Satellite Measurements Of Surface Temperature Research Articles

Urban morphology clustering analysis to identify heat-prone neighbourhoods in cities

Exposure to heat is a major health concern to urban populations. Cities aim to reduce outdoor thermal stress by adapting the built environment, but the spatial heterogeneity within cities makes it difficult to establish universal mitigation strategies. We present a methodology that identifies the hottest neighbourhoods in a city and links them to underlying patterns in urban form and function, to derive heat mitigation measures for individual neighbourhoods according to their characteristics, mitigation potential, and average surface temperature. The method applies k-means clustering and is applicable to any city using available datasets on surface cover and building morphology, as well as globally available satellite measurements of surface temperatures. Here, we present a heat-mitigation analysis for the city of Zurich. The clustering differentiates seven neighbourhood types, including two types of residential areas, modern neighbourhoods with high-rise buildings, historical districts, and industrial zones. The hottest temperatures are in neighbourhoods with extensive impervious ground cover such as railway tracks and airport parking. Surface temperatures strongly correlate with impervious surface cover and vegetation cover for all neighbourhoods, with building cover only for non-industrial built neighbourhoods, and with sky-view factor for all neighbourhoods except those with large vegetation cover. Historical, modern, and industrial neighbourhoods are particular heat-prone, and increasing vegetation for evaporative cooling is a suggested mitigation strategy for all. Modern and industrial areas could benefit from shading through increase of tree cover, while historical centres may adapt vertical greening as suitable heat mitigation strategy.

Spatial and Temporal Variability of the Characteristics of the River Plume Frontal Zone in the Kara Sea in the First Two Decades of the XXI Century

The article is devoted to obtaining long-term physical and geographical characteristics of the River Plume frontal zone as a separate hydrological structure that forms at the boundary of the fresh surface layer of the Ob and Yenisei Rivers. The primary data for identifying the frontal zone are satellite measurements of surface temperature (MODIS Aqua, Suomi NPP-VIIRS), surface salinity (NASA SMAP) and sea level (AVISO) for the period from July to October from 2002 to 2020. The position and characteristics of the River Plume frontal zone were determined using cluster analysis, which was applied for the first time to an integrated set of remote satellite sensing data in this region. The results of the study showed that in the warm period of the year, the average long-term surface temperature gradient of the River Plume frontal zone was 0.08 °C/km, the surface salinity gradient was 0.1 PSU/km, and the area was 155,000 km2. During the ice-free period of the second decade of the 21st century, the temperature gradient of the frontal zone weakens by 0.04 °C/km, and the area decreases by 100,000 km2. The correlation analysis showed that the temperature and salinity gradients, as well as the area of the River Plume frontal zone, were determined by the volumes of the river discharge of the Ob and Yenisei and ice parameters in the warm period of the year. The article presents the obtained estimates of the relationship between the characteristics of the frontal zone and the volume of river discharge, ice cover and wind parameters, as well as the value of the atmospheric indices of the Scandinavian oscillation (SCAND).

A Functional Form for the Diurnal Variation of Lake Surface Temperature on Lake Hartwell, Northwestern South Carolina

Satellite measurements of water surface temperature can benefit several environmental applications such as predictions of lake evaporation, meteorological forecasts, and predictions of lake overturning events, among others. Limitations on the temporal resolution of satellite measurements can restrict these improvements. A model of the diurnal variation in lake surface temperature could potentially increase the effective temporal resolution of satellite measurements of surface temperature, thereby enhancing the utility of these measurements in the above applications. As a step in this direction, herein a one-dimensional thermal model of a lake is used in combination with surface temperature measurements from the moderate resolution imaging spectroradiometer instrument aboard the Aqua and Terra satellites, along with ambient atmospheric conditions from local weather stations, to calculate the diurnal surface temperature variation for Lake Hartwell in South Carolina. The calculated solutions are used to obtain a functional form for the diurnal surface temperature variation of this lake, a result which has not been obtained heretofore. This functional form was obtained by averaging over several years worth of data and, therefore, represents the diurnal variation of surface temperature of the average day. Accordingly, attempts to use this averaged function to predict surface temperature in between satellite overpasses on any given day did not perform well due to day-to-day variations in cloud cover, wind speed, and other factors. It is possible that use of this averaged function combined with daily meteorological data may enable better performance.

