Urbanization and heterogeneous surface warming in eastern China

With the homogeneity-adjusted surface air temperature (SAT) data at 312 stations in eastern China for 1979-2008 and the Defense Meteorological Satellite Program/Operational Linescan System (DMSP/OLS) nighttime light data, the spatial heterogeneities of the SAT trends on different scales are detected with a spatial filtering (i.e. moving spatial anomaly) method, and the impact of urbanization in eastern China on surface warming is analyzed. Results show that the urbanization can induce a remarkable summer warming in Yangtze River Delta (YRD) city cluster region and a winter warming in Beijing-Tianjin-Hebei (BTH) city cluster region. The YRD warming in summer primarily results from the significant increasing of maximum temperature, with an estimated urban warming rate at 0.132-0.250℃ per decade, accounting for 36%-68% of the total regional warming. The BTH warming in winter is primarily due to the remarkable increasing of minimum temperature, with an estimated urban warming rate at 0.102-0.214℃ per decade, accounting for 12%-24% of the total regional warming. The temporal-spatial differences of urban warming effect may be attributed to the variation of regional climatic background and the change of anthropogenic heat release.     

Recent temperature increase recorded in an ice core in the source region of Yangtze River

Interests on climate change in the source region of Yangtze River have been raised since it is a region with the greatest warming over the Tibetan Plateau (TP). A 70-year history of precipitation δ~(18)O has been recovered using an ice core record retrieved in a plat portion of the firn area in the Guoqu Glacier (33°34′37.8″N, 91°10′35.3″E, 5720 m a.s.l.), Mt. Geladaindong (the source region of Yangtze River), in November, 2005. By using a significant positive relationship between ice core δ~(18)O record and summer air temperature (July to September) from the nearby meteorological stations, a history of summer air temperature has been reconstructed for the last 70 years. Summer temperature was relatively low in 1940s and high in 1950s to the middle of 1960s. The lowest temperature occurred in the middle of 1970s. Temperature was low in 1980s and dramatically increased since 1990s, keeping the trend to the begin-ning of the 21st century. The warming rate recorded in the ice core with 0.5℃/10 a since 1970s is much higher that that in the central TP and the Northern Hemisphere (NH), and it becomes 1.1℃/10 a since 1990s which is also higher than these from the central TP and the NH, reflecting an accelerated warm-ing and a more sensitive response to global warming in the high elevation region.     

1960－2011年华北平原城市化增温变化分析

利用华北平原9个气象观测台站1960—2011年地面和850 hPa高空气温资料分析华北平原的城市化变化特征。分析城市化对大中城市增温情况,以及应用高空与地面温度差的方法验证城市化增温的可行性。结果表明:地面与城市化增温速率和幅度均呈现上升趋势。大城市的城市化增温率以及城市化对地面增温的贡献率明显大于中等城市。冬春季是城市化增温作用最为明显的季节。1980—2011年的各台站城市化增温与1960—2011年整个时段相比有所变化。部分台站增温效应趋于增强,另外部分站的增温效应趋于弱化或消失。     

Latitudinal shift and tilt of the ring current during magnetic storms

The equatorial ring current (ERC) theory suggested that the distribution of global disturbed horizontal geomagnetic field only depends on the cosine of station’s latitude. However, we always observe a larger ΔH at higher latitude stations than lower ones, implying that the ERC could tilt or/and shift with respect to the equatorial plane during intense storms. In this paper, we analyze 11 intense magnetic storms from 2000 to 2004, and introduce two configurational factors to characterize the topology of storm time ring current. The results show that ERC has occasionally deviated off equatorial plane with both tilt angle δ_t≈13°―25° and latitude shift δ_s≈0°―21.8°. The ground disturbed field distribution should be improved as ΔH_k = ΔH_maxcos(φ_k-δ ), which agree well with the geomagnetic observations.     

