Search

The relocation of the Indonesian capital from Jakarta to Ibu Kota Nusantara (IKN) East Kalimantan IKN will affect several sectors. The change in land use from vegetated to developed land will lead to local climate changes, including the emergence of the urban heat island (UHI) phenomenon, which is reflected in a higher land surface temperature (LST) than the surrounding area. In this study, an analysis of UHI propagation was conducted on a seasonal (DJF, MAM, JJA, and SON), with 5 yearly periods from 2001 to 2020, study area in IKN and its buffer cities (Balikpapan, Samarinda, and Bontang). Terra-MODIS satellite data are processed using Google Earth Engine (GEE) platform and output is done using GrADS. UHI (high LST) is found in urban areas/buffer cities both spatially and temporally in every season, while UHI has not yet occurred in IKN (low LST) and suburban, rural, hilly areas, vegetated areas, and water bodies (lakes, rivers). The cross-sectional latitudinal and longitudinal analysis showed that the LST DJF2015-2020 from highest to lowest temperature are in Balikpapan City (36.84 OC), Samarinda City (36.13 OC), Bontang City (32.3 OC); and IKN zero point (28.82 OC). The UHI propagation was observed in 2001-2005, 2006-2010, 2011-2015, and most during 2016-2020. Seasonally, the UHI was most pronounced in the SON season, while on lowest UHI was observed in the MAM season.

This work evaluated the performance of International Telecommunication Union-Radiocommunication Sector (ITU-R) P.837-6 and P.837-7 models (Annex 1) to estimate one-minute rainfall rates in Indonesia. In addition to the default ITU-R P.837-6, the input of ITU-R P.837-6 is also modified using data which has better spatial resolution, i.e. a combination of Tropical Rainfall Measuring Mission (TRMM) 3A25 and 3B43 (ITU-R+3A25+3B43), 3B42 and 3B43 (ITU-R+3B42+3B43), Global Satellite Mapping of Precipitation (ITU-R+GSMaP), and Global Precipitation Measurement (ITU-R+GPM). Among the five test sites, the default ITU-R P.837-6 and ITU-R+3A25+3B43 could predict one-minute rainfall rates at two locations accurately. The ITU-R P.837-7 exhibited a marginally better performance for sites that had a high percentage of very heavy rain, particularly at large (1%) and small (0.001%) percentages of time exceeded. The spatial distribution of rainfall rate produced by ITU-R P.837-7 and ITU-R+3A25+3B43 was closer to the pattern demonstrated by recent satellite precipitation measurements.

This work evaluated the performance of International Telecommunication Union-Radiocommunication Sector (ITU-R) P.837-6 and P.837-7 models (Annex 1) to estimate one-minute rainfall rates in Indonesia. In addition to the default ITU-R P.837-6, the input of ITU-R P.837-6 is also modified using data which has better spatial resolution, i.e. a combination of Tropical Rainfall Measuring Mission (TRMM) 3A25 and 3B43 (ITU-R+3A25+3B43), 3B42 and 3B43 (ITU-R+3B42+3B43), Global Satellite Mapping of Precipitation (ITU-R+GSMaP), and Global Precipitation Measurement (ITU-R+GPM). Among the five test sites, the default ITU-R P.837-6 and ITU-R+3A25+3B43 could predict one-minute rainfall rates at two locations accurately. The ITU-R P.837-7 exhibited a marginally better performance for sites that had a high percentage of very heavy rain, particularly at large (1%) and small (0.001%) percentages of time exceeded. The spatial distribution of rainfall rate produced by ITU-R P.837-7 and ITU-R+3A25+3B43 was closer to the pattern demonstrated by recent satellite precipitation measurements.

Characteristics of rain attenuation for microwave-to-terahertz waveband have been investigated using raindrop size distribution (DSD) data collected by Parsivel (Particle Size Velocity) disdrometer network in Indonesia. The DSD data collected at Kototabang, Padang, Sicincin, Pontianak, Manado and Biak, were used to estimate specific rain attenuation by using T-Matrix method through Mie scattering assumption. The results of this study corroborate the regional variations of rain attenuation in Indonesia. Rain attenuation is smaller than the ITU-R model for lower frequency( 100 GHz). The largest difference between the rain attenuation obtained from measured DSD and ITU-R model is observed at Biak because the DSDs in this area contain more small-sized raindrop. This regional variation of rain attenuation should be considered in telecommunication system design especially at Q band and above.

