首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
In this analysis, the weather research and forecasting model coupled with a single-layer urban canopy model is used to simulate the climatic impacts of urbanization in the Beijing–Tianjin–Hebei metropolitan area, which has experienced significant expansion in its urban areas. Two cases examining current landscapes and the sensitivity test of urban areas replaced by cropland have been carried out to explore the changes in the surface air and atmospheric boundary structure. The impact of urbanization on annual mean surface air temperature has been found to be more than 1 °C in urban areas, and the maximum difference is almost 2 °C. The change in near-surface level temperature is most pronounced in winter, but the area influenced by urbanization is slightly larger in summer. The annual mean water vapor mixing ratio and wind speed are both reduced in the urban area. The effect of urbanization can only heat the temperature inside the urban boundary layer, below 850 hPa. The modeling results also indicate that the underlying surface thermal forces induced by the “urban heat island” effect enhance vertical air movement and engenders a convergence zone over urban areas. The convergence at low level together with the moisture increases in the layer between 850 and 700 hPa triggered the increase of convective precipitation.  相似文献   

2.
With the surface air temperature (SAT) data at 37 stations on Central Yunnan Plateau (CYP) for 1961–2010 and the Defense Meteorological Satellite Program/Operational Linescan System (DMSP/OLS) nighttime light data, the temporal-spatial patterns of the SAT trends are detected using Sen’s Nonparametric Estimator of Slope approach and MK test, and the impact of urbanization on surface warming is analyzed by comparing the differences between the air temperature change trends of urban stations and their corresponding rural stations. Results indicated that annual mean air temperature showed a significant warming trend, which is equivalent to a rate of 0.17 °C/decade during the past 50 years. Seasonal mean air temperature presents a rising trend, and the trend was more significant in winter (0.31 °C/decade) than in other seasons. Annual/seasonal mean air temperature tends to increase in most areas, and higher warming trend appeared in urban areas, notably in Kunming city. The regional mean air temperature series was significantly impacted by urban warming, and the urbanization-induced warming contributed to approximately 32.3–62.9 % of the total regional warming during the past 50 years. Meantime, the urbanization-induced warming trend in winter and spring was more significant than that in summer and autumn. Since 1985, the urban heat island (UHI) intensity has gradually increased. And the urban temperatures always rise faster than rural temperatures on the CYP.  相似文献   

3.
Cave air temperature, carbon dioxide concentrations in the cave air and external air temperature were analysed at several locations in Postojna Cave over the course of six holiday periods in 2009–2011. The results show that a 1-day increase in visitor numbers from 200 to 3,500 raised the cave air temperature by a maximum of 0.5 °C. The air temperature increases are within the annual range of cave air temperature variations. A fivefold increase in visitor numbers resulted in a carbon dioxide concentration that was at least twice as high as normal. The carbon dioxide concentration increased from 450 to 1,750 ppm (December 2009–January 2010). After 10 days of peak period visits, both the CO2 concentration and the temperature returned almost to the pre-holiday values. The gradual increase in mean annual air temperature in the cave (2004–2010) is not related to the number of visitors but to outside climate conditions.  相似文献   

4.
The Beijing meteorological tower is located in an area of Beijing, China, which has developed from a suburban to an inner city setting over the past 30 years. The impacts of this urbanization process on both the vertical profile and diurnal cycles of air temperature are investigated using hourly data collected from a series of monitoring levels (up to 325 m high) on the Beijing meteorological tower since 1984. We find that the inter-decadal temperature has increased gradually, and that a more significant increase occurred during the 1980s and 1990s due to the effects of urbanization. A well-defined change in temperature stratification was also observed over this period. The height of the temperature inversion layer decreased from the 1980s to the 2000s. A well-defined nighttime temperature inversion developed below 50 m during the summer in the 1980s, but this near-surface inversion is not seen in data from the 1990s and 2000s. This change can be related to an increase in turbulent mixing caused by urban roughness and surface heat storage that disturbs the near-surface temperature inversion layer. In addition, the diurnal change in temperature in the city in summer shows a maximum increase from sunrise to the early afternoon, which is mainly caused by the nature variability and global warming in both the summer and winter. The urbanization mainly contributes to the temperature increase in the afternoon and nighttime. Moreover the urbanization dominates the increase in daily mean near-surface temperature.  相似文献   