Impacts of climate warming on heating energy consumption and southern boundaries of severe cold and cold regions in China

Impacts of climate warming on heating energy consumption and southern boundaries of severe cold and cold regions of China in the past 20 years are analyzed by using daily and monthly average tem- perature data from 590 weather stations in China and based on regulations of Heating Ventilation and Air Conditioning Design Rules (GB50019-2003) and Thermal Design Rules for Civil Building (GB50175-93) (China National Standard). The contribution of climate warming to coal saving for heating during cold seasons in major cities is calculated according to indices of coal consumption for heating in major cities during cold seasons defined in Energy Conservation Design Standard for New Heating Residential Buildings (JCJ26-95). Comparing with the period before 1980, southern boundaries of se- vere cold and cold regions shift toward north up to 2 degrees in latitude since the mid-1980s. Theo- retically, climate warming could contribute to 5%―10% coal savings for heating since the mid-1980s in major cities, and even more since the mid-1990s.     

Regional differences in the timing of recent air warming during the past four decades in China

Global surface temperature has dramatically increased in the past decades. It is critical to evaluate such a change using appropriate approaches. The previous studies for assessment of the change usually used overall trends of temperature series (i.e. slopes of simple linear regression of temperature versus year based on a least-square analysis) for entire study period. Temperature trends, however, differ among different periods, i.e. there are often breakpoints in the temperature series. Therefore, the overall linear trend of a temperature series may conceal some of the temporal characteristics of the temperature change. To precisely characterize the temporal and spatial patterns of air temperature change in China, we analyze the annual mean temperature series between the year of 1961–2004 for 536 meteorological stations across China, using piecewise linear regression approach. We found remarkable breakpoints in the annual mean temperature during the study period across the country. The annual mean temperature started to increase in 1984 at a rate of 0.058°C/a at the country level. The year when warming started appeared to be gradually later from the north to the south: temperature increased since the 1970s in the north (north of 40°N), and did not rise until the 1980s in most areas of the south (south of 40°N), with warming starting in 1983 in the Tibetan Plateau. The trends in annual mean temperatures showed a large spatial heterogeneity across China: a relatively small rising with a rate of 0.025–0.05°C/a in the Sichuan Basin, Central China and South China; the greatest increase in some parts of northwest China (i.e. Xinjiang) with up to a rate of 0.1°C/a; and rising at a rate of >0.05°C/a for most regions of the country. The feedbacks of cold waves and snow may be responsible for such regional differences in the timing and rates of warming in China.     

Twenty-five years of change in scleractinian coral communities of Daya Bay （northern South China Sea） and its response to the 2008 AD extreme cold climate event

Coral reefs worldwide are becoming increasingly and detrimentally impacted upon by a variety of factors including significant climate changes, such as global warming and increased El Nino-Southern Oscillation activity. Generally, the persistence of coral reefs, especially at low-latitudes, is governed, in part, by sea surface temperatures not exceeding the critical limit （-30℃） at which mass mortality can occur. Thus, it is thought that corals living at high-latitudes （i.e., currently cooler sea surface temperatures） will likely respond more favourably to hypothesized future temperature increases than corals living at low-latitudes （i.e., currently warmer sea surface temperatures）. Consequently, high-latitude coral communities may have the potential to act as regions of refugia for many coral species in the face of potential future global warming. The Daya Bay （22°31′--22°50′N）, northern South China Sea, contains several high-latitude non-reefal coral communities and represents one of the most northerly distributions of scleractinian corals within the region. Significantly, Daya Bay has experienced dramatic warming in both air and sea surface temperatures throughout the past 50 years. In this paper, we analyze 25 years of change in the Daya Bay coral communities, based both on historic surveys and our latest 2006--2008 regional ecological surveys. Our results suggest that, contrary to predictions, there have been significant declines in coral cover within the Daya Bay during the past 25 years （i.e., 76.6% coral cover in 1983/1984 to only 15.3% coral cover by 2008）. Such changes also reflect a significant shift in the most abundant coral species, from Acropora pruinosa to Favites abdita. Most of the modern coral communities became established between 15 and 30 years ago, corresponding to a period of increased winter sea surface temperature. However, very few colonies have become established within the last 15 years, despite a more intense period of warming. By taking into account additional factors, we hypothesize that direct anthropogenic impacts, rather than climatic events, have both restricted the development, and drove the decline, of Daya Bay coral communities in the last 15 years. The Daya Bay has also been subjected to occasional extreme cold events during the past 50 years, with the most recent occurring in early 2008 （13 January-13 February）. During the 2008 cold event, the lowest air temperature reaches only 6.6℃, and the mean sea surface temperature for February fall to 〈 14℃, including six continuous days at 12.3℃. Significantly, the sea surface temperatures fall below the hypothesized critical lower temperature threshold （-13℃） that commonly leads to mass mortality in scleractinian coral communities. Surprisingly, our coral community surveys, conducted both before （August 2007） and after （late February 2008） the extreme 2008 cold event, demonstrate that the Daya Bay coral ecosystems are barely impacted upon during the cold period. Those observations suggest that the Daya Bay scleractinian coral communities have developed adaptations to low sea surface temperatures. Overall, our data support the hypothesis that high-latitude coral communities, such as Daya Bay, have the potential to act as areas of refugia for scleractinian corals in the advent of potential future global warming.     

