minima of the vertical temperature distribution and the temperature vertical gradient in the water column, the baraclinicity, and the effect of Coriolis deflection force.

Northward expansion of the western Pacific Warm Pool in late 1990s and early 2000s

Based on 48-year (1958-2006) ocean reanalysis data of Simple Ocean Data Assimilation and 23-year (1984-2006) global ocean-surface heat flux products developed by the Objectively Analyzed Air-Sea Heat Flux Project, meridional variation of the western Pacific Warm Pool (WPWP) is addressed. The results show that there is a significant expansion of the northern edge of the WPWP in the late 1990s and early 2000s. This variation is mainly within 120°E-160°E by 8°N-20°N, we define this region (120°E-160°E by 8°N-20°N) as the core region. Furthermore, analyses on upper ocean heat budget show that the short wave radiation plays a key role in the northward expansion of the northern edge of the WPWP in the core region. It is proved that the northward expansion may be caused by the change of the mixed layer which became shallower in 1994-2006 compared with 1984-1993 in the study region. The short wave radiation flux distribution within the shallower mixed layer leads to a positive anomaly in seawater temperature, promoting the northward expansion of the WPWP.

A DIAGNOSTIC RESEARCH OF THE SEASONAL NORTHWARD BEATING OF THE SUBTROPICAL HIGH

Diagnostic techniques of CEOF, power spectrum and bandpass filter wave are applied in this paper to analyze the seasonal northward beating of the northern subtropical high using day to day geopotential fields of 2.5 ×2.5 at 500 hPa May through July in 1988 and 1991. It is concluded that it is globally observed that the subtropical high has northward beats that propagate westward; the source of beating mainly lies in the region of Arabian Sea and central Pacific and the sink in eastern Pacific; the seasonal beating is dominated by effects of the disturbance field; low frequency oscillation plays a key role in the beating and the westward propagation so that the difference in the latter in individual years is caused by the varying source of disturbance and the low frequency waves it excites.

Relationship between a function of the northward pressure gradient and the Pacific Equatorial Undercurrent

The Equatorial Undercurrent（EUC） plays an important role in ocean circulation and global climate change. Near the equator, as the Coriolis parameter goes to 0, equatorial currents cannot be described by geostrophy in which the pressure gradient force term is balanced by the Coriolis force term. Many previous studies focus on the relationships between the EUC and El Ni？o-Southern Oscillation（ENSO）, the thermocline, sea surface topography, the distribution of equatorial wind stress and other atmosphere-ocean factors. However, little attention has been paid to the northward pressure gradient（NGT）, which may also be important to the EUC. The pressure can be regarded as a complex nonlinear function of terms including temperature, salinity and density.This study attempts to reveal the connection between a function of the northward pressure gradient（FNP） and the EUC. The connection is derived from primitive equations, by simplifying the equations with using scaling analysis, and shows that the beta effect may be the main reason why the FNP is important to the EUC. The vertical structure of the EUC can be partially described by the FNP. The NGT has an obvious influence on the EUC while the eastward pressure gradient has a relatively smaller effect.

Early Cretaceous subduction initiation beneath southern Tibet caused the northward flight of India

Collision between the Indian and Eurasian plates formed the ~2500 km long Yarlung Zangbo Suture Zone and produced the Himalaya mountains and Tibetan plateau.Here we offer a new explanation for tectonic events leading to this collision:that the northward flight of India was caused by an Early Cretaceous episode of subduction initiation on the southern margin of Tibet.Compiled data for ophiolites along the Yarlung Zangbo Suture Zone show restricted ages between 120 Ma and 130 Ma,and their supra-subduction zone affinities are best explained by seafloor spreading in what became the forearc of a north-dipping subduction zone on the southern margin of Tibet.The subsequent evolution of this new subduction zone is revealed by integrating data for arcrelated igneous rocks of the Lhasa terrane and Xigaze forearc basin deposits.Strong slab pull from this new subduction zone triggered the rifting of India from East Gondwana in Early Cretaceous time and pulled it northward to collide with Tibet in Early Paleogene time.