5.
Chang-Soo Rim 《Climatic change》2009,97(3-4):483-514
The effects of climatic changes owing to urbanization, geographical and topographical conditions on FAO Penman–Monteith (FAO P–M) reference evapotranspiration (RET), and energy and aerodynamic terms of RET have been studied. In this study, 56 climatological stations including the Seoul metropolis in South Korea have been selected, and the area of study site was set at 314 km2. The climatological station is centrally located in the study area with a 10 km radius. The geographical and topographical characteristics of these sites were examined using GIS analysis. Land use status of the study area was also examined to estimate the extent of urbanization. The study results indicated that the variation of RET rate is closely related to urbanization in most climatological stations. The level of change in RET was higher in areas with higher urbanization rates. As topographical slope of study area increases, RET decreases. Average elevation of the study area also shows the negative correlation with RET. As the wet land area increases, RET decreases. When considering the effect of proximity of the observation station to sea, the closer the observation station is to the sea, the higher the RET. The study results showed that climatic change due to proximity of the observation station to sea had the greatest effect on RET.  相似文献   

6.
Investigating the characteristics of model-forecast errors using various statistical and object-oriented methods is necessary for providing useful guidance to end-users and model developers as well. To this end, the random and systematic errors (i.e., biases) of the 2-m temperature and 10-m wind predictions of the NCAR-AirDat weather research and forecasting (WRF)-based real-time four-dimensional data assimilation (RTFDDA) and forecasting system are analyzed. This system has been running operationally over a contiguous United States (CONUS) domain at a 4-km grid spacing with four forecast cycles daily from June 2009 to September 2010. In the result an exceptionally useful forecast dataset was generated and used for studying the error properties of the model forecasts, in terms of both a longer time period and a broader coverage of geographic regions than previously studied. Spatiotemporal characteristics of the errors are investigated based on the 24-h forecasts between June 2009 and April 2010, and the 72-h forecasts between May and September 2010. It was found that the biases of both wind and temperature forecasts vary greatly seasonally and diurnally, with dependency on the forecast length, station elevation, geographical location, and meteorological conditions. The temperature showed systematic cold biases during the daytime at all station elevations and warm biases during the nighttime above 1,000 m above sea level (ASL), while below 600 m ASL cold biases occurred during the nighttime. The forecasts of surface wind speed exhibited strong positive biases during the nighttime, while the negative biases were observed in the spring and summer afternoons. The surface wind speed was mostly over-predicted except for the stations located between 1,000 and 2,100 m ASL, for which negative biases were identified for most forecast cycles. The highest wind-speed errors were found over the high terrain and near sea-level stations. The wind-direction errors were relatively large at the high-terrain elevation in the Rocky and Appalachian mountain ranges and the western coastal areas and the error structure exhibited notable diurnal variability.  相似文献   

7.
Persistence in surface air temperature anomaly (SATA) time series over 1901–2010 observed at four cities: Nagpur, Pune, Mumbai and Delhi of India is examined using rescaled-range and predictability index. A gap of 40 years is observed in predictability maxima, which is linked with the short-range correlations. Seasonal analysis showed unpredictability of SATA during four seasons at Nagpur, during summers at Pune and Mumbai, and during monsoon and post-monsoon at Mumbai and Delhi. Significant change is observed after 1991 at Delhi, Nagpur and Mumbai with a respective increase of 1.7, 2.2 and 3.3 °C in surface air temperature (SAT) during 1901–2010. The spatial and temporal variations in the SAT in four cities are attributed to their geographic and climatic conditions. The results suggest the utility of the rescaled-range analysis and predictability index in exploring the changes in the climatic variables.  相似文献   

8.
The paper focuses on exceptionally hot summers (EHS) as a manifestation of contemporary climate warming. The study identifies EHS occurrences in Central and Eastern Europe and describes the characteristic features of the region’s thermal conditions. Average air temperatures in June, July and August were considered, as well as the number of days with maximum temperatures exceeding 25, 30 and 35 °C, and with a minimum temperature greater than >20 °C, as recorded at 59 weather stations in 1951–2010. Extremely hot summers are defined as having an average temperature equal to or greater than the long-term average plus 2 SD. A calendar of EHSs was compiled and their spatial extent identified. The region experienced 12 EHSs, which occurred in a given year at 5 % or more stations (1972, 1981, 1988, 1992, 1997, 1998, 1999, 2002, 2003, 2006, 2007 and 2010). The EHS frequency of occurrence was found to be clearly on an increase. Indeed, only one EHS occurred during the first 30 years, but these occurred five times during the last 10 years of the study period. Their geographical extent varied both in terms of location and size. EHSs were observed at 57 out of the total of 59 weather stations in the study (the exceptions were Pecora and Cluj). The average air temperature of EHSs tended to exceed the relevant long-term average by 2–4 °C. The summer of 2010 was among the hottest (temperature anomaly 5.5–6 °C) and spatially largest.  相似文献   