An experimental study of dehydration melting of phengite-bearing eclogite at 1.5―3.0 GPa

Dehydration melting experiments were performed on ultrahigh-pressure eclogite from Bixiling in the Dabie orogen at 1.5--3.0 GPa and 800--950℃ using piston cylinder apparatus. The results show that （1） eclogite with -5% phengite started to melt at T≤800--850℃ and P = 1.5--2.0 GPa and produced about 3% granitic melt; （2） the products of dehydration melting of phengite-bearing eclogite vary with temperature and pressure. Fluid released from dehydration of phengite and zoisite leads to partial melting of eclogite and formation of plagioclase reaction rim around kyanite at pressures of 1.5--2.0 GPa and temperatures of 800--850℃; （3） phengite reacted with omphacite and quartz and produced oligoclase, kyanite and melt at elevated temperatures. Oligoclase is the primary reaction product produced by partial melting of phengite in the eclogite; and （4） the dehydration melting of phengite-bearing eclogite at pressures of 1.5--3.0 GPa and temperatures ≥900℃ results in formation of garnets with higher molar fraction of pyrope （37.67 wt.%--45.94 wt.%）. Potassium feldspar and jadeite occur at P = 2.4--3.0 GPa and T≥900℃, indicating higher pressure and fluid-absent conditions. Our results constrain the solidus for dehydration melting of phengite-bearing eclogite at pressures of 1.5--3.0 GPa. Combining experi- mental results with field observations of partial melting in natural eclogites, we concluded that phengite-bearing eclogites from the Dabie-Sulu orogen were able to partially molten at P= 1.5--2.0 GPa and T= 800--850℃ during exhumation. The ultrahigh-high pressure eclogites would have experienced partial melting in association with metamorphic phase transformation under different fluid conditions.     

Interdecadal shift in the western North Pacific Summer SST anomaly in the late 1980s

An interdecadal shift in summer (June―August) sea surface temperature (SST) variations during the period of 1968―2002 was identified in the late 1980s, which is characterized by a phase alternating from negative to positive phases of the leading mode of the empirical orthogonal function (EOF) analysis of the summer monthly mean SST in the Pacific domain 100°―180°E and 0°―40°N, accounting for 30.5% of the total variance. During the period of 1968―1987, the leading mode with a mean negative phase state (mean standard deviation = ?0.586) controlled SST variability in the western North Pacific. Correspondingly, negative SST anomalies occupied the western North Pacific south of Japan and Chinese marginal seas. During the period of 1988―2002, the leading mode shifted to its strong positive polarity (mean standard deviation = 0.781), thus positive SST anomalies appeared in the western North Pacific. Accompanied by the interdecadal shift in summer mean SST, summer mean rainfall increased in southern and southeastern China during the late period, particularly in southeastern China where increase in summer mean rainfall exceeded 40 mm, at the 0.05 significance level.     

