Abstract: - This study aims to identify the impact of increasing urbanization in the Bucharest metropolitan area

in Romania on the regional climate by analyzing spatiotemporal changes in MODIS Terra/Aqua geospatial and

in-situ time series of land surface albedo and climate parameters during the 2002- 2022 period. Additionally,

this paper quantifies the effect of urban spatiotemporal land surface albedo changes in urban thermal

environment. Our analysis combined multiple long-term satellite products (e.g., land surface temperature-LST,

normalized vegetation index/Enhanced Vegetation Index –NDVI/EVI, land surface albedo -LSA, leaf area

index-LAI, evapotranspiration-ET) with high-resolution land cover datasets in a complex statistical and spatial

regression analysis. During summer hot periods, the findings of this study reveal a strong inverse correlation

between LSA and LST (r= -0.80; p<0.01) in all city sectors associated with a high negative impact on the urban

thermal environment. As a measure of urban surface thermal properties, broadband albedo depends also on the

climate change modeling scenarios through albedo changes due to the fact that the urban physical climate

system is extremely sensitive to land surface albedo.

Received: May 19, 2023. Revised: August 2, 2023. Accepted: September 27, 2023. Published: October 12, 2023.

The increased and rapid urbanization contributes to

Land surface albedo (LSA) defined as the fraction

of radiative flux reflected by a surface to the

atmosphere, is one of the key geophysical variables

controlling the land surface radiation budget, that

indicator for mitigating the UHI phenomenon.

However, in the physical climate system, land

surface cover determines the radiation balance of

the surface and also, affects the land and air surface

in urban land surface albedo is required. Higher

ambient temperatures are evidence of the urban heat

island phenomenon, which has an adverse impact on

human health and occurs in highly populated

regions of cities. The urban heat island

phenomenon, which has a serious impact on human

health, is characterized by higher ambient

temperatures in the dense parts of the cities

compared to their surrounding environment. It is

generated by the positive thermal balance in the

high albedo materials and vegetation land cover in

mitigating urban thermal stress, but local and

regional atmospheric circulation and air quality are

essential parameters in the surface energy balance,

land surface albedo is identified as a primary

essential climate variable (ECV) is an essential tool

of climate change at local urban scale. The albedo

quantity, most relevant to the energy budget

comprises the shortwave domain (0.4 μm- 4 μm),

which includes the visible (0.4μm- 0.7μm) and near-

the processes of plant photosynthesis,

evapotranspiration, and vegetation growth, [5], [6].

Urban land cover spatiotemporal changes attributed

to natural and anthropogenic factors have a direct

impact on land surface albedo variability, [7], [8].

Both urban microclimates and outdoor thermal

environments depend not only on the regional

climate at a large scale but at a local scale and are

also linked to the features of the urban built

environment (its form and fabrics). The urban

the spatial pattern and influencing factors of the

urban thermal environment, the relationship

between the land surface albedo and the urban

thermal environment in Bucharest has not yet been

Surface Albedo, and Land Surface Temperature in

the Bucharest metropolis, in Romania. Also, urban

growth and climate change impact the thermal

environment in relationship with several

biogeophysical variables. The information provided

by this study may be useful for urban planning,

building design, and energy efficiency initiatives in

large metropolitan areas of Bucharest aimed at

mitigating the summer UHI phenomenon, especially

associated with HWs. By better knowledge and

The capital of Romania, Bucharest, is located in

both the South-East of Romania and the South-East

of Europe. Is described by a star-shaped pattern

(Fig.1), being bounded by latitudes 44.33 N and

44.66 N and longitudes 25.90 E and 26.20 E.

Fig. 1: Bucharest test site

44°25′N, longitude 26°06′E. The urban metropolitan

In this study air (AT), and land surface temperature

(LST), as well as vegetation-indicating parameters

(NDVI, LAI, vegetation land cover, etc.) and land

surface albedo (LSA) were clustered according to

biogeophysical parameters (LST, VIS, and NIR

surface albedo, NDVI) in Bucharest this study used

Spearman cross-correlation analysis and non-

parametric test coefficients as well as linear

regression analysis. For assessment of the normality

of the averaged daily time-series data sets,

Kolmogorov-Smirnov Tests of Normality. ORIGIN

10.0 software version 2021 for Microsoft Windows

was used for data processing. For satellite data,

ENVI 5.7 version, and IDL 7.0 software have been

MODIS Terra/Aqua data this study found the

following results: (1) TA plays an important role in

determining the LSA by controlling snow absence

alter the LSA of the urban/periurban vegetation land

cover growth; (4) shifts in urban land cover tend to

study are in good accordance with previous studies,

[36], [37], [38], [39], which demonstrated the

significant cooling impact of urban green (trees,

grass) albedo on cities' thermal environment

during hot summers under different climate

conditions. Cooling efficiency of vegetation is a

function of solar surface irradiance and urban

vegetation moisture content, [40]. Urban footprint

reports a strong inversely correlation between LSA

and LST in all city sectors of Bucharest associated

than for the city center. The quantification of the

urban thermal environment and associated heat

stress in the context of the urban heat island

phenomenon, which has detrimental effects on air

quality and human health, is a crucial research need

as heat waves are predicted to become more

frequent and severe in Romanian urban areas and

the South-East of Europe in the coming years due to

Additionally, the necessity to implement urban heat

mitigation technology will take into account the

following issues: reducing heat gains; enhancing

urban greenery and blue infrastructure; reducing

heat losses in the city; involving the use of advanced

materials for building the urban surfaces; the urban

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[12] Schaaf, C. MCD43A4 MODIS/Terra+Aqua

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of modified urban albedo on ambient

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[38] Chang H-S., Lin Z-H, Hsu, Y-Y. Planning for

[40] Alibakhshi S., Naimi B. Hovi A., Crowther