9.
Recent temperature projections for urban areas have only been able to reflect the expected change due to greenhouse-induced warming, with little attempt to predict urbanisation effects. This research examines temperature changes due to both global warming and urbanisation independently and applies them differentially to urban and rural areas over a sub-tropical city, Hong Kong. The effect of global warming on temperature is estimated by regressing IPCC data from eight Global Climate Models against the background temperature recorded at a rural climate station. Results suggest a mean background temperature increase of 0.67 °C by 2039. To model temperature changes for different degrees of urbanization, long-term temperature records along with a measureable urbanisation parameter, plot ratio surrounding different automatic weather stations (AWS) were used. Models representing daytime and nighttime respectively were developed, and a logarithmic relationship between the rate of temperature change and plot ratio (degree of urbanisation) is observed. Baseline air temperature patterns over Hong Kong for 2009 were derived from two ASTER thermal satellite images, for summer daytime and nighttime respectively. Dynamic raster modeling was employed to project temperatures to 2039 in 10-year intervals on a per-pixel basis according to the degree of urbanization predicted. Daytime and nighttime temperatures in the highly urbanized areas are expected to rise by ca. 2 °C by 2039. Validation by projecting observed temperature trends at AWS, gave low average RMS errors of 0.19 °C for daytime and 0.14 °C for nighttime, and suggests the reliability of the method.  相似文献   

10.
This paper addresses the contribution of urban land use change to near-surface air temperature during the summer extreme heat events of the early twenty-first century in the Beijing–Tianjin–Hebei metropolitan area. This study uses the Weather Research Forecasting model with a single urban canopy model and the newest actual urban cover datasets. The results show that urban land use characteristics that have evolved over the past ~20 years in the Beijing–Tianjin–Hebei metropolitan area have had a significant impact on the extreme temperatures occurring during extreme heat events. Simulations show that new urban development has caused an intensification and expansion of the areas experiencing extreme heat waves with an average increase in temperature of approximately 0.60 °C. This change is most obvious at night with an increase up to 0.95 °C, for which the total contribution of anthropogenic heat is 34 %. We also simulate the effects of geo-engineering strategies increasing the albedo of urban roofs, an effective way of reducing urban heat island, which can reduce the urban mean temperature by approximately 0.51 °C and counter approximately 80 % of the heat wave results from urban sprawl during the last 20 years.  相似文献   

11.
?rna Jama is the coldest section of cave within the Postojna Cave System. Mean annual air temperatures at the ?rna Jama 2 site are 5.6 °C (2015) and 5.7 °C (2016), and at the ?rna Jama 3 site 7.1 °C (2015) and 7.2 (2016), whereas the mean external air temperature was 10.3 °C (2015) and 10.0 °C (2016). In Lepe Jame, the passage most heavily visited by tourists, the mean cave-air temperature is 10.7 °C (2014–2017). ?rna Jama exhibits winter and summer temperature regimes. During warm periods (Tcave < Tout), it acts as a cold air trap, exchanging no air with the outside atmosphere. Under such conditions the cave-air temperature shows no short-term diurnal temperature oscillations. Cave-air temperature is significantly stable and affected only by elevation of the groundwater table, which is associated with precipitation. During cold periods (Tcave > Tout), ventilation takes place and dense, cold, outside air sinks into ?rna Jama because of the favourable cave entrance morphology. Recent ?rna Jama air temperature data (2014–2017) indicate a < 0.5 °C higher temperature than that recorded in historical data since 1933. ?rna Jama is the most appropriate place within the Postojna Cave System to study long-term climatic changes. There are hardly any tourist visits to the cave, and human impacts on the cave climate are essentially reduced.  相似文献   

12.
Due to the lack of knowledge on dynamics of the North Atlantic Oscillation (NAO) prior to the last millennium, synchronized records of air temperature and precipitation variability are needed to understand large-scale drivers of the hydroclimate. Here, we use completely synchronized paleolimnological proxy-based records of air temperature and effective precipitation from two Scandinavian lakes with ～2000-year sediment profiles. We show that the relationship between air temperature and precipitation (T/P ratio) is synchronous in both study sites throughout the records suggesting warm and dry conditions at ～300–1100 CE and cold and wet conditions at ～1200–1900 CE. Owing to the significantly increased air temperatures, the most recent T/P ratio has again turned positive. During the first millennium of the Common Era, the T/P mimics patterns in Southern Oscillation index, whereas the second millennium shows response to the NAO index but is also concurrent with solar irradiance shifts. Since our T/P reconstruction is mostly linked with the NAO, we propose the T/P ratio as an indicator of the NAO. Our results from the coherent records provide first-time knowledge on the long-term temperature-precipitation relationship in Northern Europe that increase understanding of the comprehensive hydroclimate system in the region and the NAO dynamics also further back in time.  相似文献   