Climatic changes in the Twenty-four Solar Terms during 1960–2008

The temperature thresholds and timings of the 24 climatic Solar Terms in China are determined from a homogenized dataset of the surface air temperature recorded at 549 meteorological stations for the period 1960?C2008 employing the ensemble empirical mode decomposition method. Changes in the mean temperature and timing of the climatic solar terms are illustrated. The results show that in terms of the mean situation over China, the number of cold days such as those of Slight Cold and Great Cold has decreased, especially by 56.8% for Great Cold in the last 10 years (1998?C2007) compared with in the 1960s. The number of hot days like those of Great Heat has increased by 81.4% in the last 10 years compared with in the 1960s. The timings of the climatic Solar Terms during the warming period (around spring) in the seasonal cycle have advanced significantly by more than 6 d, especially by 15 d for Rain Water, while those during the cooling period (around autumn) have delayed significantly by 5?C6 d. These characteristics are mainly due to a warming shift of the whole seasonal cycle under global warming. However, the warming shift affects the different Solar Terms to various extents, more prominently in the spring than in the autumn. The warming tendencies for Rain Water, the Beginning of Spring, and the Waking of Insects are the largest, 2.43°C, 2.37°C, and 2.21°C, respectively, for the period 1961?C2007 in China as a whole. Four particular phenology-related climatic Solar Terms, namely the Waking of Insects, Pure Brightness, Grain Full, and Grain in Ear, are found to have advanced almost everywhere. In semi-arid zones in northern China, advances of the timings of these four climatic Solar Terms are significant, 12?C16, 4?C8, 4?C8, and 8?C12 d, respectively, for the period 1961?C2007. These quantitative results provide a scientific base for climate change adaptation, especially in terms of agricultural planning and energy-saving management throughout a year.     

New Early Triassic paleomagnetic data from Huangben section, Guangdong and its tectonic implications

Continent China is composed of several blocks of variable sizes during different geological times, inwhich South China Block is composed of three tectonic units: Yangtze Block, Jiangnan Fold Belt and Southeast China Coastal Fold Belt (Fig. 1(a)), the last…     

Formate and acetate as recorded in a mid－latitude glacier in west China

Formic (HCOOH) and acetic (CH3COOH) acids are the chief carboxylic compounds in the troposphere[1]. Although weak acids, they contribute significantly to the free acidity, ionic balance of precipitation and the chemical reactions in the atmosphere, especially in the remote areas[2—4]. General sources for formate and acetate have been identified in the past 3 decades although a satisfactory source attribution is lacking to explain atmospheric observations[5]. Possible sources include veget…     

Sea surface temperature record from the north of the East China Sea since late Holocene

Using the alkenone paleotemperature index U37^k, a high-resolution sea surface temperature （SST） record since 3600 a BP was reconstructed from the mud area in the north of the East China Sea. Combining with the grain size distribution curve of sensitive grain size group, which may reflect the East Asia Winter Monsoon activity, the palaeoenvironmental evolution cycle throughout the late Holocene in the area was obtained. The marine environment evolution during the last 3600 years displays a five-stage trend. （1） Temperature descending period from 0.85 cal. ka BP to present. The maximum temperature decrease amplitude is 2℃. The winter monsoon intensified and ＇Little Ice Age＇ were recorded in this period. （2） Warming period from 1.90 to 0.85 cal. ka BP. The mean temperature increase amplitude is 0.8℃. The Sui-Tang warming period was recorded at about 0.85--1.35 cal. ka BP and a prominent cooling event was recorded at 1.4 cal. ka BP in this period. （3） Temperature descending period from 2.55 to 1.90 cal. ka BP. Temperature cooling amplitude is 0.9℃. This period is coincident with an integrated temperature circle recorded in the Antarctic ice core, with the temperature changes from a slow cooling stage to a rapid warming stage. （4） Temperature comparatively stable with a little ascending period from 3.2 to 2.55 cal. ka BP. Temperature warming amplitude is 0.3℃. This period is coincident with the temperature fluctuant ascending period recorded in Antarctic ice core. （5） Temperature comparatively stable with little descending period from 3.6 to 3.2 cal. ka BP. This period corresponds with the temperature fluctuant cooling period recorded in Antarctic ice core. Basically, those five periods were coincident with the Antarctic ice core record. During the global cooling stage, the SST change in the continental shelf sea can be adjusted simultaneously.     

