scholarly journals The urban heat budget derived from satellite data

2003 ◽  
Vol 58 (2) ◽  
pp. 99-111 ◽  
Author(s):  
E. Parlow
Keyword(s):  
Satellite Data ◽  
Urban Areas ◽  
Heat Budget ◽  
Numerical Models ◽  
Heat Fluxes ◽  
Landsat Tm ◽  
Net Radiation ◽  
Urban Climatology ◽  
Budget Analysis ◽  
Urban Heat

Abstract. The study of the interactions between urban surfaces and the urban boundary layer plays an important role in urban climatology, especially seen against the background of increasing urbanisation in most parts of the world. Measurements of radiation and heat fluxes suffer from the extreme heterogeneity of the urban landscape. It is therefore difficult to get accurate and representative measurements. To bridge the gap between accurate point measurements and their spatial representation, satellite data from Landsat-TM are used. Methods and results of the investigation of radiation properties, net radiation and heat fluxes of urban areas in the Basel Region, NW-Switzerland are presented. In addition to field measurements, satellite data from Landsat-TM were linked to numerical models to compute net radiation and heat fluxes of the whole region. By integrating the normalized difference Vegetation index (NDVI) from multi-spectral satellite data, storage heat fluxes could be estimated with high accuracy. The next step was to compute latent and sensible heat fluxes by using a Bowen-ratio approach attributed to a land use Classification. Of interest is the Observation that the idea of an «Urban Heat Island» (UHI) has to be defined very carefully. Very often an «Urban Cooling Island» may be found during daytime and under clear sky conditions. This feature could be explained using the results of the satellite based radiation and heat budget analysis.

scholarly journals Energetics of Urban Canopies: A Meteorological Perspective

J ◽  
2021 ◽  
Vol 4 (4) ◽  
pp. 645-663
Author(s):  
Edson Marciotto ◽  
Marcos Vinicius Bueno de de Morais
Keyword(s):  
Boundary Layer ◽  
Urban Heat Island ◽  
Urban Areas ◽  
Numerical Models ◽  
Urban Canopy ◽  
Urban Heat Island Intensity ◽  
Heat Island ◽  
Local Flow ◽  
Urban Climatology ◽  
Urban Heat

The urban climatology consists not only of the urban canopy temperature but also of wind regime and boundary layer evolution among other secondary variables. The energetic input and response of urbanized areas is rather different to rural or forest areas. In this paper, we outline the physical characteristics of the urban canopy that make its energy balance depart from that of vegetated areas and change local climatology. Among the several canopy characteristics, we focus on the aspect ratio h/d and its effects. The literature and methods of retrieving meteorological quantities in urban areas are reviewed and a number of physical analyzes from conceptual or numerical models are presented. In particular, the existence of a maximum value for the urban heat island intensity is discussed comprehensively. Changes in the local flow and boundary layer evolution due to urbanization are also discussed. The presence of vegetation and water bodies in urban areas are reviewed. The main conclusions are as follows: for increasing h/d, the urban heat island intensity is likely to attain a peak around h/d≈4 and decrease for h/d>4; the temperature at the pedestrian level follows similar behavior; the urban boundary layer grows slowly, which in combination with low wind, can worsen pollution dispersion.

scholarly journals Characterization of the subsurface urban heat island and its sources in the Milan city area, Italy

2021 ◽  
Author(s):  
Alberto Previati ◽  
Giovanni B. Crosta
Keyword(s):  
Urban Heat Island ◽  
Urban Areas ◽  
Heat Fluxes ◽  
Shallow Aquifer ◽  
Heat Island ◽  
Groundwater Temperature ◽  
City Area ◽  
Groundwater Environment ◽  
Urban Heat ◽  
The Impact

AbstractUrban areas are major contributors to the alteration of the local atmospheric and groundwater environment. The impact of such changes on the groundwater thermal regime is documented worldwide by elevated groundwater temperature in city centers with respect to the surrounding rural areas. This study investigates the subsurface urban heat island (SUHI) in the aquifers beneath the Milan city area in northern Italy, and assesses the natural and anthropogenic controls on groundwater temperatures within the urban area by analyzing groundwater head and temperature records acquired in the 2016–2020 period. This analysis demonstrates the occurrence of a SUHI with up to 3 °C intensity and reveals a correlation between the density of building/subsurface infrastructures and the mean annual groundwater temperature. Vertical heat fluxes to the aquifer are strongly related to the depth of the groundwater and the density of surface structures and infrastructures. The heat accumulation in the subsurface is reflected by a constant groundwater warming trend between +0.1 and + 0.4 °C/year that leads to a gain of 25 MJ/m2 of thermal energy per year in the shallow aquifer inside the SUHI area. Future monitoring of groundwater temperatures, combined with numerical modeling of coupled groundwater flow and heat transport, will be essential to reveal what this trend is controlled by and to make predictions on the lateral and vertical extent of the groundwater SUHI in the study area.

