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Dynamic changes in urban form and function affect Carbon Dioxide Fluxes in a
Mediterranean city
Konstantinos Politakos1,*, Stavros Stagakis1,2, Christian Feigenwinter2, Matthias Roth3, Nektarios
Chrysoulakis1
Remote Sensing Lab | IACM | http://rslab.gr
JURSE 2023
18/05/2023
1Remote Sensing Lab, Institute of Applied and Computational Mathematics, Foundation for Research and Technology –Hellas (FORTH), Nikolaou
Plastira 100, Vassilika Vouton, GR 700 13, Heraklion, Crete, Greece
2Department of Environmental Sciences, University of Basel, Kingelbergstrasse 27,5046, Basel, Switzerland
3Department of Geography, National University of Singapore, Singapore, Singapore
The Remote Sensing Lab operates within the Institute of
Applied and Computational Mathematics of FORTH,
mainly focusing on climate change and urbanization, the
two global megatrends that transform human life and
directly impact each other.
The CoCO2 project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 958927.This presentation reflects the
views only of the author, and the Commission cannot be held responsible for any use which may be made of the information contained therein.
On going Projects:
Hecmas
The Remote Sensing Lab operates within the Institute of
Applied and Computational Mathematics of FORTH,
mainly focusing on climate change and urbanization, the
two global megatrends that transform human life and
directly impact each other.
The CoCO2 project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 958927.This presentation reflects the
views only of the author, and the Commission cannot be held responsible for any use which may be made of the information contained therein.
On going Projects:
Hecmas
FFP model (Kljun et al., 2015)
The Remote Sensing Lab operates within the Institute of
Applied and Computational Mathematics of FORTH,
mainly focusing on climate change and urbanization, the
two global megatrends that transform human life and
directly impact each other.
The CoCO2 project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 958927.This presentation reflects the
views only of the author, and the Commission cannot be held responsible for any use which may be made of the information contained therein.
On going Projects:
Both flux towers are equipped with IRGASON Integrated CO2/H2O Open-Path
Gas Analysers, 3D Sonic Anemometers and Net Radiometers.
HECKOR operates since autumn 2016 at the city center.
HECMAS operates since spring 2021 at a residential area in Heraklion.
FFP model (Kljun et al., 2015)
The Remote Sensing Lab operates within the Institute of
Applied and Computational Mathematics of FORTH,
mainly focusing on climate change and urbanization, the
two global megatrends that transform human life and
directly impact each other.
The CoCO2 project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 958927.This presentation reflects the
views only of the author, and the Commission cannot be held responsible for any use which may be made of the information contained therein.
On going Projects:
Heckor
Hecmas
Both flux towers are equipped with IRGASON Integrated CO2/H2O Open-Path
Gas Analysers, 3D Sonic Anemometers and Net Radiometers.
HECKOR operates since autumn 2016 at the city center.
HECMAS operates since spring 2021 at a residential area in Heraklion.
FFP model (Kljun et al., 2015)
Politakos Konstantinos | JURSE 2023 | 18 May 2023| Slide 6
Calculation
Municipality of Heraklion, measured traffic counts (Land
Cover, slide 4 ) from Monday 20 July 2020 to Wednesday
29 July 2020. The traffic counts were counted on a24-hour
basis with an automatic machine, which was placed on the
Evans intersection.
Tool and Methods
The carbon dioxide fluxes () were calculated at 30-min
time step and the time-series were:
1. Quality-controlled (Stagakis et al.2019)
2. Time-series were then temporally aggregated to
monthly and yearly emission totals.
3. Values outside of 4 standard deviations are eliminated
for every 30-minute time step.
4. Measurements during major maintenances were also
removed
•November 2018 –June 2019
•June 2021
•March 2022
Traffic Counts
Lockdown Periods were defined having a minimum threshold of 75 of the Stringency Index
(Nicolini et al.2022, Oxford COVID-19 Government Response Tracker (OxCGRT) Strigency
Index
Lockdown Periods
Politakos Konstantinos | JURSE 2023 | 18 May 2023| Slide 7
Calculation
Congestion Calculation
Input: Traffic Speed (Jun 2021 - April 2022)
Traffic Speed values were averaged at 1-hour time step and then subtracted by the day's
highest traffic speed value.
