INTERNATIONAL JOURNAL OF COMPUTING SCIENCE AND APPLIED MATHEMATICS.
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Climate Change and Its Effect on Temperature and Precipitation Trends: Case Study in Surabaya Using RegCM5* Asyam Mulayyan Dary1 .
Mas Agus Mardyanto1OO .
Joni Hermana1 , and Chairul Imron2 AbstractAiClimate change is increasingly driving extreme weather events, yet its regional impacts remain complex.
This study employs the RegCM5 model, driven by ERA5 reanalysis data, to simulate high-resolution .
climate dynamics in Surabaya.
Indonesia from December 2018 to November 2023.
Validated against gridded observational datasets and analyzed via EarthAos energy balance, the results reveal a steady rise in both top-of-atmosphere and surface energy imbalances, corresponding with record-breaking increases in maximum and minimum temperatures by approximately 1.
5 C and 1 C from 2020 to While monthly precipitation patterns were inconsistent, daily observations indicate a significant increase in high-intensity precipitation events.
These findings offer critical insights into evolving regional climate impacts and inform local adaptation and mitigation strategies.
INTRODUCTION
LIMATE change impacts are becoming more frequent.
2022, flood .
, .
and drought .
, .
, .
happen in the same year.
These changes made them uncertain and become hard to mitigate and adapted to the problems .
, .
, .
Some studies revealed that climate change is impacting precipitation trends .
The changes are not only in precipitation, but it also alter the temperature trends.
The temperature reached a recordbreaking peak in 2023 .
, .
These changes in global scale do not necessarily mean all regions face the same thing, further regional studies are needed to determine the changes.
Surabaya is the second largest city in Indonesia, inhabited by 3 million people .
Brantas river flows through Surabaya and made Surabaya as the downstream of Brantas and a part of BrantasAo Watershed.
There was no recorded drought happening in Surabaya.
Pluvial .
, coastal .
, and fluvial .
floods happen frequently in Surabaya.
Surabaya has experienced the highest observed rainfall at 159.
3 mm/day in 2010 .
As for temperature, it has increased steadily since 1981 for minimum temperatures.
While the maximum temperature decreased steadily, making the temperature variability decreased over years since 1981.
Due to these changes, prediction tools are becoming more important to foresee the climate in the Climate model is a mathematical model to simulate the earthAos climate .
Global Climate Models (GCM.
are the Dary.
Mardyanto and J.
Hermana are with Department of Environmental Engineering.
Institut Teknologi Sepuluh Nopember 60111 OO Correspondent Author: marydanto@enviro.
Imron is with Department of Mathematics.
Institut Teknologi Sepuluh Nopember Manuscript received February 4, 2025.
accepted February 6, 2025.
general model of the entire earthAos climate .
, which are used as the basis for Regional Climate Models (RCM.
One of the most used RCMs is RegCM, which is developed by ICTP .
Compared to GCMs.
RCMs had more significant bias .
There are already several regional studies that utilize RCMs .
, .
, .
This study employs RegCM5 to simulate the regional climate of Surabaya, providing a fine-scale perspective of the regional impacts of global climate change.
Gridded datasets observation used as model assessment and calibration.
Thus, determining the climate change phenomenon and its impacts on temperatures and precipitation trends.
The findings are expected to offer valuable insights for local policymakers and stakeholders, by improving climate change mitigation and This research not only deepens the understanding of local climate dynamics but also contributes a replicable methodological framework for assessing climate change impacts in other vulnerable regions.
II.
METHODS
This study utilized RegCM5, the latest version of RegCM .
The domain is 5 km cell resolution, with 60 cells longitude by 60 cells latitude.
MOLOCH non-hydrodynamical core was used, with 18 vertical sigma levels and top of model at 30,000 km.
Simulation period started from December 2018 until November 2023.
The GCM used in this study was ERA5 6-hour datasets 25 horizontal resolution .
SST data is also from the same dataset.