13.
Climate Variability and Urbanization in Athens   总被引：2，自引：0，他引：2  
Summary  The effects of urbanization on the Athens National Observatory (NOA) long records are investigated, in the present study, examining the mean monthly maximum and minimum air temperature for the period 1925–1996, for NOA and the corresponding time series for Aliartos (ALI), a rural station located 70 km NW of Athens. The existing small urbanization effect in NOA before the second world war period increased after the war and up to about 1990, when the effect became stationary. The urbanization effect in NOA referred mainly to maximum temperature and to the warmer seasons of the year. It is attributed to the extensive building of Athens after the war around NOA site and up to the sea which increases the temperature of the sea breeze. The effect is also attributed to the rapid increase of the population and the number of motor vehicles mainly after 1970. Moreover the decreasing trend of precipitation during the period 1970–1990 may have contributed to the increase of maximum air temperature. The urbanization effect on maximum temperatures of NOA amounts about 2 °C in spring, summer and less in fall, while no urbanization effect is clear in winter. Received March 25, 1998 Revised October 7, 1998  相似文献   

14.
Spatial patterns of the standard deviation and skewness of daily and monthly mean summer temperature were studied with the climate model Institute of Numerical Mathematics Climate Model version 4 for three scenarios: simulation of the preindustrial climate, effect of quadrupling CO2 concentrations, and simulation of transient climate change for the period 1850–2100. In high skewness regions of the simulated preindustrial climate, hot periods exceeded the number expected for a normal distribution by a factor of 2–8. In the model in which CO2 concentrations were quadrupled, we found an increase in standard deviation and a northward shift of the area with positive skewness compared with the preindustrial scenario. The maximum increase in summer mean temperature was found in subtropical areas. The maximum increase in temperature averaged over the warmest 30 % of days was about 500 km to the north of the region of maximum increase of seasonal mean temperature, in the area where standard deviation was increased. The maximum increase in temperature averaged over the warmest 0.1 % of days was 500 km further north again, in an area of increased skewness. In the transient climate change simulation for 1850–2100, there was a noticeable increase in temperature of the warmest days exceeding the summer mean temperature in regions with increased skewness. In regions with decreased skewness, there was only a small increase or no rise at all in temperature for the warmest days under transient global warming.  相似文献   

15.
The atmospheric circulation and thermal conditions in the troposphere were analysed to identify the situations which are conductive to hail development in the North German Lowlands. They were established on the basis of the data obtained from the US National Center for Environmental Prediction/US National Center for Atmospheric Research Reanalysis database, and they included sea level pressure, 500 hPa geopotential height, the temperature at 850 and 500 hPa and HYSPLIT backward trajectories model. Daily information about hail occurrence in 16 selected stations was received from Deutscher Wetterdienst database and it covered the years 1951–2010. It was found that hail in the studied area was connected with large negative anomalies of the sea level pressure over Scandinavia and, consequently, the northwestern direction of air mass influx. In some cases, hail was associated with the northern influx, with strong negative anomalies of the temperature, and with positive anomalies of the temperature during the southern influx of air masses.  相似文献   

16.
Rapid urbanization has intensified summer heat waves in recent decades in Beijing, China. In this study, effectiveness of applying high-reflectance roofs on mitigating the warming effects caused by urban expansion and foehn wind was simulated for a record-breaking heat wave occurred in Beijing during July 13–15, 2002. Simulation experiments were performed using the Weather Research and Forecast (WRF version 3.0) model coupled with an urban canopy model. The modeled diurnal air temperatures were compared well with station observations in the city and the wind convergence caused by urban heat island (UHI) effect could be simulated clearly. By increasing urban roof albedo, the simulated UHI effect was reduced due to decreased net radiation, and the simulated wind convergence in the urban area was weakened. Using WRF3.0 model, the warming effects caused by urban expansion and foehn wind were quantified separately, and were compared with the cooling effect due to the increased roof albedo. Results illustrated that the foehn warming effect under the northwesterly wind contributed greatly to this heat wave event in Beijing, while contribution from urban expansion accompanied by anthropogenic heating was secondary, and was mostly evident at night. Increasing roof albedo could reduce air temperature both in the day and at night, and could more than offset the urban expansion effect. The combined warming caused by the urban expansion and the foehn wind could be potentially offset with high-reflectance roofs by 58.8 % or cooled by 1.4 °C in the early afternoon on July 14, 2002, the hottest day during the heat wave.  相似文献   