Vp of muscovite-biotite gneiss up to 950℃ at 400 MPa: Constraints on the origin of abnormal seismic layers in continental crust

Here we present experimental results of compressional wave velocity (Vp) of muscovite-biotite gneiss from Higher Himalayan Crystallines (HHC) at the temperature up to 950℃ and the pressure of 0.1―400 MPa. At 400 MPa, when the temperature is lower than 600℃, Vp decreases linearly with increasing temperature at the rate of (Vp/T)p -4.43×10-4 km/s ℃. In the temperature range of 600―800℃, Vp drops significantly and the signal is degraded gradually due to the dehydration of muscovite and α-quartz softening. When the temperature rises from 800℃ to 875℃, Vp increases and the signals become clear again as a result of the temperature going through the β-quartz range. The experiments indicate that the duration has great influence on the experimental results when temperature is above the dehydration point of biotite. During the first 30 h at 950℃, the Vp decreases substantially from 5.9 to 5.4 km/s and the signal amplitude is attenuated by more than 80%. After the 30-h transition, the Vp and the amplitude of ultrasonic wave signals become steady. The decrease of Vp and attenuation of the signals at 950℃ are associated with the breakdown reactions of biotite. The experiments suggest that the breakdown of muscovite and/or quartz softening can contribute to the low seismic wave velocity in thickened quartz-rich felsic-crust such as what is beneath southern Tibet. Additionally, α-β quartz transition generates a measurable high seismic velocity zone, which provides a possibility of precisely constraining the temperature in the upper-middle continental crust. Our study also demonstrates that duration is a key factor to obtain credible experimental results.     

Cretaceous synfolding remagnetization components revealing tectonic rotation of the middle Yangtze fold belt

To reveal the deformation process of the middle Yangtze fold belt, we conducted a paleomagnetic study on Middle Triassic limestones and Middle to Late Jurassic sandstones from Wanzhou, Chongqing. Stepwise thermal and alternating field demagnetization were used to isolate the multi-component re-manent magnetizations. The Jurassic samples were overprinted by recent geomagnetic field, while three magnetization components were isolated from the Middle Triassic samples. A low temperature component (LTC) was isolated at temperatures below 200℃, an intermediate temperature component (ITC) at 200―360℃ and a high temperature component (HTC) at 400―460℃. The LTC is distributed around the present-day Earth magnetic field, probably a viscous component. Stepwise unfolding indi-cates that the maximum precision parameters of ITC and HTC components are achieved at 33±8% and 50±27% (with 95% confidence) unfolding, respectively. The best-clustered ITC mean direction, Dec = 11.2°, Inc = 45.2° (α₉₅ = 4.5°, N = 34), corresponding to a paleopole at 79.3°N, 219.5°E (d_p = 3.6°, d_m = 5.7°), is consistent with the Cretaceous reference direction of the South China Block (SCB). The best-clustered HTC mean direction (taking 70% unfolding), Dec = 24.2°, Inc =49.0° (α₉₅ = 3.6°, N = 23), corresponding to a paleopole at 69.2°N, 195.5°E (d_p =3.1°, d_m = 4.8°), suggests a clockwise rotation of 12.8°±3.5°. These synfolding remagnetization components clearly reveal that a clockwise rotation happened at the middle stage of folding, thus supporting that at least part of the variation in fold axis strikes is due to orocline rotation. Combined with published data, our analysis indicates that the Wan-zhou-Xiangxi segment of the middle Yangtze fold belt experienced oroclinal bending. Furthermore, a published post-folding component isolated from the Middle Triassic Puqi Formation suggests a 27.5°±5.8° clockwise rotation, confirming that at least 50% of the observed clockwise rotations in the eastern middle Yangtze fold belt can be attributed to oroclinal bending. The remagnetization data and geological evidence observed in the middle Yangtze fold belt suggest that collision between SCB and North China Block (NCB) probably lasted till the early period of Early Cretaceous.     

A novel advanced oxidation process――wet electro-catalytic oxidation for high concentrated organic wastewater treatment

A novel advanced oxidation process——wet electrocatalytic oxidation (WEO) was studied with p-nitrophenol as model pollutant and β-PbO2 electrode as the anode. Compared with the effect of the individual wet air oxidation (WAO) and electrochemical oxidation (EO), the effect of WEO showed syn- ergistic effect on COD removal under the conditions of temperature 160℃, C=1000 mg·L-1, PN2=0.50 MPa, PO2=0.9 MPa, current density = 3 mA·cm-2, Na2SO4 3 g·L-1. And the synergistic factor got the best value of 0.98 within 120 min after 180 min treatment. The synergistic factor was studied after 120 min treatment at 100℃, 120℃, 140℃ and 160℃, and the effect of 120℃ was the best with the value of 1.26. Possible mechanism for the synergistic effect was discussed based on the analysis of free-radical generation and intermediates detected by HPLC and GC/MS.     