Northward Heat Flux in Midwest Summers

Watching the winds in northwest Iowa during more than 30 summers has led me to two conclusions about the local atmosphere at ground level: there is a net northward transport of heat and water taking place throughout the summer;warm humid winds from the south continually alternate with cool dry winds from the north. The proposed northward heat transfer is consistent with the constraint, placed on the motions of the oceans and the atmosphere, of the earth’s heat balance due to the increased absorption of solar radiation at low latitudes compared to that at high latitudes. At mid-latitudes in the interior of continents, like North America, it is the job of the atmosphere alone to constantly help satisfy the global heat balance. Although qualitative in nature, the predicted northward heat flux is strongly based on frequent observations over lengthy time intervals.

Northward Movement and Highly-Qualified Cultivation Technology of Super-early Maturing Ratoon Rice

Objective] The alm was to expIore northward movement and highIy-quali-fied cuItivation technoIogy of super-earIy maturing ratoon rice. [Method] The 2nd-sea-son rice was cuItivated in the test with suitabIe temperature, heat water and fertiIiz-er, on basis of stubbIes of the 1st-season rice. Hence, rice can be harvested twice per year, with short growth periods, and high yields, and the cuItivation is simpIe to be operated, avoiding the peak of disease damages, so that pesticides are not re-quired. [Result] The experiment of northward movement of super-earIy rice achieved success in Shenyang on October 9, 2014, with super-earIy maturing japonica rice 8501. [Conclusion] Northward movement of ratoon rice enjoys a promising prospect in increasing crop yield and guaranteeing food security.

Interdecadal Change of the Northward Jump Time of the Western Pacific Subtropical High in Association with the Pacific Decadal Oscillation

In this paper, the northward jump time of the western Pacific subtropical high（WPSH） is defined and analyzed on the interdecadal timescale. The results show that under global warming, significant interdecadal changes have occurred in the time of the WPSH northward jumps. From 1951 to 2012, the time of the first northward jump of WPSH has changed from ＂continuously early＂ to ＂continuously late＂, with the transition occurring in 1980. The time of the second northward jump of WPSH shows a similar change, with the transition occurring in 1978. In this study, we offer a new perspective by using the time of the northward jump of WPSH to explain the eastern China summer rainfall pattern change from ＂north-abundant-southbelow-average＂ to ＂south-abundant-north-below-average＂ at the end of the 1970 s. The interdecadal change in the time of the northward jump of WPSH corresponds not only with the summer rainfall pattern, but also with the Pacific decadal oscillation（PDO）. The WPSH northward jump time corresponding to the cold（warm） phase of the PDO is early（late）. Although the PDO and the El Nino–Southern Oscillation（ENSO）both greatly influence the time of the two northward jumps of WPSH, the PDO＇s effect is noticed before the ENSO＇s by approximately 1–2 months. After excluding the ENSO influence, we derive composite vertical atmospheric circulation for different phases of the PDO. The results show that during the cold（warm）phase of the PDO, the atmospheric circulations at 200, 500, and 850 h Pa all contribute to an earlier（later）northward jump of the WPSH.

Impact of 10-60-Day Low-Frequency Steering Flows on Straight Northward-Moving Typhoon Tracks over the Western North Pacific

This study investigates the impact of low-frequency(intraseasonal and interannual) steering flows on straight northward-moving(defined as a meridional displacement two times greater than the zonal displacement) typhoons over the western North Pacific using observational data. The year-to-year change in the northward-moving tracks is affected by the interannual change in the location and intensity of the subtropical high. A strengthened northward steering flow east of 120°E and a weakened easterly steering flow south of the subtropical high favor more frequent straight northward tracks. Examining each of the individual northward-moving typhoons shows that they interact with three types of intraseasonal(10-60-day) background flows during their northward journey. The first type is the monsoon gyre pattern, in which the northward-moving typhoon is embedded in a closed cyclonic monsoon gyre circulation. The second type is the wave train pattern, where a cyclonic(anticyclonic) vorticity circulation is located to the west(east) of the northward-moving typhoon center. The third type is the mid-latitude trough pattern, in which the northward-moving typhoon center is located in the maximum vorticity region of the trough.

