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1.
The accuracy of daily mean 2 meter air temperatures from five reanalyses are assessed against in-situ observations from Automatic Weather Stations in East Antarctica for 2005 to 2008.The five reanalyses all explain more than 70%of the average variance,and have annual root mean square errors(RMSE)between 3.4 and 6.9°C.The NOAA reanalyses,NCEP-1,NCEP-2and 20CRv2,have cool biases of 2.5,1.4 and 1.5°C,respectively.The ERA Interim and JCDAS reanalyses have warm biases of 1.7 and 2.0°C.All reanalyses generally perform better in the austral spring and worse in winter and autumn.They also show the best performance at an inland plateau site at 2800 m elevation,but are worst at Dome A,the summit of the East Antarctic ice sheet.In general,ERA Interim is superior to the other reanalyses,probably because of its 4D assimilation scheme.The three NOAA reanalyses perform worst;Their assimilation scheme is more constrained by limited observations and 20CRv2has less input data,assimilating only surface pressure observations.Despite deficiencies and limitations,the reanalyses are still powerful tools for climate studies in the Antarctic region.However,more in-situ observations are required,especially from the vast interior of Antarctica.  相似文献   

2.
Upper oceanographic and surface meteorological time-series observations from a moored buoy located at 9.98°N, 88°E in the south-western Bay of Bengal (BoB) were used to quantify variability in upper ocean, forced by a tropical cyclone (TC) Jal during November 2010. Before the passage of TC Jal, salinity and temperature profiles showed a typical BoB post-monsoon structure with relatively warm (30 °C) and low-saline (32.8 psu) waters in the upper 30- to 40-m layer, and relatively cooler and higher salinity (35 psu) waters below. After the passage of cyclone, an abrupt increase of 1 psu (decrease of 1 °C) in salinity (temperature) in the near-surface layers (up to 40-m depth) was observed from buoy measurements, which persisted up to 10–12 days during the relaxation stage of cyclone. Mixed layer heat budget analysis showed that vertical processes are the dominant contributors towards the observed cooling. The net surface heat flux and horizontal advection together contributed approximately 33 % of observed cooling, during TC Jal forced stage. Analysis showed the existence of strong inertial oscillation in the thermocline region and currents with periodicity of ～2.8 days. During the relaxation stage of the cyclone, upward movement of thermocline in near-inertial frequencies played significant role in mixed layer temperature and salinity variability, by much freer turbulent exchange between the mixed layer and thermocline.  相似文献   

3.
利用2008年中山站、Amundesen-Scott(SouthPole)站和Neumayer站为期一年的温度和臭氧探空数据,对AIRS第六版温度和臭氧垂直廓线产品在南极的精度进行了验证.结果表明,AIRS温度与探空温度总体上具有显著的一致性,其中对流层偏差最小(RMSe2℃),近地面温度由于受到下垫面影响偏差略大(RMSe～2℃),平流层偏差较大(2℃RMSe3℃),AIRS温度平均低于探空观测且受季节变化影响显著,秋冬季偏差整体上高于春夏季.AIRS臭氧反演精度在平流层(RMSe～25%)要优于对流层(RMSe～30%),RMSe最大值出现在UT-LS区域(可达40%)且在"臭氧洞"期间明显增大.AIRS产品精度在南极沿岸和内陆存在差异,由于南极地区探空资料较少且主要位于沿海,故在南极内陆地区进行探空观测对于提高卫星资料精度,改善该区域天气预报能力具有重大意义.  相似文献   

4.
The aim of this study was to quantify climate change impact on future blue water (BW) and green water (GW) resources as well as the associated uncertainties for 4 subbasins of the Beninese part of the Niger River Basin. The outputs of 3 regional climate models (HIRHAM5, RCSM, and RCA4) under 2 emission scenarios (RCP4.5 and RCP8.5) were downscaled for the historical period (1976–2005) and for the future (2021–2050) using the Statistical DownScaling Model (SDSM). Comparison of climate variables between these 2 periods suggests that rainfall will increase (1.7% to 23.4%) for HIRHAM5 and RCSM under both RCPs but shows mixed trends (?8.5% to 17.3%) for RCA4. Mean temperature will also increase up to 0.48 °C for HIRHAM5 and RCSM but decrease for RCA4 up to ?0.37 °C. Driven by the downscaled climate data, future BW and GW were evaluated with hydrological models validated with streamflow and soil moisture, respectively. The results indicate that GW will increase in all the 4 investigated subbasins, whereas BW will only increase in one subbasin. The overall uncertainty associated with the evaluation of the future BW and GW was quantified through the computation of the interquartile range of the total number of model realizations (combinations of regional climate models and selected hydrological models) for each subbasin. The results show larger uncertainty for the quantification of BW than GW. To cope with the projected decrease in BW that could adversely impact the livelihoods and food security of the local population, recommendations for the development of adequate adaptation strategies are briefly discussed.  相似文献   