ESA-CCI soil moisture .
was utilized to determine the initial soil moisture conditions.
The model was built under Windows Subsystem Linux (WSL) using Linux distribution.
Model configuration is required before running the simulation.
The scheme used in this study is shown on Table I, which is a mix from study by Wang .
and Ngo-Duc .
There are five steps to run a simulation in RegCM5, which are in order: .
terrain, .
mksurf, .
sst, .
icbc, and .
Only the last step could be run in parallel, the other can only be run in series and required to be just once per scenario.
All of required datasets can be found on ICTP database, except the finer resolution of ERA5 and ESA-CCI Soil Moisture.
There are four output datasets, which are in NetCDF format: .
ATM, .
LAK, .
RAD, and .
SRF.
In this study only radiation, temperatures, and precipitation was discussed.
Thus, the needed output are only RAD and SRF.
The output were hourly datasets, which then INTERNATIONAL JOURNAL OF COMPUTING SCIENCE AND APPLIED MATHEMATICS.
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Fig.
Surface Monthly Energy Budget Fig.
Top-of-Atmosphere Monthly Energy Budget be processed into monthly using Climate Data Operators .
and NetCDF Operators .
TABLE I
S CHEMES U SED IN T HIS S TUDY
Schemes Land Surface Planetary Boundary Layer Cumulus Convection Moisture Ocean-Flux Radiation Configuration CLM4.
Tiedtke SUBEX
Modified Zeng
RRTM
Fig.
Maximum and Minimum Temperature Trends Precipitation and temperatures bias were corrected using observed datasets from GPM IMERG NASA .
, .
and TerraClimate .
The bias-correction method used was quantile mapping, as it was the most suitable method for Indonesia .
Climate change phenomenon was determined using earthAos energy balance (EEB) equation .
, shown below.
Thus, needing TOA incident shortwave radiation .
TOA outgoing shortwave radiation .
, and TOA outgoing longwave radiation .
for Top-of-Atmosphere (TOA) EEB.
As for surface EEB the variables needed are surface downwelling shortwave radiation .
, surface upwelling shortwave radiation .
, surface downwelling longwave radiation .
, surface upwelling longwave radiation .
, sensible heat flux .
, and sensible latent heat flux .
TOA EEB = rsdt Oe .
sut rlu.
Surface EEB = .
sds Oe rsu.
lds Oe rlu.
Oe.
fss hfl.
RESULTS AND DISCUSSION
Climate Change Phenomenon One of the methods to determine climate change is by calculating the earthAos energy budget.
Shown on Figure 1, the trends of the TOA EEB have steadily increased each year.
Both peak and median trendline show positive trends, while the valley trendline was relatively stagnant.
The peak has increased around 15 W/m2 in 2023 compared to 2020.
As for the surface EEB on Figure 2, the trendlines showed a similar result.
But on the valley trendline, it has a slightly negative trend.
The peak has increased around 0.
5 W/m2 in 2023 compared to 2020.
The valley has also increased in 2023, 5 W/m2 compared to 2020.
Temperature Trends The positive trendlines in the earthAos energy budget translated into the increase in temperature trends on Figure 3.
The temperatures had reached new peaks for both maximum and minimum temperatures.
Maximum temperature has increased 5 C in 2023 compared to 2020.
The minimum temperature has also increased drastically, around 1 C in 2023 compared to 2020.
Precipitation Trends Both EEB and temperatures trend had increased dramatically, but no same thing happened for precipitation.
The trends of monthly precipitation were rather inconsistent displayed on Figure 4.
It jumped to around 650 mm/month in 2022 but dropped to around 400 mm/month in 2023.
The daily precipitation trends show a different story, on Figure 5.
The peak in 2023 was extreme, compared to the peak of every other year.
The lowest peak was in 2020 at 53.
mm/day, while the highest peak was in 2023 at 182.
9 mm/day.
Compared to the monthly trends, the daily precipitation follow similar patterns as the EEB and temperature trends.
Discussion