COOLING RATES, SKY VIEW FACTORS AND THE DEVELOPMENT OF INTRA-URBAN AIR TEMPERATURE DIFFERENCES

Intra‐urban cooling rates were monitored for a year in the centre of Göteborg on the Swedish west coast. Five sites with different building geometry ‐ from dense canyon to open space ‐ within a radius of 300 m were analysed. Results showed two modes of cooling during the night. In the first mode, the cooling was site‐dependent ‐the open space cooled the most and the dense canyon the least. In the second mode, which began about 3–4 hours after sunset, all sites cooled at the same rate. Our hypothesis is that in the early part of the evening both radiative divergence and sensible heat dominate the cooling. However, as the evening progresses, a spatially homogeneous inversion is established which controls the radiative cooling, making the cooling independent of both surface geometry and surface type. From April to November the sites cooled rapidly around sunset and the cooling slowly decreased during the rest of the night. However, between December and March, the cooling was less intense, with an almost constant rate during the entire night. It has been suggested that this might be the result of the draining of stored solar heat during the summer and a continuous flux of anthropogenic heating during the winter.     

Urban forest loss using a GIS-based approach and instruments for integrated urban planning:A case study of Jo(a)o Pessoa,Brazil

Urban forests play an important role in the thermal comfort and overall life of local populations in large-and medium-sized cities.This study analyzes urban forest loss and maps land use and land cover (LULC) changes between 1991 and 2018 by evaluating the use of urban planning instruments for the mitigation of urban forest loss in Jo～o Pessoa,Brazil.For this purpose,satellite-derived LULC images from 1991,2006,2010 and 2018 and data on urban forest loss areas obtained using the Google Earth Engine were used.In addi-tion,this paper also discusses the instruments used for integrated urban planning,which are(a) the legal sector,responsibility and nature;(b) the urban expansion process;and (c) the elements of urban infrastructure.The results show a clear shift in land use in the study area.The major changes in LULC classes occurred in urban areas and herbaceous vegetation,while the greatest loss was in arboreal/shrub vegetation.Thus,an increase in the pressure to occupy zones intended for environmental preservation could be estimated.Our results showed similar accuracies with other studies and more spatial details.The characteristics of the patterns,traces,and hotspots of urban expansion and forest cover loss were explored.We highlighted the potential use of this proposed framework to be applied and validated in other parts of the world to help better understand and quantify various aspects of ur-ban-related problems such as urban forest loss mapping using instruments for integrated urban planning and low-cost approaches.     

Late Holocene in central Brazil: vegetation changes and humidity variability in a tropical wetland

The Pandeiros wetland is a high biodiversity ecosystem located within a semiarid region of the Cerrado biome, a neotropical savanna. This large wetland is of key importance for ecological and hydrological balance in central Brazil and for the conservation of the Cerrado fauna and flora. In this study, we present the first palaeoecological investigation of the Pandeiros wetland based on pollen analysis of a palm swamp sediment core encompassing the Late Holocene. Our results show that the wetland was subject to multicentennial-scale oscillations in water availability during the Late Holocene; in particular, higher local humidity was documented between 4100 and 3100 cal a bp and from 2600 to 1000 cal a bp , and two events of drier local conditions occurred at approximately 2900 and 900 cal a bp. Our results also indicate a general decreasing trend in arboreal density in the Pandeiros River Basin from the beginning of the Late Holocene to the present, with the greatest expansion of dry forest occurring between 3600 and 3100 cal a bp.     

Climate variability in West Greenland during the past 1500 years: evidence from a high‐resolution marine palynological record from Disko Bay

Ribeiro, S., Moros, M., Ellegaard, M. & Kuijpers, A. 2012 (January): Climate variability in West Greenland during the past 1500 years: evidence from a high‐resolution marine palynological record from Disko Bay. Boreas, Vol. 41, pp. 68–83. 10.1111/j.1502‐3885.2011.00216.x. ISSN 0300‐9483. Here we document late‐Holocene climate variability in West Greenland as inferred from a marine sediment record from the outer Disko Bay. Organic‐walled dinoflagellate cysts and other palynomorphs were used to reconstruct environmental changes in the area through the last c. 1500 years at 30–40 years resolution. Sea ice cover and primary productivity were identified as the two main factors driving dinoflagellate cyst community changes through time. Our data provide evidence for an opposite climate trend in West Greenland relative to the NE Atlantic region from c. AD 500 to 1050. For the same period, sea‐surface temperatures in Disko Bay are out‐of‐phase with Greenland ice‐core reconstructed temperatures and marine proxy data from South and East Greenland. This is probably governed by an NAO‐type pattern, which results in warmer sea‐surface conditions with less extensive sea ice in the area for the later part of the Dark Ages cold period (c. AD 500 to 750) and cooler conditions with extensive sea ice inferred for the first part of the Medieval Climate Anomaly (MCA) (c. AD 750 to 1050). After c. AD 1050, the marine climate in Disko Bay becomes in‐phase with trends described for the NE Atlantic, reflected in the warmer interval for the remainder of the MCA (c. AD 1050–1250), followed by cooling towards the onset of the Little Ice Age at c. AD 1400. The inferred scenario of climate deterioration and extensive sea ice is concomitant with the collapse of the Norse Western Settlement in Greenland at c. AD 1350.     