17.
Assessments of the impacts of climate change typically require information at scales of 10 km or less. Such a resolution in global climate simulations is unlikely for at least two decades. We have developed an alternative to explicit resolution that provides a framework for meeting the needs of climate change impact assessment much sooner. We have applied to a global climate model a physically based subgrid-scale treatment of the influence of orography on temperature, clouds, precipitation, and land surface hydrology. The treatment represents subgrid variations in surface elevation in terms of fractional area distributions of discrete elevation classes. For each class it calculates the height rise/descent of air parcels traveling through the grid cell, and applies the influence of the rise/descent to the temperature and humidity profiles of the elevation class. Cloud, radiative, and surface processes are calculated separately for each elevation class using the same physical parametrizations used by the model without the subgrid orography parametrization. The simulated climate fields for each elevation class can then be distributed in post-processing according to the spatial distribution of surface elevation within each grid cell. Parallel 10-year simulations with and without the subgrid treatment have been performed. The simulated temperature, precipitation and snow water are mapped to 2.5-minute (~5 km) resolution and compared with gridded analyses of station measurements. The simulation with the subgrid scheme produces a much more realistic distribution of snow water and significantly more realistic distributions of temperature and precipitation than the simulation without the subgrid scheme. Moreover, the 250-km grid cell means of most other fields are virtually unchanged by the subgrid scheme. This suggests that the tuning of the climate model without the subgrid scheme is also applicable to the model with the scheme.  相似文献   

18.
Using 51 meteorological stations in the arid region of northwest China in the mountain, oasis, and the desert areas obtained from 1960 to 2010, this paper conducted a comparative analysis for detecting temperature and precipitation changes in the diverse environments. In recent 50 years, temperature has increased at 0.325, 0.339, and 0.360 °C per decade in the mountain, oasis, and the desert areas, respectively; and also, precipitation has increased at 10.15, 6.29, and 0.87 mm per decade, but in which the increasing trend of precipitation in desert area was not significant. Before the 1990s, the increase in temperature was the fastest in the desert area, up to 0.214 °C per decade, but was the slowest in the mountain area, only 0.103 °C per decade. The temperature rising was faster after the 1990s, 0.606 °C per decade, in the oasis area was fastest, but was the slowest in the desert region with 0.402 °C per decade. The precipitation in each area was stable from 1960 to 1986, but an increase in the oasis and mountain area was larger from 1987 to 2010.  相似文献   

19.
Climate change signals in Saudi Arabia are investigated using the surface air temperature (SAT) data of 19 meteorological stations, well distributed across the country. Analyses are performed using cumulative sum, cumulative annual mean, and the Mann–Kendall rank statistical test for the period of 1978–2010. A notable change in SAT for the majority of stations is found around 1997. The results show a negative temperature trend (cooling) for all stations during the first period (1978–1997), followed by a positive trend (warming) in the second period (1998–2010) with reference to the entire period of analysis. The Mann–Kendall test confirms that there is no abrupt cooling at any station during the analysis period, reflecting the warming trend across the country. The warming trend is found to be 0.06 °C/year, while the cooling trend is 0.03 °C/year, which are statistically significant.  相似文献   

20.
Weather is an important factor for air quality. While there have been increasing attentions to long-term (monthly and seasonal) air pollution such as regional hazes from land-clearing fires during El Niño, the weather-air quality relationships are much less understood at long-term than short-term (daily and weekly) scales. This study is aimed to fill this gap through analyzing correlations between meteorological variables and air quality at various timescales. A regional correlation scale was defined to measure the longest time with significant correlations at a substantial large number of sites. The air quality index (API) and five meteorological variables during 2001–2012 at 40 eastern China sites were used. The results indicate that the API is correlated to precipitation negatively and air temperature positively across eastern China, and to wind, relative humidity and air pressure with spatially varied signs. The major areas with significant correlations vary with meteorological variables. The correlations are significant not only at short-term but also at long-term scales, and the important variables are different between the two types of scales. The concurrent regional correlation scales reach seasonal at p < 0.05 and monthly at p < 0.001 for wind speed and monthly at p < 0.01 for air temperature and relative humidity. Precipitation, which was found to be the most important variable for short-term air quality conditions, and air pressure are not important for long-term air quality. The lagged correlations are much smaller in magnitude than the concurrent correlations and their regional correction scales are at long term only for wind speed and relative humidity. It is concluded that wind speed should be considered as a primary predictor for statistical prediction of long-term air quality in a large region over eastern China. Relative humidity and temperature are also useful predictors but at less significant levels.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号