Impact of urbanization on changes in temperature extremes in Beijing during 1978–2008

To quantify the impact of urbanization on changes in observed surface air temperature and extremes, a homogenized dataset of daily mean, maximum and minimum temperature （Trn, Trnax and Train） observations at 20 stations in Greater Beijing （GBJ） from 1978 to 2008 is analyzed. In contrast with previous studies, a cluster analysis is done to objectively classify observing stations into four categories （urbanized, suburban, rural and mountain）, which is checked with remote-sensing night-light images since the 1990s. At urbanized sites, there is an added warming trend in annual mean Tm representing an average of 10.9% （up to 18.4% or 0.12℃/decade at the most strongly influenced site） of overall warming. Corresponding contributions for Train are 12.7% （up to 20.8% or 0.19℃/decade） and 24% for diurnal temperature range DTR （up to 37.4% or 0.149℃/decade） over the last three dec- ades. Although it has not had a significant impact on daytime records （Tmax）, urbanization has enhanced the increasing （decreasing） trend of extremely warm （cold） nights by an average of 12.7% or 2.07 d/decade （29.0% or 5.06 d/decade） at the urbanized sites since the 1970s.     

近47年城市化发展对沈阳区域局地气候的影响研究

利用1959—2005年沈阳及周边郊区4县(康平、新民、法库、辽中)台站的气候观测资料,研究分析了沈阳城区、郊区气温、降水量、相对湿度、风速的变化趋势和特点。在此基础上,探讨了城市化发展对沈阳区域气候变化产生的影响。研究发现:1)近47年来,沈阳平均气温上升显著,其中冬季、春季增暖幅度最大,夏季最弱。同时,沈阳郊区增暖幅度略大于城区增暖幅度。2)沈阳年降水量、相对湿度、平均风速整体均呈下降趋势,降幅以平均风速最大,降水量最小。沈阳降水量的季节变化比较复杂,冬季降水量轻微增加。分析结果显示,沈阳城市化发展对区域局地气候产生了重要影响,尤其是近年来对郊区气温影响显著。另外,城市化进程对平均气温、风速的影响比其对相对湿度、降水量的影响更为显著、直接。     

近47年城市化发展对沈阳区域局地气候的影响研究

利用1959-2005年沈阳及周边郊区4县（康平、新民、法库、辽中）台站的气候观测资料,研究分析了沈阳城区、郊区气温、降水量、相对湿度、风速的变化趋势和特点。在此基础上,探讨了城市化发展对沈阳区域气候变化产生的影响。研究发现：1) 近47年来,沈阳平均气温上升显著,其中冬季、春季增暖幅度最大,夏季最弱。同时,沈阳郊区增暖幅度略大于城区增暖幅度。2) 沈阳年降水量、相对湿度、平均风速整体均呈下降趋势,降幅以平均风速最大,降水量最小。沈阳降水量的季节变化比较复杂,冬季降水量轻微增加。分析结果显示,沈阳城市化发展对区域局地气候产生了重要影响,尤其是近年来对郊区气温影响显著。另外,城市化进程对平均气温、风速的影响比其对相对湿度、降水量的影响更为显著、直接。     

Changes in precipitation and extreme precipitation in a warming environment in China

This study analyses the decadal changes in winter precipitation and extreme precipitation in a warming environment in China. The results show that, together with a trend of winter warming in China, winter precipitation and extreme precipitation in the region are also increasing. In addition, concurrent with the decadal warming shift that occurred in the mid-1980s, precipitation and extreme precipitation both increased significantly. Quantitative analysis shows that precipitation and extreme precipitation increased at rates of 9.7% and 22.6% per 1℃ of surface warming in China. This rate of precipitation increase is greater than the global mean, which indicates that precipitation in China is highly sensitive to climate warming and further highlights the importance of studying regional responses to climate warming. The fact that extreme precipitation is increasing at a higher rate than precipitation implies that winter precipitation in China will increasingly be of more extreme type in the context of global warming, which could partly explain why there have recently been a number of record-breaking extreme snowfall events in China.