Intraseasonal SST Variability and Air–Sea Interaction over the Kuroshio Extension Region during Boreal Summer

2012 ◽  
Vol 25 (5) ◽  
pp. 1619-1634 ◽  
Author(s):  
Lu Wang ◽  
Tim Li ◽  
Tianjun Zhou
Keyword(s):  
Heat Budget ◽  
Kuroshio Extension ◽  
Sensible Heat Flux ◽  
Heat Fluxes ◽  
Shortwave Radiation ◽  
Boreal Summer ◽  
Budget Analysis ◽  
Anomalous Anticyclone ◽  
Sst Warming ◽  
The Kuroshio

The structure and evolution characteristics of intraseasonal (20–100 day) variations of sea surface temperature (SST) and associated atmospheric and oceanic circulations over the Kuroshio Extension (KE) region during boreal summer are investigated, using satellite-based daily SST, observed precipitation data, and reanalysis data. The intraseasonal SST warming in the KE region is associated with an anomalous anticyclone in the overlying atmosphere, reduced precipitation, and northward and downward currents in the upper ocean. The corresponding atmospheric and oceanic fields during the SST cooling phase exhibit a mirror image with an opposite sign. A mixed layer heat budget analysis shows that the intraseasonal SST warming is primarily attributed to anomalous shortwave radiation and latent heat fluxes at the surface. The anomalous sensible heat flux and oceanic advection also have contributions, but with a much smaller magnitude. The SST warming caused by the atmospheric forcing further exerts a significant feedback to the atmosphere through triggering the atmospheric convective instability and precipitation anomalies. The so-induced heating leads to quick setup of a baroclinic response, followed by a baroclinic-to-barotropic transition. As a result, the atmospheric circulation changes from an anomalous anticyclone to an anomalous cyclone. This two-way interaction scenario suggests that the origin of the atmospheric intraseasonal oscillation over the KE region may partly arise from the local atmosphere–ocean interaction.

scholarly journals Asymmetric Response of the Equatorial Pacific SST to Climate Warming and Cooling

2017 ◽  
Vol 30 (18) ◽  
pp. 7255-7270 ◽  
Author(s):  
Fukai Liu ◽  
Yiyong Luo ◽  
Jian Lu ◽  
Oluwayemi Garuba ◽  
Xiuquan Wan
Keyword(s):  
Heat Flux ◽  
Heat Budget ◽  
Dominant Role ◽  
Surface Heat ◽  
Equatorial Pacific ◽  
Heat Fluxes ◽  
Shortwave Radiation ◽  
Asymmetric Structure ◽  
Linear Component ◽  
Budget Analysis

Abstract The response of the equatorial Pacific Ocean to heat fluxes of equal amplitude but opposite sign is investigated using the Community Earth System Model (CESM). Results show a strong asymmetry in SST changes. In the eastern equatorial Pacific (EEP), the warming responding to the positive forcing exceeds the cooling response to the negative forcing, whereas in the western equatorial Pacific (WEP) it is the other way around and the cooling surpasses the warming. This leads to a zonal dipole asymmetric structure, with positive values in the east and negative values in the west. A surface heat budget analysis suggests that the SST asymmetry mainly results from the oceanic horizontal advection and vertical entrainment, with both of their linear and nonlinear components playing a role. For the linear component, its change appears to be more significant over the EEP (WEP) in the positive (negative) forcing scenario, favoring the seesaw pattern of the SST asymmetry. For the nonlinear component, its change acts to warm (cool) the EEP (WEP) in both scenarios, also favorable for the development of the SST asymmetry. Additional experiments with a slab ocean confirm the dominant role of ocean dynamical processes for this SST asymmetry. The net surface heat flux, in contrast, works to reduce the SST asymmetry through its shortwave radiation and latent heat flux components, with the former being related to the nonlinear relationship between SST and convection, and the latter being attributable to Newtonian damping and air–sea stability effects. The suppressing effect of shortwave radiation on SST asymmetry is further verified by partially coupled overriding experiments.