5.
本文以拉格朗日观点分析北极涛动(Arctic Oscillation,AO),也被称为北半球环状模(Northern Hemisphere Annular Mode,NAM)的指数异常事件中北极近地面冷气团的活动路径,直接地表现出了异常事件中冷气团运动的优势路径,从而反映出AO/NAM对地面气温的直接调控作用.在正AO/NAM指数异常事件中,极区近地面冷气团活动轨迹以纬向环流为主,表现为环绕北半球中高纬地区的冷气团活动轨迹特征明显.而在负AO/NAM指数异常事件中,极区冷气团以反气旋式轨迹流出极区后,流入中纬度海洋上的低气压区,这种由极区向中纬度地区流动的经向运动轨迹特点显著.并且在指数下降的中后期出现两种强烈影响欧亚大陆的运动轨迹.正负事件中冷气团运动轨迹很好地解释了传统公认的AO/NAM对北半球不同地区冬季气温的影响.特别是对中国冬季气温的影响上,正AO/NAM指数异常事件中的中低层冷气团活动有利于南支槽加深,进而为南方地区冰冻雨雪天气提供了有利条件;而负事件中的极地近地面冷气团可直接影响东北地区,形成寒潮降温天气.  相似文献   

6.
This study was motivated by an interest in understanding the potential effects of climate change and glacier retreat on late summer water temperatures in alpine areas. Fieldwork was carried out between July and September 2007 at Place Lake, located below Place Glacier in the southern Coast Mountains of British Columbia. Place Lake has an area of 72 000 m2, a single inlet and outlet channel, and an approximate residence time of 4 days. Warming between the inlet and outlet of the lake ranged up to 3 °C and averaged 1.8 °C, which exceeds the amount of warming that occurred over the 1 km reach of Place Creek between the lake outlet and tree line. Over a 23‐day period, net radiation totalled about 210 MJ·m–2, with sensible heat flux adding another 56 MJ m‐2. The latent heat flux consumed about 8% of the surface heat input. The dominant heat sink was the net horizontal advection associated with lake inflow and outflow. Early in the study period, temperatures between the surface and 6‐m depth were dominantly at or above 4 °C and were generally neutral to thermally stable, whereas temperatures decreased with depth below 6 m and exhibited irregular sub‐diurnal variations. The maximum outflow temperature of almost 7 °C occurred in this period. We hypothesize that turbidity currents associated with cold, sediment‐laden glacier discharge formed an underflow and influenced temperatures in the deeper portion of the lake but did not mix with the upper layers. Later in the study period, the lake was dominantly well mixed with some near‐surface stability associated with nocturnal cooling. Further research is required to examine the combined effects of sediment concentrations and thermal processes on mixing in small proglacial lakes to make projections of the consequences of glacier retreat on alpine lake and stream temperatures. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

7.
High quality temperature measurements have been made to depths of 30 to 220 m at 42 sites in 62 observational hydrogeological wells in Alberta. The temperature profiles commonly show near-surface inversions with a minimum temperature at depths of 30 to 50 m. Thermal modelling suggests a surface temperature history with warming reaching 2°C over the past 30 to 60 years. Recent climate warming evident from the analysis of the air temperature data in the region seems to provide at least a partial explanation of the increased ground temperatures. A sudden increase of the surface ground temperature caused by land clearing may be the other explanation, although modelling of such a sudden increase can only explain the observed temperature-depth data if the onset of such warming is 20–30 years old, which is in disagreement with the history of land development in the studied area. The effect of near-surface inversions of the temperature profiles also has been observed in the forested areas. The above support the climate based effect. The superposition of the climatic effect and man-made activity effect upon the ground warming is a very complicated process calling for considerably more research.  相似文献   

8.
利用南极中山站至Dome A考察断面上3个自动气象站2005～2007年的观测资料和2008年夏季在中山站附近冰盖获取的湍流观测资料,应用空气动力学方法和涡动相关法计算分析了中山站至Dome A断面上近地层各种湍流参数(感热通量,潜热通量,湍流温度、湿度和速度尺度,地表粗糙度,大气稳定度及动量输送系数)的季节变化、日变...  相似文献   