On using mixed-layer transport parameterizations with radiometric surface temperature for computing regional scale sensible heat flux

Recent mixed-layer formulations for computing large-scale surface energy fluxes under daytime convective conditions do not require the estimation of surface-layer parameters, such as the roughness lengths for momentum and heat. This greatly simplifies approaches using operational satellite measurements of surface temperature for computing the surface energy balance at regional scales because the surface roughness parameters are not well known for many landscapes. The utility of such mixed-layer formulations is tested using data from several recent multidisciplinary field experiments (HAPEX-MOBILHY, FIFE and Monsoon 90). The results indicate that specific mixed-layer formulations adequately simulate surface sensible heat fluxes in the grassland and shrubland sites. However, use of the original values of proposed empirical coefficients for the forested site yield poor results. This is probably due to the fact that the forested site has significantly different surface geometry and associated distribution of temperature among the surface components (especially the relative importance of soil background temperatures) compared to the other sites. Therefore, the relationship between aerodynamic and radiometric surface temperature may have greatly differed between the forested site and the other locations. However, differences in aerodynamic roughness between the experimental sites were not correlated with changes required in the values of the coefficients. Instead, a two-source model which makes the distinction between aerodynamic and radiative temperature is proposed, as a means to determine which surface properties significantly affect the magnitude of the mixed-layer coefficients.

96/01094 Modelling vegetation heterogeneity effects on terrestrial water and Energy balances

A model of terrestrial water and energy balances is applied to a catchment with heterogeneous vegetation cover. The model couples the surface energy balance with the soil and surface water balance. The catchment is modelled as a nest of one-dimensional models (on a scale of ∼1 km2). The scheme allows for a known distribution of patches of different, but known, characteristics which can be integrated to give a total areal response to atmospheric boundary layer conditions. The Conjurunup catchment, in the south-west region of Western Australia, has a patchwork surface of vegetation and soil moisture conditions resulting from a combination of forestry and mining practices. Model results suggest that satellite measurements of surface temperatures can be used to estimate daily sensible heat flux from the surface in summer, but not in winter. The seasonality of this relationship is due to the soil moisture control of surface energy balance in summer. A linear relationship can be defined between the surface-air temperature difference and daily total sensible heat flux with the coefficients dependent on surface conditions, in particular leaf area index. Yearly total rainfall was also important, reflecting soil moisture levels.

An experimental study of angular effects on surface temperature for various plant canopies and bare soils

Surface temperature is a key parameter for assessing fluxes at the surface-atmosphere interface. Proper estimation of radiative surface temperature requires corrections for perturbating factors such as atmospheric contributions and angular effects. Several models have been derived to address angular effects, but relevant data for validating such models is still scarce. This paper describes a field experiment dedicated to collecting angular measurements of brightness surface temperature over several types of surfaces (bare soils with different roughnesses, corn, grass, alfalfa), using a unique measurement protocol with simultaneous temperature readings at two angles. For each surface zenithal and azimuthal angular effects are quantified. In some cases (unstressed, fully-covering alfalfa) the difference between oblique and vertical brightness temperatures is within ±0.5 K. Over stressed corn the temperature measured at angles of ±60° is about 4 K less than the nadir looking temperature, but it is 3.5 K higher over a ploughed bare soil, when the inclined radiometer faces the sunlit side of the furrows. Over a bare smooth soil the observed angular variations are shown to be compatible with those due to possible angular variations in emissivity. All the results are discussed in terms of surface geometry and microclimatic conditions, and compared to previous studies. Implications are deduced for the interpretation of satellite measurements of surface temperature.

Modelling vegetation heterogeneity effects on terrestrial water and energy balances

A model of terrestrial water and energy balances is applied to a catchment with heterogeneous vegetation cover. The model couples the surface energy balance with the soil and surface water balance. The catchment is modelled as a nest of one-dimensional models (on a scale of ∼1 km 2). The scheme allows for a known distribution of patches of different, but known, characteristics which can be integrated to give a total areal response to atmospheric boundary layer conditions. The Conjurunup catchment, in the south-west region of Western Australia, has a patchwork surface of vegetation and soil moisture conditions resulting from a combination of forestry and mining practices. Model results suggest that satellite measurements of surface temperatures can be used to estimate daily sensible heat flux from the surface in summer, but not in winter. The seasonality of this relationship is due to the soil moisture control of surface energy balance in summer. A linear relationship can be defined between the surface-air temperature difference and daily total sensible heat flux with the coefficients dependent on surface conditions, in particular leaf area index. Yearly total rainfall was also important, reflecting soil moisture levels.