scholarly journals An Intermodel Approach to Identify the Source of Excessive Equatorial Pacific Cold Tongue in CMIP5 Models and Uncertainty in Observational Datasets

2015 ◽  
Vol 28 (19) ◽  
pp. 7630-7640 ◽  
Author(s):  
Gen Li ◽  
Yan Du ◽  
Haiming Xu ◽  
Baohua Ren
Keyword(s):  
Heat Flux ◽  
Heat Budget ◽  
Equatorial Pacific ◽  
Heat Fluxes ◽  
Specific Humidity ◽  
Cmip5 Models ◽  
Climate Projections ◽  
Cold Tongue ◽  
Budget Analysis ◽  
Dynamic Cooling

Abstract An excessive cold tongue error in the equatorial Pacific has prevailed in several generations of climate models. However, the causes of this problem remain a mystery, partly owing to uncertainty and/or a lack of observational datasets. Based on the multimodel ensemble from phase 5 of the Coupled Model Intercomparison Project (CMIP5), this study introduces a novel intermodel approach to identify the bias source by going beyond comparison with observational datasets. Intermodel statistics show that the excessive cold tongue bias could be traced back to a too strong oceanic dynamic cooling linked to a too shallow thermocline along the equatorial Pacific. A heat budget analysis suggests that the excessive oceanic dynamic cooling is balanced by the surface latent heat flux (LHF) adjustment. This is consistent with a variety of oceanic and atmospheric observations but at odds with the popular objectively analyzed air–sea heat fluxes (OAFlux) products. Further analyses suggest an alarming overestimation of OAFlux net surface heat flux (Qnet) into the tropical Pacific, mainly ascribed to observational uncertainly in air specific humidity. Implications for intermodel statistics in assessing model processes, validating observational data, and regulating future climate projections are discussed.

scholarly journals Effects of Synoptic-Scale Wind under the Typical Summer Pressure Pattern on the Mesoscale High-Temperature Events in the Osaka and Kyoto Urban Areas by the WRF Model

2013 ◽  
Vol 52 (8) ◽  
pp. 1764-1778 ◽  
Author(s):  
Yuya Takane ◽  
Yukitaka Ohashi ◽  
Hiroyuki Kusaka ◽  
Yoshinori Shigeta ◽  
Yukihiro Kikegawa
Keyword(s):  
Heat Budget ◽  
Wrf Model ◽  
Heat Fluxes ◽  
Heat Diffusion ◽  
Formation Mechanisms ◽  
Sensible Heat ◽  
Synoptic Scale ◽  
Column Temperature ◽  
Budget Analysis ◽  
Typical Summer

AbstractThe actual conditions of mesoscale summer high temperatures (HTs) recorded in the Osaka–Kyoto urban area of Japan were investigated using an observation network. The daytime temperatures observed on 10 HT events in this area were the highest in the southern area of Kyoto [area with no Automated Meteorological Data Acquisition System (AMeDAS) observation sites]. To quantitatively evaluate the formation mechanisms of HT events, a heat budget analysis on an atmospheric column was conducted using the Weather Research and Forecasting (WRF) model. The results showed that over the HT area the daytime column temperature increased as a result of sensible-heat diffusion generated from the urban surface at the contribution rate of 54% and as a result of the sensible-heat advection and diffusion supplied from the sides and at the top of the column at the rate of 46% of all sensible heat supplied. To clarify previously unreported effects of synoptic-scale winds under typical summer pressure patterns on the HT events, a sensitivity experiment with no surface heat fluxes, backward trajectory analysis, and Euler forward tracer analysis was performed. These analyses yielded the following findings: 1) sensible heat at the synoptic scale and/or mesoscale was transported from the tropics by circulation patterns along the edge of the Pacific high as well as from tropical cyclones that were present in the vicinity of Japan and 2) airflow over the Kii Mountains also contributes to the HT events.

scholarly journals Turbulent Heat Fluxes during an Extreme Lake-Effect Snow Event