9.
The two key mechanisms for biologically driven carbon sequestration in oceans are the biological pump(BP) and the microbial carbon pump(MCP); the latter is scarcely simulated and quantified in the China seas. In this study, we developed a coupled physical-ecosystem model with major MCP processes in the South China Sea(SCS). The model estimated a SCSaveraged MCP rate of 1.55 mg C m~(-2) d~(-1), with an MCP-to-BP ratio of 1:6.08 when considering the BP at a depth of 1000 m.Moreover, the ecosystem responses were projected in two representative global warming scenarios where the sea surface temperature increased by 2 and 4°C. The projection suggested a declined productivity associated with the increased near-surface stratification and decreased nutrient supply, which leads to a reduction in diatom biomass and consequently the suppression of the BP. However, the relative ratio of picophytoplankton increased, inducing a higher microbial activity and a nonlinear response of MCP to the increase in temperature. On average, the ratio of MCP-to-BP at a 1000-m depth increased to 1:5.95 with surface warming of 4°C, indicating the higher impact of MCP in future ocean carbon sequestration.  相似文献   

10.
Radiocarbon data for 11 stations and tritium data for 16 stations in the North Atlantic Ocean from 74°N to 3°N are presented. For radiocarbon, normal errors inΔ14C are± 4‰, and in tritium,± 0.09TU or± 3%, whichever is larger. There is a remarkable, but not simply linear, correlation between oceanic bomb transients in14C and3H. The deep convective mixing in the Greenland Sea is reflected in substantial bomb tracer penetration to all depths, with residence time for the deep, cold core water that seems to be 20 to 30 years. The outflow in the bottom layer southward over the sills of the Denmark Strait and Faroe Passage carries significant tritium concentration, at least to 40°N. Complicated, but coherent, profile structures in the subtropical Atlantic suggest effects of large-scale lateral advection. In particular, a pronounced minimum in both14C and3H might be associated with the Antarctic intermediate water.  相似文献   

11.
To aid rock art conservation, rock temperatures have been monitored at different depths and at low (30 min) and high (1 min) acquisition rates in a painted rock shelter in the uKhahlamba‐Drakensberg Park (South Africa). Preliminary data for winter (cold and dry) show that in that season cryoclasty is unlikely to occur (rare subzero thermal events and probable reduced moisture availability) and thermal shocks are improbable (highest measured ΔT/Δt < 2 °C min?1). High amplitude (about 30 °C) rock temperature cycles accompanied by reversals of the thermal gradient have been observed to occur almost daily and hint at the possibility of thermal stress fatigue. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

12.
Field experiments were carried out over a five year period with the aim of understanding contemporary weathering and erosional environments in the Sør Rondane Mountains, an Antarctic cold desert region. These include observations of (1) scaling from rockwalls, (2) disintegration of tuff blocks with or without saline solutions, and (3) abrasion of artificial walls by wind. Monitoring was also made of rock surface temperature and wind speed. Despite frequent temperature oscillations across 0°C, rock scaling due to frost action was generally very slow because of low moisture content in the rockwalls. Exposure to the cold, dry climate led to the rapid disintegration of porous tuff blocks including soluble salts like halite and thenardite. This indicates that rates of weathering are increased greatly with the accumulation of such salts in the bedrock. Although gypsum did not cause any visible damage over four years, its widespread occurrence in heavily damaged rocks demonstrates that increasing gypsum contents may also intensify rock breakdown. The snow-laden katabatic wind resulted in rapid wearing of the windward face of an asbestos board with the peak erosion at 30–40 cm above the ground. Nonetheless, the landforms expected from the unidirectional wind characteristics are by no means common features because of lack of abrasive materials, such as snow and sand particles. These experiments suggest that frost weathering and wind erosion are only locally effective where plenty of moisture or an abrasive material is available, whilst salt weathering and removal of the waste by wind play a major role in constructing erosional landforms over the mountains.  相似文献   