Finally, the calculation of congestion daily patterns per month were calculated for the
24hous respectively as:
Where N: number of days per month
Weekends were removed from calculation of the daily patterns.
Municipality of Heraklion, measured traffic counts (Land
Cover, slide 4 ) from Monday 20 July 2020 to Wednesday
29 July 2020. The traffic counts were counted on a24-hour
basis with an automatic machine, which was placed on the
Evans intersection.
Tool and Methods
The carbon dioxide fluxes () were calculated at 30-min
time step and the time-series were:
1. Quality-controlled (Stagakis et al.2019)
2. Time-series were then temporally aggregated to
monthly and yearly emission totals.
3. Values outside of 4 standard deviations are eliminated
for every 30-minute time step.
4. Measurements during major maintenances were also
removed
•November 2018 –June 2019
•June 2021
•March 2022
Traffic Counts
Lockdown Periods were defined having a minimum threshold of 75 of the Stringency Index
(Nicolini et al.2022, Oxford COVID-19 Government Response Tracker (OxCGRT) Strigency
Index
Lockdown Periods
Gas Analyzer
Land cover map of the Heraklion city center. The average turbulent flux source area (1 year-2017)
isopleths are displayed as white contours, surrounding the location of HECKOR.
2. Reduction of vehicular traffic during lockdown
periods resulted in a temporary reduce of
emissions. Recent study have shown that
emission reductions showed a reduction of 63%
during the lockdown period compared to previous
years. (Nicolini et al, 2022)
Site description Wind direction frequencies (%) and velocities
at HECKOR (1-year, 2017)
Average
Daytime Nighttime
Politakos Konstantinos | JURSE 2023 | 18 May 2023| Slide 8
Gas Analyzer
Land cover map of the Heraklion city center. The average turbulent flux source area (1 year-2017)
isopleths are displayed as white contours, surrounding the location of HECKOR.
Site description
The population density in the city center (defined by
the Venetian walls) is greater than the city average.
The EC tower is located near numerous major roads
that intersect the city center.
The area which concentrates the main roadways, is
characterized as the commercial zone (blue color). In
particular, it gets the most traffic during rush hours
following the commercial and working hours of the city
center.
The residential zone (green color) combines residential
neighborhoods.
Politakos Konstantinos | JURSE 2023 | 18 May 2023| Slide 9
Gas Analyzer
The EC tower (HECKOR)
The center of Heraklion is an interesting study area in
the global network of urban EC stations due to the
urban morphology, the Mediterranean climate and
the mixture between residential neighborhoods and
busy commercial zone.
Land cover map of the Heraklion city center. The average turbulent flux source area (1 year-2017)
isopleths are displayed as white contours, surrounding the location of HECKOR.
Site description
Politakos Konstantinos | JURSE 2023 | 18 May 2023| Slide 10
Gas Analyzer
Land cover map of the Heraklion city center. The average turbulent flux source area (1 year-2017)
isopleths are displayed as white contours, surrounding the location of HECKOR.
The current nearly 5-year study is focused on
determining the extent to which dynamic shifts in
urban structure and traffic regulations in the city
center effect urban eddy covariance emissions in
Heraklion’s city center.
2. Reduction of vehicular traffic during lockdown
periods resulted in a temporary reduce of
emissions. Recent study have shown that
emission reductions showed a reduction of 63%
during the lockdown period compared to previous
years. (Nicolini et al, 2022)
The first study examining the Heraklion’s case study
(Stagakis et al., 2019), showed that the majority of
emissions come from anthropogenic sources,
associated with:
I. fossil fuel combustion from vehicular traffic
activity (69%)
II. space heating/cooling (11,6%)
III. household combustion or human breathing
(19.4%).
Site description
Politakos Konstantinos | JURSE 2023 | 18 May 2023| Slide 11
Gas Analyzer
Intervention Starting Date: 05 January 2018
I. Road Closing
II. Pedestrinazations
III. Minor Planting
IV. Traffic Regulations
Land cover map of the Heraklion city center. The average turbulent flux source area (1 year-2017)
isopleths are displayed as white contours, surrounding the location of HECKOR.