2017 ◽  
Vol 18 (12) ◽  
pp. 3145-3163 ◽  
Author(s):  
Ayumi Fujisaki-Manome ◽  
Lindsay E. Fitzpatrick ◽  
Andrew D. Gronewold ◽  
Eric J. Anderson ◽  
Brent M. Lofgren ◽  
...  
Keyword(s):  
Numerical Models ◽  
Atmospheric Model ◽  
Ocean Model ◽  
Heat Fluxes ◽  
Turbulent Heat ◽  
Surface Boundary ◽  
Budget Analysis ◽  
Lake Effect ◽  
Turbulent Heat Fluxes ◽  
Flux Measurements

Abstract Proper modeling of the turbulent heat fluxes over lakes is critical for accurate predictions of lake-effect snowfall (LES). However, model evaluation of such a process has not been possible because of the lack of direct flux measurements over lakes. The authors conducted the first-ever comparison of the turbulent latent and sensible heat fluxes between state-of-the-art numerical models and direct flux measurements over Lake Erie, focusing on a record LES event in southwest New York in November 2014. The model suite consisted of numerical models that were operationally and experimentally used to provide nowcasts and forecasts of weather and lake conditions. The models captured the rise of the observed turbulent heat fluxes, while the peak values varied significantly. This variation resulted in an increased spread of simulated lake temperature and cumulative evaporation as the representation of the model uncertainty. The water budget analysis of the atmospheric model results showed that the majority of the moisture during this event came from lake evaporation rather than a larger synoptic system. The unstructured-grid Finite-Volume Community Ocean Model (FVCOM) simulations, especially those using the Coupled Ocean–Atmosphere Response Experiment (COARE)-Met Flux algorithm, presented better agreement with the observed fluxes likely due to the model’s capability in representing the detailed spatial patterns of the turbulent heat fluxes and the COARE algorithm’s more realistic treatment of the surface boundary layer than those in the other models.

scholarly journals Evaluating the Urban Canopy Scheme TERRA_URB in the COSMO Model for Selected European Cities

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 237 ◽  
Author(s):  
Valeria Garbero ◽  
Massimo Milelli ◽  
Edoardo Bucchignani ◽  
Paola Mercogliano ◽  
Mikhail Varentsov ◽  
...  
Keyword(s):  
Urban Areas ◽  
Morphological Characteristics ◽  
Urban Canopy ◽  
Anthropogenic Heat ◽  
Climate Modelling ◽  
Model Framework ◽  
European Cities ◽  
Cosmo Model ◽  
Anthropogenic Heat Flux ◽  
Urban Heat

The increase in built surfaces constitutes the main reason for the formation of the Urban Heat Island (UHI), that is a metropolitan area significantly warmer than its surrounding rural areas. The urban heat islands and other urban-induced climate feedbacks may amplify heat stress and urban flooding under climate change and therefore to predict them correctly has become essential. Currently in the COSMO model, cities are represented by natural land surfaces with an increased surface roughness length and a reduced vegetation cover, but this approach is unable to correctly reproduce the UHI effect. By increasing the model resolution, a representation of the main physical processes that characterize the urban local meteorology should be addressed, in order to better forecast temperature, moisture and precipitation in urban environments. Within the COSMO Consortium a bulk parameterization scheme (TERRA_URB or TU) has been developed. It parametrizes the effects of buildings, streets and other man-made impervious surfaces on energy, moist and momentum exchanges between the surface and atmosphere, and additionally accounts for the anthropogenic heat flux as a heat source from the surface to the atmosphere. TU implements an impervious water-storage parameterization, and the Semi-empirical Urban canopy parametrization (SURY) that translates 3D urban canopy into bulk parameters. This paper presents evaluation results of the TU scheme in high-resolution simulations with a recent COSMO model version for selected European cities, namely Turin, Naples and Moscow. The key conclusion of the work is that the TU scheme in the COSMO model reasonably reproduces UHI effect and improves air temperature forecasts for all the investigated urban areas, despite each city has very different morphological characteristics. Our results highlight potential benefits of a new turbulence scheme and the representation of skin-layer temperature (for vegetation) in the model performance. Our model framework provides perspectives for enhancing urban climate modelling, although further investigations in improving model parametrizations, calibration and the use of more realistic urban canopy parameters are needed.

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