13.
Using CRU high resolution grid observational temperature and ERA40 reanalysis surface air temperature data during 1960–1999, we investigated the sensitivity of surface air temperature change to land use/cover types in China by subtracting the reanalysis from the observed surface air temperature (observation minus reanalysis, OMR). The results show that there is a stable and systemic impact of land use/cover types on surface air temperature. The surface warming of each land use/cover type reacted differently to global warming. The OMR trends of unused land (⩾0.17 °C/decade), mainly comprised by sandy land, Gobi and bare rock gravel land, are obviously larger than those of the other land use/cover types. The OMR over grassland, farmland and construction land shows a moderate decadal warmingabout 0.12°C/decade, 0.10°C/decade, 0.12°C/decade, respectively. Woodland areas do not show a significant warming trend (0.06°C/decade). The overall assessment indicates that the surface warming is larger for areas that are barren and anthropogenically developed. The better the vegetation cover, the smaller the OMR warming trend. Responses of surface air temperature to land use/cover types with similar physical and chemical properties and biological processes have no significant difference. The surface air temperature would not react significantly until the intensity of land cover changes reach a certain degree. Within the same land use/cover type, areas in eastern China with intensive human activities exhibit larger warming trend. The results provide observational evidence for modeling research on the impact of land use/cover change on regional climate. Thus, projecting further surface climate of China in regional scale should not only take greenhouse gas increase into account, but also consider the impact of land use/cover types and land cover change. Supported by National Basic Research Program of China (Grant No. 2005CB422006), National Natural Science Foundation of China (Grant Nos. 90202012, 40771206)  相似文献   

14.
Inferences on the lunar temperature regime are made from the inversion of gravity for density anomalies and the stress-state of the Moon's interior, and by comparing these results with flow laws and estimates of likely strain-rates.The nature of the spectrum of the lunar gravitational potential indicates that the density anomalies giving rise to the potential are mainly of near-surface origon. The average stress-differences in the lunar mantle required to support these density anomalies are of the order of a few tens of bars and have persisted for more than 3 · 109 years. If current flow laws for dry olivine can be extrapolated to the conditions of the lunar mantle, and the selenotherms based on electrical conductivity models are valid, the strain rates are too high to explain the preservation of the lateral near-surface density anomalies. We suggest that the present temperatures in the Moon are relatively low, of the order of 800°C or less, at a depth of about 300 km. This compares with 1100°C based on electrical conductivity models and is near the lower limit predicted by Keihm and Langseth (1977) from lunar heat-flow observations.  相似文献   

15.
Soil moisture plays a significant role in land-atmosphere interactions. Changing fractions of latent and sensible heat fluxes caused by soil moisture variations can affect near-surface air temperature, thus influencing the oasis's cooling effect in arid regions. In this study, the framework for the evaporative fraction (EF) dependence on soil moisture is used to analyse the impacts of soil moisture variation on near-surface air temperature and the oasis effect. The result showed that soil moisture's contribution rate to EF was significantly higher than that of EF to temperature. Under the interaction of temperature sensitivity to EF and EF to soil moisture, the ∂T/∂ϴ presented a similar tempo-spatial variation with both of the above. It was most significant in oasis areas during summer (−1.676), while it was weaker in plain desert areas during the autumn (−0.071). In the study region, the effect of soil moisture variation on air temperature can reach 0.018–0.242 K for different land-cover types in summer. The maximum variation of soil moisture in summer can alter air temperature by up to 0.386 K. The difference in temperature variability between the oasis and desert areas promoted the formation of the oasis effect. For different oasis, the multi-year average oasis cold effect index (OCI) ranged from −1.36 to −0.26 K. In comparison, the average summer OCI ranged from −1.38 to −0.29 K. The lower bound of the cooling effect of oasis ranged from −4.97 to −1.69 K. The analysis framework and results of this study will provide a new perspective for further research on the evolution process of the oasis effect and water–heat balance in arid areas.  相似文献   

16.
Fish habitat and aquatic life in rivers are highly dependent on water temperature. Therefore, it is important to understand andto be able to predict river water temperatures using models. Such models can increase our knowledge of river thermal regimes as well as provide tools for environmental impact assessments. In this study, artificial neural networks (ANNs) will be used to develop models for predicting both the mean and maximum daily water temperature. The study was conducted within Catamaran Brook, a small drainage basin tributary to the Miramichi River (New Brunswick, Canada). In total, eight ANN models were investigated using a variety of input parameters. Of these models, four predicted mean daily water temperature and four predicted maximum daily water temperature. The best model for mean daily temperature had eight input parameters: minimum, maximum and mean air temperatures of the current day and those of the preceding day, the day of year and the water level. This model had an overall root‐mean‐square error (RMSE) of 0·96 °C, a bias of 0·26 °C and a coefficient of determination R2 = 0·971. The model that best predicted maximum daily water temperature was similar to the first model but excluded mean daily air temperature. Good results were obtained for maximum water temperatures with an overall RMSE of 1·18 °C, a bias of 0·15 °C and R2 = 0·961. The results of ANN models were similar to and/or better than those observed from the literature. The advantages of artificial neural networks models in modelling river water temperature lie in their simplicity of use, their low data requirement and their good performance, as well as their flexibility in allowing many input and output parameters. Copyright © 2008 Crown in the right of Canada and John Wiley & Sons, Ltd.  相似文献   