Distribution of precipitation in Indonesia is very unique due to a complex interaction between local factors such as complex shape, geography, and orientation of the island coastlines and global scale atmospheric circulations. Raindrop size distribution (DSD) which has important implications for remote sensing and several numerical modeling applications may also vary considerably across the region. This work provides new insights into precipitation microphysics in Indonesia as inferred from principal component analysis (PCA) with 7 attributes. The PCA is used to classify raindrop size distribution data collected through a network of the Particle Size and Velocity (Parsivel) optical disdrometer along equatorial Indonesia. The Par-sivel were installed at Manado (Sulawesi) and Biak (Papua). In addition to the aforementioned sites, we have been conducting DSD observations at Padang, Sicincin, Kototabang (Sumatra) and Pontianak (Kalimantan). We divided the data into 6 DSD groups indicating six unique DSD characteristics. It was found the percentage of DSD in group V (large Do and low N w ) at Kototabang, Sicincin, Padang and Pontianak is larger than that at Manado and Biak. On the other hand, the percentage of data point in group IV (small Do and large N w ) and VI (small Do and very large Nw) at Manado and Biak is smaller than other locations.

The relationship between the radar reflectivity factor ( $Z$ ) and rainfall rate ( $R$ ), which is called the $Z-R$ relationship $(Z=AR^{b})$ , is important to convert $Z$ from weather radar to $R$ because a weather radar does not measure the rainfall amount directly. The $Z-R$ relationship can be governed from raindrop size distribution (DSD) data. However, the DSD varies not only within a specific storm type but also across different storm types and climatic regimes. Therefore, the use of a single $Z-R$ relation such as a climatological $Z-R$ relationship type $Z=200R^{1.6}$ (Marshall-Palmer) for converting radar reflectivity into $R$ will underestimate or overestimate rainfall rate. In this research, the $Z-R$ relationships for weather radar in Indonesia were governed through a network of the Particle Size and Velocity (Parsivel) optical disdrometer along equatorial Indonesia. The Parsivel were installed at Manado (Sulawesi) and Biak (Papua). In addition to the aforementioned sites, we have been conducting DSD observations at Padang, Sicincin, Kototabang (Sumatra) and Pontianak (Kalimantan). In general, the coefficients $A$ and $b$ of $Z-R$ equations vary from 200–400 and 1.36-1.47, respectively. This value shows a significant diurnal variation. In Biak and Manado, coefficient $A$ during 00–11 local time (LT) is larger than that during 12–23 LT. However, in Sicincin, Padang, Kototabang and Pontianak, coefficient $A$ during 00–11 LT much smaller than that during 12–23 LT. It was also found that coefficient $A$ in Pontianak is much larger than other sites which indicates a higher concentration of large size drop in this area as seen from a larger value of mass-weighted mean diameter $(D_{m})$ .

Communication via satellite is still one of the most important choices in telecommunication especially for areas which are not covered by optical fiber networks. However, the radio frequency used in communication satellites is affected by rain attenuation, which is called as rain attenuation. The rain attenuation increases with increasing rainfall rate and operating frequency. Therefore, accurate estimation of 1-min rainfall rate is important for modelling rain attenuation. However, in the tropics such as Indonesia, precipitation varies in several time scales. Furthermore, climate change has increased the frequency of occurrence of extreme rain and this condition may also affect the communication system. The ITU-R model which is widely used to estimate rain attenuation assumes a stationary climate. This research analysed rainfall pattern in Indonesia. In addition, the variation in melting layer height was also investigated. The rain gauge observation in some locations in Indonesia, i.e., Kototabang, Pontianak, Manado and Biak, were analyzed. The rainfall pattern was analysed using wavelet transforms. In addition, the percentage of time exceeded of several rainfall rate which are commonly used in modeling and design of telecommunication systems was also discussed. For melting layer height, 17 years of the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) data particularly TRMM PR 2A25 version 7 data were used. A 128–256 days scale band oscillation (seasonal) is observed at Kototabang, Pontianak and Biak, but it is not observed at Manado. This seasonal oscillation is an interval-independent characteristic, indicating a stationary dynamic of this signal. Intrasesonal oscillation is an interval-dependent characteristic in which the period of oscillation is not constant indicating a nonstationary dynamic of this signal. At Manado, Pontianak and Kototabang, 256–512 days scale band oscillation is also observed, but it is not clearly observed at Biak. It was also found that there is an increase of rainfall rate for small percentage of time exceeded. Furthermore, there is a slight increase of melting layer height at Kototabang, Pontianak and Biak. In Manado, linear regression shows a decrease of melting layer height with the increase of year.