Factors controlling northward and north-eastward moving tropical cyclones near the coast of East Asia

The impacts of multi-time-scale flows on northward and north-eastward moving tropical cyclones(TCs)near the east coast of China in August and September are investigated using reanalysis data from 1982 to 2012.TCs of interest are under the influence of the subtropical high-pressure system in the western North Pacific(WNP).In August when the subtropical highpressure system is strong and close to the coast line,most TCs in the region move northward,while more TCs move north-eastward in September when the subtropical highpressure system retreats to the east.To investigate the influence from different time-scales,the environmental flow is divided intofour components,the synoptic flow,the intraseasonal flow,the interannual flow and the climatological background field.Analysis of steering flows between 25°N and 30°N indicates that the meridional steering vectors from all time-scales point to the north,dominated by the intraseasonal component.The deciding factor on whether a TC moves to the north or north-east between 25°N and 30°N is the zonal steering vector.For the northward moving group,the sum of the zonal steering from all time-scales is very small.On the other hand,the north-east moving group has a net eastward zonal component mainly contributed by the climatological mean flow.Several individual cases that stood out from the majority of the group are analyzed.For those cases,the intraseasonal flow plays an important role in affecting the movement of the TCs mainly through the wave train,in which a cyclonic circulation is located to the north-west(north)and an anticyclonic circulation to the south-east(east)of TCs.The analysis of the steering vectors indicates the importance of all components with different timescales to the movement of TCs.

Global warmingwill shift the East Asian monsoon rain belt northward

With the support by the National Natural Science Foundation of China and the Chinese Academy of Sciences,the research team led by Prof.Yang ShiLing(杨石岭)and Prof.Ding ZhongLi(丁仲礼)at the Key Laboratory of Cenozoic Geology and Environment,Institute of Geology and Geophysics,Chinese Academy of Sciences,reported recently that global warming will shift the East Asian monsoon rain

Decadal northward shift of the Meiyu belt and the possible cause

The feature of the decadal movement of the Meiyu belt and their association with East Asia atmospheric circulation for the period of 1979―2007 is examined in this study. It is shown that the Meiyu belt of China has a decadal shift in the late 1990s. There is a remarkable difference between the periods before and after 1999, with the Meiyu belt mainly located to the south of the Yangtze River valley before 1999, but afterward mainly located in the Huaihe River valley. At the same time, a distinctive tropospheric warming and stratospheric cooling trend is found in the mid-latitudes of East Asia, which causes the upper tropospheric pressure surfaces upward bulging and the tropoause elevated in the subtropics and associated widening of the subtropical area over East Asia. Accompanying the subtropics widening, the subtropical westerly jet over East Asia shifts northward and the East Asia tropical Hadley circulation expands poleward, which results in the northward shift of the Meiyu belt.

以确保“一泓清水永续北上” 引领南水北调中线水源区水土保持高质量发展

丹江口库区及上游是南水北调中线水源区(以下简称“水源区”),其水土保持高质量发展是保障“一泓清水永续北上”的重要支撑。文章针对水源区水土流失现状和特点,总结了丹江口库区及上游水土保持重点防治工程(以下简称“丹治”工程)实施以来的水土保持成效,分析了水土保持面临的新形势和新要求,梳理了水土保持存在的短板和不足,研究提出了引领丹江口库区及上游水土保持高质量发展的对策举措,为各级政府加强南水北调中线水源区水土保持治理管理提供参考。