17.
Water temperature behaviour in a small upland Exmoor catchment (the Black Ball Stream) has been studied over a 14-year period since January 1976. Results from continuous records revealed annual mean stream temperatures to have a coefficient of variation of less than 5 per cent, and values of 5,10 and 15°C to be equalled or exceeded 90,41.8 and 4 per cent of the time respectively. The annual regime of water temperature was relatively predictable but diel cycles of varying magnitude were superimposed on the seasonal march. A clear seasonal hysteresis was evident whereby diel range in spring exceeded that in autumn by typically more than 2°C. Trend analysis of monthly temperature time series highlighted the stability of the thermal regime in recent years, although investigation of air-water temperature relationships indicated that an increase in mean surface air temperature projected for southwest England by the Year 2050 would result in a rise of mean winter and summer stream temperatures by 1.6 and 1.3°C respectively. Analysis of streamflow effects on water temperature suggested that future indirect impacts of climatic change on thermal regime via changes in stream discharge are likely to be minor.  相似文献   

18.
There is increasing evidence that the global climate is changing as a result of anthropogenic activity. Short‐term mean, maximum, and minimum temperatures of the city Rize located at the Eastern Black Sea Coast of Turkey were analyzed to reveal trends, change points, significant warming (cooling) periods, and trend rates per year. An increasing trend of approximately 1.27°C/33 years (α = 0.001) in the annual mean temperatures is found during the period from 1975 to 2007. Two periods, averaging 13.78 and 14.66°C, respectively, were detected from fluctuation in the annual mean temperatures. The trend of the first period (1975–1993) is towards a cooler climate, whereas the trend of the second period (1994–2007) is towards a warmer climate. Summer, autumn and, particularly, the spring mean temperatures have tended to increase strongly, whereas the winter mean temperatures have increased slightly over the whole period. For the winter mean temperature, the trend rate indicates a slight increase, which is insignificant. Maximum temperatures have dramatically increased with 1.61°C (α = 0.001) over the last 33 years. However, annual minimum temperatures have increased by 0.99°C (α = 0.01) over the same period.  相似文献   

19.
14C specific activities in the western Atlantic show aging of about 160 years between 42°N and 30°S for southward-moving North Atlantic Deep Water. Most of the aging occurs in the North Atlantic, with a small increase in14C level for abyssal water near the equator.The northward-flowing Antarctic Bottom Water component ages about 80 years between 50°S and the equator. The rate of Atlantic bottom water formation is estimated at 18 Sverdrups; the rate of flow for northward-moving Antarctic Bottom Water at about 6 Sverdrups.  相似文献   

20.
数字高程模型(DEM)是南极冰盖变化研究的基础,由于现场实测数据的稀缺,卫星测高数据是南极地区构建DEM的'主要数据来源.CryoSat-2是新一代用于极地冰盖、海冰监测的测高卫星,本文利用2012-12-2015-01两个完整周期的CryoSat-2测高数据建立一个新的南极冰盖DEM.坡度是影响卫星测高精度的重要因素之一,利用改进的重定位方法对CryoSat-2数据进行坡度改正.插值方法是影响DEM精度的重要因素,通过对几种常用插值方法的比较,最后选用克里金插值方法对测高数据进行插值,建立了1km分辨率的南极DEM.在88°S以南的CryoSat-2数据空白区,利用南极数字数据库(ADD)的等高线数据对DEM进行填补,建立了全南极冰盖DEM.利用ICESat卫星测高数据、IceBridge航空测高数据以及GPS地面实测数据对新建立的CryoSat-2 DEM进行精度验证,并与Bamber 1 km DEM、ICESat DEM、RAMPv2 DEM以及JLB97 DEM等四种国际上常用的南极DEM进行比较.结果表明:新建立的CryoSat-2 DEM的整体精度约为0.730±8.398 m;在冰弯顶部区域,DEM精度优于1 m;在冰架上,DEM精度约为4 m;在内陆冰盖大部分地区,DEM精度优于10 m;在地形复杂的山区和沿海边缘地区,DEM误差超过150 m.  相似文献   

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