基于多尺度数字地形定量分析的月球线性构造自动提取研究

月球表面构造对于理解和重建月球地质构造演化具有重要意义,月岭、月溪等线性构造的形态及分布特征与月球内动力构造运动密切相关。极为有限的样品和难度极高的野外勘察使得遥感成为行星科学研究的最主要手段。中国、美国、日本、印度等国先后发射的多颗新型探月卫星获取了大量高质量数据,尤其是高分辨率的数字地形数据(DTM,Digital Terrain Model)。高分辨率的DTM为月球表面构造特征的自动提取带来了新的机遇与挑战。文中利用多种分辨率的DTM数据,基于多尺度数字地形定量分析方法,识别和提取月球表面的线性构造。使用的地形数据包括500 m分辨率“嫦娥一号”激光高度计数据,100 m分辨率LRO-WAC广角相机数据,60 m分辨率的LRO-LOLA激光测距仪数据以及分辨率高达5 m的LRO-NAC窄视角相机数据。文中使用地形曲率来识别月溪月岭等线性构造,并利用不同滑动窗口大小和阈值进行线性构造的自动提取。对研究区试验结果的定量分析表明,文中提出的基于地形曲率的月表线性构造自动提取方法是有效且可行的,其结果可为月球表面线性构造解译提供重要参考,提高构造解译时效性和精度。     

Modélisation de l'incertitude sur les séquences futures de débits en rivière

Résumé

Le problème de la gestion du risque en ressources hydriques, tout comme celui de la gestion de réservoirs, est un problème de décision sous incertitudes, dont la qualité des solutions est extrêmement sensible à la façon dont la stochasticité des apports est prise en compte. Cet article propose une méthode pour modéliser l'incertitude sur les apports à court terme en fonction de la période de l'année. Pour cela, un modèle paramétrique markovien à temps continu, basé sur le processus de Poisson filtré, est construit et estimé grâce à des observations régulièrement espacées dans le temps puis validé sur trois stations hydrométriques situées au Québec (Canada). Les points étudiés sont sa capacité à représenter correctement les transitions de débits et ses performances en tant que prédicteur de la valeur à venir du débit. Ce dernier aspect est comparé à celui du modèle ARMA saisonnier. Les résultats montrent un bon comportement du modèle sur chacun de ces deux points.     

Surface wetness and mire development during the late Holocene in central Sweden

Andersson, S. & Schoning, K. 2010: Surface wetness and mire development during the late Holocene in central Sweden. Boreas, Vol. 39, pp. 749–760. 10.1111/j.1502‐3885.2010.00157.x. ISSN 0300‐9483. Late Holocene mire development and surface wetness changes have been studied in a small mixed mire located in central Sweden. Today the mire is characterized by a mainly ombrotrophic centre dominated by Sphagnum mosses, with Carex content increasing towards the more minerotrophic mire margins. Two peat sequences extracted from the central ombrotrophic part were investigated for stratigraphy, humification, testate amoebae analysis, C/N ratio and δ¹³C and δ¹⁵N stable isotopes. Three main stages of mire development are identified, with the first stage, between c. 4200 and 2600 cal. yr BP, characterized by water‐logged conditions, suggesting a minerotrophic fen stage. The second stage, between c. 2600 and 1000 cal. yr BP, is characterized by more ombrotrophic conditions and Sphagnum‐dominated vegetation. The onset of the prominent change at c. 2600 cal. yr BP could have been initiated by climate change coincident with a change in solar activity. The last stage, between c. 1000 and 50 cal. yr BP, is dominated by more ombrotrophic conditions, suggesting increased precipitation. This study shows that the response of hydrological proxies in a mixed mire during its development towards more ombrotrophic conditions might result in conflicting results, a finding that needs to be considered in palaeoenvironmental reconstructions from mires that change between ombrotrophic and minerotrophic settings.