Major modifications:
1. Heraklion's municipality has been implementing
extensive traffic regulation and rebuilding initiatives
since January 2018, occurred inside the flux footprint
area.
Site description
Politakos Konstantinos | JURSE 2023 | 18 May 2023| Slide 12
Daily Pattern
Daily Pattern:
•Period:01 January 2017 –5 January 2018
•Traffic and commuter patterns in Heraklion are following the commercial and working hours of the area showing two
characteristic peaks (midday & afternoon).
Politakos Konstantinos | JURSE 2023 | 18 May 2023| Slide 13
& Traffic Counts
Vs Congestion
& Congestion
Vs Traffic Counts
& Traffic Counts
& Congestion
•Identical patterns are evident in traffic counts and
measured emissions
•Congestion, also shows a good correlation with
emissions.
Politakos Konstantinos | JURSE 2023 | 18 May 2023| Slide 14
& HDD
&HDD:
•HDD stands for Heating Degree Days and is aunit of measure for recording how hot it has been over a 24-hour period (mod. NWS –
NOAA). Period:01 January 2017 –31 April 2022
•Measurements derived from residential zone
•Traffic patterns in residential roads do not change across the year. (Stagakis et al, 2019)
Politakos Konstantinos | JURSE 2023 | 18 May 2023| Slide 15
Daily Patterns
Daily Patterns:
•Before Intervention Period:01 January 2017 –04
January 2018
•After Intervention Period: 05 January 2018 –31
December 2022
•Lockdown Periods were removed.
Daily Patterns
•Daily Patterns in Commercial Zone shows the two
characteristic peaks which follow citizens’ commercial
and business behavior. In contrast, in Residential Zone
the two peaks are not easily observed and are
significantly lower.
Politakos Konstantinos | JURSE 2023 | 18 May 2023| Slide 16
Daily Patterns
Daily Patterns:
•Before Intervention Period:01 January 2017 –04
January 2018
•After Intervention Period: 05 January 2018 –31
December 2022
•Lockdown Periods were removed.
Daily Patterns
•On a weekly basis , weekdays follow the traffic and
commuter patterns, contrary to weekends. With an
exception for Saturdays’ midday, when commercial
sector is still open.
Politakos Konstantinos | JURSE 2023 | 18 May 2023| Slide 17
Monthly (Rush hours –
Commercial Zone) Monthly :
•Period:01 January 2017 –31 December 2022
•Measurements derived from commercial zone
•
(mod., Nicolini et al.2022)
•Weekends, non rush-hours, residential zone
measurements were removed
•The linear trend in monthly means shows a
gradual decrease in emissions
Politakos Konstantinos | JURSE 2023 | 18 May 2023| Slide 18
Boxplots: 25th and 75th percentiles and median
Conclusions
Identical patterns are evident in traffic counts and measured emissions, with characteristic diurnal peaks and
evening troughs. The linear correlation of the emission measurements and traffic counts shows great statistical
significance, verifying the reasoning and results of the present study (R-squared: 0.74). Similarly, for the linear
correlation of Congestion and emissions showing alike patterns (R-squared: 0.76).
The analysis of heating degree days (HDD) shows similar patterns for the winter months of each year. It turns out that
in the area south of the tower (the residential zone), the main factor that determines the carbon dioxide emissions is
the need for heating buildings.
In terms of the Daily Patterns, emissions from commercial zone follows the traffic and commuter patterns, in
contrast to the one from the residential zone. Also, lower emissions are observed after the start of the shifts in the
urban structure mainly in the northern part of the study area.
The linear trend in monthly medians shows a gradual decrease in emissions over time. The majority of months after
the intervention started show reduced emissions compared to months before.
Future plans: Developing methods to correlate in-situ flux tower measurements with satellite imageries
Politakos Konstantinos | JURSE 2023 | 18 May 2023| Slide 19
Contact info
Konstantinos Politakos
politakos@iacm.forth.gr
tel. +30 2810 391807
FORTH/IACM
http://rslab.gr